понедельник, 1 октября 2018 г.

Meteor Activity Outlook for 29 September-05 October 2018

Derick Wilson captured this possible September epsilon Perseid fireball at 6:08 UT on September 7, 2018, from western Colorado USA.

Meteor activity increases in October when compared to September. A major shower (the Orionids) is active all month long and there are also many minor showers to be seen. Both branches of the Taurids become more active as the month progresses, providing slow, graceful meteors to the nighttime scene. The Orionids are the big story of the month reaching maximum activity on the 22nd. This display can be seen equally well from both hemispheres which definitely helps out observers located in the sporadic-poor southern hemisphere this time of year. Sporadic activity is still good as seen from the northern hemisphere. In the southern hemisphere though, the sporadic activity is near its annual nadir.

During this period the moon will reach its last quarter phase on Tuesday October 2nd. At this time the moon will be located 90 degrees west of the sun and will rise between 2300 and 0000 local summer time (LST) as seen from mid-northern latitudes. This weekend the waning gibbous moon will rise during the late evening hours. This will hamper meteor observations the remainder of the night as the bright moonlight will obscure all but the brightest meteors. Conditions improve with each passing night as the moon wanes and rises later. The estimated total hourly meteor rates for evening observers this week is near 4 for those viewing from the northern hemisphere and 3 for those located south of the equator. For morning observers the estimated total hourly rates should be near 13 as seen from mid-northern latitudes and 10 from the southern tropics. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Morning rates are reduce during this period due to moonlight. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brighter meteors will be visible from such locations.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning September 29/30. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

Radiant Positions at 9pm LDT

Radiant Positions at 21:00

Local Summer Time

Radiant Positions at 01:00 Local Daylight Saving Time

Radiant Positions at 01:00

Local Summer Time

Radiant Positions at 5am LDT

Radiant Positions at 5:00

Local Summer Time

These sources of meteoric activity are expected to be active this week..

We are now encountering inbound debris from comet 2P/Encke, which has a radiant superimposed upon the anthelion radiant. Since it has been shown that meteors from 2P/Encke are more numerous we will recognize this activity as the Taurids. There are two distinct radiants for the Taurids. The activity profile for the Southern Taurids is unusual in that there are several peaks and valleys throughout the activity period. The difference between the peaks and valleys is not great, but definitely noticeable in video data. These peaks occur near October 10, October 29 through November 3, and near November 15th. After this last peak activity activity slowly wanes and eventually disappears by Christmas. The Northern branch reaches maximum near November 2nd and remains in a plateau-like peak for about 10 days. After November 12th activity slowly wanes and and disappears about a week before Christmas. See the charts and table below for positions of these radiants.

The September Epsilon Perseids (SPE) are active from September 3 through October 3 with the peak occurring on the night of September 9/10. The radiant is currently located at 04:44 (071) +41. This position lies in eastern Perseus, 6 degrees southwest of the brilliant zero magnitude star known as Capella (alpha Aurigae). The radiant is best placed near 0500 LST, when it lies highest above the horizon. Rates are expected to be less than 1 no matter your location. With an entry velocity of 65 km/sec., most activity from this radiant would be swift.

The Orionids (ORI) are active from a radiant located at 04:52 (073) +17, which places it in central Taurus, 3 degrees east of the 1st magnitude orange star known as Aldebaran (alpha Tauri). This area of the sky is best placed during the last hour before dawn, when it lies highest above the horizon in a dark sky. Current rates would be near 2 per hour no matter your location. With an entry velocity of 67 km/sec., most activity from this radiant would be of swift speed.

The first members of the epsilon Geminids (EGE) are expected this week. This source is active from September 30 through October 25 with maximum activity occurring on October 11. The radiant is currently located at 05:26 (081) +28, which places it in northeastern Taurus, only 1 degree southeast of the bright 2nd magnitude star known as El Nath (beta Tauri). This area of the sky is best placed in the sky during the last hour before dawn, when it lies highest above the horizon in a dark sky. Current rates would be less than 1 per hour no matter your location. With an entry velocity of 70 km/sec., most activity from this radiant would be of swift speed.

The nu Eridanids (NUE) were co-discovered by Japanese observers using SonotoCo and Juergen Rendtel and Sirko Molau of the IMO. Activity from this long-period stream stretches from August 23 all the way to November 16. A very shallow maximum occurred near September 24. The radiant currently lies at 05:31 (083) +08, which places it in central Orion, 2 degrees northeast of the 2nd magnitude star known as Bellatrix (gamma Orionis). This area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Current rates are expected to be near 1 per hour during this period no matter your location. With an entry velocity of 67 km/sec., the average meteor from this source would be of swift velocity. Some experts feel that these meteors are early members of the Orionid shower, which peaks on October 22.

The Daytime Sextantids (DSX) are not well known due to the fact that the radiant lies close to the sun and these meteors are only visible during the last couple of hours before dawn. The radiant is currently located at 10:20 (155) -02. This position lies in central Sextans, 3 degrees southeast of the 4th magnitude star known as alpha Sextantis. This area of the sky is best placed in the sky during the last hour before dawn, when it lies highest above the horizon in a dark sky. Current rates would be most likely less than 1 per hour no matter your location. Spotting any of this activity would be a notable accomplishment. With an entry velocity of 33km/sec., most activity from this radiant would be of medium-slow speed.

The October Camelopardalids (OCT) are a recent discovery due to an outburst recorded by video cameras in 2005. Activity has occurred every year since and visual observers should be able to detect these meteors. This source is active from October 5-9 with maximum falling on the 6th. The radiant position lies near 11:08 (167) +79. This area of the sky is located in a barren area of extreme northeastern Camelopardalis. The easiest way to pinpoint the radiant is to extend a line eastward from the bottom two stars of the “bowl of the Little Dipper”. Extend another line northward from the “pointers” of the Big Dipper. Where these lines intersect is the location of the radiant. This area of the sky is above the horizon all night long but is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Rates are expected to be low except near maximum activity. Due to the location near the northern pole, these meteors are not visible from the southern hemisphere. With an entry velocity of 47 km/sec., the average meteor from this source would be of medium velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 7 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 3 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 4 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are reduced during this period due to moonlight.

The list below offers the information from above in tabular form. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.

RA (RA in Deg.) DEC Km/Sec Local Summer Time North-South
Northern Taurids (NTA) Nov 02 01:00 (015) +12 28 02:00 1 – 1 II
Southern Taurids (STA) Oct 10 01:17 (019) +05 27 02:00 2 – 2 II
September Epsilon Perseids (SPE) Sep 10 04:44 (071) +41 65 05:00 <1 – <1 II
Orionids (ORI) Oct 22 04:52 (073) +17 67 05:00 2 – 2 I
epsilon Geminids (EGE) Oct 11 05:26 (081) +28 70 06:00 <1 – <1 II
nu Eridanids (NUE) Sep 24 05:31 (083) +08 67 06:00 1 – 1 IV
Daytime Sextantids (DSX) Sep 29 10:20 (155) -02 33 11:00 <1 – <1 IV
October Camelopardalids (OCT) Oct 06 11:08 (167) +79 47 12:00 <1 – <1 IV

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Bright fireball over Reunion/Mauritius islands on September 25

A very bright fireball was observed and filmed over Reunion island on September 25, 14h 10min UT. It was recorded by NASA/CNEOS government sensors, and was actually the third more energetic meteoric event of 2018.

Image of the September 25, 2018, 14h 10m UT fireball extracted from a video of the event.
Image of the September 25, 2018, 14h 10m UT fireball extracted from a Youtube video of the event.

A few witnesses from Reunion and Mauritius islands reported a very bright fireball on September 25, 2018, 14h 10min UT. A video of the event was also recorded from the Reunion, showing a very bright meteor lasting more than 5 seconds, and enlighting the clouds and the sky.

According to the NASA (National American Space Agency) CNEOS (Center for Near Earth Objects Studies) departement, the meteor was detected by governement sensors, and the calculated impact energy was close to 1.9 kT, which is the third more energetical meteor event since the beginning of the year. It occured South of the two islands, over the Indian Ocean, leaving no chances of finding associated meteorites. Previous energetic events were recorded over Russia on June 21, and Greenland on July 25.

Fireballs reported by US Government sensors, from 1988, April 15 until 2018 September 2018. Credit: NASA/CNEOS
Fireballs reported by US Government sensors, from 1988, April 15 until 2018 September 2018. Credit: NASA/CNEOS, Alan B. Chamberlin (JPL/Caltech)

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Opalized Wood (Miocene) | #Geology #GeologyPage…

Opalized Wood (Miocene) | #Geology #GeologyPage #Fossil

Locality: Virgin Valley, Humbolt County, Nevada

Photo Copyright © 1mcmurdo/ebay.com

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Vermilion Cliffs National Monument | #Geology #GeologyPage…

Vermilion Cliffs National Monument | #Geology #GeologyPage #Arizona #UnitedStates

Vermilion Cliffs National Monument is located in Arizona, immediately south of the Utah state line. This National Monument, 293,689 acres (118,852 ha) in area, protects the Paria Plateau, Vermilion Cliffs, Coyote Buttes, and Paria Canyon. Elevations in the Monument range from 3,100 feet to 6,500 feet above sea level (944 to 1,981 meters).

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Fluorite | #Geology #GeologyPage #Mineral Locality: Yaogangxian…

Fluorite | #Geology #GeologyPage #Mineral

Locality: Yaogangxian Mine, Yizhang Co., Chenzhou Prefecture, Hunan Province, China

Size: 8 x 7 x 6.5 cm

Photo Copyright © Anton Watzl Minerals

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Watermelon Valley, Egypt | #Geology #GeologyPage #Egypt How it…

Watermelon Valley, Egypt | #Geology #GeologyPage #Egypt

How it formed?, More Info & Photos: http://www.geologypage.com/2017/04/watermelon-valley-egypt.html

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Tourmaline | #Geology #GeologyPage #Mineral Locality: Mogok,…

Tourmaline | #Geology #GeologyPage #Mineral

Locality: Mogok, Pyin-Oo-Lwin District, Mandalay Division, Myanmar

Size: 4 x 2 x 2 cm

Photo Copyright © Anton Watzl Minerals

Geology Page



The formation of (very) slowly rotating stars

The famous star forming filament B211 in the Taurus molecular cloud, as observed with the Herschel satellite. Above and below the filament threads called ‘striations’ are faintly visible, they trace out the magnetic field of the cloud. Radio telescopes show that gas flows towards the filament along these striations, guided by the magnetic field. In the dense gas accumulating in the filament itself stars are forming, a few are already visible as bright dots. Credit: ESA/Herschel

Some stars are observed to rotate with extremely long periods, the ‘slow rotation problem’. A theory developed at MPA now shows how the magnetic field of a star’s ‘birth cloud’ can cause some stars to accumulate mass without acquiring significant rotation.

Some stars rotate much faster than the Sun. The star CU Virginis, a single star in the constellation Virgo for example, has a rotation period of only half a day. At the other extreme are stars like Gamma Equulei (the nose of the little horse), which rotates with a period of at least 70 years. That’s more than 50 000 times slower. Both stars are members of a special class, the so-called ’magnetic Ap stars’. (Both are just visible with the naked eye.) The rotation period of Ap stars can be measured from changes of the observed strength of the magnetic field on its surface, as the field configuration rotates into and out of view.

But also ‘normal’ stars more like the Sun show something related: already at a very young age they rotate with periods ranging all the way from a half a day to some 100 days. The rapidly rotating ones are easily explained: small random motions in a star forming cloud are amplified by ‘angular momentum conservation’, in parts of the cloud that contract to form protostars. If this were the only effect, however, it would produce only very rapidly rotating stars.

Schematic showing the expected shape of the magnetic field lines around a protostar in objects like the B211 filament of Fig. 1. The field lines, still connected at large distances to the star forming cloud, have a kink at the midplane. This distortion is due to the weight of the gas (green) under the force of gravity of the protostar (yellow). The kinks are subject to diffusion of gas across the field lines, allowing the gas to accrete onto the protostar (arrows). © MPA

But the contracting gas also has a magnetic field, which gets amplified by the same contraction. At some stage(s) of the star formation process (in particular inside the Herschel filament of Fig.1), this field will be ‘bent’ (see the sketch in Fig. 2). This magnetically dominated form of accretion is sometimes called a pseudodisk, as it differs from the standard view of stars building up their mass through an accretion disk without a strong magnetic field. This view assumes that the magnetic field has largely left the gas already at an early stage. In such a disk the host star’s gravitational attraction is balanced by orbital rotation of the gas (like planets orbiting their host star).

In a pseudodisk, however, the magnetic tension force between the contracting core and the birth cloud to which it is still connected tries to maintain the very slow rotation of the cloud. The balance between angular momentum conservation and magnetic tension now determines whether the star formed will be a slowly or a rapidly rotating one. Observations appear to show that the balance can tip either way. The work reported here explains how this balance works, and how it can lead even to extremely long rotation periods.

Orbital frequency of the gas drifting towards the protostar, in units of the frequency of a local Kepler orbit, as a function of distance r from its centre. Starting at the right boundary (r=1), with a frequency just below that of a Kepler orbit, the calculations show how the rotation of the gas changes as it approaches the protostar (at r=0). With only small differences in the initial rotation, there are two possible outcomes: either the tendency to conserve angular momentum wins and the gas ends up on a Kepler orbit (upper curve), or magnetic torques win and the gas loses its rotation (lower two curves). © MPA

Minor differences in the random velocities in the initial state of the star forming gas cloud can lead to opposite outcomes: either very fast or very slowly rotating stars (see Fig. 3). The very slowly rotating ones have accreted mass without accreting angular momentum. Key to the explanation of this result is the observation that it does not take much of a magnetic connection to extract the angular momentum of already slowly rotating gas. The slower the gas rotates, the more effective is the connection to the birth cloud in slowing it to even longer periods. Once this sequence of events is on its way, the gas will end up rotating on typical time scales just like the birth cloud, well before it ends up on the protostar. Its remaining path to the protostar is then determined by gravitational attraction, the opposing magnetic tension, and diffusion of gas across the field lines. A magnetic connection extending to a distance like the orbit of Pluto, for example, would be sufficient to explain final rotation periods of centuries. The calculations show that this unexpected outcome depends critically on the initial rotation of the gas: it has to be a bit slower than a Kepler orbit.

Observations of protostars indicate that they probably form episodically, in bursts rather than as a continuous process. This may also explain the range of intermediate rotation periods observed in young star clusters, if the balance tips randomly a few times between bursts of accretion with opposite outcomes. This speculation can probably be tested with the large new data sets becoming available from observatories like the Kepler satellite or ALMA.


Spruit, Hendrik C.
Scientist emeritus
Phone: 2220
Email: hspruit@mpa-garching.mpg.de
Room: 246

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Greeks in a Longobard cemetery

I designed a new Principal Component Analysis (PCA) to help me analyze the fine scale genetic affinities of post-Bronze Age ancient samples from Southern Europe and surrounds. Below is a version of this PCA with a selection of the most Southern European-related ancients from this year’s Amorim et al. and Veeramah et al. papers (for background reading, see the posts and comments here and here). The relevant datasheet is available here.

A number of people in the comments at this blog and elsewhere were especially curious about the potential genetic origins of the three most Near Eastern-shifted individuals from the Amorim et al. dataset: CL25, CL30 and CL38. Judging from my new PCA, it seems likely to me that this trio came from the pre-Slavic invasions Aegean region. In other words, I’d say they’re probably Roman era Greeks or their descendants, who, unlike most present-day Greeks, don’t harbor any Slavic ancestry. That’s because they cluster very strongly with present-day Greeks from Crete, and also more or less sit on a cline running from present-day mainland Greeks to Cypriots.
See also…
Celtic vs Germanic Europe

2018 October 1 The First Rocket Launch from Cape Canaveral…

2018 October 1

The First Rocket Launch from Cape Canaveral
Credit: NASA

Explanation: A new chapter in space flight began in 1950 with the launch of the first rocket from Cape Canaveral, Florida: the Bumper V-2. Featured here, the Bumper V-2 was an ambitious two-stage rocket program that topped a V-2 missile base with a WAC Corporal rocket. The upper stage was able to reach then-record altitudes of almost 400 kilometers, higher than even International Space Station. Launched under the direction of the General Electric Company, the Bumper V-2 was used primarily for testing rocket systems and for research on the upper atmosphere. Bumper V-2 rockets carried small payloads that allowed them to measure attributes including air temperature and cosmic ray impacts. Seven years later, the Soviet Union launched Sputnik I and Sputnik II, the first satellites into Earth orbit. In response in 1958, 60 years ago today, the USA created NASA.

∞ Source: apod.nasa.gov/apod/ap181001.html

Pitcher plant samples from opposite sides of the globe are surprisingly similar

The natural world is full of examples of what biologists call convergent evolution—instances where unrelated creatures developed similar traits in response to similar evolutionary pressures.

Pitcher plant samples from opposite sides of the globe are surprisingly similar
Credit: Leonora Bittleston

But can that convergence include the interactions of different species that evolve under similar conditions? The early evidence, says Leonora Bittleston, suggests the answer is yes.

As part of a study conducted while she was a graduate student in the labs of Naomi Pierce, the Sidney A. and John H. Hessel Professor of Biology, and Anne Pringle, the Vilas Distinguished Professor of Botany at the University of Wisconsin, Madison, Bittleston found that the “miniature ecosystems” housed in pitcher plants from opposite sides of the world are strikingly similar, suggesting that there may be something about the plants themselves that drives the formation of those communities. The study is published in eLife.

“These plants, the Nepenthes in Southeast Asia and Sarracenia in North America, evolved completely independently … and because they’re like little aquatic islands, they can be used as model systems to study community ecology,” said Bittleston, now a postdoctoral fellow at the Massachusetts Institute of Technology. “They have a whole little microcosm inside them—even though they eat insects, there are aquatic insects that can only survive in pitcher plants, but there are also aquatic mites, protozoa, rotifers, fungal yeasts, and bacteria.”

To capture an image of that community, Bittleston, Pierce, Pringle, and their collaborators from the Universiti Malaysia Sabah and the University of Malaya turned to a process called DNA barcoding, which uses a short section of DNA to identify different species.

“One way I think this is novel is it’s the first time we’re looking at the whole community inside a host, and not just one taxon group,” Bittleston said. “We wanted to capture the entire community that lives in these plants.”

Pitcher plant samples from opposite sides of the globe are surprisingly similar
A Nepenthes veitchii [Credit: Leonora Bittleston]

When the team compared more than 300 samples of those communities, collected from pitcher plants in Borneo, Singapore, the Harvard Forest, and along the Gulf Coast, they found surprising similarities.

“They were very similar in terms of how many different species you find,” Bittleston said. “But they’re also very similar in terms of the phylogenetic groups. Even though you don’t see the exact same things living in the Southeast Asian and North American plants, the creatures that we do find there tend to be related to each other.”

When they narrowed their focus and examined different species of pitcher plants from the same genus that grew near one another, the group found some evidence that the species of plant might influence which species were present, but Bittleston said other factors—like the acidity of the liquid—might also be involved.

“We were able to extrapolate a bit and say that we think these organisms are colonizing pitchers on different sides of the world because the pitchers have similar shapes—they have this convergent form and they have this convergent function of trapping and digesting insects,” she said. “And they also probably have some similarities in terms of the chemical conditions inside the pitchers.”

In a follow-up experiment, Bittleston transported a number of Southeast Asian pitcher plants into the Harvard Forest alongside native species and glass tubes, some of which were empty and some of which had insect material in them—and the results were startling.

Pitcher plant samples from opposite sides of the globe are surprisingly similar
A frog sits inside a Sarracenia flava [Credit: Leonora Bittleston]

“Basically, we found that the Southeast Asian plants, when they opened and were colonized by communities in North America, they were very similar to the local communities,” she said. “The local community recognized it as a host.”

Arguably the most striking example of how the local community accepted the Southeast Asian plants, she said, came in the form of the pitcher plant mosquito, Wyeomyia smithii, which is only found in North American species.

“But we found larvae growing in these pitchers—and we even found pupae, which meant they were able to complete their life cycle,” Bittleston said. “There weren’t as many of them, but they still recognized them as hosts. It was really interesting that when you bring something these mosquitoes have never seen before, and they recognized it as a place where they can live.”

The finding supports a theory, outlined by Bittleston in a 2016 paper, that suggested that, just as convergent evolution might produce similar traits in unrelated species, “convergent interactions” might lead to similar relationships between species.

As an example, Bittleston pointed to ant plants, which, though unrelated, evolved similar structures that provide nesting site for ants. The ants in turn protect the plants from herbivores.

Pitcher plant samples from opposite sides of the globe are surprisingly similar
The bacterial communities in pitchers on opposite sides of the world are more similar to each other than they are
to the bacterial communities from the environment directly surrounding the plants. In the rectangular diagrams,
each column is a sample and the colors represent different families of bacteria in that sample
[Credit: Leonora Bittleston]

“Convergent evolution has always compared individuals, but I think there is something fundamentally different about an interaction evolving,” she said. “It can tell us about how natural selection might be acting on those species interactions. The way we think of it is that there may be certain interactions that represent fitness peaks.”

Using genetic tools, Bittleston, Pierce, and Pringle also examined the functional genes in the pitcher plant community, and found several that are related to breaking down amino acids and proteins, potentially making nitrogen available to the plants. Other genes, Bittleston said, were related to the production of chitinases, enzymes capable of breaking down the chitin found in insect exoskeletons.

Going forward, Bittleston said, her work at MIT is focused on bringing the pitcher plant ecosystem into the lab to gain a deeper understanding of how the different bacteria found in the liquid interact with each other.

“Part of what I want to understand is the complexity in ecosystems,” she said. “We still don’t really know why communities form and how different species interact within communities, so some of the experiments I’m doing now are trying to get at those questions more in depth.”

Ultimately, Bittleston said, the study offers important insight into how ecosystems form and how evolution can act on a community of organisms to bring different species together in certain ways.

“What I think we need right now is better ways of understanding ecosystems, because we’re in this changing world, and we’re trying to figure out how to manage them, or at least not destroy them,” she said. “So to get a better idea of how ecosystems form, and what sort of factors might control who’s there and how they’re interacting, that’s useful.”

Author: Peter Reuell | Source:  Harvard University [September 26, 2018]



Simulations uncover why some supernova explosions produce so much manganese and nickel

Researchers have found white dwarf stars with masses close to the maximum stable mass (called the Chandrasekhar mass) are likely to produce large amounts of manganese, iron, and nickel after it orbits another star and explodes as Type Ia supernovae.

Simulations uncover why some supernova explosions produce so much manganese and nickel
An artist’s conception of a single-degenerate Type Ia supernova scenario. Due to the stronger gravitational force from the
white dwarf on the left, the outer material of the bigger, slightly evolving main-sequence star on the right is torn away
and it flows onto the white dwarf, eventually increasing the mass of the white dwarf toward the Chandrasekhar mass.
This carbon-oxygen white dwarf will later explode as a Type Ia supernova [Credit: Kavli IPMU]

A Type Ia supernova is a thermonuclear explosion of a carbon-oxygen white dwarf star with a companion star orbiting one another, also known as a binary system. In the Universe, Type Ia supernovae are the main production sites for iron-peak elements, including manganese, iron, and nickel, and some intermediate mass elements including silicon and sulfur.
However, researchers today cannot agree on what kind of binary systems triggers a white dwarf to explode. Moreover, recent extensive observations have revealed a large diversity of nucleosynthesis products, the creation of new atomic nuclei from the existing nuclei in the star by nuclear fusion, of Type Ia supernovae and their remnants, in particular, the amount of manganese, stable nickel, and radioactive isotopes of 56-nickel and 57-nickel.

To uncover the origin of such diversities, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher Shing-Chi Leung and Senior Scientist Ken’ichi Nomoto carried out simulations using the most accurate scheme to date for multi-dimensional hydrodynamics of Type Ia supernova models. They examined how chemical abundance patterns and the creation of new atomic nuclei from existing nucleons depend on white dwarf properties and their progenitors.

Simulations uncover why some supernova explosions produce so much manganese and nickel
The colour plot of the temperature distribution of the benchmark Type Ia supernova model at about 1 second
after explosion. The deflagration model with deflagration-detonation transition is used
to produce this result [Credit: Leung et al.]

“The most important and unique part of this study is that this is so far the largest parameter survey in the parameter space for the Type Ia supernova yield using the Chandrasekhar mass white dwarf,” said Leung.
A particularly interesting case was the supernova remnant 3C 397. 3C 397 is located in the Galaxy about 5.5 kpc from the center on the galactic disk. Its abundance ratios of stable manganese/iron and nickel/iron were found to be two and four times that of the Sun respectively. Leung and Nomoto found the abundance ratios among manganese, iron and nickel are sensitive to white dwarf mass and metallicity (how abundant it is in elements heavier than hydrogen and helium). The measured values of 3C 397 can be explained if the white dwarf has a mass as high as the Chandrasekhar mass and high metallicity.

The results suggest remnant 3C 397 could not be the result of an explosion of a white dwarf with relatively low mass (a sub-Chandrasekhar mass). Moreover, the white dwarf should have a metallicity higher than the Sun’s metallicity, in contrast to the neighboring stars which have a typically lower metallicity.

Simulations uncover why some supernova explosions produce so much manganese and nickel
X-ray, optical & infrared composite image of 3C 397 [Credit: X-ray: NASA/CXC/Univ of Manitoba/S.Safi-Harb et al,
Optical: DSS, Infrared: NASA/JPL-Caltech]

It provides important clues to the controversial discussion of whether the mass of the white dwarf is close to the Chandrasekhar mass, or sub-Chandrasekhar mass, when it explodes as a Type Ia supernova.
The results will be useful in future studies of chemical evolution of galaxies for a wide range of metallicities, and encourage researchers to include super-solar metallicity models as a complete set of stellar models.

Leung says the next step of this study would involve further testing their model with more observational data, and to extend it to another subclass of Type Ia supernovae.

These results were published in The Astrophysical Journal.

Source: Kavli Institute for the Physics and Mathematics of the Universe [September 26, 2018]



Cosmic ‘dustpedias’ could reveal new types of galaxy

Measuring the vast quantities of cosmic dust in interstellar space may be a key to unlocking various mysteries of the cosmos, including how the grains form and whether new types of galaxy are obscured by the particle clouds.

Cosmic 'dustpedias' could reveal new types of galaxy
Cosmic dust is too cold to be captured by optical telescopes, so visual images of galaxies
don’t give the full story of conditions [Credit: The Hubble Heritage team]

Cosmic dust grains, which are born in stars, are the building blocks for other stars and rocky planets such as Earth – as well as maybe life itself. However, our understanding of the dusty universe and the processes that form it remains limited.

‘We lack vital knowledge about the origin of cosmic dust, its evolution, and therefore the fuel for star formation of galaxies over recent cosmic history,’ said Professor Haley Gomez, an astrophysicist at Cardiff University in the UK.

The cosmic haze also means that key astronomical processes evade detection by traditional telescopes. ‘Our view of the universe has been biased,’ said Prof. Gomez, who is undertaking a project called CosmicDust. ‘We’ve been looking at the visible light from stars and galaxies. But half of all the light shone by stars since the Big Bang has in fact been hidden.’

The problem is, cosmic dust is too cold to be detected by optical telescopes. In the past decade, however, dust exploration has been aided by major space missions, such as the Planck and Herschel missions launched in 2009. These have involved telescopes that can capture galaxies in the far-infrared part of the spectrum – where the dust particles become visible.

Both missions finished in 2013, leaving behind a wealth of raw data to delve into. This is being harnessed by DustPedia, one of a couple of Cardiff University projects seeking to better understand the properties of space dust.

Data bank

DustPedia is combining the Herschel and Planck data with that from ground-based and space-based telescopes – and from other parts of the spectrum, such as the visible and ultraviolet – to create a huge archive for studying dust and its interactions in galaxies in the part of the universe nearest to us. It currently provides imagery for nearly 900 galaxies.

‘One of the prime motivations in doing this is to understand how galaxies are evolving and changing with time,’ said Professor Jonathan Davies, principal investigator of DustPedia. He explained that, for instance, a large portion of chemical elements synthesised by stars reside in cosmic dust. Understanding how much of each of these is present helps reveal how chemically evolved a galaxy is, and ultimately how far it has proceeded along its life path.

This can also help us compare how different types of galaxies are evolving – for instance, the differences between giant elliptical galaxies and smaller flattened ones.

Prof. Davies describes cosmic dust as being like cigarette smoke blown in front of a light bulb, obscuring much of the light from stars.
‘You might be misled into thinking that if a galaxy is not producing much light, there can’t be many stars there. If you can measure the quantity of dust, you can start making corrections,’ he said.

Prof. Gomez’s CosmicDust project is seeking to build an extensive catalogue of dusty galaxies to create a ‘census of dust’ aided by the insights from Herschel. She expects this will help uncover mysterious new classes of galaxies that appear dust-poor in visible light pictures, but actually contain huge quantities of dust.

The project has already finished its first statistical dust census of 15,000 galaxies, finding that some contain far more dust and some far less than predicted – and has released catalogues and maps covering almost half a million galaxies.

Among other things, the team has found three new exploding stellar remnants containing lots of dust. Interestingly, said Prof. Gomez, these all contain rapidly rotating neutron stars resulting from massive star explosions, hinting that these may be important dust-producing systems.

Furthermore, by using the Herschel data to peer back 12 billion years to the early universe, her team found initial indications that the universe may have been much dustier in the past than today and thus characterised by faster star formation.

Prof. Gomez says possible explanations for today’s missing dust include galactic winds blowing large volumes out of galaxies or destruction by shockwaves of hot gas.

‘These are exactly the kinds of things we should be able to test once the large surveys have been analysed and our catalogues and measurements are finished,’ she said.

The researchers are also aiming to resolve a long-standing controversy over the origin of cosmic dust, said Prof. Gomez – ‘whether it is made by sun-like stars in their quiet death throes, or if it is much more violent, instead originating from massive stars that tear themselves apart at the end of their lives.’ Scientific research is currently leaning towards the latter explanation, she added.

Lab dust

Another initiative, NANOCOSMOS, is modelling cosmic dust in the laboratory to build a better picture of how it forms and behaves.
Several experimental set-ups have been built to do this, such as the stardust chamber, which simulates the formation of dust grains.

Researchers at the Institute of Fundamental Physics (IFF) in Madrid, Spain are currently using this vacuum chamber to investigate the reaction of individual elements found in dust, looking initially at carbon clusters and their interaction with hydrogen. They will later investigate interactions and dust properties involving silicon, iron and other metals, and their interaction with gases, to simulate more realistic astrophysical environments.

‘Studying how dust particles form and how they interact with the gas are essential to understand their properties,’ said Professor José Cernicharo, a physicist working in the field of molecular astrophysics at the IFF and corresponding principal investigator for the NANOCOSMOS project. ‘Deriving the structure of the first nanoparticles formed from different elements is a mandatory step to model correctly the physics and chemistry of the ejecta of red giants and supernovas.’

Understanding more about nanoparticle formation does not just help uncover what is happening in space and track the universe’s history. Models showing how dust forms and grows can also aid innovation on our own planet in areas such as nanotechnology – important in fields such as green energy and biotechnology.

As for the cosmos, investigating dust will ultimately help us form a fuller picture of the universe around us.

‘Dust plays a key role in the physical and chemical evolution of astronomical objects, but cannot be properly considered in models because of our limited knowledge on its nature and properties,’ said Prof. Cernicharo. ‘Any progress on this question will therefore have a strong impact in astrophysics and astrochemistry.’

Author: Gareth Willmer | Source: Horizon: The EU Research & Innovation Magazine [September 27, 2018]



Where are they? Cosmologists search Andromeda for signs of alien life

“Are we alone in the universe?” The question has fascinated, tantalized and even disconcerted humans for as long as we can remember.

Where are they? Cosmologists search Andromeda for signs of alien life
The Andromeda Galaxy [Credit: Scot Rosen]

So far, it would seem that intelligent extraterrestrial life — at least as fits our narrow definition of it — is nowhere to be found. Theories and assumptions abound as to why we have neither made contact with nor seen evidence of advanced extraterrestrial civilizations despite decades-long efforts to make our presence known and to communicate with them.

Meanwhile, a steady stream of discoveries are demonstrating the presence of Earth analogues — planets that, like our own, exist at a “Goldilocks zone” distance from their own respective stars, in which conditions are “just right” for liquid water (and thus life) to exist. Perhaps even more mind-blowing is the idea that there are, on average, as many planets as there are stars.

“That is, I think, one of the amazing discoveries of the last century or so — that planets are common,” said Philip Lubin, an experimental cosmologist and professor of physics at UC Santa Barbara. Given that, and the assumption that planets provide the conditions for life, the question for Lubin’s group has become: Are we looking hard enough for these extraterrestrials?

That is the driver behind the Trillion Planet Survey, a project of Lubin’s student researchers. The ambitious experiment, run almost entirely by students, uses a suite of telescopes near and far aimed at the nearby galaxy of Andromeda as well as other galaxies including our own, a “pipeline” of software to process images and a little bit of game theory.

“First and foremost, we are assuming there is a civilization out there of similar or higher class than ours trying to broadcast their presence using an optical beam, perhaps of the ‘directed energy’ arrayed-type currently being developed here on Earth,” said lead researcher Andrew Stewart, who is a student at Emory University and a member of Lubin’s group. “Second, we assume the transmission wavelength of this beam to be one that we can detect. Lastly, we assume that this beacon has been left on long enough for the light to be detected by us. If these requirements are met and the extraterrestrial intelligence’s beam power and diameter are consistent with an Earth-type civilization class, our system will detect this signal.”

From Radio Waves to Light Waves

For the last half-century, the dominant broadcast from Earth has taken the form of radio, TV and radar signals, and seekers of alien life, such as the scientists at the Search for Extraterrestrial Intelligence (SETI) Institute, have been using powerful radio telescopes to look for those signals from other civilizations. Recently however, and thanks to the exponentially accelerating progress of photonic technology, optical and infrared wavelengths are offering opportunities to search via optical signals that allow for vastly longer range detection for comparable systems.

In a paper published in 2016 called The Search for Directed Intelligence or SDI, Lubin outlined the fundamental detection and game theory of a “blind-blind” system where neither we, nor the extraterrestrial civilization are aware of each other but wish to find each other. That paper was based on the application of photonics developed at UC Santa Barbara in Lubin’s group for the propulsion of small spacecraft through space at relativistic speeds (i.e. a significant fraction of the speed of light) to enable the first interstellar missions. That ongoing project is funded by NASA’s Starlight and billionaire Yuri Milner’s Breakthrough Starshot programs, both of which use the technology developed at UCSB. The 2016 paper shows that the technology we are developing today would be the brightest light in the universe and thus capable of being seen across the entire universe.

Of course, not everyone is comfortable with advertising our presence to other, potentially advanced, extraterrestrial civilizations.

“Broadcasting our presence to the universe, believe it or not, turns out to be a very controversial topic,” Stewart said, citing bureaucratic issues that arise whenever beaconing is discussed, as well as the difficulty in obtaining the necessary technology of the scale required. Consequently, only a few, tentative signals have ever been sent in a directed fashion, including the famous Voyager 1 probe with its message-in-a-bottle-like golden record.

Tipping the concept on its head, the researchers asked, ‘What if there are other civilizations out there that are less shy about broadcasting their presence?’

“At the moment, we’re assuming that they’re not using gravity waves or neutrinos or something that’s very difficult for us to detect,” Lubin said. But optical signals could be detected by small (meter class) diameter telescopes such as those at the Las Cumbres Observatory‘s robotically controlled global network.

“In no way are we suggesting that radio SETI should be abandoned in favor of optical SETI,” Stewart added. “We just think the optical bands should be explored as well.”

Searching the Stars

“We’re in the process of surveying (Andromeda) right now and getting what’s called ‘the pipeline’ up and running,” said researcher Alex Polanski, a UC Santa Barbara undergraduate in Lubin’s group. A set of photos taken by the telescopes, each of which takes a 1/30th slice of Andromeda, will be knit together to create a single image, he explained. That one photograph will then be compared to a more pristine image in which there are no known transient signals — interfering signals from, say, satellites or spacecraft — in addition to the optical signals emanating from the stellar systems themselves. The survey photo would be expected to have the same signal values as the pristine “control” photo, leading to a difference of zero. But a difference greater than zero could indicate a transient signal source, Polanski explained. Those transient signals would then be further processed in the software pipeline developed by Stewart to kick out false positives. In the future the team plans to use simultaneous multiple color imaging to will help remove false positives as well.

“One of the things the software checks for is, say, a satellite that did go through our image,” said Kyle Friedman, a senior from Granada Hills High School in Los Angeles, who is conducting research in Lubin’s group. “It wouldn’t be small; it would be pretty big, and if that were to happen the software would immediately recognize it and throw out that image before we actually even process it.”

Other vagaries, according to the researchers, include sky conditions, which is why it’s important to have several telescopes monitoring Andromeda during their data run.

Thanks to the efforts of Santa Barbara-based computer engineer Kelley Winters and the guidance of Lubin group project scientist Jatila van der Veen, the data is in good hands. Winters’ cloud-based Linux server provides a flexible, highly connected platform for the data pipeline software to perform its image analysis, while van der Veen will apply her digital image processing expertise to bring this project to future experimental cosmologists.

For Laguna Blanca School senior and future physicist Caitlin Gainey, who joins the UCSB physics freshman class this year, the project is a unique opportunity.

“In the Trillion Planet Survey especially, we experience something very inspiring: We have the opportunity to look out of our earthly bubble at entire galaxies, which could potentially have other beings looking right back at us,” she said. “The mere possibility of extraterrestrial intelligence is something very new and incredibly intriguing, so I’m excited to really delve into the search this coming year.”

The search, for any SETI-watcher, is an exercise in patience and optimism. Andromeda is 2.5 million light-years away, van der Veen pointed out, so any signal detected now would have been sent at least 2.5 million years ago — more than long enough for the civilization that sent it to have died out by the time the light reaches us.

“That does not mean we should not look,” van der Veen said. “After all, we look for archaeological relics and fossils, which tell us about the history of Earth. Finding ancient signals will definitely give us information about the history of evolution of life in the cosmos, and that would be amazing.”

While the data run and processing time for this particular project could occur in a span of weeks, according to the researchers this sequence could be repeated indefinitely. Theoretically, like all the sunrise and sunset watchers, and stargazers before us, we could look at the sky forever.

“I think if you were to take someone outside and you were to point at some random star in the night sky and see that is where life is, I think you would be hard pressed to find anyone who would not look at that star and just feel something very deep within themselves,” Polanski said. “Some very deep connection to whatever is up there or some kind of solace, I think, knowing that we’re not alone.”

The latest UCSB data and game theory of the “blind-blind” detection strategy used is being presented at the NASA Technosignatures workshop in Houston on September 28.

Author: Sonia Fernandez | Source: University of California – Santa Barbara [September 27, 2018]



PCB pollution threatens to wipe out killer whales

More than forty years after the first initiatives were taken to ban the use of PCBs, the chemical pollutants remain a deadly threat to animals at the top of the food chain. A new study, just published in the journal Science, shows that the current concentrations of PCBs can lead to the disappearance of half of the world’s populations of killer whales from the most heavily contaminated areas within a period of just 30-50 years.

PCB pollution threatens to wipe out killer whales
In some areas, killer whales feed primarily on sea mammals and big fish like tuna and sharks and are then threatened
by PCBs. In areas where the killer whales primarily feed on small fish like herring, they are less threatened
[Credit: Audun Rikardsen]

Killer whales (Orcinus orca) form the last link in a long food chain and are among the mammals with the highest level of PCBs (polychlorinated biphenyls) in their tissue. Researchers have measured values as high as 1300 milligrams per kilo in the fatty tissue (blubber) of killer whales. For comparison, a large number of studies show that animals with PCB levels as low as 50 milligrams per kilo of tissue may show signs of infertility and severe impacts on the immune system.

Together with colleagues from a wide range of international universities and research institutions, researchers from Aarhus University have documented that the number of killer whales is rapidly declining in 10 out of the 19 killer whale populations investigated and that the species may disappear entirely from several areas within a few decades.

Killer whales are particularly threatened in heavily contaminated areas like the waters near Brazil, the Strait of Gibraltar and around the UK. Around the British Isles, the researchers estimate that the remaining population counts less than 10 killer whales. Also along the east coast of Greenland, killer whales are effected due to the high consumption of sea mammals like seals.

PCBs accumulate in the food chain

The killer whale is one of the most widespread mammals on Earth and is found in all of the world’s oceans from pole to pole. But today, only the populations living in the least polluted areas possess a large number of individuals.

Overfishing and man-made noise may also affect the health of the animals, but PCBs particularly can have a dramatic effect on the reproduction and immune system of the killer whales.

Killer whales whose diet includes, among other items, seals and large fish such as tuna and sharks critical accumulate PCBs and other pollutants stored at successive levels of the food chain. It is these populations of killer whales that have the highest PCB concentrations and it is these populations that are at the highest risk of population collapse. Killer whales that primarily feed on small-sized fish such as herring and mackerel have a significantly lower content of PCBs and are thus at lower risk of effects.

PCB pollution threatens to wipe out killer whales
When foreign hazardous substances enter the marine environment, they are assimilated into the first link in the food chain,
 phytoplankton. The phytoplankton is consumed by zooplankton, which in turn is consumed by smaller fish, etc. The
 chemicals accumulate in each link of the food chain, and this means that killer whales that feed on large animals
in contaminated areas may contain concentrations of PCBs so high that the survival of the species is threatened.
Killer whales that primarily feed on smaller fish are not threatened in the same way
[Credit: Aarhus University]

PCBs have been used around the world since the 1930s. More than one million tonnes of PCBs were produced and used in, among other things, electrical components and plastics. Together with DDT and other organic pesticides — PCBs have spread around the global oceans.

Through the 1970s and 1980s, PCBs were banned in several countries and in 2004, through the Stockholm Convention, more than 90 countries have committed themselves to phase out and dispose of the large stocks of PCBs.

PCBs are only slowly decomposed in the environment. Moreover, PCBs are passed down from the mother orca to its offspring through the mother’s fat-rich milk. This means that the hazardous substances remain in the bodies of the animals, instead of being released into the environment where they eventually deposit or degrade.

Global investigation of killer whales

“We know that PCBs deform the reproductive organs of animals such as polar bears. It was therefore only natural to examine the impact of PCBs on the scarce populations of killer whales around the world,” says Professor Rune Dietz from the Department of Bioscience and Arctic Research Centre, Aarhus University, who initiated the killer whale studies and is co-author of the article.

The research group, which includes participants from the United States, Canada, England, Greenland, Iceland and Denmark, reviewed all the existing literature and compared all data with their own most recent results. This provided information about PCB levels in more than 350 individual killer whales around the globe — the largest number of killer whales ever studied.

Applying models, the researchers then predicted the effects of PCBs on the number of offspring as well as on the immune system and mortality of the killer whale over a period of 100 years.

More than 50% of the populations under threat

“The findings are surprising. We see that over half of the studied killer whales populations around the globe are severely affected by PCBs” says postdoc Jean-Pierre Desforges from Aarhus University, who led the investigations.

PCB pollution threatens to wipe out killer whales
By collecting data from around the world and loading them into population models, the researchers
can see that 10 out of 19 populations of killer whales are affected by high levels of PCBs in their body.
PCBs particularly affect the reproduction and immune system of the whales. The situation is worst
in the oceans around Brazil and the UK where the model predicts that populations have been cut
 in half over the first decades since the use of PCBs became widespread. Here, the models predict
a high risk that the species will disappear within a 30-40-year period. The line indicates
median values, while the shaded field shows the variation
[Credit: Aarhus University]

The effects result in fewer and fewer animals over time in these populations. The situation is worst in the oceans around Brazil, the Strait of Gibraltar, the northeast Pacific and around the UK. Here, the models show that the populations have virtually been halved during the half century where PCBs have been present.

“In these areas, we rarely observe newborn killer whales,” says Ailsa Hall, who together with Bernie McConnell developed the models used by Sea Mammal Research Unit in Scotland.

“As the effects have been recognized for more than 50 years, it is frightening to see that the models predict a high risk of population collapse in these areas within a period of 30-40 years,” says Jean-Pierre Desforges.

A female killer whale may live for 60-70 years, and although the world took its first steps to phase out PCBs more than 40 years ago, killer whales still have high levels of PCBs in their bodies.

“This suggests that the efforts have not been effective enough to avoid the accumulation of PCBs in high trophic level species that live as long as the killer whale does. There is therefore an urgent need for further initiatives than those under the Stockholm Convention,” concludes Paul D. Jepson, Institute of Zoology, Zoological Society of London, England, who is another killer whale expert and co-author of the article.

In the oceans around the Faroe Islands, Iceland, Norway, Alaska and the Antarctic, the prospects are not so gloomy. Here, killer whale populations grow and the models predict that they will continue to do so throughout the next century.

Source: Aarhus University [September 27, 2018]



Well established theories on patterns in evolution might be wrong

How do the large-scale patterns we observe in evolution arise? A new paper in the journal Evolution by researchers at Uppsala University and University of Leeds argues that many of them are a type of statistical artefact caused by our unavoidably recent viewpoint looking back into the past. As a result, it might not be possible to draw any conclusions about what caused the enormous changes in diversity we see through time.

Well established theories on patterns in evolution might be wrong
Credit: WikiCommons

The diversity of life through time shows some striking patterns. For example, the animals appear in the fossil record about 550 million years ago, in an enormous burst of diversification called the “Cambrian Explosion”. Many groups of organisms appear to originate like this, but later on in their evolutionary history, their rates of diversification and morphological change seem to slow down. These sorts of patterns can be seen both in the fossil record, and also in reconstructions of past diversity by looking at the relationships between living organisms, and they have given rise to a great deal of debate.
Do organisms have more evolutionary flexibility when they first evolve? Or do ecosystems get “filled up” as more species evolve, giving fewer opportunities for further diversification later on? In their new paper, Graham Budd and Richard Mann make the provocative argument that these patterns may be largely illusory, and that we would still expect to see them even if rates of evolutionary change stay the same on average through time.

Biologists and palaeontologists use statistical models called “birth-death models” to model how random events of speciation and extinction give rise to patterns of diversity. Just as one can roll a dice five times and get five sixes or none, the outcomes of these random models are very variable. These statistical fluctuations are particularly important at the origin of a group, when there are only a few species. It turns out that the only groups that survive this early period are those that happen to diversify quickly – all the others go extinct.

As is it exactly those groups that go on to be the large successful groups we see living today, and that fill most of the fossil record, it follows that they are likely to show this rapid pattern of diversification at their origin – but only because they are a biased subset of all groups. Later in their history, when such groups are diverse, statistical fluctuations have much less effect, and therefore their rate of evolution appears to slows down to the background average.

As a result, the patterns we discover by analyzing such groups are not general features of evolution as a whole, but rather represent a remarkable bias that emerges by only studying groups we already know were successful. This bias, called “the push of the past”, has indeed been known about theoretically for about 25 years, but it has been almost completely ignored, probably because it was assumed to be negligible in size.

However, Budd and Mann show that the effect is very large, and can in fact account for much of the variation we see in past diversity, especially when we combine it with the effects of the great “mass extinctions” such as the one that killed off the dinosaurs some 66 million years ago. Because the resulting patterns are an inevitable feature of the sorts of groups available for us to study, Budd and Mann argue, it follows that we cannot perceive any particular cause of them: they simply arise from statistical fluctuation.

The push of the past is an example of a much more general type of pattern called “survivorship bias” which can be seen in many other areas of life, for example in business start-ups and finance and the study of history. In all these cases, failure to recognize the bias can lead to highly misleading conclusions. Budd and Mann argue that the history of life itself is not immune to such effects, and that many traditional explanations for why diversity changes through time may need to be reconsidered – a viewpoint that is bound to prove controversial.

Source: Uppsala University [September 27, 2018]



New study probes the ancient past of a body plan code

Researchers from the Stowers Institute for Medical Research have opened a window on another piece of evolutionary biology. They have found that Hox genes, which are key regulators of the way the bodies of bilaterally symmetrical animals form, also play a role in controlling the radially symmetric body plan of the starlet sea anemone, Nematostella vectensis.

New study probes the ancient past of a body plan code
The sea anemone Nematostella uses an array of elegant tentacles to capture and feed on marine plankton. New research
show that the radial patterning of the tentacles requires Hox genes, which are also found in humans
and other vertebrates where they control body patterning along the head-to-tail axis
[Credit: Ahmet Karrabulut, Gibson Lab]

These findings, published in the journal Science, give researchers a better understanding of these genes’ ancestral function, and a grasp on an important step in evolutionary biology.

“The sea anemone offers us a window into the possible ancient past of Hox gene function,” says Stowers Investigator Matthew Gibson, Ph.D., who led the study.

The roles of Hox genes in bilaterian animals have been well established. These are animals that have a head-to-tail axis, have largely symmetrical left and right sides, and include everything from humans to dogs to fish to spiders. Hox genes control the identity of different segments of these animals as they develop, setting in motion the genetic programs that form various body structures such as limbs and organs. Segment identity depends on which Hox genes are expressed – or the Hox code – in that region of the developing organism.

Although Hox genes have been identified in the group of animals known as Cnidaria, which include radially symmetrical animals like sea anemones, jellyfish, and corals, their particular roles in cnidarian body plan regulation were previously unknown.

“We’ve never had functional evidence for where the Hox code originated and how it may have controlled development before the emergence of the bilaterians,” Gibson said. “By studying the function of Hox genes in a sea anemone we can begin to understand the possible role of these genes in our ancient common ancestor, some 600 million years in the past.”

To tackle this problem, the researchers disrupted the function of the Anthox1a, Anthrox8, Anthrox6a, and Gbx genes in body patterning of the sea anemone Nematostella vectensis. They did this in two ways – they disrupted the function of Hox genes through treatment with short hairpin RNAs, and also used CRISPR-Cas9, a gene editing system, to remove these Hox genes from the genome.

They found that the loss or disruption of Hox gene function led to striking defects in both segmentation of the body and tentacle patterning. The mutant sea anemones developed only two or three tentacles instead of the usual four. Some tentacles were enlarged and partially fused, and others were bifurcated.

“It’s entirely possible that the ancestral role of the Hox genes was to both drive segment formation and confer segment identity,” Gibson said. “In extant bilaterians, these functions may have separated such that Hox genes just control segment identity.”

“These findings uncover the existence of a Hox code in a developing cnidarian, providing evolutionary biologists with new insights into the process of Hox code evolution,” said Shuonan He, a predoctoral researcher at the Graduate School of the Stowers Institute for Medical Research and first author of the paper. “These genes already existed before the split of bilaterians and cnidarians from their common ancestor,” he said. “Now we can look at more cnidarian branches to test if these genes are employed in similar fashion.”

Gibson said that these findings also provide further evidence that evolution doesn’t necessarily make the gene code more complex. “There is a popular notion that the process of evolution increases sophistication and complexity inexorably upward, but we now know in many cases that’s not what happens at all,” he said. “Our ancient animal ancestors had complex biology regulated by the same types of genes that are present in humans today. They were just employed in a different way.”

Source: Stowers Institute for Medical Research [September 27, 2018]



Roman graves discovered near legionary camp Novae in Bulgaria

Rich, well-preserved graves from the Roman period, approx. 1800 years ago, have been discovered by Polish archaeologists during excavations near the legionary camp Novae (near Svishtov) in Bulgaria. This is a rare and unexpected discovery in the Balkans, the discoverers say.

Roman graves discovered near legionary camp Novae in Bulgaria
Credit: A. Tomas

“The people buried in the graves we discovered were probably associated with the Roman legion – perhaps even soldiers. This is indicated by metal parts of outfits. Interestingly, among the burial offerings there were jugs of wine – preserved inside in the form of sediment on the walls”, said the head of excavations in Novae, Dr. Agnieszka Tomas from the Institute of Archaeology, University of Warsaw, who made the discovery with her team in August.
The graves also contained ceramic lamps and preserved elements of clothing, including metal parts of military belts and shoes – buckles and rivets. These, however, are in poor condition, because they were consumed by fire during the cremation ceremony.

Roman graves discovered near legionary camp Novae in Bulgaria
Credit: T. Dziurdzik

Although archaeologists have only found two graves, the consider it a significant find. “These are the first graves from the Roman period preserved in this condition in this area”, emphasises Tomas. Until now, archaeologists only had reports of similar finds in this area discovered accidentally or by looters. Luck smiled on them in Novae: not only did the graves remain almost intact for nearly 2,000 years, they were not touched by present-day robbers. Researchers were able to prepare a complete documentation of the find. They hope to find more burials during the work planned for 2019.
Preliminary analysis shows that men were buried in both graves. In one case, where the bones were less damaged, anthropologist made a preliminary determination that the deceased was a fairly young person. Both bodies were burnt elsewhere, and the remains were placed in wooden boxes, of which only iron nails have survived. Equipment, including coins with images of Roman emperors, supports the conclusion that the deceased were men. The head of excavations added that coins with female images were usually placed in women`s graves.

Roman graves discovered near legionary camp Novae in Bulgaria
Credit: A. Tomas

“A coin was given for the way to the afterlife, because it was believed that the deceased would have to cross a river and the ferryman would expect payment”, explains Tomas.

The archaeologist explains that Roman legionaries came from various areas of the Empire. Therefore, the burial rites varied – it was not always cremation.

Roman graves discovered near legionary camp Novae in Bulgaria
Credit: E. Jeczmienowski

“Interestingly, in the case of the graves we discovered in Novae it is possible that the cremation ritual was repeated in the grave. The incinerated corpses with a dozen or so grave offerings were covered with large ceramic plates, forming a gable-roofed structure”, said Tomas.
The graves discovered by Polish archaeologists are in the area of the remains of a civil settlement located east of the Roman legionary camp in Novae, today`s northern Bulgaria. Archaeologists received funding from the National Science Centre for surveying the area.

Roman graves discovered near legionary camp Novae in Bulgaria
Credit: T. Dziurdzik

“The fact that Roman troops were stationed in camps and forts located throughout the Empire is well-known. But not everyone knows that there were vast civilian settlements around the camps and forts. They are the focus of our research”, says Tomas. She describes that merchants, service providers and families of legionnaires and veterans lived in those settlements. They were melting pots of cultures, languages, traditions, places of coexistence of various social groups. In the second half of the third century, when barbarian invasions intensified and the Roman Empire was in crisis, the camps became shelters for civilians, and later evolved into late-Roman cities.

Dr. Tomas` expedition is one of three Polish missions in Novae. The other two are the expedition of the Antiquity of Southeastern Europe Research Centre University of Warsaw headed by Prof. Piotr Dyczek and the expedition of the Adam Mickiewicz University in Poznań, headed by Dr. Elena Klenina. In addition to Polish researchers, Bulgarian archaeologists under the supervision of Prof. Evgenia Gencheva also work in the area.

Author: Szymon Zdziebłowski | Source: PAP – Science in Poland [September 27, 2018]




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