четверг, 5 декабря 2019 г.

SpaceX Gears Up for Second CRS-19 Launch Attempt













SpaceX - CRS-19 Dragon patch.

December 5, 2019

SpaceX is preparing for the second launch attempt of its 19th Commercial Resupply Services (CRS-19) mission to the International Space Station today at 12:29 p.m. EST (17:29:23 GMT). The company’s Falcon 9 rocket and uncrewed Dragon spacecraft will lift off from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida. Join us here on the blog, as well as on NASA TV and the agency’s website, for live launch countdown coverage, beginning at 12 p.m. EST.


Image above: A SpaceX Falcon 9 rocket stands ready for liftoff at Cape Canaveral Air Force Station’s Space Launch Complex 40 in Florida on Dec. 5, 2019, for the company’s 19th Commercial Resupply Services mission to the International Space Station. Launch is scheduled for 12:29 p.m. EST. Photo credit: NASA.

SpaceX made the decision to call off the first launch attempt yesterday due to upper-altitude winds and high winds at sea, creating dangerous conditions around the drone ship “Of Course I Still Love You,” which the rocket’s first stage will attempt landing on following its separation from the rest of the launch vehicle.

The Dragon spacecraft that will deliver critical supplies, equipment and material to the space station on this mission first flew to the orbiting laboratory in 2014 on CRS-4, and then again on CRS-11, making it the first spacecraft that SpaceX reused for resupply missions. Now preparing to fly for a third time, the material it will carry on CRS-19 will directly support dozens of research investigations taking place in space. To learn more about some of those research experiments, visit: https://www.nasa.gov/mission_pages/station/research/news/spx19-research/

Related links:

International Space Station: https://www.nasa.gov/mission_pages/station/main/index.html

NASA TV: https://www.nasa.gov/nasalive

Image (mentioned), Text, Credits: NASA/Danielle Sempsrott.

Greetings, Orbiter.ch

* This article was originally published here

Compound eyes: The visual apparatus of today's horseshoe crabs goes back 400 million years


The eyes of the extinct sea scorpion Jaekelopterus rhenaniae have the same structure as the eyes of modern horseshoe crabs (Limulidae). The compound eyes of the giant predator exhibited lens cylinders and concentrically organized sensory cells enclosing the end of a highly specialized cell. This is the result of research Dr Brigitte Schoenemann, professor of zoology at the Institute of Biology Didactics at the University of Cologne, conducted with an electron microscope.

Compound eyes: The visual apparatus of today's horseshoe crabs goes back 400 million years
Horseshoe crab [Credit: Shutterstock]
The eyes of modern horseshoe crabs consist of compounds, so-called ommatidia. Unlike, for example, insects that have compound eyes with a simple lens, the ommatidia of horseshoe crabs are equipped with a lens cylinder that continuously refracts light and transmits it to the sensory cells.


These sensory cells are grouped in the form of a rosette around a central light conductor, the rhabdom, which is part of the sensory cells and converts light signals into nerve signals to transmit them to the central nervous system. At the centre of this 'light transmitter' in horseshoe crabs is a highly specialized cell end, which can connect the signals of neighbouring compounds in such a way that the crab perceives contours more clearly. This can be particularly useful in conditions of low visibility under water. In the cross-section of the ommatidium, it is possible to identify the end of this specialized cell as a bright point in the centre of the rhabdom.

Compound eyes: The visual apparatus of today's horseshoe crabs goes back 400 million years
Fossil of J. rhenaniae [Credit: wanderflechten/flickr]
Brigitte Schoenemann used electron microscopes to examine fossil Jaekelopterus rhenaniae specimens to find out whether the compound eyes of the giant scorpion and the related horseshoe crabs are similar or whether they are more similar to insect or crustacean eyes. She found the same structures as in horseshoe crabs. Lens cylinders, sensory cells and even the highly specialized cells were clearly discernible.


'This bright spot belongs to a special cell that only occurs in horseshoe crabs today, but apparently already existed in eurypterida,' explained Schoenemann. 'The structures of the systems are identical. It follows that very probably this sort of contrast enhancement already evolved more than 400 million years ago,' she added. Jaekelopterus most likely hunted placoderm. Here, its visual apparatus was clearly an advantage in the murky seawater.

Compound eyes: The visual apparatus of today's horseshoe crabs goes back 400 million years
Close-up of impressions and fossilizations of the eyes of eurypterid Jaekelopterus rhenaniae
[Credit: Schoenemann et al. 2019]
Sea scorpions, which first appeared 470 million years ago, died out about 250 million years ago, at the end of the Permian age - along with about 95 percent of all marine life. Some specimens were large oceanic predators, such as Jaekelopterus rhenaniae. It reached a length of 2.5 meters and belonged to the family of eurypterida, the extinct relatives of the horseshoe crab. Eurypterida are arthropods, which belong to the subphylum Chelicerata, and are therefore related to spiders and scorpions.


Among the arthropods there are two large groups: mandibulates (crustaceans, insects, trilobites) and chelicerates (arachnid animals such as sea scorpions). In recent years, Schoenemann has been able to clarify the eye structures of various trilobite species and to make decisive contributions to research into the evolution of the compound eye. 'Until recently, scientists thought that soft tissues do not fossilize. Hence these parts of specimens were not examined until not so long ago', she concluded.

Compound eyes: The visual apparatus of today's horseshoe crabs goes back 400 million years
Close-up of a massive Jaekelopterus on the seabed
[Credit: Lucas Lima and Earth Archives]
The new findings on the eye of the sea scorpion are important for the evolution of the compound eyes not only of chelicerates, but also for determining the position of sea scorpions in the pedigree of these animals and for the comparison with the eyes of the related group of mandibulates.

The findings have been published in the journal Scientific Reports.

Source: University of Cologne [December 03, 2019]



* This article was originally published here

First Giant Planet around White Dwarf Found













ESO - European Southern Observatory logo.

4 December 2019

ESO observations indicate the Neptune-like exoplanet is evaporating

 Artist’s impression of the WDJ0914+1914 system

Researchers using ESO’s Very Large Telescope have, for the first time, found evidence of a giant planet associated with a white dwarf star. The planet orbits the hot white dwarf, the remnant of a Sun-like star, at close range, causing its atmosphere to be stripped away and form a disc of gas around the star. This unique system hints at what our own Solar System might look like in the distant future.

“It was one of those chance discoveries,” says researcher Boris Gänsicke, from the University of Warwick in the UK, who led the study, published today in Nature. The team had inspected around 7000 white dwarfs observed by the Sloan Digital Sky Survey and found one to be unlike any other. By analysing subtle variations in the light from the star, they found traces of chemical elements in amounts that scientists had never before observed at a white dwarf. “We knew that there had to be something exceptional going on in this system, and speculated that it may be related to some type of planetary remnant.”

To get a better idea of the properties of this unusual star, named WDJ0914+1914, the team analysed it with the X-shooter instrument on ESO’s Very Large Telescope in the Chilean Atacama Desert. These follow-up observations confirmed the presence of hydrogen, oxygen and sulphur associated with the white dwarf. By studying the fine details in the spectra taken by ESO’s X-shooter, the team discovered that these elements were in a disc of gas swirling into the white dwarf, and not coming from the star itself.

Location of WDJ0914+1914 in the constellation of Cancer

“It took a few weeks of very hard thinking to figure out that the only way to make such a disc is the evaporation of a giant planet,” says Matthias Schreiber from the University of Valparaiso in Chile, who computed the past and future evolution of this system.

The detected amounts of hydrogen, oxygen and sulphur are similar to those found in the deep atmospheric layers of icy, giant planets like Neptune and Uranus. If such a planet were orbiting close to a hot white dwarf, the extreme ultraviolet radiation from the star would strip away its outer layers and some of this stripped gas would swirl into a disc, itself accreting onto the white dwarf. This is what scientists think they are seeing around WDJ0914+1914: the first evaporating planet orbiting a white dwarf.

Combining observational data with theoretical models, the team of astronomers from the UK, Chile and Germany were able to paint a clearer image of this unique system. The white dwarf is small and, at a blistering 28 000 degrees Celsius (five times the Sun's temperature), extremely hot. By contrast, the planet is icy and large—at least twice as large as the star. Since it orbits the hot white dwarf at close range, making its way around it in just 10 days, the high-energy photons from the star are gradually blowing away the planet's atmosphere. Most of the gas escapes, but some is pulled into a disc swirling into the star at a rate of 3000 tonnes per second. It is this disc that makes the otherwise hidden Neptune-like planet visible.

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Channel: Terry's Theories  

Seven bright lights seen through raging thunderstorm location unknown.
Source video : https://www.youtube.com/watch?v=P5i9wLLRuL4

Video length: 2:01
Category: Science & Technology
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Votive Offerings of Roman Coins, some pierced and used as pendants, The National Museum of Scotland,...

Votive Offerings of Roman Coins, some pierced and used as pendants, The National Museum of Scotland, Edinburgh, November 2019.



* This article was originally published here

NASA’s OSIRIS-REx in the Midst of Site Selection












NASA - OSIRIS-REx Mission logo.

Dec. 4, 2019

NASA’s OSIRIS-REx mission is just days away from selecting the site where the spacecraft will snag a sample from asteroid Bennu. After a lengthy and challenging process, the team is finally ready to down-select from the four candidate sites to a primary and backup site.

OSIRIS-REx is NASA’s first asteroid sample return mission, so this decision of a sample collection site is key for asteroid operations and mission success.

After selecting the four candidate sample sites – Sandpiper, Osprey, Kingfisher, and Nightingale – in July, the mission completed its Reconnaissance A phase. During Recon A, the OSIRIS-REx spacecraft performed a month-long series of four flyovers – one over each potential sample collection site. This mission phase provided the team with high-resolution imagery in order to thoroughly examine the sampleability (fine-grained material), topography, albedo, and color of each site. The data collected from these high-altitude flyovers is central for determining which site is best-suited for sample collection.


Image above: These images show the four candidate sample collection sites on asteroid Bennu: Nightingale, Kingfisher, Osprey and Sandpiper. One of these four sites will ultimately be the location on which NASA’s OSIRIS-REx spacecraft will touch down to collect a sample. Image Credits: NASA/Goddard/University of Arizona.

While the mission is one step closer to collecting a sample, Recon A observations have revealed that even the best candidate sites on Bennu pose significant challenges to sample collection, and the choice before the site selection board is not an easy one.

“Sample site selection really is a comprehensive activity. It requires that we look at many different types of data in many different ways to ensure the selected site is the best choice in terms of spacecraft safety, presence of sampleable material, and science value,” said Heather Enos, OSIRIS-REx deputy principal investigator at the University of Arizona, Tucson, and chair of the sample site selection board. “Our team is incredibly innovative and integrated, which is what makes the selection process work.”

The most recent images show that while there is fine-grained material (smaller than 2.5 cm in diameter), much of it may not be easily accessible. The mission was originally designed for a beach-like surface, with “ponds” of sandy material, not for Bennu’s rugged terrain. In reality the potential sample sites are not large, clear areas, but rather small spaces surrounded by large boulders, so navigating the spacecraft in and out of the sites will require a bit more fine-tuning than originally planned.

Starting in Bennu’s southern hemisphere, site Sandpiper was the first flyover of the Recon A mission phase. Sandpiper is one of the “safer” sites because it is located in a relatively flat area, making it easier for the spacecraft to navigate in and out. The most recent images show that fine-grained material is present, but the sandy regolith is trapped between larger rocks, which makes it difficult for the sampling mechanism to operate.

OSIRIS-REx collecting sample on Bennu. Image Credit: NASA

Site Osprey was the second site observed during Recon A. This site was originally chosen based on its strong spectral signature of carbon-rich material and because of a dark patch in the center of the crater, which was thought to possibly be fine-grained material. However, the latest high-resolution imagery of Osprey suggests that the site is scattered with material that may be too large to ingest for the sampling mechanism.

Site Kingfisher was selected because it is located in a small crater – meaning that it may be a relatively young feature compared to Bennu’s larger craters (such as the one in which Sandpiper is located). Younger craters generally hold fresher, minimally-altered material. High-resolution imagery captured during the Recon A flyover revealed that while the original crater may be too rocky, a neighboring crater appears to contain fine-grained material.

Recon A concluded with a flyover of site Nightingale. Images show that the crater holds a good amount of unobstructed fine-grained material. However, while the sampleability of the site ranks high, Nightingale is located far to the north where the lighting conditions create additional challenges for spacecraft navigation. There is also a building-size boulder situated on the crater’s eastern rim, which could be a hazard to the spacecraft when backing away after contacting the site.


Image above: This flat projection mosaic of asteroid Bennu shows the relative locations of the four candidate sample collection sites on the asteroid: Nightingale, Kingfisher, Osprey and Sandpiper. NASA’s OSIRIS-REx spacecraft is scheduled to touch down on one of these four sites to collect a sample in summer 2020. Image Credits: NASA/Goddard/University of Arizona.

Bennu has also made it a challenge for the mission to identify a site that won’t trigger the spacecraft’s safety mechanisms. During Recon A, the team began cataloguing Bennu’s surface features to create maps for the Natural Feature Tracking (NFT) autonomous navigation system. During the sample collection event, the spacecraft will use NFT to navigate to the asteroid’s surface by comparing the onboard image catalog to the navigation images it will take during descent. In response to Bennu’s extremely rocky surface, the NFT system has been augmented with a new safety feature, which instructs it to wave-off the sampling attempt and back away if it determines the point of contact is near a potentially hazardous surface feature. With Bennu’s building-sized boulders and small target sites, the team realizes that there is a possibility that the spacecraft will wave-off the first time it descends to collect a sample.

“Bennu’s challenges are an inherent part of this mission, and the OSIRIS-REx team has responded by developing robust measures to overcome them,” said Mike Moreau, OSIRIS-REx deputy project manager at Goddard. “If the spacecraft executes a wave-off while attempting to collect a sample, that simply means that both the team and the spacecraft have done their jobs to ensure the spacecraft can fly another day. The success of the mission is our first priority.”