среда, 7 августа 2019 г.

Anatomy of a Cosmic Seagull




The Rosy Glow of a Cosmic Seagull

 




The Seagull Nebula on the borders of the constellations of Monoceros and Canis Major


 



Wide-field view of the entire Seagull Nebula (IC 2177)




Videos


ESOcast 205 Light: The Rosy Glow of a Cosmic Seagull



ESOcast 205 Light: The Rosy Glow of a Cosmic Seagull


Panning across the Cosmic Seagull



Panning across the Cosmic Seagull


Zooming into the Cosmic Seagull



Zooming into the Cosmic Seagull


3D animation of the Seagull Nebula



3D animation of the Seagull Nebula





ESO’s VST captures a celestial gull in flight


Colourful and wispy, this intriguing collection of objects is known as the Seagull Nebula, named for its resemblance to a gull in flight. Made up of dust, hydrogen, helium and traces of heavier elements, this region is the hot and energetic birthplace of new stars. The remarkable detail captured here by ESO’s VLT Survey Telescope (VST) reveals the individual astronomical objects that make up the celestial bird, as well as the finer features within them. The VST is one of the largest survey telescopes in the world observing the sky in visible light.


The main components of the Seagull are three large clouds of gas, the most distinctive being Sharpless 2-296, which forms the “wings”. Spanning about 100 light-years from one wingtip to the other, Sh2-296 displays glowing material and dark dust lanes weaving amid bright stars. It is a beautiful example of an emission nebula, in this case an HII region, indicating active formation of new stars, which can be seen peppering this image.


It is the radiation emanating from these young stars that gives the clouds their fantastical colours and makes them so eye-catching, by ionising the surrounding gas and causing it to glow. This radiation is also the main factor that determines the clouds’ shapes, by exerting pressure on the surrounding material and sculpting it into the whimsical morphologies we see. Since each nebula has a unique distribution of stars and may, like this one, be a composite of multiple clouds, they come in a variety of shapes, firing astronomers’ imaginations and evoking comparisons to animals or familiar objects.


This diversity of shapes is exemplified by the contrast between Sh2-296 and Sh2-292. The latter, seen here just below the “wings”, is a more compact cloud that forms the seagull’s “head”. Its most prominent feature is a huge, extremely luminous star called HD 53367 that is 20 times more massive than the Sun, and which we see as the seagull’s piercing “eye”. Sh2-292 is both an emission nebula and a reflection nebula; much of its light is emitted by ionised gas surrounding its nascent stars, but a significant amount is also reflected from stars outside it.


The dark swathes that interrupt the clouds’ homogeneity and give them texture are dust lanes – paths of much denser material that hide some of the luminous gas behind them. Nebulae like this one have densities of a few hundred atoms per cubic centimetre, much less than the best artificial vacuums on Earth. Nonetheless, nebulae are still much denser than the gas outside them, which has an average density of about 1 atom per cubic centimetre.


The Seagull lies along the border between the constellations of Canis Major (The Great Dog) and Monoceros (The Unicorn), at a distance of about 3700 light-years in one arm of the Milky Way. Spiral galaxies can contain thousands of these clouds, almost all of which are concentrated along their whirling arms.


Several smaller clouds are also counted as part of the Seagull Nebula, including Sh2-297, which is a small, knotty addition to the tip of the gull’s upper “wing”, Sh2-292 and Sh2-295. These objects are all included in the Sharpless Catalogue, a list of over 300 clouds of glowing gas compiled by American astronomer Stewart Sharpless.


This image was taken using the VLT Survey Telescope (VST), one of the largest survey telescopes in the world observing the sky in visible light. The VST is designed to photograph large areas of the sky quickly and deeply.



Can you spot the seagull in this photo? We challenge our readers to let their imagination run free and outline the bird in our photo as they see it. Share your photos with the outline of the bird using the hashtag #SpotTheSeagull.





More Information




ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largestastronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.




Contact:


Mariya Lyubenova
ESO Head of Media Relations Team
Garching bei München, Germany
Tel: +49 89 3200 6188
Email:
pio@eso.org


Source: ESO/News








Archive link


5 of Your Fermi Gamma-ray Space Telescope Questions Answered

The Fermi Gamma-ray Space Telescope is a satellite in low-Earth orbit that detects gamma rays from exotic objects like black holes, neutron stars and fast-moving jets of hot gas. For 11 years Fermi has seen some of the highest-energy bursts of light in the universe and is helping scientists understand where gamma rays come from.


Confused? Don’t be! We get a ton of questions about Fermi and figured we’d take a moment to answer a few of them here.


1. Who was this Fermi guy?


The Fermi telescope was named after Enrico Fermi in recognition of his work on how the tiny particles in space become accelerated by cosmic objects, which is crucial to understanding many of the objects that his namesake satellite studies.


Enrico Fermi was an Italian physicist and Nobel Prize winner (in 1938) who immigrated to the United States to be a professor of physics at Columbia University, later moving to the University of Chicago.


image


Original image courtesy Argonne National Laboratory



Over the course of his career, Fermi was involved in many scientific endeavors, including the Manhattan Project, quantum theory and nuclear and particle physics. He even engineered the first-ever atomic reactor in an abandoned squash court (squash is the older, English kind of racquetball) at the University of Chicago.


There are a number of other things named after Fermi, too: Fermilab, the Enrico Fermi Nuclear Generating Station, the Enrico Fermi Institute and more. (He’s kind of a big deal in the physics world.)


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Fermi even had something to say about aliens! One day at lunch with his buddies, he wondered if extraterrestrial life existed outside our solar system, and if it did, why haven’t we seen it yet? His short conversation with friends sparked decades of research into this idea and has become known as the Fermi Paradox — given the vastness of the universe, there is a high probability that alien civilizations exist out there, so they should have visited us by now.  


2. So, does the Fermi telescope look for extraterrestrial life?


No. Although both are named after Enrico Fermi, the Fermi telescope and the Fermi Paradox have nothing to do with one another.


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Fermi does not look for aliens, extraterrestrial life or anything of the sort! If aliens were to come our way, Fermi would be no help in identifying them, and they might just slip right under Fermi’s nose. Unless, of course, those alien spacecraft were powered by processes that left behind traces of gamma rays.


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Fermi detects gamma rays, the highest-energy form of light, which are often produced by events so far away the light can take billions of years to reach Earth. The satellite sees pulsars, active galaxies powered by supermassive black holes and the remnants of exploding stars. These are not your everyday stars, but the heavyweights of the universe. 


3. Does the telescope shoot gamma rays?


No. Fermi DETECTS gamma rays using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM).


The LAT sees about one-fifth of the sky at a time and records gamma rays that are millions of times more energetic than visible light. The GBM detects lower-energy emissions, which has helped it identify more than 2,000 gamma-ray bursts – energetic explosions in galaxies extremely far away.


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The highest-energy gamma ray from a gamma-ray burst was detected by Fermi’s LAT, and traveled 3.8 billion light-years to reach us from the constellation Leo.


4. Will gamma rays turn me into a superhero?


Nope. In movies and comic books, the hero has a tragic backstory and a brush with death, only to rise out of some radioactive accident stronger and more powerful than before. In reality, that much radiation would be lethal.


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In fact, as a form of radiation, gamma rays are dangerous for living cells. If you were hit with a huge amount of gamma radiation, it could be deadly — it certainly wouldn’t be the beginning of your superhero career.


5. That sounds bad…does that mean if a gamma-ray burst hit Earth, it would wipe out the planet and destroy us all?


Thankfully, our lovely planet has an amazing protector from gamma radiation: an atmosphere. That is why the Fermi telescope is in orbit; it’s easier to detect gamma rays in space!


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Gamma-ray bursts are so far away that they pose no threat to Earth. Fermi sees gamma-ray bursts because the flash of gamma rays they release briefly outshines their entire home galaxies, and can sometimes outshine everything in the gamma-ray sky.


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If a habitable planet were too close to one of these explosions, it is possible that the jet emerging from the explosion could wipe out all life on that planet. However, the probability is extremely low that a gamma-ray burst would happen close enough to Earth to cause harm. These events tend to occur in very distant galaxies, so we’re well out of reach.


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We hope that this has helped to clear up a few misconceptions about the Fermi Gamma-ray Space Telescope. It’s a fantastic satellite, studying the craziest extragalactic events and looking for clues to unravel the mysteries of our universe!


Now that you know the basics, you probably want to learn more!
Follow the Fermi Gamma-ray Space Telescope on Twitter (@NASAFermi) or Facebook (@nasafermi), and check out more awesome stuff on our Fermi webpage.


Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.  


Recreated Viking Settlement, Yorkshire Museum of Farming, York, Yorkshire, 3.8.19.











Recreated Viking Settlement, Yorkshire Museum of Farming, York, Yorkshire, 3.8.19.


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SpaceX — AMOS-17 Mission Success


SpaceX — Falcon 9 / Amos-17 Mission patch.


August, 6, 2019



Falcon 9 rocket carrying AMOS-17 launch

On Tuesday, August 6, SpaceX’s Falcon 9 rocket successfully lifted off from Space Launch Complex 40 (SLC-40) at Cape Canaveral Air Force Station, Florida, carrying the AMOS-17 satellite for Spacecom. Liftoff occurred at 7:23 p.m. EDT, or 23:23 UTC and the satellite was deployed approximately 31 minutes after liftoff.



AMOS-17 launch

Video above: A SpaceX Falcon 9 rocket launched the AMOS-17 satellite from Space Launch Complex 40 (SLC-40) at Cape Canaveral Air Force Station, Florida, on 6 August 2019 at 23:23 UTC (19:23 EDT). Falcon 9’s first stage (Block 5 B1047) for the AMOS-17 mission previously supported the Telstar-19 VANTAGE mission in July 2018 and the Es’hail-2 mission in November 2018. Due to mission requirements, SpaceX did not attempt to land Falcon 9’s first stage after launch. Video Credits: SpaceX/SciNews.



AMOS-17 satellite separation

Video above: The AMOS-17 satellite was successfully deployed to a Geostationary Transfer Orbit (GTO) 31 minutes after being launched by a  SpaceX Falcon 9 rocket from Space Launch Complex 40 (SLC-40) at Cape Canaveral Air Force Station, Florida, on 6 August 2019 at 23:23 UTC (19:23 EDT). Falcon 9’s first stage (Block 5 B1047) for the AMOS-17 mission previously supported the Telstar-19 VANTAGE mission in July 2018 and the Es’hail-2 mission in November 2018. Due to mission requirements, SpaceX did not attempt to land Falcon 9’s first stage after launch. Video Credits: SpaceX/SciNews.



AMOS-17 satellite

A SpaceX Falcon 9 rocket launches the Amos 17 communications satellite. Built by Boeing and owned by Spacecom Ltd. of Israel, Amos 17 will provide high-throughput broadband connectivity and other communications services over Africa, the Middle East and Europe.


For more information about SpaceX, visit: https://www.spacex.com/


AMOS-17 satellite: https://www.amos-spacecom.com/satellite/amos-17/


Images, Videos (mentioned), Text, Credits: SpaceX/Günter Space Page/Orbiter.ch Aerospace/Roland Berga.


Greetings, Orbiter.chArchive link


U.S. Cygnus Space Freighter Departs Station



ISS — Expedition 60 Mission patch / Northrop Grumman — Cygnus NG-11 Mission patch.


August 6, 2019



Image above: The U.S. Cygnus space freighter from Northrop Grumman was released from the station’s robotic arm today at 11:15 a.m. EDT. Image Credit: NASA TV.


The Cygnus spacecraft successfully departed the International Space Station three months after arriving at the space station to deliver 7,600 of supplies and scientific experiments to the orbiting laboratory.



NG-11: SS Roger Chaffee Cygnus departure

Video above: Northrop Grumman’s Cygnus spacecraft, dubbed the SS Roger Chaffee, departed the International Space Station on 6 August 2019, at 16:16 UTC (12:15 EDT). The NG-11 Cygnus Cargo Delivery Spacecraft is named in honor of the American astronaut Roger Chaffe, the pilot of the Apollo 1 spacecraft, the first manned mission of the Apollo program. Cygnus delivered about 3450 kilograms (7600 pounds) of cargo to the International Space Station. Video Credits: NASA TV/SciNews.


The Cygnus spacecraft will now remain in orbit until mid-December and coincide with a second Cygnus spacecraft scheduled for launch to the space station in October. This will be the first extended duration flight to demonstrate spacecraft’s capability to fly two Cygnus vehicles simultaneously and support hosted payloads for longer periods of time.


The crew outfitted Cygnus with the SlingShot Deployer that will eject a series of nanosatellites once the spacecraft reaches a safe distance and a higher altitude from the station. Cygnus will continue orbiting Earth for a few more months of systems tests before it reenters the atmosphere above the Pacific Ocean for a fiery demise.



Image above: Expedition 60 Flight Engineers (clockwise from top) Luca Parmitano, Andrew Morgan and Nick Hague work on life support maintenance inside the U.S. Destiny laboratory module. Image Credit: NASA.


Flight Engineer Luca Parmitano of the European Space Agency started Monday collecting his blood samples and stowing them in a science freezer for later analysis. Next, he wore virtual reality goggles for an experiment testing his ability to judge the duration of time. Results are collected before, during and after a spaceflight to understand how time perception is affected in space. The impacts could potentially affect space navigation and other mission-oriented tasks.


Commander Alexey Ovchinin tested Russian smoke detectors, conducted a fit check of the Soyuz MS-12 crew ship seats and worked on space biology gear. Cosmonaut Alexander Skvortsov checked out video gear then studied how microgravity affects pain sensation.


Related articles:


Northrop Grumman Carries Technology, Scientific Investigations on Mission to Space Station
https://orbiterchspacenews.blogspot.com/2019/04/northrop-grumman-carries-technology.html


Liftoff!
https://orbiterchspacenews.blogspot.com/2019/04/liftoff.html


Related links:


Expedition 60: https://www.nasa.gov/mission_pages/station/expeditions/expedition60/index.html


SlingShot Deployer: https://www.nasa.gov/mission_pages/station/research/news/slingshot-small-satellite-deployment-test


BioFabrication Facility: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7599


Time perception: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7504


Pain sensation: https://www.energia.ru/en/iss/researches/human/17.html


Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html


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


Images (mentioned), Video (mentioned), Text, Credits: NASA/Mark Garcia.


Best regards, Orbiter.chArchive link


Flight VA249: Ariane 5 lifts off from French Guiana


ARIANESPACE — Ariane 5 ECA Flight VA249 Mission poster.


August 6, 2019



Ariane 5 ECA Flight VA249 lift off

Arianespace’s Ariane 5 launcher has lifted off from the Spaceport in French Guiana, carrying Intelsat 39 and EDRS-C – which will be deployed during a sequence lasting 33 minutes from liftoff to final separation.



Ariane 5 ECA launches Intelsat 39 and EDRS-C

Video above: An Ariane 5 ECA launch vehicle (Ariane Flight VA249) launched Intelsat 39 and EDRS-C satellites to Geostationary Transfer Orbit (GTO) from Ariane Launch Complex No. 3 (ELA 3) at Guiana Space Centre in Kourou, French Guiana, on 6 August 2019 at 19:30 UTC (16:30 local time). Intelsat 39 telecommunication satellite is the 61st satellite launched by Arianespace for Intelsat and will replace Intelsat 902 (launched by Arianespace in 2001) at 62 degrees East. The EDRS-C satellite is the second node of the SpaceDataHighway network, the world’s first “optical fiber” network in the sky based on cutting-edge laser technology. Video Credits: Arianespace TV/SciNews.



VA249 Launch Sequence. Video Credit: Arianespace TV

Payload lift performance for today’s mission to geostationary transfer orbit – designated Flight VA249 in Arianespace’s launcher family numbering system – is approximately 10,660 kg. This total includes the two satellite passengers, plus the workhorse vehicle’s dual-payload deployment system and integration hardware.


Intelsat 39



Intelsat 39 will be the 61st satellite launched by Arianespace for Intelsat since the first mission at its service in 1983. It will replace Intelsat 902 (launched by Arianespace in 2001) at 62 degrees East.


The Intelsat 39 telecommunication satellite is designed with both wide and high-powered steerable spot beams to meet the needs of broadband networking, video and government customers across Africa, Asia, Europe, the Middle East and Indian Ocean region. The steerable spot beams provide flexibility within the payload and enable customers to rapidly and efficiently respond to shifts in geographic or application requirements. The satellite features C-and Ku-band capabilities to provide additional scale for Intelsat’s Flex managed service and enhance mobile connectivity for aero, maritime and government users operating across these regions.


Intelsat 39 is a powerful platform that will enable mobile network operators, enterprises and internet service providers to deliver faster and more efficient connectivity services. It will also provide government entities with the ability to expand connectivity to more remote areas and continue to narrow the digital divide. Intelsat 39 is based on the powerful 1300 platform, which has the flexibility to support a broad range of applications and technology advances, including electric propulsion.


Intelsat 39 was built by Maxar in Palo Alto, California. Maxar is a leading provider of innovative spacecraft systems with deep experience in building and integrating some of the world’s most powerful and comprehensive spacecraft.


Intelsat 39 will be the 57th satellite based on a Maxar 1300 platform launched by Arianespace.


EDRS-C



The EDRS-C satellite is the second node of the SpaceDataHighway network. The SpaceDataHighway is the world’s first “optical fiber” network in the sky based on cutting-edge laser technology. It is a unique network of geostationary satellites permanently fixed over a network of ground stations that can transmit data at a rate of 1.8 Gbit/s It will help to improve environmental and security monitoring, disaster response and crisis management.


As a result, Arianespace once again ensures its leading mission to offer an independent access to space for European flagship programs.


The SpaceDataHighway system will relay larger volumes of image data in a secure way. From its position in geostationary orbit, the SpaceDataHighway system relays data collected by observation satellites to Earth in near-real-time, a process that would normally take several hours. It thus enables the quantity of image and video data transmitted by observation satellites to be tripled and their mission plan to be reprogrammed at any time and in just a few minutes.


Launched into a geostationary orbit at 31° East, EDRS-C will be able to connect low-orbiting observation satellites via laser at a distance up to 45,000 km., as well as intelligence UAVs or mission aircraft. The SpaceDataHighway is a public–private partnership between the European Space Agency (ESA) and Airbus, with the laser terminals developed by Tesat-Spacecom and Germany’s DLR Aerospace Center. Airbus owns, operates and provides services for the SpaceDataHighway. The EDRS-C satellite platform is supplied by OHB System AG.


In addition, a hosted payload – HYLAS 3 – was provided by Avanti Communications under a contract with ESA as a customer-furnished item to OHB.


EDRS-C/HYLAS 3 will be: the 132th satellite launched for Airbus by Arianespace, the 26th satellite based on an OHB platform; and the 4th Avanti payload to be launched by Arianespace.


Related article:


Satellite with Swiss equipment ready to fly
https://orbiterchspacenews.blogspot.com/2019/08/satellite-with-swiss-equipment-ready-to.html


Related links:


European Space Agency (ESA): http://www.esa.int/ESA


EDRS: http://www.esa.int/Our_Activities/Telecommunications_Integrated_Applications/EDRS


Arianespace: http://www.arianespace.com/


Intelsat: http://www.intelsat.com/


Images, Videos (mentioned), Text, Credits: Arianespace/ESA/Airbus/Orbiter.ch Aerospace/Roland Berga.


Best regards, Orbiter.chArchive link


Our Sun Today


NASA — Solar Dynamics Observatory (SDO) patch.


Aug. 6, 2019



NASA’s Solar Dynamic Observatory, or SDO, was the first mission to be launched for NASA’s Living With a Star (LWS) Program, and is designed to understand the causes of solar variability and its impacts on Earth. SDO ​launched on February 11, 2010, on its journey to help us understand the Sun’s influence on Earth and Near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously.


SDO’s goal is to understand, driving towards a predictive capability, the solar variations that influence life on Earth and humanity’s technological systems by determining how the Sun’s magnetic field is generated and structured, and how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance.



Solar Dynamics Observatory (SDO)

Each day, SDO images the sun in a variety of wavelengths. Find daily images here: https://sdo.gsfc.nasa.gov/data/


SDO (Solar Dynamics Observatory): http://www.nasa.gov/mission_pages/sdo/main/index.html


Image; Animation, Text, Credits: NASA/Yvette Smith.


Greetings, Orbiter.chArchive link


HiPOD 6 August 2019: In Etched TerrainA previous image here…



HiPOD 6 August 2019: In Etched Terrain


A previous image here showed evidence of recurring slope lineae, so this picture is a follow-up to see if this might be a good candidate for them, although the lineae really aren’t very prominent. Still, we have to look!


ID: ESP_055016_1815
date: 22 April 2018
altitude: 270 km


NASA/JPL/University of Arizona


Ice Pop Engineers, biologists and geologists are all…


Ice Pop


Engineers, biologists and geologists are all fascinated by freezing – watching how cold spreads along metal girders, through blood or tissue, or perhaps over mountains and glaciers. Freezing bubbles present a different challenge, as cold travels differently around their domes. This soap bubble is sitting on a bed of ice in a room chilled to around —18 degrees Celsius. Running top left to bottom right here, a temperature ‘front’ steadily moves up the bubble – known as Marangoni flow – flaking away ice crystals in a ‘snow globe’ pattern before the bubble frosts up altogether. Bubbles attempting to freeze in warmer surroundings can’t conduct temperature in the same way and eventually collapse. As bubbles are an essential part of drug-carrying emulsions, such insights may suggest more efficient forms of storage for longer-lasting drug compounds.


Written by John Ankers



You can also follow BPoD on Instagram, Twitter and Facebook


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Shining (Star) light on the Search for Life


NASA’s Goddard Space Flight Center logo.


Aug. 6, 2019


In the hunt for life on other worlds, astronomers scour over planets that are light-years away. They need ways to identify life from afar — but what counts as good evidence?


Our own planet provides some inspiration. Microbes fill the air with methane; photosynthesizing plants expel oxygen. Perhaps these gases might be found wherever life has taken hold.



Animation above: An artist’s conception of an Earth-like exoplanet. Animation Credits: NASA/GSFC/C. Meaney/B. Monroe/S. Wiessinger.


But on worlds very different from our own, putative signs of life can be stirred up by non-biological processes. To know a true sign when you see it, astronomer Kevin France at the University of Colorado, Boulder, says, you must look beyond the planet itself, all the way to the gleaming star it orbits.


To this end, France and his team designed the SISTINE mission. Flying on a sounding rocket for a 15-minute flight, it will observe far-off stars to help interpret signs of life on the planets that orbit them. The mission will launch from the White Sands Missile Range in New Mexico in the early morning hours of Aug. 5, 2019.


When Earth Is a Bad Example


Shortly after Earth formed 4.6 billion years ago, it was enveloped by a noxious atmosphere. Volcanoes spewed methane and sulfur. The air teemed with up to 200 times more carbon dioxide than today’s levels.



Image above: The young Earth’s atmosphere might have looked like this artist’s interpretation — a pale orange dot. Image Credits: NASA/GSFC/F. Reddy.


It wasn’t for another billion and a half years that molecular oxygen, which contains two oxygen atoms, entered the scene. It was a waste product, discarded by ancient bacteria through photosynthesis. But it kick-started what became known as the Great Oxidization Event, permanently changing Earth’s atmosphere and paving the way for more complex lifeforms.


“We would not have large amounts of oxygen in our atmosphere if we didn’t have that surface life,” France said.


Oxygen is known as a biomarker: a chemical compound associated with life. Its presence in Earth’s atmosphere hints at the lifeforms lurking below. But as sophisticated computer models have now shown, biomarkers on Earth aren’t always so trustworthy for exoplanets, or planets orbiting stars elsewhere in the universe.


France points to M-dwarf stars to make this case. Smaller and colder than our Sun, M-dwarfs account for nearly three-quarters of the Milky Way’s stellar population. To understand exoplanets that orbit them, scientists simulated Earth-sized planets circling M-dwarfs. Differences from Earth quickly emerged.


M-dwarfs generate intense ultraviolet light. When that light struck the simulated Earth-like planet, it ripped the carbon from carbon dioxide, leaving behind free molecular oxygen. UV light also broke up molecules of water vapor, releasing single oxygen atoms. The atmospheres created oxygen — but without life.


“We call these false-positive biomarkers,” France said. “You can produce oxygen on an Earth-like planet through photochemistry alone.”


Earth’s low oxygen levels without life were a kind of fluke – thanks, in part, to our interaction with our Sun. Exoplanet systems with different stars might be different. “If we think we understand a planet’s atmosphere but don’t understand the star it orbits, we’re probably going to get things wrong,” France said.


To Know a Planet, Study its Star


France and his team designed SISTINE to better understand host stars and their effects on exoplanet atmospheres. Short for Suborbital Imaging Spectrograph for Transition region Irradiance from Nearby Exoplanet host stars, SISTINE measures the high-energy radiation from these stars. With knowledge about host stars’ spectra, scientists can better distinguish true biomarkers from false-positives on their orbiting planets.


To make these measurements, SISTINE uses a spectrograph, an instrument that separates light into its component parts.


“Spectra are like fingerprints,” said Jane Rigby, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who uses the methodology. “It’s how we find out what things are made of, both on our planet and as we look out into the universe.”


SISTINE measures spectra in wavelengths from 100 to 160 nanometers, a range of far-UV light that, among other things, can create oxygen, possibly generating a false-positive. Light output in this range varies with the mass of the star — meaning stars of different masses will almost surely differ from our Sun.



Image above: The Hubble Space Telescope captured this image of Planetary Nebula NGC 6826 Jan. 27, 1996. SISTINE will image NGC 6826 during its first flight to calibrate its instruments. Image Credits: HST/NASA/ESA.


SISTINE can also measure flares, or bright stellar explosions, which release intense doses of far-UV light all at once. Frequent flares could turn a habitable environment into a lethal one.


The SISTINE mission will fly on a Black Brant IX sounding rocket. Sounding rockets make short, targeted flights into space before falling back to Earth; SISTINE’s flight gives it about five minutes observing time. Though brief, SISTINE can see stars in wavelengths inaccessible to observatories like the Hubble Space Telescope.


Two launches are scheduled. The first, from White Sands in August, will calibrate the instrument. SISTINE will fly 174 miles above Earth’s surface to observe NGC 6826, a cloud of gas surrounding a white dwarf star located about 2,000 light-years away in the constellation Cygnus. NGC 6826 is bright in UV light and shows sharp spectral lines — a clear target for checking their equipment.


After calibration, the second launch will follow in 2020 from the Arnhem Space Centre in Nhulunbuy, Australia. There they will observe the UV spectra of Alpha Centauri A and B, the two largest stars in the three-star Alpha Centauri system. At 4.37 light-years away, these stars are our closest stellar neighbors and prime targets for exoplanet observations. (The system is home to Proxima Centauri B, the closest exoplanet to Earth.)



Image above: The Alpha Centauri system in optical (main) and X-ray (inset) light. Only the two largest stars, Alpha Cen A and B, are visible. These two stars will be the targets of SISTINE’s second flight. Image Credits: Zdenek Bardon/NASA/CXC/Univ. of Colorado/T. Ayres et al.


Testing New Tech


Both SISTINE’s observations and the technology used to acquire them are designed with future missions in mind.


One is NASA’s James Webb Space Telescope, currently set to launch in 2021. The deep space observatory will see visible to mid-infrared light — useful for detecting exoplanets orbiting M-dwarfs. SISTINE observations can help scientists understand the light from these stars in wavelengths that Webb can’t see.


SISTINE also carries novel UV detector plates and new optical coatings on its mirrors, designed to help them better reflect rather than absorb extreme UV light. Flying this technology on SISTINE helps test them for NASA’s future large UV/optical space telescopes.


By capturing stellar spectra and advancing technology for future missions, SISTINE links what we know with what we’ve yet to learn. That’s when the real work starts. “Our job as astronomers is to piece those different data sets together to tell a complete story,” Rigby said.


Related links:


More about SISTINE: https://sites.wff.nasa.gov/code810/news/story239-36.346%20SISTINE.html


More about exoplanets: https://exoplanets.nasa.gov/


Astrobiology: https://www.nasa.gov/content/the-search-for-life


Hubble Space Telescope (HST): https://hubblesite.org/


James Webb Space Telescope (JWST): https://www.nasa.gov/webb


Sounding Rockets: http://www.nasa.gov/mission_pages/sounding-rockets/index.html


Goddard Space Flight Center (GSFC): https://www.nasa.gov/centers/goddard/home/index.html


Animation (mentioned), Images (mentioned), Text, Credits: NASA’s Goddard Space Flight Center, by Miles Hatfield.


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