PSLV Successfully Launches Six Satellites from Singapore

ISRO - Indian Space Research Organisation logo.


Dec 16, 2015

In its thirty second flight conducted from Satish Dhawan Space Centre (SDSC), SHAR, Sriharikota today evening (December 16, 2015) at 12:30 GMT (7:30 a.m. EST), ISRO's Polar Satellite Launch Vehicle PSLV-C29 (PSLV-CA configuration) successfully launched six satellites from Singapore, including the 400 kg TeLEOS-1, the primary satellite.

Image above: India’s Polar Satellite Launch Vehicle (PSLV) rocket carrying TeLEOS 1 satellite, liftoff from Satish Dhawan Space Center.

The other five satellites were co. passenger payloads. PSLV-C29 launched all the six payloads into an orbit of 549 km height inclined at an angle of 15 deg to the equator. The six satellites carried by PSLV-C29 today together weighed about 624 kg at lift-off.

These six satellites were launched as part of the agreement entered into between ST Electronics (Satcom & Sensor Systems), Singapore and Antrix Corporation Limited, the commercial arm of the Indian Space Research Organisation (ISRO), a government of India Company under the Department of Space (DOS).

Launch of Indian PSLV Rocket with TeLEOS-1 Onboard (C-29)

This is the eleventh flight of PSLV in ‘core-alone’ configuration (without the use of solid strap-on motors). PSLV has successfully launched 57 satellites for customers from abroad including the six Singapore satellites launched today. After a 59 hour smooth count down, the 227.6 ton PSLV-C29 lifted off from the First Launch Pad (FLP) at SDSC SHAR at 1800 hrs (6:00 pm) IST with the ignition of its first stage.

The important flight events included the separation of the first stage, ignition of the second stage, separation of the payload fairing at about 117 km altitude, second stage separation, third stage ignition and separation, fourth stage ignition and cut-off. Once the intended orbit was achieved, TeLEOS-1 was deployed at about 18 min 12 seconds after lift-off. This was followed by the deployment of other five satellites, viz., Kent Ridge-1, VELOX-C1, VELOX-II, Galassia and Athenoxat-1 in quick succession in the subsequent three minutes.

TeLEOS 1 satellite

The largest of the satellites, TeLEOS 1, is an Earth observation satellite designed to operate in an equatorial orbit for AgilSpace. Four other satellites aboard the launch were developed by university students in Singapore will test new technologies, observe Earth and study the climate.

For more information about Indian Space Research Organisation (ISRO), visit: http://www.isro.gov.in/

Images, Video, Text, Credits: ISRO/Günter Space Page/Orbiter.ch Aerospace.

Greetings, Orbiter.ch

Hubble captures first-ever predicted exploding star

ESA - Hubble Space Telescope logo.

16 December 2015

Caught in the act

Third appearance of the Refsdal supernova

The NASA/ESA Hubble Space Telescope has captured the image of the first-ever predicted supernova explosion. The reappearance of the Refsdal supernova was calculated from different models of the galaxy cluster whose immense gravity is warping the supernova’s light.

Many stars end their lives with a with a bang, but only a few of these stellar explosions have been caught in the act. When they are, spotting them successfully has been down to pure luck — until now. On 11 December 2015 astronomers not only imaged a supernova in action, but saw it when and where they had predicted it would be.

The supernova, nicknamed Refsdal [1], has been spotted in the galaxy cluster MACS J1149.5+2223. While the light from the cluster has taken about five billion years to reach us, the supernova itself exploded much earlier, nearly 10 billion years ago [2].

Appearance of the the Refsdal supernova

Refsdal’s story began in November 2014 when scientists spotted four separate images of the supernova in a rare arrangement known as an Einstein Cross around a galaxy within MACS J1149.5+2223 (heic1505) [3]. The cosmic optical illusion was due to the mass of a single galaxy within the cluster warping and magnifying the light from the distant stellar explosion in a process known as gravitational lensing [4].

"While studying the supernova, we realised that the galaxy in which it exploded is already known to be a galaxy that is being lensed by the cluster,” explains Steve Rodney, co-author, from the University of South Carolina. “The supernova's host galaxy appears to us in at least three distinct images caused by the warping mass of the galaxy cluster.”

These multiple images of the galaxy presented a rare opportunity. As the matter in the cluster — both dark and visible — is distributed unevenly, the light creating each of these images takes a different path with a different length. Therefore the images of the host galaxy of the supernova are visible at different times.

Illustration showing gravitational lensing producing supernova images

Using other lensed galaxies within the cluster and combining them with the discovery of the Einstein Cross event in 2014, astronomers were able to make precise predictions for the reappearance of the supernova. Their calculations also indicated that the supernova appeared once before in a third image of the host galaxy in 1998 — an event not observed by any telescope. To make these predictions they had to use some very sophisticated modelling techniques.

“We used seven different models of the cluster to calculate when and where the supernova was going to appear in the future. It was a huge effort from the community to gather the necessary input data using Hubble, VLT-MUSE, and Keck and to construct the lens models,” explains Tommaso Treu, lead author of the modelling comparison paper, from the University of California at Los Angeles, USA. “And remarkably all seven models predicted approximately the same time frame for when the new image of the exploding star would appear”.

Since the end of October 2015 Hubble has been periodically peering at MACS J1149.5+2223, hoping to observe the unique rerun of the distant explosion and prove the models correct. On 11 December Refsdal finally made its predicted, but nonetheless showstopping, reappearance.

Appearances of the Refsdal supernova

“Hubble has showcased the modern scientific method at its best,” comments Patrick Kelly, lead author of the discovery and re-appearance papers and co-author of the modelling comparison paper from the University of California Berkeley, USA. “Testing predictions through observations provides powerful means of improving our understanding of the cosmos.”

The detection of Refsdal’s reappearance served as a unique opportunity for astronomers to test their models of how mass — especially that of mysterious dark matter — is distributed within this galaxy cluster. Astronomers are now eager to see what other surprises the ongoing Hubble Frontier Fields programme will bring to light.

Notes:

[1] The supernova has been nicknamed Refsdal in honour of the Norwegian astronomer Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a lensed supernova to study the expansion of the Universe.

[2] The W. M. Keck Observatory on Mauna Kea, in Hawaii, was used to measure the redshift of the supernova’s host galaxy (z = 1.491), which is a proxy to its distance.

[3] Hubble observed MACS J1149.5+2223 as part of the Grism Lens Amplified Survey from Space (GLASS) and the Frontier Fields programme. Both surveys are exploiting the lensing properties of galaxy clusters to examine the dark matter within them and some of the most distant galaxies beyond them.

[4] Gravitational lensing magnifies the light from fainter, background objects, allowing Hubble to spy galaxies it would otherwise not be able to detect. The process was first predicted by Albert Einstein and is now being exploited by the Frontier Fields programme in order to find some of the most distant galaxies in the Universe.

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Links:

- heic1505: http://www.spacetelescope.org/news/heic1505/
- Galaxy cluster MACS J1149.5+2223: http://frontierfields.org/2014/02/25/meet-the-frontier-fields-macs-j1149-52223/

- First observation of Refsdal supernova: http://www.spacetelescope.org/news/heic1505/

- Announcement on the search programme: https://www.spacetelescope.org/announcements/ann1526/

- Link to science paper (prediction): http://www.spacetelescope.org/static/archives/releases/science_papers/heic1525b.pdf

- Link to science paper (reappearance): http://www.spacetelescope.org/static/archives/releases/science_papers/heic1525a.pdf

- ESO announcement: https://www.eso.org/public/announcements/ann15088/

- Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

NASA Hubble Space Telescope website: http://hubblesite.org/

Images, Video, Text, Credits: NASA/ESA/S. Rodney (John Hopkins University, USA) and the FrontierSN team; T. Treu (University of California Los Angeles, USA), P. Kelly (University of California Berkeley, USA) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)/Music: Johan B Monell.

Best regards, Orbiter.ch

ALMA Reveals Planetary Construction Sites

ALMA - Atacama Large Millimeter/submillimeter Array logo.

16 December 2015

New evidence for young planets in discs around young stars

Artist’s impression of a transitional disc around a young star

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the clearest indications yet that planets with masses several times that of Jupiter have recently formed in the discs of gas and dust around four young stars. Measurements of the gas around the stars also provide additional clues about the properties of those planets.

Planets are found around nearly every star, but astronomers still do not fully understand how — and under what conditions — they form. To answer such questions, they study the rotating discs of gas and dust present around young stars from which planets are built. But these discs are small and far from Earth, and the power of ALMA was needed for them to reveal their secrets.

Schematic view of a transitional disc around a young star

A special class of discs, called transitional discs, have a surprising absence of dust in their centres, in the region around the star. Two main ideas have been put forward to explain these mysterious gaps. Firstly, the strong stellar winds and intense radiation could have blown away or destroyed the encircling material [1]. Alternatively, massive young planets in the process of formation could have cleared the material as they orbit the star [2].

The unparalleled sensitivity and image sharpness of ALMA have now allowed the team of astronomers, led by Nienke van der Marel from the Leiden Observatory in the Netherlands to map the distribution of gas and dust in four of these transitional discs better than ever before [3]. This in turn has allowed them to choose between the two options as the cause of the gaps for the first time.

ALMA imaging of the transitional disc HD 135344B

The new images show that there are significant amounts of gas within the dust gaps [4]. But to the team’s surprise, the gas also possessed a gap, up to three times smaller than that of the dust.

This could only be explained by the scenario in which newly formed massive planets have cleared the gas as they travelled around their orbits, but trapped the dust particles further out [5].

“Previous observations already hinted at the presence of gas inside the dust gaps,” explains Nienke van der Marel. “But as ALMA can image the material in the entire disc in much greater detail than other facilities, we could rule out the alternative scenario. The deep gap points clearly to the presence of planets with several times the mass of Jupiter, creating these caverns as they sweep through the disc.”

ALMA imaging of the transitional disc DoAr 44

Remarkably, these observations were conducted utilising just one tenth of the current resolving power of ALMA, as they were performed whilst half of the array was still under construction on the Chajnantor Plateau in northern Chile.

Further studies are now needed to determine whether more transitional discs also point towards this planet-clearing scenario, although ALMA’s observations have, in the meantime, provided astronomers with a valuable new insight into the complex process of planetary formation.

Artist’s impression of a transitional disc around a young star

“All the transitional discs studied so far that have large dust cavities also have gas cavities. So, with ALMA, we can now find out where and when giant planets are being born in these discs, and compare these results with planet formation models,” says Ewine van Dishoeck, also of Leiden University and the Max Planck Institute for Extraterrestrial Physics in Garching [6]. “Direct planetary detection is just within reach of current instruments, and the next generation telescopes currently under construction, such as the European Extremely Large Telescope, will be able to go much further. ALMA is pointing out where they will need to look.”

Artist’s impression of a transitional disc around a young star

Notes:

[1] This process, which clears the dust and gas from the inside out, is known as photoevaporation.

[2] Such planets are difficult to observe directly (eso1310) and previous studies at millimetre wavelengths (eso1325) have failed to achieve a sharp view of their inner, planet-forming zones where these different explanations could be put to the test. Other studies (eso0827) could not measure the bulk of the gas in these discs.

- eso1310: https://www.eso.org/public/news/eso1310/
- eso1325: https://www.eso.org/public/news/eso1325/
- eso0827: https://www.eso.org/public/news/eso0827/

[3] The four targets of these investigations were SR 21, HD 135344B (also known as SAO 206462), DoAr 44 and Oph IRS 48.

- SR 21: http://www.circumstellardisks.org/show.php?id=149
- HD 135344B: http://www.circumstellardisks.org/show.php?id=53
- DoAr 44: http://www.circumstellardisks.org/show.php?id=34
- Oph IRS 48: https://www.eso.org/public/news/eso1325/

[4] The gas present in transitional discs consists primarily of hydrogen, and is traced through observations of the carbon monoxide — or CO — molecule.

[5] The process of dust trapping is explained in an earlier release (eso1325).

[6] Other examples include the HD 142527 (http://www.eso.org/public/news/eso1301/ and http://almaobservatory.org/en/press-room/press-releases/666-alma-discovers-a-formation-site-of-a-giant-planetary-systeme) and J1604-2130 transitional discs.

More information:

This research was presented in a paper entitled “Resolved gas cavities in transitional disks inferred from CO isotopologs with ALMA”, by N. van der Marel, et al., to appear in Astronomy & Astrophysics in December 2015.

The team is composed of N. van der Marel (Leiden University, Leiden, the Netherlands; Institute for Astronomy, University of Hawaii, Honolulu, USA), E. F. van Dishoeck (Leiden University, Leiden, the Netherlands; Max Planck Institute for Extraterrestrial Physics, Garching, Germany), S. Bruderer (Max-Planck Institute for Extraterrestrial Physics, Garching, Germany), S. M. Andrews (Harvard-Smithsonian Center for Astrophysics, Massachusetts, USA), K. M. Pontoppidan (Space Telescope Science Institute, Baltimore, Maryland, USA), G. J. Herczeg (Peking University, Beijing, China), T. van Kempen (Leiden University, Leiden, the Netherlands) and A. Miotello (Leiden University, Leiden, the Netherlands).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Research paper in Astronomy & Astrophysics:
http://www.eso.org/public/archives/releases/sciencepapers/eso1549/eso1549a.pdf

Photos of ALMA: http://www.eso.org/public/images/archive/search/?adv=&subject_name=Atacama%20Large%20Millimeter/submillimeter%20Array

Related links:

Leiden Observatory: https://www.strw.leidenuniv.nl/

Atacama Large Millimeter/submillimeter Array (ALMA): http://www.eso.org/alma

Images, Videos, Text, Credits: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser.

Best regards, Orbiter.ch

Plunging into the Ionosphere: Satellite’s Last Days Improve Orbital Decay Predictions

NASA - Goddard Space Flight Center logo.

Dec. 15, 2015

Scientists are learning more about how the upper atmosphere and ionosphere affect space satellites as well as communications and navigation here on Earth, thanks to new data from a U.S. Air Force satellite that recently completed a more than seven-year mission.

The Communication/Navigation Outage Forecasting System (C/NOFS) satellite burned up in Earth’s atmosphere during a planned reentry on Nov. 28, leaving behind a treasure trove of data about a part of the space environment that’s difficult to study. The unique set of sustained observations from C/NOFS will greatly improve models currently used to predict satellite trajectories, orbital drag and uncontrolled re-entry.

Image above: The U.S. Air Force Communication/Navigation Outage Forecasting System re-entered Earth's atmosphere on Nov. 28, 2015, after a more than seven-year mission. Observations during its last year will help scientists better predict orbital decay. Image Credits: NASA's Goddard Space Flight Center.

Scientists from the U.S. Air Force, NASA, and the University of Texas (UT) at Dallas are presenting the results at the American Geophysical Union Fall Meeting in San Francisco.

Launched on April 16, 2008, C/NOFS studied a region high above in our atmosphere called the ionosphere, a layer of electrically charged particles created by ultra-violet radiation from the sun. This layer lies some 40 to 600 miles above the Earth’s surface, where it interacts and co-mingles with the neutral particles of the tenuous upper atmosphere. The upper atmosphere and ionosphere change constantly in response to forces from above and below, including explosions on the sun, intense upper atmosphere winds, and dynamic electric field changes. In addition to interfering with satellite orbits, such changes can produce turbulence in the ionosphere that cause what's known as scintillations, which interfere with radio wave navigation and communication systems, especially at low latitudes near the equator.

During most of its lifetime, C/NOFS never came closer than about 250 miles above the ground. However, as solar activity increased, C/NOFS began to orbit at lower and lower altitudes—ultimately descending to less than 160 miles above Earth.  

During its last 13 months of operations, as its orbit decayed and it spiraled into lower altitudes and eventual re-entry into Earth’s atmosphere, C/NOFS satellite captured a unique set of comprehensive observations as it traveled through the very space environment that can directly cause premature orbital decay. Such regions have rarely been studied directly for extended periods of time, because orbits in this denser region of the atmosphere are not sustainable long-term without on board propulsion.

"One thing we learned clearly from C/NOFS is just how hard it is to predict the precise time and location of re-entry," said Cassandra Fesen, principal investigator for C/NOFS at the Air Force Research Laboratory at the Kirtland Air Force Base in Albuquerque, New Mexico.

The C/NOFS data at these lower altitudes show that the upper atmosphere and ionosphere react strongly to even small changes in near-Earth space, said Rod Heelis, principal investigator at the UT-Dallas for NASA's Coupled Ion-Neutral Dynamics Investigation (CINDI) instrument suite on board the satellite.

Animation above: The ionosphere lies some 40 to 600 miles above Earth’s surface, where it interacts and co-mingles with the neutral particles of the tenuous upper atmosphere. The upper atmosphere and ionosphere change constantly in response to forces from above and below, including explosions on the sun, intense upper atmosphere winds and dynamic electric field changes. Animation Credits: NASA's Goddard Space Flight Center.

"The neutral atmosphere responds very dramatically to quite small energy inputs," said Heelis. "Even though the energy is put in at high latitudes – closer to the poles – the reaction at lower latitudes, near the equator, is significant."

Heelis also described research on a previously-hard-to-view sweet spot in the atmosphere, where the charged particles of the ionosphere and the neutral particles of the atmosphere directly affect each other. The CINDI observations show that the neutral wind creates piles of neutral gas pushed up against ionospheric density variations – similar to how blowing snow piles up in drifts against a building wall. This results in density striations in the atmosphere that were never previously observed. Such density variations are necessary data to include when modeling interference with radio waves or excess drag on a travelling spacecraft.

Rob Pfaff, project scientist for CINDI at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and principal investigator for another C/NOFS instrument, the Vector Electric Field Investigation, is studying observations that speak to one of the original goals of the C/NOFS program: Why does the low latitude ionosphere at night become so turbulent that it can wreak havoc on communications and navigation radio signals?

Graphic above: The U.S. Air Force Communication/Navigation Outage Forecasting System observed how changes in Earth's ionosphere cause what's known as scintillations, which interfere with radio wave navigation and communication systems, especially at low latitudes near the equator. Graphic Credits: U.S. Air Force Research Laboratory.

Developing the capability to predict such space weather disturbances has been a long-standing goal of the Air Force Research Laboratory. The C/NOFS low altitude observations were critical to form a complete picture of these disturbances, as the satellite ventured to the possible root of the largest ionospheric upheavals -- those that emanate from the bottom ledge of the ionosphere at night. The observations revealed the presence of strong shears in the horizontal ionosphere motions at the base of the ionosphere, places where charged particles flow by each other in opposite directions. C/NOFS observed shears and undulations along this boundary. Such shears and undulations -- spotted throughout the nighttime, equatorial ionosphere -- are believed to be the source of large-scale instabilities that ultimately drive the detrimental scintillations.

For more information about C/NOFS, visit:
http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=2008-017A

Image (mentioned), Animation (mentioned), Graphic (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Karen C. Fox.

Greetings, Orbiter.ch

Soyuz Launches Human Research to the Space Station

ISS - International Space Station logo.

Dec. 15, 2015

International Space Station (ISS). Image Credit: NASA

The next crew members visiting the International Space Station (ISS), today launched aboard a Soyuz spacecraft, are packing multiple research investigations with them including three specifically focused on human health in space.

Determining the radiation doses inside the space station using various devices, measuring the impact of space travel on both the human immune system and an individual's microbiome, and studying the occurrence and indicators of airway inflammation in astronauts are the goals of these three investigations. This research will help highlight any health impacts to crew members’ well-being on long-duration missions, including on the journey to Mars where astronauts will need to be more self-sufficient in dealing with the extreme conditions of spaceflight.

Image above: To monitor microbial growth and ensure a safe and healthy environment on the International Space Station, crew members take regular samples of air, surfaces, and water to be analyzed. Scientists' main focus is still to prevent microbes on the station, rather than to remediate. Image Credit: NASA.

The Dose Distribution Inside the International Space Station – 3D (DOSIS-3D) investigation provides insight into combining different devices for radiation dosage monitoring, and provides lessons in how to monitor real-time radiation exposure data. This could prove beneficial to radiation monitoring for commercial and military airline crews, as well as other workers exposed to radiation.

Space station crew members are continually exposed to varying levels of radiation that can be harmful to their health, but it can be difficult to gain a complete picture of radiation within the space station. DOSIS-3D uses several active and passive detectors to determine the radiation doses inside the station. The goal is to create a three-dimensional radiation map covering all sections of the space station and a pinpoint of the distribution and levels of radiation inside the space station.

Image above: The Dose Distribution Inside the International Space Station - 3D (DOSIS-3D) Passive Detector Pack (PDP) was deployed in the Columbus European Laboratory during Expedition 39. A similar PDP will launch aboard the Soyuz spacecraft Dec. 15. Image Credit: NASA.

As part of the Microbiome investigation, scientists will assess the likelihood and consequences of alterations in the microbiome (the collection of microbes that live in and on the human body at any given time) and the related human health risk due to the extreme spaceflight environment. During a mission to space, astronauts are subject to many stressful conditions (g-forces, radiation, microgravity, anxiety, etc.) that can have a negative impact on their health. Several studies have demonstrated that space travel affects their immune systems, and have shown some evidence suggesting that changes in their microbiomes occur as well. Because the human microbiome plays a key role in human health, it is important to assess the effect of long-duration space exploration on the microbial population that inhabits the human body.

During the investigation, crew members will take periodic samples from different parts of their body and the surrounding space station environment to monitor the status of their microbiome and immune system and their interaction with the unique environment of the orbiting laboratory. Samples will also be collected from astronauts before and after their missions. These samples will help scientists determine how microgravity, the space station environment and diet affect their stress levels, immune system function and microbiome. The study will inform the design of therapies to mitigate any microbiome changes or related health issues identified during the investigation.

Image above: European Space Agency astronaut Samantha Cristoforetti on board the International Space Station working with equipment for the Airway Monitoring investigation. Image Credit: NASA.

Crew members may breathe easier thanks to another space station experiment set to launch on the Soyuz 45S. The Airway Monitoring investigation will study the occurrence and indicators of airway inflammation in astronauts resulting from dust particles in the orbiting vehicle. Scientists will use ultra-sensitive gas analyzers to measure nitric oxide exhaled by crewmembers. Monitoring these measurements will help highlight environmental conditions that exacerbate/alleviate airway inflammation in crewmembers and will help in the development of countermeasures to reduce the possibility of its occurrence. This, in turn, can help to optimize the health and performance of astronauts on long-duration exploration missions. Researchers hope to provide new insights in nitric oxide physiology, which could improve the diagnostic use of exhaled nitric oxide on Earth that could benefit patients with asthma or other airway inflammatory diseases.

From radiation to microbiome to respiratory research and more, the space station continues to conduct science off the Earth for the Earth and beyond.

Related links:

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

International Space Station – 3D (DOSIS-3D) investigation: http://www.nasa.gov/mission_pages/station/research/experiments/184.html

Microbiome investigation: http://www.nasa.gov/mission_pages/station/research/experiments/1010.html

Airway Monitoring investigation: http://www.nasa.gov/mission_pages/station/research/experiments/1172.html

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

Images (mentioned), Text, Credits: NASA’s Johnson Space Center/International Space Station Program Science Office/Andrea Dunn/ Jennifer Harbaugh.

Greetings, Orbiter.ch

NASA's Fermi Satellite Kicks Off a Blazar-detecting Bonanza

NASA - Fermi Gamma-ray Space Telescope logo.

Dec. 15, 2015

A long time ago in a galaxy half the universe away, a flood of high-energy gamma rays began its journey to Earth. When they arrived in April, NASA's Fermi Gamma-ray Space Telescope caught the outburst, which helped two ground-based gamma-ray observatories detect some of the highest-energy light ever seen from a galaxy so distant. The observations provide a surprising look into the environment near a supermassive black hole at the galaxy's center and offer a glimpse into the state of the cosmos 7 billion years ago.

Blazar Bonanza

Video above: Explore how gamma-ray telescopes in space and on Earth captured an outburst of high-energy light from PKS 1441+25, a black-hole-powered galaxy more than halfway across the universe. Video Credits: NASA's Goddard Space Flight Center.

"When we looked at all the data from this event, from gamma rays to radio, we realized the measurements told us something we didn't expect about how the black hole produced this energy," said Jonathan Biteau at the Nuclear Physics Institute of Orsay, France. He led the study of results from the Very Energetic Radiation Imaging Telescope Array System (VERITAS), a gamma-ray telescope in Arizona.

Astronomers had assumed that light at different energies came from regions at different distances from the black hole. Gamma rays, the highest-energy form of light, were thought to be produced closest to the black hole.

"Instead, the multiwavelength picture suggests that light at all wavelengths came from a single region located far away from the power source," Biteau explained. The observations place the area roughly five light-years from the black hole, which is greater than the distance between our sun and the nearest star.

The gamma rays came from a galaxy known as PKS 1441+25, a type of active galaxy called a blazar. Located toward the constellation Boötes, the galaxy is so far away its light takes 7.6 billion years to reach us. At its heart lies a monster black hole with a mass estimated at 70 million times the sun's and a surrounding disk of hot gas and dust. If placed at the center of our solar system, the black hole's event horizon -- the point beyond which nothing can escape -- would extend almost to the orbit of Mars.

As material in the disk falls toward the black hole, some of it forms dual particle jets that blast out of the disk in opposite directions at nearly the speed of light. Blazars are so bright in gamma rays because one jet points almost directly toward us, giving astronomers a view straight into the black hole's dynamic and poorly understood realm.

Image above: Black-hole-powered galaxies called blazars are the most common sources detected by NASA's Fermi Gamma-ray Space Telescope. As matter falls toward the supermassive black hole at the galaxy's center, some of it is accelerated outward at nearly the speed of light along jets pointed in opposite directions. When one of the jets happens to be aimed in the direction of Earth, as illustrated here, the galaxy appears especially bright and is classified as a blazar. Image Credits: M. Weiss/CfA.

In April, PKS 1441+25 underwent a major eruption. Luigi Pacciani at the Italian National Institute for Astrophysics in Rome was leading a project to catch blazar flares in their earliest stages in collaboration with the Major Atmospheric Gamma-ray Imaging Cerenkov experiment (MAGIC), located on La Palma in the Canary Islands. Using public Fermi data, Pacciani discovered the outburst and immediately alerted the astronomical community. Fermi's Large Area Telescope revealed gamma rays up to 33 billion electron volts (GeV), reaching into the highest-energy part of the instrument's detection range. For comparison, visible light has energies between about 2 and 3 electron volts.

"Detecting these very energetic gamma rays with Fermi, as well as seeing flaring at optical and X-ray energies with NASA's Swift satellite, made it clear that PKS 1441+25 had become a good target for MAGIC," Pacciani said.

Following up on the Fermi alert, the MAGIC team turned to the blazar and detected gamma rays with energies ranging from 40 to 250 GeV. "Because this galaxy is so far away, we didn't have a strong expectation of detecting gamma rays with energies this high," said Josefa Becerra Gonzalez, a researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who analyzed Fermi LAT data as part of the MAGIC study. "There are fewer and fewer gamma rays at progressively higher energies, and fewer still from very distant sources."

The reason distance matters for gamma rays is that they convert into particles when they collide with lower-energy light. The visible and ultraviolet light from stars shining throughout the history of the universe forms a remnant glow called the extragalactic background light (EBL). For gamma rays, this is a cosmic gauntlet they must pass through to be detected at Earth. When a gamma ray encounters starlight, it transforms into an electron and a positron and is lost to astronomers. The farther away the blazar is, the less likely its highest-energy gamma rays will survive to be detected.

Image above: More distant blazars show a loss of higher-energy gamma rays thanks to the extragalactic background light (EBL), a "cosmic fog" of visible and ultraviolet starlight that permeates the universe. From studies of nearby blazars, scientists know how many gamma rays should be emitted at different energies. If a gamma ray on its way to Earth collides with lower-energy light in the EBL, it converts into a pair of particles and is lost to astronomers. As shown by the graphs at left in this illustration, the more distant the blazar, the fewer high-energy gamma rays we can detect. During the April 2015 outburst of PKS 1441+25, MAGIC and VERITAS saw rare gamma rays exceeding 100 GeV that managed to survive a journey of 7.6 billion light-years. Image Credits: NASA's Goddard Space Flight Center.

Following the MAGIC discovery, VERITAS also detected gamma rays with energies approaching 200 GeV. Findings from both teams are detailed in papers published Dec. 15 in The Astrophysical Journal Letters.

PKS 1441+25 is one of only two such distant sources for which gamma rays with energies above 100 GeV have been observed. Its dramatic flare provides a powerful glimpse into the intensity of the EBL from near-infrared to near-ultraviolet wavelengths and suggests that galaxy surveys have identified most of the sources responsible for it.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

Related links:

Very Energetic Radiation Imaging Telescope Array System (VERITAS): http://veritas.sao.arizona.edu/

Major Atmospheric Gamma-ray Imaging Cerenkov experiment (MAGIC): https://magic.mpp.mpg.de/

DETECTION OF THE z = 0.940 BLAZAR PKS 1441+25 WITH MAGIC: http://iopscience.iop.org/article/10.1088/2041-8205/815/2/L23

For more information about NASA's Fermi, visit: http://www.nasa.gov/fermi

Images (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Francis Reddy/Ashley Morrow.

Best regards, Orbiter.ch

XXL Hunt for Galaxy Clusters

ESO - European Southern Observatory logo.

15 December 2015

Observations from ESO telescopes provide crucial third dimension in probe of Universe’s dark side

ESO telescopes have provided an international team of astronomers with the gift of the third dimension in a plus-sized hunt for the largest gravitationally bound structures in the Universe — galaxy clusters. Observations by the VLT and the NTT complement those from other observatories across the globe and in space as part of the XXL survey — one of the largest ever such quests for clusters.

Galaxy clusters are massive congregations of galaxies that host huge reservoirs of hot gas — the temperatures are so high that X-rays are produced. These structures are useful to astronomers because their construction is believed to be influenced by the Universe’s notoriously strange components — dark matter and dark energy. By studying their properties at different stages in the history of the Universe, galaxy clusters can shed light on the Universe’s poorly understood dark side.

The team, consisting of over 100 astronomers from around the world, started a hunt for the cosmic monsters in 2011. Although the high-energy X-ray radiation that reveals their location is absorbed by the Earth’s atmosphere, it can be detected by X-ray observatories in space. Thus, they combined an ESA XMM-Newton survey — the largest time allocation ever granted for this orbiting telescope — with observations from ESO and other observatories. The result is a huge and growing collection of data across the electromagnetic spectrum [1], collectively called the XXL survey.

X-ray image of the XXL-South Field

“The main goal of the XXL survey is to provide a well-defined sample of some 500 galaxy clusters out to a distance when the Universe was half its current age,” explains XXL principal investigator Marguerite Pierre of CEA,  Saclay, France.

The XMM-Newton telescope imaged two patches of sky — each one hundred times the area of the full Moon — in an attempt to discover a huge number of previously unknown galaxy clusters. The XXL survey team have now released their findings in a series of papers using the 100 brightest clusters discovered [2].

Observations from the EFOSC2 instrument installed on the New Technology Telescope (NTT), along with the FORS instrument attached to ESO’s Very Large Telescope (VLT), also were used to carefully analyse the light coming from galaxies within these galaxy clusters. Crucially, this allowed the team to measure the precise distances to the galaxy clusters, providing the three-dimensional view of the cosmos required to perform precise measurements of dark matter and dark energy [3].

Composite of X-ray and visible light views of a distant cluster of galaxies

The XXL survey is expected to produce many exciting and unexpected results, but even with one fifth of the final expected data, some surprising and important findings have already appeared.

One paper reports the discovery of five new superclusters — clusters of galaxy clusters — adding to those already known, such as our own, the Laniakea Supercluster.

Another reports followup observations of one particular galaxy cluster (informally known as XLSSC-116), located over six billion light-years away [4]. In this cluster unusually bright diffuse light was observed using MUSE on the VLT.

“This is the first time that we are able to study in detail the diffuse light in a distant galaxy cluster, illustrating the power of MUSE for such valuable studies,” explained co-author Christoph Adami of the Laboratoire d'Astrophysique, Marseille, France.

Visible light view of a distant galaxy cluster discovered in the XXL survey

The team have also used the data to confirm the idea that galaxy clusters in the past are scaled down versions of those we observe today — an important finding for the theoretical understanding of the evolution of clusters over the life of the Universe.

The simple act of counting galaxy clusters in the XXL data has also confirmed a strange earlier result  — there are fewer distant clusters than expected based on predictions from the cosmological parameters measured by ESA’s Planck telescope. The reason for this discrepancy is unknown, however the team hope to get to the bottom of this cosmological curiosity with the full sample of clusters in 2017.

These four important results are just a foretaste of what is to come in this massive survey of some of the most massive objects in the Universe.

Notes:

[1] The XXL survey has combined archival data as well as new observations of galaxy clusters covering the wavelength range from 1 × 10^—4 μm (X-ray, observed with XMM) to more than 1 metre (observed with the Giant Metrewave Radio Telescope [GMRT]).

[2] The galaxy clusters reported in the thirteen papers are found at redshifts between z = 0.05 and z = 1.05, which correspond to when the Universe was approximately 13 and 5.7 billion years old, respectively.

[3] Probing the galaxy clusters required their precise distances to be known. While approximate distances — photometric redshifts — can be measured by analysing their colours at different wavelengths, more accurate spectroscopic redshifts are needed. Spectroscopic redshifts were also sourced from archival data, as part of the VIMOS Public Extragalactic Redshift Survey (VIPERS), the VIMOS-VLT Deep Survey (VVDS) and the GAMA survey.

[4] This galaxy cluster was found to be at a redshift of z = 0.543.

More information:

A description of the survey, and some of the early science results, will be presented in a series of papers to appear in the journal Astronomy & Astrophysics on 15 December 2015.

A full listing of the XXL team can be found here: http://irfu.cea.fr/xxl/members

XXL is an international project based around an XMM Very Large Programme surveying two 25 square degrees extragalactic fields at a depth of ~5 × 10^–15 erg cm^—2 s^—1 in the [0.5—2] keV band for point-like sources. The XXL website is found here: http://irfu.cea.fr/xxl. Multi-band information and spectroscopic follow-up of the X-ray sources are obtained through a number of survey programmes is summarised here: http://xxlmultiwave.pbworks.com/

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

XXL Survey: http://irfu.cea.fr/xxl/

Scientific Papers in Astronomy & Astrophysics: http://www.aanda.org/component/toc/?task=topic&id=542

ESA XMM-Newton survey: http://sci.esa.int/xmm-newton/

EFOSC2 instrument: http://www.eso.org/public/teles-instr/lasilla/ntt/efosc2/

New Technology Telescope (NTT): http://www.eso.org/public/teles-instr/lasilla/ntt/

ESO’s Very Large Telescope (VLT): http://eso.org/paranal

FORS instrument: http://www.eso.org/public/teles-instr/vlt/vlt-instr/fors/

MUSE instrument: http://www.eso.org/public/teles-instr/vlt/vlt-instr/muse/

ESA’s Planck telescope: http://www.esa.int/Our_Activities/Space_Science/Planck

Giant Metrewave Radio Telescope (GMRT): http://gmrt.ncra.tifr.res.in/

VIMOS Public Extragalactic Redshift Survey (VIPERS): http://vipers.inaf.it/

VIMOS-VLT Deep Survey (VVDS): https://en.wikipedia.org/wiki/VIMOS-VLT_Deep_Survey

GAMA survey: http://www.gama-survey.org/

Images, Text, Credits: Credit: ESO/ESA/XMM-Newton/XXL survey consortium/(S. Snowden, L. Faccioli, F. Pacaud)/Canada France Hawaii Telescope.

Greetings, Orbiter.ch