Black hole winds pull the plug on star formation

ESA - Herschel Mission patch.

25 March 2015

Black-hole wind sweeping away galactic gas

Astronomers using ESA’s Herschel space observatory have found that the winds blowing from a huge black hole are sweeping away its host galaxy’s reservoir of raw star-building material.

Found at the hearts of most galaxies, supermassive black holes are extremely dense and compact objects with masses between millions and billions of times that of our Sun.

Many are relatively passive, like the one sitting at the centre of our Milky Way. However, some of them are devouring their surroundings with a great appetite.

Black-hole wind

These active black holes not only feed on nearby gas but also expel some of it as powerful winds and jets. Astronomers have long suspected these outflows to be responsible for draining galaxies of their interstellar gas, in particular the gas molecules from which stars are born.

This could eventually affect a galaxy’s star-forming activity, slowing it down or possibly quenching it entirely.

Until now, it had not been possible to capture a complete view of this process. While astronomers were able to detect winds very close to black holes using X-ray telescopes, and to trace much larger galactic outflows of gas molecules through infrared observations, they had not succeeded at finding both in the same galaxy.

A new study has changed the scene, detecting winds driven by one particular black hole from the smallest to largest scales. 

Host galaxy

“This is the first time that we have seen a supermassive black hole in action, blowing away the galaxy’s reservoir of star-making gas,” explains Francesco Tombesi from NASA’s Goddard Space Flight Center and the University of Maryland, USA, who led the research published this week in Nature.

Combining infrared observations from ESA’s Herschel space observatory with new data from the Japanese/US Suzaku X-ray satellite, the astronomers detected the winds close to the central black hole as well as their global effect in pushing galactic gas away in a galaxy known as IRAS F11119+3257.

The winds start small and fast, gusting at about 25% the speed of light near the black hole and blowing away about the equivalent of one solar mass of gas every year.

As they progress outwards, the winds slow but sweep up an additional few hundred solar masses of gas molecules per year and push it out of the galaxy.

Galactic outflow

This is the first solid proof that black-hole winds are stripping their host galaxies of gas by driving large-scale outflows.

The new finding supports the view that black holes might ultimately stop stars forming in their host galaxies.

“Herschel has already revolutionised our understanding of how stars are born. This new result is now helping us understand why and how star formation in some galaxies can be globally affected and even switched off entirely,” says Göran Pilbratt, Herschel Project Scientist at ESA.

“The culprit of this cosmic ‘whodunnit’ has been found. As many suspected, a central black hole can power large-scale gas outflows, quenching the formation of stars.”  

Read more about this discovery: http://sci.esa.int/herschel/55628

More information:

“Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy,” by F. Tombesi, et al., is published in the 26 March 2015 issue of the journal Nature: http://www.nature.com/nature/journal/v519/n7544/full/nature14261.html

The study is based on observations performed with the Photoconductor Array Camera and Spectrometer (PACS) instrument on ESA’s Herschel space observatory, as well as on data from the Japanese/US Suzaku mission.

Related links:

Herschel: ESA's giant infrared observatory: http://www.esa.int/Our_Activities/Space_Science/Herschel

More about...:

Herschel overview: http://www.esa.int/Our_Activities/Space_Science/Herschel_overview

Online Showcase of Herschel Images OSHI: http://oshi.esa.int/

In depth:

This article in depth: http://sci.esa.int/herschel/55628

Herschel in depth: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=16

Herschel Science Centre: http://herschel.esac.esa.int/

Images, Text, Credits: ESA/ATG medialab/NASA/SDSS/S. Veilleux.

Best regards, Orbiter.ch

Cluster satellite catches up

ESA - Cluster II Mission patch.

25 March 2015

One of the four Cluster satellites has shifted its orbit to ensure a safe reentry when the time comes, as well as providing a rare opportunity to study how a satellite’s exhaust plume interacts with the solar wind.

ESA’s Cluster quartet, in orbit since 2000, is studying the detailed structures of Earth’s magnetosphere – our protective magnetic bubble – and its environment in 3D.

Cluster quartet

The identical satellites fly in highly elliptical orbits between 6 km and 20 000 km apart, depending on the regions that each satellite’s set of 11 identical instruments is studying.

With their current paths, three will safely reenter the atmosphere between 2024 and 2026, tugged down to a planned destruction by gravity and atmospheric drag once their fuel is exhausted.

But after 15 years of complex manoeuvring that has enabled the fleet to gather valuable data in three dimensions, Cluster-1 ended up in a rather different orbit – leaving it to reenter much later than the others. 

Planning safe reentry

“The delayed reentry exposed it to additional perturbations and undesired natural variations in its orbit, meaning that it might have reentered over the northern hemisphere, where population densities are high,” says Detlef Sieg, a flight dynamics specialist at ESA’s Space Operations Centre, ESOC, in Darmstadt, Germany.

“By performing a thruster burn now, we could bring forward its reentry date to match those of the other satellites and plan for a future safe descent over the much less populated southern hemisphere.”

Monitoring signals

The sequence of three thruster burns was carried out by the team at ESOC on 9, 17 and 25 March. These will maintain Cluster-1’s orbital position relative to the other satellites, while shifting the angle of its orbit (see Orbital inclination: https://en.wikipedia.org/wiki/Orbital_inclination) and make the orbit a little more elliptical.

“The Sun and the Moon will now affect its orbit over the next decade such that the minimum altitude in 2025, after the mission’s science gathering ends, will finally become low enough for the atmosphere to capture it and cause it to burn up safely,” says Detlef.

Largest firing in eight years

The 17 March firing – the largest in eight years for Cluster – was the largest of the three burns, and two aspects made it particularly challenging.

There was uncertainty as to the amount of fuel left in the tanks, and the satellite’s orientation with respect to the Sun was close to the safe operating limit.

“If we weren’t careful, one of the instruments attached to a boom would start shadowing the solar arrays, potentially affecting power generation, which is always a critical issue for any satellite,” notes Spacecraft Operations Manager Bruno Sousa.

Mission team watches closely

Even though the thrusters performed flawlessly, the team spent an anxious 20 minutes watching to see that the Sun angle remained within limits.

“It changed slightly faster than we had predicted in the undesired direction, but at the end it remained under the limit by 0.1º. Nonetheless, we had a finger on the ‘abort’ button throughout,” says Bruno.

Rare chance for unique science

In addition, the flight control team were asked to perform the burns while some science observations continued.

“We also conducted an experiment,” says Philippe Escoubet, Cluster Project Scientist, “suggested by one of our recently selected guest investigators, collecting electric and magnetic data during the thruster firing.

“The measurements will be used to study the interaction between the cloud of gas generated by the thrusters and the solar wind, the plasma emitted by the Sun.”

Related links:

Exploring the Sun-Earth connection: http://www.esa.int/Our_Activities/Space_Science/Cluster

Cluster overview: http://www.esa.int/Our_Activities/Space_Science/Cluster_overview2

ESA Operations Centre: http://www.esa.int/Our_Activities/Operations

Images, Text, Credit: ESA.

Greetings, Orbiter.ch

NASA's Curiosity Rover Finds Biologically Useful Nitrogen on Mars

NASA - Mars Science Laboratory (MSL) logo.

March 24, 2015

A team using the Sample Analysis at Mars (SAM) instrument suite aboard NASA's Curiosity rover has made the first detection of nitrogen on the surface of Mars from release during heating of Martian sediments. The nitrogen was detected in the form of nitric oxide, and could be released from the breakdown of nitrates during heating. Nitrates are a class of molecules that contain nitrogen in a form that can be used by living organisms. The discovery adds to the evidence that ancient Mars was habitable for life.

Image above: This self-portrait of NASA's Mars rover Curiosity combines dozens of exposures taken by the rover's Mars Hand Lens Imager on Feb. 3, 2013 plus three exposures taken May 10, 2013 to show two holes (in lower left quadrant) where Curiosity used its drill on the rock target "John Klein". Image Credit: NASA/JPL-Caltech/MSSS.

Nitrogen is essential for all known forms of life, since it is used in the building blocks of larger molecules like DNA and RNA, which encode the genetic instructions for life, and proteins, which are used to build structures like hair and nails, and to speed up or regulate chemical reactions.

However, on Earth and Mars, atmospheric nitrogen is locked up as nitrogen gas (N2) – two atoms of nitrogen bound together so strongly that they do not react easily with other molecules. The nitrogen atoms have to be separated or "fixed" so they can participate in the chemical reactions needed for life. On Earth, certain organisms are capable of fixing atmospheric nitrogen and this process is critical for metabolic activity. However, smaller amounts of nitrogen are also fixed by energetic events like lightning strikes.

Nitrate (NO3) – a nitrogen atom bound to three oxygen atoms – is a source of fixed nitrogen. A nitrate molecule can join with various other atoms and molecules; this class of molecules is known as nitrates.

There is no evidence to suggest that the fixed nitrogen molecules found by the team were created by life. The surface of Mars is inhospitable for known forms of life. Instead, the team thinks the nitrates are ancient, and likely came from non-biological processes like meteorite impacts and lightning in Mars' distant past.

Features resembling dry riverbeds and the discovery of minerals that only form in the presence of liquid water suggest that Mars was more hospitable in the remote past. The Curiosity team has found evidence that other ingredients needed for life, such as liquid water and organic matter, were present on Mars at the Curiosity site in Gale Crater billions of years ago.

Mars Has Ways to Make Organics Hard to Find

Image above: This illustration portrays some of the reasons why finding organic chemicals on Mars is challenging. Whatever organic chemicals may be produced on Mars or delivered to Mars face several possible modes of being transformed or destroyed. Organic chemicals are molecular building block of life, although they can be made without the presence of life. Whether or not organic chemicals are produced by processes on Mars, some are delivered to the planet aboard meteorites and dust from asteroids and comets. Image credit: NASA/JPL-Caltech.

"Finding a biochemically accessible form of nitrogen is more support for the ancient Martian environment at Gale Crater being habitable," said Jennifer Stern of NASA's Goddard Space Flight Center in Greenbelt, Maryland. Stern is lead author of a paper on this research published online in the Proceedings of the National Academy of Science March 23.

The team found evidence for nitrates in scooped samples of windblown sand and dust at the "Rocknest" site, and in samples drilled from mudstone at the "John Klein" and "Cumberland" drill sites in Yellowknife Bay. Since the Rocknest sample is a combination of dust blown in from distant regions on Mars and more locally sourced materials, the nitrates are likely to be widespread across Mars, according to Stern. The results support the equivalent of up to 1,100 parts per million nitrates in the Martian soil from the drill sites. The team thinks the mudstone at Yellowknife Bay formed from sediment deposited at the bottom of a lake. Previously the rover team described the evidence for an ancient, habitable environment there: fresh water, key chemical elements required by life, such as carbon, and potential energy sources to drive metabolism in simple organisms.

The samples were first heated to release molecules bound to the Martian soil, then portions of the gases released were diverted to the SAM instruments for analysis. Various nitrogen-bearing compounds were identified with two instruments: a mass spectrometer, which uses electric fields to identify molecules by their signature masses, and a gas chromatograph, which separates molecules based on the time they take to travel through a small glass capillary tube -- certain molecules interact with the sides of the tube more readily and thus travel more slowly.

Along with other nitrogen compounds, the instruments detected nitric oxide (NO -- one atom of nitrogen bound to an oxygen atom) in samples from all three sites. Since nitrate is a nitrogen atom bound to three oxygen atoms, the team thinks most of the NO likely came from nitrate which decomposed as the samples were heated for analysis. Certain compounds in the SAM instrument can also release nitrogen as samples are heated; however, the amount of NO found is more than twice what could be produced by SAM in the most extreme and unrealistic scenario, according to Stern. This leads the team to think that nitrates really are present on Mars, and the abundance estimates reported have been adjusted to reflect this potential additional source.

"Scientists have long thought that nitrates would be produced on Mars from the energy released in meteorite impacts, and the amounts we found agree well with estimates from this process," said Stern.

The SAM instrument suite was built at NASA Goddard with significant elements provided by industry, university, and national and international NASA partners. NASA's Mars Science Laboratory Project is using Curiosity to assess ancient habitable environments and major changes in Martian environmental conditions. NASA's Jet Propulsion Laboratory in Pasadena, California, a division of Caltech, built the rover and manages the project for NASA's Science Mission Directorate in Washington. The NASA Mars Exploration Program and Goddard Space Flight Center provided support for the development and operation of SAM. SAM-Gas Chromatograph was supported by funds from the French Space Agency (CNES). Data from these SAM experiments are archived in the Planetary Data System: http://pds.nasa.gov/

For more information about Curiosity or Mars Science Laboratory (MSL), visit: http://www.nasa.gov/mission_pages/msl/ and http://mars.jpl.nasa.gov/msl/

Images (mentioned), Text, Credits: NASA Goddard Space Flight Center / Nancy Neal-Jones / William Steigerwald.

Greetings, Orbiter.ch

NASA Reformats Memory of Longest-Running Mars Rover

NASA - Mars Exploration Rover B (MER-B) "Opportunity" patch.

March 24, 2015

Fast Facts:

- The rover team reformatted the aging rover's flash memory to restore use of overnight data storage

- Opportunity completed inspections of blocky rocks above Marathon Valley

- The rover is nearing the equivalent of a marathon in total driving distance

After avoiding use of the rover's flash memory for three months, the team operating NASA's 11-year-old Mars Exploration Rover Opportunity has reformatted the vehicle's flash memory banks and resumed storing some data overnight for transmitting later.

Mars 'Marathon Valley' Overlook

Image above: This view from NASA's Opportunity Mars rover shows part of "Marathon Valley," a destination on the western rim of Endeavour Crater, as seen from an overlook north of the valley. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

The team received confirmation from Mars on March 20 that the reformatting completed successfully. The rover switched to updated software earlier this month that will avoid using one of the seven banks of onboard flash memory. Some of the flash-memory problems that prompted the team to adopt a no-flash mode of operations in late 2014 were traced to Bank 7. The remaining six banks provide more nonvolatile memory capacity than the rover has used on all but a few days since landing on Mars in January 2004.

Mars 'Marathon Valley' Overlook (False Color)

Image above: This view from NASA's Opportunity Mars rover shows part of "Marathon Valley" as seen from an overlook north of the valley. It was taken by the rover's Pancam on March 13, 2015. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

In the no-flash mode of operations, Opportunity continued conducting science investigations and driving, but transmitted each day's accumulated data before powering down for overnight conservation of energy. Flash memory is nonvolatile, meaning it retains data even without power. Opportunity also uses random access memory, which retains data only while power is on.

Last week, Opportunity completed examination of unusual rocks it found at an overlook to its "Marathon Valley" science destination. The rover is approaching an elongated crater called "Spirit of St. Louis" on the path to Marathon Valley. As of March 23, Opportunity has 47 yards (43 meters) remaining to drive before its odometry passes the distance of an Olympic marathon race.

Mars 'Marathon Valley' Overlook, in Stereo

Image above: This stereo scene from NASA's Opportunity Mars rover shows part of "Marathon Valley" as seen from an overlook north of the valley on March 13, 2015.

"Opportunity can work productively without use of flash memory, as we have shown for the past three months, but with flash we have more flexibility for operations," said Opportunity Project Manager John Callas of NASA's Jet Propulsion Laboratory, Pasadena, California. "The rover can collect more data than can be returned to Earth on any one day. The flash memory allows data from intensive science activities to be returned over several days."

Rover's Progress Toward Mars Marathon, Sol 3966

Image above: This map updates progress that NASA's Mars Exploration Rover Opportunity is making toward reaching a driving distance equivalent to a marathon footrace. Image Credit: NASA/JPL-Caltech/Univ. of Arizona.

Marathon Valley was selected as a science destination because spectrometer observations from orbit indicate exposures of clay minerals. Before entering the valley, Opportunity will observe Spirit of St. Louis Crater, which holds an interior rock structure rising higher than the crater rim.

Mars Exploration Rover B (MER-B) "Opportunity". Image Credits: NASA/JPL-Caltech

As of March 16, Opportunity has driven 26.192 miles (42.152 kilometers) since it landed on Mars in January 2004. A marathon is 26.219 miles (42.195 kilometers).

Image above: This illustration depicts some highlights along the route as NASA's Mars Exploration Rover Opportunity drove as far as a marathon race during the first 11 years and two months after its January 2004 landing in Eagle Crater. The vehicle surpassed marathon distance of 26.219 miles (42.195 kilometers) with a drive completed on March 24, 2015, during the 3,968th Martian day, or sol, of Opportunity's work on Mars. For this map, north is on the left. Image Credit: NASA/JPL-Caltech/Cornell Univ./USGS/Arizona State Univ.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for NASA's Science Mission Directorate in Washington. For more information about Spirit and Opportunity, visit: http://www.nasa.gov/rovers and http://marsrovers.jpl.nasa.gov

You can follow the project on Twitter and on Facebook at: http://twitter.com/MarsRovers and http://www.facebook.com/mars.rovers

Images (mentioned), Text, Credits: NASA/JPL/Guy Webster.

Best regards, Orbiter.ch

NASA Satellites Catch 'Growth Spurt' from Newborn Protostar

NASA - Spitzer Space Telescope patch.

March 23, 2015

Using data from orbiting observatories, including NASA's Spitzer Space Telescope, and ground-based facilities, an international team of astronomers has discovered an outburst from a star thought to be in the earliest phase of its development. The eruption, scientists say, reveals a sudden accumulation of gas and dust by an exceptionally young protostar known as HOPS 383.

Stars form within collapsing fragments of cold gas clouds. As the cloud contracts under its own gravity, its central region becomes denser and hotter. By the end of this process, the collapsing fragment has transformed into a hot central protostar surrounded by a dusty disk roughly equal in mass, embedded in a dense envelope of gas and dust. Astronomers call this a "Class 0" protostar.

"HOPS 383 is the first outburst we've ever seen from a Class 0 object, and it appears to be the youngest protostellar eruption ever recorded," said William Fischer, a NASA Postdoctoral Program Fellow at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Images above: Infrared images from instruments at Kitt Peak National Observatory (KPNO, left) and NASA's Spitzer Space Telescope document the outburst of HOPS 383, a young protostar in the Orion star-formation complex. Background: A wide view of the region taken from a Spitzer four-color infrared mosaic. Image Credit: E. Safron et al.; Background: NASA/JPL/T. Megeath (U-Toledo).

The Class 0 phase is short-lived, lasting roughly 150,000 years, and is considered the earliest developmental stage for stars like the sun.

A protostar has not yet developed the energy-generating capabilities of a sun-like star, which fuses hydrogen into helium in its core. Instead, a protostar shines from the heat energy released by its contraction and by the accumulation of material from the disk of gas and dust surrounding it. The disk may one day develop asteroids, comets and planets.

Because these infant suns are thickly swaddled in gas and dust, their visible light cannot escape. But the light warms dust around the protostar, which reradiates the energy in the form of heat detectable by infrared-sensitive instruments on ground-based telescopes and orbiting satellites.

HOPS 383 is located near NGC 1977, a nebula in the constellation Orion and a part of its sprawling star-formation complex. Located about 1,400 light-years away, the region constitutes the most active nearby "star factory" and hosts a treasure trove of young stellar objects still embedded in their natal clouds.

A team led by Thomas Megeath at the University of Toledo in Ohio used Spitzer to identify more than 300 protostars in the Orion complex. A follow-on project using the European Space Agency's Herschel Space Observatory, called the Herschel Orion Protostar Survey (HOPS), studied many of these objects in greater detail.

The eruption of HOPS 383 was first recognized in 2014 by astronomer Emily Safron shortly after her graduation from the University of Toledo. Under the supervision of Megeath and Fischer, she had just completed her senior thesis comparing the decade-old Spitzer Orion survey with 2010 observations from NASA's Wide-field Infrared Survey Explorer (WISE) satellite. Using software to analyze the data, Safron had already run through it several times without finding anything new. But with her thesis completed and graduation behind her, she decided to take the extra time to compare images of the "funny objects" by eye.

That's when she noticed HOPS 383's dramatic change. "This beautiful outburst was lurking in our sample the whole time," Safron said.

Safron's catalog of observations included Spitzer data at wavelengths of 3.6, 4.5 and 24 microns and WISE data at 3.4, 4.6 and 22 microns. HOPS 383 is so deeply enshrouded in dust that it wasn't seen at all before the outburst at the shortest Spitzer wavelength, and an oversight in a version of the catalog produced before Safron's involvement masked the increase at the longest wavelengths. As a result, her software saw a rise in brightness in only one wavelength out of three, which failed to meet her criteria for the changes she was hoping to find.

Once they realized what had happened, Safron, Fischer and their colleagues gathered additional Spitzer data, Herschel observations, and images from ground-based infrared telescopes at the Kitt Peak National Observatory in Arizona and the Atacama Pathfinder Experiment in northern Chile. Their findings were published in the Feb. 10 edition of The Astrophysical Journal.

Artist's view of the Spitzer Space Telescope. Image Credit: NASA

The first hint of brightening appears in Spitzer data from 2006. By 2008, they write, HOPS 383's brightness at a wavelength of 24 microns had increased by 35 times. According to the most recent data available, from 2012, the eruption shows no sign of abating.

"An outburst lasting this long rules out many possibilities, and we think HOPS 383 is best explained by a sudden increase in the amount of gas the protostar is accreting from the disk around it," explained Fischer.

Scientists suspect that instabilities in the disk lead to episodes where large quantities of material flow onto the central protostar. The star develops an extreme hot spot at the impact point, which in turn heats up the disk, and both brighten dramatically.

The team continues to monitor HOPS 383 and has proposed new observations using NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA), the world's largest flying telescope.

For more information about NASA's Spitzer Space Telescope, visit: http://www.spitzer.caltech.edu/

Related Links:

Paper: HOPS 383: An Outbursting Class 0 Protostar In Orion: http://iopscience.iop.org/2041-8205/800/1/L5

Stars Adorn Orion's Sword (05.26.2011): http://orbiterchspacenews.blogspot.ch/2011/10/stars-adorn-orions-sword.html

In McNeil's Nebula, a Young Star Flaunts its X-ray Spots (07.03.2012): http://www.nasa.gov/topics/universe/features/xray-flaunt.html

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

Greetings, Orbiter.ch

Colliding Stars Explain Enigmatic Seventeenth Century Explosion

ESO - European Southern Observatory logo.

23 March 2015

APEX observations help unravel mystery of Nova Vulpeculae 1670

The nova of 1670 recorded by Hevelius

New observations made with APEX and other telescopes reveal that the star that European astronomers saw appear in the sky in 1670 was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later. The results appear online in the journal Nature on 23 March 2015.

Some of seventeenth century’s greatest astronomers, including Hevelius — the father of lunar cartography — and Cassini, carefully documented the appearance of a new star in the skies in 1670. Hevelius described it as nova sub capite Cygni — a new star below the head of the Swan — but astronomers now know it by the name Nova Vulpeculae 1670 [1]. Historical accounts of novae are rare and of great interest to modern astronomers. Nova Vul 1670 is claimed to be both the oldest recorded nova and the faintest nova when later recovered.

The remnant of the nova of 1670 seen with modern instruments

The lead author of the new study, Tomasz Kaminski (ESO and the Max Planck Institute for Radio Astronomy, Bonn, Germany) explains: “For many years this object was thought to be a nova, but the more it was studied the less it looked like an ordinary nova — or indeed any other kind of exploding star.”

When it first appeared, Nova Vul 1670 was easily visible with the naked eye and varied in brightness over the course of two years. It then disappeared and reappeared twice before vanishing for good. Although well documented for its time, the intrepid astronomers of the day lacked the equipment needed to solve the riddle of the apparent nova’s peculiar performance.

The position of Nova Vul 1670 in the constellation of Vulpecula

During the twentieth century, astronomers came to understand that most novae could be explained by the runaway explosive behaviour of close binary stars. But Nova Vul 1670 did not fit this model well at all and remained a mystery.

Even with ever-increasing telescopic power, the event was believed for a long time to have left no trace, and it was not until the 1980s that a team of astronomers detected a faint nebula surrounding the suspected location of what was left of the star. While these observations offered a tantalising link to the sighting of 1670, they failed to shed any new light on the true nature of the event witnessed over the skies of Europe over three hundred years ago.

Wide-field view of the sky around Nova Vul 1670

Tomasz Kaminski continues the story: “We have now probed the area with submillimetre and radio wavelengths. We have found that the surroundings of the remnant are bathed in a cool gas rich in molecules, with a very unusual chemical composition.”

As well as APEX, the team also used the Submillimeter Array (SMA) and the Effelsberg radio telescope to discover the chemical composition and measure the ratios of different isotopes in the gas. Together, this created an extremely detailed account of the makeup of the area, which allowed an evaluation of where this material might have come from.

What the team discovered was that the mass of the cool material was too great to be the product of a nova explosion, and in addition the isotope ratios the team measured around Nova Vul 1670 were different to those expected from a nova. But if it wasn’t a nova, then what was it?

Zooming in on the location of Nova Vul 1670 in the constellation of Vulpecula

The answer is a spectacular collision between two stars, more brilliant than a nova, but less so than a supernova, which produces something called a red transient. These are a very rare events in which stars explode due to a merger with another star, spewing material from the stellar interiors into space, eventually leaving behind only a faint remnant embedded in a cool environment, rich in molecules and dust. This newly recognised class of eruptive stars fits the profile of Nova Vul 1670 almost exactly.

Co-author Karl Menten (Max Planck Institute for Radio Astronomy, Bonn, Germany) concludes: “This kind of discovery is the most fun: something that is completely unexpected!”

Notes:

[1] This object lies within the boundaries of the modern constellation of Vulpecula (The Fox), just across the border from Cygnus (The Swan). It is also often referred to as Nova Vul 1670 and CK Vulpeculae, its designation as a variable star.

More information:

This research was presented in a paper entitled “Nuclear ashes and outflow in the oldest known eruptive star Nova Vul 1670” by T. Kaminski et al., to appear online in the journal Nature on 23 March 2015.

The team is composed of Tomasz Kaminski (ESO, Santiago, Chile; Max Planck Institute for Radio Astronomy, Bonn, Germany [MPIfR]), Karl M. Menten (MPIfR), Romuald Tylenda (N. Copernicus Astronomical Center, Torun, Poland), Marcin Hajduk (N. Copernicus Astronomical Center), Nimesh A. Patel (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA) and Alexander Kraus (MPIfR).

APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. Operation of APEX at Chajnantor is entrusted to ESO.

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 Nature: http://www.eso.org/public/archives/releases/sciencepapers/eso1511/eso1511a.pdf

Photos of APEX: http://www.eso.org/public/images/archive/search/?adv=&subject_name=Atacama%20Pathfinder%20Experiment

Images, Text, Credits: ESO/Royal Society/T. Kaminski/IAU, and Sky & Telescope/Digitized Sky Survey 2. Acknowledgement: Davide De Martin/Video: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org) Acknowledgement: Davide De MartinMusic: Johan B. Monell (www.johanmonell.com).

Greetings, Orbiter.ch

Slight surface movements on the radar

ESA - Sentinel-1 Mission logo.

23 March 2015

Scientists are making advances in the use of satellite radar data – such as those from the Sentinel-1 mission – to monitor Earth’s changing surface.

Italy’s Phlegraean Fields – or Campi Flegrei – is a large, active volcanic area near the city of Naples near Mount Vesuvius. Since the 1970s, the ground has been rising owing to the volcanic nature of this area.

Campi Flegrei monitored by Sentinel-1

“In 2012, deformation rates up to 3 cm a month prompted the Italian Civil Protection Department to move from the base (green) alert level of the Campi Flegrei Emergency Plan to the attention (yellow) level,” said Sven Borgstrom from Italy’s National Institute for Geophysics and Volcanology.

“The uplift continues today: radar imagery from the Sentinel-1A satellite captured over the area between October 2014 and March 2015 show that the ground is rising by about 0.5 cm per month.”

This is just one of the many findings being presented this week at the Fringe Workshop on advances in the science and applications of ‘SAR interferometry’ held at ESRIN, ESA’s centre for Earth observation, in Frascati, Italy.

Vestfonna and Austfonna shedding ice

Interferometric Synthetic Aperture Radar, or InSAR, is a remote sensing technique where two or more images of the same area are combined to detect slight changes occurring between acquisitions.

Tiny changes on the ground cause changes in the radar signal and lead to rainbow-coloured interference patterns in the combined image, known as an ‘interferogram’.

The Fringe Workshop takes its name from these coloured fringes seen in the interferograms.

2015 Fringe Workshop

Small movements – down to a scale of a few millimetres – can be detected across wide areas. Tectonic plates grinding past one another, the slow ‘breathing’ of active volcanoes, the slight sagging of a city street through groundwater extraction, and even the thermal expansion of a building on a sunny day.

This year, the workshop is paying particular attention to new results from the Sentinel-1 mission. Launched in April of last year, Sentinel-1A became the first satellite in orbit for Europe’s Copernicus programme, and has been delivering important data for an array of operational and scientific applications.

Sentinel-1

In Norway’s Svalbard archipelago, Sentinel-1 data are being used to monitor ice loss from the Austfonna ice cap. Earlier this year, the satellite captured the ice cap’s outlet glacier flowing at 3 cm per day.

 Monitoring volcanoes with radar satellites

With over 420 participants, this year’s Fringe workshop has seen the largest turnout since its inauguration in 1991 – when four specialists met to discuss the early InSAR results from the ERS-1 mission. Radar interferometry has come a long way since, with contributions from satellites such as Envisat and now Sentinel-1A.

Related links:

2015 Fringe Workshop: http://seom.esa.int/fringe2015/index.php

National Institute for Geophysics and Volcanology: http://www.ingv.it/it/

Copernicus: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Overview3

Sentinel-1: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1

Images, Video, Text, Credits: ESA/Copernicus data (2015)/ESA/DLR Microwaves and Radar Institute/INGV/e-GEOS/GFZ–SEOM INSARAP study.

Greetings, Orbiter.ch