Tuesday, January 31, 2017

New Planet Imager Delivers First Science

The vortex mask shown at left is made out of synthetic diamond. Viewed with an scanning electron microscope, right, the "vortex" microstructure of the mask is revealed. Image credit: University of Liège/Uppsala University. › Larger view

This image shows the dusty disk of planetary material surrounding the young star HD 141569, located 380 light-years away from Earth. 
Image credit: NASA/JPL-Caltech

This image shows brown dwarf HIP 79124 B, located 23 times as far from its host star as Earth is from the sun. 
Image credit: NASA/JPL-Caltech 


A new device on the W.M. Keck Observatory in Hawaii has delivered its first images, showing a ring of planet-forming dust around a star, and separately, a cool, star-like body, called a brown dwarf, lying near its companion star.

The device, called a vortex coronagraph, was recently installed inside NIRC2 (Near Infrared Camera 2), the workhorse infrared imaging camera at Keck. It has the potential to image planetary systems and brown dwarfs closer to their host stars than any other instrument in the world.

"The vortex coronagraph allows us to peer into the regions around stars where giant planets like Jupiter and Saturn supposedly form," said Dmitri Mawet, research scientist at NASA's Jet Propulsion Laboratory and Caltech, both in Pasadena. "Before now, we were only able to image gas giants that are born much farther out. With the vortex, we will be able to see planets orbiting as close to their stars as Jupiter is to our sun, or about two to three times closer than what was possible before."

The new vortex results are presented in two papers, both published in the January 2017 issue of The Astronomical Journal. One study, led by Gene Serabyn of JPL, the overall lead of the Keck vortex project, presents the first direct image of the brown dwarf called HIP79124 B. This brown dwarf is located 23 astronomical units from a star (an astronomical unit is the distance between our sun and Earth) in a nearby star-forming region called Scorpius-Centaurus.

"The ability to see very close to stars also allows us to search for planets around more distant stars, where the planets and stars would appear closer together. Having the ability to survey distant stars for planets is important for catching planets still forming," said Serabyn. He also led a team that tested a predecessor of the vortex device on the Hale Telescope at Caltech's Palomar Observatory, near San Diego. In 2010, the team secured high-contrast images of three planets orbiting in the distant reaches of the star system called HR8799.

The second vortex study, led by Mawet, presents an image of the innermost of three rings of dusty, planet-forming material around the young star called HD141569A. The results, when combined with infrared data from NASA's Spitzer and WISE missions, and the European Space Agency's Herschel mission, reveal that the star's planet-forming material is made up of pebble-size grains of olivine, one of the most abundant silicates in Earth's mantle. The data also show that the temperature of the innermost ring imaged by the vortex is about minus 280 degrees Fahrenheit (100 Kelvin, or minus 173 degrees Celsius), a bit warmer than our asteroid belt.

"The three rings around this young star are nested like Russian dolls and undergoing dramatic changes reminiscent of planetary formation," said Mawet. "We have shown that silicate grains have agglomerated into pebbles, which are the building blocks of planet embryos."

About the vortex coronagraph

The vortex was invented in 2005 by Mawet while he was at the University of Liege in Belgium. The Keck vortex coronagraph was built by a combination of the University of Liege, Uppsala University in Sweden, JPL and Caltech.

The first science images and results from the vortex instrument demonstrate its ability to image planet-forming regions hidden under the glare of stars. Stars outshine planets by a factor of few thousand to a few billion, making the dim light of planets very difficult to see, especially for planets that lie close to their stars. To deal with this challenge, researchers have invented Instruments called coronagraphs, which typically use tiny masks to block the starlight, much like blocking the bright sun with your hand or a car visor to see better.

What makes the vortex coronagraph unique is that it does not block the starlight with a mask, but instead redirects light away from the detectors using a technique in which light waves are combined and canceled out. Because the vortex doesn't require an occulting mask, it has the advantage of taking images of regions closer to stars than other coronagraphs. Mawet likens the process to the eye of a storm.

"The instrument is called a vortex coronagraph because the starlight is centered on an optical singularity, which creates a dark hole at the location of the image of the star," said Mawet. "Hurricanes have a singularity at their centers where the wind speeds drop to zero -- the eye of the storm. Our vortex coronagraph is basically the eye of an optical storm where we send the starlight."

What's next for the vortex

In the future, the vortex will look at many more young planetary systems, in particular planets near the "frost lines," which are the region around a star where temperatures are cold enough for volatile molecules, such as water, methane and carbon dioxide, to condense into solid icy grains. The frost line is thought to divide a solar system into regions where planets are likely to become rocky or gas giants. Surveys of the frost line region by the vortex coronagraph will help answer ongoing puzzles about a class of hot, giant planets found extremely close to their stars -- the "hot Jupiters," and "hot Neptunes." Did these planets first form close to the frost line and migrate in, or did they form right next to their stars? "With a bit of luck, we might catch planets in the process of migrating through the planet-forming disk, by looking at these very young objects," Mawet said.

"The power of the vortex lies in its ability to image planets very close to their star, something that we can't do for Earth-like planets yet," said Serabyn. "The vortex coronagraph may be key to taking the first images of a pale blue dot like our own."

The Keck Observatory is managed by Caltech and the University of California. In 1996, NASA joined as a one-sixth partner in the Keck Observatory. JPL is managed by Caltech for NASA.


News Media Contact

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425

elizabeth.landau@jpl.nasa.gov

Whitney Clavin
Caltech, Pasadena, Calif.
626-395-1856

wclavin@caltech.edu

Written by Whitney Clavin


Source:  JPL-Caltech

NASA's Fermi Sees Gamma Rays from 'Hidden' Solar Flares

An international science team says NASA's Fermi Gamma-ray Space Telescope has observed high-energy light from solar eruptions located on the far side of the sun, which should block direct light from these events. This apparent paradox is providing solar scientists with a unique tool for exploring how charged particles are accelerated to nearly the speed of light and move across the sun during solar flares.

"Fermi is seeing gamma rays from the side of the sun we're facing, but the emission is produced by streams of particles blasted out of solar flares on the far side of the sun," said Nicola Omodei, a researcher at Stanford University in California. "These particles must travel some 300,000 miles within about five minutes of the eruption to produce this light."

Omodei presented the findings on Monday, Jan. 30, at the American Physical Society meeting in Washington, and a paper describing the results will be published online in The Astrophysical Journal on Jan. 31.


On three occasions, NASA's Fermi Gamma-ray Space Telescope has detected gamma rays from solar storms on the far side of the sun, emission the Earth-orbiting satellite shouldn't be able to detect. Particles accelerated by these eruptions somehow reach around to produce a gamma-ray glow on the side of the sun facing Earth and Fermi. Watch to learn more. Credits: NASA's Goddard Space Flight Center/Scott Wiessinger, producer.
Download this video in HD formats from NASA Goddard's Scientific Visualization Studio

Fermi has doubled the number of these rare events, called behind-the-limb flares, since it began scanning the sky in 2008. Its Large Area Telescope (LAT) has captured gamma rays with energies reaching 3 billion electron volts, some 30 times greater than the most energetic light previously associated with these "hidden" flares.

Thanks to NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft, which were monitoring the solar far side when the eruptions occurred, the Fermi events mark the first time scientists have direct imaging of beyond-the-limb solar flares associated with high-energy gamma rays.
These solar flares were imaged in extreme ultraviolet light by NASA's STEREO satellites, which at the time were viewing the side of the sun facing away from Earth. All three events launched fast coronal mass ejections (CMEs). Although NASA's Fermi Gamma-ray Space Telescope couldn't see the eruptions directly, it detected high-energy gamma rays from all of them. Scientists think particles accelerated by the CMEs rained onto the Earth-facing side of the sun and produced the gamma rays. The central image was returned by the STEREO A spacecraft, all others are from STEREO B.Credits: NASA/STEREO
Combined images from NASA's Solar Dynamics Observatory (center) and the NASA/ESA Solar and Heliospheric Observatory (red and blue) show an impressive coronal mass ejection departing the far side of the sun on Sept. 1, 2014. This massive cloud raced away at about 5 million mph and likely accelerated particles that later produced gamma rays Fermi detected. Credits: NASA/SDO and NASA/ESA/SOHO


"Observations by Fermi's LAT continue to have a significant impact on the solar physics community in their own right, but the addition of STEREO observations provides extremely valuable information of how they mesh with the big picture of solar activity," said Melissa Pesce-Rollins, a researcher at the National Institute of Nuclear Physics in Pisa, Italy, and a co-author of the paper. 

The hidden flares occurred Oct. 11, 2013, and Jan. 6 and Sept. 1, 2014. All three events were associated with fast coronal mass ejections (CMEs), where billion-ton clouds of solar plasma were launched into space. The CME from the most recent event was moving at nearly 5 million miles an hour as it left the sun. Researchers suspect particles accelerated at the leading edge of the CMEs were responsible for the gamma-ray emission.

Large magnetic field structures can connect the acceleration site with distant part of the solar surface. Because charged particles must remain attached to magnetic field lines, the research team thinks particles accelerated at the CME traveled to the sun's visible side along magnetic field lines connecting both locations. As the particles impacted the surface, they generated gamma-ray emission through a variety of processes. One prominent mechanism is thought to be proton collisions that result in a particle called a pion, which quickly decays into gamma rays.

In its first eight years, Fermi has detected high-energy emission from more than 40 solar flares. More than half of these are ranked as moderate, or M class, events. In 2012, Fermi caught the highest-energy emission ever detected from the sun during a powerful X-class flare, from which the LAT detected high­energy gamma rays for more than 20 record-setting hours.

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. 


For more information on Fermi, visit:  https://www.nasa.gov/fermi
 

By Francis Reddy
NASA's Goddard Space Flight Center
Editor: Rob Garner


Monday, January 30, 2017

Radio Weak Blazars

Black-hole-powered galaxies called blazars have powerful jets that are thought to be fortuitously aimed directly toward Earth. Blazars emit at wavelengths from the radio to the gamma-rays, but astronomers have now found two objects that are blazar like in many ways but which are radio-quiet. Credit: NASA; M. Weiss/CfA


A blazar is a galaxy whose central nucleus is bright at wavelengths from the low energy radio band to high energy gamma rays (each gamma ray photon is over a hundred million times more energetic than the X-rays seen by the Chandra X-ray Observatory). Astronomers think that the blazar nucleus contains a supermassive black hole, similar to a quasar nucleus. The emission results when matter falls onto the vicinity of the black hole and erupts into powerful, narrow jets of radiating charged particles moving close to the speed of light. Two defining characteristics of blazars, strong radio emission and high variability, are results of the accretion and jets.

Although the nuclei of other galaxies also eject jets of particles, the class of blazars is thought to result from our unique viewing angle: staring directly down the throats of these jets. The orientation makes these objects unique probes of exotic physical activity, with the relative intensities of the radiation providing key diagnostics. In most other galaxies, for example, infrared radiation comes from heated dust, but in blazars the infrared colors indicate that it comes from jet emission. Because the jet emission is so bright the underlying galaxy light can be masked, with the result that in the class of BL Lac blazars emission and absorption lines are not detected, making their distances difficult to determine.

CfA astronomers Raffaele D'Abrusco and Howard Smith and their four colleagues report discovering blazars that challenge this general paradigm. They found two BL Lac blazars with no apparent radio emission: "radio weak" BL Lacs. The astronomers discovered them by using the Fermi catalog of very high energy sources to identify a set of possible new blazars, and the WISE infrared sky catalog to reinforce the categorization and to pinpoint the locations of the sources in the sky. After searching radio catalogs for counterparts to the sources, they discovered two that had no detected radio emission.

Since blazars are by definition highly variable, and since not all of the wavelengths were measured at the same time, the scientists review the possibility that the emission at one or more wavelengths varied enough to account for the peculiar observations; they also examine some other possibilities. In the end, they conclude that although variability might be a possible explanation, if these candidates behaved like other blazars, variability alone could not resolve the mystery of the radio silence. If confirmed, these new Radio Weak BL Lac objects challenge the basic explanation of blazars. How many radio weak BL Lacs exist, how far away they are, and how they are formed and evolve - indeed why they exist at all - are now pressing questions in extragalactic astronomy.


Reference(s): 

"Radio-weak BL Lac Objects in the Fermi Era," F. Massaro, E. J. Marchesini, R. D'Abrusco, N. Masetti, I. Andruchow & Howard A. Smith, ApJ 834, 113, 2017.



Friday, January 27, 2017

Starbirth with a chance of winds?

Credit: ESA/Hubble & NASA

The lesser-known constellation of Canes Venatici (The Hunting Dogs), is home to a variety of deep-sky objects — including this beautiful galaxy, known as NGC 4861. Astronomers are still debating on how to classify it: While its physical properties — such as mass, size and rotational velocity — indicate it to be a spiral galaxy, its appearance looks more like a comet with its dense, luminous “head” and dimmer “tail” trailing behind. Features more fitting with a dwarf irregular galaxy.

Although small and messy, galaxies like NGC 4861 provide astronomers with interesting opportunities for study. Small galaxies have lower gravitational potentials, which simply means that it takes less energy to move stuff about inside them than it does in other galaxies. As a result, moving in, around, and through such a tiny galaxy is quite easy to do, making them far more likely to be suffused with streams and outflows of speedy charged particles known as galactic winds, which can flood such galaxies with little effort. 

These galactic winds can be powered by the ongoing process of star formation, which involves huge amounts of energy. New stars are springing into life within the bright, colourful ‘head’ of NGC 4861 and ejecting streams of high-speed particles as they do so, which flood outwards to join the wider galactic wind. While NGC 4861 would be a perfect candidate to study such winds, recent studies did not find any galactic winds in it.



Thursday, January 26, 2017

Cosmic lenses support finding on faster than expected expansion of the Universe


Lensed quasar and its surroundings

PR Image heic1702b
Studied lensed quasars of H0LiCOW collaboration

PR Image heic1702c
Lensed quasar

PR Image heic1702d
Lensed quasar

PR Image heic1702e
Lensed quasar

PR Image heic1702f
Lensed quasar

PR Image heic1702g
Lensed quasar



Videos

Strong Gravitational lensing
Strong Gravitational lensing

Flickering quasar images
Flickering quasar images



By using galaxies as giant gravitational lenses, an international group of astronomers using the NASA/ESA Hubble Space Telescope have made an independent measurement of how fast the Universe is expanding. The newly measured expansion rate for the local Universe is consistent with earlier findings. These are, however, in intriguing disagreement with measurements of the early Universe. This hints at a fundamental problem at the very heart of our understanding of the cosmos.

The Hubble constant — the rate at which the Universe is expanding — is one of the fundamental quantities describing our Universe. A group of astronomers from the H0LiCOW collaboration, led by Sherry Suyu (associated with the Max Planck Institute for Astrophysics in Germany, the ASIAA in Taiwan and the Technical University of Munich), used the NASA/ESA Hubble Space Telescope and other telescopes [1] in space and on the ground to observe five galaxies in order to arrive at an independent measurement of the Hubble constant [2].

The new measurement is completely independent of — but in excellent agreement with — other measurements of the Hubble constant in the local Universe that used Cepheid variable stars and supernovae as points of reference [heic1611].

However, the value measured by Suyu and her team, as well as those measured using Cepheids and supernovae, are different from the measurement made by the ESA Planck satellite. But there is an important distinction — Planck measured the Hubble constant for the early Universe by observing the cosmic microwave background.

While the value for the Hubble constant determined by Planck fits with our current understanding of the cosmos, the values obtained by the different groups of astronomers for the local Universe are in disagreement with our accepted theoretical model of the Universe. “The expansion rate of the Universe is now starting to be measured in different ways with such high precision that actual discrepancies may possibly point towards new physics beyond our current knowledge of the Universe,” elaborates Suyu.

The targets of the study were massive galaxies positioned between Earth and very distant quasars — incredibly luminous galaxy cores. The light from the more distant quasars is bent around the huge masses of the galaxies as a result of strong gravitational lensing [3]. This creates multiple images of the background quasar, some smeared into extended arcs.

Because galaxies do not create perfectly spherical distortions in the fabric of space and the lensing galaxies and quasars are not perfectly aligned, the light from the different images of the background quasar follows paths which have slightly different lengths. Since the brightness of quasars changes over time, astronomers can see the different images flicker at different times, the delays between them depending on the lengths of the paths the light has taken. These delays are directly related to the value of the Hubble constant. “Our method is the most simple and direct way to measure the Hubble constant as it only uses geometry and General Relativity, no other assumptions,” explains co-lead Frédéric Courbin from EPFL, Switzerland

Using the accurate measurements of the time delays between the multiple images, as well as computer models, has allowed the team to determine the Hubble constant to an impressively high precision: 3.8% [4]. “An accurate measurement of the Hubble constant is one of the most sought-after prizes in cosmological research today,” highlights team member Vivien Bonvin, from EPFL, Switzerland. And Suyu adds: “The Hubble constant is crucial for modern astronomy as it can help to confirm or refute whether our picture of the Universe — composed of dark energy, dark matter and normal matter — is actually correct, or if we are missing something fundamental.



Notes


[1] The study used, alongside the NASA/ESA Hubble Space Telescope, the Keck Telescope, ESO’s Very Large Telescope, the Subaru Telescope, the Gemini Telescope, the Victor M. Blanco Telescope, the Canada-France-Hawaii telescope and the NASA Spitzer Space Telescope. In addition, data from the Swiss 1.2-metre Leonhard Euler Telescope and the MPG/ESO 2.2-metre telescope were used.

[2] The gravitational lensing time-delay method that the astronomers used here to achieve a value for the Hubble constant is especially important owing to its near-independence of the three components our Universe consists of: normal matter, dark matter and dark energy. Though not completely separate, the method is only weakly dependent on these.

[3] Gravitational lensing was first predicted by Albert Einstein more than a century ago. All matter in the Universe warps the space around itself, with larger masses producing a more pronounced effect. Around very massive objects, such as galaxies, light that passes close by follows this warped space, appearing to bend away from its original path by a clearly visible amount. This is known as strong gravitational lensing.

[4] The H0LiCOW team determined a value for the Hubble constant of 71.9±2.7 kilometres per second per Megaparsec. In 2016 scientists using Hubble measured a value of 73.24±1.74 kilometres per second per Megaparsec. In 2015, the ESA Planck Satellite measured the constant with the highest precision so far and obtained a value of 66.93±0.62 kilometres per second per Megaparsec.



More Information


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

This research was presented in a series of papers to appear in the Monthly Notices of the Royal Astronomical Society.

The papers are entitled as follows: "H0LiCOW I. H0 Lenses in COSMOGRAIL’s Wellspring: Program Overview", by Suyu et al., "H0LiCOW II. Spectroscopic survey and galaxy-group identification of the strong gravitational lens system HE 0435−1223", by Sluse et al., "H0LiCOW III. Quantifying the effect of mass along the line of sight to the gravitational lens HE 0435−1223 through weighted galaxy counts", by Rusu et al., "H0LiCOW IV. Lens mass model of HE 0435−1223 and blind measurement of its time-delay distance for cosmology", by Wong et al., and "H0LiCOW V. New COSMOGRAIL time delays of HE 0435−1223: H0 to 3.8% precision from strong lensing in a flat ΛCDM model", by Bonvin et al.

The international team consists of: S. H. Suyu (Max Planck Institute for Astrophysics, Germany; Academia Sinica Institute of Astronomy and Astrophysics, Taiwan; Technical University of Munich, Germany), V. Bonvin (Laboratory of Astrophysics, EPFL, Switzerland), F. Courbin (Laboratory of Astrophysics, EPFL, Switzerland), C. D. Fassnacht (University of California, Davis, USA), C. E. Rusu (University of California, Davis, USA), D. Sluse (STAR Institute, Belgium), T. Treu (University of California, Los Angeles, USA), K. C. Wong (National Astronomical Observatory of Japan, Japan; Academia Sinica Institute of Astronomy and Astrophysics, Taiwan), M. W. Auger (University of Cambridge, UK), X. Ding (University of California, Los Angeles, USA; Beijing Normal University, China), S. Hilbert (Exzellenzcluster Universe, Germany; Ludwig-Maximilians-Universität, Munich, Germany), P. J. Marshall (Stanford University, USA), N. Rumbaugh (University of California, Davis, USA), A. Sonnenfeld (Kavli IPMU, the University of Tokyo, Japan; University of California, Los Angeles, USA; University of California, Santa Barbara, USA), M. Tewes (Argelander-Institut für Astronomie, Germany), O. Tihhonova (Laboratory of Astrophysics, EPFL, Switzerland), A. Agnello (ESO, Garching, Germany), R. D. Blandford (Stanford University, USA), G. C.-F. Chen (University of California, Davis, USA; Academia Sinica Institute of Astronomy and Astrophysics, Taiwan), T. Collett (University of Portsmouth, UK), L. V. E. Koopmans (University of Groningen, The Netherlands), K. Liao (University of California, Los Angeles, USA), G. Meylan (Laboratory of Astrophysics, EPFL, Switzerland), C. Spiniello (INAF – Osservatorio Astronomico di Capodimonte, Italy; Max Planck Institute for Astrophysics, Garching, Germany) and A. Yıldırım (Max Planck Institute for Astrophysics, Garching, Germany)

Image credit: NASA, ESA, Suyu (Max Planck Institute for Astrophysics), Auger (University of Cambridge)



Links



Contacts 

Sherry Suyu
Max Planck Institute for Astrophysics
Garching, Germany
Tel: +49 89 30000 2015
Email:
suyu@mpa-garching.mpg.de

Vivien Bonvin
Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatory of Sauverny
Versoix, Switzerland
Tel: +41 22 3792420
Email:
vivien.bonvin@epfl.ch

Frederic Courbin
Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatory of Sauverny
Versoix, Switzerland
Tel: +41 22 3792418
Email:
frederic.courbin@epfl.ch

Mathias Jäger
ESA/Hubble, Public Information Officer
Garching, Germany
Tel: +49 176 62397500
Email: hubble@eso.org


Wednesday, January 25, 2017

Gaia turns its eyes to asteroid hunting

Whilst best known for its surveys of the stars and mapping the Milky Way in three dimensions, ESA's Gaia has many more strings to its bow. Among them, its contribution to our understanding of the asteroids that litter the Solar System. Now, for the first time, Gaia is not only providing information crucial to understanding known asteroids, it has also started to look for new ones, previously unknown to astronomers.

Asteroid Gaia-606 on 26 October 2016
Credit: Observatoire de Haute-Provence & IMCCE 


Since it began scientific operations in 2014, Gaia has played an important role in understanding Solar System objects. This was never the main goal of Gaia – which is mapping about a billion stars, roughly 1% of the stellar population of our Galaxy – but it is a valuable side effect of its work. Gaia's observations of known asteroids have already provided data used to characterise the orbits and physical properties of these rocky bodies more precisely than ever before.

"All of the asteroids we studied up until now were already known to the astronomy community," explains Paolo Tanga, Planetary Scientist at Observatoire de la Côte d'Azur, France, responsible for the processing of Solar System observations.

These asteroids were identified as spots in the Gaia data that were present in one image and gone in one taken a short time later, suggesting they were in fact objects moving against the more distant stars.

Gaia's asteroid detections
Credit: ESA/Gaia/DPAC/CU4, L. Galluccio, F. Mignard, P. Tanga (Observatoire de la Côte d'Azur) 


Once identified, moving objects found in the Gaia data are matched against known asteroid orbits to tell us which asteroid we are looking at. "Now," continues Tanga, "for the first time, we are finding moving objects that can't be matched to any catalogued star or asteroid." 

 The process of identifying asteroids in the Gaia data begins with a piece of code known as the Initial Data Processing (IDT) software – which was largely developed at the University of Barcelona and runs at the Data Processing Centre at the European Space Astronomy Centre (ESAC), ESA's establishment in Spain. 

 This software compares multiple measurements taken of the same area and singles out objects that are observed but cannot be found in previous observations of the area. These are likely not to be stars but, instead, Solar System objects moving across Gaia's field of view. Once found, the outliers are processed by a software pipeline at the Centre National d'Etudes Spatiales (CNES) data centre in Toulouse, France, which is dedicated to Solar System objects. Here, the source is cross matched with all known minor bodies in the Solar System and if no match is found, then the source is either an entirely new asteroid, or one that has only been glimpsed before and has never had its orbit accurately characterised. 

Although tests have shown Gaia is very good at identifying asteroids, there have so far been significant barriers to discovering new ones. There are areas of the sky so crowded that it makes the IDT's job of matching observations of the same star very difficult. When it fails to do so, large numbers of mismatches end up in the Solar System objects pipeline, contaminating the data with false asteroids and making it very difficult to discover new ones. 

"At the beginning, we were disappointed when we saw how cluttered the data were with mismatches," explains Benoit Carry, Observatoire de la Côte d'Azur, France, who is in charge of selecting Gaia alert candidates. "But we have come up with ways to filter out these mismatches and they are working! Gaia has now found an asteroid barely observed before."

Asteroid Gaia-606 on 26 October 2016. 
Credit: Observatoire de Haute-Provence & IMCCE 


The asteroid in question, nicknamed Gaia-606, was found in October 2016 when Gaia data showed a faint, moving source. Astronomers immediately got to work and were able to predict the new asteroid's position as seen from the ground over a period of a few days. Then, at the Observatoire de Haute Provence (southern France), William Thuillot and his colleagues Vincent Robert and Nicolas Thouvenin (Observatoire de Paris/IMCCE) were able to point a telescope at the positions predicted and show this was indeed an asteroid that did not match the orbit of any previously catalogued Solar System object. 

However, despite not being present in any catalogue, a more detailed mapping of the new orbit has shown that some sparse observations of the object do already exist. This is not uncommon with new discoveries where, as with Gaia-606 (now renamed 2016 UV56), objects that first appear entirely new transpire to be re-sightings of objects whose previous observations were not sufficient to map their orbits. 

"This really was an asteroid not present in any catalogue, and that is an exciting find!" explains Thuillot. "So whilst we can't claim this is the first true asteroid discovery from Gaia, it is clearly very close and shows how near we are to finding a never-before-seen Solar System object with Gaia." 

Asteroid search region
Credit: ESA

Gaia is an ESA mission to survey one billion stars in our Galaxy and local galactic neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its origin and evolution.

The mission's primary scientific product will be a catalogue with the positions, motions, brightnesses, and colours of the more than a billion surveyed stars. The first intermediate catalogue was released in September 2016. In the meantime, Gaia's observing strategy, with repeated scans of the entire sky, is allowing the discovery and measurement of many transient events across the sky: among these are the detection of candidate asteroids which are subsequently observed by astronomers in the Gaia Follow-Up-Network. During the five-year nominal mission, Gaia is expected to observe about 350 000 asteroids of which a few thousand will be previously unknown.


About Gaia

Gaia is an ESA mission to survey one billion stars in our Galaxy and local galactic neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its origin and evolution.

The mission's primary scientific product will be a catalogue with the positions, motions, brightnesses, and colours of the more than a billion surveyed stars. The first intermediate catalogue was released in September 2016. In the meantime, Gaia's observing strategy, with repeated scans of the entire sky, is allowing the discovery and measurement of many transient events across the sky: among these are the detection of candidate asteroids which are subsequently observed by astronomers in the Gaia Follow-Up-Network. During the five-year nominal mission, Gaia is expected to observe about 350 000 asteroids of which a few thousand will be previously unknown.


Gaia Follow-Up Network for Solar System Objects
Credit: Google Earth

The nature of the Gaia mission leads to the acquisition of an enormous quantity of complex, extremely precise data, and the data-processing challenge is a huge task in terms of expertise, effort and dedicated computing power. A large pan-European team of expert scientists and software developers, the Data Processing and Analysis Consortium (DPAC), located in and funded by many ESA member states, and with contributions from ESA, is responsible for the processing and validation of Gaia's data, with the final objective of producing the Gaia Catalogue. Scientific exploitation of the data only takes place once the data are openly released to the community.


Contacts

Paolo Tanga
Observatoire de la Côte d'Azur, France
Email: Paolo.Tang@aoca.eu

Benoit Carry
Observatoire de la Côte d'Azur, France
Email: benoit.carry@oca.eu

William Thuillot
Observatoire de Paris, France
Email: William.Thuillot@obspm.fr

Timo Prusti
Gaia Project Scientist
Directorate of Science
European Space Agency
Email: timo.prusti@esa.int

Source:  ESA/Gaia

Tuesday, January 24, 2017

NuSTAR Finds New Clues to 'Chameleon Supernova'

Supernova SN 2014C (X-ray) [annotated]
This image from NASA's Chandra X-ray Observatory shows spiral galaxy NGC 7331, center, in a three-color X-ray image. Red, green and blue colors are used for low, medium and high-energy X-rays, respectively. An unusual supernova called SN 2014C has been spotted in this galaxy, indicated by the white box in the image.  Credit: NASA/CXC/CIERA/R.Margutti et al. Annotated image

Supernova SN 2014C
This visible-light image from the Sloan Digital Sky Survey shows spiral galaxy NGC 7331, center, where astronomers observed the unusual supernova SN 2014C . The inset images are from NASA's Chandra X-ray Observatory, showing a small region of the galaxy before the supernova explosion (left) and after it (right). Red, green and blue colors are used for low, medium and high-energy X-rays, respectively. Credit: X-ray images: NASA/CXC/CIERA/R.Margutti et al; Optical image: SDS.  Hi-res image
Annotated image

We're made of star stuff," astronomer Carl Sagan famously said. Nuclear reactions that happened in ancient stars generated much of the material that makes up our bodies, our planet and our solar system. When stars explode in violent deaths called supernovae, those newly formed elements escape and spread out in the universe.

One supernova in particular is challenging astronomers' models of how exploding stars distribute their elements. The supernova SN 2014C dramatically changed in appearance over the course of a year, apparently because it had thrown off a lot of material late in its life. This doesn't fit into any recognized category of how a stellar explosion should happen. To explain it, scientists must reconsider established ideas about how massive stars live out their lives before exploding.

"This 'chameleon supernova' may represent a new mechanism of how massive stars deliver elements created in their cores to the rest of the universe," said Raffaella Margutti, assistant professor of physics and astronomy at Northwestern University in Evanston, Illinois. Margutti led a study about supernova SN 2014C published this week in The Astrophysical Journal.

A supernova mystery

Astronomers classify exploding stars based on whether or not hydrogen is present in the event. While stars begin their lives with hydrogen fusing into helium, large stars nearing a supernova death have run out of hydrogen as fuel. Supernovae in which very little hydrogen is present are called "Type I." Those that do have an abundance of hydrogen, which are rarer, are called "Type II."

But SN 2014C, discovered in 2014 in a spiral galaxy about 36 million to 46 million light-years away, is different. By looking at it in optical wavelengths with various ground-based telescopes, astronomers concluded that SN 2014C had transformed itself from a Type I to a Type II supernova after its core collapsed, as reported in a 2015 study led by Dan Milisavljevic at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Initial observations did not detect hydrogen, but, after about a year, it was clear that shock waves propagating from the explosion were hitting a shell of hydrogen-dominated material outside the star.

In the new study, NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) satellite, with its unique ability to observe radiation in the hard X-ray energy range -- the highest-energy X-rays -- allowed scientists to watch how the temperature of electrons accelerated by the supernova shock changed over time. They used this measurement to estimate how fast the supernova expanded and how much material is in the external shell.

To create this shell, SN 2014C did something truly mysterious: it threw off a lot of material -- mostly hydrogen, but also heavier elements -- decades to centuries before exploding. In fact, the star ejected the equivalent of the mass of the sun. Normally, stars do not throw off material so late in their life.

"Expelling this material late in life is likely a way that stars give elements, which they produce during their lifetimes, back to their environment," said Margutti, a member of Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics.

NASA's Chandra and Swift observatories were also used to further paint the picture of the evolution of the supernova. The collection of observations showed that, surprisingly, the supernova brightened in X-rays after the initial explosion, demonstrating that there must be a shell of material, previously ejected by the star, that the shock waves had hit.

Challenging existing theories

Why would the star throw off so much hydrogen before exploding? One theory is that there is something missing in our understanding of the nuclear reactions that occur in the cores of massive, supernova-prone stars. Another possibility is that the star did not die alone -- a companion star in a binary system may have influenced the life and unusual death of the progenitor of SN 2014C. This second theory fits with the observation that about seven out of 10 massive stars have companions.
The study suggests that astronomers should pay attention to the lives of massive stars in the centuries before they explode. Astronomers will also continue monitoring the aftermath of this perplexing supernova.

"The notion that a star could expel such a huge amount of matter in a short interval is completely new," said Fiona Harrison, NuSTAR principal investigator based at Caltech in Pasadena. "It is challenging our fundamental ideas about how massive stars evolve, and eventually explode, distributing the chemical elements necessary for life."

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR's mission operations center is at UC Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center. ASI provides the mission's ground station and a mirror archive. JPL is managed by Caltech for NASA.



Monday, January 23, 2017

You Are in Command as NRAO's 'Orion Explorer' Tours this Iconic Constellation

How can you travel to distant stars from the comfort of your own home? It's easy with the new Orion Explorer, the latest installment in NRAO's interactive Milky Way Explorer. Credit: NRAO/AUI/NSF


Imagine an up-close view of a red supergiant star, a peek inside a glowing nebula churning out new stars, and spying a myriad of other objects in our galaxy as you have never seen them before – in invisible radio light! That is the experience you will get through the National Radio Astronomy Observatory’s (NRAO) newly released Orion Explorer installment of its popular Milky Way Explorer, an online tour of our interstellar neighborhood guided by the actual astronomers who study it using radio waves.

Through an entertaining and informative series of videos, NRAO’s Science Visualization Team presents multimedia-rich tours of the stars Bellatrix and Betelgeuse, stellar masers, snowlines around young stars, and much more. At each stop along the way, astronomers reveal the new science and exciting details we have learned about one of the most recognizable star patterns in the night sky, the constellation of Orion.

Unlike familiar optical telescopes, which can only study objects illuminated by stars, radio telescopes can see the otherwise invisible cold, dark features in space. This includes the faint radio light that is naturally emitted by the molecules and chemicals that make up vast interstellar clouds where new stars are born, like the Orion Nebula.

The Milky Way Explorer, which was launched in 2013, also includes dozens more videos showcasing the diverse radio astronomy studies of our home galaxy and its environs.


The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


For more information, contact:

Alexandra Angelich
aangelic@nrao.edu



Friday, January 20, 2017

A slice of Sagittarius

Constelation of Sagittarius (The Archer)
 Credit: ESA/Hubble & NASA


This stunning image, captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), shows part of the sky in the constellation of Sagittarius (The Archer). The region is rendered in exquisite detail — deep red and bright blue stars are scattered across the frame, set against a background of thousands of more distant stars and galaxies. Two features are particularly striking: the colours of the stars, and the dramatic crosses that burst from the centres of the brightest bodies.

While some of the colours in this frame have been enhanced and tweaked during the process of creating the image from the observational data, different stars do indeed glow in different colours. Stars differ in colour according to their surface temperature: very hot stars are blue or white, while cooler stars are redder. They may be cooler because they are smaller, or because they are very old and have entered the red giant phase, when an old star expands and cools dramatically as its core collapses. 

The crosses are nothing to do with the stars themselves, and, because Hubble orbits above Earth’s atmosphere, nor are they due to any kind of atmospheric disturbance. They are actually known as diffraction spikes, and are caused by the structure of the telescope itself. Like all big modern telescopes, Hubble uses mirrors to capture light and form images. Its secondary mirror is supported by struts, called telescope spiders, arranged in a cross formation, and they diffract the incoming light. Diffraction is the slight bending of light as it passes near the edge of an object. Every cross in this image is due to a single set of struts within Hubble itself! Whilst the spikes are technically an inaccuracy, many astrophotographers choose to emphasise and celebrate them as a beautiful feature of their images.



Thursday, January 19, 2017

Public to Choose Jupiter Picture Sites for NASA Juno

This amateur-processed image was taken on Dec. 11, 2016, at 9:27 a.m. PST (12:27 p.m. EST), as NASA's Juno spacecraft performed its third close flyby of Jupiter. Credit: Image credit: NASA/JPL-Caltech/SwRI/MSSS/Eric Jorgensen.  › Full image and caption


Where should NASA's Juno spacecraft aim its camera during its next close pass of Jupiter on Feb. 2? You can now play a part in the decision. For the first time, members of the public can vote to participate in selecting all pictures to be taken of Jupiter during a Juno flyby. Voting begins Thursday, Jan. 19 at 11 a.m. PST (2 p.m. EST) and concludes on Jan. 23 at 9 a.m. PST (noon EST).

"We are looking forward to people visiting our website and becoming part of the JunoCam imaging team," said Candy Hansen, Juno co-investigator from the Planetary Science Institute, Tucson, Arizona. "It's up to the public to determine the best locations in Jupiter's atmosphere for JunoCam to capture during this flyby."

NASA's JunoCam website can be visited at: https://www.missionjuno.swri.edu/junocam

The voting page for this flyby is available at:https://www.missionjuno.swri.edu/junocam/voting/

JunoCam will begin taking pictures as the spacecraft approaches Jupiter's north pole. Two hours later, the imaging will conclude as the spacecraft completes its close flyby, departing from below the gas giant's south pole. Juno is currently on its fourth orbit around Jupiter. It takes 53 days for Juno to complete one orbit.

"The pictures JunoCam can take depict a narrow swath of territory the spacecraft flies over, so the points of interest imaged can provide a great amount of detail," said Hansen. "They play a vital role in helping the Juno science team establish what is going on in Jupiter's atmosphere at any moment. We are looking forward to seeing what people from outside the science team think is important."

There will be a new voting page for each upcoming flyby of the mission. On each of the pages, several points of interest will be highlighted that are known to come within the JunoCam field of view during the next close approach. Each participant will get a limited number of votes per orbit to devote to the points of interest he or she wants imaged. After the flyby is complete, the raw images will be posted to the JunoCam website, where the public can perform its own processing.

"It is great to be able to share excitement and science from the Juno mission with the public in this way," said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. "Amateur scientists, artists, students and whole classrooms are providing the world with their unique perspectives of Jupiter. I am really pleased that this website is having such a big impact and allowing so many people to join the Juno science team. The public involvement is really affecting how we look at the most massive planetary inhabitant in our solar system."

During the Feb. 2 flyby, Juno will make its closest approach to Jupiter at 4:58 a.m. PST (7:58 a.m. EST), when the spacecraft is about 2,700 miles (4,300 kilometers) above the planet's swirling clouds.
JunoCam is a color, visible-light camera designed to capture remarkable pictures of Jupiter's poles and cloud tops. As Juno's eyes, it will provide a wide view of Jupiter over the course of the mission, helping to provide context for the spacecraft's other instruments. JunoCam was included on the spacecraft primarily for public engagement purposes, although its images also are helpful to the science team.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. The Juno mission is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of Caltech in Pasadena, California.


More information on the Juno mission is available at: http://www.nasa.gov/juno -  http://www.missionjuno.swri.edu


The public can follow the mission on Facebook and Twitter at: http://www.facebook.com/NASAJuno  -  http://www.twitter.com/NASAJuno


News Media Contact

DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011
agle@jpl.nasa.gov

Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077
dwayne.c.brown@nasa.gov / laura.l.cantillo@nasa.gov


Source:  JPL-Caltech

Galaxy murder mistery

Spiral galaxy NGC 4921
This artist’s impression shows the spiral galaxy NGC 4921 based on observations made by the Hubble Space Telescope. 
Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA).

Ram-pressure stripping of galaxy NGC 4921 
An artist’s impression of ram-pressure stripping of galaxy NGC 4921. Stripping removes gas—the raw fuel for star formation—and could be the dominant way galaxies are killed by their environment. Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA).

Ram-pressure stripping removing gas from galaxies
An artist’s impression showing the increasing effect of ram-pressure stripping in removing gas from galaxies, sending them to an early death. Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA)


Ram Stripping of Galaxies
An animation showing how ram-pressure stripping removes gas from galaxies, sending them to an early death. 
Credit: ICRAR, NASA, ESA, the Hubble Heritage Team (STScI/AURA)



It’s the big astrophysical whodunnit. Across the Universe, galaxies are being killed and the question scientists want answered is, what’s killing them?

New research published today by a global team of researchers, based at the International Centre for Radio Astronomy Research (ICRAR), seeks to answer that question. The study reveals that a phenomenon called ram-pressure stripping is more prevalent than previously thought, driving gas from galaxies and sending them to an early death by depriving them of the material to make new stars.

The study of 11,000 galaxies shows their gas—the lifeblood for star formation—is being violently stripped away on a widespread scale throughout the local Universe.

Toby Brown, leader of the study and PhD candidate at ICRAR and Swinburne University of Technology, said the image we paint as astronomers is that galaxies are embedded in clouds of dark matter that we call dark matter halos.

Dark matter is the mysterious material that despite being invisible accounts for roughly 27 per cent of our Universe, while ordinary matter makes up just 5 per cent. The remaining 68 per cent is dark energy.

“During their lifetimes, galaxies can inhabit halos of different sizes, ranging from masses typical of our own Milky Way to halos thousands of times more massive,” Mr Brown said.

“As galaxies fall through these larger halos, the superheated intergalactic plasma between them removes their gas in a fast-acting process called ram-pressure stripping.

“You can think of it like a giant cosmic broom that comes through and physically sweeps the gas from the galaxies.” Mr Brown said removing the gas from galaxies leaves them unable to form new stars.

“It dictates the life of the galaxy because the existing stars will cool off and grow old,” he said.

“If you remove the fuel for star formation then you effectively kill the galaxy and turn it into a dead object.” ICRAR researcher Dr Barbara Catinella, co-author of the study, said astronomers already knew ram-pressure stripping affected galaxies in clusters, which are the most massive halos found in the Universe.

“This paper demonstrates that the same process is operating in much smaller groups of just a few galaxies together with much less dark matter,” said Mr. Brown. “Most galaxies in the Universe live in these groups of between two and a hundred galaxies,” he said.

“We’ve found this removal of gas by stripping is potentially the dominant way galaxies are quenched by their surrounds, meaning their gas is removed and star formation shuts down.”

The study was published in the journal Monthly Notices of the Royal Astronomical Society. It used an innovative technique combining the largest optical galaxy survey ever completed—the Sloan Digital Sky Survey—with the largest set of radio observations for atomic gas in galaxies —the Arecibo Legacy Fast ALFA survey.

Mr Brown said the other main process by which galaxies run out of gas and die is known as strangulation.

“Strangulation occurs when the gas is consumed to make stars faster than it’s being replenished, so the galaxy starves to death,” he said. “It’s a slow-acting process. On the contrary, what ram-pressure stripping does is bop the galaxy on the head and remove its gas very quickly—of the order of tens of millions of years—and astronomically speaking that’s very fast.”



Publications Details


‘Cold gas stripping in satellite galaxies: from pairs to clusters’, published in the Monthly Notices of the Royal Astronomical Society on January 17th, 2017.

Click here for the research paper



More Information

ICRAR

The International Centre for Radio Astronomy Research (ICRAR) is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia.



Contact Information

Mr Toby Brown (ICRAR-UWA, Swinburne University of Technology)
Email:
toby.brown@icrar.org
M: +61 6488 7753
 
Dr Barbara Catinella (ICRAR-UWA)
Email:
barbara.catinella@icrar.org
Tel: +972 89346511
 
Pete Wheeler—Media Contact, ICRAR
Email:
pete.wheeler@icrar.org
M: +61 423 982 018


Wednesday, January 18, 2017

Geminga and B0355+54: Chandra Images Show That Geometry Solves a Pulsar Puzzle

Geminga and  PSR B0355+54
Credit: X-ray: NASA/CXC/PSU/B.Posselt et al; 
Infrared: NASA/JPL-Caltech; Illustration: Nahks TrEhnl




NASA's Chandra X-ray Observatory has taken deep exposures of two nearby energetic pulsars flying through the Milky Way galaxy. The shape of their X-ray emission suggests there is a geometrical explanation for puzzling differences in behavior shown by some pulsars.

Pulsars - rapidly rotating, highly magnetized, neutron stars born in supernova explosions triggered by the collapse of massive stars were discovered 50 years ago via their pulsed, highly regular, radio emission. Pulsars produce a lighthouse-like beam of radiation that astronomers detect as pulses as the pulsar's rotation sweeps the beam across the sky.

Since their discovery, thousands of pulsars have been discovered, many of which produce beams of radio waves and gamma rays. Some pulsars show only radio pulses and others show only gamma-ray pulses. Chandra observations have revealed steady X-ray emission from extensive clouds of high-energy particles, called pulsar wind nebulas, associated with both types of pulsars. New Chandra data on pulsar wind nebulas may explain the presence or absence of radio and gamma-ray pulses.

This four-panel graphic shows the two pulsars observed by Chandra. Geminga is in the upper left and B0355+54 is in the upper right. In both of these images, Chandra's X-rays, colored blue and purple, are combined with infrared data from NASA's Spitzer Space Telescope that shows stars in the field of view. Below each data image, an artist's illustration depicts more details of what astronomers think the structure of each pulsar wind nebula looks like.

For Geminga, a deep Chandra observation totaling nearly eight days over several years was analyzed to show sweeping, arced trails spanning half a light year and a narrow structure directly behind the pulsar. A five-day Chandra observation of the second pulsar, B0355+54, showed a cap of emission followed by a narrow double trail extending almost five light years.

The underlying pulsars are quite similar, both rotating about five times per second and both aged about half a million years. However, Geminga shows gamma-ray pulses with no bright radio emission, while B0355+54 is one of the brightest radio pulsars known yet not seen in gamma rays.

A likely interpretation of the Chandra images is that the long narrow trails to the side of Geminga and the double tail of B0355+54 represent narrow jets emanating from the pulsar's spin poles. Both pulsars also contain a torus, a disk-shaped region of emission spreading from the pulsar's spin equator. These donut-shaped structures and jets are crushed and swept back as the pulsars fly through the Galaxy at supersonic speeds.

In the case of Geminga, the view of the torus is close to edge-on, while the jets point out to the sides. B0355+54 has a similar structure, but with the torus viewed nearly face-on and the jets pointing nearly directly towards and away from Earth. In B0355+54, the swept-back jets appear to lie almost on top of each other, giving a doubled tail.

Both pulsars have magnetic poles quite close to their spin poles, as is the case for the Earth's magnetic field. These magnetic poles are the site of pulsar radio emission so astronomers expect the radio beams to point in a similar direction as the jets. By contrast the gamma-ray emission is mainly produced along the spin equator and so aligns with the torus.

For Geminga, astronomers view the bright gamma-ray pulses along the edge of the torus, but the radio beams near the jets point off to the sides and remain unseen. For B0355+54, a jet points almost along our line of sight towards the pulsar. This means astronomers see the bright radio pulses, while the torus and its associated gamma-ray emission are directed in a perpendicular direction to our line of sight, missing the Earth.

These two deep Chandra images have, therefore, exposed the spin orientation of these pulsars, helping to explain the presence, and absence, of the radio and gamma-ray pulses.
The Chandra observations of Geminga and B0355+54 are part of a large campaign, led by Roger Romani of Stanford University, to study six pulsars that have been seen to emit gamma-rays. The survey sample covers a range of ages, spin-down properties and expected inclinations, making it a powerful test of pulsar emission models.

A paper on Geminga led by Bettina Posselt of Penn State University was accepted for publication in The Astrophysical Journal and is available online. A paper on B0355+54 led by Noel Klingler of the George Washington University was published in the December 20th, 2016 issue of The Astrophysical Journal and is available online. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.



Fast Facts for Geminga:

Scale: Image is 4.6 arcmin across. (About 1 light year)
Category: Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 06h 33m 54.15s | Dec Dec: +17 46 12.91
Constellation: Gemini
Observation Dates: 14 pointings between Feb 2004 and Sep 2013
Observation Time: 188 hours 21 min
Obs. IDs: 4674, 7592, 14691-14694, 15551, 15552, 15595, 15622, 15623, 16318, 16319, 16372
Instrument: ACIS
References: Posselt, B. et al, 2016, ApJ (accepted); arXiv:1611.03496
Color Code: X-ray (Pink, Blue); Infrared (Grayscale)
Distance Estimate: About 800 light years



Fast Facts for PSR B0355+54:

Scale: Image is 1.8 arcmin across. (About 1.8 light years)
Category: Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 03h 58m 53.72s | Dec Dec: +54 13 13.73
Constellation: Camelopardalis
Observation Dates: 8 pointings between Nov 2012 and July 2013
Observation Time: 109 hours 45 min
Obs. IDs: 14688-14690, 15548-15550, 15585, 15586
Instrument:
ACIS
Color Code: X-ray (Pink, Blue); Infrared (Grayscale)
Distance Estimate: About 3400 light years