 |
|
Integral expands our view of the gamma-ray sky
February 21, 2007Integral's latest survey of the gamma-ray universe continues to change the way astronomers think of the high-energy cosmos. With over seventy percent of the sky now observed by Integral, astronomers have been able to construct the largest catalogue yet of individual gamma-ray-emitting celestial objects. And there is no end in sight for the discoveries.
Integral is the European Space Agency's latest orbiting gamma-ray observatory. Ever since Integral began scientific operations in 2003, the project team has been devoting a substantial proportion of its observing time to a survey of the gamma-ray universe.
"The gamma-ray sky is notoriously variable and extremely unpredictable," says Anthony Dean, University of Southampton, UK, one of the original proposers of the Integral mission. Hence, the need for Integral's constant vigilance and an accurate catalogue of all gamma-ray sources. With this, astronomers can target individual gamma-ray objects for more detailed, study.
or the past three and a half years, Integral has been collecting survey data. At the end of every year, the data has been turned into a catalogue of sources.
During the first year, it concentrated on the regions close to the centre of our galaxy and found more than 120 sources. During the following year, Integral broadened its reach and found almost 100 more sources.
Now Integral has observed over 70 percent of the sky, with a total exposure time of 40 million seconds. A European team of astronomers led by Antony Bird, University of Southampton, UK, have turned all three years' worth of data into the third Integral catalogue of gamma-ray sources. It contains a total of 421 gamma-ray objects. Most have been identified as either binary stars in our Galaxy containing exotic objects such as black holes and neutron stars, or active galaxies, far away in space. But a puzzling quarter of sources remain unidentified so far.
"I think many of these will turn out to be either star systems enshrouded in dust and gas, or cataclysmic variable stars," says Dean. Integral observes in the gamma-ray band so it can see through the intervening material. It has demonstrated that it can discover sources obscured at other wavelengths.
One surprise has been the efficiency with which Integral has detected just one minor subclass of cataclysmic variable stars (CVs), the so-called intermediate polars. Initially astronomers were not sure that CVs would emit gamma rays. Indeed, Integral has already shown that only about one percent of them do. "At the moment, the reason why this should be is totally mysterious," says Dean.
As its surveys points further from our Galaxy, so Integral increasingly sees the active galaxies. These represent about a tenth of all galaxies and each one has some kind of extraordinary activity taking place in its core. It is widely accepted that this activity is driven by a gigantic black hole sucking matter out of existence.
Roman Krivonos, Max-Planck-Institute für Astrophysik, Germany, and colleagues have used the Integral survey to show that AGN are concentrated in the same places that ordinary galaxies are found. Whilst this is not an unexpected result, it is the first time such an AGN distribution has been seen at high-energies.
"Integral represents a milestone in gamma-ray astronomy," says Dean. Thirty years ago, NASA's Einstein observatory produced a catalogue of X-ray sources that became the standard reference document for all X-ray observatories - including ESA's XMM-Newton. "Integral is doing the same for gamma-ray astronomy," says Dean.
"We are in a golden age of gamma-ray astronomy," agrees Bird. And ESA's Integral is at the forefront of this brave new universe.
European Space Agency
During the first year, it concentrated on the regions close to the centre of our galaxy and found more than 120 sources. During the following year, Integral broadened its reach and found almost 100 more sources.
Now Integral has observed over 70 percent of the sky, with a total exposure time of 40 million seconds. A European team of astronomers led by Antony Bird, University of Southampton, UK, have turned all three years' worth of data into the third Integral catalogue of gamma-ray sources. It contains a total of 421 gamma-ray objects. Most have been identified as either binary stars in our Galaxy containing exotic objects such as black holes and neutron stars, or active galaxies, far away in space. But a puzzling quarter of sources remain unidentified so far.
"I think many of these will turn out to be either star systems enshrouded in dust and gas, or cataclysmic variable stars," says Dean. Integral observes in the gamma-ray band so it can see through the intervening material. It has demonstrated that it can discover sources obscured at other wavelengths.
One surprise has been the efficiency with which Integral has detected just one minor subclass of cataclysmic variable stars (CVs), the so-called intermediate polars. Initially astronomers were not sure that CVs would emit gamma rays. Indeed, Integral has already shown that only about one percent of them do. "At the moment, the reason why this should be is totally mysterious," says Dean.
As its surveys points further from our Galaxy, so Integral increasingly sees the active galaxies. These represent about a tenth of all galaxies and each one has some kind of extraordinary activity taking place in its core. It is widely accepted that this activity is driven by a gigantic black hole sucking matter out of existence.
Roman Krivonos, Max-Planck-Institute für Astrophysik, Germany, and colleagues have used the Integral survey to show that AGN are concentrated in the same places that ordinary galaxies are found. Whilst this is not an unexpected result, it is the first time such an AGN distribution has been seen at high-energies.
"Integral represents a milestone in gamma-ray astronomy," says Dean. Thirty years ago, NASA's Einstein observatory produced a catalogue of X-ray sources that became the standard reference document for all X-ray observatories - including ESA's XMM-Newton. "Integral is doing the same for gamma-ray astronomy," says Dean.
"We are in a golden age of gamma-ray astronomy," agrees Bird. And ESA's Integral is at the forefront of this brave new universe.
European Space Agency
Gamma-ray Burst News and Current Gamma-ray Burst Events RSSThe quiet explosion
A European-led team of astronomers are providing hints that a recent supernova may not be as normal as initially thought. Instead, the star that exploded is now understood to have collapsed into a black hole, producing a weak jet, typical of much more violent events, the so-called gamma-ray bursts.
UC Santa Cruz physicists eagerly await launch of NASA space telescope they helped build
When NASA launches its newest space observatory, physicists at the University of California, Santa Cruz, will be watching as the product of nearly 16 years of hard work blasts into orbit.
NASA's Swift satellite catches first 'normal' supernova in the act of exploding
Thanks to a fortunate observation with NASA's Swift satellite, astronomers, for the first time, have caught a normal supernova at the moment of its birth--the first instant when an exploding star begins spewing its energy into space, transforming into a supernova that during its brief lifetime will shine brighter than billions of stars combined.
Astronomers find record-old cosmic explosion
Using the powerful one-two combo of NASA's Swift satellite and the Gemini Observatory, astronomers from a number of institutions, including Johns Hopkins, have detected a mysterious type of cosmic explosion farther back in time than ever before.
Gamma-ray birth cries suggest massive magnetic engines
Several times a week, astronomers detect the violent death cry of a massive star — an extraordinarily energetic release of gamma rays that takes place in just a matter of seconds to minutes, called a gamma-ray burst (GRB).
Astronomers discover new kind of black-hole explosion
Scientists have discovered what appears to be a new kind of cosmic explosion - a "hybrid gamma-ray burst" - which will be the subject of four articles to be published in the journal Nature on 21 December 2006.
Scientists piece together the most distant cosmic explosion
In this week's issue of Nature, scientists at Penn State University and their U.S. and European colleagues discuss how this explosion, detected on 4 September 2005, was the result of a massive star collapsing into a black hole.
Rare gamma-ray flare from a distant star disturbs Earth's daytime ionosphere
On Dec. 27, 2004, scientists detected the largest gamma-ray burst ever recorded. It came from a magnetar-a neutron star with an enormous magnetic field-50,000 light years away.
Astronomers link old stars and mysterious cosmic explosions
Cosmic gamma-ray bursts, the most powerful explosions in the universe, have the extreme brilliance of a billion billion Suns and occur several times a day.
HETE-2 satellite solves mystery of cosmic explosions
An international team of scientists using three NASA satellites and a host of ground-based telescopes believes it has solved the greatest remaining mystery of the mysterious gamma-ray bursts (GRBs), the most powerful explosions in the universe.
More Gamma-ray Burst News Articles
 | Gamma-Ray Bursts in the Afterglow Era: Proceedings of the International Workshop Held in Rome, Italy, 17-20 October 2000 (ESO Astrophysics Symposia) The information received from BeppoSAX, Chandra and other instruments in the last two years has more than doubled the number of samples of Gamma-Ray Bursts localized and followed up for afterglow search. This has also increased the interest of astronomers in GRBs. This book reviews the research of the last two years and covers the global properties of GRBs, GRB afterglows, GRB host galaxies,... |
 | The Biggest Bangs: The Mystery of Gamma-Ray Bursts, the Most Violent Explosions in the Universe by Jonathan I. Katz Gamma-ray bursts are the most violent events since the birth of the universe. They are about ten times more energetic than the most powerful supernovae. At their peak, gamma-ray bursts are the brightest objects in space, about 100,000 times brighter than an entire galaxy. And yet until recently these titanic eruptions were the most mysterious events in astronomy. In The Biggest Bangs,... |
 | Toward an Understanding of the Progenitors of Gamma-Ray Bursts by Joshua S. Bloom The various possibilities for the origin ("progenitors") of gamma-ray bursts (GRBs) manifest in differing observable properties. Through deep spectroscopic and high-resolution imaging observations of some GRB hosts, I demonstrate that well-localized long-duration GRBs are connected with otherwise normal star-forming galaxies at moderate redshifts of order unity. Using high-mass binary stellar... |
 | Cosmic Catastrophes: Supernovae, Gamma-Ray Bursts, and Adventures in Hyperspace by J. Craig Wheeler In this tour de force of the ultimate and extreme in astrophysics, renowned astrophysicist and author J. Craig Wheeler takes us on a breathtaking journey to supernovae, black holes, gamma-ray bursts and adventures in hyperspace. This is no far-fetched science fiction tale, but an enthusiastic exploration of ideas at the cutting edge of current astrophysics. Wheeler follows the tortuous life of a... |
 | Flash!: The Hunt for the Biggest Explosions in the Universe by Govert Schilling About three times a day our sky flashes with a powerful pulse of gamma ray bursts (GRB), invisible to human eyes but not to astronomers' instruments. The sources of this intense radiation are likely to be emitting, within the span of seconds or minutes, more energy than the sun will in its entire 10 billion years of life. Where these bursts originate, and how they come to have such incredible... |
 | Exploding Superstars: Understanding Supernovae and Gamma-Ray Bursts (Springer Praxis Books / Popular Astronomy) by Alain Mazure, Stéphane Basa In Exploding Superstars, Alain Mazure and Stephane Basa show how great stellar explosions have become extremely important in recent years to cosmologists trying to understand the evolution of our universe since the Big Bang and the scale of that universe. Recently supernovae and gamma-ray bursters have been used, for example, as "standard candles," illuminating their immediate environs like... |
 | Astrophysics: A New Approach (Astronomy and Astrophysics Library) by Wolfgang Kundt For a quantitative understanding of the physics of the universe - from the solar system through the milky way to clusters of galaxies all the way to cosmology - these edited lecture notes are perhaps among the most concise and also among the most critical ones: Astrophysics has not yet stood the redundancy test of laboratory physics, hence should be wary of early interpretations. Special chapters... |
| From Luminous Hot Stars to Starburst Galaxies (Cambridge Astrophysics) by Peter S. Conti, Paul Crowther, Claus Leitherer Before exploding as supernovae, luminous hot stars live out their lives of a few million years with prodigious outputs of radiation and stellar winds, dramatically affecting both their evolution and environments. This book offers a detailed introduction to the astrophysics of these massive stars and how they contribute to the evolution of galaxies and starburst phenomena. HII galaxies, their... | |
| Cosmic Mysteries (Voyage Through the Universe) by Time Life Books | |
| First Stars III (AIP Conference Proceedings / Astronomy and Astrophysics) (AIP Conference Proceedings) This conference explored the formation, life, and death of the earliest stars (also known as Population III stars) and their impact on subsequent structure formation and chemical evolution of the universe. First Stars III covered a wide range of observational topics, including star formation, stellar evolution, supernovae, and the search for primordial and metal-poor stars in the galactic... |
| © 2008 BrightSurf.com |