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Backwards Black Holes Might Make Bigger Jets

Copyright NASA

Going against the grain may turn out to be a powerful move for black holes. New research suggests supermassive black holes that spin backwards might produce more ferocious jets of gas. The results have broad implications for how galaxies change over time.

“A lot of what happens in an entire galaxy depends on what’s going on in the miniscule central region where the black hole lies,” said theoretical astrophysicist David Garofalo of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Garofalo is lead author of a new paper that appeared online May 27 in the Monthly Notices of the Royal Astronomical Society. Other authors are Daniel A. Evans of the Massachusetts Institute of Technology, Cambridge, Mass., and Rita M. Sambruna of NASA Goddard Space Flight Center, Greenbelt, Md.

Black holes are immense distortions of space and time with gravity that is so great, even light itself cannot escape. Astronomers have known for more than a decade that all galaxies, including our own Milky Way, are anchored by tremendous, so-called supermassive black holes, containing billions of suns’ worth of mass. The black holes are surrounded and nourished by disks of gas and dust, called accretion disks. Powerful jets stream [...]

NASA’s Swift Survey Finds ‘Smoking Gun’ Of Black Hole Activation

Copyright NASA

Data from an ongoing survey by NASA’s Swift satellite have helped astronomers solve a decades-long mystery about why a small percentage of black holes emit vast amounts of energy.

Only about one percent of supermassive black holes exhibit this behavior. The new findings confirm that black holes “light up” when galaxies collide, and the data may offer insight into the future behavior of the black hole in our own Milky Way galaxy. The study will appear in the June 20 issue of The Astrophysical Journal Letters.

The intense emission from galaxy centers, or nuclei, arises near a supermassive black hole containing between a million and a billion times the sun’s mass. Giving off as much as 10 billion times the sun’s energy, some of these active galactic nuclei (AGN) are the most luminous objects in the universe. They include quasars and blazars.

“Theorists have shown that the violence in galaxy mergers can feed a galaxy’s central black hole,” said Michael Koss, the study’s lead author and a graduate student at the University of Maryland in College Park. “The study elegantly explains how the black holes switched on.”

Until Swift’s hard X-ray survey, astronomers never could be sure [...]

XMM-Newton discovers a new class of black holes

XMM-Newton discovers a new class of black holes

Copyright ESA

Astronomers using ESA’s XMM-Newton X-ray observatory have discovered a black hole weighing more than 500 solar masses, a missing link between lighter stellar-mass and heavier supermassive black holes, in a distant galaxy. This discovery is the best detection to date of a new class that has long been searched for: intermediate mass black holes. Due to appear tomorrow in the journal Nature, the discovery has been made by an international team of researchers working with XMM-Newton data, led by Sean Farrell from the Centre d’Etude Spatiale des Rayonnements, now based at the University of Leicester. Stellar-mass black holes (about three to twenty times as massive as the Sun) and supermassive black holes (several million to several thousand million times as massive as the Sun) have long been known to exist. Because of the large gap between these two extremes, scientists have speculated the existence of a third, intermediate class of black holes, with masses between a hundred and several hundred thousand solar masses. Up until now, scientists were unable to confirm that this elusive intermediate class actually existed. Farrell’s team were analysing archived data obtained by XMM-Newton, looking for neutron stars and white dwarves, when they stumbled [...]

XMM-Newton takes astronomers to a black hole’s edge

xmm-newton-takes-astronomers-to-a-black-holes-edge

Copyright ESA

Using new data from ESA’s XMM-Newton spaceborne observatory, astronomers have probed closer than ever to a supermassive black hole lying deep at the core of a distant active galaxy.

The galaxy – known as 1H0707-495 – was observed during four 48-hr-long orbits of XMM-Newton around Earth, starting in January 2008. The black hole at its centre was thought to be partially obscured from view by intervening clouds of gas and dust, but these current observations have revealed the innermost depths of the galaxy.

“We can now start to map out the region immediately around the black hole,” says Andrew Fabian, at the University of Cambridge, who headed the observations and analysis.

X-rays are produced as matter swirls into a supermassive black hole. The X-rays illuminate and are reflected from the matter before its eventual accretion. Iron atoms in the flow imprint characteristic iron lines on the reflected light. The iron lines are distorted in a number of characteristic ways: they are affected by the speed of the orbiting iron atoms, the energy required for the X-rays to escape the black hole’s gravitational field, and the spin of the black hole. All these features show that the astronomers are [...]

Integral catches a new erupting black hole

integral-catches-a-new-erupting-black-hole

Copyright ESA

ESA’s gamma-ray observatory, Integral, has spotted a rare kind of gamma-ray outburst. The vast explosion of energy allowed astronomers to pinpoint a possible black hole in our Galaxy.

The outburst was discovered on 17 September 2006 by staff at the Integral Science Data Centre (ISDC), Versoix, Switzerland. Inside the ISDC, astronomers constantly monitor the data coming down from Integral because they know the sky at gamma-ray wavelengths can be a swiftly changing place.

“The galactic centre is one of the most exciting regions for gamma ray astronomy because there are so many potential gamma-ray sources,” says Roland Walter, an astronomer at the ISDC, and lead author of these results.

To reflect the importance of this region, Integral is now running a Key Programme, in which almost four weeks of its observing time is given over to the study of the galactic centre. This is allowing astronomers to understand the gamma-ray characteristics of the galactic centre and its celestial objects, better than ever before.

XMM-Newton’s image of X-ray nova IGR J17497-2821 It was during one of the first of these observations that astronomers saw the outburst take place. An unexpected event of this kind is known as a ‘target [...]

Black hole without a home

black-hole-without-a-home

Copyright ESA

The detection of a super-massive black hole without a massive ‘host’ galaxy is the surprising result from a large Hubble and VLT study of quasars.

This is the first convincing discovery of such an object. One intriguing explanation is that the host galaxy may be made almost exclusively of ‘dark matter’.

A team of European astronomers has used two of the most powerful astronomical facilities available, the NASA/ESA Hubble Space Telescope and the ESO Very Large Telescope (VLT) at Cerro Paranal, to discover a bright quasar without a massive host galaxy.

Quasars are powerful and typically very distant source of huge amounts of radiation. They are commonly associated with galaxies containing an active central black hole.

The team conducted a detailed study of 20 relatively nearby quasars. For 19 of them, they found, as expected, that these super-massive black holes are surrounded by a host galaxy. But when they studied the bright quasar HE0450-2958, located some 5000 million light-years away, they could not find evidence for a host galaxy.

The astronomers suggest that this may indicate a rare case of a collision between a seemingly normal spiral galaxy and an ‘exotic’ object harbouring a very massive black hole.

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