* Astronomy

Blobrana · L

RE: Black Holes

Blobrana · L

Chandra's observation of black holes

Blobrana · L

A black hole's intense gravitational field can cause individual photons of light to go into orbit around it temporarily, new calculations suggest. That means that photons from a single burst of light that explodes near the black hole could orbit the hole for different amounts of time before escaping into space, making the black hole appear to flash like a strobe light.
The light pulses could give scientists a new window on the mysterious properties of black holes, such as their mass and rotation rate.
Scientists have long known that black holes can bend light. But Keigo Fukumura and Demosthenes Kazanas, both of NASA's Goddard Space Flight Centre in Greenbelt, Maryland, US, say photons that come in at just the right angle can be bent into nearly circular paths, causing them to swing around the black hole one or more times before flying off into space.
The rapid-fire pulses are triggered when a flash of X-ray light called a flare goes off in the disc of matter swirling into a feeding black hole. Scientists are still not sure what causes these flares, but they are common around black holes.

Read more

Blobrana · L

NASA's Spitzer Space Telescope has detected plump black holes where least expected -- skinny galaxies.

Read more

Blobrana · L

Scientists have uncovered a supermassive black hole at the core of a svelte, spiral galaxy, a finding that questions a recently devised rule of thumb in which only galaxies with bulging cores have such black holes.
Read more

Blobrana · L

A Nasa telescope has discovered bulky black holes lurking where they are least expected - in skinny galaxies.
So-called supermassive black holes were thought to reside at the cores of nearly all galaxies.
But svelte galaxies lacking a central concentration of stars - or bulge - were thought to be a rare exception.
Previous observations had suggested that the more massive the bulge in a galaxy, the bigger the black hole. So it seemed reasonable to think that the formation and growth of galactic bulges must be intimately linked to their central black holes.

Read more

Blobrana · L


Credit: NASA/CXC/UFRGS/R.Nemmen et al.; Illustration: NASA/CXC/M.Weiss
JPEG (179 kb)	Tiff (15.1 MB)	PS (10.3 MB)

Results from NASA's Chandra X-ray Observatory, combined with new theoretical calculations, provide one of the best pieces of evidence yet that many supermassive black holes are spinning extremely rapidly. The images on the left show 4 out of the 9 large galaxies included in the Chandra study, each containing a supermassive black hole in its centre.
The Chandra images show pairs of huge bubbles, or cavities, in the hot gaseous atmospheres of the galaxies, created in each case by jets produced by a central supermassive black hole. Studying these cavities allows the power output of the jets to be calculated. This sets constraints on the spin of the black holes when combined with theoretical models.

Read more

Blobrana · L

Galaxy may hold hundreds of rogue black holes
If the latest simulation of what happens when black holes merge is correct, there could be hundreds of rogue black holes, each weighing several thousand times the mass of the sun, roaming around the Milky Way galaxy.

Read more

Blobrana · L

Peering into the heart of a black hole
A glimpse beyond the event horizon.
Quantum mechanics might be capable of stripping bare a black hole to reveal the mysterious and unseeable 'singularity' that exists at its heart1, say George Matsas and André da Silva of the São Paulo State University in Brazil.
It has long been suspected that these singularities where the known laws of physics break down are always decorously veiled behind the 'event horizon', a boundary beyond which light cannot escape from the fearsome gravitational pull of a black hole.
Theoretically, nothing within an event horizon can ever be perceived or investigated by an outside observer, because no light can escape. So the singularities remain insulated from the rest of the Universe.

Read more

Blobrana · L

The theory that predicted black holes in the first place general relativity says that all the matter inside them gets squashed into a central point of infinite density called a singularity.
Dr Christian Böhmer and colleague Kevin Vandersloot of the University of Portsmouth in the UK applied loop quantum gravity, which defines space-time as a network of abstract links that connect tiny chunks of space, to black holes in general. Because loop quantum gravity equations cannot be solved exactly for the inside of every black hole, the researchers used computers to approximate what would happen to the infalling matter.

Read more