The Daily Flash -Eco, Space, Tech (10/21)
Explorers Search for Ancient Supernova Explosion at the Bottom of the World

Hundreds of Black Holes Roam the Outer Edges of the Milky Way -Why are They There? A Galaxy Classic

6a00d8341bf7f753ef0115721a27f0970b-320wi Hundreds of rogue black holes should be traveling the Milky Way's outskirts, each containing the mass of 1,000 to 100,000 suns. Each a remnant of the collapsed core of a really massive rapidly rotating star that exploded in a hypernova every 100,000 to a million years . New calculations by Ryan O'Leary and Avi Loeb of the Harvard-Smithsonian Center for Astrophysics suggest that hundreds of massive rogue black holes, left over from the galaxy-building days of the early universe, may wander the Milky Way.

The Earth appears safe, however, with the closest rogue black hole thousands of light-years away.

"These black holes are relics of the Milky Way's past," said Loeb. "You could say that we are archaeologists studying those relics to learn about our galaxy's history and the formation history of black holes in the early universe."

According to theory, rogue black holes originally lurked at the centers of tiny, low-mass galaxies. Over billions of years, those dwarf galaxies smashed together to form full-sized galaxies like the Milky Way.

Each time two proto-galaxies with central black holes collided, their black holes merged to form a single, "relic" black hole. During the merger, directional emission of gravitational radiation would cause the black hole to recoil. A typical kick would send the black hole speeding outward fast enough to escape its host dwarf galaxy, but not fast enough to leave the galactic neighborhood completely. As a result, such black holes would still be around today in the outer reaches of the Milky Way halo.

One telltale sign could mark a rogue black hole: a surrounding cluster of stars yanked from the dwarf galaxy when the black hole escaped. Only the stars closest to the black hole would be tugged along, so the cluster would be very compact.

Due to the cluster's small size on the sky, appearing to be a single star, astronomers would have to look for more subtle clues to its existence and origin. For example, its spectrum would show that multiple stars were present, together producing broad spectral lines. The stars in the cluster would be moving rapidly, their paths influenced by the gravity of the black hole.

"The surrounding star cluster acts much like a lighthouse that pinpoints a dangerous reef," explained O'Leary. "Without the shining stars to guide our way, the black holes would be all but impossible to find."

The number of rogue black holes in our galaxy depends on how many of the proto-galactic building blocks contained black holes at their cores, and how those proto-galaxies merged to form the Milky Way. Finding and studying them will provide new clues about the history of our galaxy

"Until now, astronomers were not searching for such a population of highly compact star clusters in the Milky Way's halo," said Loeb. "Now that we know what to expect, we can examine existing sky surveys for this new class of objects."

Loeb and O'Leary's journal paper will be published in the Monthly Notices of the Royal Astronomical Society and is available online at http://arxiv.org/abs/0809.4262.

Posted by Casey Kazan.

Related Galaxy posts:

18 Billion Suns -A Galaxy Classic: Biggest Black Hole in Universe Discovered—and it’s BIG
Neutron Stars: New Discovery Proves Einstein's Space-Time Predictions
Mystery Neutron Star Discovered
Andromeda Galaxy & Its Mystery Core: Destined to Merge With the Milky Way?
Neutron Stars & The Physics of Star Trek
New, Revised Hitchhiker's Guide to the Galaxy
Black Holes Key to Mapping the Evolution of the Universe

Source: http://www.cfa.harvard.edu/news/2009/pr200912.html

Comments

Black hole and Big bang.
============== ....
1.
A black hole is a theoretical region of space in which the
gravitational field is so powerful that nothing can escape.
2.
Hawking Radiation theorizes that black holes do not,
in fact, absorb all matter absolutely; they give off some
return matter.
3.
Once upon a time, 20 billions of years ago, all matter
(all elementary particles and all quarks and their
girlfriends- antiparticles and antiquarks, all kinds of
waves: electromagnetic, gravitational, muons…
gluons field ….. etc.) – was assembled in a ‘single point ‘

The reason of this unity is gravitational force.
4.
How did the ‘single point ‘ create if the matter
can escape from any strong gravitational force?

==== .
Best wishes.
Israel Sadovnik. / Socratus.

http://www.worldnpa.org/php2/index.php?tab0=Scientists&tab1=Display&id=1372
www.socratus.com
===================== . .

Perhaps they are the elusive dark matter.

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