[meteorite-list] NASA's Chandra Detects Record-Breaking Outburst from Milky Way's Black Hole

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 6 Jan 2015 12:52:35 -0800 (PST)
Message-ID: <201501062052.t06KqZG6011941_at_zagami.jpl.nasa.gov>

     
January 5, 2015
     
NASA's Chandra Detects Record-Breaking Outburst from Milky Way's Black Hole

Astronomers have observed the largest X-ray flare ever detected from the
supermassive black hole at the center of the Milky Way galaxy. This event,
detected by NASA's Chandra X-ray Observatory, raises questions about the
behavior of this giant black hole and its surrounding environment.

The supermassive black hole at the center of our galaxy, called Sagittarius
A*, or Sgr A*, is estimated to contain about 4.5 million times the mass of
our sun.

Astronomers made the unexpected discovery while using Chandra to observe how
Sgr A* would react to a nearby cloud of gas known as G2.

"Unfortunately, the G2 gas cloud didn't produce the fireworks we were
hoping for when it got close to Sgr A*," said lead researcher Daryl Haggard
of Amherst College in Massachusetts. "However, nature often surprises us
and we saw something else that was really exciting."

On Sept. 14, 2013, Haggard and her team detected an X-ray flare from Sgr A*
400 times brighter than its usual, quiet state. This "megaflare" was
nearly three times brighter than the previous brightest X-ray flare from Sgr
A* in early 2012. After Sgr A* settled down, Chandra observed another
enormous X-ray flare 200 times brighter than usual on Oct. 20, 2014.

Astronomers estimate that G2 was closest to the black hole in the spring of
2014, 15 billion miles away. The Chandra flare observed in September 2013 was
about a hundred times closer to the black hole, making the event unlikely
related to G2.

The researchers have two main theories about what caused Sgr A* to erupt in
this extreme way. The first is that an asteroid came too close to the
supermassive black hole and was torn apart by gravity. The debris from such a
tidal disruption became very hot and produced X-rays before disappearing
forever across the black hole's point of no return, or event horizon.

"If an asteroid was torn apart, it would go around the black hole for a
couple of hours - like water circling an open drain - before falling
in," said co-author Fred Baganoff of the Massachusetts Institute of
Technology in Cambridge, Massachusetts. "That's just how long we saw the
brightest X-ray flare last, so that is an intriguing clue for us to
consider."

If this theory holds up, it means astronomers may have found evidence for the
largest asteroid to produce an observed X-ray flare after being torn apart by
Sgr A*.

A second theory is that the magnetic field lines within the gas flowing
towards Sgr A* could be tightly packed and become tangled. These field lines
may occasionally reconfigure themselves and produce a bright outburst of
X-rays. These types of magnetic flares are seen on the sun, and the Sgr A*
flares have similar patterns of intensity.

"The bottom line is the jury is still out on what's causing these giant
flares from Sgr A*," said co-author Gabriele Ponti of the Max Planck
Institute for Astrophysics in Garching, Germany. "Such rare and extreme
events give us a unique chance to use a mere trickle of infalling matter to
understand the physics of one of the most bizarre objects in our galaxy."

In addition to the giant flares, the G2 observing campaign with Chandra also
collected more data on a magnetar: a neutron star with a strong magnetic
field, located close to Sgr A*. This magnetar is undergoing a long X-ray
outburst, and the Chandra data are allowing astronomers to better understand
this unusual object.

These results were presented at the 225th meeting of the American
Astronomical Society being held in Seattle. 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.

NASA is exploring our solar system and beyond to understand the universe and
our place in it. The agency seeks to unravel the secrets of our universe, its
origins and evolution, and search for life among the stars.

An interactive image, a podcast, and a video about the findings are available
at:

http://chandra.si.edu

For more Chandra images, multimedia and related materials, visit:

http://www.nasa.gov/chandra

-end-

Felicia Chou
Headquarters, Washington
202-358-0257
felicia.chou at nasa.gov

Janet Anderson
Marshall Space Flight Center, Huntsville, Ala.
256-544-6162
janet.l.anderson at nasa.gov

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
mwatzke at cfa.harvard.edu
Received on Tue 06 Jan 2015 03:52:35 PM PST