Space

October 9, 2012

NASA’s Swift satellite discovers new black hole in our galaxy

NASA’s Swift satellite recently detected a rising tide of high-energy X-rays from a source toward the center of our Milky Way galaxy. The outburst, produced by a rare X-ray nova, announced the presence of a previously unknown stellar-mass black hole.

“Bright X-ray novae are so rare that they’re essentially once-a-mission events and this is the first one Swift has seen,” said Neil Gehrels, the mission’s principal investigator, at NASA’s Goddard Space Flight Center in Greenbelt, Md. “This is really something we’ve been waiting for.”

An X-ray nova is a short-lived X-ray source that appears suddenly, reaches its emission peak in a few days and then fades out over a period of months. The outburst arises when a torrent of stored gas suddenly rushes toward one of the most compact objects known, either a neutron star or a black hole.

The rapidly brightening source triggered Swift’s Burst Alert Telescope twice on the morning of Sept. 16, and once again the next day.

Named Swift J1745-26 after the coordinates of its sky position, the nova is located a few degrees from the center of our galaxy toward the constellation Sagittarius. While astronomers do not know its precise distance, they think the object resides about 20,000 to 30,000 light-years away in the galaxy’s inner region.

Ground-based observatories detected infrared and radio emissions, but thick clouds of obscuring dust have prevented astronomers from catching Swift J1745-26 in visible light.

The nova peaked in hard X-rays — energies above 10,000 electron volts, or several thousand times that of visible light — on Sept. 18, when it reached an intensity equivalent to that of the famous Crab Nebula, a supernova remnant that serves as a calibration target for high-energy observatories and is considered one of the brightest sources beyond the solar system at these energies.

Even as it dimmed at higher energies, the nova brightened in the lower-energy, or softer, emissions detected by Swift’s X-ray Telescope, a behavior typical of X-ray novae. By Wednesday, Swift J1745-26 was 30 times brighter in soft X-rays than when it was discovered and it continued to brighten.

“The pattern we’re seeing is observed in X-ray novae where the central object is a black hole. Once the X-rays fade away, we hope to measure its mass and confirm its black hole status,” said Boris Sbarufatti, an astrophysicist at Brera Observatory in Milan, Italy, who currently is working with other Swift team members at Penn State in University Park, Pa.

The black hole must be a member of a low-mass X-ray binary system, which includes a normal, sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole. In most LMXBs, the gas in the disk spirals inward, heats up as it heads toward the black hole, and produces a steady stream of X-rays.

But under certain conditions, stable flow within the disk depends on the rate of matter flowing into it from the companion star. At certain rates, the disk fails to maintain a steady internal flow and instead flips between two dramatically different conditions – a cooler, less ionized state where gas simply collects in the outer portion of the disk like water behind a dam, and a hotter, more ionized state that sends a tidal wave of gas surging toward the center.

“Each outburst clears out the inner disk, and with little or no matter falling toward the black hole, the system ceases to be a bright source of X-rays,” said John Cannizzo, a Goddard astrophysicist. “Decades later, after enough gas has accumulated in the outer disk, it switches again to its hot state and sends a deluge of gas toward the black hole, resulting in a new X-ray outburst.”

This phenomenon, called the thermal-viscous limit cycle, helps astronomers explain transient outbursts across a wide range of systems, from protoplanetary disks around young stars, to dwarf novae — where the central object is a white dwarf star — and even bright emission from supermassive black holes in the hearts of distant galaxies.

Swift, launched in November 2004, is managed by Goddard Space Flight Center. It is operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Va., with international collaborators in the United Kingdom and Italy and including contributions from Germany and Japan.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines October 29, 2014

News: Unmanned rocket explodes just six seconds after taking off - A NASA rocket due to be visible across the East Coast on its way to the International Space Station has blown up on the Launchpad. IG: Former chief of wounded warrior office broke law, DOD regs - The Defense Department inspector general has recommended “corrective action”...
 
 

News Briefs October 29, 2014

F-35C makes first landing at Virginia Beach Navy base The Navy says an operational F-35C joint strike fighter has landed at Naval Air Station Oceana for the first time. Naval Air Station Oceana is the Navy’s master jet base on the East Coast. The Navy says the plane came to the Virginia Beach base Oct....
 
 

Time to turn to American technology for space launch

For the first time since the Cold War, the United States has deployed armored reinforcements to Europe. To counter Russia’s aggression, several hundred troops and 20 tanks are now in the Baltic. Yet the U.S. military is still injecting millions into the Russian military industrial complex. In late August, the United Launch Alliance – the...
 

 
Air Force photograph by Joe Davila

Boeing, Air Force demonstrate Minuteman III readiness in flight test

Air Force photograph by Joe Davila Boeing supported the launch of an unarmed Minuteman III intercontinental ballistic missile at Vandenberg Air Force Base, Calif., on Sept. 23, 2014. Boeing supported the U.S. Air Force’s succ...
 
 

Pentagon going to court for refusing to release Sikorsky data

PETALUMA, Calif. – The Pentagon is refusing to release any data on any prime contractors participating in the 25-year-old Comprehensive Subcontracting Plan Test Program. The American Small Business League launched a program in 2010 to expose the fraud and abuse against small businesses the CSPTP had allowed. As a test the ASBL requested the most...
 
 
Northrop Grumman photograph

Raytheon Griffin C flight tests demonstrate in-flight retargeting capability

Northrop Grumman photograph Northrop Grumman has received a contract from the U.S. Marine Corps for low-rate initial production of the AN/TPS-80 Ground/Air Task Oriented Radar (G/ATOR). G/ATOR is the first ground-based multi-mi...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>