Swift Catches X-ray Activity at the Galaxy's Center

  • Released Wednesday, January 8, 2014
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A seven-year campaign to monitor the center of our galaxy with NASA's Swift spacecraft has provided astronomers with a unique bounty, more than doubling the number of bright X-ray flares observed from our galaxy's central black hole and leading to the discovery of a rare type of neutron star.

The innermost region of our galaxy lies 26,000 light-years away in the direction of the constellation Sagittarius. At the center of it all lurks Sgr A (pronounced "saj a-star"), a behemoth black hole containing 4 million times the sun's mass.

Sgr A regularly produces bright X-ray flares today, but astronomers know it was much more active in the past.

To better understand its long-term behavior, the Swift team began regular observations of the galactic center in February 2006. Every few days, the spacecraft turns toward the inmost galaxy and takes a 17-minute-long "snapshot" with its X-Ray Telescope (XRT).

Swift's XRT has now detected six bright flares, during which the black hole's X-ray emission brightened by up to 150 times for a couple of hours. These new detections, in addition to four found by other spacecraft, enabled astronomers to estimate that similar flares occur every five to 10 days.

The Swift XRT team is on the lookout for the first sign that a small cold gas cloud named G2, which is swinging near Sgr A, has begun emitting X-rays. This is expected to start sometime in spring 2014. The event will unfold for years and may fuel strong activity from the monster black hole.

The monitoring campaign has already yielded one important discovery: SGR J1745-29, an object called a magnetar. This subclass of neutron star has a magnetic field thousands of times stronger than normal; so far, only 26 magnetars are known. A magnetar orbiting Sgr A may allow scientists to explore important properties of the black hole and test predictions of Einstein’s theory of general relativity.

This sequence from the X-ray Telescope on NASA’s Swift mission shows changes in the central region of the Milky Way galaxy from 2006 through 2013. Watch for flares from binary systems containing a neutron star or black hole and the changing brightness of Sgr A* (center), the galaxy’s monster black hole.

Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)

This sequence from the X-ray Telescope on NASA’s Swift mission shows changes in the central region of the Milky Way galaxy from 2006 through 2013. Watch for flares from binary systems containing a neutron star or black hole and the changing brightness of Sgr A* (center), the galaxy’s monster black hole. Unlabeled.

Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)

This X-ray image of the galactic center merges all Swift XRT observations through 2013. Sgr A* is at center. Low-energy X-rays (300 to 1,500 electron volts) are shown in red, medium-energy (1,500 to 3,000 eV) in green, and high-energy (3,000 to 10,000 eV) in blue. The total effective exposure time is 12.6 days, and the field of view is 25 arcminutes across.Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)

This X-ray image of the galactic center merges all Swift XRT observations through 2013. Sgr A* is at center. Low-energy X-rays (300 to 1,500 electron volts) are shown in red, medium-energy (1,500 to 3,000 eV) in green, and high-energy (3,000 to 10,000 eV) in blue. The total effective exposure time is 12.6 days, and the field of view is 25 arcminutes across.

Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)

This X-ray image of the galactic center merges all Swift XRT observations through 2013. Sgr A* (center) is labeled, as well as several other important sources. The magnetar SGR J1745-29 is so close to Sgr A* that the XRT cannot separate them. GRS 1741.9 and AX J1745.6 are known to be binary systems where one member is a neutron star. The others, all new Swift discoveries, are binaries containing either a neutron star or a black hole. Low-energy X-rays (300 to 1,500 electron volts) are shown in red, medium-energy (1,500 to 3,000 eV) in green, and high-energy (3,000 to 10,000 eV) in blue. The total effective exposure time is 12.6 days, and the field of view is 25 arcminutes across.Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)

This X-ray image of the galactic center merges all Swift XRT observations through 2013. Sgr A (center) is labeled, as well as several other important sources. The magnetar SGR J1745-29 is so close to Sgr A that the XRT cannot separate them. GRS 1741.9 and AX J1745.6 are known to be binary systems where one member is a neutron star. The others, all new Swift discoveries, are binaries containing either a neutron star or a black hole. Low-energy X-rays (300 to 1,500 electron volts) are shown in red, medium-energy (1,500 to 3,000 eV) in green, and high-energy (3,000 to 10,000 eV) in blue. The total effective exposure time is 12.6 days, and the field of view is 25 arcminutes across.

Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)

This simulation shows the future behavior of the G2 gas cloud now approaching Sgr A*, the supermassive black hole at the center of the Milky Way. X-ray emission from the cloud’s tidal interaction with the black hole is expected sometime this spring.

Credit: ESO/MPE/M.Schartmann

For More Information

See http://www.nasa.gov/press/2014/january/nasas-swift-catches-x-ray-action-at-milky-ways-center/

Credits

Please give credit for this item to:
NASA's Goddard Space Flight Center. However, individual items should be credited as indicated above.

This page was originally published on Wednesday, January 8, 2014.
This page was last updated on Wednesday, May 3, 2023 at 1:51 PM EDT.

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