NASA / JPL-Caltech
These are the first, focused high-energy X-ray views of the area surrounding the supermassive black hole at the center of our Milky Way galaxy, called Sagittarius A*. The three images on the right side show Sagittarius A* before, during and after an X-ray flare that was spotted in July.
By Alan Boyle
For years, astronomers have known about the supermassive black hole at the center of our Milky Way galaxy, but these pictures from NASA's NuSTAR telescope show a rare view of the usually sleeping giant gobbling down a cosmic snack.
"We got lucky to have captured an outburst from the black hole during our observing campaign," Caltech's Fiona Harrison, the $165 million mission's principal investigator, said today in a NASA news release. "These data will help us better understand the gentle giant at the heart of our galaxy and why it sometimes flares up for a few hours and then returns to slumber."
NuSTAR, also known as the Nuclear Spectroscopic Telescope Array, is an X-ray observatory that was launched in June to study high-energy phenomena such as the tumult that takes place around black holes. Sagittarius A*, which is 4 million times as massive as our sun, is one of the prime targets for observation.
Supermassive black holes like Sagittarius A* commonly form at the center of big galaxies: In fact, they may be an essential piece of the galaxy formation puzzle, and some of them can get pretty violent. Our galaxy's black hole is uncommonly quiet, however, and that's probably a good thing. Only occasionally does matter from the surrounding area fall into its grip. As that matter is sucked into the singularity, it heats up and emits a blast of radiation.
NuSTAR happened to be in the right place at the right time to observe Sagittarius A* for two days in July, along with other observatories. NASA's Chandra X-ray Observatory was watching for lower-energy X-rays, while the Keck Observatory on Hawaii's Mauna Kea was taking infrared images.
During the observations, a bright X-ray flash flared up. The emissions were given off by matter that was heated up to about 180 million degrees Fahrenheit (100 mllion degrees Celsius), NASA said. The high-energy readings are being compared with the images in other wavelengths to deepen astronomers' understanding of how black holes gobble up matter and grow.
"Astronomers have long speculated that the black hole's snacking should produce copious hard X-rays, but NuSTAR is the first telescope with sufficient sensitivity to actually detect them," Columbia University's Chuck Hailey, a member of the mission science team, said in today's statement.
Get ready for a gluttonous orgy
NuSTAR and other black-hole watchers are getting set to watch Sagittarius A*, or Sgr A* for short, go into full gobble mode next year: A huge cloud of dust and gas known as G2 is approaching the black hole, and when it gets close enough, gravitational forces will start pulling material in and heating it up. If July's event was a snack, G2's close encounter will be a gluttonous orgy.
Just this week, researchers at Lawrence Livermore National Laboratory in California released a supercomputer simulation showing how the cloud will be disrupted as it passes by Sgr A*. That simulation suggests that the close encounter will last several months, and that G2 will be totally gone in less than a decade.
Fragile et al. via College of Charleston / LLNL
This three-dimensional volume visualization spans the period 2010 to 2020, showing the cloud of dust and gas known as G2 as it approaches the Sgr A* black hole near the center of the Milky Way galaxy.
"It will just sort of break up into some sort of incoherent structure," Peter Anninos, a computational physicist at Livermore Lab, said in a news release. "Much of it will join the rest of the hot accretion disk around the black hole, or just fall and get captured by the black hole. It will lose a lot of energy, but not all of it. It will become so diffuse that it's unlikely that any remnant of the gas will continue on its orbital track."
Check out this Web page for QuickTime animations showing what scientists think will happen to the cloud, and stay tuned for updates on the dietary preferences of our galaxy's not-always-sleeping giant.
More about black holes:
The G2 computer simulation is the subject of a paper due for publication in The Astrophysical Journal, titled "3D Moving-Mesh Simulations of Galactic Center Cloud G2." In addition to Anninos, the authors include P. Chris Fragile and Julia Wilson of the College of Charleston, as well as Stephen D. Murray of Livermore Lab.
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the?Cosmic Log page?to your Google+ presence. You can also check out?"The Case for Pluto,"?my book about the controversial dwarf planet and the search for new worlds.
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