The Milky Way’s Nuclear Star Cluster

The most massive, densest star cluster in the galaxy 

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In this image the infrared light, which is invisible to humans, has been translated into colors our eyes can see. The red stars observed are embedded or shrouded by intervening dust and gas. Areas appearing dark against the bright background stars are actually very dense clouds of gas and dust seen in silhouette. These regions even the infrared eyes of the Hubble Space Telescope can’t penetrate. Credits: NASA/ESA/Hubble

Space news (Into the lair of the Monster of the Milky Way) – the center of the galaxy, 27,000 light-years away – 

Astronomers recently used the Hubble Space Telescope’s infrared vision to observe the lair of the Monster of the Milky Way. Using Hubble’s infrared cameras scientists revealed a dusty galactic core crammed with over an estimated half a million stars. Plus at least ten million stars too faint to be seen by Hubble through the dust in the disk of our island universe. Watch this Spitzer Space Telescope site video “The Hidden Universe: The Galactic Center Revisited“.

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A keyhole-view through Hubble’s looking glass towards the center of the Milky Way through the Sagittarius Star Cloud at a treasure chest full of stars. A treasure chest containing ancient stars that first formed the galaxy with a tale to tell astronomers about the evolution of galaxies.

Part of the Milky Way’s nuclear star cluster, the densest and most massive star cluster in the galaxy, these stars orbit Sagittarius A, a supermassive black hole astronomers believe resides at the center of our galaxy. Called the Monster of the Milky Way, the stars in this cluster are doomed to fall prey to this mysterious object, to be swallowed whole by this 4 million solar mass supermassive black hole. 

The 4-million-solar-mass black hole at the center of the Milky Way.

The bottom panel of this graphic is a view of the region around Sgr A* where red, green, and blue represent low, medium, and high-energy X-rays detected by NASA’s Chandra X-ray Observatory. Sgr A* itself is not visible in this image but is embedded in the white dot at the end of the arrow. The other two telescopes involved in the 15 years of X-ray observations were ESA’s XMM-Newton and NASA’s Swift Gamma Ray Burst Explorer, but their data are not included in this image.

Astrophysicists measured the movements of the stars within the galactic core to determine the mass and structure of the nuclear star cluster. Using these measurements they were able to get a glimpse backward in time to the moment it was formed. To see if it was constructed over time as globular clusters fell into the core of the galaxy or from gas and dust spiraling into the core from the disk to form new stars. 

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This image is meant to show the grand scale of the lair of the Monster of the Milky Way. The storm of stars seen here is actually just the tip of the iceberg, there are at least 10 million stars in this image to faint for Hubble to detect according to estimates by astronomers. Astronomers used the Hubble Space Telescope’s infrared vision to look through the dust in the disk of the Milky Way at its nuclear star cluster. Credits: NASA/ESA/Hubble

Study continues

Astronomers weren’t able to determine which scenario best fits current theory and computer simulations conducted. They continue to modify parameters and devise additional scenarios to explain the formation of the nuclear star cluster. We’ll update you on their findings in future articles. 

Learn more about the Monster of the Milky Way – Sagittarius A

Discover NASA

Take the space journey of the ESA here

Read and learn more about the Milky Way’s nuclear star cluster

Read about the unusual star formation timescale astronomers have observed in dwarf galaxy Leo A.

Check out this artist’s conception of future Europa spacecraft.

Read about Chandra’s detection of X-rays emitted by a distant supermassive black hole.

 

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The Monster of the Milky Way Comes to Life

Erupting X-ray flares every day, a ten-fold increase in bright flares from previous observations of Sagittarius A

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Astronomers believe the ten-fold increase in X-ray flares during the past year could be connected to the passage of a mysterious object designated G2 near the supermassive black hole (Image credit NASA and ESO

Space news (October 01, 2015) – 26,000 light-years from Earth, near the center of the Milky Way

NASA's Chandra X-ray Observatory is part of a new breed of star hunting telescopes.
NASA’s Chandra X-ray Observatory is part of a new breed of star hunting telescopes.

Astrophysicists combining the telescopic talents of NASA’s Chandra X-ray Observatory and Swift spacecraft, with the European Space Agency’s X-ray Space Observatory XMM-Newton, recently detected an increase in X-ray flares erupting from the supermassive black hole (Sagittarius A) at the center of the Milky Way.

NASA's Swift Gamma Ray Burst Explorer scans the universe looking for gamma ray bursts.
NASA’s Swift Gamma Ray Burst Explorer scans the universe looking for gamma ray bursts.

By analyzing data collected during extensive periods of monitoring by all three spacecraft, space scientists determined the Monster of the Milky Way – the supermassive black hole at the center with more than 4 million times the mass of Sol– has been more active during the past 15 years than first thought. 

An artists impression of the ESO's Newton XMM-Newton telescope.
An artists impression of the ESO’s Newton XMM-Newton telescope.

Erupting a bright X-ray flare every ten days, the Monster of the Milky Way has been eating hot gas falling into its gravity pool. Even more interesting, Sagittarius A during the past year has been erupting ten times as much, producing a bright X-ray flare every day. A discovery that has astrophysicists going over the data looking for a reason for the sudden increase. 

“For several years, we’ve been tracking the X-ray emission from Sgr A*. This includes also the close passage of this dusty object” said Gabriele Ponti of the Max Planck Institute for Extraterrestrial Physics in Germany. “A year or so ago, we thought it had absolutely no effect on Sgr A*, but our new data raise the possibility that that might not be the case.”

The mystery started late in 2013, as G2 passed close to the supermassive black hole. At this time, there wasn’t any apparent change in G2 as it approached Sagittarius A, other than being slightly stretched by the gravity pool of the black hole.

Originally astronomers thought G2 was a stretched cloud of gas and dust, but this finding has led scientists to the possibility it could be a dense body embedded in a dusty cocoon. Currently, there’s no consensus among astronomers on the identity of this mysterious object. But the recent ten-fold increase in X-ray flares as G2 passed near the supermassive black hole suggests there could be a connection of some kind. 

“There isn’t universal agreement on what G2 is,” said Mark Morris of the University of California at Los Angeles. “However, the fact that Sgr A* became more active not long after G2 passed by suggests that the matter coming off of G2 might have caused an increase in the black hole’s feeding rate.”

At this point, astronomers don’t know if the increase in X-ray flares from the supermassive black hole is common or unusual in nature. These emissions could be part of the normal life cycle of supermassive black holes and totally unrelated to the passage of G2. The ten-fold increase in X-ray flares could also be due to changing solar winds from nearby massive stars feeding gas and dust into the black hole.

What’s next?

Scientists will keep observing Sagittarius A over the next little while to see what pops up next in this mystery. Hopefully, they can shed some light on the reason the Monster of the Milky Way, suddenly started emitting X-ray flares once a day.  

“It’s too soon to say for sure, but we will be keeping X-ray eyes on Sgr A* in the coming months,” said co-author Barbara De Marco, also of Max Planck. “Hopefully, new observations will tell us whether G2 is responsible for the changed behavior or if the new flaring is just part of how the black hole behaves.”

Read about plans of private firm Planetary Resources, Inc. to mine a near-Earth asteroid in the next decade or less.

Learn more about a magnetar astronomers believe is orbiting extremely close to the supermassive black hole at the center of the Milky Way, Sagittarius A.

Discover the Butterfly Nebula or Twin Jet Nebula.

You can learn more about NASA’s Chandra X-ray Observatory here.

Learn more about the discoveries made by NASA’s Swift spacecraft here.

Discover the European Space Agency’s X-ray Space Observatory XMM-Newton here.

Learn more about the Monster of the Milky Way: Sagittarius A here.

Discover NASA’s mission to the stars here.

Take part in the European Space Agency’s mission to the stars here.

Watch this Nova video on the Monster of the Milky Way.