“Unlikely New Discovery” –Stars Like Our Sun Exist in Milky Way’s Violent Supermassive Black Hole Region (VIDEO)

 

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At the center of our galaxy, in the immediate vicinity of its supermassive black hole, is a region wracked by powerful tidal forces and bathed in intense ultraviolet light and X-ray radiation. These harsh conditions, astronomers surmise, do not favor star formation, especially low-mass stars like our sun. Surprisingly, new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile suggest otherwise.


ALMA has revealed the telltale signs of eleven low-mass stars forming perilously close—within three light-years—to the Milky Way's supermassive black hole, known to astronomers as Sagittarius A* (Sgr A*). At this distance, tidal forces driven by the supermassive black hole should be energetic enough to rip apart clouds of dust and gas before they can form stars.

 

 

 

An ALMA image of the center of the Milky Way galaxy showing the location of 11 young protostars within about 3 light-years of our galaxy's supermassive black hole. The lines indicate the direction of the bipolar lobes created by high-velocity jets from the protostars. The illustrated star in the middle of the image indicates the location of Sagittarius A*, the 4 million solar mass supermassive black hole at the center of our galaxy. The next image is a zoom-in to one of the protostars.

 

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The presence of these newly discovered protostars (the formative stage between a dense cloud of gas and a young, shining star) suggests that the conditions necessary to birth low-mass stars may exist even in one of the most turbulent regions of our galaxy and possibly in similar locales throughout the universe.

"Despite all odds, we see the best evidence yet that low-mass stars are forming startlingly close to the supermassive black hole at the center of the Milky Way," said Farhad Yusef-Zadeh, an astronomer at Northwestern University in Evanston, Illinois, and lead author on the paper. "This is a genuinely surprising result and one that demonstrates just how robust star formation can be, even in the most unlikely of places."

The ALMA data also suggest that these protostars are about 6,000 years old. "This is important because it is the earliest phase of star formation we have found in this highly hostile environment," Yusef-Zadeh said.
The team of researchers identified these protostars by seeing the classic "double lobes" of material that bracket each of them. These cosmic hourglass-like shapes signal the early stages of star formation. Molecules, like carbon monoxide (CO), in these lobes glow brightly in millimeter-wavelength light, which ALMA can observe with remarkable precision and sensitivity.

Protostars form from interstellar clouds of dust and gas. Dense pockets of material in these clouds collapse under their own gravity and grow by accumulating more and more star-forming gas from their parent clouds. A portion of this infalling material, however, never makes it onto the surface of the star. Instead, it is ejected as a pair of high-velocity jets from the protostar's north and south poles.

Extremely turbulent environments can disrupt the normal procession of material onto a protostar, while intense radiation—from massive nearby stars and supermassive black holes—can blast away the parent cloud, thwarting the formation of all but the most massive of stars.

The Milky Way's galactic center, with its 4 million solar mass black hole, is located approximately 26,000 light-years from Earth in the direction of the constellation Sagittarius. Vast stores of interstellar dust obscure this region, hiding it from optical telescopes. Radio waves, including the millimeter and submillimeter light that ALMA sees, are able to penetrate this dust, giving radio astronomers a clearer picture of the dynamics and content of this hostile environment.

Prior ALMA observations of the region surrounding Sgr A* by Yusef-Zadeh and his team revealed multiple massive infant stars that are estimated to be about 6 million years old. These objects, known as proplyds, are common features in more placid star-forming regions, like the Orion Nebula. Though the galactic center is a challenging environment for star formation, it is possible for particularly dense cores of hydrogen gas to cross the necessary threshold and forge new stars.

The Daily Galaxy via ALMA Observatory

Image Credit: ALMA (ESO/NAOJ/NRAO), Yusef-Zadeh et al.; B. Saxton (NRAO/AUI/NSF)

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