From ALMA: “ALMA Discovers Infant Stars Surprisingly Near Galaxy’s Supermassive Black Hole” ALMA Contact has been added in

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

ALMA

28 November, 2017
Valeria Foncea Rubens
Education & Public Outreach Officer (EPO)
Alonso de Córdova 3107
Vitacura 763-0355, Santiago – Chile
T: 56 2-224676258 / 97-5871963

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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) 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*).

SGR A* NASA’s Chandra X-Ray Observatory

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.

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.

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Double-lobe feature produced by jets from newly forming star near the galactic center. ALMA discovered 11 of these telltale signs of star formation remarkably close to the supermassive black hole at the center of our galaxy.
Credit: ALMA (ESO/NAOJ/NRAO), Yusef-Zadeh et al.; B. Saxton (NRAO/AUI/NSF)

NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

The results are published in The Astrophysical Journal Letters.

“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, creating a cosmic hourglass-like shape of gas that signals 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.

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Infant stars, like those recently identified near the supermassive black hole at the center of our galaxy, are surrounded by a swirling disk of dust and gas. In this artist’s conception of infant solar system, the young star pulls material from its surroundings into rotating disk (right) and generates outflowing jets of material (left). Credit: Bill Saxton (NRAO/AUI/NSF)

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, however, 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 25,000 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.

Orion Nebula M. Robberto NASA ESA Space Telescope Science Institute Hubble

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, despite the extreme conditions.

The new ALMA observations, however, revealed something even more remarkable, signs that eleven low-mass protostars are forming within 1 parsec – a scant 3 light-years – of the galaxy’s central black hole. Yusef-Zadeh and his team used ALMA to confirm that the masses and momentum transfer rates – the ability of the protostar jets to plow through surrounding interstellar material – are consistent with young protostars found throughout the disk of our galaxy.

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An ALMA image of the center of the Milky Way galaxy revealing 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 star indicates the location of Sagittarius A*, the 4 million solar mass supermassive black hole at the center of our galaxy.
Credit: ALMA (ESO/NAOJ/NRAO), Yusef-Zadeh et al.; B. Saxton (NRAO/AUI/NSF)

Additional Information

The research team was composed by F. Yusef-Zadeh[1], M. Wardle[2], D. Kunneriath[3], M. Royster[1], A. Wootten[3] & D. A. Roberts[1]

[1] Department of Physics and Astronomy Northwestern University, Evanston, IL 60208

[2] Dept of Physics and Astronomy, Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney NSW 2109, Australia

[3] National Radio Astronomy Observatory, Charlottesville, VA 22903 4Fort Worth Museum of Science and History, Fort Worth, TX 76107

See the full article here .

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The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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