News Feature: March 18, 2019 at 3:04 pm EDT
Image Release: ALMA Shows Birth of Spiraling Giants
Witnessing the birth of a massive binary star system
ALMA Image Protostars
Credit: ALMA (ESO/NAOJ/NRAO); RIKEN, Zhang et al.
Using the Atacama Large Millimeter/submillimeter Array (ALMA)Atacama Large Millimeter/submillimeter Array (ALMA)Funded by the U.S. National Science Foundation and its international partners (NRAO/ESO/NAOJ), ALMA is among the most complex and powerful astronomical observatories on Earth or in space. The telescope is an array of 66 high-precision dish antennas in northern Chile. See more here, astronomers have observed the formation and mutually entwined motions of a massive binaryBinaryTwo stars in the same system that orbit around a common center of mass due to their mutual gravity. Binary stars are twins in the sense that they formed together out of the same interstellar cloud. Most stars in our galaxy have a binary companion. star system.
The results, published in Nature Astronomy, provide strong evidence that the two sibling stars formed as the result of disk fragmentation – or the breaking apart of a protoplanetary diskprotoplanetary diskThe swirling disk of dust and gas that collapsed from a much larger cloud of material that will eventually evolve into a fully fledged planetary system. Features in the disk may already herald the presence of young planets. [caption id="attachment_11841" align="alignnone" width="300"] ALMA Observatory image of the young star HL Tau and its protoplanetary disk. This best image ever of planet formation reveals multiple rings and gaps that herald the presence of emerging planets as they sweep their orbits clear of dust and gas. Credit: ALMA(ESO/NAOJ/NRAO); C. Brogan, B. Saxton (NRAO/AUI/NSF)[/caption] to form a pair of massive stars in orbit around each other.
"Massive stars are important throughout the universe, including for producing the heavy elements that make up our Earth and are in our bodies, but their formation mechanism is literally shrouded in mystery, being so deeply embedded in dusty clouds," said Jonathan Tan, an astronomer at the University of Virginia in Charlottesville, Virginia, and co-author on the paper.
Unlike our solitary Sun, many star systems, particularly massive star system, form in pairs. But questions remain about how these binary systems form and evolve: Are the stars born together from a common spiraling gas disk at the center of a collapsing cloud or do they pair up later by chance encounters in a crowded star cluster?
Answering this question has been difficult because the protostars in these systems are still enveloped in a thick cloud of gas and dust. Longer millimeter-wavelength light, however, is able to pass through the dust, enabling ALMA to observe star-forming regions in amazing detail. The new observations show that even at this early stage of development, the cloud contains both a massive "primary" central star and another "secondary" high-mass star.
The system, known as IRAS07299-1651, is located about 5,500 light-years from Earth. The two protostars are quite far apart — about 180 astronomical unitsAstronomical unitAstronomical unit (AU): A unit of distance equal to the average distance between the Earth and the Sun, or 149.6 million kilometers (93 million miles). , or about six times the distance from the Sun to Neptune, but because the system is very distant, this corresponds to a very small angular separation. The new ALMA data show they orbit about once every 600 years and they have a combined mass at least 18 times that of our Sun.
The full news release can be read here: https://www.almaobservatory.org/en/press-release/spiraling-giants-witnessing-the-birth-of-a-massive-binary-star-system/
Contact: Charles E. Blue: Public Information Officer
cblue@nrao.edu; 434-296-314
Reference: Yichen Zhang, Jonathan C. Tan, Kei E. I. Tanaka, James M. De Buizer, Mengyao Liu, Maria T. Beltrán, Kaitlin Kratter, Diego Mardones and Guido Garay, Dynamics of a massive binary at birth, Nature Astronomy (2019), doi: 10.1038/s41550-019-0718-y
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
ALMA image of the IRAS-07299 star-forming region and the massive binary system at its center. The background image shows dense, dusty streams of gas (shown in green) that appear to be flowing toward the center of the system. Gas that is moving toward us -- as traced by the methanol molecule -- is shown in blue; motions away from us in red. The inset image shows a zoom-in view of the massive forming binary, with the brighter, primary protostar moving toward us shown in blue and the fainter, secondary protostar moving away from us shown in red. The blue and red dotted lines show an example of orbits of the primary and secondary spiraling around their center of mass (marked by the cross).
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