Nav: Home

ALMA hears birth cry of a massive baby star

June 12, 2017

Stars form from gas and dust floating in interstellar space. But, astronomers do not yet fully understand how it is possible to form the massive stars seen in space. One key issue is gas rotation. The parent cloud rotates slowly in the initial stage and the rotation becomes faster as the cloud shrinks due to self-gravity. Stars formed in such a process should have very rapid rotation, but this is not the case. The stars observed in the Universe rotate more slowly.

How is the rotational momentum dissipated? One possible scenario involves that the gas emanating from baby stars. If the gas outflow rotates, it can carry rotational momentum away from the system. Astronomers have tried to detect the rotation of the outflow to test this scenario and understand its launching mechanism. In a few cases signatures of rotation have been found, but it has been difficult to resolve clearly, especially around massive baby stars.

The team of astronomers led by Tomoya Hirota, an assistant professor at the National Astronomical Observatory of Japan (NAOJ) and SOKENDAI (the Graduate University for Advanced Studies) observed a massive baby star called Orion KL Source I in the famous Orion Nebula, located 1,400 light-years away from the Earth. The Orion Nebula is the closest massive-star forming region to Earth. Thanks to its close vicinity and ALMA's advanced capabilities, the team was able to reveal the nature of the outflow from Source I.

"We have clearly imaged the rotation of the outflow," said Hirota, the lead author of the research paper published in the journal Nature Astronomy. "In addition, the result gives us important insight into the launching mechanism of the outflow."

The new ALMA observations beautifully illustrate the rotation of the outflow. The outflow rotates in the same direction as the gas disk surrounding the star. This strongly supports the idea that the outflow plays an important role in dissipating the rotational energy.

Furthermore, ALMA clearly shows that the outflow is launched not from the vicinity of the baby star itself, but rather from the outer edge of the disk. This morphology agrees well with the "magnetocentrifugal disk wind model." In this model, gas in the rotating disk moves outward due to the centrifugal force and then moves upward along the magnetic field lines to form outflows. Although previous observations with ALMA have found supporting evidence around a low-mass protostar, there was little compelling evidence around massive protostars because most of the massive-star forming regions are rather distant and difficult to investigate in detail.

"In addition to high sensitivity and fidelity, high resolution submillimeter-wave observation is essential to our study, which ALMA made possible for the first time. Submillimeter waves are a unique diagnostic tool for the dense innermost region of the outflow, and at that exact place we detected the rotation," explained Hirota. "ALMA's resolution will become even higher in the future. We would like to observe other objects to improve our understanding of the launching mechanism of outflows and the formation scenario of massive stars with the assistance of theoretical research."

ALMA also imaged rotation of a gas jet from a low-mass protostar. Please read the press release "Baby Star Spits a "Spinning Jet" As It Munches -Down on a "Space Hamburger"" from the Academia Sinica Institute of Astronomy and Astrophysics, Taiwan.
-end-
Paper and research team

These observation results were published as Hirota et al. "Disk-Driven Rotating Bipolar Outflow in Orion Source I" in Nature Astronomy on June 12, 2017.

The research team members are:

Tomoya Hirota (National Astronomical Observatory of Japan / SOKENDAI), Masahiro Machida (Kyushu University), Yuko Matsushita (Kyushu University), Kazuhito Motogi (Yamaguchi University / NAOJ), Naoko Matsumoto (Yamaguchi University / NAOJ), Mi Kyoung Kim (Korean Astronomy and Space Science Institute), Ross A. Burns (Joint Institute for VLBI ERIC), Mareki Honma (NAOJ/SOKENDAI)

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 National Science Council of Taiwan (NSC) 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.

National Institutes of Natural Sciences

Related Astronomers Articles:

Astronomers unveil 'heart' of Eta Carinae
An international team of astronomers has imaged the Eta Carinae star system -- a colossal binary system that consists of two massive stars orbiting each other -- including a region between the two stars in which extremely high-velocity stellar winds are colliding.
Astronomers capture best view ever of disintegrating comet
Astronomers have captured the sharpest, most detailed observations of a comet breaking apart 67 million miles from Earth, using NASA's Hubble Space Telescope.
Astronomers find the first 'wind nebula' around a magnetar
Astronomers have discovered a vast cloud of high-energy particles called a wind nebula around a rare ultra-magnetic neutron star, or magnetar, for the first time.
Astronomers discover 'young Jupiter' exoplanet
The first planet detected by the Gemini Planet Imager is 100 light-years away but shares many of the characteristics of an early Jupiter.
Astronomers discover 'young Jupiter' exoplanet
A team of astronomers that includes University of Georgia professor Inseok Song has discovered a Jupiter-like planet within a young star system that could serve as a decoder ring for understanding how planets formed around the sun.
Astronomers discover 'young Jupiter' exoplanet
An international team of scientists that includes Travis Barman and Katie Morzinski from the University of Arizona has discovered a new exoplanet using the latest planet-hunting tool, the Gemini Planet Imager.
Astronomers discover 'young Jupiter' exoplanet
Astronomers have discovered a Jupiter-like planet within a young system that could serve as a decoder ring for understanding how planets formed around our sun.
Astronomers discover 'young Jupiter' exoplanet
Discovery of a Jupiter-like planet within a young system that could serve as a decoder ring for understanding how planets formed around our Sun.
Astronomers explain why a star is so hot right now
Astronomers have solved a mystery over small, unusually hot blue stars, 10 times hotter than our Sun, that are found in the middle of dense star clusters.
Astronomers unveil the farthest galaxy
An international team of astronomers led by Yale University and the University of California-Santa Cruz have pushed back the cosmic frontier of galaxy exploration to a time when the universe was only 5 percent of its present age.

Related Astronomers Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Moving Forward
When the life you've built slips out of your grasp, you're often told it's best to move on. But is that true? Instead of forgetting the past, TED speakers describe how we can move forward with it. Guests include writers Nora McInerny and Suleika Jaouad, and human rights advocate Lindy Lou Isonhood.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...