​Artist’s impression of the wind from the young solar system TMC1A. The rotating wind is formed in the disc surrounding the protostar.​​
​D. Lamm/BOID and P. Bjerkeli/Chalmers

Newly formed star shoots out powerful whirlwind

Astronomers led by Per Bjerkeli, Chalmers, have used the telescope Alma to observe the early stages in the formation of a new solar system. For the first time they have seen how a powerful whirlwind is launched from a rotating disk surrounding the young star. The results are published on 15 December 2016 in Nature.

A new solar system is formed in a large cloud of gas and dust that contracts and condenses due to the force of gravity. Eventually it becomes so compact that the centre collapses into a ball of gas where the pressure heats the material, resulting in a glowing globe of gas: a star. The remains of the gas and dust cloud rotate around the newly formed star in a disc. The material in the disc starts to accumulate and form larger and larger clumps, which finally become planets.

Close to newly formed stars, called protostars, scientists have observed evidence powerful whirling winds and outflows. But before now, no one had observed how these winds are formed.   

“Using Alma, we have observed a protostar at a very early stage. We see how the wind, like a tornado, lifts material and gas up from the rotating disc, which is in the process of forming a new solar system,” explains Per Bjerkeli, astronomer at Chalmers and the Niels Bohr Institute at the University of Copenhagen, Denmark.  

Slowed down by a tornado

The telescope Alma (Atacama Large Millimeter/submillimeter Array) consists of 66 antennas which observe the universe in light with wavelength around one millimetre from the Chajnantor plateau at 5000 metres altitude in northern Chile. The observed protostar, called TMC1A, is located in the constellation Taurus (the Bull), 450 light years away. The researchers have now observed details never seen before in a system of this kind.

“During the contraction of the gas cloud, the material begins to rotate faster and faster just like a figure skater doing a pirouette spins faster by pulling their arms close to their body. In order to slow down the rotation, the energy must be carried away. This happens when the new star emits a wind. The wind is formed in the disc around the protostar and thus rotates together with it. In this way, when this rotating wind moves away from the protostar, it takes part of the rotational energy with it and the dust and gas close to the star can continue to contract,” explains Per Bjerkeli. 

How is this wind created? Up to now scientists have thought that it could originate from inside the centre of the rotating disc of gas and dust, but the new observations argue for a different origin for the wind.

“We can see that the rotating wind formed across the entire disc. Like a tornado, it lifts material up from the cloud of gas and dust. At some point the wind releases its hold on the cloud, so that the material floats freely. This has the effect that the rotation speed of the cloud is slowed and thus the new star can hold together. In the process, the material in the rotating disc of gas and dust accumulates and forms planets,” explains Jes Jørgensen, also at the Niels Bohr Institute and the Centre for Star and Planet Formation at the University of Copenhagen.  

Future observations with Alma and other telescopes will tell us more about how planetary systems form around protostars like this one, explains Matthijs van der Wiel, astronomer at Astron, Netherlands.

“The next thing we want to find out is whether the material released from the disc is completely blown away or whether it falls back onto the disc at some point and becomes part of the planet-forming system”, he says. 

Contacts

Per Bjerkeli, Department of Earth and Space Science, Chalmers University of Technology and Niels Bohr Institute, University of Copenhagen, +46 7034-13192, per.bjerkeli@chalmers.se

Robert Cumming, communicator, Onsala Space Observatory, Chalmers University of Technology, robert.cumming@chalmers.se,  +46 31 772 5500 or 46 70 493 3114

Images and video:

High-resolution images are available at https://www.flickr.com/photos/onsala/albums/72157676436740150

1 (top): Artist’s impression of the wind emanating from the young solar system TMC1A. The rotating wind is formed in the disc surrounding the protostar. See an animated version of this image at https://vimeo.com/195450409/a1e477bf06. (Credit: D. Lamm/BOID and P. Bjerkeli/Chalmers)
 
2: ALMA’s observations of TMC1A reveal gas motions close to a protostar. Here blue colour indicates gas that is moving towards us while the red colour indicates gas moving away from us. The protoplanetary disc is shown in green. The grey spirals indicate the boundaries of the swirling outflow from the star. The observations, of emission from carbon monoxide molecules, were made with ALMA at 1.3 mm wavelength.  (Credit: ALMA/ESO/NRAO/NAOJ, P. Bjerkeli/Digitized Sky Survey/ESASky)
 
3: The telescope ALMA (Atacama Large Millimeter/submillimeter Array) consists of 66 antennas which observe the universe in light with wavelength around one millimetre from the Chajnantor plateau at 5000 metres altitude in northern Chile. High-resolution image and more information at ESO.​
Credit: S. Otárola/ESO

4: Per Bjerkeli, astronomer at Chalmers and the Niels Bohr Institute, University of Copenhagen, Denmark, has together with colleagues observed the early phases in the formation of a new solar system and have observed how powerful vortices shoot out from the rotating cloud of gas and dust. (Credit: Ola Jakup Joensen, NBI).

More about the research

The research is published in a paper, “Resolved images of a protostellar outflow driven by an extended disk wind”, by P. Bjerkeli et al., in the 15 December 2016 issue of the journal Nature, http://www.nature.com/nature/journal/v540/n7633/full/nature20600.html


More about Alma and Onsala Space Observatory
 
The Atacama Large Millimeter/submillimeter Array (Alma), an international astronomy facility, is a partnership of 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).

Chalmers and Onsala Space Observatory have been involved in Alma since its inception; receivers for the telescope are one of many contributions. Onsala Space Observatory is host to the Nordic Alma Regional Centre, which provides technical expertise to the Alma project and supports astronomers in the Nordic countries in using Alma.

Onsala Space Observatory is Sweden's national facility for radio astronomy. The observatory provides researchers with equipment for the study of the earth and the rest of the universe. In Onsala, 45 km south of Gothenburg, it operates two radio telescopes and a station in the international telescope Lofar. It also participates in several international projects. The observatory is hosted by Department of Earth and Space Sciences at Chalmers University of Technology, and is operated on behalf of the Swedish Research Council.

Published: Wed 14 Dec 2016.