The location of a monster embryonic star in the constellation of Norma
Wide-field view of the sky around SDC 335.579-0.292
The birth of a monster star seen at different wavelengths of light
Videos
New observations using the Atacama Large
Millimeter/submillimeter array (ALMA) have given astronomers the best
view yet of a monster star in the process of forming within a dark cloud. A stellar womb with over 500 times the mass of the Sun has been found — the largest ever seen in the Milky Way
— and it is still growing. The embryonic star within the cloud is
hungrily feeding on material that is racing inwards. The cloud is
expected to give birth to a very brilliant star with up to 100 times the
mass of the Sun.
The most massive and brightest stars in the galaxy form within cool and dark clouds but the process remains not just shrouded in dust, but also in mystery [1].
An international team of astronomers has now used ALMA to perform a
microwave prenatal scan to get a clearer look at the formation of one
such monster star that is located around 11 000 light-years away, in a
cloud known as the Spitzer Dark Cloud (SDC) 335.579-0.292.
There are two theories on the formation of the most massive
stars. One suggests that the parental dark cloud fragments, creating
several small cores that collapse on their own and eventually form
stars. The other is more dramatic: the entire cloud begins to collapse
inwards, with material racing towards the cloud’s centre to form one or
more massive behemoths there. A team led by Nicolas Peretto of CEA/AIM
Paris-Saclay, France, and Cardiff University, UK, realised that ALMA was
the perfect tool to help find out what was really happening.
SDC 335.579-0.292 was first revealed as a dramatic
environment of dark, dense filaments of gas and dust through
observations with NASA’s Spitzer Space Telescope and ESA’s Herschel Space Observatory. Now the team has used the unique sensitivity of ALMA to look in detail at both the amount of dust and the motion of the gas moving around within the dark cloud — and they have found a true monster.
“The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud,” says Peretto. “We
wanted to see how monster stars form and grow, and we certainly
achieved our aim! One of the sources we have found is an absolute giant —
the largest protostellar core ever spotted in the Milky Way."
This core — the womb of the embryonic star — has over 500 times the mass of our Sun swirling around within it [2].
And the ALMA observations show that much more material is still flowing
inwards and increasing the mass still further. This material will
eventually collapse to form a young star up to 100 times as massive as
our home star — a very rare beast.
“Even though we already believed that the region was a
good candidate for being a massive star-forming cloud, we were not
expecting to find such a massive embryonic star at its centre,” says Peretto. “This
object is expected to form a star that is up to 100 times more massive
than the Sun. Only about one in ten thousand of all the stars in the
Milky Way reach that kind of mass!”
"Not only are these stars rare, but their birth is
extremely rapid and their childhood is short, so finding such a massive
object so early in its evolution is a spectacular result," adds team member Gary Fuller from the University of Manchester, UK.
Another team member, Ana Duarte Cabral from the Laboratoire d'Astrophysique de Bordeaux, France, emphasises that "the
ALMA observations reveal the spectacular details of the motions of the
filamentary network of dust and gas, and show that a huge amount of gas
is flowing into a central compact region". This strongly supports the theory of global collapse for the formation of massive stars, rather than fragmentation.
These observations formed part of the Early Science phase of ALMA, and have made use of just a quarter of the full array of antennas. “We managed to get these very detailed observations using only a fraction of ALMA’s ultimate potential,” concludes Peretto. “ALMA
will definitely revolutionise our knowledge of star formation, solving
some current problems, and certainly raising new ones.”
Notes
[1] Astronomers use the expression “massive stars” to mean those with roughly ten or more times the mass of the Sun. It refers to the star’s mass, not its size.[2] This star formation region is forming many stars. The 500 solar mass core is the most massive of several.
More information
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 Southern Observatory (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.
This research was presented in a paper entitled “Global collapse of
molecular clouds as a formation mechanism for the most massive stars”,
to appear in Astronomy & Astrophysics.
The team is composed of N. Peretto (CEA/AIM Paris Saclay, France;
University of Cardiff, UK), G. A. Fuller (University of Manchester, UK;
Jodrell Bank Centre for Astrophysics
and UK ALMA Regional Centre Node), A. Duarte-Cabral (LAB, OASU,
Université de Bordeaux, CNRS, France), A. Avison (University of
Manchester, UK; UK ALMA Regional Centre node), P. Hennebelle (CEA/AIM
Paris Saclay, France), J. E. Pineda (University of Manchester, UK; UK
ALMA Regional Centre node; ESO, Garching, Germany), Ph. André (CEA/AIM
Paris Saclay, France), S. Bontemps (LAB, OASU, Université de Bordeaux,
CNRS, France), F. Motte (CEA/AIM Paris Saclay, France), N. Schneider
(LAB, OASU, Université de Bordeaux, CNRS, France) and S. Molinari (INAF,
Rome, Italy).
ESO is the foremost intergovernmental astronomy organisation in
Europe and the world’s most productive ground-based astronomical
observatory by far. It is supported by 15 countries: Austria, Belgium,
Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Portugal, Spain, Sweden, Switzerland and the United
Kingdom. ESO carries out an ambitious programme focused on the design,
construction and operation of powerful ground-based observing facilities
enabling astronomers to make important scientific discoveries. ESO also
plays a leading role in promoting and organising cooperation in
astronomical research. ESO operates three unique world-class observing
sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO
operates the Very Large Telescope, the world’s most advanced
visible-light astronomical observatory and two survey telescopes. VISTA
works in the infrared and is the world’s largest survey telescope and
the VLT Survey Telescope is the largest telescope designed to
exclusively survey the skies in visible light. ESO is the European
partner of a revolutionary astronomical telescope ALMA, the largest
astronomical project in existence. ESO is currently planning the
39-metre European Extremely Large optical/near-infrared Telescope, the
E-ELT, which will become “the world’s biggest eye on the sky”.
Links
Contacts
Nicolas PerettoSchool of Physics and Astronomy, Cardiff University
Cardiff, UK
Tel: +44 29 208 75314
Email: Nicolas.Peretto@astro.cf.ac.uk
Gary Fuller
Jodrell Bank Centre for Astrophysics, University of Manchester
Manchester, UK
Tel: +44 161 306 3653
Email: G.Fuller@manchester.ac.uk
Ana Duarte-Cabral
Laboratoire d'Astrophysique de Bordeaux
Bordeaux, France
Email: Ana.Cabral@obs.u-bordeaux1.fr
Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
