Artist's impression of an accretion burst in a high-mass young stellar object like S255 NIRS 3.
Image Credit: Deutsches SOFIA Institut (DSI).
Full resolution JPEG
Astronomers using critical observations from the Gemini Observatory have
found the strongest evidence yet that the formation of more massive
stars follow a path similar to their lower-mass brethren - but on
steroids!
The new findings, that include data from Gemini, SOFIA, Calar Alto, and
the European Southern Observatory, show that the episodic explosive
outbursts within what are called accretion disks, known to occur during
the formation of average mass stars like our Sun, also happen in the
formation of very massive stars.
"These outbursts, which are several orders of magnitude larger than
their lower mass siblings, can release about as much energy as our Sun
delivers in over 100,000 years," said Dr. Alessio Caratti o Garatti of
the Dublin Institute for Advanced Studies (Ireland). "Surprisingly,
fireworks are observed not just at the end of the lives of massive
stars, as supernovae, but also at their birth!"
The international team of astronomers (led by Caratti o Garatti) published their work in the November 14th issue of the journal Nature Physics,
presenting the first clear case that massive stars can form from clumpy
disks of material – in much the same way as less massive stars.
Previously it was thought that the accretion disks seen around lower
mass stars would not survive around stars of higher mass due to their
strong radiation pressure. Therefore, some other process would be
necessary to account for the existence of more massive stars – which can
exceed 50-100 times the mass of our Sun.
"How accretion disks can survive around these massive stars is still a
mystery, but the Gemini spectroscopic observations show the same
fingerprints we see in lower mass stars," said Caratti o Garatti.
"Probably the accretion bursts reduce the radiation pressure of the
central source and allow the star to form, but we still have a lot of
explaining to do in order to account for these observations."
According to team member Dr. Bringfried Stecklum of the Thüringer
Landessternwarte Tautenburg (Germany), "Studying the formation of
high-mass stars is challenging because they are relatively rare and
deeply embedded in their natal cloud, thus not visible in optical, or
visible, light. This is why we need infrared instruments like the
Near-infrared Integral Field Spectrograph at Gemini North on Maunakea in
Hawai‘i." The outburst events are also very rapid, probably lasting
only a few years or less - which, for a star, is the blink of an eye,
adding to their rarity.
"The birth of truly massive stars has been a mystery that astronomers
have been studying for decades. Only now, with large, infrared-optimized
telescopes like Gemini, are we able to probe the details of this
short-lived and, now it seems, rather explosive process," notes Chris
Davis, Program Director at the National Science Foundation which
supports the operation of the Gemini Observatory and the development of
its instruments. "These NIFS observations represent yet another coup for
the Gemini Observatory."
The developing star observed in this study, S255IR NIRS 3, is relatively
distant, some 6,000 light years away, with a mass estimated at about 20
times the mass of our Sun. The Gemini observations reveal that the
source of the explosive outburst is a huge clump of gas, probably about
twice the mass of Jupiter, accelerated to supersonic speeds and ingested
by the forming star. The team estimates that the outburst began about
16 months ago and according to Caratti o Garatti it appears that the
outburst is still active, but much weaker.
"While low-mass stars, and possible planetary systems, can form
basically next door to our Sun, the formation of high-mass stars is a
complex and relatively rapid process that tends to happen rather far
away in our galaxy, thousands, or even tens of thousands of light years
away," said Caratti o Garatti. He adds that the formation of these
massive stars happens on timescales of 100,000 years, whereas it takes
hundreds of times longer for lower mass stars like our Sun to form.
"When we study the formation of higher mass stars it's like watching a
timelapse move when compared to less massive stars, although the process
for massive stars is fast and furious, it still takes tens of thousands
of years!"
"While this research presents the strongest case yet for similar
formation processes for low and high mass stars, there is still lots to
understand," concludes Stecklum. "Especially whether planets can form in
the same way around stars at both ends of the mass spectrum."
Science Contacts:
- Alessio Caratti o Garatti
Dublin Institute for Advanced Studies
Email: alessio@cp.dias.ie
Office: +353 1 4406656 ext.342
Cell: +353 87 1091628
- Bringfried Stecklum
Thüringer Landessternwarte Tautenburg
Email: stecklum@tls-tautenburg.de
Office: +49 36427 863
Cell: +49 179 38088401
Media Contact:
-
Peter Michaud
Gemini Observatory
Hilo, Hawai‘i
Email: pmichaud@gemini.edu
Cell: (808) 936-6643
Source: Gemini Observatory
