Artist's impression of Beta Pictoris
Around Beta Pictoris
ALMA image of carbon monoxide around Beta Pictoris (infographic)
ALMA reveals an enigmatic gas clump in debris disc around Beta Pictoris
Astronomers using the Atacama Large
Millimeter/submillimeter Array (ALMA) telescope in northern Chile have
today announced the discovery of an unexpected clump of carbon monoxide
gas in the dusty disc around the star Beta Pictoris. This is a surprise,
as such gas is expected to be rapidly destroyed by starlight. Something
— probably frequent collisions between small, icy objects such as
comets — must be causing the gas to be continuously replenished. The new
results are published today in the journal Science.
Beta Pictoris,
a nearby star easily visible to the naked eye in the southern sky, is
already hailed as the archetypal young planetary system. It is known to harbour a planet that
orbits some 1.2 billion kilometres from the star, and it was one of the
first stars found to be surrounded by a large disc of dusty debris [1].
New observations from ALMA now show that the disc is permeated by carbon monoxide
gas. Paradoxically the presence of carbon monoxide, which is so harmful
to humans on Earth, could indicate that the Beta Pictoris planetary
system may eventually become a good habitat for life. The cometary
bombardment that its planets are currently undergoing is likely
providing them with life-enabling water [2].
But carbon monoxide is easily and rapidly broken up by starlight — it
can only last about 100 years where it is observed in the Beta Pictoris
disc. Seeing it in the 20-million year old Beta Pictoris disc is a
complete surprise. So where did it come from, and why is it still there?
“Unless we are observing Beta Pictoris at a very unusual time, the carbon monoxide must be continuously replenished,”
said Bill Dent, an ESO astronomer at the Joint ALMA Office in Santiago,
Chile, and lead author on a paper published today in the journal
Science. “The most abundant source of carbon monoxide in a young
solar system is collisions between icy bodies, from comets up to larger
planet-sized objects.”
But the rate of destruction must be very high: “To get the amount
of carbon monoxide we observe, the rate of collisions would be truly
startling — one large comet collision every five minutes,” noted Aki Roberge, an astronomer at NASA’s Goddard Research Center in Greenbelt, USA, and coauthor of the paper. “To get this number of collisions, this would have to be a very tight, massive comet swarm.”
But there was another surprise in the ALMA observations, which did
not just discover the carbon monoxide, but also mapped its location in
the disc, through ALMA’s unique ability to simultaneously measure both
position and velocity: the gas is concentrated in a single compact
clump. This concentration lies 13 billion kilometres from the star,
which is about three times the distance of Neptune from the Sun. Why the
gas is in this small clump so far from the star is a mystery.
“This clump is an important clue to what is going on in the outer reaches of this young planetary system,”
says Mark Wyatt, an astronomer at the University of Cambridge, UK, and a
co-author on the paper. He goes on to explain that there are two ways
such a clump can form: “Either the gravitational pull of an as yet
unseen planet similar in mass to Saturn is concentrating the cometary
collisions into a small area, or what we are seeing are the remnants of a
single catastrophic collision between two icy Mars-mass planets”.
Both of these possibilities give astronomers reason to be optimistic
that there are several more planets waiting to be found around Beta
Pictoris. “Carbon monoxide is just the beginning — there may be other more complex pre-organic molecules released from these icy bodies,” adds Roberge.
Further observations are planned with ALMA, which is still ramping up
to its full capabilities, to shed more light on this intriguing
planetary system, and so help us to understand what conditions were like
during the formation of the Solar System.
Notes
[1] Many stars are surrounded by
swirling clouds of dust, known as debris discs.They are the remains of a
collisional cascade of the rocks in orbit around the star, much like
the collisional breakup of the space station depicted in the movie Gravity (but on a much larger scale). Earlier observations of Beta Pictoris were reported in eso1024 and eso0842.
[2] Comets contain ices of carbon monoxide, carbon
dioxide, ammonia and methane, but the majority component is a mixture of
dust and water ice.
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 “Molecular Gas Clumps
from the Destruction of Icy Bodies in the β Pictoris Debris Disk” to
appear in the journal Science on 6 March 2014.
The team is composed of W.R.F. Dent (Joint ALMA Office, Santiago,
Chile [JAO]), M.C. Wyatt (Institute of Astronomy, Cambridge, UK [IoA]),
A. Roberge (NASA Goddard Space Flight Center, Greenbank, USA), J.-C.
Augereau (Institut de Planétologie et d'Astrophysique de Grenoble,
France [IPAG]), S. Casassus (Universidad de Chile, Santiago, Chile), S.
Corder (JAO), J.S. Greaves (University of St. Andrews, UK), I. de
Gregorio-Monsalvo (JAO), A. Hales (JAO), A.P.Jackson (IoA), A. Meredith
Hughes (Wesleyan University, Middletown, USA), A.-M. Lagrange (IPAG), B.
Matthews (National Research Council of Canada, Victoria, Canada) and D.
Wilner (Smithsonian Astrophysical Observatory, Cambridge, USA).
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
Bill DentJoint ALMA Office
Santiago, Chile
Email: wdent@alma.cl
Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO
