Artist’s impression of exocomets around Beta Pictoris
Beta Pictoris as Seen in Infrared Light
Exoplanet caught on the move
Around Beta Pictoris
*************************************************
Videos
Biggest census ever of exocomets around Beta Pictoris
The HARPS instrument at ESO’s La Silla
Observatory in Chile has been used to make the most complete census of
comets around another star ever created. A French team of astronomers
has studied nearly 500 individual comets orbiting the star Beta Pictoris
and has discovered that they belong to two distinct families of
exocomets: old exocomets that have made multiple passages near the star,
and younger exocomets that probably came from the recent breakup of one
or more larger objects. The new results will appear in the journal
Nature on 23 October 2014.
Beta Pictoris
is a young star located about 63 light-years from the Sun. It is only
about 20 million years old and is surrounded by a huge disc of material —
a very active young planetary system where gas and dust are produced by
the evaporation of comets and the collisions of asteroids.
Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”
For almost 30 years astronomers have seen subtle changes in the light
from Beta Pictoris that were thought to be caused by the passage of
comets in front of the star itself. Comets are small bodies of a few
kilometres in size, but they are rich in ices, which evaporate when they
approach their star, producing gigantic tails of gas and dust that can
absorb some of the light passing through them. The dim light from the
exocomets is swamped by the light of the brilliant star so they cannot
be imaged directly from Earth.
To study the Beta Pictoris exocomets, the team analysed more than 1000 observations obtained between 2003 and 2011 with the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.
The researchers selected a sample of 493 different exocomets. Some
exocomets were observed several times and for a few hours. Careful
analysis provided measurements of the speed and the size of the gas
clouds. Some of the orbital properties of each of these exocomets, such
as the shape and the orientation of the orbit and the distance to the
star, could also be deduced.
This analysis of several hundreds of exocomets in a single
exo-planetary system is unique. It revealed the presence of two distinct
families of exocomets: one family of old exocomets whose orbits are
controlled by a massive planet [1],
and another family, probably arising from the recent breakdown of one
or a few bigger objects. Different families of comets also exist in the
Solar System.
The exocomets of the first family have a variety of orbits and show a
rather weak activity with low production rates of gas and dust. This
suggests that these comets have exhausted their supplies of ices during
their multiple passages close to Beta Pictoris [2].
The exocomets of the second family are much more active and are also on nearly identical orbits [3].
This suggests that the members of the second family all arise from the
same origin: probably the breakdown of a larger object whose fragments
are on an orbit grazing the star Beta Pictoris.
Flavien Kiefer concludes: “For the first time a statistical study
has determined the physics and orbits for a large number of exocomets.
This work provides a remarkable look at the mechanisms that were at work
in the Solar System just after its formation 4.5 billion years ago.”
Notes
[1] A giant planet, Beta Pictoris b, has also been discovered in orbit at about a billion kilometres from the star and studied using high resolution images obtained with adaptive optics.
[2] Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped in orbital resonance
with a massive planet. The properties of the comets of the first family
show that this planet in resonance must be at about 700 million
kilometres from the star — close to where the planet Beta Pictoris b
was discovered.
[3] This makes them similar to the comets of the Kreutz family in the Solar System, or the fragments of Comet Shoemaker-Levy 9, which impacted Jupiter in July 1994.
More information
This research was presented in a paper entitled "Two families of exocomets in the Beta Pictoris system" which will be published in the journal Nature on 23 October 2014.
The team is composed of F. Kiefer (Institut d’astrophysique de Paris
[IAP], CNRS, Université Pierre & Marie Curie-Paris 6, Paris,
France), A. Lecavelier des Etangs (IAP), J. Boissier (Institut de
radioastronomie millimétrique, Saint Martin d’Hères, France), A.
Vidal-Madjar (IAP), H. Beust (Institut de planétologie et
d'astrophysique de Grenoble [IPAG], CNRS, Université Joseph
Fourier-Grenoble 1, Grenoble, France), A.-M. Lagrange (IPAG), G. Hébrard
(IAP) and R. Ferlet (IAP).
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
Alain Lecavelier des Etangs
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC
France
Tel: +33-1-44-32-80-77
Cell: +33 6 21 75 12 03
Email: lecaveli@iap.fr
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC
France
Tel: +33-1-44-32-80-77
Cell: +33 6 21 75 12 03
Email: lecaveli@iap.fr
Flavien Kiefer
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC and School of Physics and Astronomy, Tel Aviv University
France / Israel
Tel: +972-502-838-163
Email: kiefer@iap.fr
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC and School of Physics and Astronomy, Tel Aviv University
France / Israel
Tel: +972-502-838-163
Email: kiefer@iap.fr
Richard Hook
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO
