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For the first time, astronomers have been able to directly follow the motion of an exoplanet

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as it moves to the other side of its host star. 

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The planet has the smallest orbit of all directly imaged exoplanets so far,

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lying as close to its host star as Saturn is to the Sun.

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This discovery proves that gas giant planets can form in only a few million years,

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a short time in cosmic terms.

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This is the ESOcast!

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Cutting-edge science and life behind the scenes of ESO, the European Southern Observatory.

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Exploring the ultimate frontier with our host Dr J, a.k.a. Dr Joe Liske.

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Hello and welcome to the ESOcast.

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In this episode, we’ll talk about the planet around the star Beta Pictoris.

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This star has not quite twice the mass of the Sun, and is about 12 million years old.

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Although this sounds like a lot, it’s actually a really young star.

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For example, the Sun is already about 4.7 billion years old.

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Beta Pictoris is one of the best-known examples of a star

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surrounded by a so-called dusty debris disc.

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Now the debris in this disc comes from collisions among larger bodies

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such as planetary embryos or asteroids.

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Earlier observations had already shown that this debris disc is actually warped,

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and that there are comets falling onto the star.

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Now these are telltale signs that strongly suggest the presence of a massive planet

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in orbit around the star.

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Now, with the new observations obtained with ESO’s Very Large Telescope,

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we have definitive proof.

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Because the star is so young,

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the planet must also have formed in only a few million years. 

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This is good news because we already knew that discs around young stars

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disperse in a few million years, 

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and astronomers were looking for proof that giant planet formation can occur within this time.

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The planet has a mass of about 8 Jupiter masses.

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It has the right mass and location to explain the observed warp in the inner parts of the disc.

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The team used the NACO instrument,

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which is mounted on one of the four 8.2-m Unit Telescopes

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of ESO's Very Large Telescope or VLT.

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They observed the immediate neighbourhood of Beta Pictoris in 2003, 2008 and 2009.

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Now the 2003 observations clearly showed a massive planet in the disc,

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but in 2008 and in early 2009, it had disappeared!

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However, in the most recent observations, in late 2009,

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the planet has reappeared, but on the other side of the star.

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Clearly in the earlier observations, the planet was hidden, either in front or behind the star.

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So now, for the first time, we can actually see an exoplanet

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moving around its host star from one side to the other!

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This also gives the astronomers a much better estimate of the distance between the star and the planet.

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Among the handful of planets already imaged,

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the planet around Beta Pictoris, designated “Beta Pictoris b”,

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has the smallest orbit so far.

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It is located between 8 and 14 Earth-Sun distances — or Astronomical Units — from its star.

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This is about the distance Saturn is from the Sun.

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The short period of the planet will allow astronomers to record the full orbit

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within the next 15 to 20 years,

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and further studies of Beta Pictoris b will provide the first insights

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into the physics and chemistry of a young giant planet’s atmosphere.

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Super-Jupiters like Beta Pictoris b are exceedingly rare around Sun-like stars.

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However, the planets found around the stars Fomalhaut and HR8799,

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together with the existence of Beta Pictoris b,

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seems to suggest that super-Jupiters may be a more frequent by-product

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 of the formation of stars that are more massive than the Sun.

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Such planets strongly disturb the discs around their stars,

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and that creates structures that will be easily observable with ALMA,

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which is a revolutionary new millimetre and submillimetre telescope

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that is being built right now by ESO together with international partners.

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A few other exoplanets have been imaged,

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but they are all located farther away from their host star than Beta Pictoris b is.

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If located in the Solar System,

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they would lie close to or beyond the orbit of the farthest planet, Neptune.

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The formation processes of these distant planets

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are likely to be quite different from those in our Solar System and in Beta Pictoris.

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The recent direct images of exoplanets illustrate the diversity of planetary systems.

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Among these, Beta Pictoris b is the most promising case of a planet

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that may have formed in a similar way as the giant planets in our own Solar System.

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This is Dr J signing off for the ESOcast.

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Join me again next time for another cosmic adventure.

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ESOcast is produced by ESO, the European Southern Observatory

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ESO, the European Southern Observatory, is the pre-eminent intergovernmental science and technology organisation in astronomy

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designing, constructing and operating the world’s most advanced ground-based telescopes. 

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Transcription by ESO ; translation by —

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Now that you've caught up with ESO,

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head 'out of this world' with Hubble.

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The Hubblecast highlights the latest discoveries of the world's most recognized and prized space observatory,

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the NASA/ESA Hubble Space Telescope