English subtitles for clip: File:ESOcast 24.webm

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An exoplanet orbiting a star that entered our Milky Way from another galaxy

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has been detected by a European team of astronomers.

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The Jupiter-like planet is particularly unusual, 

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as it is orbiting a star nearing the end of its life

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and could be about to be engulfed by it,

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giving tantalising clues about the fate of our own planetary system 

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in the distant future.

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This is the ESOcast! 

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Cutting-edge science and life behind the scenes at ESO

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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 are going to find out how an act of galactic cannibalism

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 has brought a planet from another galaxy within astronomers’ reach.

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Astronomers have detected nearly 500 planets 

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orbiting stars in our cosmic neighbourhood, 

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but none outside our Milky Way has been confirmed.

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Now, however, a planet weighing at least 1.25 times as much as Jupiter

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has been discovered orbiting a star of extragalactic origin,

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even though the star now finds itself within our own galaxy.

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The star, which is known as HIP13044

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lies about 2000 light-years from Earth and is part of the so-called Helmi stream.

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 This stream of stars originally belonged to a dwarf galaxy,

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which was devoured by our Milky Way 

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in an act of galactic cannibalism six to nine billion years ago. 

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Astronomers detected the planet by looking for tiny telltale wobbles of the star

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caused by the gravitational tug of an orbiting companion.

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For these precise observations, 

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the team used a high resolution spectrograph called FEROS, 

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attached to the 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

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The planet, HIP 13044 b, is also one of the few exoplanets known

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to have survived its host star massively growing in size

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after exhausting the hydrogen fuel supply in its core

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i.e. the Red Giant phase of stellar evolution.

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HIP 13044 b is near to its host star.

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At the closest point in its elliptical orbit, 

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it is less than one stellar diameter from the surface of the star

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(or only about 0.055 times the Sun-Earth distance),

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and it completes an orbit in only about 16 days.

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The astronomers hypothesise 

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that the planet's orbit might initially have been much larger, 

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but that it moved inwards during the Red Giant phase.

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Any closer-in planets may not have been so lucky.

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Astronomers suggest that some inner planets 

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may have been swallowed by the star during its Red Giant phase.

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Although the Jupiter-like exoplanet 

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has escaped the fate of these inner planets so far,

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the star will expand again in the next stage of its evolution.

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When this happens, the star may engulf the planet,

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meaning it may be doomed after all.

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The astronomers are now searching for more planets

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around stars near the end of their lives. 

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Their work may tell us about the distant fate of the planets in our own Solar System,

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as the Sun is also expected to become a Red Giant

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in about five billion years.

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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