Name: ESOcast 24: 銀河系外起源の最初の惑星 (ESOcast 24: First planet of extragalactic origin)
Uploaded: 2021-01-14T04:59:14.000Z
Duration: 4 min 46 s
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An exoplanet orbiting a star that entered our Milky Way from another galaxy

上級受動態

has been detected by a European team of astronomers.

The Jupiter-like planet is particularly unusual,

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

giving tantalising clues about the fate of our own planetary system

Cutting-edge science and life behind the scenes at ESO

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

In this episode we are going to find out how an act of galactic cannibalism

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

Astronomers have detected nearly 500 planets

orbiting stars in our cosmic neighbourhood,

but none outside our Milky Way has been confirmed.

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

has been discovered orbiting a star of extragalactic origin,

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

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

This stream of stars originally belonged to a dwarf galaxy,

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

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

caused by the gravitational tug of an orbiting companion.

the team used a high resolution spectrograph called FEROS,

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

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

to have survived its host star massively growing in size

after exhausting the hydrogen fuel supply in its core

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

At the closest point in its elliptical orbit,

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

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

and it completes an orbit in only about 16 days.

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

but that it moved inwards during the Red Giant phase.

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

Astronomers suggest that some inner planets

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

has escaped the fate of these inner planets so far,

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

When this happens, the star may engulf the planet,

The astronomers are now searching for more planets

around stars near the end of their lives.

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

as the Sun is also expected to become a Red Giant

This is Dr J signing off for the ESOcast.

Join me again next time for another cosmic adventure.

ESOcast is produced by ESO, the European Southern Observatory.

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

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

Transcription by ESO ; translation by —

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ESOcast 24: 銀河系外起源の最初の惑星 (ESOcast 24: First planet of extragalactic origin)

planet

giant

evolution

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