Astronomers Spot First Known Exoplanet To Survive Its Dying Star

'In our new paper, published in Nature, we report the discovery of the first known exoplanet to survive the death of its star without having its orbit altered by other planets moving around -- circling a distance comparable to those between the Sun and the Solar System planets,' writes one of the study's authors, Dimitri Veras, in an article for The Conversation. From the report: This new exoplanet, which we discovered with the Keck Observatory in Hawaii, is particularly similar to Jupiter in both mass and orbital separation, and provides us with a crucial snapshot into planetary survivors around dying stars. A star's transformation into a white dwarf involves a violent phase in which it becomes a bloated 'red giant,' also known as a 'giant branch' star, hundreds of times bigger than before. We believe that this exoplanet only just survived: if it was initially closer to its parent star, it would have been engulfed by the star's expansion. When the Sun eventually becomes a red giant, its radius will actually reach outwards to Earth's current orbit. That means the Sun will (probably) engulf Mercury and Venus, and possibly the Earth -- but we are not sure.

Jupiter, and its moons, have been expected to survive, although we previously didn't know for sure. But with our discovery of this new exoplanet, we can now be more certain that Jupiter really will make it. Moreover, the margin of error in the position of this exoplanet could mean that it is almost half as close to the white dwarf as Jupiter currently is to the Sun. If so, that is additional evidence for assuming that Jupiter, and Mars, will make it. So could any life survive this transformation? A white dwarf could power life on moons or planets that end up being very close to it (about one-tenth the distance between the Sun and Mercury) for the first few billion years. After that, there wouldn't be enough radiation to sustain anything.

The new white dwarf exoplanet was found with what is known as the microlensing detection method. This looks at how light bends due to a strong gravitational field, which happens when a star momentarily aligns with a more distant star, as seen from Earth. The gravity from the foreground star magnifies the light from the star behind it. Any planets orbiting the star in the foreground will bend and warp this magnified light, which is how we can detect them. The white dwarf we investigated is one-quarter of the way towards the centre of the Milky Way galaxy, or about 6,500 light years away from our Solar System, and the more distant star is in the centre of the galaxy.

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