Planets can survive the death of their stars and become capable of supporting life; Now astronomers will start looking for them.
Stars can’t survive forever, Sun including. In about five billion yearsThe Earth star will begin to consume the hydrogen source it uses to produce energy. nuclear fusion in its core. The Sun’s core will then begin to contract and the temperature will increase so that the hydrogen in its outer shell can then ignite fusion reactions that will cause the Sun and other stars like it to expand once they reach this stage. red giant.
red giant phase bad news for nearby planets. ours solar systemThe expanding sun will swallow Mercury, Venus, and possibly Earth as well.
More distant planets will be better off. Worlds that are five to six times farther away from their stars The world is from the sun It will be heated by the expanding star, melting its ice and forming surface oceans and potentially life. In our solar system, Jupiterlike the icy moons of Europe And in the bootyHe would be in such an important position.
Relating to: Alien life may be detected on planets around dying stars
But this is a good thing. If it is too close, the water will evaporate. If we are too far away, the worlds will remain frozen. In essence, Goldilocks zone Habitability will shift away from an expanding star, and a planet or icy moon would need to inhabit that region to have a chance of developing liquid water.
The red giant star will continue to evolve. Eventually all fusion reactions will cease and the star’s fluffy outer layers will be expelled, leaving behind only the star’s compact core. white dwarf.
White dwarfs are born hot and shine brightly, but they are also very small, about the size of Earth. Their small size means they don’t emit much heat overall. A planet orbiting one of these exotic objects would need to be about 930,000 miles (1.5 million kilometers) away from the white dwarf to be hot enough to host liquid water; that is, about 1% of the distance from the Earth to the sun.
And therein lies the problem. Any nearby planets would have been deep-fried and swallowed long ago, and any now-molten outer planets and moons would be too far from the white dwarf to support surface water.
So how do we transfer a planet hundreds of millions of kilometers away into a new, nearby Goldilocks zone?
“This is a dangerous journey,” said Juliette Becker of the University of Wisconsin-Madison. expression. He stated that “it is difficult for the oceans to overcome this process, but it is possible.”
Becker discussed how outer planets At the 244th meeting of the American Astronomical Society in early June, he announced the mechanism for bringing a planet closer to a white dwarf, where it can survive this process and be detected later via “transits” (transits across the surface of the host star, from our perspective). It is called tidal migration.
“In tidal migration, some dynamic instability between the planets in the system puts one of them in a high eccentric orbit, just like a planet. comet“It swings very close to the central body in the system and then swings very far away again.”
The migrating planet does not stay in this comet-like orbit for long. It keeps the planet close to the white dwarf by making its gravitational path circular. And this is where astronomers can see their transit.
One caveat is that white dwarfs do not appear to be hotbeds of exoplanetary activity. The James Webb Space Telescope (JWST) earlier this year observed two planet candidates around white dwarfs, but overall they are very few. None of these candidates can pass through the white dwarf.
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If a planet is transiting its white dwarf, transit spectroscopy (observing how the planet’s atmosphere absorbs and filters certain wavelengths of starlight during the transit) can reveal the presence of water in that planet’s atmosphere. Such measurements have been made for exoplanets passing in front of normal stars, but it may actually be easier to do this with a white dwarf.
“White dwarfs are so small and so featureless that if a terrestrial planet were to pass in front of them, you could actually do a much better job of characterizing its atmosphere,” Becker said. “The planet’s atmosphere will have a much larger, clearer signal because more of the light you see is passing through exactly what you want to study.”
Water is no guarantee of life, of course, but the mere possibility that previously frozen worlds could be made habitable by the death of their star, and then pulled into a close orbit around that dead star where they could remain habitable, makes this possible. astrobiologists a new field to consider alien life. Such a world could be the ultimate example of a “phoenix” world and prove that life can exist after the death of the stars.
Becker has a paper describing his work on the search for habitable planets passing by white dwarfs that is currently under peer review.