Illustration: An artist's imagination shows a tiny rocky planet collapsing while orbiting a white dwarf. In 20 15, astronomers discovered this phenomenon around the white dwarf WD1145+017 by using the data of Kepler K2 mission. The planet will slowly disintegrate, leaving metal fragments on the surface of the star. Source: CfA/Mark A.Garlick.
The astronomer who wrote this paper found unusual spectral lines in the light emitted by white dwarfs. It shows the existence of elements such as iron, oxygen, silicon and magnesium, which are the characteristics of exoplanets. Usually, the spectral lines of white dwarfs show the existence of hydrogen and helium. Any heavier element will be pulled back to the white dwarf by gravity.
Illustration: The spectral analysis of white dwarf WD1145+017 shows that there are metal elements such as iron, silicon, calcium, nickel, magnesium and aluminum, but the abundance is unknown. Source: nature
They also found a debris ring around the white dwarf WD1145+017, which has existed for about 654.38+75 million years.
Illustration: A dust cloud generated by an asteroid orbiting WD1145+017 is simulated. For reference, the size of this rocky asteroid is shown in the upper left corner. The dust formed a relatively strong tail and a weak front tail. Source: nature
The title of this paper is "Planet Death: Simulating Tidal Tearing Events of Differentiated Planetary Matter around WD1145+017". The first author is Kirish Dufry, who was at Wesleyan University at the time of writing this article.
This paper is currently accepted and published in the Journal of Astrophysics. This is the first time that a white dwarf has been found to "eat" its own planet. (Translator's Note: The title of this paper should be "A disintegrating planet with white dwarfs", which was published in the June 20 15 issue of Nature. The first author is Andrew Van der Berg of Harvard Smithsonian Center for Astrophysics. The work of this article published in the Journal of Astrophysics is mainly to model and analyze the properties of disintegrated planets. In the years between writing the paper and publishing it in the Journal of Astrophysics, other researchers also studied WD1145+017 and wrote their own papers.
Overall, this study shows that white dwarfs are devouring their own planet. Not only that, we now know that other 2 1 stars have the same behavior. Generally speaking, this has spawned a new research field, and its name sounds like science fiction-"Planet Death".
Illustration: According to theoretical prediction, when a sun-like star becomes a red giant, the orbits of the planets orbiting it will become unstable and collide with each other to form a disk of dust debris orbiting the red giant. When the star finally becomes a white dwarf, many unstable asteroids land on the star and evaporate. Source: Mark Garlik /space-art. co. uk// University of Warwick.
"... we are observing the death of the planetary system in operation. "
-Dufry et al., 2020.
In the first paper five years ago, the author used the data of Kepler spacecraft, which were collected when Kepler spacecraft found abnormal transit phenomena near WD1145+017. The researchers created 36 different types of planetary models and made 100 simulations to simulate the transit phenomenon observed by Kepler spacecraft lasting 4.5 hours. Then, they compared the simulation results with the observed transit curve. They came to the conclusion that they saw an exoplanet destroyed by a white dwarf under the action of tides.
Illustration: This figure describes the brightness curve shape model of WD1145+017. The red line represents the symmetrical shape of the typical planetary transit, while the blue line represents the asymmetrical shape of the decomposed planetary transit. The black dot is the measured value of K2 task record of WD1145+017. Source: Central Finance Bureau/National Aeronautics and Space Administration.
Their simulation shows that the object most likely to lead to their observation is a rocky planet with a small core and a solid mantle. The author compares them with the asteroid Vesta. These compact celestial bodies have a certain ability to resist the tidal damage of white dwarfs, but from an astronomical point of view, they will be torn apart in a short time.
Illustration: Tidal destruction of planets around white dwarfs. White dwarfs are green dots, while planets are black dots in orange stripes. As time goes by (from A to F), more and more substances fall off the earth. Some of these substances fall into white dwarfs, and some form peristellar disks around stars. Source: Malamud and peretz, 2020.
Essentially, the corpse of the planet observed by the author was torn and landed on a white dwarf, and some substances were sent to a peristellar disk. They wrote in their study: "By combining tidal interference simulation with photometry, we can reveal the internal structure and composition characteristics of exoplanets, and this information is only possible if the planetary system we are observing dies."
These findings show us what may happen in our solar system in the future. Our sun will eventually become a white dwarf like WD1145+017. Before that, it will become a red giant and may devour Mercury, Venus and even the earth. Like all stars that become white dwarfs, a series of violent explosions will eject matter into space. But this planet will survive.
Illustration: The artist's imagination of a red superstar. Before becoming a white dwarf, the sun will go through the red giant stage. Source: NASA/Walter Feimer
Any remaining planets will be in a creepy position: orbiting a white dwarf star, which is only a fraction of the size of the present sun, but extremely dense. Compared with their current orbits, their orbits and those of all other objects in the solar system may be greatly affected. They are likely to be close to white dwarfs and torn by tides, just like planets orbiting WD1145+017.
Now, astronomers know many other white dwarfs, and these white dwarfs also show unusual transit phenomena and spectra. These discoveries opened the door to the study of planetary death. As the author wrote in the paper: "All-weather sky survey missions like TESS and LSST will be able to detect other systems, such as WD1145+017, thus creating a thematic sample for a new sub-field of planetary science:" Planet Death ".