This exoplanet, the planet outside our solar system, is Jupiter-shaped and is known as WD 1586 b.
It zips around the giant exoplanet star remnant, which is about the size of Earth, in a very close orbit every 34 hours. In comparison, Mercury is the closest planet to the Sun in our solar system and it takes 90 days to complete a revolution around the Sun.
A white dwarf is one that swells a red giant as the sun develops. Red giants burn through their hydrogen fuel and consume any planet near their path. For example, when our Sun turns red giant billions of years ago, it will probably surround Mercury and Venus – and perhaps Earth.
After the star loses its atmosphere, all that remains is the collapsed core – the white dwarf. It remains cold for billions of years.
Finding an intact planet in such a close orbit around a white dwarf raises questions about how it got there, and how it survived the star’s evolution into a white dwarf.
Researchers believe that the planet was far away from its host star and came closer as the star evolved.
Their simulations suggested that when the star became a white dwarf, the planet was kicked close.
The study suggested a theory that large planets could survive the violent evolution of a star and then reach a close orbit.
Ian Crossfield, assistant and assistant professor of physics, said Ian Crossfield, “We think this star died six billion years ago and became a white dwarf about a billion years ago. The Sun, Earth and the Solar System have yet to be formed Did not happen. ” And in an email, astronomy at the University of Kansas.
“Although the star is just a fading ember (only one-ten-thousandth of our Sun), the planet is now likely to be in a stable orbit, so it should be up to us to study it for many years Come learn more. ”
Detecting a dead solar system
NASA’s planet-prey transiting exoplanet survey satellite (TESS) mission was launched in 2018 and has since been sought by nearby stars for exoplanet. This white dwarf is the oldest observation by TESS.
Researchers looked at the planet while searching through data collected by TESS.
“TSE finds a planet looking at a star, and measures how bright the star is for weeks in a row,” Crosfield said. “If a planet is orbiting a star, and if the planet passes between you and the star, then some of that star’s light is going to be blocked. Then the star will accelerate again as the planet passes – we’ll call it ‘transit.’ Of the planet. “
While TESS data can reveal the presence of something, it is not always clear what that object is, he said. It may be a dim star that passes through, instead of a planet.
To help confirm the planet’s discovery, Crosfield used NASA’s Spitzer Space Telescope before its mission ended in January. Spitzer was designed to make infrared observations and to see objects that would otherwise be invisible in visible light.
Infrared light was important in helping scientists determine whether an object was a small star or a large planet. Stars emit infrared light, but planets are colder than stars, so they do not.
“Our Spitzer data showed that there is basically no infrared light,” Crossfield said. “And the depth of these shifts is similar between the TESS data and our Spitzer dataset. In fact, the last nail in the coffin is that this thing is almost a planet rather than a planet.”
Follow-up observations by ground-based telescopes, including some runs by amateur astronomers, helped confirm the discovery.
The planet has no more than 14 times the mass of Jupiter determined by the researchers.
After the planet’s discovery, the researchers ran simulations to determine how the planets reached so close to the star. If the red giant eats planets close in its path, it will destabilize the orbit of the Jupiter-shaped planet, sending it into an elliptical orbit that will bring it closer to the white dwarf, but also far away. .
Over time, this energetic dance slowed, causing the planet to move into a short, tight orbit over billions of years.
When our own sun becomes a red giant, is it possible that the Earth can survive this stellar evolution?
“Our sun will become a white dwarf in about five billion years,” Crossfield said. “There are a lot of open questions about whether planets can survive the process of the star becoming a red giant, swallowing some of the inner planets, and then shrinking back and just leaving as white dwarfs again. can be given.
“Can planets really survive – or is it impossible? And until now, there were no known planets around white dwarfs.”
While it is unlikely that the Earth will survive, “Mars, the asteroid belt and all gas-giant planets will likely survive and live in altered orbits around the remnants of the Sun,” Steven Parsons said in an article with the Nature Study. Parsons, an Ernest Rutherford Fellow in the astronomy group at the University of Sheffield, was not involved in this study.
Can habitable planets exist around dying stars?
Given the size of this planet, it is a gas giant similar to Jupiter in our solar system.
“This is not a good candidate for planetary habitat in particular,” said Andrew Vanderberg, lead study writer and assistant professor in the Department of Astronomy at the University of Wisconsin, Madison. “It’s big enough that it should have a smooth environment made of hydrogen and helium. So it’s not a good place for life as we know it to live.”
Vanderburg said researchers expect the system to last for billions of years as the white dwarf remains cold and “enjoys a long, peaceful retirement.”
However, the discovery of a planet around a white dwarf raises questions about a unique habitable environment that may exist close to the light of a dying star. White dwarfs release light and heat as they cool down, so a close planet may actually be in the habitable zone of the star, or the Goldilocks region where the temperature on the planet is just right for supporting liquid water – and here Even the possible life – – on the surface.
“It tells us that white dwarfs can have planets, which is something we didn’t know before,” Crosfield said. “There are people who are now looking to move planets around white dwarfs that could potentially be habitable. Now we at least know that certain types of planets can survive and be found there , Providing greater support and greater interest in continuing the search. ” Small planets around these white dwarfs. “
This suggests that the dead solar system may actually host hospitable areas, Vanderburg said.
Researchers look forward to exploring smaller planets around white dwarfs in the future, as well as determining more about the planet they have found.
“It seems that the white dwarf system can be a very good place to live, if your planet is in the right side of the system,” Vanderburg said. “So if WD 1856 could make it to this part of the system, it might have included other, smaller planets, including rocky planets that we expect to be the best places for life to exist.”