Discover a planet forming around two stars

Astronomers have found evidence that meteorite fragments revolve around two stars, a sign that a planet is about to be formed.

Although the Earth has only one parent star, the Sun, but most of the other stars the size of the Sun have another star that accompanies it and becomes a binary star system, even three-star or seven-star systems.

The planets that move around the binary star-like system Tatooine in the Star Wars series , and are called circumbinary planet (complete: spin, inter: link many, fine: stars; are spinning around many stars).

In 2011, researchers discovered the first planet moving around two stars , known as Kepler-16b, a giant gas planet orbiting Kepler-16 star 220 light years away.

So far, all planets orbiting binary stars are giant gas planets like Jupiter, but scientists believe there are still rocky planets moving around binary stars. And we have the first evidence.

"The formation of a terrestrial planet that turns two stars is very difficult and takes a long time because it is subjected to the gravitational effects of both stars, the interaction of each other makes it difficult for rocks and dust. gather to form a large mass and develop into a planet, " said the study's lead author, astrophysicist Jay Farihi at the University of London.

The team of scientists found fragments that are remnants of a former planet, moving around this binary star system. "This is a sign that there will be a planet created from here. Moreover, this finding also shows that rocky planets may exist after a star's death , " co-authored. Research, astrophysicist Boris Gänsicke from the University of Warwick, UK, said.

This binary star system is called SDSS 1557 , which is about 1,000 light-years away. Scientists initially thought that it was a white dwarf whose mass was about 40 to 90 times that of the Sun but the same diameter as the Earth, which was left over after a giant star exploded. The sun and 90% of the other stars in the Milky Way will end their lives and become white dwarfs.

Detecting a disk of material from rock debris moving around a binary star system, these two stars orbit each other every 2 hours a round.(Photo: Mark Garlick / UCL).

Using the Large Gemini Observatory and Telescope of the Southern European Observatory located in Chile, the researchers analyzed the spectrum of SDSS 1557. Different wavelengths could tell the composition chemistry and its surroundings.

The researchers found that the high levels of infrared were excessive, suggesting that SDSS 1557 owned a disk of rock debris from a dead planet , mostly silicon and magnesium, located about 1.3 million kilometers away. with the star. The planetary dust disk is estimated at 110 billion tons, small rocks with a diameter of about 4km.

But through long-term observation, co-author Steven Parsons from the University of Sheffield, UK, found that this star often rocked back and forth , making him confirm it is not just a star, but a star system with two stars together.

"This dwarf moves at a rate of about 144,000 km / hour, which is a high speed compared to a single star. It can only happen when it is a two-star system," he said.

"From this observation, we understand how a planet forms from small debris, and how a planetary alien is created in a binary star system , " Gänsicke added.

Researchers predict the turbulent history of this star system. They argue that perhaps in the past, both stars were farther apart than they are today. However, when one of the stars burned off their fuel, it began to swell to make it closer to the other star.

"Now both stars are 482,000 kilometers apart. This distance is not much larger than the distance between the Earth and the Moon. This distance shows that one of the two stars survived the death of the throne. The remaining stars become stars and stars, " Gänsicke added.

Although this finding shows that a new planet will be created, it is difficult to monitor the process of creating the planet.

"The usual method to search for exoplanets is to observe the forward movement of the planet compared to the host star, which causes the star's brightness to be reduced by being obscured by a planet. But light is not applicable because white dwarfs are inherently fuzzy, " Gänsicke said.

Although we can't find much in this star system, we still have new insights into how a planet can develop in a binary star system. In the future, scientists will use the Hubble Space Telescope to analyze ultraviolet light to identify chemical components in small fragments around the star.

And next year, when the James Webb Space Telescope is launched, operational, we can even analyze the detailed chemical composition and specific dimensions of these broken rocks.

This finding leaves many questions for us. How do the fragments make up the planet near the binary star? How can planetary development happen? How can fragments determine its location?