Few sun-like stars have these huge planets, which makes our sun unusual – ScienceDaily

The location of this landmark is between 3 and 10 times the distance between the Earth and our sun (3 to 10 astronomical units, or AU). Jupiter is at 5.2 AU from our sun.

This is just one of the conclusions of an unprecedented analysis of 300 stars captured by the Gemini Planet Imager, or GPI, a sensitive infrared detector mounted on the 8 meter Gemini South telescope at Chile.

The GPI Exoplanet Survey, or GPIES, is one of two major projects that directly look for exoplanets by blocking starlight and photographing the planets themselves, instead of looking for revealing oscillations in the star – the method radial velocity – or planets crossing in front of the star – the transit technique. The GPI camera is sensitive to the heat released by the newly formed planets and brown dwarfs, which are more massive than the gaseous giant planets, but still too small to ignite the fusion and become stars.

The analysis of the first 300 of the more than 500 stars listed by GPIES, published on June 12 The astronomical journal"is a milestone," said Eugene Chiang, a professor of astronomy at the University of Berkeley and a member of the collaboration theory group. "We now have excellent statistics on the frequency of the planets, their mass distribution and their distance from their stars.This is the most comprehensive analysis I've seen in this domain."

The study complements previous investigations of exoplanets by counting planets between 10 and 100 AU, a range in which it is unlikely that the Kepler Spatial Telescope transit study and radial velocity observations will detect the planets. It was led by Eric Nielsen, a researcher at the Kavli Institute of Astrophysics of Particles and Cosmology at Stanford University, and involved more than 100 researchers from 40 institutions worldwide, including the University of California. 39, University of California at Berkeley.

A new planet, a new brown dwarf

Since the beginning of the GPIES survey, five years ago, the team has imagined six planets and three brown dwarfs in orbit around these 300 stars. The team estimates that about 9% of massive stars have gas giants between 5 and 13 masses of Jupiter beyond a distance of 10 AU and less than 1% have brown dwarfs included between 10 and 100 AU.

The new dataset provides important information on how and where large objects are formed in planetary systems.

"As you come out of the central star, giant planets become more frequent.With 3 to 10 AU, the occurrence rate peaks," said Chiang. "We know the peak hits because Kepler 's surveys and radial velocity show an increase in the rate, from very hot Jupiters near the star to Jupiters to a few UA of the star. bridged at the other end, from 10 to 100 AU, and finding that the rate of occurrence decreases: giant planets are more often than 10 times 100. If you combine everything, there is a low risk of occurrence for a giant planet around 3 to 10 AU. "

"With future observatories, especially the thirty-meter telescope and ambitious space missions, we will begin to visualize the planets that are in the preferred area of ​​the sun's stars," said Paul Kalas, assistant professor of photography. astronomy at the University of Berkeley.

The investigation of exoplanets revealed that only one planet previously unknown – 51 Eridani b, nearly three times the mass of Jupiter – and a previously unknown brown dwarf – HR 2562 B – weighing approximately 26 masses of Jupiter. None of the giant planets pictured were surrounded by sun-like stars. Instead, giant gas planets were only discovered around more massive stars, at least 50% larger than our sun, or 1.5 solar masses.

"Given what we and other investigations have seen so far, our solar system does not look like other solar systems," said Bruce Macintosh, GPI Principal Investigator and Stanford Physics Professor. . "We do not have as many planets stacked as close to the sun as their stars and we now have tentative evidence that another way we might be rare is to have these kinds of planets of Jupiter and more. "

"The fact that giant planets are more common around more massive stars than the stars of the sun is an interesting puzzle," Chiang said.

Since many stars visible in the night sky are massive young stars called A stars, it means that "the stars that you can see in the night sky with your eye are more likely to be surrounded by planets of the mass. of Jupiter as the weaker stars you need.a telescope to see, "said Kalas. "It's pretty cool."

The analysis also shows that gaseous giant planets and brown dwarfs, though apparently on a continuum of growing mass, can constitute two distinct populations that have formed in different ways. The gaseous giants, about 13 times more numerous than the mass of Jupiter, seem to be formed by the accumulation of gas and dust on smaller objects, from the bottom up. Brown dwarfs, between 13 and 80 masses of Jupiter, were formed like stars, by gravitational collapse – from top to bottom – in the same cloud of gas and dust that gave birth to the stars.

"I think it's the clearest evidence that we have these two groups of objects, the planets and the brown dwarfs, form differently," Chiang said. "These are really apples and oranges."

Direct imaging is the future

The Gemini Planet Imager can create a sharp image of planets around distant stars, thanks to highly adaptive optics, which quickly detects turbulence in the atmosphere and reduces fuzziness by adjusting the shape of a planet. flexible mirror. The instrument detects heat from bodies that still shine from their own internal energy, such as large exoplanets, between 2 and 13 times the mass of Jupiter, and young people under 100 million years old. compared to 4.6 billion solar age. years. Although it blocks most of the light from the central star, glare always limits GPI to seeing only the planets and brown dwarfs distant from the stars they orbit, between 10 and 100 AU approximately.

The team plans to analyze data on the remaining stars in the survey, in the hope of better understanding the most common types and sizes of planets and brown dwarfs.

Chiang noted that the success of GPIES shows that direct imaging will become increasingly important in the study of exoplanets, especially to understand their training.

"Direct imaging is the best way to reach young planets," he said. "When young planets form, their young stars are too active, too nervous for radial velocity or transit methods to work easily, but with direct imagery, see, it's believing."

The other members of the UC Berkeley team are post-doc Ian Czekala, Gaspard Duchene, Thomas Esposito, Megan Ansdell and Rebecca Jensen-Clem, astronomy professor James Graham and students Jonathan Lin, Meiji Nguyen and Yilun Ma. The other members of the team include Nielsen, a former undergraduate student at Berkeley, Franck Marchis, a former research assistant, and Marshall Perrin, Mike Fitzgerald, former veteran Jason Wang, Eve Lee and Lea Hirsch graduate students.

The research was funded by the National Science Foundation (AST-1518332), the National Aeronautics and Space Administration (NNX15AC89G) and the Nexus for Exoplanet System Science (NExSS), a research coordination network sponsored by the Directorate of the Mission. NASA scientist (NNX15AD95G).