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The star in question seems to harbor a huge exoplanet. It is one of the few exoplanets directly observed to date. But that may be about to change.
In the meantime, astronomers have already spotted more than 5,000 exoplanets. Most of them, however, are not directly represented. Researchers generally rely on indirect methods, inferring the presence of an exoplanet by looking at the parent star, hoping to momentarily witness the star’s dip in brightness. The Gaia Space Telescope could change that. Because thanks to this satellite, the researchers encountered a “wobbly” star, after which the researchers saw a truly gigantic exoplanet appear before their eyes.
(Indirectly
As mentioned, there are two ways astronomers hunt exoplanets: directly and indirectly. Historically, most exoplanets were discovered by indirect methods. Direct means that a telescope actually sees the planet. Currently, of the thousands of exoplanets we know of, only about twenty have been directly imaged. It is not surprising that there are so few. Exoplanets are extremely difficult to see with existing telescopes. To get a good picture of it, the exoplanet must be far from its parent star and also much more massive than Jupiter, the largest planet in our solar system. And the universe unfortunately does not make many such planets.
flickering stars
But maybe Gaia will make direct observation of exoplanets a little easier now. Using this telescope, astronomers scanned the night sky, looking for stars that literally flickered across the sky. As a planet orbits a star, the star oscillates back and forth, increasing or decreasing its relative speed relative to Earth. Thus, a flickering star can betray the presence of a planet.
After studying the data collected in depth, the researchers have indeed discovered a number of promising flickering stars, which may well be home to a giant planet. Then they turned to the Subaru Telescope, located on the island of Hawaii. And soon after, they spotted a huge exoplanet orbiting the star HIP 99770.
HIP 99770b
The newly discovered exoplanet has been named HIP 99770 b and is about sixteen times the mass of Jupiter, the researchers write in the journal. Science. The exoplanet orbits a star nearly twice as massive as our sun. Although the planet’s orbit is more than three times that of Jupiter around the sun, it receives almost the same amount of light as Jupiter because its parent star is much brighter than ours.
Characterize
With this discovery, the researchers show that with the help of Gaia, it is possible to directly image exoplanets in a much simpler way. And this is an important step forward. Moreover, the discovery of HIP 99770 also has broader implications. “Not only does this show how we can detect more exoplanets, but it also shows how we can better characterize them,” said study co-author Thayne Currie. Indeed, direct and indirect detection methods provide different information about a planet. Using direct methods, astronomers can accurately determine a planet’s temperature and composition. Meanwhile, indirect methods provide accurate measurements of mass and orbit, especially if they are then combined with measurements of the planet’s position by direct observations.
Follow-up studies
In short, combining Gaia data with observations from the Subaru Telescope gives astronomers the best of both worlds. And that’s just the beginning. Now that astronomers know the planet exists and is also visible, other telescopes can take on the task of further analyzing the light. “The discovery of this planet will lead to dozens of follow-up studies,” Currie said.
In addition, many other discoveries are likely to occur. HIP 99770 was one of the first stars to be studied. Currie and his team are currently analyzing data from around 50 other stars. And what they’ve seen so far suggests that more yet-unknown exoplanet discoveries are on the way.
