When astronomers discovered the first worlds orbiting other stars 30 years ago, they also started the so-called Galactic Planetary Survey, which tallies the number and types of extrasolar planets in the Milky Way. Although it’s impossible to exhaustively study all the hundreds of billions of stars in our galaxy, a representative sample of them could yield important information. By studying the planetary populations of such samples, researchers can learn what kinds of worlds are most common or rare, and how our Earth and solar system correspond to them. I would like to know
However, there are several different methods for finding planets, each of which tends to be best suited for different kinds of worlds, and can skew the results. We infer the presence of planets by looking for subtle effects of , and are most sensitive to giant planets very close to stars. The orbital “year” of such a world is only a few days or weeks and does not exist in the solar system. In contrast, seeing the planets directly, called a direct image, requires distinguishing them from the overwhelming glare of the stars. If such orbits were around our own Sun, most of these planets would be placed well beyond Pluto.
Fortunately, new methods and broader datasets allow scientists to bridge the gap between these extremes, combining results from multiple planet-hunting techniques to determine the true planetary ensemble of the Milky Way. Get a better, clearer view. New study published in chemistry is one of the first successes of this synergistic approach, and a broader strategy for finding and investigating not only the newly discovered ‘middle of the road’ planets, but many others as well. have earned. The largest and brightest planets yet to be discovered could also be good candidates for future direct imaging efforts, potentially allowing astronomers to discern their atmospheres and climates.
“Combined [motion and imagery] Thane Curry, planet hunter at NASA’s Ames Research Center and lead author of the study, said:
catch the star
Curry and his colleagues will compare data on star motion collected in 2021 by the European Space Agency’s Gaia spacecraft with similar measurements made in the early 1990s by Gaia’s predecessor, Gaia. has discovered a new planet, a giant world called HIP 99770b. , ESA’s Hipparcos satellite. Both Gaia and Hipparchus aimed to map the stars (rather than the planets) of the Milky Way using a technique called astrometry to accurately track the positions, distances and movements of stars. But astronomical observations can also reveal planets. A planet orbiting a star can cause the star’s position to change very slightly and periodically, causing it to oscillate back and forth in the plane of the sky. By identifying the magnitude and repetition of that change, astronomers can determine the mass and orbit of the invisible planet.
The initial discovery of the planet and its photographic follow-up were only possible thanks to decades of Gaia-Hipparcos data that enabled detection of the long orbit of HIP 99770 b. The combined catalog itself was years in the making. After Gaia’s first data were released in 2016, Timothy Blunt, an astronomer at the University of California, Santa Barbara, and a co-author of the new study, identified tens of thousands of stars that he augmented by matching the previous Hipparcos. Published the list. It will be updated again in 2021 after the latest Gaia data is released. The result is a window of roughly 25 years on how these stars have moved across the sky.
Several teams have begun excavating a new database of stellar companions, says Caroline Morley, a researcher at the University of Texas at Austin who studies the atmospheres of exoplanets. Part of new research.
For HIP 99770 b, the Gaia-Hipparcos data showed it to be a gas giant orbiting a star a little further from the Sun than Uranus. Range of direct imaging. Follow-up observations conducted using his SCExAO direct imager on the Subaru Telescope at Mauna Kea, Hawaii, confirmed these suspicions, revealing the planet as a spot clouded with molecules of water vapor and carbon monoxide. rice field. Climate models suggest that the Earth’s temperature is between 1,300 and 1,400 Kelvin (1,880 to 2,060 Fahrenheit). Though decidedly eerie, HIP 99770 b’s properties as a whole make it a relatively close cousin to Earth.
“It is the first time [finding from this database] “You can really argue that this is probably the mass of the planet,” says Beth Biller, who was not part of the research team. is in the gray area between a planet and a brown dwarf, pointing out that some might object to classifying it as a planet. minimum mass,” she says.
worth a thousand words
Results like these help fill a lingering gap in planetary surveys of our galaxy. In addition to being limited to very large planets in very broad orbits, current direct imaging efforts are very young (between 10 and 100 million years old) and still hot at the time of formation. Perfect for a world that still shines. Biller said the cumulative results of all these previous studies were significant, but still not overwhelming. “What we found [hot, young, wide-orbiting] Giant planets are very rare,” she says.
Many stars are expected to have planets in their orbits, but direct imaging studies have found far fewer stars with giant planets in their limbs. Thermal imaging reveals insight into the atmospheres of these worlds, and models provide estimates of their mass. Of the dozens of exoplanets captured by direct imaging, astronomers have only been able to narrow down the masses of two more precisely using tracking measurements from indirect planet detection techniques. is partly due to the existing observational preference for young planets, and correspondingly having much more active young host stars than more mature stars, which makes star-based measurements of companion mass It is more destructive to
“Once you get a directly imaged planet, there’s a certain amount of guesswork in corroborating its physical properties,” says Brandt. Fusing astrometry with direct imaging not only helps us find more targets. It also eliminates some of this guesswork by revealing the orbit and mass of each newly discovered planet, as well as its atmosphere.
Gaia targets 2 billion stars, while Hipparchus has studied only 100,000, all of which are relatively bright and close to Earth. Currie estimates that about one-third of the stars studied in the combined catalog have companion stars, most of which are low-mass stars. If only one-hundredth of the cataloged stars that have companions have photogable planets, a new fusion of planet detection methods could dramatically increase the total number of worlds that astronomers can immediately see directly. should increase. According to the researchers, by the end of his decade-long search, Gaia was able to identify as many as 100 additional planets as candidates for direct imaging using current equipment. That’s more than four times as many of the directly imaged worlds identified so far. And this will extend our knowledge of the planetary system not only to the youngest and brightest, but perhaps even more worlds like ours.
“The yield of new discoveries is higher than if we did a blind search,” says Currie.
