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NASA’s Kepler planet-hunting spacecraft was disabled in November 2018, about ten years after launch. The mission detected more than 5,000 candidate exoplanets and 2,662 confirmed exoplanets using the transit method. But scientists are still working with all of Kepler’s data, hoping to uncover more planets in the observations.
A team of researchers has announced the discovery of another planet in Kepler data, and this one is almost a twin of Jupiter.
The planet is called K2-2016-BLG-0005Lb (sorry), and it’s 17,000 light years away. This is almost twice as far as the next most distant planet discovered by Kepler. Its mass is almost identical to that of Jupiter and it orbits its star at the same distance as Jupiter orbits the Sun. Astronomers found the world in Kepler data from 2016.
Kepler found planets using the transit time method. But he discovered this one differently. He relied on one of Einstein’s predictions; that extremely massive objects have such powerful gravity that they can bend light. This is called gravitational microlensing.
“The probability of a background star being affected in this way by a planet is tens to hundreds of millions to one.”
Dr. Eamonn Kerins, Principal Investigator for the Science and Technology Facilities Council.
A new article titled “Kepler K2 Campaign 9: II. First space discovery of an exoplanet using microlenses” presents the discovery. It is available online at the preprint site arxiv.org and has not yet been peer reviewed. The lead author is Ph.D. student David Specht from the University of Manchester.
The opportunities to detect exoplanets with gravitational microlenses were heightened between April and July 2016 when Kepler was looking at millions of stars towards the center of the Milky Way. In the microlensing technique, astronomers monitor light from a background star bent by the mass of a foreground exoplanet. It’s not easy to do; this requires precise alignment of the background and foreground from Kepler’s perspective.
“To see the effect, you need near-perfect alignment between the foreground planetary system and a background star,” said Dr. Eamonn Kerins, principal investigator for the Science and Technology Facilities Council (STFC) grant. ) who funded this research. “The probability of a background star being affected in this way by a planet is tens to hundreds of millions to one. But there are hundreds of millions of stars towards the center of our galaxy. So Kepler sat and watched them for three months.
Last year, a team of researchers developed a new algorithm to search for microlensing candidates in Kepler data. Some of these same researchers are behind this new study. The researchers developed the algorithm to search for free-floating candidate planets. They found five new candidates, including one that is “…a binary caustic crossover event, consistent with a planet bound,” according to this study.
This effort expanded the possibilities of Kepler data, even though NASA did not explicitly design the mission for the microlens. “Even through a space telescope not designed for microlensing studies, this result highlights the benefits for the discovery of exoplanet microlenses that come from continuous high-rate temporal sampling that is possible from space,” write the authors of the new study.
The 2021 study found “only one candidate exoplanet”, and this new study confirms its candidacy. But in science, each planet is a data point that tells scientists something, now or in the future.
Five ground surveys also examined the same area of sky as Kepler from April to July 2016. Kepler saw the microlens anomaly before them because Kepler is more than 100 million kilometers closer. This delay allowed the researchers to get a better idea of what they were seeing and where they were seeing it.
“The difference in perspective between Kepler and observers here on Earth allowed us to triangulate where the planetary system is along our line of sight,” Dr Kerins said. Kepler’s vantage point above Earth’s atmosphere also allowed him to observe continuously.
“Kepler was also able to observe weather or daylight without interruption, which allowed us to accurately determine the mass of the exoplanet and its orbital distance to its host star,” Dr Kerins said. “It’s basically Jupiter’s identical twin in terms of mass and position relative to its Sun, which is about 60% the mass of our own Sun.”
This study highlights the growing importance of gravitational microlensing in exoplanet science. “Microlensing remains the primary method for detecting cold, low-mass exoplanets, including planets beyond the snow line,” the authors write. The transit method has a built-in sampling bias: it is more likely to detect giant planets close to large stars because the light-blocking signal is more robust. The transit method struggles to identify planets in wider orbits because it can take hundreds of years for multiple transits to occur, and astronomers need multiple transits to confirm exoplanet candidates. The gravitational microlens does not have the same limitations.
But detecting planets like 2-2016-BLG-0005Lb beyond a solar system’s snow line is essential to building our understanding of solar system architecture and bolstering our theories about planet formation. Current thinking shows that high-mass planets form by core accretion past the snow line and then migrate toward the star. (Although some may form due to gravitational instability.) Jupiter probably did, and although Jupiter eventually settled into its orbit beyond the snow line, other planets will not. maybe not. This process explains the high number of hot Jupiters in the exoplanet database.
“The simulations also indicate that lower-mass planets should exist in large numbers beyond the snowline, but that these generally do not migrate from their formation orbit,” the authors write. “By probing
the demography of cold, low-mass exoplanets, so we can directly test predictions of planet formation, without having to take into account the complex dynamics of migration.
Astronomers have proven that gravitational microlensing can detect distant exoplanets, but they won’t have to rely on older Kepler data to use the technique. NASA’s Nancy Grace Roman Telescope is expected to detect thousands of exoplanets using gravitational microlensing. A study showed that it could detect more than 100,000.
“Roman will find planets in other poorly studied categories,” NASA said. “The microlens is best suited for finding worlds from the habitable zone of their star and beyond. This includes ice giants, like Uranus and Neptune in our solar system,” says NASA’s website for the Roman Space Telescope. Some evidence shows that ice giants are the most common type of exoplanet in the galaxy, which makes our own solar system a bit of an outlier with just two of them. “Roman will put this theory to the test and help us better understand which planetary features are most prevalent.”
ESA’s Euclid mission will also use gravitational microlenses. Its main mission is to study dark matter, dark energy and the expansion of the Universe. But it can also detect exoplanets. Euclid and Roman are designed to complement each other, so who knows exactly what we might learn from them.
Dr Kerins is Deputy Head of ESA’s Euclidean Exoplanet Science Working Group. “Kepler was never designed to find planets using microlenses, so in many ways it’s amazing that it did. Roman and Euclid, on the other hand, will be optimized for that kind of They will be able to complete the census of the planet started by Kepler,” he said.
“We will learn how typical the architecture of our own solar system is. The data will also allow us to test our ideas about planet formation. It’s the start of an exciting new chapter in our search for other worlds.
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