Finding real Tatooines in real life
Scientists have studied data from our TESS telescope and discovered more than two dozen planets that orbit pairs of stars! On Star Wars Day, learn more about how these planets form outside our solar system.
For NASA's TESS spacecraft, stellar eclipses shed light on possible new worlds
A study of data from NASA's TESS (Transiting Exoplanet Survey Satellite) satellite, dedicated to pairs of stars experiencing mutual eclipses, has revealed more than two dozen candidates for exoplanets, or worlds beyond our solar system. This method allows the mission to find planets that it would not be able to detect otherwise.
A gas giant is visible in the foreground to the right, illuminated by a pair of stars, in this artist's rendering of a world in a binary star system. NASA's TESS (Transiting Exoplanet Survey Satellite) discovered planets in two binary star systems by observing the dimming of stars as planets pass in front of one of the stars. Now, astronomers have demonstrated a new method for finding planets in these systems by focusing on the timing of mutual eclipses of stars.NASA Goddard Space Flight Center/Chris Smith (USRA)
To date, TESS has discovered 885 confirmed exoplanets and has identified more than 7,900 candidates, almost all of which were discovered by planets passing in front of their stars from our perspective. These events, called transits, cause a small, regular decrease in the brightness of the planet's host star.TESS also observes tens of thousands of eclipsing binaries—two orbiting stars that alternately eclipse each other from our vantage point. Astronomers can detect the gravitational pull of exoplanets in these systems by carefully measuring the exact timing of many eclipses. Prior to the new study, discoveries made by NASA's completed Kepler mission and other telescopes had detected 16 transiting worlds around binary stars. stars, while TESS discovered two more.
“Detecting transits in binary systems is certainly challenging, but we would like to learn more about the range of planets that can form around two gravitationally bound stars,” said study leader Margot Thornton, a PhD student at the University of New South Wales (UNSW) in Sydney. “So we developed a method for finding planets using stellar eclipses that is not limited by the orientation of the planet's orbit.”
For planets in binary systems, the orientation of the planet's orbit can tell us how the system formed. Some models of planet formation in binary systems suggest that planets primarily form near the plane formed by the two orbiting stars, increasing the likelihood that binary systems will host transiting planets. But other models point to a much more chaotic formation process, in which the star pair dissects its young planets along wider and more inclined trajectories, greatly reducing the likelihood of transits.
The timing of stellar eclipses can gradually change due to tidal and rotational interactions between stars, the effects of general relativity, and the presence of other invisible masses in the system, such as planets.All these forces cause the entire orbital plane of the binary system to rotate, or precession, which in turn changes the timing of the eclipse.
“The key to calculating all these different factors is the extensive and long-term set of observations available through the TESS telescope,” said co-author Benjamin Monte, assistant professor of science at the University of New South Wales Sydney. “After analyzing 1,590 binary systems with at least two years of TESS data, we found 27 planet candidate systems that are now awaiting confirmation.”
Learn how observing stellar eclipses could expand the capabilities of NASA's TESS telescope, leading to the discovery of new planet candidates that it might not otherwise discover.NASA Goddard Space Flight Center/Francis Reddy
Since the start of scientific research in 2018, TESS has been observing the sky for almost a month, covering large areas called sectors. Currently, the mission's cameras receive a single image of the entire 24 by 96 degree sector approximately every 3 minutes, and observations of selected objects are carried out even faster.
The masses of the new candidates remain uncertain, but the team suggests that the smallest world could contain just 12 Earth masses, while the largest could contain about 3,200 Earth masses, or about 10 times the mass of Jupiter.Confirming the existence of these planets will require future ground-based observations that accurately measure the velocities of their host stars, revealing the weak gravitational pull of any possible planets.
“The TESS mission was designed to search for transiting planets, and it's exciting to see how those same measurements lead to discoveries far beyond the scope of the original mission,” said Allison Youngblood, TESS project scientist at NASA Goddard Space Flight Center in Greenbelt, Maryland. “The mission's ongoing data collection is a treasure trove of information, enabling new discoveries on a wide range of astronomical topics, from asteroids in the solar system to active galaxies fueled by black holes in the distant Universe.”
You can discover the next exoplanet! Join the citizen science projectPlanet Hunters TESSand you'll learn to read light curves—graphs of light data from distant stars—to find signature signals from exoplanetsorbiting them.