NASA’s TESS Mission Finds Planetary System in New Way

5 Min Read NASA’s TESS Mission Finds Planetary System in New Way This artist’s concept visualizes a super-Jupiter orbiting an orange dwarf star at a distance similar to Jupiter’s distance from the Sun. Credits: NASA’s Goddard Space Flight Center For the first time, NASA’s TESS (Transiting Exoplanet Survey Satellite) mission has identified a planet orbiting a distant star thanks to ripples in space-time. Unlike the star-hugging transiting planets TESS regularly reveals, the newfound world is a super-Jupiter orbiting far from its host star. “When TESS launched, no one expected it to ever be capable of finding this kind of planet,” said Diana Dragomir, a professor at the University of New Mexico in Albuquerque and co-author of a paper describing the results. At 1.6 times Jupiter’s mass and a similar orbital distance, it would be extremely unlikely to find such a planet via the primary detection method TESS was designed for. “The discovery implies that there are probably other so-called microlensing planets hiding in TESS’s data that we hadn’t previously thought to look for.” This artist’s concept visualizes Gaia23bra b, the first microlensing planet orbiting a distant star found by NASA’s TESS (Transiting Exoplanet Survey Satellite). This super-Jupiter orbits an orange dwarf star at a distance similar to Jupiter’s distance from the Sun. NASA’s Goddard Space Flight Center Astronomers found the first hint of the planet, called Gaia23bra b, in 2023 using ESA’s (European Space Agency) now-retired Gaia space telescope. Gaia’s alert system flagged a star that brightened — something that can happen when a foreground star passes in front of a more distant one and magnifies its light through gravitational microlensing. Researchers later looked back through archived TESS data and found TESS had caught it too. “Gaia’s observations were too sparse to pick up on the planet,” said Mallory Harris, a Ph.D. candidate at the University of New Mexico, who led the study. “The TESS spacecraft happened to be monitoring the same area of the sky during the event, and its denser time coverage showed extra features in the light curve caused by a planet.” The team’s analysis, published July 1 in The Astrophysical Journal Letters , revealed that Gaia23bra b, which orbits an orange dwarf star that’s about 80 percent of the Sun’s mass, is nearly 40,000 light-years away from Earth, far exceeding TESS’s usual search radius of about 150 light-years. Microlensing 101 Out of more than 6,000 known exoplanets (worlds outside our solar system), about three-fourths were discovered via the transit method, TESS’s typical planet-hunting technique. Astronomers monitor hordes of stars, watching for ones that periodically dim as orbiting planets cross in front of them — an event called a transit. This animation illustrates the concept of gravitational microlensing. When one star in the sky (shown in the center of the animation) appears to pass nearly in front of another (located in the dashed circle at the right) from our vantage point, the light rays of the background star become bent due to the warped space-time around the foreground star. This star acts like a virtual magnifying glass, amplifying the brightness of the background star and causing its position to appear to slightly shift. If the nearer star harbors a planetary system, then those planets can also act as lenses, each one producing a short deviation in the brightness of the source. When astronomers find planets this way, they can measure their mass and orbital distance from their host star. NASA’s Goddard Space Flight Center/CI Lab Microlensing has revealed less than 5% of known exoplanets. This light-bending phenomenon occurs when two stars align closely from our vantage point. Light from the more distant star curves as it travels through the warped space-time caused by the nearer star’s mass. If the alignment is especially close, the nearer star acts like a cosmic lens, focusing and magnifying light from the background star. Planets orbiting the foreground star may also modify the distant star’s light, acting as their own tiny lenses. Astronomers see the effect as a spike in the star’s brightness. The transit method is best at finding large planets orbiting very close to their host stars; large planets block the most starlight, while close-in planets are more likely to pass in front of the host star. These gargantuan, steamy worlds are fascinating to scientists, but astronomers want to find planets like those in our solar system, too. That’s microlensing’s specialty. With microlensing, we can find smaller planets with greater orbital distances, including worlds in the habitable zone of their star and even farther away. Mallory harris Ph.D. candidate at the University of New Mexico Microlensing isn’t well suited to finding huge, close-in planets because their gravitational signals would jus