The TESS exoplanet telescope has revealed a distant world using a completely different detection method than the one it was built around
By Sam Macdonald edited by Sarah Lewin Frasier
Artist’s concept visualizing Gaia23bra b, the first microlensed planet orbiting a distant star discovered by NASA’s Transiting Exoplanet Survey Satellite (TESS).
NASA Goddard Space Flight Center
It seems that NASA Satellite for studying transiting exoplanets (TESS) is an outperformer.
When NASA launched TESS in 2018, the satellite had just one job: monitor nearby stars for tiny dips in brightness caused by planets passing in front of them. That’s what he did spectacularly gooddiscovering hundreds of new worlds. Scientists now realized that TESS was also collecting evidence of something it never expected to find.
In a study published on July 1 in the Letters from astrophysical journalsthe researchers report that TESS captured the signal from Gaia23bra ba planet orbiting a star nearly 40,000 light years away, more than 250 times the distance to the nearby stars that TESS was designed to study.
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It’s a bit like pointing a backyard bird camera at your feeder and later realizing you’ve also captured wildlife on another continent.
Even more surprising, TESS discovered the planet using a technique for which it was not designed.
The discovery began in April 2023, when the European Space Agency’s Gaia space probe spotted a brief brightening of a distant star. This flash was caused by gravitation microlensesa phenomenon predicted by Albert Einstein.
When two stars align almost perfectly from Earth’s perspective, the gravity of the closer one bends and amplifies the light of the more distant star, acting like a cosmic star. magnifying glass. If this foreground star hosts a planet, it leaves ripples in the magnified light.
Gaia recorded the stellar brightening, but did not collect enough observations to reveal the planet itself. Fortunately, less than a month later, TESS was looking at the same part of the sky.
“Observations of Gaia were too rare to be captured on the planet,” said Mallory Harris, a Ph.D. candidate at the University of New Mexico and lead author of the study, said in a statement. “The TESS spacecraft was monitoring the same area of the sky during the microlensing event, and its denser temporal coverage showed additional features in the light curve caused by a planet.”
But no one noticed it.
Why would they?
“When TESS was launched, no one expected that it would be able to find this type of planet,” Diana Dragomir, study co-author and assistant professor at the University of New Mexico, said in the same release.
The microlensing array between the two stars came and went in 2023, and the telltale planetary signal went unnoticed in the TESS archives for nearly three years before researchers connected the dots.
“This discovery implies that there are likely other so-called microlensing planets hidden in the TESS data that we hadn’t thought to look for before,” Dragomir said.
The discovery suggests that one of NASA’s most successful planet hunters may still be hiding plenty of surprises in its archives.
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