Hidden giant exoplanet citizen scientist found

Astronomers have discovered thousands of exoplanets so far, but in fact these are only a fraction of the planets in the galaxy. Moreover, due to the limitations of observation technology, exoplanets that are relatively close can be discovered only when various conditions are met. An elusive exoplanet is a planet with a large mass and very close to the star that periodically obscures or subtly shakes the star. Therefore, planets that have a long orbital period like Jupiter and are far from stars are difficult to detect.

Astronomers at the University of California, Riverside (UCR) and citizen scientists who volunteered for astronomical research overcame these difficulties and succeeded in finding a hidden giant exoplanet. Astronomers are getting help from citizens to manually classify and verify vast amounts of astronomical data. For example, a subtle change in brightness, a sign that a planet is hiding. Although the role of artificial intelligence has been increasing recently, astronomers are being helped by citizen scientists because there are still areas that are not easily noticed by non-humans.

Former naval officer Tom Jacobs, one of these citizen scientists, was examining data from NASA’s planet hunter TESS, when he noticed a subtle change in brightness in the star TOI-2180. This could be evidence of exoplanets, so Jacobs immediately provided the information to astronomer Paul Dalba at the University of California. However, the team could only confirm the change in brightness once, so they could not be sure that this was a signal from an exoplanet. This is because the brightness of a star can change for a number of reasons, and sometimes there are errors in the device.

Still, the research team believed that this signal could be a signal from an exoplanet with a relatively long orbital period, and in mid-2020, 14 telescopes spanning three continents were used to observe TOI-2180. The research team obtained as many as 20,000 images, but unfortunately did not find any evidence of exoplanets. Usually, this is enough to give up, but the research team did not abandon the possibility that an exoplanet with a longer orbital period than expected might be hiding.

In the end, after obsessive observation, the research team confirmed the second brightness change in the TESS data in February 2021. It was not a signal anomaly or a coincidence, but an exoplanet with a long orbital period actually existed. The orbital period of this exoplanet is 261 days, which is shorter than that of Earth, but it is quite long among exoplanets reported so far. This means that an exoplanet with an orbital period that is difficult to detect with current observational techniques has been discovered.

Interestingly, however, is not just the orbital period. According to the research team’s analysis, the planet’s diameter is similar to that of Jupiter, but the mass is three times that of Jupiter. Therefore, it can be presumed to be a planet with a very large central rock and metal nucleus. The team estimated that the mass of the heavy element would be 105 times the mass of Earth. In addition to the orbit, it is a planet with different characteristics from exoplanets so far.

TOI-2180b is 379 light-years away from Earth and is close to the center of exoplanets, so scientists expect subsequent observations to reveal several facts.

Gordon Jung Columnist jjy0501@naver.com