What Are Trans-Neptunian Objects? Scientists Spot Unusually Close Binary TNOs

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  • A team of researchers spotted a close pair of trans-Neptunian objects
  • The unusually close pair was also occulting a binary star system
  • The discovery was made with the help of a citizen science project

With the help of a citizen science research network, a team of researchers has discovered an unusual pair of trans-Neptunian objects (TNO).

Any object in our solar system that has an orbit beyond Neptune is considered a TNO. According to NASA’s Jet Propulsion Laboratory (JPL), there are about 70,000 known TNOs, including Pluto, each measuring at least 100 kilometers (62.137 miles​) across.

In a new study, published in The Planetary Science Journal, a team of researchers discovered a TNO pair orbiting each other. The researchers discovered them using a stellar occultation, which occurs when the light of a star is blocked by an object from reaching the observer, a news release from the Southwest Research Institute (SwRI) said.

It is somewhat like a transit, which NASA’s TESS uses to search for exoplanets. NASA explains that the difference between the two is that in occultations, the object completely blocks the one behind it whereas, in transits, the object in front only blocks very little of the star behind.

In this case, the data showed that the binary TNO was actually occulting a binary star.

“Binary stars are not unusual and binary objects are not unusual,” study co-author Marc Buie of SwRI said in the news release. “But it is unusual that we had a binary TNO occulting a binary star.”

Trans-Neptunian Object Pictured: This image is an artist’s impression of the trans-Neptunian object that two Southwest Research Institute scientists recently discovered is a binary object. Photo: Southwest Research Institute

The first author of the study, Rodrigo Leiva, also of SwRI, says the two TNOs are