Mysterious Asteroid 3200 Phaethon Confuses Astronomers as It Acts Like a Comet [Study]

A comet-like asteroid leaves astronomers baffled. It's reportedly an asteroid but behaves like a comet.

Mysterious Asteroid 3200 Phaethon

NASA has been studying asteroid 3200 Phaethon for years. However, the more they look into it, the weirder it gets, CBS News reported.

NASA released a statement Tuesday giving an update about the asteroid with a comet-like tail. The fact that the asteroid 3200 Phaethon behaves like a comet has long been known, the American space agency noted. Although comets are often responsible for meteor showers, the yearly Geminid meteor shower is caused by one that brightens and creates a tail when it is close to the Sun.

Phaethon's comet-like behavior was initially attributed to dust escaping from the asteroid as it gets burnt by the Sun. However, a recent investigation employing two NASA solar observatories revealed that Phaethon's tail is formed of sodium gas and not at all dust.

Qicheng Zhang, a Ph.D. student at the California Institute of Technology and the paper's primary author, noted that their study demonstrates that dust cannot account for Phaethon's comet-like behavior.

Zhang searched for the tail again in 2022, during Phaethon's most recent perihelion, to learn what it comprises. He took advantage of the NASA and ESA-collaborated Solar and Heliospheric Observatory (SOHO) spacecraft, which contains color filters that can find sodium and dust. The tail was discovered by Zhang's team in 18 of Phaethon's close solar encounters between 1997 and 2022 by searching old Solar Terrestrial Relations Observatory (STEREO) and SOHO pictures.

The asteroid's tail was brightly visible in the sodium detection filter during SOHO observations but not in the dust detection filter. In addition, if Phaethon's tail were made of sodium, it would have the same shape and brightness as it passed the Sun, but not if it were made of dust.

This data suggests sodium, not dust, makes up Phaethon's tail.

According to team member Karl Battams of the Naval Research Laboratory, they performed this using data from two heliophysics spacecraft, SOHO and STEREO, which were not intended to study phenomena like this. As a result, we have an amazing conclusion that somewhat contradicts 14 years of thinking about a well-examined item.

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How Phaethon Supplies Material for Geminid Meteor Shower?

The asteroid Phaethon doesn't produce much dust, so how can it contribute to the Geminid meteor shower we observe every December?

Zhang's team hypothesizes that a disruptive event occurred a few thousand years ago that caused Phaethon to eject the billion tons of material that are believed to make up the Geminid debris stream. This disruptive event may have involved a section of the asteroid breaking apart under the pressure of Phaethon's spin. However, the nature of the incident is still unknown.

Zhang and his colleagues are unsure whether some comets discovered by SOHO and citizen scientists participating in the Sungrazer Project who studied SOHO photos are comets.

According to Zhang, many of the other "comets" that are skirting the Sun may not be comets in the traditional sense of an icy body but rather are rocky asteroids like Phaethon that have been burned by the Sun.

The study was published in the Planetary Science Journal, reporting the results.