This two-hour sequence of images from the Solar and Heliospheric Observatory (SOHO) shows Phaethon (circled around) moving relative to background stars. While SOHO regularly observes the Sun, it also observes numerous objects that pass near the Sun, including asteroids and comets.
In 2009, NASAs Solar Terrestrial Relations Observatory (STEREO) spotted a short tail extending from Phaethon as the asteroid reached its closest point to the Sun (or “perihelion”) along its 524-day orbit. Regular telescopes had not seen the tail previously because it just forms when Phaethon is too close to the Sun to observe, except with solar observatories.
In 2018, another solar mission imaged part of the Geminid particles path and found a surprise. Observations from NASAs Parker Solar Probe showed that the trail consisted of much more material than Phaethon could perhaps shed throughout its close methods to the Sun.
Zhangs group wondered whether something else, besides dust, lagged Phaethons comet-like habits. “Comets frequently glow remarkably by sodium emission when really near the Sun, so we suspected salt could similarly serve an essential function in Phaethons brightening,” Zhang stated.
An earlier research study, based on models and lab tests, recommended that the Suns extreme heat throughout Phaethons close solar techniques could undoubtedly vaporize sodium within the asteroid and drive comet-like activity.
The Large Angle and Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) imaged asteroid Phaethon through different filters as the asteroid passed near the Sun in May 2022. On the left, the sodium-sensitive orange filter shows the asteroid with a surrounding cloud and little tail, suggesting that sodium atoms from the asteroids surface area are glowing in reaction to sunshine. On the right, the dust-sensitive blue filter shows no indication of Phaethon, showing that the asteroid is not producing any noticeable dust. Credit: ESA/NASA/Qicheng Zhang
Intending to learn what the tail is actually made from, Zhang searched for it once again during Phaethons newest perihelion in 2022. He utilized the Solar and Heliospheric Observatory (SOHO) spacecraft– a joint objective in between NASA and the European Space Agency (ESA)– which has color filters that can detect salt and dust. Zhangs group also browsed archival images from STEREO and SOHO, discovering the tail throughout 18 of Phaethons close solar approaches in between 1997 and 2022.
In SOHOs observations, the asteroids tail appeared bright in the filter that finds sodium, however it did not appear in the filter that finds dust. In addition, the shape of the method and the tail it brightened as Phaethon passed the Sun matched precisely what researchers would anticipate if it were made from salt, but not if it were made from dust.
This evidence indicates that Phaethons tail is made of sodium, not dust.
” Not just do we have a truly cool result that sort of upends 14 years of considering a well-scrutinized things,” stated staff member Karl Battams of the Naval Research Laboratory, “however we likewise did this utilizing data from two heliophysics spacecraft– SOHO and STEREO– that were not at all meant to study phenomena like this.”
Zhang and his coworkers now question whether some comets found by SOHO– and by citizen scientists studying SOHO images as part of the Sungrazer Project– are not comets at all.
“A lot of those other sunskirting comets might likewise not be comets in the normal, icy body sense, but might instead be rocky asteroids like Phaethon warmed up by the Sun,” Zhang explained.
Still, one essential concern remains: If Phaethon does not shed much dust, how does the asteroid supply the material for the Geminid meteor shower we see each December?
Zhangs team suspects that some sort of disruptive event a couple of thousand years back– perhaps a piece of the asteroid disintegrating under the tensions of Phaethons rotation– caused Phaethon to eject the billion lots of material estimated to comprise the Geminid particles stream. But what that event was stays a mystery.
More answers may come from an approaching Japan Aerospace Exploration Agency (JAXA) mission called DESTINY+ (short for Demonstration and Experiment of Space Technology for Interplanetary voyage Phaethon fLyby and dUst Science). Later this years, the DESTINY+ spacecraft is expected to fly past Phaethon, imaging its rocky surface area and studying any dust that might exist around this enigmatic asteroid.
This illustration portrays asteroid Phaethon being heated by the Sun. The asteroids surface area gets so hot that salt inside Phaethons rock may vent and vaporize into area, causing it to lighten up like a comet and remove small pieces of rocky particles. Credit: NASA/JPL-Caltech/IPAC
Researchers discovered that asteroid Phaethon, the source of the Geminid meteor shower, has actually a tail made from sodium, not dust. This finding challenges 14 years of understanding about the object and raises questions about the nature of some comets. The origin of the Geminid meteor showers product stays a secret, with more responses anticipated from an approaching JAXA objective, DESTINY+.
Asteroids, which are primarily rocky, do not typically form tails when they approach the Sun. Comets, nevertheless, are a mix of ice and rock, and generally do form tails as the Sun vaporizes their ice, blasting material off their surface areas and leaving a path along their orbits. When Earth travels through a particles trail, those cometary bits burn up in our environment and produce a swarm of shooting stars– a meteor shower.
After astronomers discovered Phaethon in 1983, they recognized that the asteroids orbit matched that of the Geminid meteors. This indicated Phaethon as the source of the annual meteor shower, despite the fact that Phaethon was an asteroid and not a comet.
The asteroids surface gets so hot that salt inside Phaethons rock may vaporize and vent into space, triggering it to brighten like a comet and dislodge little pieces of rocky particles. Scientists discovered that asteroid Phaethon, the source of the Geminid meteor shower, has actually a tail made of sodium, not dust. In 2009, NASAs Solar Terrestrial Relations Observatory (STEREO) found a short tail extending from Phaethon as the asteroid reached its closest point to the Sun (or “perihelion”) along its 524-day orbit. The Large Angle and Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) imaged asteroid Phaethon through different filters as the asteroid passed near the Sun in May 2022. On the right, the dust-sensitive blue filter reveals no sign of Phaethon, suggesting that the asteroid is not producing any detectable dust.