Astronomers see a “near the Sun” comet disintegrate as it flew too close to the Sun

Astronomers see a "near the Sun" comet disintegrate as it flew too close to the Sun

Comets coming close to the Sun can turn into something beautiful, but sometimes they are consumed when they get too close. Of the different types of comets orbiting close to the Sun, astronomers had never seen annihilation of the type classified as “near the Sun” comets. But thanks to a variety of telescopes on the summit of Mauna Kea in Hawaii? They say that the disintegration of this comet may help explain the lack of such periodic near-Sun comets.

Astronomers have certainly seen other types of comets disintegrating in the solar corona. For example, earlier this year — after making a spectacular appearance — Comet Leonard broke apart just after perihelion (closest point to the Sun) in January, 2022. Comet Leonard was thought to be a Sun-grazing comet, making up most of the known comets. Closest path to the Sun. The Solar and Heliospheric Observatory (SOHO) spacecraft has detected nearly 4,000 Sun-shepherds since their launch in 1995.

But there are also near-suns, sun-skirts and sun-divers. However, the nomenclature and distinction between them all are not clearly defined, says Carl Battams of the US Naval Research Laboratory in Washington DC. Batums tracks Sun-grazing comets with data from SOHO, particularly those belonging to the ‘Kreutz’ family of comets, named after the nineteenth-century astronomer Heinrich Kreutz, who discovered several of their orbits. was calculated.

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Astronomers see a "near the Sun" comet disintegrate as it flew too close to the Sun
It’s hard to detect, but the dot in the cross-hair is a comet facing the Sun. This image is from 2015, and is the 3,000th comet discovered by Comet SOHO since its launch. Image: SOHO/ESA/NASA

“There is no clearly defined separation between what we classify as a near-Sun versus a Sun-grazing comet,” Batms said via email. But he was part of a group of astronomers that drafted some of the guidelines in a 2018 survey paper.

He proposed clear definitions for comets, based on how close they come to the Sun: Near-Sun comets should include all objects orbiting Mercury, about .3 AU. Sunscatters are defined as objects that pass within 33 solar radii of the Sun’s center, equal to half the perihelion distance of Mercury, and the commonly used phrase sun-grazers are such objects. which reach perihelion within 3.45 solar radii. Finally, comets with orbits that intersect the solar photosphere are called sun-divers.

But, Batums says, definitions can still be confusing because all Sun-grazing comets are near-Sun comets, but not all near-Sun comets are Sun-grazing comets.

The near-Sun comet that was recently seen collapsing, named 323P/SOHO, is a short-period ‘near the Sun’ (but not Sun-grazing) comet that exhibited a distinct atmosphere to the Kreutz sun-grazers. felt.

Astronomers see a "near the Sun" comet disintegrate as it flew too close to the Sun
Near-sun object 323P/SOHO observed by the Subaru Telescope on December 21, 2020 (left) and by CFHT on February 11, 2021 (right). 323P/SOHO on its way to perihelion is seen as a point source in the center of the left image; After perihelion, the comet has developed a long narrow tail as seen in the right image. (credit: Subaru Telescope/CFHT/Man-To Hui/David Tholen)

“Instead of sinking deeper into the corona and erupting or vaporizing,” Battams said, “it’s slowly baking with repeated passes in a toasty atmosphere, causing a slow-but-steady death.” There are probably many non-Kreutz watching SOHO going through this process, but this is the first time we’ve been able to say with certainty that this is happening.”

Batms, who was not involved in the ground-based study of this comet, said this first-of-its-kind observation for this class of comet is an important result for telling us about the evolution and final stages of comets. -Sun” region. An excellent question is that objects closer to the Sun should be seen much less often than the model shows.

Comet 323P/SOHO was discovered along with SOHO in 1999, and is a relatively small comet, measuring only 172 meters (560 ft) in diameter. It spins rapidly at 0.522 pm, the fastest rotation of every known comet in the Solar System. Its orbital period is just over four years, so it has come close to the Sun several times. Furthermore, on its final pass, it came dangerously close to the Sun, with a perihelion of only 0.04 astronomical units. While a larger comet might have survived such a close approach, smaller comets that come closer are skirted with eventual annihilation.

Because comets like 323P pass so close to the Sun, they are difficult to detect and observe. To study this object, an international group of astronomers from Macau, the US, Germany, Taiwan and Canada used several telescopes, including the Subaru Telescope, the Canada France Hawaii Telescope (CFHT), the Gemini North Telescope, the Lovells Discovery Telescope, and the Subaru Telescope. As the Hubble Space Telescope.

Astronomers see a "near the Sun" comet disintegrate as it flew too close to the Sun
Convex shape model of the nucleus of 323P/SOHO in three orthogonal views. The left and middle panels show side-by-side views of the nucleus which are 90° apart from each other, its spin axis ( jade-axis) pointing upward, while the nucleus is viewed in a pole-on configuration (line of sight with negative jade direction) in the right panel. Credit: Man-to-Hui/David Tholen)

Observations with the Surbaru telescope, which has a wide field of view, were the first time 323P/SOHO was captured by a ground-based telescope. With this data, the researchers were able to better constrain the orbit, and they knew where to point the other telescopes when 323P/SOHO began to move away from the Sun again.

To their surprise the researchers found that 323P/SOHO had changed significantly during perihelion. In the Subaru Telescope data, 323P/SOHO was just a point.

“However, in our post-perihelion observations, it developed a long, narrow tail mimicking a disintegrating comet debris cloud,” the authors write in their paper.

They also found that 323P/SOHO has a different color than anything else in the Solar System. They say that observations of other near-Sun comets are needed to see if they also share these traits.

The researchers said they believe the intense radiation from the Sun caused parts of the comet to break apart due to thermal fracturing, much like ice cubes bursting when you pour a hot drink on them. This mass loss mechanism may help explain what happens to near-Sun comets and why there are so few of them.

The researchers hope to learn more about whatever remains of the comet at its next perihelion. But it will sink into the Sun at one of the next close passes.

Paper: The Sluggish Death of Periodic Near-Sun Comet 323P/SOHO.
NAOJ Press Release
Email Exchange with Karl Buttams