SOHO discovers a five-thousandth near-solar comet

The Solar and Heliospheric Observatory (SOHO) marked a round figure. It managed to find a five-thousandth near-solar comet. 

A 30-year mission

SOHO is a joint project of NASA and ESA. It was launched in 1995 and placed in a halo orbit around the L₁ point of the Earth-Sun system. SOHO collects information about the activity of the Sun, the state of its atmosphere and measures the characteristics of the solar wind.

SOHO in the artist’s impression. Source: ESA/ATG medialab; Sun: SOHO (ESA & NASA)

With a nominal service life of two years, SOHO is still in service and will celebrate its 30th anniversary next year. In addition to studying the Sun, the spacecraft unexpectedly turned out to be an extremely effective instrument for solving another task — the search for near-solar comets. 

This is the name of comets that come extremely close to our sun at perihelion, sometimes flying at a distance of only a few thousand kilometers from its surface. As a rule, they are small in size (most often from 10 to 50 m) and completely evaporate during their approach to the Sun. Because of this, they are extremely difficult to detect through ground-based observations. At the time of SOHO’s launch, the number of known near-solar comets was small and did not exceed several dozen.

SOHO Anniversary Comet

Soon after SOHO started working, the staff of the support group was surprised to find that its images often showed near-solar comets. Sometimes during the week, the spacecraft takes pictures of up to a dozen such objects. As a result, in order to systematize the search for comets, NASA launched the Sungrazer project. Within its framework, a group of amateur astronomers daily scans new SOHO images in search of still unidentified “tailed stars”.

This approach has proved to be very productive. In 2010, SOHO discovered its two thousandth comet, in 2015 — three thousandth, in 2020 — four thousandth. Now this list has reached the five thousand mark. 

The image on which the five thousandth comet of the SOHO mission was identified. Source: ESA/NASA/SOHO

The anniversary comet was found by Hanjie Tan, a graduate student from Prague. He has been involved in the Sungrazer project since 2009 and has discovered over 200 near-solar comets during this time.

The five thousandth comet SOHO belongs to the so-called Marsden group. It is believed that it is debris ejected by the much larger comet 96P/Mcholtz, which approaches the Sun every 5.3 years. This is a relatively small family, accounting for only 1.5% of all tailed guests found by SOHO. Like the vast majority of other near-solar comets, the anniversary comet did not survive the encounter with the Sun and was destroyed by its radiation.

According to

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