Among the near-solar comets lurking "outsiders"

Among the near-solar comets lurking

Come comets love to play "weakly" with the sun. But some of them may not be comets at all.

Recently, we have been spoiled by comet news. The Rosetta spacecraft circled Comet 67P Churyumov-Gerasimenko for 18 months and sent back daily information about what changes are taking place in it.

Now this mission is over, but, fortunately, there is another protracted mission that monitors circumsolar comets (objects that come very close to the star). The spacecraft of the Solar and Heliospheric Observatory (SOHO) is designed to observe our nearest star and its fine atmosphere. Fortunately, he also manages to monitor cometary oscillations. Over the past 20 years, he managed to find more than 3,000 such objects.

And the interesting news is that a minority of these near-solar comets may not be comets at all. The object 322P / SOHO 1 seems to have some properties of asteroids or cosmic stones, but does not consist of a free mixture of dust and ice, which comets can recognize. These and other properties of the near-solar objects are discussed in a new document under the leadership of Karl Battams, an astrophysicist from the US Naval Research Laboratory in Washington, DC. “We found that this species looks like an asteroid and a comet,” said Battams. “This is a strange hybrid. The results seemed uncertain, so we are not sure if this object was once a comet ... or maybe it was a stuck asteroid. There is no final conclusion yet. ”

Among the near-solar comets lurking

Comet ISON is one of the most well-known observations of SOHO, taken in an interval survey in 2013 (ESA / NASA / SOHO).

Approximately 86% of the observed SOHO comets are definitely comets. They belong to a certain family - the Kreutz comet, and include the infamous comet ISON that crashed into the Sun three years ago for Thanksgiving. The comet fell apart, and then flashed for the last time, before disappearing forever. This shows how difficult it is to predict the behavior of a comet. Battams considers that day a real madness.

The remaining 14% of the near-solar objects are more difficult to determine. They represent four different groups - Meyer, Marsden, Kracht and Kracht II. There is also a fifth “non-group” of objects that, by their properties, do not fit anywhere. Battams suggests that most of these other near-solar objects may be cometary nuclei, or perhaps asteroids, which somehow came close to the Sun.

But further observations are needed. It is difficult to predict their orbits, because when they pass the Sun, the star’s gravity changes their path. However, after several passes of short-term comets, scientists can make more accurate predictions about where the object is going. In this way, a group led by Matthew Knight of the University of Maryland watched 322P / SOHO 1 distant from the Sun. This was the first such observation.

Among the near-solar comets lurking

Artistic interpretation of the SOHO spacecraft against the background of the Sun.

Battams recalls the importance of researching near-solar objects, which are often invisible when solar energy is not close. He recalled that around 2008, the Marsden group was extremely close to lunar orbit. In astronomical terms, this was a situation “almost inevitable death”. This suggests the need to better track these objects, because some of them may pose a threat to the Earth.

“SOHO fulfills this mission, but its magnitude is limited,” said Battams, hinting at the visible brightness. SOHO can see objects up to magnitude 9. And this is not so far from the possibility of observations with the naked eye (approximately 6). He said that a typical asteroid survey could go down to a magnitude of 22.

SOHO continues to do its job well and can even participate in the discovery of comets.

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