Comet and Asteroids

[Gaby]

The full video of comet PANSTARRS from the LASCO telescope is available here. Pretty!

Comet C/2025 R3 has passed by the Sun and will be ejected from the solar system

An exceptionally beautiful sight has been visible over the past three days in images from the LASCO telescope—between Earth and the Sun, almost exactly between them, at a distance of 75 million km from Earth, Comet C/2025 R3 (PanSTARRS) passed by slowly. The celestial body was discovered last September (prior to that, this comet was unknown) and, by all accounts, arrived at Earth from the so-called Oort Cloud—a vast cluster of comets, asteroids (and possibly minor planets), located about one light-year from Earth but nonetheless part of the Solar System.

The comet tops the brightness rankings among the approximately 100 cometary bodies currently visible in the sky (most of these bodies are visible only through very large telescopes operating at the limits of their sensitivity). The object will remain at the top of the list for at least another month, moving further away from Earth all the while. The comet’s future fate is both sad and inspiring. Calculations show that the Sun is ejecting the comet from the Solar System—its trajectory has diverged as it passes by, and the object is passing Earth and the Sun for the last time. Ahead lie tens of millions of years of emptiness, but somewhere on the horizon, an encounter with other suns and other star systems is possible—and almost certain to happen.

On Earth, however, the comet season is coming to an end. Two bright bodies with opposite fates—Comet C/2026 A1, which perished in the Sun, and, conversely, Comet C/2025 R3, which has permanently escaped its embrace—gave us a brilliant start to the year, which is now giving way to months of emptiness. None of the comets already visible in the sky are capable of reaching a luminosity comparable to that of these bodies. We can only wait for new visitors.

Solar Astronomy Laboratory (xras.ru)

 

[Gaby]

At the end of the video quoted above, you can see that the comet develops two tails. Xras.ru zooms in on this and draws a nice attempt to explain it. In short, plasma discharge comet theory.

A second tail forming on the comet was captured from space

The LASCO telescope, which had Comet C/2025 R3 in its field of view, managed to observe the formation of a second tail around the comet’s nucleus in the final hours before the comet disappeared from view. The attached video begins on April 25 at 9:18 p.m. Moscow time and ends today, April 27, at 2:18 a.m. (total duration: 29 hours). The video in its original quality (2.5 MB) is available via the link.

The nature of the structure as a whole is not obvious. Comets’ second tails, known as ion tails, usually form under the influence of the solar wind; however, since comets are constantly immersed in the solar wind, the tails associated with it are typically stationary, long-lasting structures. In this case, it is difficult to explain the sudden formation of the tail and its very rapid dynamics: over the course of a day of observation, the structure rotated around the comet’s nucleus by an angle of about 90°.

One possible explanation is that the comet was struck by one of the two plasma clouds ejected by the Sun on April 23–24, between which Earth had so narrowly passed the day before. The start of the formation of the second tail of C/2025 R3 (midday on April 25) roughly coincides with the calculated time when the comet could have been hit by the solar wind. A sharp increase in the density and temperature of the surrounding gas could have triggered the formation of an ion tail, for which the density of the normal solar wind was insufficient to sustain it. There are, however, other explanations: ranging from the mundane—simply a coincidence—to the quite romantic, such as the awakening of a geyser on the comet’s nucleus (this does indeed happen).

The comet should become visible from Earth again within a few days (the Sun is currently blocking the view). We’ll see if the celestial body still has a second tail by then. If not, the hypothesis that the tail was temporarily formed by a solar plasma impact will become very likely.

 

[SasaM]

The full video of comet PANSTARRS from the LASCO telescope is available here. Pretty!

In that video, there were also two notable solar 'burps' or energy/mass ejections from the Sun in general direction of the comet's trajectory as it was passing by, that seem to correspond to those two X class solar flares that happened few days ago.
It surely gave the impression that the comet's passage might have triggered them.