3
$\begingroup$

Some news channels published a video of an unusual phenomenon. The description says it's Comet Pons Brooks, but the comet looks completely different. There are other videos of this kind on YouTube, the phenomenon is not unique. What is this phenomenon? How is it explained? Screenshots:

enter image description here

enter image description here

Source: https://t.me/c/1333788481/1673

$\endgroup$
9

3 Answers 3

21
$\begingroup$

That is a re-entry of an artifical satellite, or rocket body. (As Darth Pseudonym mentions, its actually the upper stage from the Soyuz MS-25 launched two days earlier).

It's certainly not a comet. Comets don't move over a few seconds. They are in orbit around the sun and so they appear to move about as fast as the planets do, and usually more slowly than the moon. They are also usually faint. Pons Brooks, for example would be close to invisible in the light polluted sky of a city, even at its brightest (which isn't for 3 months). Whatever website said that this is a comet is pretty useless.

It looks rather similar to a natural meteor. But meteors, which come from deep space, are normally moving much faster, and so glow brighter, but also are destroyed more quickly. You don't normally see the break-up and several glowing chunks. Instead you just see a streak, or sometimes a streak and an explosion.

So this is a satellite or rocket re-entry. There are lots of other videos eg

$\endgroup$
1
9
$\begingroup$

Objects that shed a lot of bits like that and move relatively slowly are usually human-made space junk from low-earth orbit that has slowed down enough to reenter and burn up.

It's definitely not a comet; comets look like a narrow triangular blur or cloud, and move across the sky over the course of days or weeks, not seconds. The movement is usually only visible by comparing its position across many nights.

For example, this photo published on NASA's website: Comet NEOWISE

There's some possibility that this is a meteor, but as meteors are moving at solar-orbit speeds on a different orbit than Earth, they usually move much faster across the sky and rarely shatter into pieces like that -- a meteor that breaks up usually looks like a fireball rather than visibly separate pieces of material on parallel courses, as in the case of the Chelyabinsk meteor in 2013: The Chelyabinsk meteor

Given the speed and the visible breakup, a meteor is a possibility, but it's just much less likely than the reentry of a complex manmade object like a rocket stage or an old satellite.

But, since we know these images were taken in Khabarovsk, Russia on March 25th 2024, the object can be pretty solidly identified as the upper stage from the Soyuz MS-25 launch on the 23rd. It took a couple of days for the orbit to drop enough to hit thick atmosphere and burn up spectacularly.

$\endgroup$
3
  • $\begingroup$ I don't understand the argument that Khavarovsk implies it is a Russian rocket. A rocket part orbits the Earth many times in 2 days. There is no reason for it to reenter near the place it was launched. $\endgroup$
    – Florian F
    Commented Mar 29 at 10:13
  • $\begingroup$ We (national militaries, astronomers, etc) track pretty much all the rocket stages and satellites in orbit, so "something happened over Khabarovsk on this day and time" is a simple matter of checking whether any tracked objects were in that area and low enough to reenter, and there was one, which originated from the Soyuz launch. It's more or less coincidence that a Russian rocket part reentered over Russia (but not entirely; space programs generally plan where their debris is going to end up, if only to avoid dropping something on another country and causing an incident). $\endgroup$ Commented Mar 29 at 14:56
  • $\begingroup$ China is a notable exception, in that they have been strongly criticized lately for letting rocket stages just kinda come down wherever they happen to be with no apparent planning. That sort of thing tends to makes other countries annoyed. $\endgroup$ Commented Mar 29 at 15:01
6
$\begingroup$

As James K said, that's no comet. ;)

12P/Pons–Brooks is a relatively bright comet, but it's certainly not that bright.

On 2024-Mar-26, JPL updated the trajectory data for this comet, which has ID 90000223.

Its orbit has high inclination (74.19°), and it's approaching the ecliptic from the north. It reaches perihelion on 2024-Apr-21. Here's a Horizons plot showing its orbit (purple) and Earth's (blue), using a 5 day time step for 180 days either side of that date, from 2023-Oct-24 to 2024-Oct-18. Plot points are at 0:00 TT. Numeric labels are every 30 days. The orange dot is the Sun, the grey plane is the ecliptic, the dark vertical line is the J2000 equinox line (the +X axis of the ecliptic and equatorial coordinate systems).

Comet Pons-Brooks & Earth, 2024

It looks better in the interactive 3D view. There's some info about an earlier version of my plotting script here. This version also has a "rainbow" option, which gives dots equal hues at equal times.

It's also interesting to look at the geocentric trajectory of the comet. Just make Earth (ID 399) the Center, and make the Sun (ID 10) one of the Targets.


Here's a plot showing the comet's estimated total magnitude, once again using a 5 day time step. Plot points are at 0:00 UTC.

Comet magnitude

Here's a plot of the ecliptic latitude and longitude of the Sun and 12P/Pons–Brooks, using the same time step.

Ecliptic lat & lon, Sun & comet

This table shows the date corresponding to each numeric label.

Label Date
0 2024-Mar-01
1 2024-Mar-16
2 2024-Mar-31
3 2024-Apr-15
4 2024-Apr-30
5 2024-May-15
6 2024-May-30
7 2024-Jun-14

The magnitude plotting script can be found at the end of this answer. Note that for comets, the nuclear magnitude replaces the surface brightness. Please see the Horizons manual for details.

The latitude-longitude script is here. It's a minor update to the script in this answer.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .