Double comet… oh, my god, double comet, all the way across the sky!
If you’re ready to have your mind blown contemplating the vastness of the universe, mark your calendar for October 20 and the few nights following.
One comet would be cool enough to see, but in the second half of this month, it could be possible to see two of them.
Comets Swan and Lemmon will be visible at roughly the same time, and people are already getting excited for potentially glimpsing them both in the same night.
Just to spoil us a bit more, it will also happen at the same time as the Orionids meteor shower, which is when debris from Halley’s Comet causes a shower of shooting stars.
What are these double comets?
C/2025 A6 (Lemmon) was discovered in January, using a telescope from Mount Lemmon in Arizona. At that point, it seemed faint, and didn’t cause too much excitement.
But when it reappeared back from behind the Sun, it had become significantly brighter, and astronomers now think it might be clear with binoculars, or even the naked eye.
Meanwhile, C/2025 R2 (SWAN) was found by an amateur Ukrainian astronomer using solar data from the Solar Wind Anisotropies (SWAN) instrument.
Both have already been seen with a green tail using telescopes, but they are due to become so bright it could be possible to see them just by looking up.
When is the best time to see comets Lemon and SWAN?
According to StarWalk, the best time to observe Comet Lemmon is from October 12 (today!) until November 2.
The stargazing website predicted it could be the ‘best comet of 2025’.
It will be near Earth, and will reach its peak brightness around October 31 oe November 1, so a nice Halloween treat.
Meanwhile, Swan will reach peak visibility on October 20, which perfectly coincides with October’s new moon when skies are darkest.
Are they really comets or are they alien spacecraft?
Not normally something we ask about comets, but a similar question has been in the headlines lately, after a Harvard astrophysicist posited that Comet 31 Atlas could be on a mission to scope out Earth.
Dr Avi Loeb did stress that he didn’t necessarily believe this, but thought it was worth asking the question, given that comet originated from outside our solar system, and is only the third object we have ever identified as doing so.
Regarding the two comets visible later this month, most people accept that Lemmon is, in fact, a comet.
But some do think that Swan might also be an alien spacecraft, speculating it could be off to battle Comet 31 Atlas behind the Sun where we can’t see it.
Unfortunately (or fortunately?) for the theory, Swan has already reached its closest point to the Sun (perihelion) while Atlas won’t apprach until the end of the month.
Also, the idea of Swan being a mystery UFO is even less likely than Atlas, beause why the latter does actually come from outer space, with a theoretical chance it was sent by an advanced civilisation, Swan comes from the distant edges of our own solar system, the Oort Cloud.
How to see comets Swan and Lemmon?
Watch out for Swan low above the southwestern horizon as night falls on October 20, and look northwest to potentially see Lemmon at the same time.
Try to find somewhere with little light pollution, and clear skies.
Even then, there’s no guarantee they will brighten enough to be visible with the naked eye, but it won’t be a wasted night even if you just spot the Orionids.
With the right weather conditions, this would be the best night to try, but you might also get lucky during the nights immediately following,
What if I don’t see them this month?
Well, it’s probably not worth waiting around for the next time.
After it moves away from view, Lemmon won’t be seen again unless humans somehow work out how to download our conciousness into the cloud, because it won’t be back for over a millennium.
It was last seen about 1,350 years ago, around the time King Wulfhere died of illness and his brother Æthelred became the next King of Mercia.
There’s even less point waiting on Swan.
After it starts to head back towards the outer reaches of the solar system on November 3, it won’t be back again for more than 20,000 years.
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