Yikes.

And it’s clear! (At least in Oxford)

Americans and others who do not know: tonight is the night for #duvetknowitschristmas. Enjoy.

Parents & anyone else up early on Christmas morning: there’s a bright pass of the International Space Station over the UK, just after 6.15. Well, I say it’s the ISS. Could be Santa heading home… Exact timings for where you are at www.heavens-above.com/PassSummary....

A little 3I/ATLAS update building on @marshall-eubanks.bsky.social's nice RNAAS from last week. Given its non-grav acceleration and the rate at which it's losing mass, you can work out its size. The answer: a diameter around 1 km, very typical for comets. arxiv.org/abs/2512.18341 🔭 🧪

Heading into what's already looking like a, let's say, challenging 2026, this lovely little piece stands for science too. Do the work. It'll help.

Great research opportunity at a world leading institute 🔭

The days will start getting longer… …wait for it… …now! Winter solstice 2025, December 21st, 15:03 UTC

Anyone tuning in to see me talking about 3I/ATLAS on Sky News should know I’ve just managed to put my right foot into a bowl of mulligatawny soup while setting up.

Always nice to hear from fans.

Europa Clipper has imaged interstellar comet 3I/Atlas with its ultraviolet spectrometer! This is only the 3rd interstellar object discovered so far: an icy wanderer from a distant planetary system, and now we’ll learn more about what it’s made of!! 🔭 www.swri.org/newsroom/pre...

Accepted papers thus far - several more still in peer review, or underway

Just because you keep saying the same things doesn’t make you any more right. #NoNotHimTheOtherOne #WhatDoWeCallASubtweetOnBluesky

@chrislintott.bsky.social and I were talking about making cute cartoon versions of past spacecraft, and he mentioned encounters with the Great Galactic Ghoul, so here's what really happened to Mars Polar Lander, rest its motherboard. #space #Mars

Today would be a great day to sign up to become a Cosmic Shambles Patreon. No reason… patreon.com/cosmicshambles @robinince.bsky.social

All missions should have cartoon versions of their spacecraft, and these cartoons should be on all slides. These are the rules, as shown here by JAXA’s Go Murakami talking about BepiColombo.

Louise Devoy presenting the tool every astronomer needs: a spider fork.

Wait, seismologists have a unit of slowness‽? s/km, apparently...

Helen Grant (Kent) is now talking at @royalastrosoc.bsky.social on sample return from flying through the watery plumes of Enceladus and the volcanic plumes of Io. What missions those would be!

This thing will find us some interstellar objects, too!

At the @royalastrosoc.bsky.social getting very excited about future sample return missions, including JAXA's MMX - launch next year, bringing back bits of Mars' moon Phobos. The hope is we'll get Martian samples sitting on the surface of the moon too. www.mmx.jaxa.jp/en/

Cycled past my favourite blue plaque in London this morning: Thomas Young MAN OF SCIENCE. www.english-heritage.org.uk/visit/blue-p...

@spoonsontrays.bsky.social #museumofshadows from the National Gallery’s Joseph Wright exhibition

How have I not noticed the National Gallery mosaics before? Science! Rutherford! Sea monsters! Amazing stuff

Really interesting analysis here on how claims get amplified by our current media environment (and a rebuttal of sorts to those who argue that Avi Loeb's alien spacecraft hype is good because any science engagement is good engagement): www.cip.uw.edu/2025/12/03/3...

The XRISM satellite has detected the x-ray glow of Comet 3I/ATLAS. This is the first time anyone has managed to obseve x-ray emission from an interstellar comet! (FYI: X-rays result from the comet interacting with the solar wind. No spaceships required.) 🔭🧪 www.xrism.jaxa.jp/en/topics/ne...

So, let us make, And set the weather fair. (MacNiece, Fanfare for the Makers)

Just finished ‘The Martians’ by David Baron, a pacy story of the Martian canal craze and Percival Lowell, the man who believed more than anyone else that life had been discovered. It’s great - detailed yet written with a lovely light touch. blackwells.co.uk/bookshop/pro...

The first image of #3IAtlas from ESA's JUICE mission is in! I reprocessed the image to remove hot pixels (left) and the stars (right) to make the tail easier to see. Credit: ESA/Juice/NavCam Processing: Simeon Schmauß

NEW: Researchers have found a ‘razor-thin’ string of galaxies rotating together inside a giant cosmic filament 140 million light-years away – one of the largest spinning structures ever seen. The findings could offer valuable new insights into how galaxies formed in the early Universe. More info ⬇️

Back to bed. #thecricket

It’s Mars tonight @greshamcollege.bsky.social - live online from 7pm GMT www.youtube.com/live/fC0zdsG...

Interested in finding transiting planets at long periods, e.g. with the @platomissioncon.bsky.social? We just published a Research Note led by Geert Jan Talens, showing that such transits can be much longer or shorter than usually assumed iopscience.iop.org/article/10.3...

Tryptophan? In Bennu? Happy Thanksgiving! www.pnas.org/doi/10.1073/...

#Humblebrag. Today is my 45th birthday. This is a completely arbitrary number. However, as it turns out it is also the day I got my #realtennis singles handicap under 30 (to 29.9), also an arbitrary number. But one I’m very pleased about; the result of a lot of sweat, some tears, & a little blood.

Tag yourself. I’m roundish beaky guy, second down on the right.

For more than a decade now the government’s answer to how to fund universities has been to make money from overseas students. The last lot then tried to discourage students from coming here. This lot just want the money back. But then how do we fund ourselves? Crazy.

The cricket score.

Cambridge! We’re bringing a Universe of Music to you next Thursday. This show features shells, black holes, music, planets and more - do come if you can! www.junction.co.uk/events/linto...

Dressing room debris after my Universe of Music Show with Steve Pretty in Cambridge last night. The suspicious white powder is from conch sawing. Honest.

This is a real image of a real thing that exists in the universe! And because a bunch of humans decided to get together and build a space telescope, we get to see it! 🤯

@lsstuk.bsky.social and @vrubinobs.bsky.social need your help to train our computing systems to sort through the tens of millions of alerts we will detect every night during the Vera C. Rubin Observatory #LSST survey. www.zooniverse.org/projects/ebe... #capturethecosmos

I know it’s hard. But you can’t possibly go to an academic conference that imposes restrictions on freedom of speech like this.

@oldenoughtosay.com Heard a new Oxford building story today. Allegedly Magdalen Tower was almost entirely replaced, stone by stone, in the eighties. Any truth to it?

Astronomers: I'm having trouble installing the SPARCL-client. Is this a known problem?

New paper's out! First result from excellent DPhil student Brian Rogers - machine learning for scientific discovery. (I'll post a thread explaining in a bit). arxiv.org/abs/2511.09433

Opening of Star Trek Voyager's 'Death Wish': CHAKOTAY: Its trajectory is erratic, & our sensors aren't detecting any stellar or planetary gravitational fields that could account for its motion JANEWAY: Then you're saying it isn't a comet CHAKOTAY: And yet it looks, feels, & tastes just like a comet

Get outside into a dark place if you can tonight - no guarantees, but a possible brilliant display of the northern lights.

Sky at Night always used to have an early repeat - and we're back, with our collaboration with the Curious Cases team on at 7pm tomorrow on BBC4. Please watch if you possibly can - support your local science program! www.bbc.co.uk/programmes/m...

Londoners! Drink excellent wine and chat with me about space, next week: www.eventbrite.co.uk/e/cosmology-...