Teaching the students which parts of spacetime can or cannot send out light rays that reach a uniformly accelerated observer. 🧪 ⚛️

Another interesting paper for mapping. ui.adsabs.harvard.edu/abs/2023A%26...

I took a course in astronomy in university but my degree is in mathematics and I learned most of what I know about astronomy from reading papers in arXiv and ADS. I think the main problem with my university courses was that the question "why is this important?" was usually left unanswered.

Just noticed that Messier 99 is a "Fiddler Crab" galaxy a bit like my model with two very different arms. Credit: ESO VLT.

I've been skeptical about using kinematic (gas velocity) distance estimates. However, recently I have been comparing them with masers. There are problems with the solar circle (gas that has the same distance to the galactic centre as the Sun), However, otherwise the correspondence is not bad.

The programme of EAS 2026 is now available! 🔭 #galactic This year, @emily.space, Josefa Großschedl, and I are chairing a special session! We are co-organising it with notably @mac0598.bsky.social on the topic of young stars, clusters & association in the Milky Way! #EAS2026Lausanne

All stars move relative to us, and while relatively slow, their positions do detectably change over decades. I wrote a #Python program to calculate a star's location in the sky at a given epoch (time). Gonna need it for updating @celestiaproject.bsky.social. #CelestiaProject #astronomy #star

My wife loves #chocolates and #boardgames so for Valentine's Day I got her a box of Belgian pralines and we played a round of Star Realms. Blowing up each other's galactic bases may not have *quite* fit the theme of the day but was fun. I squeeked to victory with 11 authority points remaining.

Just came across a very interesting paper. ui.adsabs.harvard.edu/abs/2017ApJ....

Normally my maps of the Milky Way focus on specific objects (star clusters, HII regions), or density distributions (dust, hot stars). I sometimes extrapolate beyond these to larger OB associations or star formation regions (eg. Ori OB1) but very rarely do I try to discern spiral arms.

Love this image of IC 342. Credit: Credit: NASA/JPL-Caltech/J. Turner (UCLA)

Messier 58 - another barred spiral galaxy. But does not seem to have an inner ring. Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

Continuing my search for nearby barred spiral galaxies to compare to the Milky Way. Here's Messier 91. Credit: NOIRLab/NSF/AURA

I'm continuing on with my galactic structure experiments. I've been looking at another paper on HII regions in the inner galaxy. ui.adsabs.harvard.edu/abs/2009ApJ....

It's just over a year since we joined @bsky.app. Check out our updated #StarterPack and see what's changed!

Interesting. In my experience astronomers tend to oversell their research so that "here's an interesting new theory to investigate" becomes "we have revolutionized astronomy". But it *is* an interesting theory to investigate. ras.ac.uk/news-and-pre...

A beautiful image of a galaxy with a prominent inner ring and fragmentary spiral arms. Not that I think that the Milky Way looks like this but another example of how diverse the structure of disk galaxies can be.

A few days ago I put up a 12 kpc map of the Milky Way using masers (blue), an estimated bar position and a new catalog of about 500 HII regions with Gaia-derived distances (red). Here's an enhanced version of that including star density from a new OB star catalog. The galactic centre is down.

With the availability of a new catalog of about 500 HII regions with Gaia-derived distances, I combined them with masers out to 12 kpc as explained a couple of days ago and have been tweaking my two arm Milky Way schematic. Here is the latest version.

I still don't see the point of Artemis and I expect that I never will.

I just heard recently that the Andromeda galaxy is a barred spiral galaxy. That was not so obvious to me in visual images or even in this Spitzer infrared image.

I mentioned a few weeks ago that a research term have finally put out a catalog of about 500 HII regions with Gaia-derived distances. Here's an image out to a radius of 9 kpc that I created in Blender with the galactic centre to the right.

We've haven't found many or any truly Earth-like planets but that doesn't mean that they are rare. They are just hard to detect using our current techniques. A new experiment is trying something different.

Yikes. In this letter, Michele Dougherty, who among other roles is the current Astronomer Royal, is asking UK astronomers to prepare for up to 60% cuts. Granted, she also mentions flat funding as a possibility but the fact that a 60% cut is even mentioned must be incredibly demoralizing.

I hope I live long enough in good health to be able to see some of these results!

Astronomy needs some good news and this is the best!

I usually produce maps using highly luminous hot OB stars. Just for variety, here is a density map based on a larger set of stars - everything warmer than the Sun. I've labelled three mysterious regions that Gaia DR4 might help us understand,

This afternoon I am reading papers proposing that the inner Milky Way is dominated by a bar surrounded by a prominent ring. So a bit like Messier 95.

Busy today labelling bits of the hydrogen HI4PI lbv models in my new HI4PI VR world.

I've started working on an article on Gaia DR4 and the outer galaxy for February and to give away the conclusion in advance: my revised model of the Milky Way looks like this, but the usual caveats apply: there are limited masers available, and HI4PI velocity does not derive from rotation alone.

In a recent musing on HI4PI and the outer galaxy I mislabeled some spiral structures (I said in the post that I was not sure about it). Actually there seems to have been a consensus about the labels in the first and second quadrants for the positions of the Perseus and Outer arms.

Keep an eye on our website (www.camras.nl) and this account for the official announcement of the CAMRAS-seminar which takes place 14 March. The title is 'Waterstof in je achtertuin', the subject is amateur observing of the neutral hydrogen line. The event will be mainly in Dutch. #savethedate

I've been invited to show off some of my VR visualizations at the ASTRON / CAMRAS event at the Dwingeloo radio telescope on 14 March. So excited to get to see Dwingeloo again and to meet some key radio astronomy people in the Netherlands.

Just played a round of Zoo Vadis with my wife and two friends visiting from the UK. My new favorite game. #boardgames

This year on Bluesky I wrote 263 posts and 732 replies. I received 2,344 likes, whereas 58 was from my most popular post, and apparently I love saying "star" and 😆! www.madebyolof.com/bluesky-wrap...

Now that I've put up my big article on the inner galaxy, I'm looking at the outer galaxy. This entails a mystery that I've long wondered about: the asymmetry of the Milky Way. Looking at the hydrogen distribution it appears that the Milky Way has only one major spiral arm, the Perseus arm.

I've put up one of the most ambitious (and lengthy) articles I've written on the Milky Way. The timing works out well because this year is the 75th anniversary of the detection of the 21 cm line, one of the events that started the Golden Age of galactic cartography. kevinjardine.dev/blog/post-16/

Somehow I missed this. Looks exciting. ui.adsabs.harvard.edu/abs/2025A%26...

Tomorrow I'll be releasing one of the most elaborate articles I've ever written, on Gaia DR4 and the inner galaxy. I had intended it to be a short piece on what DR4 might be able to add to our knowledge of the inner galaxy. But then I asked: wait, what do we actually *know* about the inner galaxy?

Things I want more than Greenland as an American: •Affordable Housing •Universal Healthcare •Ability to travel and explore •Chance to pursue passions not money •To make a difference in other people’s lives So I want #StarTrek The future Gene Roddenberry envisioned

What a dream it would be to one day have the entire hydrogen-alpha sky accessible at this resolution.

Got another ringed bar. If you start to look they are everywhere. IC 2560.

Was just reading W . B. Burton's paper: "A Kinematic Method for the Derivation of the Galactic Distribution of Hydrogen" ui.adsabs.harvard.edu/abs/1971BAAS... Here is figure 13 overlaid on recent maser and Gaia data. This paper ended the Golden Age of galactic cartography that started in 1951.

I keep reading Burton and Shane 1970 over and over and I don't understand how to combine the Sagittarius arm fragments shown in figures 3 and 12. Maybe the point is that they can't be combined into a consistent spiral arm pattern? Not clear to me. ui.adsabs.harvard.edu/abs/1970IAUS...

So far as I know, this radio contour map from Van de Hulst, Muller and Oort 1954 is one of the first radio contour maps of the outer galaxy ever published (maybe the first). Posting this overlay on current data as a reminder for my article on Gaia DR4 and the outer galaxy later this year.

Found this very interesting paper from 1952 by Oort and Muller where Oort speculates on the structure of the Milky Way. ui.adsabs.harvard.edu/abs/1952MNSS...

After following up on citations I've found this beautiful Milky Way map from 1958. It is I believe to be the earliest "real map"(showing actual regions and not just race track lines). Created by Van de Hulst, the discover of the 21 cm line.

Maarten Schmidt's 1957 paper "Spiral structure in the inner parts of the Galactic System derived from the hydrogen emission at 21-cm wavelength" is in ADS but is missing Plates A and B. Does anyone have those?

For my article next week, I'm showing maps created during the Golden Age of galactic cartography (1951 - 1970) overlaid on the latest data. To do this I've created this new map showing Gaia data, masers and the position of the bar determined by Gaia, with the typical GC down Golden Age orientation

The race track model of the Milky Way of concentric arm-like structures, which has its origins during the Golden Age of galactic cartography and has haunted astronomy ever since, is like the Bohr model of the atom, simple, elegant and wrong.