Peter Laursen

Distance measures in cosmology Formulae for the line-of-sight and transverse comoving distances, proper motion distance, angular diameter distance, luminosity distance, k-correction, distance modulus, comoving volume, lookback time...

I was very confused for too long, until I realized we weren’t talking about the author of possibly the highest-cited non-refereed paper in cosmology (arxiv.org/abs/astro-ph...).

Actually it was almost completely clouded, but there was a small hole I the clouds I tried to take advantage of, but failed.

Luckily they didn’t question what I was doing with a telescoping a cloudy evening 😄

Four police officers came to my building because a person had been spotted with a suspicious instrument.

It was me and my telescope, trying to image C/2025 Lemmon.

I surrendered unconditionally.

Planetmæssigt kommer Saturn og Neptun op tidligt. Neptun kræver dog en kikkert, men står lige ved siden af Saturn

Jupiter og Venus som bliver flottest, også lige ved siden af hinanden (1°), står op ca. 2:30.

Punktet hvorfra meteorerne kommer (“radianten”) stiger højere op på himlen i løbet af natten, så flere stjerneskud ud på morgenen. På den anden side kommer en næsten fuld Måne også længere op og spolerer det lidt.

Så stjerneskudsmæssigt ville jeg gå efter det mest skyfri tidspunkt.

First light from student-built radio telescope - Cosmic Dawn Center During the last six months, academic employee Gaurav Kumar, together with master students Kaj Grimstrup, Liazhe Li, and Omar Rashdan, have built two radio telescopes. One of them now observed its firs...

Behold the homemade 1.9 m radio telescope, built by DAWNers Gaurav, Kaj, Jiazhe, and Omar📡

The telescope received its first light last week, where the team was able to observe neutral hydrogen in the Milky Way from the institute's backyard.
cosmicdawn.dk/news/first-l...
@dg.dk

I like Lyman α for many reasons, including its ability to probe reionization:

James Webb giver ny indsigt i galaksernes vækst og deres mørke stof - Cosmic Dawn Center Kortlægning af en kosmisk historie: Et internationalt hold af forskere, ledet af astronomer på Cosmic Dawn Center i København, har udgivet et omfattende studie af, hvordan galakser og deres mørke stof...

In an extensive study on galaxy evolution through cosmic time, Marko Shuntov presents a plethora of interesting result, including how the total mass of the galaxies' stars and dark matter are related?

🇬🇧 cosmicdawn.dk/news/new-ins...
🇩🇰 cosmicdawn.dk/news-in-dani...
@dg.dk

Amazing! I love how the long exposure lets you see the stars’ temperatures 🤩

Fair point :)

Right, if you're aiming to illustrate peak wavelength it makes sense. I just meant that O stars don't look purple to the human eye, so *personally* I would prefer a Planckian locus color scheme :)

Nice! Is that all 1½ billion stars (or how many the full sample is)?

One comment: Personally I prefer HR diagram with "real" colors, i.e. how it would look to the human eye. Blackbodies tend to be red below a few 10³, white at T☉, and saturate at a pale blue above ~10⁴ K. And never green or violet.

I just came back from Tromsø where I saw this. It was absolutely amazing 🤩 Flickering and shimmering around us. Even the red colors were visible to the naked eye!

More like STONEDWACK (aSTrONomErs Don't understand hoW ACronyms worK).

…then proceeds to hit the Klein bottle.

Ha ha ha I was somewhat confused 😄

Jeg fik engang at vide, at jeg var tabt bag af en vogn…

You might be consistent, but you’re incomplete. Unrecoverably sick 🔥

With four kids, they need all the support they can get 😓

I think I have four different Dinosaur Comic T-shirts :)

I love them! But… has it really been 20 years… 😬🫠
I just turned old…

3/3
I describe how astrophysics is hard because of the huge span of timescales, but easy because of the huge span of timescales.

There's also an account of the first ~half year of galaxy observations with James Webb.

And lots of illustrative figures that you can use in your talks👍🏽

2/3
Context:

The article is a chapter in a multidisciplinary anthology, "Multiplicity of Time Scales in Complex Systems", aimed at non-astronomer scientists, but may also be fun for astro-students.

And "island" is also a hat-tip to "island universes"…🙂

1/3
I wrote my first single-author article, and I'm proud to say the a reference to Jon Bon Jovi
made it through peer review 😃

arxiv.org/abs/2309.02486

2/3
Context:

The article is a chapter in a multidisciplinary anthology, "Multiplicity of Time Scales in Complex Systems", aimed at non-astronomer scientists, but may also be fun for astro-students.

And "island" is also a hat-tip to "island universes"…🙂

I describe how astrophysics is hard because of the huge span of timescales, but easy because of the huge span of timescales.

There's also an account of the first ~half year of galaxy observations with James Webb.

And lots of illustrative figures that you can use in your talks👍🏽

Context:
The article is a chapter in a multidisciplinary anthology, "Multiplicity of Time Scales in Complex Systems", aimed at non-astronomer scientists, but may also be fun for astro-students.

And "island" is also a hat-tip to "island universes"…🙂

Never had one until I got this recently :)

Agree!

Thanks, I needed this 😭