Markus Pössel
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mpoessel.de
Markus Pössel
@mpoessel.de
12K followers 800 following 18K posts
Astronomy and relativity outreach (Tweets in German & English) | personal account | he/his | managing scientist @hausderastronomie.bsky.social | director @astro4edu.bsky.social |outreach @mpi-astro.bsky.social | Seestar enthusiast
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mpoessel.de
The effect can also be seen clearly in the binars pulsar and in a pulsar-plus-white-dwarf binary - that‘s a really cool and precise test. :-)
Curves showing the Shapiro time delay as a function of orbital angle for the binary pulsar, the NS-WD binary, and the Hulse-Taylor pulsar
November 13, 2025 at 8:58 PM
mpoessel.de
Das hier ist die betreffende Stelle. Dass Stanley nicht Gegenwind-in-Talkshows meint sondern das erwähnte keine-Bühne-geben bzw. die-vorgesehene-Bühne-entziehen scheint mir da recht eindeutig.
Die jüdische Schriftstellerin und Journalistin Masha Gessen wurde kürzlich mit dem Hannah-Arendt-Preis ausgezeichnet. Die Preisverleihung wurde jedoch abgesagt, da sie in einem Artikel eine Analogie zwischen Gaza und dem Warschauer Ghetto gezogen hatte. Aber auch Hannah Arendt erkannte die Ungleichbehandlung der Palästinenser deutlich und befürwortete einen Staat, der Juden und Palästinensern die gleichen Rechte als gleichberechtigte Bürger einräumt. Hannah Arendt dürfte heute in Deutschland nicht mehr sprechen. Albert Einstein unterstützte einen binationalen Staat mit freier Einwanderung für Palästinenser und Juden. Auch er dürfte heute in Deutschland nicht mehr sprechen.
November 12, 2025 at 7:32 PM
mpoessel.de
I think likening that to a superposition of quantum states doesn't work. In the quantum case, make a measurement and you will end up either with one or the other. What you are describing is worse: it starts out and will remain inconsistent. Let's call it the Whitman approach to causal inference!
Excerpt from Walt Whitman's "Song of Myself": "Do I contradict myself? Very well then I contradict myself, (I am large, I contain multitudes.)"
November 11, 2025 at 11:52 AM
mpoessel.de
Going through old images, and apparently, I was considerably younger 13.5 years ago?
Selfie with DSLR showing Markus's reflections in the mirrored exterior of a ship on Lake Constance.
November 9, 2025 at 10:25 PM
mpoessel.de
They‘re right! The generator *is* fun!
Mamdami-Style „V for Vendetta“
November 8, 2025 at 11:22 PM
mpoessel.de
Wir sollten offener und häufiger über die plutokratischen Züge unseres politischen Systems reden. Freue mich daher, dass das Problem hier zumindest kurz angesprochen wird. Geld, das zu Einfluss wird, ist kein Automatismus, sondern eine Konsequenz unserer (ggf. fehlenden) Regeln. 1/
Screenshot des Textausschnitts "Diese Konzentration von Vermögen führt nicht nur zu sozialer Ungleichheit, sondern auch zu politischer Ungleichheit: Geld wird zu Einfluss. Und das prägt die Demokratie tief."
November 7, 2025 at 9:41 AM
mpoessel.de
OK, so now we have three additional sources. Two of them get Peter Desaga's name wrong (Britannica and Allchin), and one erroneously makes him Bunsen's laboratory assistant (Allchin) - neither of which inspires much confidence :-/

The third article (Williams) ascribes the design to Bunsen. 1/
Since the burners then in use produced smoky flames and gave low heat output, Bunsen undertook the task of designing an acceptable device. Two coworkers joined Bunsenn his endeavor: Henry Roscoe, a student, and Peter Desaga, the university's instrument maker.
November 1, 2025 at 11:34 PM
mpoessel.de
OK, I suspect I might have used a slightly wrong setting on this one. Bunsen's former (custom-built) laboratories in the background, by the way. Where the fact that these newfangled buildings had a gas connection inspired him to design the Bunsen burner.🧪⚛️
October 31, 2025 at 11:52 PM
mpoessel.de
OK, here is my Ozymandias contribution:

What shall I name thee, ill-shaped lump of stone?
You are decayed, half hidden in the sand,
your visage shattered, wrinkled lips a-frown,
and, seriously: sneer of cold command?

(complete version in image/alt text)
What shall I name thee, ill-shaped lump of stone? You are decayed, half hidden in the sand, your visage shattered, wrinkled lips a-frown, and, seriously: sneer of cold command? Who are we kidding? All of us await when despots sneer, and brag, and have a ball, that such behavior meets deservéd fate, with hubris promptly followed by a fall. You stamp your name on sundry lifeless things. You claim the truth while speaking lie and lie. You claim your seat as mighty king of kings. Your cronies help you out all they can buy. You tell us to despair? We tell you: nope. We see those trunkless legs, and we take hope.
October 30, 2025 at 9:02 PM
mpoessel.de
with a smartphone no less, between 14 August 2022 and 5 April 2023, by the winner of our 2023 @astro4edu.bsky.social educational astrophotography contest in the category "smartphones", Rob Kerby Guevarra. Image credit is Rob Kerby Guevarra/IAU OAE (CC BY 4.0) under license CC BY 4.0. 3/
A small part of the sky that includes the Pleiades, with several copies of the same reddish dot, which is Mars, in different positions. The positions form a loop, with Mars doubling back before moving on. The image is "Retrograde motion of Mars," Image credit: Rob Kerby Guevarra/IAU OAE (CC BY 4.0)
October 28, 2025 at 11:17 PM
mpoessel.de
Later today, I'll do an introductory lecture on planet motion in the solar system. Here is an animation I prepared for that. It shows, to scale, the orbits and motion of Earth and Mars. The yellow line is the direction in which we here on Earth observe Mars. And as you can see in the video, 1/ 🧪🔭🎢
October 28, 2025 at 11:17 PM
mpoessel.de
I just made this video for my astro-for-non-physicist course on the solar system, to illustrate celestial motion. The separate clips are all winners/honorable mentions of the @astro4edu.bsky.social astrophoto contest 2022. So nice to have this material! 🧪🔭🎢
October 26, 2025 at 9:45 PM
mpoessel.de
Others find peace and calm in knitting, I find it in preparing slides for my astronomy lectures for curious non-physics students :-)

I'm quite pleased with my step-by-step spectroscopy slide, which starts with a "spectral glasses" photo and goes from there to a spectrum-as-diagram. 🧪🔭⚛️
Lecture slide. Bottom left is a photograph taken through spectral glasses: a slit cut in a piece of cardboard, and spectral lines from an overhead lamp. The slide progresses from there to a picture showing just the spectral lines, now rotated so that blue is left, red is right; then the black-and-white-version, and the right half of the slide is a double image showing a (stretched) version of the spectral lines photograph and below a diagram plotting intensity against wavelength, which is aligned with the stretched-version image and shows maxima where there are bright lines in the image.
October 25, 2025 at 10:12 PM
mpoessel.de
Erinnerte mich an das berühmte Wikipedia-Beispiel aus en.wikipedia.org/wiki/Scottis... - wobei die Bildunterschrift da ja leider inzwischen geändert wurde.
Picture showing a penguin (left) and a human with a bagpipe (right) on the antarctic ice, with the caption "Piper Kerr (right) posing with bagpipes and a penguin, March 1904".
October 24, 2025 at 1:18 PM
mpoessel.de
I had completely forgotten that I drew an elaborate title page for my summer school notes on the topic of entropy, 30 years ago.
Drawing of a village in the alps, with the title „Entropy“ and a small and complex thermodynamic machine near the top. Detail from the previous picture, with the machine shown a bit larger than before.
October 23, 2025 at 11:24 PM
mpoessel.de
S. 278 in dem verlinkten Dokument https://open.ifz-muenchen.de/server/api/core/bitstreams/e8b641bb-f7e8-4775-aab6-36be1553d9bf/content
Textausschnitt aus dem verlinkten Goebbels-Tagebuch u.a. mit der Aussage zu 76000 Juden, die sich „zum größten Teil als Parasiten“ in Berlin „herumtreiben“. „Sie verderben nicht nur das Straßenbild, sondern auch die Stimmung.“
October 18, 2025 at 9:13 AM
mpoessel.de
Acting Prussian interior minister (and major Nazi) has published a decree, directed at the police forces under his command. Vossische prints that decree in full. It's not all that long. 3/
Screenshot of the Vossische Zeitung article "Police decree with wide-ranging consequences". The text itself, in translation, is given in the following posts of the thread.
October 10, 2025 at 5:59 PM
mpoessel.de
I find triangulum difficult to work with in general. Hard to tease out the details. This is how far I've gotten so far with the S50, but at some point I'll try again!
Triangulum galaxy looking unsatisfyingly fluffy.
October 6, 2025 at 10:29 PM
mpoessel.de
Nice! I "harvested" three galaxies (and a bit) a few days ago with the S30. I like to include fresh galaxies in my introductory lecture, and will put the S30 on the table at the start of tomorrow's lecture to show that it doesn't really take a lot to see and image galaxies! :-)
Two galaxies, M81 a spiral and M82 seen from the side, in a small image. The open spiral of M101 in a small image. Image with the elliptical galaxy M110 top center, and parts of the Andromeda galaxy M31 below.
October 6, 2025 at 10:26 PM
mpoessel.de
New this year in my galaxy basics lecture: a slides about how pretty pictures lie shamelessly about true brightness profiles. Dynamic range for galaxy pictures is soooooo much more than the made-to-look-nice images imply! 🧪🔭

(M81 images with Celestron Origin, profile with SAO DS9)
Left: (fairly) raw image of the galaxy M81, with a green line that indicates where the profile has been measured. The measured profile is below: an exponential increase of brightness towards the center. Right: the same image of M81, but now in the version that was stretched to make it look pretty. The changed brightness profile, shown below, has a linear increase towards the center. The information about just how exponentially bright central galaxy regions are has gotten lost!
October 5, 2025 at 11:23 AM
mpoessel.de
What is your sign?

(In mine, the missing e is symbolic of the imperfections of reality when compared to ideals. It's like a memento mori thing.)
Screenshot of the website https://www.poessl-group.de/de/marken/poessl for comparatively well-known camper vans under the brand of Pössl (without the last e in Pössel). The image shows a camper van, and superimposed is the logo "Pössel" with an addition "das Original," meaning "the Original".
September 28, 2025 at 9:17 PM
mpoessel.de
Ich rätsele gerade über diese Passage. Soll das über ein Jahr gerechnet sein? Über die Lebenszeit von E-Auto/Wärmepumpe? Wer sonst per Gasheizung 4 Tonnen pro Jahr ausstieß, jetzt für 20 kEUR Wärmepumpe einbaut, die 15 Jahre nutzt, hat EUR 400 pro Tonne CO2-Vermeidung gezahlt.
Textpassage: "So koste eine Tonne CO2-Einsparung in Deutschland durch den Tausch einer Gasheizung für eine Wärmepumpe 1.200 Euro, ähnlich teuer sei die Förderung von E-Autos durch Steuervorteile oder gar Kaufprämien."
September 28, 2025 at 9:03 PM
mpoessel.de
Both my students and the astronomy community at large should be pleased to learn that my Gaia DR3 quasar sample near the galactic north pole does not contradict the large-scale isotropy of the universe. A simple binomial "am I more likely to find a quasar in the first quadrant as compared 1/🧪🔭
A plot of nearly 1000 dots in a small region of the sky. The dots appear to be distributed randomly.
September 26, 2025 at 8:15 PM
mpoessel.de
It's Andromeda / M31 season! Here is yesterday's haul with the S30 of @hausderastronomie.bsky.social - M31 and neighbourhood as a mosaic. Hoping to get about the same amount of photons today, to make the image less noisy overall! 🧪🔭
A spiral galaxy (Andromeda / M31) seen somewhat from the side. There is another elliptical galaxy close to it, halfway to the top of the image.
September 19, 2025 at 6:51 PM
mpoessel.de
Interesting panel discussion about scientific integrity with @lonnibesancon.bsky.social , Yukari Ito and Eusang Lee, moderated by Benjamin Skuse. #HLF25
Four people sitting in a row on a stage
September 19, 2025 at 8:35 AM