@vicgrinberg@mastodon.social
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vicgrinberg

@vicgrinberg@mastodon.social

Me:

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vicgrinberg, to random
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Ahem... 📢

Dear ppl - please do not repost stuff from accounts such as "amazing science", "wonders of science/nature", etc. OR posts that use these accounts as sources.

They are spoofers, stealing artwork without attribution, often misrepresenting highly photoshopped (or fully artificial) images as real and not so seldomly posting absolutely bogus explanations.

Nature is beautiful - it does not need Photoshop or wrong explanations to make it sound more sensational.

vicgrinberg,
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@RolloTreadway yeah. And what makes me even sadder are folks use these accounts on various pages as ligitimate sources of information, "but this is a well established scientific account" ... No, it's not. :(

vicgrinberg, (edited ) to random
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: Heute, beträgt die aktuelle Moorfläche (also Flächen, wo noch eine, Torfschicht vorhanden ist, einschließlich der trockenen Flächen, die den Großteil stellen!) in Deutschland 1.8 Millionen Hektar - bei einer Gesamtlänge Deutschlands von 35.8 Millionen Hektar.

Vor 300 Jahren waren es wahrscheinlich ca. 2 Millionen Hektar Moorflächen, wobei ein Teil durch Torfabbau und Entwässerung verloren gegangen ist.

  • Aus: "Das " von Franziska Tanneberger & Vera Schroeder
vicgrinberg, (edited )
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Von den heute verblieben 1.8 Millionen Hektar Moorflächen sind nur 2% naturnahe, nasse Moorflächen, meistens Naturschutzgebiete. 4% sind wiedervernässte Moorflächen - die also einmal entwässert waren, wo die Entwässerung aber gestoppt wurde. Das meiste - 94% - sind entwässerte, trockene Moorböden. Sie sind für ca. 6.7% der gesamten CO2 Emission in Deutschland verantwortlich.

vicgrinberg, (edited )
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4% der gesamten Landfläche der Erde sind mit Mooren bedeckt. Darin ist doppelt so viel Kohlenstoff gespeichert wie Bäumen aller Wälder der Erde zusammen.

Eine Karte gibt es hier: https://greifswaldmoor.de/files/dokumente/Global%20Peatland%20Database/GloPeMap_update_20210912_COP21_low%20res.png

Und mehr detaillierte Karten, z.T. mit Schwerpunkt Europa, hier: https://greifswaldmoor.de/global-peatland-database-en.html

  • Infos aus: "Das " von Franziska Tanneberger & Vera Schroeder
vicgrinberg, (edited ) to space
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Cecilia Payne-Gaposchkin, who revolutionized our understanding of what stars & the Universe are made of, was born in 1900.

In 1926, she wrote what is considered the "undoubtedly most brilliant PhD thesis ever written in astronomy".

She continued in the same spirit - only to be denied a professorship (or even the a proper astronomer position). She finally became a professor at Harvard at 1956(!) & first woman to chair a department.

vicgrinberg, to random
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So what kinds of black holes are actually out there?

vicgrinberg, (edited ) to science
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🥳

Where we use a method originally used for AGN to answer the question whether
we can use variability in individual X-ray lines to probe the variable stellar wind.

And the answer is: yes, we can!

The paper (submitted not yet refereed) is:

"Stellar wind variability in Cygnus X-1 from high-resolution excess
variance spectroscopy with Chandra" by Härer et al.
https://arxiv.org/abs/2304.14201

Let me disentangle what the title means: 1/6

vicgrinberg,
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"Stellar winds" - all stars, including our own Sun, have stellar winds.

Massive giant stars have especially strong ones, that can carry away a significant portion of a star's mass over its lifetime. These winds are highly structured and thus variable.

Understanding stellar winds is thus crucial to understanding the life of massive stars (who usually end their life spectacularly in an supernova explosion, producing a neutron star or a black hole). 2/6

vicgrinberg,
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"Cygnus X-1" is perhaps the most-known black hole (that we have updated the mass of: https://www.scientificamerican.com/article/astronomers-just-upsized-an-iconic-black-hole/).

But I'm also interested in its companion, a star of about 50 times the mass of the Sun, in a 5.6 day orbit with the black hole.

We can see lots of variability in the X-ray emission from the black hole - some is accretion physics close to the black hole, but a lot are clumps im the wind of the star passing in front of the black hole (see Fig. in first toot!)

Image credid: ICRAR

3/6

An artist’s impression of the Cygnus X-1 system, showing material from the star flowing towards the black hole and forming an accretion disk. Credit: ICRAR

vicgrinberg,
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"Excess variance" is the variance in a lightcurve above the expected statistical noise.

A lightcurve is a list of measurements of how bright the source is vs time; here, we make one measurement every 1.7 seconds. Excess variance then pretty much shows whether there is signal in the static noise.

By comparing excess variance for lightcurves at different energies, we can say at which energies have more or less signal to them.

4/6

vicgrinberg,
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"High resolution with Chandra" - @ChandraScience is an amazing X-ray telescope. If we use gratings on it, we are able to see details of lines from individual elements - this tells us what material is there but also how hot it is (as atoms are stripped of their electrons in especially hot or violent plasmas).

Here, we show that for a source as bright as Cygnus X-1, we can use Chandra to measure excess variable for individual ions. 5/6

vicgrinberg,
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How do we bring all these ideas together? We show that we can use excess variance and, comparing it to simulations that my colleagues I. El Mellah, I & collaborators have developed recently, use it to constrain wind properties.

This is a proof of concept paper, where we develop a new method and independently confirm its results. We also show that we need a proper treatment of ionization in the simulations in the future. So we'll get working on this soon!

6/6

vicgrinberg, to Cat
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It turns out are a lot like cats 😼 Especially, they play with their food 🐀

You don't believe me?

Remember how a plays with a mouse: catches it, releases it, catches it again, releases it again ... Turns out, black holes can do the same with stars: they can catch and partially disrupt a star, release it, wait until it approaches again, play with it a bit more, release it, wait for the next approach:

▶️ https://www.esa.int/Science_Exploration/Space_Science/XMM-Newton_spies_black_holes_eating_the_same_stars_again_and_again

vicgrinberg, to random
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2022 was not a good (reading) year. It started great and then Russia invaded Ukraine (again) and I lost the ability to focus on books. I kept correcting my reading goals down - in the end, it's 25 books this year, the lowest ever since kindergarten.

Still - I read some AMAZING books that I want to recommend. And to move my hashtag to the fediverse. First time in my life that all my favorites are non-fiction. These I somehow still can read 🤷‍♀️

Anyway, my favs in reading order:

1/8

vicgrinberg,
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  • Herbstmilch (Autumn Milk) by Anna Wimschneider

Autobiography of Wimschneider (1919-1993), a peasant woman from Southern Germany: simple language, originally written for her family - so both very intimate & likely much "cleaner" than reality - & later professionally edited.

An impressive reminder for what life was like for women whose lifetime overlapped with mine. It reads like something from long ago and yet my grandma (Jewish doctor) was 15 years older than Wimschneider.

2/8

vicgrinberg,
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  • Community-Kapitalismus - Silke van Dyk, Tine Haubner

Found this one via @DieVilla4. A well-argumented, thin book on how capitalism uses the idea of community to perpetuate itself and to off-load all the unprofitable (care-)work.

I'm extremely suspicious of communities in general (yes, especially the marginalized ones; been there, done that, have scars to show) even more so since my time in the USA. This gave me a good theoretical foundation for a part of the why.

3/8

vicgrinberg, to Astro
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We are all stardust.

That oxygen you breath? That comes from dying massive stars, ending their light in a supernova.

The iron in your blood? Some massive stars dying, but mainly white dwarfs, the leftovers of dwarf stars like our own Sun, exploding.

The gold ring on your finger? Mostly merging neutron stars, leftovers from supernovae.

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