How can astronomers know exactly how hot stars are? You can guess from their colors, but to get a precise measurement, you have to look at their spectra.
We spread out the light from the stars into a rainbow-like spectrum and look for patterns of lines, made by different elements and molecules in the star's outer layers. The presence or absence of lines tells you the precise temperature. 1/
Here are some actual stellar spectra, arranged by temperature. The hottest stars are at the top, coolest stars are at the bottom. The letters on the left are βspectral types,β a classification of stars based on their spectra.
Note how certain lines appear and then fade out as we go down in temperature. Most of the lines are caused by single elements. At the very bottom, we start to see bands of lines. Those are from molecules in the outer layers of stars. 2/
Why do we see lines? We will have to get into a little atomic physics.
As starlight shines through the outer layers of the star, the gas there will absorb photons that have exactly enough energy to bump their atomsβ electrons up to higher energy levels. The energy levels are different for each type of atom.
Since there are fewer photons at certain wavelengths that leave the star, we see narrow, dark lines. 3/
This is also interesting in the context of #astrophotography where we are capturing the light emitted by the inverse phenomena in emission nebulae (explained in the linked article).
Is there a standard nomenclature for these absorption/emission lines, e.g. alpha & beta for hydrogen vs iii in Oiii for Oxygen emissions? Does it correspond to the number of energy level changes the electrons undergo?
At visible wavelengths, the Balmer series is the most important (HΞ±, HΞ², HΞ΄, etc.) At UV wavelengths, the Lyman series is important (LyΞ±, LyΞ², LyΞ΄, etc.) And at IR wavelength the Paschen series is important (PaΞ±, PaΞ², PaΞ΄, etc.) en.wikipedia.org/wiki/Hydrogenβ¦
Most other elements are designated by their ionization state and wavelength in angstroms. For example: HeII 4686 He I = neutral helium He II = singly-ionized helium He III = doubly-ionized helium
Some lines are known as forbidden lines. These are normally disallowed, by the rules of quantum mechanics, but can be quite common in the very sparse gas found in astronomical objects, like nebulas. en.wikipedia.org/wiki/Forbiddeβ¦
These are designated by brackets. One common forbidden line is the oxygen doublet [OIII] 4959 and [OIII] 5007
Thank you! Now I understand the difference between the Balmer series used to designate Hydrogen emission lines and the ionization state used to designate the Oxygen and Sulfur emission lines, the most common emission lines we capture in amateur astrophotography.
Canada would be more than happy to help to thank you for the assistance received lately (If only we had #Wildfires under control & could spare teams & equipment)
I'm posting this graph by Eliot Jacobson here because I think it's truly remarkable how strong this outlier is growing to be.
It means that #sea temperatures are extremely unusually higher than normal, and the departure from the historical record is almost off the charts. #climatechange #heat
The effects? I couldn't tell you, but I do get the idea that it won't be very pleasant
Meta - the tech giant from Silicon Valley that is heavily criticized for privacy violations - is finally seeing some real headwind; but not from the EU. The small country of Norway is taking on the tech giant.
Out now! This calendar includesΒ tarot deck illustrations from my tarot deck in development. - Limited Edition of 100 calendars. - All calendars will be signed and numbered by the artist.
Ready to dive into the clearest waters this summer? Most bathing water sites in #Europe meet the EU's excellent water quality standards.
Since the adoption of the Bathing Water Directive in 2006, the proportion of excellent sites has increased to 86% of all bathing waters in the #EU. This means more protection for your health and the environment.
Check our interactive map for the status of bathing waters in each country: europa.eu/!dJqTgQ
beaches.ie has the best places to swim, with the latest bathing water quality, tides, weather and accessibility information for Ireland's beaches and lakes.
DE: Hallo EU-Kommission. Mal eine Frage am Rande: warum gibt es eure Infos eigentlich nur in Englisch, wo die EU doch deutlich mehr AMTs-Sprachen hat?
EN: Hello EU Commission. A question on the side: why is your information only available in English, when the EU has many more OFFICIAL languages (and English is just a very small one meanwhile)?
Hallo @CafeJunkie! Vielfalt und Mehrsprachigkeit sind uns wichtig. Jedoch wird dieser Social-Media-Kanal aus praktischen GrΓΌnden nur auf Englisch betrieben und nicht in allen 24 offiziellen EU-Sprachen. Unsere Kollegen in den EU-Vertretungen der Mitgliedstaaten fΓΌhren fΓΌr jedes Land einen eigenen Social-Media-Kanal. Diese KanΓ€le sind in allen 24 offiziellen EU-Sprachen verfΓΌgbar.
Hi @CafeJunkie! We are dedicated to diversity and multilingualism, however, this particular social media page is in English as for practical reasons it is not feasible to do it in all 24 official EU languages. Our colleagues in the EU representations in the Member States run a separate social media channel for each country. These channels are available in all 24 official EU languages.
The Luddites of 19th century Britain weren't anti-technology, which is the common perception nowadays -- they destroyed machines not because they didn't like them, but as a form of protest; what they *really* were after was better working conditions, and a more fair share in the gains from those machines. See the wikipedia entry, or, say, locusmag.com/2022/01/cory-doct….
We have the exact same dynamic today. But it's not about weaving machines -- it's about health care.
From "The Moral Crisis of America's Doctors",
... show more
Doctors are Luddites -- and that's a good thing!
The Luddites of 19th century Britain weren't anti-technology, which is the common perception nowadays -- they destroyed machines not because they didn't like them, but as a form of protest; what they *really* were after was better working conditions, and a more fair share in the gains from those machines. See the wikipedia entry, or, say, locusmag.com/2022/01/cory-doctβ¦.
We have the exact same dynamic today. But it's not about weaving machines -- it's about health care.
"In the past, one privilege conferred on physicians who made these sacrifices was the freedom to control their working conditions in independent practices. But today, 70 percent of doctors work as salaried employees of large hospital systems or corporate entities, taking orders from administrators and executives who do not always share their values or priorities."
It's the exact same dynamic. Doctors are no more opposed to fancy health care tech than the weavers were opposed to fancy weaving tech; they just want to have a fair say in their working conditions, and want the power to put their patients' interests first.
(Consider the story from the article of the doctor who had dying patient whose family could not be there. She stayed with him and held his hand as he died. Do you want a health care system where doctors can't do that?)
...and, holy coincidence, Batman: as I write this, at this very moment, I'm listening to @radiofreefedi and the song is "Trapped in a Patient Portal" by @jasondidner...!!
All latitude bands observed anomalous warmth in June 2023. The largest positive departure were near the Antarctic Peninsula.
Plot shows zonal-mean surface air temperature anomalies (1951-1980 baseline), where latitude = x-axis (not scaled by distance). Data from GISTEMPv4 at data.giss.nasa.gov/gistemp/.
Big Tech can legally store your data in the US again - though it is at risk of mass surveillance there.
This does not affect Tutanota: We store all your data on our own servers here in Germany. Unlike most services, we do not use Big Tech cloud services (like AWS or Google), but have full control over our own infrastructure.
Shout out to @radiofreefedi for introducing me to so many awesome new Fedi #artists in so many genres. I usually can only listen for 20 minutes at a time as Iβm doing chores, and itβs great to hear such a wide variety of #music that I just couldnβt get from a commercial station that only plays 2-3 genres, or even streaming algorithms that still canβt understand that I crave novelty, not just more of the same. And no ads filling up my precious time! #FediMusic
@KydiaMusic Warms our heart to hear the drop-in and discover model resonating so nicely!
It's an honour to have you as an artist and listener and love hearing experiences so indicative of the amazing support abound in the community that has lifted up #radioFreeFedi and each other as fedi artists
in case whatever stage of your weekend could use some friendly chat and some fun tune discovery.
We can talk about some of the new things coming. Maybe some artists will stop through and say hi. Maybe we can trade secrets for the softest ever shirt laundering. Or just hang and listen. All welcome.
radio free fedi is small web, consent driven, artist populated, non-commercial mechanism, attribution promoting, community radio for the fediverse. This stream is for the main channel simulcast, hangouts and chat, and special events.
#Antarctic sea ice remains on its own this year compared to any other July in our satellite record. Keep in mind when looking at this graph that the y-axis interval is 1,000,000 kmΒ². This is a massive deviation from the previous record for the date.
I wonder how many millimeters of sea level rise that much less sea ice might correlate although does less ice on the water reduce sea level? Anyways, it's not good imo.
Polar ice isnβt all the same - it can be divided roughly into βland iceβ and βsea iceβ. What matters most for sea levels is how much ice slides off the land and melts in the sea.
Yeah, I know that intuitively (ice cubes in a glass of water and all), but I was just wondering where all that water that would have been locked away as sea ice in the last decades is now I suppose.
@GreenFire Melting sea ice has a small influence on sea level because floating ice displaces the amount of water it would add to sea level. What changes the sea level is melting land ice and warming water (thermal expansion). But when sea ice melts, it's reflection rate (albedo) decreases, because dark water absorbs much more of the solar energy while white ice reflects nearly all energy. That leads to mentioned thermal expansion.
@Geonitiv Yeah, I know that intuitively (ice cubes in a glass of water and all), but I was just wondering where all that water that would have been locked away as sea ice in the last decades is now instead of being concentrated at the poles.
Those water molecules have to go somewhere, but perhaps our atmosphere is retaining that much more?
Antarctic sea ice extent hit a record low extent in February, but thanks to large natural variability from year to year, experts say there is still no long-term trend.
@Geonitiv I was thinking that the sea ice was formed from precipitation, but that's probably not the case and it is probably partially de-salted sea water which would not affect the overall water distribution around the globe which is what I was thinking. sorry.
Precipitation is expected to increase far more over the twenty-first century in the Arctic than the global average; climate models show that this is driven mainly by increased local evaporation and sea-ice retreat, rather than by increased moisture tβ¦
Almost a third the area of Europe lower than the baseline average, if I've got my maths correct (based on your other graphs that have been shared showing the anomaly).
This is another deeply concerning story of an outlier track, that is only surpassed in its shock value by the silences & misleading stories of the outlairs who shape opinion from right wing mainstream medias worldwide.
After several data protection agreements between the EU and USA have already failed, they are now venturing another attempt with the Data Privacy Framework. But US surveillance - the underlying problem of the data sharing agreement - has not miraculously dissipated in the meantime.
That's why the new Data Privacy Framework is doomed to fail - and that is a good thing!
All data are referenced at My visualizations: Arctic Climate Seasonality and Variability Arctic Sea Ice Extent and Concentration Arctic Sea Ice Volume and Thickness Arctic Temperatures Antarctic Seβ¦
If I started Thesis Whisperer today, 10th of July 2023, you would never hear about me. I built a readership in my little corner of academia, and some measure of influence, by sharing my work onlineβ¦
Detail in all its glory.
Kelly Lepo
in reply to Kelly Lepo • • •Here are some actual stellar spectra, arranged by temperature. The hottest stars are at the top, coolest stars are at the bottom. The letters on the left are βspectral types,β a classification of stars based on their spectra.
Note how certain lines appear and then fade out as we go down in temperature. Most of the lines are caused by single elements. At the very bottom, we start to see bands of lines. Those are from molecules in the outer layers of stars.
2/
Image from: noirlab.edu/public/images/noaoβ¦
OBAFGKM
www.noirlab.eduKelly Lepo
in reply to Kelly Lepo • • •Why do we see lines? We will have to get into a little atomic physics.
As starlight shines through the outer layers of the star, the gas there will absorb photons that have exactly enough energy to bump their atomsβ electrons up to higher energy levels. The energy levels are different for each type of atom.
Since there are fewer photons at certain wavelengths that leave the star, we see narrow, dark lines.
3/
Learn more: webbtelescope.org/contents/artβ¦
Julien :ve: π:python:
in reply to Kelly Lepo • • •Very interesting and well explained!
This is also interesting in the context of #astrophotography where we are capturing the light emitted by the inverse phenomena in emission nebulae (explained in the linked article).
Is there a standard nomenclature for these absorption/emission lines, e.g. alpha & beta for hydrogen vs iii in Oiii for Oxygen emissions? Does it correspond to the number of energy level changes the electrons undergo?
Kelly Lepo
in reply to Julien :ve: π:python: • • •There is a system, it is confusing.
Hydrogen lines get their own names.
At visible wavelengths, the Balmer series is the most important (HΞ±, HΞ², HΞ΄, etc.)
At UV wavelengths, the Lyman series is important (LyΞ±, LyΞ², LyΞ΄, etc.)
And at IR wavelength the Paschen series is important (PaΞ±, PaΞ², PaΞ΄, etc.)
en.wikipedia.org/wiki/Hydrogenβ¦
1/
important atomic emission spectra
Contributors to Wikimedia projects (Wikimedia Foundation, Inc.)Kelly Lepo
in reply to Kelly Lepo • • •Most other elements are designated by their ionization state and wavelength in angstroms. For example: HeII 4686
He I = neutral helium
He II = singly-ionized helium
He III = doubly-ionized helium
2/
Kelly Lepo
in reply to Kelly Lepo • • •Some lines are known as forbidden lines. These are normally disallowed, by the rules of quantum mechanics, but can be quite common in the very sparse gas found in astronomical objects, like nebulas. en.wikipedia.org/wiki/Forbiddeβ¦
These are designated by brackets. One common forbidden line is the oxygen doublet [OIII] 4959 and [OIII] 5007
3/
spectral line associated with absorption or emission of light by atomic nuclei, atoms, or molecules
Contributors to Wikimedia projects (Wikimedia Foundation, Inc.)Kelly Lepo
in reply to Kelly Lepo • • •Except for the forbidden lines (which are only emission lines), these names are used for both absorption and emission lines.
4/
Julien :ve: π:python:
in reply to Kelly Lepo • • •Julien :ve: π:python:
in reply to Julien :ve: π:python: • • •Follow-up question:
In the different emission nebulae images taken with the NIRCam instrument (like webbtelescope.org/contents/medβ¦), what emission lines are captured?
Do the hydrogen an other atoms also emit in infrared?
Looking up the Balmer series on Wikipedia, the hydrogen emission lines start in the visible (red) and extend into UV but not in IR.