I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
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a question not directly connected to stars (but concerning mass in our universe):
Currently we "need" a lot of dark matter and dark energy to keep our universe models "running", but still have few ideas about both dark things and how to verify the various theories (WIMPs, axions, etc.).
Do you think we will find some day this type of matter and energy or do you think the answer is more lying in the area of MOND (modified Newtonian dynamics), TeVes, entropic gravity, so that some "constants" in the universe are not so constant as we think?
@echopapa sorry, as said, I'd like this one to be focussed on the stars topic
But re: dark matter & dark energy - keep an eye out on upcoming Euclid @ec_euclid results, I expect a lot of cool stuff in the next years. Also I heard the new book on "Dunkle Materie" (Beck Wissen) by @sianderl is very good, but haven't read it yet. -
I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg bearing in mind the two items I have heard/seen, viz.
1. There is a wave which is not captured by known black holes; and
2. That particle acceleration within our measurable frame is below that which would escape an event horizon, meaning we may be inside a black hole;What evidence is there for entropy to be incontestable?
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My understanding is that heavy elements were formed by super novas, and also that super novas are rare occurrences. How do these two facts(?) square up, given that we have a fair amount of them in Earth's crust?
@Enema_Cowboy that's because if you look overall into the solar system we still have a small amount of heavier elements - it's just that they are a lot more concentrated in the (rocky) planets than in the Sun where most (99.8%) of the overall material in the solar system is. So overall we still have only very little of heavier elements.
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@GranVegas actually, the metals (and thanks for using the astrophysical meaning of it, otherwise I always have to explain our strange terminology
) don't fall into the core - stars are pretty well mixed! And currently, we have still very, very little metals around.I guess if one were to start with a metal only cloud, one could possibly directly form a (cold) white dwarf, but that's a speculation and as said, we still have very little metals.
@vicgrinberg Ahh, I see, so statistically impossible. I remember reading some sci-fi about a generation ship decelerating into the solar system and poisoning the Sun with their reaction mass. " People of Earth we come in peace! Oops, snuffed out your star. Peace out."
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@vicgrinberg Ahh, I see, so statistically impossible. I remember reading some sci-fi about a generation ship decelerating into the solar system and poisoning the Sun with their reaction mass. " People of Earth we come in peace! Oops, snuffed out your star. Peace out."
@GranVegas ah
yeah, that one is likely to be veery far fetched (We did do some terrible sf film watching with scientist friends, it needed a lot of snacks and snark to survive some movies...) -
I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
@vicgrinberg This may be a dumb question but did our night sky look different to our ancestors thousands of years ago with different constellations?
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@echopapa sorry, as said, I'd like this one to be focussed on the stars topic
But re: dark matter & dark energy - keep an eye out on upcoming Euclid @ec_euclid results, I expect a lot of cool stuff in the next years. Also I heard the new book on "Dunkle Materie" (Beck Wissen) by @sianderl is very good, but haven't read it yet.@vicgrinberg @sianderl @ec_euclid
OK, but many thanks for your answer anyway!
Mhm, another question regarding red dwarfs (like Proxima Centauri):
Red dwarfs may sound harmless at first, but they are much more dangerous for nearby planets (and any potential life) due to intense flares and CMEs, as well as strong magnetic fields that fluctuate considerably.
Is the only reason for this that heat transfer in these stars is convective (meaning the interior is well “stirred up” and therefore rather inhomogenous ) or are there further reasons for this behaviour?
In stars like the Sun, heat transfer occurs internally via radiation and in the outer layers via convection, without things being so uncomfortable all around....
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@GranVegas ah
yeah, that one is likely to be veery far fetched (We did do some terrible sf film watching with scientist friends, it needed a lot of snacks and snark to survive some movies...)@vicgrinberg Thanks Dr. Grinberg. Enjoy your vacation.
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@vicgrinberg This may be a dumb question but did our night sky look different to our ancestors thousands of years ago with different constellations?
@coleenwalter it's a very cool question actually! The stars move relative to the solar system and the solar system itself moves through our galaxy, so overall the position of stars changes. The timescales are very large, though, so "just" a few thousand years ago things would not look too different, possibly not even noticeable with the nakes eye. But the further in the past you go (to pre homo sapiens time), the more different it would look - same for far away future!
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
What the heck are the Little Red Dots seen by the James Webb telescope? The February SciAm said they might be "a totally new class of cosmic object". Still True?
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I have a bit of time on my hands, so let's do another 24h round of #AskAnAstrophysicist, but this time it's a thematic one.
What do you want to ask an astrophysicist about stars? (I am a professional astrophysicist, part of whose work concerns itself with high mass stars & their winds and I've also taught a variety of astro university courses)
Boosts welcome. I may not be able to reply to all in case of many questions.
Is there any work amateur astronomers can still do that is at all useful to professional astronomy? I know that at one time, for example, gathering data on variable stars was worthwhile to some extent. Is it still or are the days of amateurs helping the pros long gone?
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@bkahn oh, there are still so many! I'll pick one I especially like: we do not understand the most massive stars that existed very early in the universe, when there were few heavier elements super well. Somehow, in their death, these stars have managed to create black holes that are just so bigger than we would have expectes - but we do have ideas what may be the cause, so we are working hard on finding out which one is correct.
@vicgrinberg @bkahn Interesting! So how do we know that these black holes were caused by single supermassive stars rather than having grown over time?
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Is there any work amateur astronomers can still do that is at all useful to professional astronomy? I know that at one time, for example, gathering data on variable stars was worthwhile to some extent. Is it still or are the days of amateurs helping the pros long gone?
@kitkat_blue the variable star monitoring is still very much done! https://www.aavso.org/observing-variable-stars
It's amateurs partially with very high end expensive equipment, I think, but still amateurs not professionals...
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@CASSCFenjoyer they certainly do! Even our sun does - it's the driver of the solar cycle and solar spots.
You can find more info here https://www.esa.int/Science_Exploration/Space_Science/The_solar_cycle_a_heartbeat_of_stellar_energy
And here is a really cool recent measurement https://www.esa.int/ESA_Multimedia/Keywords/Description/Sun_magnetic_field/(result_type)/images
