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Halbhh

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I was into using my 3.5" refractor for a couple of years as a young teen (and got the surprise from Saturn that happens, which I had no idea I'd be able to see until the moment I saw it :) ), and then I got more into reading articles, and only used it a little after then, and have done little looking through scopes since those years. But I really enjoy astronomy articles and images, along with all sorts of astrophysics, especially the stuff I listed in the OP there.

Lately, a fun thing I've wanted to see more of are these computational simulations of 2 nuetron stars spiraling in to merge. (This simulation uses the mass estimates of a pair that recently merged)


Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut)
Published on Oct 16, 2017

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The video shows a numerical simulation representing the binary neutron star coalescence and merger which resulted in the gravitational-wave event GW170817 and gamma ray burst GRB170817A. The two non-spinning neutron stars shown in the animations have 1.528 and 1.222 solar masses and follow the ALF2 equation of state (EOS). The employed parameters (total mass, mass ratio, spin and EOSs) are consistent with the detection made on the 17th of August by the LIGO/Virgo detectors. While only the gravitational wave signal emitted during the inspiral of the two neutron stars has been detected, the detection of electromagnetic counterparts, in particular of the kilonova and gamma ray burst, suggest a complicated evolution of the merger remnant with a possible hypermassive or supramassive neutron star phase and black hole formation as shown in the animation.

(continues... to see more of this description text, click text at top of video then under the video box click the "show more" at the end of the caption excerpt)
 
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Ophiolite

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Astronomers report a possible slew of extragalactic exoplanets
Quite remarkable if it is confirmed. Read more here.

Discoveries of exoplanets in our galaxy exceed 3,700 to date, but if that’s not enough for you, astronomers are now probing outside of the Milky Way to find exoplanets in other galaxies. A group of researchers at the University of Oklahoma has just announced the discovery of a large population of free-floating planets in a galaxy 3.8 billion light-years away. Their results were published February 2 in the Astrophysical Journal Letters.

From Astronomy.com
 
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Halbhh

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Astronomers report a possible slew of extragalactic exoplanets
Quite remarkable if it is confirmed. Read more here.

Discoveries of exoplanets in our galaxy exceed 3,700 to date, but if that’s not enough for you, astronomers are now probing outside of the Milky Way to find exoplanets in other galaxies. A group of researchers at the University of Oklahoma has just announced the discovery of a large population of free-floating planets in a galaxy 3.8 billion light-years away. Their results were published February 2 in the Astrophysical Journal Letters.

From Astronomy.com

Interesting to see that order of magnitude guesstimate of 2000/per star. Also the image of RX J1131-1231 was spectacular. Really something. Lemme see if I can post that image.

rxj1131.jpg

RX J1131-1231 is about 6 billion light-years away. It is a lensed quasar; gravitational lensing caused by an intervening elliptical galaxy (center, yellow) has magnified and multiplied the image of RX J1131 into four images (pink) as seen with the Chandra X-ray Observatory.
X-ray: NASA/CXC/Univ of Michigan/R.C.Reis et al; Optical: NASA/STScI
from Astronomers report a possible slew of extragalactic exoplanets
(as from Ophiolite's link just above)
 
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Willis Gravning

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About 20 years ago I took an interest in astronomy when the Hale-Bopp comet lit up the night sky. At the time I lived on an acreage far from city lights and enjoyed a beautiful dark night sky. I liked to make things so I built an 8 inch F8 Newtonian telescope from scratch, grinding and polishing the main objective mirror from a Pyrex blank and designing a Dobsonian mount from large surplus bearings. I especially enjoyed finding other galaxies with it, although with the naked eye they are only dim smudges and not at all like the wonderful color photos we see from observatories and the Hubble ST. I remember one particular night looking for and finding the Triangulum Galaxy. It took some time to find but finally there it was, very dim but huge...it filled up the field of view of the scope. It was awesome.

Now I live in the city so star gazing is only a rare treat.

M33_-_Triangulum_Galaxy.jpg
 
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USincognito

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We had a clear night last night so I got to do some observing. I was too lazy to get the scope out so just used the binos. How long have you folks been amateur astronomers? 22 years for me?

I've been doing naked eye astronomy for 30 years since I first watched Jack Horkheimer: Star Hustler. Actually got a chance to get a photo with him in 2003.
MeHorkheimer.JPG
 
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Halbhh

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Willis Gravning

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Halbhh

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Michael

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Is this typical? Old Red Dwarf star not so stable...by a lot!:
https://phys.org/news/2018-02-proxima-centauri-good-bad-day.html

People have wanted to imagine these red dwarfs, 85% of all stars, might be hospitable for life.

I would say from the article that it was not typical for this particular star:

"March 24, 2017 was no ordinary day for Proxima Cen," said lead author MacGregor.

Whether it's typical for all red dwarfs to produce such massive events remains to be seen. I doubt that we have enough long term data to make that kind of call, but but my "guess" is that it's an unusual event in general in terms of the magnitude.

Keep in mind that most flares are pretty directional in terms of the slower solar wind, so it's unlikely that this flare resulted on a direct solar wind hit on every planet in the solar system. On the other hand, the original "burst" of very high speed charged particles could have briefly overwhelmed the daylight side of the several planets on the flare side of the sun. Depending on the magnetosphere of the planets involved, some of that high speed particle radiation would have been funneled toward the poles of the planet and the planet's atmosphere likely absorbed a lot of the rest of that radiation.

In short, even such a massive event wouldn't necessarily wipe out all life on every planet in the solar system. A planet that happened to be located on the opposite side of the sun as the flare might have only seen a bit of an unusual light show.
 
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Halbhh

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I would say from the article that it was not typical for this particular star:



Whether it's typical for all red dwarfs to produce such massive events remains to be seen. I doubt that we have enough long term data to make that kind of call, but but my "guess" is that it's an unusual event in general in terms of the magnitude.

Keep in mind that most flares are pretty directional in terms of the slower solar wind, so it's unlikely that this flare resulted on a direct solar wind hit on every planet in the solar system. On the other hand, the original "burst" of very high speed charged particles could have briefly overwhelmed the daylight side of the several planets on the flare side of the sun. Depending on the magnetosphere of the planets involved, some of that high speed particle radiation would have been funneled toward the poles of the planet and the planet's atmosphere likely absorbed a lot of the rest of that radiation.

In short, even such a massive event wouldn't necessarily wipe out all life on every planet in the solar system. A planet that happened to be located on the opposite side of the sun as the flare might have only seen a bit of an unusual light show.

It was notable that only because of the new technique did they even see the flare. Meaning we don't know how often such flares happen, but even just if for instance once in 1,000 or 10,000 years, it's already too much I'm betting, because it's so powerful. That's why they suggest it would dessicate planets. Having plenty of atmosphere isn't enough and their magnetic fields aren't likely large since they are tidally locked. (that's all off the top of my head, but one should read up more on such questions to get more details).

----------
(note that when the authors say ""Over the billions of years since Proxima b formed, flares like this one could have evaporated any atmosphere or ocean and sterilized the surface, suggesting that habitability may involve more than just being the right distance from the host star to have liquid water." that's not just hand waving, but they are referring to the variety of results of the math and computation already done on this question by various groups in the last few years, also notably though without full knowledge but only an older guesstimation of the type and size of stellar flares, to which this new observation of course suggests....could be, like so much, a wrong estimation. It should be interesting to see new estimations of flare activity and size and frequency in the coming years for the red dwarf population! But even the more tame estimations already used suggests a lot of just-so requirements, such as a significant magnetic field (which we don't have cause to expect in a tidally locked planet I'm thinking))

also, just noticed this, but it's typical of other such articles I've seen:
https://phys.org/news/2016-12-simulations-life-planet-proxima-thick.html#nRlv
 
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Halbhh

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Remember people the popular notion little red stars -- Red Dwarfs, which are over 3/4th of all stars -- might be often enough hosting life? Hey, why not, right?

Ah, well...

Maybe...not so much.

Little red stars are more deadly it looks even than I suggested a while back. Consider the increase in flux noted well down in this article!

https://phys.org/news/2018-04-proxima-centauri-flare-powerful-visible.html

What if our own sun got 68x as bright for a while?...
 
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Shemjaza

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Remember people the popular notion little red stars -- Red Dwarfs, which are over 3/4th of all stars -- might be often enough hosting life? Hey, why not, right?

Ah, well...

Maybe...not so much.

Little red stars are more deadly it looks even than I suggested a while back. Consider the increase in flux noted well down in this article!

https://phys.org/news/2018-04-proxima-centauri-flare-powerful-visible.html

What if our own sun got 68x as bright for a while?...
Not great for life developing there, but possible a good place for an advanced species to set up shop for the long haul. Those things can theoretically last a trillion years.

There are still a large number of orange stars slightly smaller then Sol who will last quite a while and might have more sensible planetary orbits and behaviors.
 
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Halbhh

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Not great for life developing there, but possible a good place for an advanced species to set up shop for the long haul. Those things can theoretically last a trillion years.

There are still a large number of orange stars slightly smaller then Sol who will last quite a while and might have more sensible planetary orbits and behaviors.

Yes, in our imaginations. I say that from reading many thousands of astronomy articles. For instance, this was interesting yesterday:
https://phys.org/news/2018-04-amazingly-wide-variety-disks.html
You'll want to see these interesting images on a larger screen, or at least clicking on them if using a phone.
Planetary systems are rather more highly individual than we used to think. Also, the planets tend to migrate unless they can get an unusual stable configuration. To be protected from bombardment for instance it helps a smaller rocky planet like Earth (a planet able to have both land and water and pleasant and very useful margins between the two) to have a gas giant to help protect it against too much asteroid bombardment. But a gas giant will cause a small planet to migrate. Why doesn't Earth? Because we have an unusual combination of 4 gas giants of favorable mass ratios and orbits. A variety of stars in addition to red dwarfs are non-quiet, and even a sun sized star isn't necessarily quiet. Ergo, conditions favorable to the evolution of life (as compared to a brief existence then extinction) as we know it is likely to be rather a lot more rare than people imagine in popular science articles in the last many years. Often when you read in popular science articles you are reading a combination of a bit of observation and a lot of extra added imagination. Another new factor I just noticed the other day is that it helps if one hopes to have both water and land and margins to have only a little water, but not much, and then you have to have the magnetic field that is adequate to protect that water from solar flux dissociation over time, so here we have a combo of a nicely strong magnetic field, a quiet star, a nice distance, just the right amount of water and plate tectonics, a helpful moon of a nice size, a very nice combination of gas giants. Rather a nice locale. I didn't make an exhaustive list there, but these are the most key things off the top of my head.
 
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FrumiousBandersnatch

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Remember people the popular notion little red stars -- Red Dwarfs, which are over 3/4th of all stars -- might be often enough hosting life? Hey, why not, right?

Ah, well...

Maybe...not so much.

Little red stars are more deadly it looks even than I suggested a while back. Consider the increase in flux noted well down in this article!

https://phys.org/news/2018-04-proxima-centauri-flare-powerful-visible.html

What if our own sun got 68x as bright for a while?...
On the plus side, they say that a third of red dwarfs do not actively flare:

"However, even if two-thirds of these stars are active, that still leaves us with billions of possibilities."
 
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Halbhh

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On the plus side, they say that a third of red dwarfs do not actively flare:

"However, even if two-thirds of these stars are active, that still leaves us with billions of possibilities."
That was actually a hand-waving hypothetical sentence. Notably hopeful. We want to instead be clear-eyed of course. It's useful to be aware that only recently do we have instruments that are good at observing variability (for instance Kepler is an example). The instruments needs to be outside the atmosphere ideally (to notice smaller but still important variation), and also needs to stare at the same star(s) a significant time. It's useful to be aware it's easy to find articles only laying out an older theory with some older observations that have been superseded. In the past, "variable" meant large variation, that is quite dramatic, like for example Cepheid. But we want to know more than only that there are extremely variable stars. We want to know instead what about typical stars that don't have dramatic variation, as to whether they are highly stable like our sun, or have still significant variation or too much flaring, etc.

Ah, here's a recent article that both accessible and informative:
Kepler space telescope discovers variability in the Seven Sisters – Astronomy Now
 
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