Arniepie From Belgium, joined Aug 2005, 1265 posts, RR: 1 Posted (4 years 1 week 2 days 17 hours ago) and read 5186 times:
At 600 lightyears away from earth , the supergiant star Betelgeuze ( left top star in ORION constellation) is on the brink of becoming a supernova and will be the second brightest object on the sky, after our own sun.
Shrinking about 15% in 15 years time it might already have exploded by now, whe're up for a great show, hopefully I'll see it in my lifetime.
Vivekman2006 From India, joined May 2006, 517 posts, RR: 3 Reply 1, posted (4 years 1 week 2 days 17 hours ago) and read 5175 times:
The article says:
Quote: Yes, it's totally possible Betelgeuse could explode, but the chances of this happening in this 600 year window is highly unlikely, regardless how fast it seems to be shrinking.
So is there a chance of we getting to see any visual effects in our life time?
Also, how bright does a supernova appear? If you are saying that it would be the second brightest object in the sky after the sun, will it be brighter than the moon? By how much?
Prebennorholm From Denmark, joined Mar 2000, 6039 posts, RR: 55 Reply 2, posted (4 years 1 week 1 day 2 hours ago) and read 4863 times:
Betelguese has always been somewhat unstable. It was first described as a highly variable star by Sir John Herchel back in 1836. It may have exploded as a type II supernova 599 years ago, or it may happen in a million years time. We cannot know.
When it happens it will for a month or two give a visible light comparable to the full Moon.
But for many years Betelguese has varied its size and luminosity. Diameter is believed to vary between roughly 180 million and 280 million miles. Its mass is some 20 times the Sun, but volume is several hundred million times the Sun since diameter is comparable to the orbit of Mars. Luminosity has during the last couple of hundred years varied between mag 0.2 and 1.2 - or roughly by a factor 2.5.
For sure it has been shrinking during the last couple of decades. But it has been shrinking and expanding many thousand times since it became a red gigant star. And sure a type II supernova begins with the star imploding. But the chance for us to see that is very small.
The axis of rotation of Betelguese has recently been found. Since it is far from pointing our way, then there should be no risk of a serious gamma ray burst which otherwise might threaten our ecosystem.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
BritJap From Japan, joined Aug 2006, 250 posts, RR: 2 Reply 4, posted (4 years 1 week 22 hours ago) and read 4813 times:
Quoting Nomadd22 (Reply 3): Quoting Prebennorholm (Reply 2):
but volume is several hundred million times the Sun since diameter is comparable to the orbit of Mars
Diameter of 180 million miles would give it about 8 million times the sun's volume.
Don't ask me how accurate it is but it does give a nice impression.....
(Betelguese appears towards the end!!)
SpeedyGonzales From Norway, joined Sep 2007, 679 posts, RR: 0 Reply 5, posted (4 years 1 week 18 hours ago) and read 4779 times:
The outer envelopes of giant stars can be described as a "hot vacuum", as it has extremely low density. Using 20 M☉ as mass and 950 R☉ as radius (http://en.wikipedia.org/wiki/Betelguese) the average density of Betelguese is only ~33mg/m^3, or about 36000 times lower than air at sea level (1,2 kg/m^3). The outer parts will be significantly less dense than the average.
KC135TopBoom From United States of America, joined Jan 2005, 11742 posts, RR: 51 Reply 6, posted (4 years 6 days 11 hours ago) and read 4635 times:
Quoting Prebennorholm (Reply 2): The axis of rotation of Betelguese has recently been found. Since it is far from pointing our way, then there should be no risk of a serious gamma ray burst which otherwise might threaten our ecosystem.
Are we sure about that? Are we sure a gamma ray burst will only shoot out along the axis? But, you are right, a gamma ray burst would be a very bad thing for Earth.
Nomadd22 From United States of America, joined Feb 2008, 1577 posts, RR: 0 Reply 8, posted (4 years 5 days 16 hours ago) and read 4536 times:
Quoting SpeedyGonzales (Reply 5): The outer envelopes of giant stars can be described as a "hot vacuum", as it has extremely low density. Using 20 M☉ as mass and 950 R☉ as radius (http://en.wikipedia.org/wiki/Betelguese) the average density of Betelguese is only ~33mg/m^3, or about 36000 times lower than air at sea level (1,2 kg/m^3). The outer parts will be significantly less dense than the average.
That's why I doubt if the giants really look anything like the artists concepts. As diffuse as the outer parts are there's no way they could have the nice smooth, well defined surface as a smaller star. They probably look more like big fuzzy gas clouds.
Quoting KC135TopBoom (Reply 6): Are we sure about that? Are we sure a gamma ray burst will only shoot out along the axis? But, you are right, a gamma ray burst would be a very bad thing for Earth.
I think the idea is that that the gamma ray burst comes with the final stage of collapse when the neutron star or black hole is formed and the core's spin accelerates so fast it creates a ludicrous strength magnetic field that funnels the burst along the poles.
The jet is pretty narrow, which is why out of hundreds of millions of collapses in the observable universe every year, we only detect bursts from a few hundred.
Prebennorholm From Denmark, joined Mar 2000, 6039 posts, RR: 55 Reply 9, posted (4 years 5 days 2 hours ago) and read 4421 times:
Quoting KC135TopBoom (Reply 6): Are we sure a gamma ray burst will only shoot out along the axis? But, you are right, a gamma ray burst would be a very bad thing for Earth.
That's what the scientists tell us. They also tell us that the axis point 20 degrees aways from Earth, so the gamma ray burst will miss Earth by almost a couple of hundred comfortable lightyears.
But there is nothing unusual in red gigant stars like Betelguese ballooning in and out. Spectral analizes of many stars has told us that for a long time. The only unusual thing is that with Betelguese being so close to us it has now been proven visually.
Betelguese may easily last another million years or more. But compared to the Sun it is of course extremely shortlived. It has spent less than eight million years as a main sequence star while the Sun will outdo that by a factor 1,000 to 1,500.
It may have suffered a type II supernova 600 years ago, we cannot know. But the chance that present generations of homo sapient on planet Earth will live to see that is probably like one in 10,000 to one in 100,000. I wouldn't bet any money on that.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
Osiris30 From Barbados, joined Sep 2006, 3182 posts, RR: 25 Reply 13, posted (4 years 4 days ago) and read 4260 times:
Just a question, but if the star was undergoing gravitational collapse (i.e. starting to go supernova), wouldn't the rate of contraction be exponential in nature?
I don't care what you think of my opinion. It's my opinion, so have a nice day :)
Nomadd22 From United States of America, joined Feb 2008, 1577 posts, RR: 0 Reply 14, posted (4 years 3 days 16 hours ago) and read 4193 times:
Quoting Osiris30 (Reply 13): Just a question, but if the star was undergoing gravitational collapse (i.e. starting to go supernova), wouldn't the rate of contraction be exponential in nature?
Yep. The outer layers start falling inward and the closer to the core they get the stronger the gravitational field, so the acceleration accelerates. The rate as measured from the outside slows down when it approaches lightspeed, but the mass of the particles increase, so it comes out to the same thing momentum wise.
This type supernova happens when the momentum plus the gravity is enough to overcome the electron pressure and push them into the nuclei changing protons to neutrons and creating a neutron star. If there's enough mass to overcome the bounce you get from that and overcome the forces that keep neutrons distinct, they collapse and you get a black hole.
Much more complicated than that, of course. The interactions in that last few milliseconds of collapse are so complicated the best models and supercomputers are just beginning to get a handle on them.
Osiris30 From Barbados, joined Sep 2006, 3182 posts, RR: 25 Reply 16, posted (4 years 3 days 14 hours ago) and read 4166 times:
Quoting Nomadd22 (Reply 14):
Yep. The outer layers start falling inward and the closer to the core they get the stronger the gravitational field, so the acceleration accelerates. The rate as measured from the outside slows down when it approaches lightspeed, but the mass of the particles increase, so it comes out to the same thing momentum wise.
Thank you, nice to see some thing in physics still behave as logical deduction would have you think
So the question is, does the shrinking of this star conform to that pattern or not. Seems to me like it would be fairly straight forward to have some inkling if it's just a contraction or if it's actually the start of a supernova. (**straight forward in this sense means, if you can measure that it has shrunk, you can measure how fast it is shrinking, and with the two presto.. I'm not trying to imply measuring something 600 light years away is trivial).
I don't care what you think of my opinion. It's my opinion, so have a nice day :)
Nomadd22 From United States of America, joined Feb 2008, 1577 posts, RR: 0 Reply 17, posted (4 years 3 days 11 hours ago) and read 4137 times:
Quoting Osiris30 (Reply 16): So the question is, does the shrinking of this star conform to that pattern or not. Seems to me like it would be fairly straight forward to have some inkling if it's just a contraction or if it's actually the start of a supernova. (**straight forward in this sense means, if you can measure that it has shrunk, you can measure how fast it is shrinking, and with the two presto.. I'm not trying to imply measuring something 600 light years away is trivial).
They can tell when the star is in it's final stages by detecting the spectrum you'd see from iron making reactions, but predicting the normal cycles of expansion and contraction of stars is still a baby science.
The normal expanding and contractiong caused by varying nuclear activity goes on over years or thousands of years. Our sun does it a little bit. The collapse leading to the supernova happens almost instantly. The core hasn't been active for a long time and when the heavy element fusion in the farther out layers goes below a certain point, it stops completely in a few seconds leading to the collapse. The outer most layers can't fall in that fast, being several light minutes from the core, so you wouldn't actually see the collapse from a disance like in a Star Trek episode.
In a Betelgeuse type supernova, it's the jam up of the material trying to reach the core that causes the explosion. The rebound is intense enough to create all the heavier than iron elements that you can't make with steady state fusion.
Any radiation you can detect from the falling matter could have it's speed measured by doppler shift, but unless you can analyze it in five seconds or so, the star exploding would probably be a hint it's not a normal contraction.
Springbok747 From Australia, joined Nov 2004, 4387 posts, RR: 13 Reply 19, posted (4 years 3 days 6 hours ago) and read 4070 times:
It would be cool to see one, though it looks like it won't be visible in our lifetime. On a related note..anyone know about the 'Pillars of Creation' in the Eagle Nebula? I'm talking about this one:
Apparently it no longer exists as it has been toppled by a stellar blast some 6000 years ago, but it is still visible to us and will remain visible for another 1000 years as it is some 7000 light years away..so the aftermath of the blast will only be visible to us after a 1000 years. Interesting stuff.
EA772LR From United States of America, joined Mar 2007, 2836 posts, RR: 10 Reply 20, posted (4 years 3 days 6 hours ago) and read 4059 times:
Some really great and informative posts! I have to admit I am a total novice when it comes to astronomy, and pardon my ignorance, but what causes a star to collapse within itself?
We often judge others by their actions, but ourselves by our intentions.
Phoenix9 From Canada, joined Aug 2007, 2546 posts, RR: 8 Reply 21, posted (4 years 3 days 6 hours ago) and read 4056 times:
Quoting Springbok747 (Reply 19): Apparently it no longer exists as it has been toppled by a stellar blast some 6000 years ago, but it is still visible to us and will remain visible for another 1000 years as it is some 7000 light years away..so the aftermath of the blast will only be visible to us after a 1000 years. Interesting stuff.
Amazing isn't it. Something that we say is a million light years away....was there million years ago....so basically in a sense, we are looking into past. So who knows what stage Betelgeuse is at this point!
Life only makes sense when you look at it backwards.
Phoenix9 From Canada, joined Aug 2007, 2546 posts, RR: 8 Reply 22, posted (4 years 3 days 6 hours ago) and read 4039 times:
Quoting EA772LR (Reply 20): what causes a star to collapse within itself?
It happens towards the end of a large star's lifecycle when the fuel is burned off. The high gravity of a very large star causes the material to collapse towards the core...the core pushes back due to the neutron denisty. Things at this point basically go apesht and the star ends up exploding.
EA772LR From United States of America, joined Mar 2007, 2836 posts, RR: 10 Reply 23, posted (4 years 3 days 6 hours ago) and read 4033 times:
Quoting Phoenix9 (Reply 22): It happens towards the end of a large star's lifecycle when the fuel is burned off. The high gravity of a very large star causes the material to collapse towards the core...the core pushes back due to the neutron denisty. Things at this point basically go apesht and the star ends up exploding.
This would be a good place to start:
Thank you
Yeah as soon as I made my post, I realized I was staring at the largest encyclopedia in the world *cough* the internet, and was just being lazy! But thank you also for the link.
We often judge others by their actions, but ourselves by our intentions.
AirCatalonia From Spain, joined Nov 2007, 532 posts, RR: 0 Reply 24, posted (4 years 3 days 3 hours ago) and read 3982 times:
That would be awesome!
An impressive show, for sure. And the ultimate reminder that we are nothing, dust in the space wind, even in a time of internet and all sorts of technological advances.
25 Phoenix9: Just to put that into perspective: and that is just our backyard![Edited 2009-06-17 17:48:33]
26 EA772LR: I was reading that some astrophysicist theorize that matter (stars, nebulae, galaxies, etc) that were created quickly after the supposed Big Bang out
27 Tugger: I don't see anything in your post. Am I missing something or is it supposed to be representing the vast nothingness of space? Tugg
28 Phoenix9: Something is fishy here though....nothing can move faster than speed of light (well at least as far as we know), the expansion rate 'approaches' towa
29 Phoenix9: There is a picture that should be showing. I can see it on my computer. You can check it out here: http://binarri.edu.au/moodle/file.ph.../2/milkyway
30 EA772LR: Right. According to Einstein, and he's been right thus far, the closer we get to the speed of light, the more mass we begin to gain, therefore more e
31 DocLightning: Now, imagine flying all that distance on FR.
33 Tugger: If I understand what the astrophysicist and theoretical physicist were getting at, it is the COMBINED speeds of the two objects that bring us to a se
34 EA772LR: Yes thank you Tugger. That is what I want to say, but couldn't formulate my words to explain.
35 Phoenix9: Ah...we're talking about relative speeds...sorry I misunderstood. I was talking about considering one as a stationary point and then 'observing' from
36 NoWorries: Under special relativity, the rule for combining speeds is (a + b) / (1 + (a/c)( b/c)) where a and b are the two objects moving along a line relative
37 Prebennorholm: My old car just passed 300,000 miles today (480,000 km). When I put it on Ebay, then I think that I will write "One owner and 1.6 light seconds". It l
38 TheCol: There have been a number of supernovas that have been documented by ancient China and other cultures. The most significant event was in 1054 A.D. htt
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I have to admit I am a total novice when it comes to astronomy, and pardon my ignorance, but what causes a star to collapse within itself?
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