Three Enormous Stars Found

[livius drusus]

3 Giant Stars May Point the Way to Our Sun's Destiny (http://www.nytimes.com/2005/01/11/science/space/11star.html) (NYT, may require registration or bugmenot).

Each of the three stars is more than a billion miles wide, filling as much space as 3.4 billion Suns. Placed at the center of the solar system, one of these stars would extend to halfway between Jupiter and Saturn. The stars are more than twice as wide as Betelgeuse in the constellation Orion, a red supergiant familiar to amateur astronomers.

"We actually know, both observationally and theoretically, how big a star can get," said Dr. Philip Massey of the Lowell Observatory in Flagstaff, Ariz., who led an international team of astronomers that conducted the research. "These are right at the limit of what solar evolutionary theory says we should get by the way of red supergiants."

[...]

While KW Sagitarii, KY Cygni and V354 Cephei are most likely the largest possible stars in the Milky Way, Dr. Massey said, they may not be the largest in the universe. Stellar models, he said, predict that even larger stars could evolve in galaxies with lower concentrations of elements heavier than helium, like the nearby Magellanic Clouds.

I didn't even know the field was called solar evolutionary theory, but of course it makes sense that it would be. Anyway, I thought it was a really cool discovery, particularly thinking about what kinds of planets (if any) would revolve around such giants, a la SkepticJ's Bowl World (http://www.freethought-forum.com/forum/showthread.php?t=837) discussion.

[wade-w]

Stellar Evolution is the name given to the theory of how stars age. Exactly how a star ages depends on it's mass, though the red giant (or super giant) stage is one all but the very smallest stars experience in their old age. What happens - this is extremely simplified - is that when all of the hydrogen in the star's core is exhausted, the core collapses which increases the pressure there. This higher pressure in the core causes the helium that is the byproduct of the former hydrogen reaction to begin it's own fusion.

Since helium fuses at a much higher temprature, this excess heat causes the star to reach a new equilibrium, and the outer layers begin to expand. The result of this exapnsion is a red giant or super giant depending on it's original mass. When our own sun reaches this stage, earth will be consumed in a fiery death by the expansion. IIRC, it's estimated that the sun will expand to somewhere around the asteroid belt.

[Dragar]

Cool findings!

I have an exam on stellar structure (which includes sections on stellar evolution) next Thursday. :yup:

[viscousmemories]

When our own sun reaches this stage, earth will be consumed in a fiery death by the expansion.
And not a moment too soon!

Astronomical sizes are so completely unfathomable to me. I mean, I've driven cross-country and flown over the ocean, so I can visualize thousands of miles. But when I try to visualize something a billion miles wide... :eek:

[Ymir's blood]

Three Enormous Stars Found
Ok, Elvis has to be one but who are the other two?

[viscousmemories]

:chuckle:

Dammit. I can't think of anymore.

[Skep]

Three Enormous Stars Found
Ok, Elvis has to be one but who are the other two?
Orson Welles and William Conrad.

[livius drusus]

Three enormous doofuses found. In this thread.

[viscousmemories]

:roflmao:







Wait a minute!

[Dingfod]

John Candy and Chris Farley!

[viscousmemories]

Yeah see, I thought of them too. But like Orson Welles and William Conrad, they're not missing! Elvis is the only one I can think of that needs to be 'found'.

[Dingfod]

I thought it might be based on girth, given the size of the stars mentioned.

[Ymir's blood]

I was really just thinking of missing stars. Originally I had wanted to mention Buddy Holly and Foxglove, but that was just an in-joke. The Elvis thing meant reaching a larger demographic.

[Shake]

I was going to say John Goodman and Kirstie Alley! :P :D

Seriously though, I'd always heard that while our sun will eventually blow up to engulf the Earth, it would then shrink back down to become a small white dwarf. Something I read yesterday said that our sun doesn't have enough mass to ever get as big as those three are now.

[wade-w]

Seriously though, I'd always heard that while our sun will eventually blow up to engulf the Earth, it would then shrink back down to become a small white dwarf. Something I read yesterday said that our sun doesn't have enough mass to ever get as big as those three are now.

That's right. As I said before, IIRC it's estimated our sun will eventually be somewhere between the current orbit of Mars and that of Jupiter.

For stars that have a solar mass of about 1.5 and less, after the red giant phase (when the helium fuel is exhausted) the star collapses into a white dwarf, about the size of earth. It continues to shine for a few billion years, due to thermal radiation, but there is no further fusion reaction.

For stars that have a solar mass of more than 1.5, the collapse - new fusion reaction - further expansion begins anew, and we get a carbon -> oxygen reaction. This cycle repeats until we get all the way up to iron, which cannot fuse in this manner. Once this happens, the star collapses for a final time, resulting in a supernova. For stars with between 1.5 and 3 solar masses, what's left after the supernova is a neutron star, or pulsar. If the star's mass is greater than this, we wind up with a black hole.

[Brimshack]

"We actually know, both observationally and theoretically, how big a star can get," said Dr. Philip Massey of the Lowell Observatory in Flagstaff, Ariz., who led an international team of astronomers that conducted the research. "These are right at the limit of what solar evolutionary theory says we should get by the way of red supergiants."

Yeah that's right baby! Don't even try to pretend you people not jealous. All your solar evolutionary theory are belong to us!!!!

[godfry n. glad]

I thought it might be based on girth, given the size of the stars mentioned.

Well... My mind went right to Luciano Pavarotti, Placido Domingo, and that other tenor...whatshisname.

godfry

[Ensign Steve]

All your solar evolutionary theory are belong to us!!!!

Oh my god, AYB?! That is so last millenium.

(I still shot beer out my nose, tho. tee hee!)

Congrats on the big telescope thing, or whatever. Seriously! That's cool.

[wade-w]

/me sighs.

I guess I should know better by now.

Note to self: Don't bother with serious posts around here anymore.

[Ymir's blood]

* wade-w sighs.

I guess I should know better by now.

Note to self: Don't bother with serious posts around here anymore.
Sorry, man. Didn't mean to derail the thread. :(

[Brimshack]

All your solar evolutionary theory are belong to us!!!!

Oh my god, AYB?! That is so last millenium.

(I still shot beer out my nose, tho. tee hee!)

Congrats on the big telescope thing, or whatever. Seriously! That's cool.

Making beer come out a hot chicks nose. It's what I live for!


:yup:


Sorry Wade,

[JoeP]

Returning to stellar evolution:

There's plenty of focus on the masses of the stars; I recall reading that these stars have masses more than 150 times that of the sun. But being a million(?) times larger, they must be enormously less dense. Presumably in moving from a regular star (main sequence? Dredging my memory here although I could go and look it up) to a giant they don't miraculously gain mass.

What is the range of densities in stars?

[livius drusus]

Well, I'm pretty sure I'm not alone in appreciating your elucidations of the topic, wade. Thank you. :thankee:

(And thanks for the info on shrimp farming, xoup and Darren. It makes sense, but it just sounded so odd to me.)

[godfry n. glad]

I blame Brimshack and his new toupee.

godfry

[Dragar]

Returning to stellar evolution:

There's plenty of focus on the masses of the stars; I recall reading that these stars have masses more than 150 times that of the sun. But being a million(?) times larger, they must be enormously less dense. Presumably in moving from a regular star (main sequence? Dredging my memory here although I could go and look it up) to a giant they don't miraculously gain mass.

What is the range of densities in stars?

That's odd. I've read that for fusion reaction type stars (i.e. not black holes and neutron stars) there isn't that much range in the mass. They go from about a tenth of the mass of the sun to a few tens times the mass of the sun. Have you got a link to where their masses are quoted? 150 times is more massive than I thought!

[JoeP]

I didn't have it quite right: "they're only 25 times the mass of the Sun (stars have been discovered which have 150 times the mass of the Sun)" (http://www.universetoday.com/am/publish/three_largest_stars.html)

Howeger, "All three are 1,500 times bigger than our own Sun". I assume this means in radius, hence 3,000,000,000 times greater in volume and 100,000,000 times less in density.

[Dragar]

Interesting. I didn't realise they got that big.

I think you dropped a zero or two on the density. Though I imagine it varies quite considerably through the star.

[wade-w]

Wow, I didn't realize that stars could be that massive either. One intersting thing about very massive stars: the larger the mass of the star, the shorter it's overall life.

[JoeP]

Interesting. I didn't realise they got that big.

I think you dropped a zero or two on the density. Though I imagine it varies quite considerably through the star.
The zeroes are right ... 3,000,000,000 divided by 30 = 100,000,000. More accurately, another page said "3.4 billion times" the volume of the sun. Divide that by 25: 136,000,000.

I still want to research this later today...

[Dragar]

Oh, yes, my mistake.