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Mysterious Stars Surround Andromeda's Black Hole
UltimaGuy writes to tell us that Yahoo is running a story about a recent discovery that shows the source of strange blue light coming from the center of the Andromeda galaxy. The light is actually a cluster of stars circling the galaxy's central black hole with immense orbital velocity. From the article: "Such frenetic activity was thought to prevent star formation. Stars form when a knot of gas and dust collapses under its own gravity."
Elements past iron can only be created in a supernova explosion. Google on "supernova elements" for more information. Of course, the element synthesis during a supernova explosion is due to fusion, but I'm not sure one could call it "star fusion".
Ben Hocking
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Wouldnt matter too much...our Milky Way and Andromeda are on a slow collision course anyway - by the time an ejected star got here, the rest of the galaxy would be right behind it. But no need to go hide in a cave just yet, we've still got about 3 billion years.
HA! Dude, no it's not. If we were close enough to a black hole to send a probe into it, we'd also be close enough to have the entire Earth sucked in and squeezed down to a grain of sand... or you know, whaver actually happens when you get sucked into a black hole.
According to Here Our sun will still be burning brightly.
:)
According to the article, it should happen in about 3 billion years
On a side note---considering the lifespan of planets, galaxies, universis - it is kind of depressing we won't be around to see spectacular things (i.e. Star Trek space travel). Ah I need to find me a "Q" and get them to let me join up
I mod down so you can mod up. Your welcome.
The sun won't go nova in any case; it's too small.
Andromeda is the closest major galaxy to the Milky Way, a mere ~2 million light years away. It's moving toward us rather rapidly though, and the two galaxies should collide in about 3 billion years; if one of these stars was "thrown free" (how exactly?) it might get here well before that, but your basic point is right on: By the time it got here, there is basically no chance that the earth will still be a habitable planet.
Of course, the chance of an object randomly thrown from that far away hitting the earth is like... Let's see, if I randomly threw a dart (really hard), the chances of hitting the bullseye of a dartboard on the planet neptune... are much much better.
We get a slow expansion to red giant, then it peters out to a dwarf. I think we at least get a planetary nebula in the deal.
There are several methods for the creation of elements including the r-process (supernovae), the s-process (red giants), the cosmic ray interaction, and the big bang. See this thread for more information:
http://www.bautforum.com/showthread.php?p=249157
and wikipedia:
http://en.wikipedia.org/wiki/Nucleosynthesis
Obi-Wan Kenobi: "That eye is our last hope"
Yoda: "No, there is another."
In the end they will lay their freedom at our feet and say to us, Make us your slaves, but feed us. - Fyodor Dostoyevsky
You can read the abstract; if you have an institutional subscription to Astrophys.J., you can also view the full text.
An artist's rendition on their picture of the day:
_ feature_411.html
http://www.nasa.gov/multimedia/imagegallery/image
--
fu
That's quite possible. If they formed in a wider orbit around the black hole, for example, they could well have been caught by tidal drag and slowly moved into lower orbits.
The real question is how they can exist at all in such a low orbit (or, more accurately, how they can exist in such a strong gravity gradient). What happens is that if they tidal difference between the two sides of the star (the difference between the black hole's gravity at the closest edge of the star and that on the furthest edge) exceeds the star's escape velocity, matter will be able to leave the star and it just falls apart. The implication (which the Yahoo! article was too low-tech to get right) was that the stars must be very dense. A dense star will have both (a) less distance between that nearest and furthest edge and (b) a steeper gravity well for material to get out of in the first place.
The other interesting bit is the rather close estimate of the black hole's mass. Most of the other estimates of galactic center black hole masses I've seen are based on things orbiting them far more distantly, such as 10-100 light years.
Have you ever wondered How to Take Over
While it's true that you lose energy when you fuse to stuff heavier than iron, that doesn't mean that it never happens. In a supernova, for instance, there is a short time when there's energy to burn (pardon the pun) and heavy stuff like lead and uranium etc. can form. That's why you see that the solar system is made up of mostly hydrogen and helium (stuff not yet fused), several percent the stuff heavier than helium but lighter than iron, and only a tiny fraction of a percent of the stuff heavier than iron. The heavy stuff almost never gets a chance to form.
Have you ever wondered How to Take Over
The initial gas mix of stars is approximately 95% Hydrogen (H) and about 5% Helium (He), with a very tiny fraction of Lithium and heavier elements. Anything heavier than Helium is considered a "metal" to an astronomer, BTW.
Stars produce the most energy by fusing H into He, and they can also gain some energy by fusing heavier elements, but the amount of energy declines until you reach Iron (Fe), after which fusion no longer results in an energy gain. Once a star starts having a lot of Fe in its core, the fusion synthesis process stops producing the energy needed to keep the star going, so it collapses, and the rebound shock causes a nova, also producing elements heavier than Iron as a result.
The approximate distribution of elements in Sol, our sun, today is:
{'H':.785, 'He':.197, 'O':.0097, 'C':.004, 'N':.001, 'Si':.001, 'Mg':.00076, 'Ne':.00058, 'Fe':.00014, 'S':.0004}
Planets like Earth have a much higher distribution of heavier elements than stars do, for a very simple reason: they aren't big enough to have enough gravity to keep things like H and He from escaping over time, unless the planet is above a critical mass, in which case it forms a gas giant like Jupiter, Saturn, etc, which are big enough to retain such very light gasses.
Here's a table of the planets in our solar system, with mass measured in 10**24 kg, density relative to water, then the heaviest molecular weight of a gas the planet will retain, and the lightest common atmospheric gas which is kept:
Mercury mass: 0.33 density: 5.43 moleculelim: 43.5 gas: CarbonDioxide
Venus mass: 4.87 density: 5.24 moleculelim: 7.3 gas: Methane
Earth mass: 5.97 density: 5.51 moleculelim: 6.3 gas: Methane
Mars mass: 0.64 density: 3.93 moleculelim: 31.1 gas: OxygenGas
Jupiter mass: 1899.00 density: 1.33 moleculelim: 0.2 gas: HydrogenGas
Saturn mass: 568.00 density: 0.69 moleculelim: 0.6 gas: HydrogenGas
Uranus mass: 86.80 density: 1.27 moleculelim: 1.7 gas: HydrogenGas
Neptune mass: 102.00 density: 1.64 moleculelim: 1.4 gas: HydrogenGas
Pluto mass: 0.01 density: 1.75 moleculelim: 578.5 gas: None
In particular, oxygen gas, O2, has a molecular weight of 32, and N2 is 28. If Mars were just a little bit heavier, it would have a much more substantial atmosphere which would be much more similar to that here on Earth.
-Chuck
PS: Why yes, that's a Python dictionary above, you didn't think I'd write the table above by hand or post using "Code" frivolously, do you...? :-)
"The human race's favorite method for being in control of the facts is to ignore them." -Celia Green