- #491
SchrodingersCat
- 12
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Eratosthenes observing the noontime Sun.
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Astronomy Trivia Challenge: Can You Answer These Questions About the Night Sky?
In summary, this conversation is about an astronomy Q&A game where players take turns asking and answering questions. The rules are that a question must be answered correctly within 3 days or a new question is posted. If the person who posted the question does not respond within 2-3 days, the first person to answer correctly can then post their own question. The first question asked is about the brightest star in the Northern Sky, with the correct answer being Sirius. The game then continues with questions about other astronomical topics such as supermassive black holes, energy generation in stars, and the length of Pluto's orbit. The conversation also includes some discussion about the rules and format of the game, as well as some jokes and personal anecdotes from the
- #492
SchrodingersCat
- 12
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Sorry, that was for measuring the circumferance. I believe it was Aristotle using Earth's shadow on the Moon during a lunar eclipse
- #493
schwarzchildradius
Naw you were right with the first one. your go/
- #494
schwarzchildradius
By the way, I've run across a passage from Cosmos where he names the hydrocarbon sludge
"Such experiments were first performed in the early 1950's by Stanley Miller, then a graduate student of the chemist Harold Urey. Urey had argued compellingly that the early atmosphere of the Earth was hydrogen-rich, as is most of the Cosmos; that the hydrogen has since trickled away to space from Earth, but not from massive Jupiter... After Urey suggested that such gasses be sparked, someone asked him wat he expected to make in such and experiment. Urey replied, "Beilstein." Beilstein is the massive German compendium in 28 volumes, listing all the organic molecules known to chemists."
So what is "Tholin?"
"Such experiments were first performed in the early 1950's by Stanley Miller, then a graduate student of the chemist Harold Urey. Urey had argued compellingly that the early atmosphere of the Earth was hydrogen-rich, as is most of the Cosmos; that the hydrogen has since trickled away to space from Earth, but not from massive Jupiter... After Urey suggested that such gasses be sparked, someone asked him wat he expected to make in such and experiment. Urey replied, "Beilstein." Beilstein is the massive German compendium in 28 volumes, listing all the organic molecules known to chemists."
So what is "Tholin?"
- #495
Phobos
Staff Emeritus
Science Advisor
Gold Member
- 1,957
- 7
schwarzchildradius said:
The hydrocarbon sludge on Saturn's moon Titan (discussed briefly in Sagan's sequel to "Cosmos" called "Pale Blue Dot")
- #496
SchrodingersCat
- 12
- 0
Sorry It took so long to post this. Anyhow, here is the question. What supports a Neutron Star from collapse? (Do not just name the type of support but also explain it)
- #497
Labguy
Science Advisor
- 731
- 7
It is called "neutron degeneracy pressure". Neutron degeneracy is actually at a "core", since a neutron star is not all neutrons from the surface down, they (the stars) actually have a structure. the "mass" is the gravitational mass and is distinct from the baryonic mass, because the gravitational redshift of a neutron star is so great, the gravitational mass is about 20% lower than the baryonic mass.SchrodingersCat said:
When the density towards the inner core exceeds the nuclear density of 2.8x10^14 g/cm^3 by a factor of 2 or 3, exotic stuff might be able to form, like pion condensates, lambda hyperons, delta isobars, and quark-gluon plasmas. To me, most likely quark-gluon plasmas. So it is essentially the strong nuclear force in the deep interior preventing further collapse.
The interesting structure can be seen at: http://www.lsw.uni-heidelberg.de/users/mcamenzi/NS_Mass.html
Beyond that (simple explanation) it gets a bit complicated, and several models all work to show one form or another of "condensate" to prevent collapse without additional mass being added.
- #498
SchrodingersCat
- 12
- 0
Well Labguy, it is your turn to ask a question. 
- #499
Labguy
Science Advisor
- 731
- 7
Hey, S-Cat. I'm going to have to pass and let you ask another because I'll be on a trip and "away from a computer" for several weeks.SchrodingersCat said:Well Labguy, it is your turn to ask a question.
Ask another Q or pass to the last guy, etc. I'll be back for more in a few weeks.
- #500
SchrodingersCat
- 12
- 0
In a cluster most stars have the same main sequince turn off point. However, there is another class of bluer stars that seem to be younger. The formation of these stars is uncertain but one of the theories is that they form when one star accretes matter from another star. Another possible formation scenario is the collision of one or more stars. If you look at the HR diagram for some clusters you will see the that most stars lay along the same main sequice and horizontal branch and whatnot but there is also often a separate main sequince and horizontal branch (containing much less stars) for these strange objects.
What is the name of these objects, who was the first to discovere them and which globular cluster were they first found in?
What is the name of these objects, who was the first to discovere them and which globular cluster were they first found in?
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- #501
SchrodingersCat
- 12
- 0
Need a hint?
The person who discovered these objects was one of the co-discoverers of the quasar.
I guess if no one gets this with in the next couple of days I should post a new question? Or should I just try and think of more hints?
The person who discovered these objects was one of the co-discoverers of the quasar.
I guess if no one gets this with in the next couple of days I should post a new question? Or should I just try and think of more hints?
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- #502
Cecil
- 20
- 0
I believe these stars are termed "blue stragglers". They are stars in a globular cluster that are on the main sequence, but to the left of the turn-off point. This means that they should have already burned out into red giants, but haven't yet evolved. In some sense, they appear to be normal stars, but younger than the other stars in the cluster. They were first found in M3 by Sandage in 1953 (had to look his name and date up, couldn't remember them OTOH).
A coalescion of two smaller stars that have not yet evolved would produce a such a blue straggler because, of course, more massive stars tend to be bluer and brighter. Mass transfer from a nearby binary "overflowing" its Roche lobe works in the same way to shift a star left-wards on the main sequence.
Of course, these stars exist everywhere in the universe, but they are only easily identified as BSs in a globular cluster due to the proximity of stars of precisely the same age.
Good question, and mine will follow as soon as I can think of one.
A coalescion of two smaller stars that have not yet evolved would produce a such a blue straggler because, of course, more massive stars tend to be bluer and brighter. Mass transfer from a nearby binary "overflowing" its Roche lobe works in the same way to shift a star left-wards on the main sequence.
Of course, these stars exist everywhere in the universe, but they are only easily identified as BSs in a globular cluster due to the proximity of stars of precisely the same age.
Good question, and mine will follow as soon as I can think of one.
- #503
Cecil
- 20
- 0
Okay. Is it possible for a pulsar to spin so fast that it breaks up, and are there any known mechanisms for this? How fast (% of c) does the surface need to be going for this to happen?
- #504
FZ+
- 1,604
- 3
If it spins so fast... why would it form in the first place?
- #505
SchrodingersCat
- 12
- 0
Congrats on your answer to the last question Cecil.
Well mv^2/r=GMm/r^2 (centripital force= gravity) sets this limit. Thus v=Sqrt[GM/r] where G is the gravitational constant. I will assum M~1.4Msolar and r=10km.
=> ~0.46c.
I believe another factor which actually occurs at lesser velocities involving gravitational radiation. This effect seems to not allow the pulsar to spin so fast and thus saves it from flying apart in such a manor.
Nice question!
FZ++ Well, it spins fast to conserve angular momentum. Neutron Stars have radii of 10e5 cm. Our sun for example has a radius on the order of 1e10 cm. This dramatic loss in radius causes it to have to spin faster in order to achieve conservation of angular momentum.
Well mv^2/r=GMm/r^2 (centripital force= gravity) sets this limit. Thus v=Sqrt[GM/r] where G is the gravitational constant. I will assum M~1.4Msolar and r=10km.
=> ~0.46c.
I believe another factor which actually occurs at lesser velocities involving gravitational radiation. This effect seems to not allow the pulsar to spin so fast and thus saves it from flying apart in such a manor.
Nice question!
FZ++ Well, it spins fast to conserve angular momentum. Neutron Stars have radii of 10e5 cm. Our sun for example has a radius on the order of 1e10 cm. This dramatic loss in radius causes it to have to spin faster in order to achieve conservation of angular momentum.
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- #506
SchrodingersCat
- 12
- 0
Sorry I have not been around for a while. I have been really busy. Umm... Cecil, do you want to ask another question? I am afraid I prolly will not be posting for a bit as I have a lot of other stuff to attend to.
- #507
Shadow
- 19
- 0
is that a no cecil?
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