Astronomy Trivia Challenge: Can You Answer These Questions About the Night Sky?

[SchrodingersCat]

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?

 

[Cecil]

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.

 

[Cecil]

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?

 

[FZ+]

If it spins so fast... why would it form in the first place?

 

[SchrodingersCat]

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.

 

[SchrodingersCat]

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.

 

[Shadow]

is that a no cecil?