Anyone up for a Astrophysics Marathon? (1 Viewer)

[nirukk]

Explain why a white dwarf does not collapse further. (2mks)

White dwarfs have a solar mass of less than 1.4 (Chandrasekar Limit). This means that the electron degeneracy pressure can hold back its gravitational collapse, causing it to be more denser and no longer undergoes fusion reaction.

Correct me if I am wrong.

 

[kiinto]

White dwarfs have a solar mass of less than 1.4 (Chandrasekar Limit). This means that the electron degeneracy pressure can hold back its gravitational collapse, causing it to be more denser and no longer undergoes fusion reaction.

Correct me if I am wrong.

Correct. However, you may want to review the wording of the last part.

 

[someth1ng]

Correct. However, you may want to review the wording of the last part.

Agreed.

As far as I know, electrons try to avoid to be pushed into the nuclei of atoms from the pressure and do you want to be on the same energy level as according to the Pauli exclusion principle. Hence, electron degeneracy pressure (outward) is in equilibrium with gravity.

 

[Shadowless]

Could someone differentiate for me, adaptive optics, interferometry and active optics?

 

[DamTameNaken]

Could someone differentiate for me, adaptive optics, interferometry and active optics?

This is so late and you've probably already got the answer but for all you curious onlookers the distinction is easy enough to understand.

Adaptive Optics: Corrects for bending in the mirror due to gravity. This allows for lighter mirrors that aren't as thick that can be more easily moved around, it also makes sure that the surface is the most accurate shape. The shape of the mirror is corrected every several minutes.

Active Optics: Corrects for atmospheric effects such as 'seeing', the telescope focuses on a nearby target star while at the same time observing the desired star, when the target star becomes distorted there is a mirror that bends to counteract and accomodate for the seeing effects. The shape of the mirror can be changed several thousand times a second, so it is very much 'real time'.

Interferometry: Used with radio waves to provide a much needed large baseline. The signal received by the two satellites is sent to a certain point. The interference patterns can provide information on the star.

 

[DamTameNaken]

And question.

'Explain how Cepheid Variables are used to determine distances to galaxies.'

 

[someth1ng]

And question.

'Explain how Cepheid Variables are used to determine distances to galaxies.'

That was the one about the period length being proportional to the average magnitude of the Cepheid. Therefore, measuring the period of pulsation of the Cepheid, its average absolute magnitude can be estimated and hence, using distance-modulus formula, distance can be calculated.

(Insert the formula during the explanation)