Astronomy | Astrophysics Answers

When the Sun was a protostar, it had a maximum luminosity about 1000 times its present luminosity and a surface temperature about 1000K. What was its radius? Assume that the star radiates like a blackbody.

.The two stars in a binary system have an orbital period of 5 years and an orbital separation, a, of 10AU. What is their combined mass?

In a model of the universe, the Hubble parameter has the following functional form H(z) = H0(1 + z)^(5/4), where H0 is the Hubble constant.

Answer the following questions:

1. Can a spectrograph that operates in the visible region of the electromagnetic spectrum (i.e. 0.38 um to 0.74 um) detect the Hb (H beta) line from a galaxy with a comoving distance D = c/2H0 (c being the speed of light).

2. How long did it take for light to reach an observer, at the present time, from a galaxy that has a redshift z = 2.0? Assume H0 = 67 km/s Mp/c. Express your result in Gyr.

Inflation theory predicts that even the most distant observable parts of the universe should have very similar properties.

Why? Pick one of the answers below which is a crucial part of this explanation.

1)Because of the exponential growth in the size of the universe.
2)Because of spontaneous symmetry breaking.
3)Because of the Higgs field.
4)Because of the unification of the forces of nature.
5).Because of the amplification of quantum mechanical fluctuations

The big rip theory suggest the possibility of the universe being ripped apart by the force of dark energy. With some physicist suggesting it’s going to be too severe to the extend that individual atoms will be ripped off from the universe, leading to a complete annilation but isn’t an exponential expansion and an actual interstellar redshift supposed to mean at one point, everything will be so far from each other? So how is everything going to be ripped apart?

Do particles(including all the quarks and other elementary particles) creating themselves and annihilating provide the bigger clue to the possibility of a parallel universe and if no, then any reason?

All the 4 fundamental forces of nature are a by-product of the big bang, (Gravity and the 2 nuclear forces), then which force held the energy that resulted in the big bang together, and if energy can be packed in a single position, is it not supposed to be contained by something?

It’s said that everything before the big bang was packed in a super-dense tiny atom size position, but where did that energy come from, and what could have ignited the supernovae?

If particles can create themselves by borrowing some energy from its surrounding, as favored by the uncertainty principle, then,
1) How come everything is perceived to have come to existence only about a billion years after the big bang, including all the quarks and other elementary particles are given that there’s an endless possibility they could have acquired enough energy from a fluctuation to survive long enough?

The star Wolf 359 is at a distance of 7.8 light-years from Earth. A radio signal from Wolf 359 is detected by a radio telescope on Earth.

(A) (i) State the speed of the radio waves.
(ii) Calculate the distance, in metres, from Wolf 359 to Earth.

(B) another telescope is used to observe the same star in the visible part of the spectrum.
(i) State a suitable detector of visible light that may be used in this telescope.
(ii) State either the time taken for the visible light from the star to reach Earth is less than, equal to or greater than the time taken for the radio waves from the star to reach Earth.