Astronomy | Astrophysics Answers

(a) Why is it difficult for LyC radiation to escape galaxies with high star formation rates?

A warning system has calculated that two asteroids will collide not far from Earth any time soon.
The smaller asteroid has the mass m and moves with the velocity vm. The bigger asteroid has the
mass M = 3m and the velocity of vM =
1
2
vm. They collide at an angle of α = 60◦ and turn into a
single heavy asteroid (inelastic collision):
M
m
α
β
(a) Calculate the velocity of the single object aer the collision.
(b) Determine the angle β aer the collision.

You are the captain of a spaceship that is circling through a binary star system. Due to the gravitational forces and the rocket engines, the orbit of your spaceship looks like that:
The position of your spaceship (in AU) at the time t (in days) is given by:
x = 5 sin(t) y = sin(2t) z = 0
(a) How long does it take your spaceship to circle the orbit once?
(b) Find an equation that calculates the velocity v(t) of your spaceship at a given time t.
(c) The two stars are positioned at the points (4, 0, 0) and (−4, 0, 0): What is the distance of your
spaceship to the stars at the time t =
π
2
?

The Moon has a mass of M = 7.3 · 1022 kg, a radius of R = 1.7 · 106 m and a rotation period of
T = 27.3 days. Scientists are planning to place a satellite around the Moon that always remains
above the same position (geostationary).
(a) Calculate the distance from the Moon’s surface to this satellite.
(b) Explain if such a Moon satellite is possible in reality.

You have discovered a new star in the Milky Way: Your new star is red and has 3/5 the temperature of our Sun. The new star emits a total power that is 100,000 times greater than the power
emitted by our Sun.
(a) Determine the spectral type (i.e. spectral classification) of the new star.
(b) How many times bigger is the radius of the new star compared to the radius of our Sun?

The diameter of the Sun is 1.39 million kilometres and the Earth is 8.3 light minutes far away.
Proxima Centauri is the nearest star - it has a distance of 4.24 light years to our Sun.
(a) How long does it take to travel to Proxima Centauri with
(i) an airplane (920 km/h) or
(ii) with the Voyager 1 space probe (17 km/s).
(b) Let the Sun have the size of a tennis ball (diameter: 6.7 cm): How far away is the Earth and
how far away is Proxima Centauri on this scale?

For a special mission to Mars you need to know the smallest distance between Earth and Mars.
However, you have lost your astronomy book and you could only find these values:
Distance Earth to Sun: 149.6 million km
Orbital period Earth: 1.00 years
Orbital period Mars: 1.88 years
By using these values and assuming that Mars and Earth move an circular orbits, calculate the
smallest possible distance between Earth and Mars.
Expert's answer

The Milky Way has a diameter of about 150,000 light years. Our solar system is located 27,000
light years from the center of the Milky Way and orbits the center with a speed of 220 km/s.
(a) How long does it take for the solar system to circle the center of the Milky Way?
(b) The earth has formed about 4.5 billion years ago. How oen has the earth circled the center?

What protects astronauts from the lack of gravity

Problem A.3 :
The stellar parallax of the star Arcturus in the constellation Boötes was measures with 0.0900
.
(a) Calculate the distance (in parsec) between Arcturus and the Earth.
(b) How long does it take to send a light message from Earth to Arcturus?