Astronomy | Astrophysics Answers

A 10 keV electron is moving in a circular orbit of radius 1 m in a plane at right angles to a uniform magnetic field. What is:

(a) the speed of the electron?

(b) the magnitude of the magnetic field?

(c) the frequency of revolution?

(d) the period of motion?

1) The magnitude of the Earth’s magnetic field is about 0.5 Gauss near Earth's surface. What’s the maximum possible force on an electron near the Earth’s surface with kinetic energy of 1 keV? How does this compare to the gravitational force on the electron near the Earth’s surface?

Difference between rigid body rotation and keplerian motion

How does the ring system of jovian planets persist for so long?

A research team has discovered that a moon is circling a planet of our solar system: The moon orbits the planet once every 7 hours on a nearly circular orbit in a distance R of 48000 km from the centre of the planet. Unfortunately, the mass m of the moon is not known. Use Newton’s law of gravitation with G = 6.67 · 10−11 m3 /(kg·s 2 ) to approach the following questions: F = G · mM R2 (1) (a) Based on the observations, determine the total mass M of the planet. (b) Which moon and planet of our solar system is the team observing? (

Something massive seems to live in the centre of the Bloodstain - stars close to it are moving really fast. One such star (BZ2) is observed to be moving in an edge-on circle around the central mass. From the Doppler effect, its speed is measured to be 89000 km/s. And when passing in front of the central mass, it has an apparent side-ways speed of 3 arcsec per (Earth) year.

It is not possible to measure the distance to the Bloodstain using parallax - Zing's orbit is too small and the Bloodstain too far away. But perhaps we can use these motions around the central mass to calculate a distance?

Use these numbers to calculate the distance from Zing to the centre of the bloodstain (in parsecs):

Where in the night sky can you observe the famous double star system Mizar and Alcor?

a) A particular emission line is originally emitted with a wavelength of 556.3 nm from a gas cloud. At our telescope, we observe the wavelength of the emission line to be 556.6 nm. How fast is this gas cloud moving toward or away from Earth?

b) Two stars have the same size and are the same distance from us. Star A has a surface temperature of 5500 K, and star B has a surface temperature twice as high, 11,000 K. How much more luminous is star B compared to star A?

c) What is the value of power received in orbit around Mars by a 1 m² solar panel? Assume Mars is 1.5 A.U. from the Sun at the time of measurement. 

a) . If the emitted infrared radiation from Pluto, has a wavelength of maximum intensity at 75,000 nm, what is the temperature of Pluto assuming it follows Wien’s law?

b) What is the energy of the photon with the wavelength of 150 nm? 

c) Would you prefer to be irradiated by radio wavelength radiation or gamma ray wavelength radiation? Why? 

a) What is the wavelength of the carrier wave of a campus radio station, broadcasting at a frequency of 97.2 MHz (million cycles per second or million hertz)?

b) What is the frequency of a red laser beam, with a wavelength of 670 nm, which your astronomy instructor might use to point to slides during a lecture on galaxies?

c) Can you hear sounds in space? Why or why not?