A, B, and D above.
Star D appears twice as bright as star C
Star C appears twice as bright as star D
Star C appears four times as bright as star D
Star D appears four times as bright as star C
It has a transverse velocity that is toward us.
Its surface temperature is higher than that of the Sun.
It has a radial velocity that is toward us.
It has a radial velocity that is away from us.
It has a transverse velocity that is away from us.
Proportional to temperature
Inversely proportional to temperature
Proportional to temperature to the fourth power
Inversely proportional to temperature to the fourth power
Both a and c above
The Earth's atmosphere easily absorbs it at the upper atmosphere
Very few objects emit at ultraviolet wavelengths
No space-based telescopes operate at ultraviolet wavelengths
Only the lowest mass stars emit ultraviolet light
Poor light gathering power.
Poor resolving power.
Poor magnifying power.
Interference from nearby sources of radio waves.
The low energy of radio photons.
A radio observatory
An adaptive optics observatory
An X-ray observatory
A large optical observatory
Visible and Ultraviolet
Visible & Radio
Microwave & Radio
Ultraviolet & Infrared
X-ray & Gamma-ray
The electron makes the transition from energy level 3 to energy level 2.
The electron makes the transition from energy level 2 to energy level 3.
The electron makes the transition from energy level 2 to energy level 1.
The electron makes the transition from energy level 1 to energy level 2.
The electron makes the transition from energy level 3 to energy level 4.
Lack of chromatic aberration
Shorter length for the same aperture size
Lighter weight for larger apertures
All of the above are valid reasons
The solar wind
The early universe
Brown dwarf stars
The absolute zero temperature.
The ground state.
The ionization level.
Responsible for Doppler shifts.
The energy level from which the Paschen Series of hydrogen originates.
Will not penetrate Earth's atmosphere and reach the ground.
Has a wavelength that is longer than the visible light emitted by the star.
Has a wavelength that is shorter than the X-rays emitted by the star.
A and b
B and c
A bright (emission) line
A dark (absorption) line
A bright (emission) line
Photons with longer wavelengths have lower frequencies
Radio wave photons have shorter wavelengths than gamma ray photons
X-rays can be transmitted through the atmosphere around the world
All of the above are true
All of these determines the element
None of these determines the element
Here's an interesting quiz for you.