🔭astrophysics🔭

Power is proportional to ?

I x distance squared

intensity is proportional to ?

1 / distance squared

how is a white dwarf produced?

when nuclear fusion stops so outward pressure disappears and the core contracts

in a converging telescope, if fo>fe min ang resolution …?

large

telescopes form virtual image through eye lens at ?

infinity

CCD spatial resolution is ?

10 micro meters

eyes spatial resolution is ?

100 micro meters

dim star, absolute magnitude is positive or negative?

positive

what does earths atmosphere absorb?

most UV some IR

define absolute magnitude

magnitude of object if object is 10 pc from earth

define resolving power

a measure of how much detail a telescope can see

what causes spheric aberration?

distorted mirror

how long does light take to get to earth?

8 minutes

what is a neutron stars density?

4×10 power of 17 kgm

what 2 words describe the universe?

isotrophic and homogenous

high proportion of He supports big bang because?

universe was once hot enough to fuse H to He.

define rayleigh criterion

minimum subtended angle between 2 objects that can be resolved

what is a quasar?

active galactic nuclei

orbiting systems have periodic doppler shift due to what?

orbital centre of mass

hubbles law is not reliable over large distances because?

dark energy

what is the axis or symmetry called?

principle axis

define focal length

the distance between the centre of the lens and the principle focus

with a telescope in normal adjustment, is Fo or Fe bigger

Fo

what makes M=Fo/Fe unusable?

it both angles are bigger than 10 degrees

what is chromic aberration?

when a lens refracts different colours different amounts so there’s blurring and coloured fringes around the image

how can you fix aberration in lenses?

use a convex then concave lens to ensure the focus point is the same

what is a concave and convex lens cemented together called?

achromatic doublet

when you increase the size of mirror what happens?

you can see fainter objects

what is collecting power proportional to?

diameter²

define rayleigh criterion?

two objects will be resolved if the centre or the diffraction pattern of one image coincides with the first minimum of the other

where must infrared telescopes be?

in space

where just UV telescopes be?

in space

what configuration are UV telescopes in?

cassegrain

where are x-ray telescopes found?

space

what is the hipparcos scale?

defines brightness of stars in terms of apparent magnitude between 1 and 6

what is stefans law in words?

the power output of a star is directly proportional to its surface area and its (absolute temperature)^4

what is wiens law in words?

the wavelength of a stars emission at peak intensity is inversely proportional to it’s absolute temperature

what is a black body?

something that absorbs all EM radiation and can emit all EM radiation (no reflection at all)

what is dark energy?

energy that has an overall repulsive effect throughout the universe

what is hubbles law in words?

the velocity of receding galaxies is proportional to their distance from Earth

what is an exoplanet?

planets not in our solar system

what is a galaxy?

a collection of billions of stars