Lecture 6 Flashcards
how do different wavelengths help to view universe
different wavelengths give different views
all wavelengths dominated by Milky Way stars and gas
what is the universe visually dominated by
galaxies
where do we believe galaxies sit
inside much larger and heavier clouds of dark matter
what does IR allow us to see
through cosmic dust, distant universe is also red shifted so need IR to seee more distant galaxies
what do forming stars give off
UV
what does UV allow us to see
short lived massive stars so star forming regions
only saw by space telescopes as absorbed by atmosphere
what do x rays and gamma rays allow us to see
high energy sources e.g. accreting black holes, hot gas
again, absorbed by atmosphere so only space telescopes can observe them
what does radio waves allow us to see
dominated by jets and such from black holes, the matter gets spread out across the universe affecting distribution
allows to see cosmic dawn
what is cosmic dawn
era when first stars and galaxies emitted light
can see with radio wave as hydrogen gives out wavelength of 21cm.
maps how structures in universe formed, pattern of galaxies and matter
what is photometry
coloured filter put infront of telescope to filter light and see how much of a specific colour an object emits by using different filters and measuring
what is spectroscopy
light is split by wavelength with a prism, measure each wavelength brightness separately, instead of picture we get a spectrum
negatives for spectroscopy
light split up is fainter so takes longer to measure than for any given object in photometry
cant measure as many objects in the same time, cant see faint things
positives for spectroscopy
can look for emission/absorption at a specific wavelength as signatures of chemicals
can learn about movement of the light source
what is doppler shift
receding objects look redder
advancing look bluer
what is red light
longer wavelength, waves squash and stretch which shifts the whole spectrum
what is atmospheric distortion
stars and smaller galaxies twinkle due to earths atmosphere
turbulent layers bend paths of light
limits how clearly we can see smaller objects,
can make close objects seem like one
what is atmospheric absorption
earths atmosphere absorbs wavelengths
all of gamma, x rays, most of uv, lots of ir and all microwave
what can IR and microwave astronomy be done from
high altitude or even balloons - suggested by Charles piazzi smith
what wavelength does not have a value in space telescopes
radio
pros and cons of space telescopes
high res, high energy, can see motion of stars and even distant galaxies and the faintest stars
VERY expensive, usually technology used in the telescope is obsolete by the time it launches
