Exploring starlight Flashcards
what is absolute magnitude
true brightness of a star
absolute magnitude is defined at the stars apparent magnitude if the star was 10 PC away from us
what information can be obtained from a stellar
spectrum
chemical composition temperature radial velocity sunspot or starspot cycle wave length revolution of a star
Understand how stars can be classified according to spectral type
classified by their spectra (the elements that they absorb) and their temperature.
What is the name of the technique used by astronomers to study the chemical composition of a star?
spectroscopy
What is the name of the diagonal band running from top left to bottom right on a H-R Diagram?
main sequence
what is 1 degree in arcmins and 1 arcmin in arcseconds?
1 degree = 60 arcmins
1 arcmin = 60 arcseconds
what is apparent magnitude?
brightness of stars as observed from Earth in the night sky
how is a star’s colour and spectral type related
to its surface temperature
The surface temperature of a star determines the color of light it emits.
Understand the inverse square relationship between distance and brightness/intensity
light intensity is proportional to 1/d^2
define magnitude
how bright an object appears to the naked eye
Understand the term parsec (pc)
distance from earth to a star that subtends a parallax angle of 1 arc second
how can you work out parallax angles and distance
parallax angle = 1 / d
d = 1 / parallax angle
if tan parallax = 1 / d
parallax = 1 / d
Understand how a star’s life cycle relates to its position on the Hertzsprung-Russell diagram, for stars similar in mass to the Sun and those with masses that are much greater
OBAFGKM - O = hottest, M = coolest
Understand the light curves of the following variable stars: a short/long period b eclipsing binary c Cepheid d novae and supernovae
short/long period - changes magnitude over several days or weeks.
eclipsing binary - dips, at 24 hours, stays at 2.5 luminosity till 60 hours then dips
cepheid - light they produce dip and rise over a short period of time, returning to the same luminosity a few days later.
novae and supernovae - When it explodes, the luminosity increases by many magnitudes. The star reverts back to its former brightness after a period of 30 to 100 days.
Understand the causes of variability in the light curve of eclipsing binary stars
when one star is brighter than the other and darker star moves in front of it.
Understand how Cepheid variables can be used to determine distances
compare the Cepheid variable’s apparent brightness with its intrinsic brightness. difference between observed and actual brightness yields the distance.
Understand the structure of gravitationally bound stellar groupings such as binary stars and clusters
binary stars - two stars that orbit around a common centre of orbit.
clusters:
open - groups of stars close to each other in space. usually very bright, found around galactic plane
globular clusters - spherical shaped with more stars nearer the nucleus. located around the galactic nucleus
Understand how the period of an eclipsing binary star can be deduced from its light curve
from when the luminosity dips
what are most modern astronomical observations recorded with?
digital sensors that convert light into electrical
signals, which can then be processed and stored as data files
what radiation does the earth’s atmosphere not block out?
visible light and radio waves
what can only be located at sea level on the Earth’s surface
only optical and radio telescopes should be located
at sea level on the Earth’s surface
Understand how astronomers obtain and study the patterns of spectral lines in the light from astronomical objects
when looking at stars with a spectrometer, the spectrum tells us what atoms are present in the star and what atoms are absorbing the light
Understand why radio telescopes need extremely large apertures in order to maintain a useful resolution
the larger the diameter, greater the resolution
wavelength of radiowaves are very long
Understand how multiple radio telescopes can operate as an aperture synthesis system (array)
when they connect to other dishes, they give a greater resolution and and use the process of interferometry to combine signals
what has radio astronomy been important for?
discovery of quasars, jets from black holes, the structure of the Milky Way and protoplanetary discs
what has infrared astronomy been important in?
discovery of protostars, dust and molecular clouds and
hotspots on moons
Understand the detrimental effect of the Earth’s atmosphere on the quality of images formed by telescopes on the Earth’s surface
The Earth’s atmosphere blocks all X-rays from space, so space telescopes must be used to observe in these wavelengths
Understand why telescopes operating outside the optical and radio ‘windows’ need to be sited above the Earth’s atmosphere
Less infrared light penetrates to the surface so a higher location is better
to study x-rays and gamma rays
Understand the advantages and disadvantages of space telescopes and detectors, including orbital observing platforms
advantages: clear observations wider wavelengths of em spectrum no limitations to observing at night time disadvantages: expensive maintenance is difficult
Understand how gamma ray, x-ray and ultraviolet astronomy have been important in the discovery of gamma ray bursts, black hole accretion discs and the corona and chromosphere structure of young stars
Ultraviolet observation lets us study the chemical make-up and temperature of stars and lets us see stars at different stages of their evolution. sun is observed in UV to see corona and chromosphere in detail.
strong gravitational forces that surround a black hole can be observed in the x-ray part of the spectrum.
Understand how a telescope alters the appearance of: a stars b double stars c binary stars d open clusters e globular clusters f nebulae g galaxies
a) appears as dots of light to naked eye - telescope: sharper dots of light
b) naked eye - Appear as single star. Telescope: Viewed as multiple stars
c) naked eye - Can just be seen as two stars in dark light. Telescope: Viewed as multiple stars
d) naked eye - Faint stars in close proximity. Some individuals can be seen. Telescope: Numerous individual stars can be seen
e) naked eye - Appear as vague ‘blur’. Telescope: Detailed numerous stars can be seen
f) naked eye - Appears as small but slightly brighter ‘blur’. Telescope: Shape is more detailed. Colours are more obvious.
g) naked eye - difficult to view. Telescope: brighter and detailed view
Explain the connection between the dark absorption lines and the chemical composition of the star
light passing through outer layers is made of all wavelengths/energies. some of this light has correct wavelength to excite atoms in stars outer layers. when atoms de excite they emit radiation of same wavelength
what are the 7 types of the electromagnetic spectrum
radio waves, microwaves, infra red radiation, visible light, ultra violet light, xrays, gamma rays
