(A) Topic 13 wrongs Flashcards
Describe the system used to differentiate the apparent magnitude between stars.
A bright star would have an apparent magnitude of 1, whereas a faint star would have a magnitude of 6.
What are the four factors magnitude depends on?
- total energy radiated by the star
- distance to the star
- the amount of interstellar gas and dust that reflects and absorbs light
- amount of light absorbed +scattered by the Earth’s atmosphere
What equipment is used to detect the spectrum of a star?
Spectometer
What does the spectrum tell us about the star?
Helps us identify the chemical elements present, the temperature of the star, and whether the star is moving toward or away from us in its line of sight (radial velocity)
What are absorption and emission lines?
Absorption: show what atoms are absorbing light - are dark
Emission: shows which atoms are emitting light
How can we tell a star’s radial velocity using the spectrum?
The radial velocity of a star can be measured by measuring the distance between certain spectral lines - we can tell its wavelength and by how much it shows redshift or blueshift
What is an HR diagram?
Graph in which the absolute magnitudes of stars are plotted against their spectral class
What are the main components of the HR diagram?
- magnitude
- spectral class
- the shape of the main sequence
- position of giants and super giants
- position of the sun
- position of white dwarfs
How is an HR diagram used to determine distances to stars?
Calculate the luminosity of the star and use the apparent brightness to work out its distance
What are arcminutes and arcseconds?
arcminute = 1/60 of a degree
arcsecond = 1/60 of an arcminute
Describe how scientists can use heliocentric parallax to establish distances to nearby stars.
Measure the distance to nearby stars by measuring how they appear to move against distant stars. For example, measure the star in one month, then again in six months when the Earth is on the other side of the sun
What is a light curve?
Graph that displays how bright an object is over a period of time
Define short period stars
Eclipsing binaries, cepheids or pulsating stars change magnitude over several days or weeks
Define long period stars
Giant stars with periods between 100-1000 days
Define eclipsing binary stars
Consists of a bright primary star and a dimmer second star. Large drop = secondary star blocks first and vice versa
Define cepheid variable stars
Class of giant yellow stars that expand and contract regularly
Define nova
A star that suddenly increases its output tremendously then fades away to its former obscurity in a few months or years
Define supernova
The explosion of a star
What is the equation used for star trail calculations?
angle of arc/ 360 = time exposure/24 hours
Name three benefits and drawbacks of the Earth’s atmosphere.
pros: - oxygen allows humans + animals to breath
- protect us from harmful radiation
- makes temperature and climate consistent
cons: - clouds regularly obscure good astronomical viewing
- refracts light which means less accurate position and clarity of star viewing
- pollution obscures observations
Why does the location of observatories matter? Name 3 factors which affect it.
- light pollution
- less atmosphere
- good dry weather with less clouds
Give a simple explanation of how radio telescopes work.
Large concave dish reflects radio waves to a focus, where an ariel converts radio waves into electrical signals that can be stored + processed
What can cause interference between the telescopes?
- telecommunications
- emergency services communications
- air traffic control
- television and FM/AM signals
Why are infrared telescopes located in high and dry locations?
Water vapour absorbs IR light, so high and dry conditions are ideal
What discoveries can be attributed to infrared telescopes?
- protostars
- dust and molecular clouds
- hotspots on the moon
Name three advantages and disadvantages of space telescopes.
pros:
- clearer observations (no distortions)
- wider wavelengths of the EM spectrum
- no limitations in terms of day and nighttime
cons:
- expensive
- difficult maintenance
- limitations with the Hubble Space Telescope : not being able to photograph some things due to light sensitivity
What does ultraviolet observation allow us to study?
Chemical make up and temperature of stars
What kind of objects produce X-rays?
Hotter objects outside of the visual band of the EM spectrum
What are Gamma-ray bursts?
Powerful explosions observed in distant galaxies - brightest EM events in the universe
What is X-ray used to observe?
Effects of fast-moving particles under a strong gravitational force that surround a black hole - an accretion disc
How does a telescope alter the appearance of binary stars and double stars?
They’re viewed as multiple stars
How does a telescope alter the appearance of open clusters?
Numerous individual stars can be seen
How does a telescope alter the appearance of globular clusters?
Detailed numerous stars can be seen
How does a telescope alter the appearance of nebulae?
More detailed shape + more obvious colours
How does a telescope alter the appearance of galaxies?
Brighter and more detailed view
