7.1 Stars Flashcards
(24 cards)
What is astronomy?
The study of stars.
What is the difference between apparent magnitude and absolute magnitude.
Apparent magnitude: a measure of the brightness of a star as it appears to an observer in Earth.
Absolute magnitude: a measure of how bright a star would appear if it was 10 parsecs from Earth.
What is the difference between light years and parsecs?
Light years/ L.y: the distance light travels in a year, approximately 9,500,000,000,000,000 km/ 9.5 trillion km.
Parsecs: an astronomical unit of length equal to 3.26 L.y
1 parsec = 3.26 light years
Convert from L.y to parsecs:
Distance in light years
Divided by 3.26
Convert parsec into L.y:
Distance in L.y x 3.26
What is parallax?
A technique used to measure the distance to other stars.
What is stellar parallax and what is it useful for?
The apparent change in the position of a star throughout the year due to the Earth’s motion around the Sun.
GOOD = Using two different perspectives: You can find out how much they shift between. See distance between us and star.
BAD = unreliable after certain distance
What are two factors that determine apparent magnitude?
- How much light the star emits.
2. The distance between the star and Earth - the greater the distance, the dimmed the star will appear.
What is a red giant?
A star produced when the core of a sun-sized star runs out on hydrogen.
What is a stars colour due to?
The surface temperature of the star.
Hotter stars = cooler colours. emit Uv rays = makes them blue.
Cooler stars = warmer colours.
What is a Planetary nebula?
A cloud of gas produced by radiation from a hot object
What is a white dwarf?
Hot, dense star that is the remains of a red giant.
What is a black dwarf?
Cold, dark remains of a white dwarf.
What is a blue super giant?
Stars that are ten or more times more massive than the sun.
What is a supernova?
A giant explosion that occurs when a star many times larger than our sun runs out of nuclear fuel.
What is a neutron star?
A remnant of a supernova, consisting entirely of neutrons.
What is a black hole?
Aka collapsed star,
A star so massive that not even light can escape from its gravitational field.
What determines a stars spectrum?
By its surface temperature.
Cooler stars = warmer colours
Hotter stars = cooler colours because of UV rays
In between extremes = white, yellow
What colours do cooler and hotter stars emit?
Cooler = Orange, Red Hotter = Blue, Purple
What is a spectrometer?
A device that splits light into a spectrum to show its component wavelengths.
How can scientists determine what chemical elements are present in a star?
From distinctive lines that appear in its spectrum.
Some elements emit colours of particular wavelengths = can be measured to determine elements in star.
What are Fraunhofer lines and why do they occur?
Missing colours = dark lines. Suns dark lines in spectrum.
Dark lines = due to light interacting with atoms in outer layers of the star.
See Figure 7.1.6
What information about the star can be gained from observing Fraunhofer lines?
Shows the absorption that would be emitted by the element when it’s extremely hot.
What is ‘spectral class’?
A classification system for stars based on their colour.
What does a stars spectral indicate about the star?
The elements present in the star, the temperature and the colour of a star.
What makes a star so hot?
Nuclear Fusion.
The enormous gravitational forces within a star can heat the material at its centre.
AND
Proton + proton -> deuterium + positron + neutrino + energy (See 7.1.7)
