7.1 Stars

Question 1

What is astronomy?

Answer 1

The study of stars.

Question 2

What is the difference between apparent magnitude and absolute magnitude.

Answer 2

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.

Question 3

What is the difference between light years and parsecs?

Answer 3

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

Question 4

What is parallax?

Answer 4

A technique used to measure the distance to other stars.

Question 5

What is stellar parallax and what is it useful for?

Answer 5

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

Question 6

What are two factors that determine apparent magnitude?

Answer 6

1. How much light the star emits.

2. The distance between the star and Earth - the greater the distance, the dimmed the star will appear.

Question 7

What is a red giant?

Answer 7

A star produced when the core of a sun-sized star runs out on hydrogen.

Question 8

What is a stars colour due to?

Answer 8

The surface temperature of the star.
Hotter stars = cooler colours. emit Uv rays = makes them blue.
Cooler stars = warmer colours.

Question 9

What is a Planetary nebula?

Answer 9

A cloud of gas produced by radiation from a hot object

Question 10

What is a white dwarf?

Answer 10

Hot, dense star that is the remains of a red giant.

Question 11

What is a black dwarf?

Answer 11

Cold, dark remains of a white dwarf.

Question 12

What is a blue super giant?

Answer 12

Stars that are ten or more times more massive than the sun.

Question 13

What is a supernova?

Answer 13

A giant explosion that occurs when a star many times larger than our sun runs out of nuclear fuel.

Question 14

What is a neutron star?

Answer 14

A remnant of a supernova, consisting entirely of neutrons.

Question 15

What is a black hole?

Answer 15

Aka collapsed star,

A star so massive that not even light can escape from its gravitational field.

Question 16

What determines a stars spectrum?

Answer 16

By its surface temperature.
Cooler stars = warmer colours
Hotter stars = cooler colours because of UV rays
In between extremes = white, yellow

Question 17

What colours do cooler and hotter stars emit?

Answer 17

Cooler = Orange, Red
Hotter = Blue, Purple

Question 18

What is a spectrometer?

Answer 18

A device that splits light into a spectrum to show its component wavelengths.

Question 19

How can scientists determine what chemical elements are present in a star?

Answer 19

From distinctive lines that appear in its spectrum.

Some elements emit colours of particular wavelengths = can be measured to determine elements in star.

Question 20

What are Fraunhofer lines and why do they occur?

Answer 20

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

Question 21

What information about the star can be gained from observing Fraunhofer lines?

Answer 21

Shows the absorption that would be emitted by the element when it’s extremely hot.

Question 22

What is ‘spectral class’?

Answer 22

A classification system for stars based on their colour.

Question 23

What does a stars spectral indicate about the star?

Answer 23

The elements present in the star, the temperature and the colour of a star.

Question 24

What makes a star so hot?

Answer 24

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)