Chapter 2 Surveying the Stars

Question 1

What is a light year?

Answer 1

A light year is the distance light travels through space in 1 year

Question 2

What is Parallax

Answer 2

Parallax is the effect where close stars shift in position against the background of more distant stars as the Earth moves around it’s orbit

Question 3

What is an Astronomical Unit

Answer 3

An Astronomical Unit is the distance between the Centre of the Sun and the Earth

Question 4

What is the Parallax angle

Answer 4

The Parallax angle is defined as the angle subtended to the star by the line between the Earth and the sun.

Question 5

What is a Parsec

Answer 5

A parsec is defined as the distance to a star which subtends as an angle pf 1 arc second to the line from the centre of the Earth to the centre of the Sun

Question 6

What two scales calculate the intensity of stars?

Answer 6

Absolute Magnitude & Apparent Magnitude

Question 7

What is the Absolute Magnitude?

Answer 7

Absolute Magnitude is the defined as the star’s apparent magnitude of brightness if the star was a distance of 10 parsecs from earth

Question 8

What is Apparent Magnitude

Answer 8

Apparent Magnitude is the magnitude of brightness of a star from it’s current distance from the Earth

Question 9

What is a Black Body

Answer 9

A Black body is defined as a body that is a perfect absorber of radiation (absorbs 100% of radiation incident on it at all wavelengths) and therefore emits a continuous spectrum of wavelengths, because of this, stars can be said to be Black Body Emitters

Question 10

What are the Spectral Classes of Stars

Answer 10

O, B, A, F, G, K, M

Question 11

What are the characteristics of a star in the O spectral class

Answer 11

Stars in the O spectral class have an intrinsic Blue colour, a temperature between 25000 and 50000 Kelvin, and prominent neutral helium, Helium and Hydrogen Absorption Lines

Question 12

What are the characteristics of a star in the B spectral class

Answer 12

Stars in the B spectral class have an intrinsic Blue colour, a temperature between 11,000 and 25,000 Kelvin and have prominent Helium and Hydrogen Absorption Lines

Question 13

What are the characteristics of a star in the A spectral Class

Answer 13

Stars in the spectral class A have an intrinsic blue-white colour, a temperature between 7500 and 11000 kelvin and have strong Hydrogen absorption lines as well as ionised metal absorption lines

Question 14

What are the characteristics of a star in the F spectral class

Answer 14

Stars in the spectral class F have an intrinsic White colour, a temperature between 6000 and 7500 Kelvin and have ionised metal absorption lines

Question 15

What is the characteristics of a star in the G spectral class

Answer 15

Stars in the Spectral Class G have an intrinsic Yellow-white colour, a temperature between 5000-6000 Kelvin and have ionised and neutral metals in their absorption lines

Question 16

What is the characteristics of a star in the K Spectral Class

Answer 16

Stars in the Spectral Class K have an intrinsic orange colour, a temperature between 3500-5000 Kelvin and have neutral metals in their absorption lines

Question 17

What is the characteristics of a star in the M spectral class

Answer 17

Stars in the Spectral Class M have an intrinsic Red colour, a temperature between 2500-3500 Kelvin and have neutral metals in their absorption lines

Question 18

What are the different classes of stars

Answer 18

Brown Dwarf, White Dwarf, Main Sequence, Giant & Supergiant

Question 19

What is the evolutionary sequence of a low mass star

Answer 19

For Main Sequence stars they eventually run out of Hydrogen to continue Hydrogen fusion, this disrupts the equilibrium between the Thermal Forces and the Gravitational pull of the Stars core, causing the star to balloon outwards and become a Giant class star, one this star can no longer fuse carbon in its core this equilibrium is lost once more and the outer shell flies away becoming a Planetary Nebula while the core becomes a white dwarf, which eventually cools down to become a Brown Dwarf

Question 20

What is the Evolutionary Sequence for high mass stars

Answer 20

for high mass stars the sequence is largely the same, however when they run out of hydrogen to fuse in the core, they instead become super-giant stars, which once they can no-longer fuse carbon in their core they explode into a supernova, which later forms into a neutron star, the core of a supernova after all the surrounding matter has been thrown off into space.

Question 21

What is the evolutionary sequence for very high mass stars

Answer 21

for stars of a very high mass the sequence is largely the same as high mass stars up to the Supernova stage, at this stage the supernova collapses in on itself due to the gravitational strength of the matter which makes it up, this process results in the formation of a black hole.

Question 22

What are the three classes of Black Holes?

Answer 22

Normal Black Hole, Supermassive Black Hole and Primordial Black holes

Question 23

what are normal black holes?

Answer 23

Normal Black holes are objects of immense mass, they have such a large mass that their gravitational pull is so strong that from a certain distance from it, even light cannot escape, this distance is known as the schwarzschild radius.

Question 24

What are Primordial Black Holes

Answer 24

Primordial Black Holes are black holes which formed as a result of the Big Bang, as the universe expanded it was theorised that in objects of immense mass black holes formed almost instantly, instead of from the collapse of a supernova these black holes formed from massive amounts of mass collapsing in on themselves due to the big bang. The main evidence for their existence comes from the evidence of early supermassive black holes.

Question 25

What are Supermassive Black Holes

Answer 25

Supermassive Black Holes are black holes that have a much stronger gravitational pull than their normal counterparts, they usually reside in the center of galaxies, and have grown to this titanic mass through the accretion of matter and through merging with other black holes (usually thought to be Primordial Black Holes)

Question 26

What do short-lived Gamma ray bursts correspond to?

Answer 26

Short lived gamma-ray bursts can correspond to black holes, with their source either being the merging of neutron stars to form a black hole or a neutron star falling into a black hole

Question 27

what do long-lived Gamma ray bursts correspond to?

Answer 27

Long lived gamma-ray bursts can correspond to the collapse of a massive star into a supernova

Question 28

What is a Standard Candle

Answer 28

A standard candle is an object with a known Absolute magnitude, an example of this can be Type-1A Supernova.