Chapter 5.1 - 'Measurements in the Universe'

Question 1

Arc second.

Equal to…

Answer 1

Equal to 1/3600 of a degree

Question 2

AU.
Short for…
Equated to…

Answer 2

Short for Astronomical Unit.

Equated to: AU = 2πr/360*3600

Question 3

pc.
Short for…
Equated to…

Answer 3

Short for parsec.

Equated to: pc = 1/p

Question 4

Earths closest star.
Known as…
Angle of x p…
Distance of x pc…

Answer 4

Known as Proxima Centauri.
Angle of 0.77 p.
Distance of 1.30 pc.

Question 5

1 AU.
Equivalent to x m…
Equivalent to x ly…
Equivalent to x pc…

Answer 5

Equivalent to 1.496*10^11 m OR 14.96m km
Equivalent to 63240 ly.
Equivalent to 206265 pc.

Question 6

1 ly.

Equivalent to…

Answer 6

Equivalent to 3*10^8 m/s

Question 7

Milky Way.
Predicted to be x amount of stars…
Universe.
Predicted to be x amount of galaxies…

Answer 7

Predicted to be several hundred billion stars in the Milky Way.

Predicted to be a hundred billion galaxies in the universe.

Question 8

Nebula.

Defined as…

Answer 8

Defined as a cloud of gas in outer space.

Question 9

Cepheid variables.

Defined as…

Answer 9

Very large, luminous yellow stars that change brightness in continuous cycles.

Question 10

Intrinsic brightness.

Relates to…

Answer 10

Relates to the actual or natural brightness regardless of distance.

Question 11

Brightness of stars.
Measured in…
Lower values relate to…
Each value corresponds to the next by…

Answer 11

Measured in magnitudes.
Lower values relate to brighter stars.
Each value corresponds to the next by 2.5 times.

Question 12

Two brightness stars in the sky.
First known as…
Second known as…
Relativity of distance of both…

Answer 12

First known as Canopus.
Second known as Sirius.
Relativity of distance of both find that Canopus is 36 times further.

Question 13

Parallax angle.
Defined as...
Measure of...
Measured by...
Measured in...

Answer 13

Defined as the angle subtended by the radius of the earths orbit (1 AU) as it would be seen at the distance of the star.
Measure of distance to a star.
Measured by size of the angle, the larger the closer.
Measured in arc seconds.

Question 14

Spectra.
Different gasses will absorb…
Wavelengths that have been absorbed will be…
These will be apparent as…

Answer 14

Different gasses will absorb different wavelengths.
Wavelengths that have been absorbed will be missing from the spectrum.
These will be apparent as black lines.

Question 15

Wavelength and colour.
Blue wavelengths will be around x…
Red wavelengths will be around x…

Answer 15

Blue wavelengths will be around 5*10^-7 m

Red wavelengths will be around 7*10^-7 m

Question 16

Doppler effect.

Described as…

Answer 16

Described as an increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other

Question 17

Redshift.

As the source of light moves away, the wavelength will…

Answer 17

As the source of light moves away, the wavelength will increase, therefore the redshift occurs.

Question 18

Hubbles law.
Defined as the…
Equated as…

Answer 18

Defined as the speed of recession being proportionate to the distance away.
Equated as: v = H0*d
v being the speed of recession in km/s.
H0 being Hubbles constant. Equal to 70km/s/Mpc.
d being the distance away in Mpc.

Question 19

Rather than galaxies rushing away from Earth…

At very large distance from Earth, space will be…

Answer 19

Rather than galaxies rushing away from Earth, space itself is expanding.
At very large distance from Earth, space will be expanding faster than the speed of light.

Question 20

Curvature.
Positive curvature implies…
Negative curvature implies…
Zero curvature implies…

Answer 20

Positive curvature implies that there is enough matter in the universe to fold in on itself. Producing a closed universe.
Negative curvature implies that space curves outwards and can continue forever.
Zero curvature implies that expansion is sufficient to go on forever.

Question 21

Most of the mass in the universe is…

By nature, it is…

Answer 21

Most of the mass in the universe is dark matter.

By nature, it is very hard to detect.

Question 22

CMB stands for…
CMB has been travelling in space since…
CMB patterns have revealed that the universe is…

Answer 22

CMB stands for Cosmic Microwave Background radiation.
CMB has been travelling in space since the hot early universe.
CMB patterns have revealed that the universe is flat, zero curvature.

Question 23

Visible matter accounts for…
Dark matter accounts for…
Dark energy accounts for…

Answer 23

Visible matter accounts for 4% of the universes matter.
Dark matter accounts for 26% of the universes matter.
Dark energy accounts for 70% of the universes matter.

Question 24

Explain the cause of acceleration of expansion.

Answer 24

The decreasing effect of gravity with the expansion of the universe heightens the effect of dark energy, accelerating the process.