Galaxies

Question 1

Who is famous for classifying different types of galaxy?

Answer 1

• Edwin Hubble - 1920′s

Question 2

Describe the 5 main types of galaxy.

Answer 2

• Spiral (S) Flattened disk-shaped (e.g. Andromeda) -Barred Spiral(Sb) Like Spiral with bright bar running through nucleus through which spiral arms appear. - Elliptical (E) Smooth Spheroid of stars Brightest at centre / Dimmest at edge. - Irregular (Irr) Has little structure or symmetry - Lenticular Class between Elliptical and Spiral

Question 3

What is a Tuning fork diagram?

Answer 3

-Published Hubble’s book (Realm of the Nebulae)in 1936 -Represents Hubble’s classification scheme.

Question 4

Draw a Tuning fork diagram.

Answer 4

Question 5

Give the classification of our own galaxy’s structure.

Answer 5

-Traditionally (Sb) -More evidence suggests a definite bar - Spiral Barred (SBb)

Question 6

What is the Local Group?

Answer 6

-Galaxies are groped together just like stars . -Our galaxy is grouped together with 50 others -This is the local groupOur Local Group has 5 neighbouring galaxies. 3Mpc across

Question 7

Name 6 galaxies in our Local Group.

Answer 7

-Andromeda (largest) -Large Magellanic -Small Magellanic -The Triangullum Galaxy -Pisces Dwarf -Aquarius Dwarf

Question 8

What is a cluster?

Answer 8

-Many local groups of galaxies can be found in gravitational agglomerations called clusters. -Often there is a giant elliptical galaxy at the centre of a cluster. (nearest is Virgo Cluster, 2000 galaxies)

Question 9

What is a super cluster?

Answer 9

• A group of clusters held together by gravity. - Our local group and cluster belong to the Virgo Supercluster Galaxy < Group < Cluster < SuperCluster < Universe

Question 10

What is an Active Galactic Nucleus?

Answer 10

-Region in the centre of some galaxies emitting huge amounts of radiation. (visible, radio, etc.) - Supermassive black holes at their centre. Matter spiralling to black hole emits radiation.

Question 11

Name 4 types of active galaxy

Answer 11

• Radio galaxies. - Seyfert galaxies. (IR and X-Ray) - Quasars (very massive, remote and bright. black hole at the center) - Blaxars (very compact quasar)