Galaxies Flashcards
Who is famous for classifying different types of galaxy?
- Edwin Hubble - 1920′s
Describe the 5 main types of galaxy.
- 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
What is a Tuning fork diagram?
-Published Hubble’s book (Realm of the Nebulae)in 1936 -Represents Hubble’s classification scheme.
Draw a Tuning fork diagram.
Give the classification of our own galaxy’s structure.
-Traditionally (Sb) -More evidence suggests a definite bar - Spiral Barred (SBb)
What is the Local Group?
-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
Name 6 galaxies in our Local Group.
-Andromeda (largest) -Large Magellanic -Small Magellanic -The Triangullum Galaxy -Pisces Dwarf -Aquarius Dwarf
What is a cluster?
-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)
What is a super cluster?
- A group of clusters held together by gravity. - Our local group and cluster belong to the Virgo Supercluster Galaxy < Group < Cluster < SuperCluster < Universe
What is an Active Galactic Nucleus?
-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.
Name 4 types of active galaxy
- Radio galaxies. - Seyfert galaxies. (IR and X-Ray) - Quasars (very massive, remote and bright. black hole at the center) - Blaxars (very compact quasar)
