4.2 Galaxies Flashcards
Who is famous for classifying different types of galaxy?
Edwin Hubble
1920’s
Describe the 5 main types of galaxy.
Spiral (S) e.g. Andromeda Flattened disk-shaped Barred Spiral(Sb) Like Spiral Has 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’s a tuning fork diagram
Published Hubble’s book (Realm of the Nebulae)in 1936
Represents Hubble’s classification scheme.
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 M31 Largest in Local Group Large Magellanic Small Magellanic The Triangullum Galaxy M33 Spiral 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.
e.g. Virgo Cluster
2000 galaxies
Nearest grouping of galaxies to us
e.g. fornax Cluster and Coma Cluster
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’s an active galactic nucleus
Region in the centre of some galaxies emitting huge amounts of radiation.
Not just visible light
Radio, infra red,UV, X-rays, Gamma rays.
Supermassive black holes at their centre
Matter spiralling to black hole emits radiation
Name 4 types of Galaxy
Radio galaxies.
Seyfert galaxies. IR and X-Ray Quasars Quasi -Stellar Radio Source Compact Extremely bright One of brightest objects in universe Supermassive black hole at centre. One of the oldest objects in universe. High redshifts Discovered 1963 Blazars Emit strongly in all regions of the spectrum. Optical brightness can vary over 1 or 2 days.
