The Formation of Galaxies
First Presentation:
The Hubble Sequence
Bruno Berwanger
Remco van der Burg
Short Preview
► Edwin
Hubble
► The Hooker Telescope
► What is the Hubble Sequence?
► Differences between known galaxy types
► Examples
► Summary
Edwin Hubble (1889-1953)
► State
Record high jump 1906
► Served in both WWI and WWII
► 1919 A.D. Observations with Hooker
Telescope
► 1953 Nobel prize
The Hooker Telescope
► Built
in 1908
► Location: northeast of Los
Angeles
► Mountain of 1742 meter
high
► Resolving Power: 0.05”
Tuning Fork Diagram
Elliptical Galaxies (E0-E7)
► Degree
of eccentricity
► Mostly consists of old stars
► Population II stars
► Low in gas and dust
► Physical Properties enormous
range
Examples
NGC 4623 – E7
NGC 4365 – E3
Spiral Galaxies (Sa – Sd)
► Central
bulge
► Outlying disk containing spiral arms
► Plenty of gas and dust
► Old and young stars
► Sa tightly wound + big central bulge
► Sd very loose spirals + small central bulge
Spiral
NGC 4448 - Sa
NGC 5457 - Sc
Barred Spiral Galaxies
(SBa-SBd)
► Spirals
running from a bar
► Plenty of gas and dust
► Old and young stars
► Bars temporary?
Examples
NGC 253 - SBc
NGC 1300 - SBc
Lenticular Galaxies (S0, SB0, E8)
► Intermediate
between
Elliptical and Spirals in:
ƒ
ƒ
ƒ
Composition
Age of stars
Shape
NGC 4649 – E8
NGC 4684 – S0
Irregular Galaxies (Irr I, Irr II)
► Do
not fit in the Hubble Classification
► Irr I
ƒ Deformed Galaxies
ƒ Sometimes remnants can be seen
► Irr
ƒ
ƒ
ƒ
II
Completely Chaotic in form
Mostly Young stars
Will later take one of the regular shapes
Examples
Large Magellanic Cloud – Irr I
Irr II
Visible Galaxies
► All
ƒ
ƒ
ƒ
visible Galaxies:
77% Spirals
20% Elliptical
3% Irregular
► Within
ƒ
ƒ
ƒ
9 Mpc from here:
33% Spirals
13% Elliptical
54% Irregular
Some facts
Ellipticals
Spirals
Irregulars
m sun
105 to 1013
109 to 1011
108 to 1010
Abs Mag
-9 to -23
-15 to -21
-13 to -18
Diameter (kpc) 1 to 200
5 to 50
1 to 10
Spectral Type K
F to K
A to F
Summary
► The
Hubble sequence is a usefull tool for
the classification of galaxies:
ƒ
ƒ
ƒ
ƒ
Elliptical Galaxies
(Barred)Spiral Galaxies
Lenticular Galaxies
Irregular Galaxies
The End