View
29
Download
0
Category
Preview:
DESCRIPTION
Hubble Science Briefing. Discovering galaxies Bursting through the limits of space and time. Jean-René Roy Space Telescope Science Institute. 5 July, 2012. 2. The key ideas. Many people “ discovered ” galaxies Many people found the distances to galaxies - PowerPoint PPT Presentation
Citation preview
Discovering galaxies
Bursting through the limits of space and time
Jean-René RoySpace Telescope Science Institute
Hubble Science Briefing
5 July, 20125 July, 2012
22
The key ideas
•Many people “discovered” galaxies
•Many people found the distances to galaxies
•A few people found that the universe was expanding and accelerating
•Establishing priority is a complex exercise
•The discovery of the “sidereal universe” is a fascinating story of humankind curiosity, astuteness and ingenuity
33
44
55
How were galaxies discovered?
66
Pre-history
• Abd al-Rahman ibn Umar al-Sufi (903 - 986) refers to a “small cloud” in Andromeda
• Book of the constellations of the fixed stars in year 964
Al-Sufi (903-986)
77
The Herschels - William (1738-1822), Caroline (1750-1848) & John (1792-1871)
88
While William Herschel is surveying the sky for binary stars, his sister searches for new comets.
With her comet finder, Caroline discovers several new “nebulae”
William switches his program to the “study of the sidereal Universe”
99
.... the naked eye, which, as we have before estimated,
can only see the stars of the seventh magnitude so as to distinguish them; but it is nevertheless very evident that the united lustre of
millions of stars, such as I suppose the nebula in
Andromeda to be, will reach our sight in the shape of a
very small, faint nebulosity; since the nebula which I
speak may easily be seen in a fine evening.
William Herschel,
Construction of the Heavens, 1785 1010
Immanuel Kant 1724 - 1804“I easily persuaded myself
that these stars can be nothing else than a mass of
many fixed stars... On account of their feeble
light, they are removed to an inconceivable distance from
us.” (1755)
“Island Universes”
1111
William Parsons, 3rd Earl of Rosse (1800-1867)
Birr Castle, Ireland
72-inch Leviathan72-inch Leviathan
1212
1313
Whirlpool Galaxy (M51 or NGC 5194/95)
Leviathan HST
1414
How far away? How we found out
1515
Extragalactic Renaissance
• Opinions change dramatically between 1900 and 1920
• Opposing views for “in” (Shapley/van Maanen) and for “out” (Curtis, Lundmark, Öpik, Hubble)
• Strong observational evidence builds up quickly for most nebulae to be “extragalactic”
• Several new technologies provide the key tools
1616
Isaac Roberts introduces astrophotography for nebular
work
1829-1904
Roberts took this first photograph of the Andromeda galaxy on December 29, 1888
Roberts observatory, Crowborough - Sussex
1717
New technologies: sturdy metal mount, precision motor drive, glass mirror 1818
Shapley: The Milky Way is big (300,000 l-y) and is everything = the universe, but ...
Harlow Shapley (1885-1972)
1919
Novae!
~24 novae/yr are observed every yearin the Andromeda galaxy
2020
Knut Lundmark (1889-1958)Heber Curtis (1872-1942)
In 1917, novae in the Andromeda “nebula”:they are located at 650,000 light-years =
well outside the Milky Way2121
Vesto Slipher (1875-1969)
2222
Ernst Öpik (1893-1985)In 1922, Ernst Öpik uses
stellar orbital velocity and starlight density of
Andromeda:
Distance = 1,440,000 l-yMass = 4.5 billions “suns” 2323
“Cracking the nut” of galaxies
2424
Text
Henrietta Leavitt and a new class of
variable stars: Cepheids
1868-1921
2525
N not a nova it is a
variableCepheid
Andromeda Galaxy, M31 by Edwin Hubble
Edwin Hubble (1889-1953)Edwin Hubble (1889-1953)
“The spiral is 7.25 times as far away as the Cloud, or about 680,000 l-y.”
2626
Corcoran Hall, George Washington University, DC
American Astronomical Society 1st Jan 1925“Cepheids in Spiral Nebulae”, Edwin Hubble
2727
... there is the shadow of Adriaan van Maanen
1894-1946
M 332828
Edwin Hubble
2929
How was the expansion of the universe found?
3030
The expanding universe
Albert Einstein (1879-1955)
Text
General Relativity: A theory of space-time and gravitation 3131
Alexander Friedman (1888-1925)
Georges Lemaître (1894-1966)
Slipher Humason Hubble
3232
Lundmark (1889-1958)
1924: First “distance-velocity diagram” by Knut Lundmark
3333
Edwin Hubble
Milton Humason
3434
The “Hubble law” of 1929
v = H0 d
v = recessional velocityH0 = Hubble constant
d = distance
H0 = 72 km/sec per megaparsec or 20 km/sec per million light-years
3535
H. Nussbaumer and L. Bieri (2011) write that Hubble was very dubious that the recessional velocities represented the expansion of the universe: “Actually Hubble never believed in such a thing.”
3636
The evolving universe
As we go back into the early history of the universe, we see a different universe
•Stars are forming at a much higher rate
•This rate is changing rapidly over the first Gyrs (1 Gyr = 109 years)
•Galaxies are merging at a higher rate
•Galaxy morphology is different
3737
The universe was condensed in a “fireball” of space-time 13.7 billion years ago
3838
Georges Lemaître
40 rue de NamurLouvain
Georges Lemaître
40 rue de NamurLouvain
3939
Hubble Deep Fields
Galaxy cluster Abell 2744 ~3.5 Giga-ly
More distant field
4040
4141
The world of galaxies is much more varied and strange than inferred by Hubble’s elegant scheme.
4242
Movie Credits: Frank Summers (STScI), Chris Mihos (Case Western Reserve Univ.) & Lars Hernquist (Harvard)
Download movie here: http://hubblesite.org/newscenter/archive/releases/2008/16/video/d/
“Cosmic Collisions”A Computer Simulation of Galaxies
Colliding
4343
4444
Adam Riess
Brian Schmidt
Albert EinsteinSaul Perlmutter
Signatures of dark energy and of dark matter
2011 Physics Nobel
4545
In the last 100 years, the volume of the
observed universe has been multiplied by
1015 times, or “one million billion times
! ”4646
4747
4848
4949
5050
200 billion galaxies in the200 billion galaxies in theobservable universe, each with observable universe, each with
about 100 billion stars like the sunabout 100 billion stars like the sun
20,000,000,000,000,000,000,00020,000,000,000,000,000,000,000 stars stars
5151
5252
5353
The Suomi NPP Blue Marble, Credit:NASA/NOAA
5454
Discovering galaxies: some references
• The Realm of the Nebulae, Edwin Hubble, Yale University Press, 1936
• Man Discovers the Galaxies, R. Berendzen, Richard Hart & Daniel Seeley, Science History Publications, 1976
• The Day We Found the Universe, Marcia Bartusiak, Pantheon Books, 2009
• Discovering the Expanding Universe, H. Nussbaumer & L. Bieri, Cambridge University Press, 2009
• http://en.wikipedia.org/wiki/Galaxy
5555
Images from
•NASA and ESA
•Space Telescope Science Institute
•Gemini Observatory
•Canada France Hawaii Telescope
•Peabody Library, Johns Hopkins University
•Wikipedia Commons
5656
Acknowledgments
•Zoltan Levay, STScI
•Carolyn Slivinski, STScI
•Frank Summers, STScI
•Paul Espinoza, JHU Peabody Library
5757
Thank you5858
Recommended