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 The Andromeda Galaxy
 (M31 or NGC 224)
The Andromeda galaxy harbors
about  500 000 000 000  stars.

Final Answers
© 2000-2020   Gérard P. Michon, Ph.D.

Galaxies

 Michon
 
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Related articles:

Related Links (Outside this Site)

An Atlas of the Universe  by  Richard Powell
FAQs about Galaxies  (The Astronomy Café)  by  Sten Odenwald
The Structure of the Universe  (OpenCourse, Introduction to Astronomy #35)
The Milky Way  by Jim Kaler.   |   Center for Astrophysics  (CfA)
 
Wikipedia :   Galaxy  |  Milky Way  |  Local Group  |  Virgo Supercluster  |  List of nearest galaxies  |  List of Galaxies
Galaxy Morphological Classification  |  Hubble sequence  |  Galaxy color-magnitude diagram  |  Dark galaxy

Videos

Powers of Ten :  The classic short film  (9 min)  rereleased in 1977.
The definitive guide to the Milky Way galaxy   National Geographic Channel.
Monster of the Milky Way   BBC Nova   (Eric Becklin & Andrea Ghez, UCLA).
 
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 International Year 
 of Astronomy (2009)

Galaxies and the
Fabric of the Universe

 The Andromeda Galaxy
 (M31 or NGC 224)

 The Milky Way   Pierre Mechain
1744-1804 (2012-07-14)   The Milky Way
The name of  our own  galaxy.

The Milky Way  (latin: Via Lactea)  is the dim stripe of nebulous light which can be seen on a clear night in the direction of Sagittarius.  It's a fabulous side view of the disk-shaped system that includes our Sun and billions of other stars like it.  In modern times, a huge number of such systems were discovered.

The Milky Way is significantly larger than early estimates had indicated.  In December 2012, it was deduced from years of observations by the  Hubble Soace Telescope  that the neighbohring dwarf galaxy known as  Leo 1  is in orbit around the center of the Milky way at a speed comparable to our Sun's own orbital speed.

To create the corresponding gravitational pull, the total mass of the Milky Way ought to be  1.6 trillion solar masses or so  (counting everything, dark matter spherical halo and all, at a lesser distant from the galactic center than Leo 1 itself).

The definitive guide to the milky way galaxy  NASA, JPL, National Geographic Chanel.
Space Fan News #84  by  Tony Darnell   (2012-12-04).
Wikipedia :   Galaxy rotation curve


(2012-07-14)   The Local Group of Galaxies

The Andromeda Galaxy and the Milky Way dominate our local cluster.

 The Pinwheel Galaxy in Triangulum 
 (M33 or NGC 598) may contain 
 about 40 000 000 000 stars.
M33:  The Pinwheel Galaxy in Triangulum
(NGC 598) has about 40 000 000 000 stars
  The third largest member of the local group is the Pinwheel Galaxy  (located in the Triangulum constellation).  It contains about 40 billion stars and is thus only about one tenth the size of either the Andromeda Galaxy or the Milky way...

 Come back later, we're
 still working on this one...

The Universe within 5 million Light-Years: The Local Group of Galaxies   |  Virgo Supercluster
 
The Andromeda-Milky Way Collision (12:01)  by  Matt O'Dowd   (PBS Space Time, 2018-03-28).


(2012-07-14)   The Virgo Cluster

The dominant structure in our corner of the Universe.

 Come back later, we're
 still working on this one...

Wikipedia :   Virgo Cluster   |  List of galaxy clusters


(2012-07-14)   Superclusters:  The largest objects in the Universe

The Virgo cluster is part of the Virgo supercluster.

 Come back later, we're
 still working on this one...

The Universe within 100 million light-years: The Virgo Supercluster  |  Virgo Supercluster


(2019-07-31)   Spiral Galaxies
Natural shape of young galaxies,  before they collide with each other.

 Come back later, we're
 still working on this one...

How do we know the Milky Way is a spiral? (16:37)  by  Becky Smethurst  (2019-06-12).


(2019-07-31)   Ring Galaxies
rare  type of galaxies.

 Come back later, we're
 still working on this one...

Hoag's Object (14:49)  by  Becky Smethurst  (2018-11-14).
The Cartwheel Galaxy (13:59)  by  Becky Smethurst  (2019-07-31).


(2012-09-21)   Elliptical galaxies may just be mature merger remnants.
The largest elliptical galaxy we know is  IC 1101.

IC 1101  is a  giant  elliptical galaxy,  about one billion light-years away.

 Come back later, we're
 still working on this one...

The Largest Galaxy in the Universe: IC 1101 (5:39)  by  Tony Darnell   (2012-09-21)
 
Wikipedia :   IC 1101   |   Abell 2029


(2017-09-06)   Supermassive Black Holes
They are located at the center of almost every galaxy.

 Come back later, we're
 still working on this one...

Supermassive Black Holes (10:08)  with  Michael Merrifield, Meghan Gray & Omar Almaini  (2016-04-10).
Supermassive Black Holes or Their Galaxies.  Which Came First? (11:06)  by  Fraser Cain  (2017-09-05).
History of galactical black holes (25:48)  by  Becky Smethurst  (2019-01-16).
 
Wikipedia :   IC 1101   |   Abell 2029

Richard Brent Tully
R. Brent Tully

(2020-04-08)   Tully-Fisher Relation  (TFR, 1977)
Empirical relation between the luminosity of a spiral galaxy and its asymptotic rotational velocity.

The rotation velocity of a galaxy is directly observed as the width of emission lines in its spectrum.

 Come back later, we're
 still working on this one...

Tully-Fisher relation (1977)   |   R. Brent Tully (1943-)   |   Rick Fisher (1943-)

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