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Whirlpool Galaxy (M51, NGC 5194/5)
Alexis Bonnema

Whirlpool Galaxy

The Whirlpool Galaxy (M51 / NGC 5194) is a grand design spiral galaxy. Galaxies, including the Milky Way galaxy which we live in, contain clouds of dust and gas as well as stars and their solar systems; spiral galaxies are thought to have black holes at their centers.  The Whirlpool Galaxy was discovered in 1773 by Charles Messier, who did not at first realize there were two distinct objects; for this reason the designation M51 sometimes refers to the pair of galaxies and sometimes just to the larger one (the smaller one has the designation M51B.)  M51 was the first galaxy in which the spiral shape (for which spiral galaxies are named) was noticed, in 1845.  This is why the galaxy is also sometimes called Lord Rosse’s “Question Mark.”  Its two arms are very distinct, making it a “grand design” spiral galaxy.  The galaxy’s visibility and unique shape make it popular with amateur astronomers.

The Whirlpool Galaxy’s smaller companion galaxy, M51B / NGC 5195, almost seems like it is touching one arm of M51, but clearer pictures from the Hubble Space Telescope show that it is “passing behind“ it.  It is possible that the companion galaxy’s interaction causes the Whirlpool’s arms to be so defined.  As it moves past, it sends out waves that compress the galaxy’s gas clouds in some places, forming more clearly defined arms.  These arms contain new stars forming.  On one edge, they have clouds of dust and gas; in the reddish middle regions the new stars form. On the other edge are the resulting star clusters, which shine blue.

References:

Frommert, Hartmut and Christine Kronberg. “Messier Object 51.” Students for the Exploration and Development of Space.  http://messier.seds.org/m/m051.html

“Grand Design Spiral.” COSMOS - The SAO Encyclopedia of Astronomy. Swinburne University of Technology.  http://astronomy.swin.edu.au/cosmos/g/grand+design+spiral

Howell, Elizabeth. “Whirlpool Galaxy: Exploding with Supernovas.”  Space.com.  http://www.space.com/25506-whirlpool-galaxy.html

“Hubble Celebrates 15th Anniversary with Spectacular New Images.”    http://hubblesite.org/newscenter/archive/releases/2005/12/image/a/

“NED data for the Messier Objects.” Retrieved from Students for the Exploration and Development of Space.  http://messier.seds.org/xtra/supp/m_NED.html#m51

Redd, Nola Taylor. “Spiral Galaxy Facts and Definition.”  Space.com.  http://www.space.com/22382-spiral-galaxy.html

Wikipedia, "Spiral Galaxy".

Right Ascension (J2000) 13:29:52.6
Declination (J2000) +47:11:44.0
Filters used B (Blue), C (Clear), R (Red), V (Green)
Exposure x number of images for each filter B and R (90s x 8); V and C (90s x 7)
Image dimension 632x562 pixels; 13.8x12.3 arcminutes
Date/time observed March 03, 2016 11:12 UT
Distance 6.81 +- 0.04 Mpc (from NED radial velocity; distance is not well understood)
Scale 1980 pc/arcminute

 

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