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The Triangulum Galaxy taken from Al Sadeem Observatory taken on September 5, 2018 using Vixen ED115S refractor telescope and ZWO1600MC camera, 1 hour and 30 minutes total exposure time, stacked and post-processed in Pixinsight.


Messier 33, known as the Triangulum Galaxy, is a spiral galaxy situated between approximately 3 million light years away from Earth in the small constellation of Triangulum. It contains about 40 billion stars within 60,000 light-years diameter and weighs about 5 billion solar masses.

It was first discovered by Italian astronomer Giovanni Battista Hodierna back in 1654 when he noted the galaxy as a cloud-like nebulous or obscured object in his book “De systemate orbis cometici” (“About the systematics of the cometary orbit”).  The French astronomer and comet-hunter Charles Messier independently sighted the galaxy and catalogued on August 25, 1764.

About half the size as the Milky Way galaxy, it is the third largest galaxy in the Local Group. From observations of its composition and movement, astronomers thought that it may have interacted with Andromeda Galaxy in the past due to its proximity with each other in the night sky and the presence of neutral hydrogen streams linking the two galaxies. It exhibits a scattered distribution of hydrogen (H) II gas in its inner core and along its outer bands, suggesting an inside-out stellar formation within the galaxy. It also possesses the largest black hole M33 X-7 with a mass of about 85 solar masses; discovered in 2007.

H (Hydrogen) II gas distribution indicating active star formation in the inner core and outer armbands of the Triangulum Galaxy taken from the Dominion Radio Astrophysical Observatory (DRAO) Synthesis Telescope and Arecibo (Image Credit:

Having an apparent magnitude of +5.7, it can be viewed with the naked eye under extremely clear, dark skies. It is oriented face-on to us, having a low surface brightness which makes it faint when observed visually. Little light pollution could totally glare out the view.

In finding the Triangulum Galaxy, first spot the Andromeda Galaxy and draw a straight line towards the bright star Mirach and further straight in the general direction of the bright star Hamal (in Aries). The galaxy will appear as a faint smudge somewhere a third the distance between the two mentioned stars or Mothallah (slightly bright star in Triangulum). Long exposure photography with telescopes at least 4 inches will reveal its colorful armbands and coma-like center.

Location of Messier 33 in the Night Sky (Image Credit: EarthSky Via ESO Public Outreach)

REFERENCES (2014, March 25). Triangulum Galaxy – Messier 33 | Constellation Guide. [online] Available at:

McClure, B. and Byrd, D. (2017, November 22). Messier 33: 2nd-closest spiral galaxy | [online] Available at:

Tammy, P. (2017, January 30). Messier 33 – The Triangulum Galaxy – Universe Today. [online] Universe Today. Available at:

Triangulum Galaxy Facts • The Planets. (n.d.). Retrieved from

Wikipedia contributors. (2018, May 17). M33 X-7. In Wikipedia, The Free Encyclopedia. Retrieved from

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