Triangulum Galaxy Alex Roberson

Location 3 million light years from earth Located in Triangulum constellation

Name Catalogued as Messier 33 or NGC 598 Sometimes called the Pinwheel Galaxy; a nickname shared with Messier 101

Visibility Under good conditions, it can be seen with the naked eye. It is one of the farthest galaxies that can be seen with the naked eye.

Discovery Most likely discovered by Giovanni Battista Hodierna before 1654 In his work De systemate orbis cometici; deque admirandis coeli caracteribus he described it as a cloud-like nebula or obsuration and gave the description, "near the Triangle hinc inde".

Second discovery It was discovered again by Charles Messier. He listed it in his book Catalog of Nebulae and Star Clusters as number 33.

Properties It has a diameter of about 50,000 lightyears It is the third largest member of the Local Group It may be gravitationally bound to the Andromeda galaxy

Local Group The local group consists of around 30 galaxies. Its gravitational center is somewhere near the Milky Way and the Andromeda Galaxy.

Stars It contains about 40 billion stars The Milky Way contains around 400 billion The Andromeda Galaxy has over 1 trillion

The Disk The disk of Triangulum has an estimated (3-6) × 10^9 solar masses Its gas is around 3.2 x 10^9 Combined mass of everything in the galaxy is 10^9

Distance Three techniques have been used to measure distances to M 33. Using the Cepheid variable method, an estimate of 2,770 ± 130 kly (850 ± 40 kpc) was reached. The Tip of the Red Giant Branch (TRGB) method was used to derive a distance estimate of 2,590 ± 80 kilolight-years (790 ± 25 kpc).

Structure In astronomer Gérard de Vaucouleurs' revised Hubble Sandage system of galaxy morphological classification, the Triangulum galaxy is classified as type SA(s)cd. The S basically means it is a spiral galaxy The A means “ the galactic nucleus lacks a bar-shaped structure”. Astronomer Allan Sandage's "(s)" is used when the spiral arms emerge directly from the nucleus or central bar. The cd means it has loosely wound arms.

Inclination It has an inclination of 54° when viewed from the Earth. This allows it to be viewed without much obstruction from gas and dust.

Star formation It has a higher rate of star formation than the Andromeda Galaxy. The rate of star formation is about 3.4 Gyr^−1 pc^−2 This is about 0.45 ± 0.1 solar masses per year

Star Formation History Due to differing gradients, there is a different star formation history between the inner and outer disks. This occurs when gas is accumulated at large radii later in a galaxy's life span, while the gas at the core becomes depleted. The result is a decrease in the average age of stars with increasing radius from the galaxy core

Discrete Features A total of 515 discrete candidate sources of 24 μm emissions have been discovered as of 2007. The brightest of them lie within the central region of the galaxy. Many of these are associated with HII regions. The four brightest are NGC 588, NGC 592, NGC 595 and NGC 604.

Sources Wikipedia