Alex Roberson

Triangulum Galaxy

3 million light years from earthLocated in Triangulum constellation

Location

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

Name

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.

Visibility

Most likely discovered by Giovanni Battista Hodierna before 1654In 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".

Discovery

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

Second discovery

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

Properties

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

Local Group

It contains about 40 billion starsThe Milky Way contains around 400 billionThe Andromeda Galaxy has over 1 trillion

Stars

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

The Disk

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).

Distance

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 galaxyThe 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.

Structure

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

Inclination

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

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

Star Formation History

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.

Discrete Features

Wikipedia

Sources