Messier 83: The Southern Pinwheel Galaxy in Hydra

Messier 83, usually shortened to M83, is a barred spiral galaxy in Hydra, near the border with Centaurus. It also goes by NGC 5236 and the Southern Pinwheel Galaxy, and it's the southernmost galaxy in Messier's catalogue.

It sits roughly 15 million light-years away and ranks among the brightest spiral galaxies in the night sky. Binoculars under a dark sky show it as a small, hazy smudge, and June is the easiest month to try.

What Kind of Galaxy Messier 83 Is

What is Messier 83?

Messier 83 is a barred spiral galaxy in Hydra, near the Centaurus border, about 15 million light-years from Earth. The bar is faint, and the whole structure reads as a grand-design spiral: a few long, well-defined arms instead of ragged stubs.

Astronomers classify it as SAB(s)c. The code breaks into three parts: SAB for a bar that exists but doesn't dominate, (s) for pure spiral arms with no ring around the core, and c for loosely wound arms.

One description puts the galaxy midway between a normal spiral and a barred one, which is what a weak bar looks like in practice.

Names, Catalog Designations and the Southern Pinwheel Nickname

Messier 83, M83 and NGC 5236 all point to the same galaxy. The Southern Pinwheel nickname comes from its resemblance to the Pinwheel Galaxy, M101, and a later electronic band borrowed the galaxy's name for itself.

Why is M83 called M83?

M83 is a Messier catalogue designation rather than a description. Charles Messier added the galaxy to his catalogue of nebulous objects in 1781, and it has carried the number 83 since. Nebulous meant soft and cloudy through a telescope, not a sharp point of light.

Discovery at the Cape of Good Hope

Nicolas-Louis de Lacaille discovered M83 in 1752 from the Cape of Good Hope. It's sometimes credited as the first galaxy found beyond the Local Group, the small family of galaxies that contains our own, and the third galaxy overall after M31 and M32.

How Big and How Bright Messier 83 Is

A Diameter of 118,000 Light-Years

Astronomers give its isophotal diameter, the width measured out to a fixed level of faintness, as about 36.24 kiloparsecs. A parsec is about 3.26 light-years, so that diameter works out to roughly 118,000 light-years.

On the sky, the galaxy spans about 11 by 10 arcminutes. One arcminute is a sixtieth of a degree, so the whole galaxy covers a modest patch of sky.

Magnitude 7.5 and What Binoculars Show

Its apparent magnitude is 7.5. That places the galaxy among the brightest spirals in the night sky and makes it a binocular target rather than a naked-eye one.

Star Formation, Supernovae and Stellar Bubbles

Much of what you see in photographs of M83 comes from what the galaxy's gas is doing right now. The colors in those images carry information.

Dust Lanes, Young Clusters and the Pink Glow

New stars form in clusters along the edges of dark, spiraling dust lanes. Those clusters are only a few million years old, and they pour out large amounts of ultraviolet light.

Surrounding diffuse gas absorbs that light and glows pink in response. That pink is the hydrogen emission visible in color images of the arms.

Red Knots, Blue Regions and the Outer Disk

Red knots in those images trace diffuse gaseous nebulae where star formation is underway and very hot young stars are exciting the gas. Blue regions mark young stellar populations formed within millions to tens of millions of years.

Star formation concentrates along the leading edge of the spiral arms. That pattern fits density wave theory, in which the arms behave as waves that compress gas as it orbits through them.

NASA's Galaxy Evolution Explorer reported large numbers of new stars about 20 kiloparsecs from the center, in outer reaches where star formation had been thought impossible.

Six Supernovae, Including a Prototype

A supernova marks the explosive end of a star's life, and six have been observed in M83: SN 1923A, SN 1945B, SN 1950B, SN 1957D, SN 1968L and SN 1983N.

SN 1983N stands out. Robert Evans found it from Australia on 3 July 1983, and it became the first Type I supernova detected through radio emission.

It also became the prototype for hydrogen-deficient Type Ib supernovae, with a Wolf-Rayet star inferred as the one that exploded.

Bubbles Carved by Nearly 300 Supernovas

Hubble imaging revealed interstellar bubbles, cavities blown into the surrounding gas, produced by nearly 300 supernovas across the galaxy.

Those hollows help astronomers work out which stars exploded and how they spread nuclear-processed elements through the galaxy.

M83's Neighbors and Galaxy Group

M83 sits at the center of one of two subgroups inside the Centaurus A/M83 Group. Centaurus A anchors the other subgroup.

One Group or Two?

Whether that arrangement counts as one group or two is still unsettled. The two subgroups sit physically close and appear not to be moving relative to each other.

NGC 5253 and a Past Encounter

The dwarf galaxy NGC 5253, classified as peculiar, lies near M83. The two likely interacted within the last billion years, triggering bursts of rapid star formation in the central regions of both.

Seeing Messier 83

The physics explains the galaxy's appearance. The practical part is shorter: a dark sky, a low southern horizon and stars you can identify first.

Both routes below begin with stars you need to recognize first. The Constellation guide covers Hydra and Centaurus if either pattern is new to you.

When to Look, and What Binoculars Show

June is the easiest month for M83. Binoculars reveal it as a soft, small glow rather than a defined spiral.

From mid-northern latitudes the galaxy is difficult to see. Messier observed it from Paris at about 49 degrees north and said it could only be seen with the greatest concentration.

The northern limit of good observation is sometimes placed near the 45th parallel north. Farther south, the galaxy climbs higher and is far more forgiving.

Observing conditions decide whether the trip is worth it, so check cloud cover and moonlight before you set up.

For a galaxy this spread out, sky darkness matters. A Light pollution map shows how dark your nearest site really is.

Star-Hopping from Hydra

Start with Gamma Hydrae or Pi Hydrae, the two landmarks that bracket the galaxy. From Gamma Hydrae, M83 lies about 6.5 degrees north and 3 degrees 15 minutes west.

From Pi Hydrae, the offsets run about 3 degrees 15 minutes south and 6 degrees 20 minutes west. A trail of 5th- to 7th-magnitude stars covers the rest.

It ends at a yellowish star of magnitude 5.83 and a fainter one of magnitude 7.0, about 30 arcminutes northeast of the galaxy.

If the trail is hard to follow, a Bright stars reference confirms you're starting from the right star.

Star-Hopping from Centaurus

Southern observers have a second route. Start at Iota and Theta Centauri, then look between them for four stars of magnitudes 4 to 5, labeled i, h, k and g Centauri.

Some charts number those same stars instead: i Cen as 1, g Cen as 2, k Cen as 3 and h Cen as 4.

The pair g and i points toward M83 and onward to Gamma Hydrae, which gives you a line to follow rather than a single jump.

What Remains Uncertain at the Center

For all the activity in the arms, the center of the galaxy has been harder to pin down. In April 2025, astronomers published the first clues pointing to a possible supermassive black hole there.

The evidence came from the James Webb Space Telescope's MIRI instrument, which detected highly ionized neon gas. That signal could be the signature of an active galactic nucleus, the luminous core of a galaxy whose central black hole is drawing in material.

That's a lead rather than a conclusion: the neon detection points to a possible active nucleus, not a confirmed black hole.

If the neon signal holds up, that small smudge in a pair of binoculars marks the outer face of a galaxy with a feeding black hole at its heart.