Whirlpool Galaxy
What is Whirlpool Galaxy?
Galaxies· Distance ~23 million ly. The textbook spiral. Seen face-on, its perfect whirlpool arms end at a small companion galaxy whose collision has sharpened the spiral pattern. In 1845 Lord Rosse sketched its spiral structure — the first ever recognised in any galaxy.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Whirlpool Galaxy is in your sky right now: https://nowsky.org/solar/sky?sel=whirlpool galaxy — location and time set automatically, no login.
Its place in the sky
A galaxy, in the direction of Canes Venatici, spanning about 11 arcminutes of sky — 0.4 times the width of the full Moon.
Distance and scale
| Distance | ~23 million ly |
|---|---|
| Diameter | ~76,000 ly |
| Companion | NGC 5195, hanging off one arm |
| Constellation | Canes Venatici |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
In 1845 Lord Rosse sketched its arms with his giant "Leviathan" — the first spiral structure ever seen.
Frequently asked
- How far is Whirlpool Galaxy from Earth?
- ~23 million ly.
- How big is Whirlpool Galaxy?
- ~76,000 ly.
- Where in the sky is Whirlpool Galaxy?
- In the direction of Canes Venatici.
- Where is Whirlpool Galaxy in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
Three supernovae in M51 — 1994, 2005, 2011
The Whirlpool is known as a galaxy where supernovae are frequent — 1994, 2005 and 2011, three in seventeen years, several times the average of one or two a century for a single galaxy. The collision with its companion NGC 5195 drives star formation, so massive stars are plentiful and so are the short lives ending in explosion. SN 2011dh was found first by an amateur, and because Hubble had photographed the site beforehand the star that exploded could be traced.
It was a yellow supergiant, neither the red supergiant nor the blue star that supernova theory expected, and the case was argued over. The explanation offered was a star whose outer layers had been stolen by a companion, leaving it at an intermediate temperature, and after the explosion that companion was detected in ultraviolet light. At 23 million light-years these supernovae were never naked-eye objects, but small telescopes caught them as new points on the galaxy's arms.
The galaxy in depth
The Whirlpool Galaxy, M51, is a spiral about 23 million light-years away in Canes Venatici. At roughly 76,000 light-years across it is slightly smaller than the Milky Way, but its face-on disc shows two bold arms as crisply as a diagram. A small irregular galaxy, NGC 5195, clings to the end of one arm; its passage through M51's disc over hundreds of millions of years appears to have sculpted the striking spiral pattern.
Messier found it in 1773, and in 1845 the Earl of Rosse in Ireland, using the then-largest 1.8-metre reflector, was the first to recognise and sketch a spiral form — the first spiral structure ever seen in any galaxy. Hubble and Webb images show star-forming regions strung along the arms like beads, making M51 the standard case for studying how density waves trigger star birth. Three supernovae have been seen here in recent decades.
Find it just south-west of Alkaid at the end of the Big Dipper's handle. Select the Whirlpool in the Sky view to mark its direction; in dark skies binoculars show the two galactic cores side by side, and a medium telescope hints at the arms.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.