The sky around Leo Triplet at true scale, north up and east left, with stars to magnitude 8. The circles show the field of a low-power eyepiece and of 10×50 binoculars.
Leo Triplet is a barred spiral galaxy in Leo, 37 million light-years away
Leo Triplet (M66, NGC 3627, Arp 16, PGC 034695, UGC 06346) is a barred spiral galaxy in the constellation Leo, 37 million light-years away. It shines at magnitude 8.9 and spans 9.1′ × 4.2′ of sky, about 97,700 light-years across. It is an easy target in binoculars, and it is highest in the evening sky in April.
Galaxy: a system of billions of stars, gas and dust held together by gravity, far outside the Milky Way. Spiral galaxies have a disk with arms; elliptical galaxies are smooth, round or oval swarms of older stars.
Leo Triplet is Arp 16, one of Arp's spiral galaxies with detached segments
Halton Arp photographed it for his Atlas of Peculiar Galaxies (1966) as field Arp 16. It is in his group of spiral galaxies, Arp 1 to 101, under the category Spiral galaxies with detached segments.
Leo Triplet lies 2.8° southeast of Chertan, the magnitude 3.3 star. Three fingers held at arm's length cover about 5°.
Leo Triplet is highest in the evening in April
The chart gives its height above the horizon at 9 pm through the year, from 60°N to 40°S. It can be seen from the whole northern hemisphere and south to about 77°S, and never sets north of 77°N.
Leo Triplet is 37 million light-years away
The light seen from Leo Triplet tonight left it about 37 million years ago, long before modern humans existed. It ranks 89 of 109 by distance among the 110 Messier objects. Distance source: TRGB, Anand 2021.
