VY Canis Majoris (VY CMa)
VY Canis Majoris (VY CMa) is a star in the constellation Canis Major, magnitude 7.9.
One of the largest stars known: a swollen red hypergiant that would engulf the orbit of Jupiter.
If VY Canis Majoris took the Sun’s place, its surface would stretch beyond the orbit of Jupiter. Light would need about six hours to travel once around it, against 14.5 seconds for the Sun. With a radius estimated at around 1,420 times the Sun’s — close to the limit of how large a cool star can grow — it is one of the largest stars known, and one of the most luminous in the Milky Way.
It is tearing itself apart. Strong convection and magnetic fields in its tenuous outer layers drive huge, randomly aimed outbursts — like the Sun’s coronal mass ejections, but far larger — that have flung arcs and knots of gas into a complex cloud around it within the last thousand years. In that cloud astronomers have found molecules ranging from titanium oxide to table salt.
Its history is full of illusions. Since 1847 observers have called it crimson, and in the 19th century they saw up to six ‘companions’ around it — now known to be bright patches in its surrounding nebula. It was also one of the first radio masers ever discovered.
VY Canis Majoris (VY CMa) is 3,800 light-years away: the light we see from it set off around 1780 BC, 450 years before Tutankhamun was buried in the Valley of the Kings.
Did you know?
- ‘Betelgeuse on steroids’. VY Canis Majoris has been described as ‘Betelgeuse on steroids’. Its closest analogue is NML Cygni, another extreme cool hypergiant, in Cygnus.
- Billions of Suns inside. At its estimated size, VY Canis Majoris has almost 3 billion times the Sun’s volume — yet only about 17 times its mass.
- Child of a stellar nursery. It sits at the tip of the glowing cloud Sh 2-310 and is thought to belong to the young star cluster NGC 2362.
A 7th- to 8th-magnitude orange-red point, about three degrees east of Wezen and just over a degree south-east of the little cluster NGC 2362 around Tau Canis Majoris. Its colour stands out in binoculars, but no telescope shows a disc.
When and where to see it
It is best placed in the evening sky around February, when it crosses the meridian at about 10 pm local time (around midnight in January). It can be seen from everywhere south of 64°N and never sets south of 64°S.
At its highest it stands 14° up from 50°N, 29° up from 35°N, 64° up from the equator, 81° up from 35°S.
Facts
- Type
- Star
- Constellation
- Canis Major
- Designations
- VY CMa, HD 58061, HIP 35793
- Magnitude
- 7.9
- Position
- RA 7h 23.0m, Dec −25° 46′ (J2000)
- Spectral type
- M5Iae
- Colour
- orange (B−V 1.38)
- Brightness
- varies from magnitude 6.5 to 9.6
- Distance
- 3,800 light-years
- Discovered
- Jérôme Lalande, 1801, First known record, as a 7th-magnitude star
Open AstroPilot to see when VY Canis Majoris (VY CMa) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.