VY Canis Majoris
|VY Canis Majoris is about 1,000 times
wider than the Sun, making it one of the largest stars known
A red hypergiant star that is one of
the largest and most luminous known stars in the Milky Way Galaxy. VY Canis
Majoris, an irregular pulsating variable, lies about 5,000 light-years away
in the constellation Canis Major.
|VY Canis Majoris. Material ejected
by the star is visible in this 2004 image captured by the Hubble Space
Telescope's Advanced Camera for Surveys, using polarizing filters.
Credit: NASA/ESA/R Humphreys/U Minnesota)
Although VY Can is about half a million times as luminous as the Sun, much
of its visible light is absorbed by a large, asymmetric cloud of dust particles
that has been ejected from the star in various outbursts over the past 1,000
years or so. The infrared emission from this dust cloud makes VY Can one
of the brightest objects in the sky at wavelengths of 5–20 microns.
In 2007, a team of astronomers using the 10-meter radio dish on Mount Graham,
in Arizona, found that VY Can's extended circumstellar cloud is a prolific
molecule-making factory. Among the radio emissions identified were those
of hydrogen cyanide (HCN), silicon monoxide (SiO), sodium chloride (NaCl)
and a molecule, phosphorus nitride (PN), in which a phosphorus
atom and a nitrogen atom are bound together. Phosphorus-bearing molecules
are of particular interest to astrobiologists because phosphorus is relatively
rare in the universe, yet it is a key ingredient in molecules that are central
to life as we know it, including the nuclei acids DNA and RNA and the energy-storage
||5,000 light-years (1,500 pc)
||R.A. 07h 22m 59s,
Dec. -25° 46' 02"
||HD 58061, HIP 35793
|Jets of molecules, indicated by red and blue arrows,
flow from VY Canis Majoris photographed by the Hubble Space Telescope.
The blue arrow (lower right) shows the slight deviation of the "squirt"
flow from the direction towards us. The curved nebulous tail (CNT)
and red arrow (upper right) show the fan of material flowing away
from us and to the side. The white arrows and transparent circle show
the general spherical flow of matter outward. Credit: UA Steward Observatory
Herschel spectroscopic analysis
Among the first results of the Herschel
Space Observatory, in November 2009, was a detailed spectrum of the
cloud of gas swirling away from VY Canis Majoris obtained by the SPIRE instrument.
This revealed copious amounts of water and carbon monoxide together with
the spectral signatures of more than 30 other molecules (see below).