Enormous Aging Star’s Incredible, Successful New Diet

VY Canis Majoris is an enormous red hypergiant star that sends forth its magnificent and brilliant light from where it dwells in the constellation Canis Major (The Great Dog) in the southern celestial hemisphere. One of the largest stars known–indeed, at one time the largest star known–it is one of the most luminous of its type. In November 2015, a team of astronomers using the European Southern Observatory’s (ESO’s) Very Large Telescope (VLT), announced that they have obtained the most detailed images yet of this brilliant stellar giant. These observations reveal how the surprisingly large size of the grains of dust encircling this hefty star help it to shed mass as it begins to die. This mysterious process, understood now for the first time, is necessary to prepare such giant stars for their final farewell performance to the Universe in the explosive, incandescent rage of a supernova blast.

VY Canis Majoris is a gigantic denizen of our Milky Way Galaxy. It is 30 to 40 times the mass of our own Star, the Sun, and 300,000 times more luminous. Indeed, if this gigantic star were to replace our own Sun at the center of our Solar System, it would reach all the way out to the orbit of Jupiter, after having bloated tremendously as it entered its death throes during the final stages of its stellar life. Although there is still considerable variation in estimates of its radius, this elderly stellar behemoth boasts an estimated radius of approximately 1,420 plus or minus 120 solar radii–equivalent to a diameter of 13.2 astronomical units (AU), or about 1,976,640,000 kilometers. It is located about 3,900 light-years from Earth. One AU is equal to Earth’s average distance from our Sun, which is about 93,000,000 miles.

Lonely, solitary, and burning brightly with its doomed and dying stellar fires, VY Canis Majoris is categorized as a semiregular variable star with an estimated period of 2,000 days.

The first known observation of VY Canis Majoris is recorded in the star catalogue of the French astronomer, freemason and writer Jerome Lalande (1732-1807) on March 7, 1801. It is listed here as a 7th magnitude star. Additional studies of its apparent magnitude, that were conducted in the 19th century, show that the enormous star had been in the process of fading since 1850.

Since 1847, VY Canis Majoris has been described as a “crimson star.” During the 19th century, astronomers measured at least a half-dozen components. This suggested that it might be a multiple star. However, these discrete components are now known to be particularly brilliant areas in the surrounding nebula. Visible observations obtained in 1957, as well as high-resolution imaging conducted more recently in 1998, indicate that there are no stellar companions–and that VY Canis Majoris is experiencing a very lonely old age.

Classified as a high-luminosity M star, VY Canis Majoris has an effective temperature of about 3,500 Kelvin, which puts it at the upper-right hand corner of the Hertzsprung-Russell diagram of stellar evolution. This means that it is a highly evolved star in the process of dying. However, VY Canis Majoris will not go gentle into that good night, and will blast itself to pieces in a supernova explosion.

When VY Canis Majoris was still on the hydrogen-burning main-sequence of the Hertzsprung-Russell diagram, it was an O-type star with the hefty mass of 15 to 35 times that of our Sun. 바카라사이트

Dr. Roberta M. Humphreys, a professor of astronomy at the University of Minnesota, used the spectral energy distribution distance of VY Canis Majoris to determine its luminosity. Although Dr. Humphreys originally estimated the hefty star’s radius at 1,800 to 2,100 solar radii, more recent measurements made with the VLT indicate that the star really has a radius of 1420 plus or minus 120 solar radii.

Stellar Hypergiants

hypergiant star like VY Canis Majoris boasts an immense luminosity showing signs of an extremely high rate of mass loss. The word hypergiant itself is normally used as an all-encompassing term describing the most luminous stars observed. However, more precise definitions exist.

In 1971, the American astronomer Philip Childs Keenan (1908-2000) proposed that the term should only be used to describe supergiants sporting at least one broad emission component that would indicate an extended stellar atmosphere or a relatively high rate of mass loss. This criterion first suggested by Keenan is the one most commonly used by astronomers today. Keenan collaborated with William Wilson Morgan and Edith Kellman (1911-2007). In addition, hypergiants are predicted to show characteristic broadening and red-shifting of their spectral lines, thus producing a distinctive shape termed a P Cygni profile. However, this particular method, that uses hydrogen emission, is not especially helpful for characterizing the coolest hypergiants, and these are primarily classified on luminosity because the shedding of mass is almost inevitable for this class of relatively cool hypergiants.


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