New study reveals mechanism behind extreme mass loss in hypergiant dying stars
Through observations ofone of the largest stars known to exist in the Milky Way, a redhypergiant known as VY Canis Majoris, astronomers have been able tounravel the mystery as to how enormous stars shed vast quantities ofmass prior to meeting their end in a cataclysmic supernova explosion.
Located in the constellation Canis Major, VY CanisMajoris is a true monster, even when compared to other stellar bodies. With amass of between 30 - 40 times that of our Sun (and 300,000 times asbright), if VY Canis Majoris were to be switched with our Sun, its bulkwould fill our solar system beyond the orbit of Jupiter.
We know from previousobservations that VY Canis Majoris is coming to the end of its life.As the hypergiant progressed through its geriatric years, it expandedexponentially, expelling around 30 times the mass of Earth each yearin the process.
It is not expected thatthe ancient star will meet its end for hundreds of thousands of years(a relatively short period in the life of a red hypergiant), and theresultant radiation will pose no threat to life here on Earth.From our vantage point, the tumultuous supernova will likely appear asbright as a second full Moon in the sky.
Under normalcircumstances, it is next to impossible to observe objects in closeproximity to a star due to the high levels of interference thrown offby bodies such as VY Canis Majoris. However, by using the advancedadaptive optics boasted by the SPHERE instrument mounted aboard the ESO's Very Large Telescope (VLT) located at the Paranal Observatory, Chile, the team were able to cut through thedistortions and observe the clouds of stellar material thrown off bythe host in its twilight years.
Based on an analysis ofthe polarisation of the starlight as it was scattered by thesurrounding cloud of stellar material, it was discovered that theparticles expelled from VY Canis Majoris were roughly 50 times thesize of the standard particles known to exist in interstellar space.
Whilst we are stilltalking about relatively minuscule particles, spanning only 0.5micrometers across, the comparatively large size of the gas and dustthrown off by VY Canis Majoris is the key to how the star sheds vastquantities of mass as it prepares to go supernova.
Prior to recentobservations it had been theorized that radiation pressure,the force exerted by starlight, was the driving force behind howenormous stars shed and push away stellar material from the upperatmosphere, but it is the size of the newly discovered particles thatmakes the theory workable.
Had the particles beenmuch lighter, the starlight would have essentially passed through,having little effect, much larger, and they would have been too heavyfor the radiation pressure to shift. The particles detected by SPHEREthread the needle, being just the right size to boast the surfacearea needed for the starlight to propel the dust and gas away from VYCanis Majoris prior to its cataclysmic death.
It is further theorizedthat the large size of the particles will grant them a better chanceof surviving the death of its host, allowing larger quantities ofsurviving gas and dust to be used by nearby stars to create the nextgeneration of planets, thus continuing the complicated cycle ofdestruction and formation that allows our galaxy to thrive.