Monster Star Set To Explode.
Located at a distance of about 13 000 light-years from Earth, in the heart of the Milky Way in the constellation of Scorpius, a yellow hypergiant with a diameter about a thousand times bigger than our Sun could soon face its final days and die.
Despite its enormous size, the star has not been identified as yellow hypergiant until recently.
When the stars explodes, astronomers will have a new opportunity to study a supernova explosions in our galaxy.
Astronomers have used ESO’s Very Large Telescope to image the monster star, known as IRAS 17163-3907, a colossal star that belongs to one of the rarest classes of stars in the Universe, the yellow hypergiants.
The new picture is the best ever taken of a star in this class and shows for the first time a huge dusty double shell surrounding the central hypergiant.
The star and its shells resemble an egg white around a yolky centre, leading the astronomers to nickname the object the Fried Egg Nebula.
New observations show IRAS 17163-3907 shines some 500 000 times more brightly than the Sun.
The total mass of this star is estimated to be roughly twenty times that of the Sun.
IRAS 17163-3907 is one of the 30 brightest stars in the infrared sky, at the wavelength of 12 microns observed by IRAS, but it had been overlooked because it is quite faint in visible light.
“This object was known to glow brightly in the infrared but, surprisingly, nobody had identified it as a yellow hypergiant before,” said Eric Lagadec (European Southern Observatory), who led the team that produced the new images.
The observations of the star and the discovery of its surrounding shells were made using the VISIR infrared camera on the VLT.
The pictures are the first of this object to clearly show the material around it and reveal two almost perfectly spherical shells.
If the Fried Egg Nebula were placed in the centre of the Solar System the Earth would lie deep within the star itself and the planet Jupiter would be orbiting just above its surface.
The much larger surrounding nebula would engulf all the planets and dwarf planets and even some of the comets that orbit far beyond the orbit of Neptune.
The outer shell has a radius of 10 000 times the distance from the Earth to the Sun.
Yellow hypergiants are in an extremely active phase of their evolution, undergoing a series of explosive events — this star has ejected four times the mass of the Sun in just a few hundred years.
The material flung out during these bursts has formed the extensive double shell of the nebula, which is made of dust rich in silicates and mixed with gas.
This activity also shows that the star is likely to soon die an explosive death — it will be one of the next supernova explosions in our galaxy.
Supernovae provide much-needed chemicals to the surrounding interstellar environment and the resulting shock waves can kick start the formation of new stars.
The Very Large Telescope mid-IR instrument, VISIR, captured this delicious image of the Fried Egg Nebula through three mid-infrared filters that are here coloured blue, green and red.
After burning all their hydrogen all stars of ten solar masses or more become red supergiants.
This phase ends when the star has finished burning all of its helium.
Some of these high-mass stars then spend just a few million years in the post-red supergiant phase as yellow hypergiants, a relatively short time in the life of a star, before rapidly evolving into another unusual type of star called a luminous blue variable.
These hot and brilliant stars are continuously varying in brightness and are losing matter due to the strong stellar winds they expel.
But this is not the end of the star’s evolutionary adventure, as it may next become a different kind of unstable star known as a Wolf-Rayet star before ending its life as a violent supernova explosion.
Forty light years from Earth, a rocky world named “55 Cancri e” circles perilously close to a stellar inferno. Completing one orbit in only 18 hours, the alien planet is 26 times closer to its parent star than Mercury is to the Sun. If Earth were in the same position, the soil beneath our feet would heat up to about 3200 F. Researchers have long thought that 55 Cancri e must be a wasteland of parched rock.
Now they’re thinking again. New observations by NASA’s Spitzer Space Telescope suggest that 55 Cancri e may be wetter and weirder than anyone imagined.
Spitzer recently measured the extraordinarily small amount of light 55 Cancri e blocks when it crosses in front of its star. These transits occur every 18 hours, giving researchers repeated opportunities to gather the data they need to estimate the width, volume and density of the planet.
According to the new observations, 55 Cancri e has a mass 7.8 times and a radius just over twice that of Earth. Those properties place 55 Cancri e in the “super-Earth” class of exoplanets, a few dozen of which have been found. Only a handful of known super-Earths, however, cross the face of their stars as viewed from our vantage point in the cosmos, so 55 Cancri e is better understood than most.
Rethinking An Alien World
When 55 Cancri e was discovered in 2004, initial estimates of its size and mass were consistent with a dense planet of solid rock. Spitzer data suggest otherwise: About a fifth of the planet’s mass must be made of light elements and compounds–including water. Given the intense heat and high pressure these materials likely experience, researchers think the compounds likely exist in a “supercritical” fluid state.
A supercritical fluid is a high-pressure, high-temperature state of matter best described as a liquid-like gas, and a marvelous solvent. Water becomes supercritical in some steam turbines–and it tends to dissolve the tips of the turbine blades. Supercritical carbon dioxide is used to remove caffeine from coffee beans, and sometimes to dry-clean clothes. Liquid-fueled rocket propellant is also supercritical when it emerges from the tail of a spaceship.
On 55 Cancri e, this stuff may be literally oozing–or is it steaming?–out of the rocks.
With supercritical solvents rising from the planet’s surface, a star of terrifying proportions filling much of the daytime sky, and whole years rushing past in a matter of hours, 55 Cancri e teaches a valuable lesson: Just because a planet is similar in size to Earth does not mean the planet is like Earth.
It’s something to re-think about. Source: NASA
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