domingo, 11 de mayo de 2014

The strangest and biggest things in space

Photo credit: FORS Team, 8.2-meter VLT Antu , ESO

 

The ‘gap’ in space

 

This ‘gap’ in space is actually Barnard 68, a molecular cloud about 500 light-years away in the constellation of Ophiuchus, the Serpent-holder. The gap is an example of a Bok globule, which are dark clouds of dense cosmic dust and gas that appear opaque in the visible light spectrum. There are around 3,700 stars within this globule, which is half a light year across. Barnard 68’s interior is very cold – about -257°C.

 

The biggest star

 

The biggest known star in the Universe is VY Canis Major, a red supergiant star that is also classified as a hypergiant because of its very high luminosity. It is located 5,000 light-years away and is 500,000 times brighter and about 30 to 40 times more massive than our Sun. If our Sun was replaced with VY Canis Majoris, its surface could extend to the orbit of Saturn.

 

The oldest star

 

While the image may not be impressive compared to other images of stars, the star itself is extremely impressive due to its age. The Methuselah Star (HD 140283) is the oldest star with a determined age. Astronomers in the 1950’s noticed it had a deficiency of heavy elements compared to other nearby stars, suggesting that it formed in a very early period in the Universe. The star likely formed in a primeval galaxy which was later shredded by the Milky Way over 12 billion years ago. Early estimates put the star’s age at 16 billion years old, which would make it older than the accepted age of the universe (13.8 billion years). The star is now estimated to be around 14.5 billion years old (plus or minus 0.8 billion years), which has the star’s age overlapping with that of the Universe.

 

Super magnetars

 

NGC 1624-2 is 20,000 light-years from Earth in the constellation Perseus, and may be the most magnetic massive star seen yet. NGC 1624-2 has about 35 times the mass of our Sun and has a magnetic field 20,000 times stronger than the Sun's and nearly 10 times stronger than that detected around any other high-mass star. NGC 1624-2 is the most magnetic of all known massive stars, though some intermediate mass stars have magnetic fields twice as strong. A typical magnetar might have a field on the order of 10 trillion gauss, while the magnetic field of NGC 1624-2 is about 20,000 gauss at the star's surface.

 

Hypervelocity stars

 

The first hypervelocity star was discovered in 2005: a massive star whose 3.2 million kmph velocity can only have come from ejection from the Galaxy's massive black hole. The star is essentially an outcast and is destined to drift alone through intergalactic space. The study of hypervelocity stars tell us about the types of stars that orbit near the central black hole of galaxies. Since the initial discovery astronomers have found 15 more "hypervelocity" stars. in 2012, Vanderbilt astronomers reported that they had identified a group of more than 675 stars on the outskirts of the Milky Way that could be hypervelocity stars ejected from the galactic core.

 

Weird spiral from LL Pegasi

 

While no astronomer is sure about what created the spiral structure on the left in the image, it’s likely to be related to a star in a binary star system entering the planetary nebula phase, when its outer atmosphere is ejected. The spiral is about a third of a light year across and winds about four or five turns. The expansion rate of the spiral gas indicates a new layer must appear every 800 years. The star system that created the spiral is also known as AFGL 3068, though the spiral itself is known as IRAS 23166+1655. The reason why the spiral glows is a mystery, though the leading hypothesis is that it is illumination from nearby stars.

 

Biggest black hole: NGC 1277

 

Though is listed as the second biggest black hole observed, it may actually be the biggest as the current record holder has still not been precisely calculated. NGC 1277 is 220 million light years away in the constellation Perseus, in a small galaxy just a tenth the size of our Milky Way. The black hole has a mass 17 billion times that of our Sun, comprising 14% of the galaxy’s entire mass. The size of this supermassive black hole’s event horizon is eleven times the diameter of Neptune’s orbit — a radius of over 300 AU.

 

The biggest structure in the universe: the large quasar group (LQG)

 

The LQG is so large it would take a vehicle travelling at the speed of light 4 billion years to cross it. Quasars, which are the nuclei of galaxies from the Universe’s early years, tend to group together. This LQG has a typical dimension of 500 Mpc (mega parsecs; a parsec is equal to about 3.26 light-years, or about 30.9 trillion kilometres), but is elongated so its longest dimension is 1200 Mpc (or 4 billion light years). This is 1600 times larger than the distance from the Milky Way to Andromeda.

 

 

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