White dwarf star

Wispy remains of a supernova explosion hide a possible ‘survivor.’ Of all the varieties of exploding stars, the ones called Type Ia are perhaps the most intriguing. Their predictable brightness lets astronomers measure the expansion of the universe, which led to the discovery of dark energy. Yet the cause of these supernovae remains a mystery. Do they happen when two white dwarf stars collide? Or does a single white dwarf gorge on gases stolen from a companion star until bursting? If the second theory is true, the normal star should survive. Astronomers used the Hubble Space Telescope to search the gauzy remains of a Type Ia supernova in a neighboring galaxy called the Large Magellanic Cloud. They found a sun-like star that showed signs of being associated with the supernova. Further investigations will be needed to learn if this star is truly the culprit behind a white dwarf’s fiery demise.

 This supernova remnant is located 160,000 light-years from Earth. The actual supernova remnant is the irregular shaped dust cloud, at the upper center of the image. The gas in the lower half of the image and the dense concentration of stars in the lower left are the outskirts of a star cluster.

Image credit: NASA, ESA and H.-Y. Chu (Academia Sinica, Taipei)

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We just got our first complete look at an exploding white dwarf star

For the first time ever, scientists have captured the full process of a nova explosion — the moments before, during and after the blast.

Nova explosions are different from supernovas because the star isn’t completely destroyed. Novas happen in two-star systems, when a white dwarf star has been sucking in mostly hydrogen gas from a close neighboring star. The extra hydrogen explodes, but the explosion only happens on the star’s surface. Apparently, white dwarfs have something in common with bears.

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Of all the varieties of exploding stars, the ones called Type Ia are perhaps the most intriguing. Their predictable brightness lets astronomers measure the expansion of the universe, which led to the discovery of dark energy. Yet the cause of these supernovae remains a mystery. Do they happen when two white dwarf stars collide? Or does a single white dwarf gorge on gases stolen from a companion star until bursting?

If the second theory is true, the normal star should survive. Astronomers used NASA’s Hubble Space Telescope to search the gauzy remains of a Type Ia supernova in a neighboring galaxy called the Large Magellanic Cloud. They found a sun-like star that showed signs of being associated with the supernova. Further investigations will be needed to learn if this star is truly the culprit behind a white dwarf’s fiery demise.

This image, taken with NASA’s Hubble Space Telescope, shows the supernova remnant SNR 0509-68.7, also known as N103B. It is located 160,000 light-years from Earth in a neighboring galaxy called the Large Magellanic Cloud. N103B resulted from a Type Ia supernova, whose cause remains a mystery. One possibility would leave behind a stellar survivor, and astronomers have identified a possible candidate.

The actual supernova remnant is the irregular shaped dust cloud, at the upper center of the image. The gas in the lower half of the image and the dense concentration of stars in the lower left are the outskirts of the star cluster NGC 1850.

The Hubble image combines visible and near-infrared light taken by the Wide Field Camera 3 in June 2014.

Image credit:andnbsp;NASA, ESA and H.-Y. Chu (Academia Sinica, Taipei)
Text: Space Telescope Science Institute
Media contact: Rob Gutro, NASA’s Goddard Space Flight Center, Greenbelt, Md.

Hubble Space Telescope

Time And Space

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White Dwarfs and Neutron Stars

What happens to a star after it dies depends entirely on the mass it contains. If the star has a low to medium mass (anything less than 8 solar masses) then at the end of its life it will transform into a white dwarf. If a star is massive (8-20 solar masses) then it will turn into a neutron star.

When a red giant starts to fuse helium to carbon and oxygen but lacks the mass to generate the core temperatures required to fuse carbon, an inert mass of carbon and oxygen will build up at the core. Towards the end of the stars nuclear fusion stage, it will shed its outer layers in the form of ionized gas forming a planetary nebula. The core that is left behind is the white dwarf typically about the size of earth. This is made up of electron degenerate matter which forms because the white dwarf lacks its previous ability to create an internal pressure meaning gravity squashes the mass much closer together. The reason this is happens is because under normal circumstances electrons with the same spin can’t occupy the same energy level, and there’s only two ways an electron can spin (this is known as the Pauli Exclusion Principle). In a normal gas this isn’t a problem because there aren’t enough electrons to fill the energy levels. In a “degenerate” gas however, all its energy levels filled. For a white dwarf to be forced smaller by gravity, it would have to make electrons go where they couldn’t go thus white dwarfs survive through quantum mechanical principles that prevent their collapse further. There are other unusual properties as well, white dwarfs with greater masses are actually smaller because gravity has to force the electrons closer together to maintain the outward pressure. However there is a limit to how much mass a white dwarf can have and it’s about 1.4 solar masses.

Neutron stars are incredibly dense (and one of my favourite things ever) with a typical one being about 20km and containing 1.4 solar masses. A teaspoon would weigh about a billion tonnes on a neutron star that’s how dense they are. They are also composed entirely of neutrons as the force of gravity is so great that it has caused the electrons and protons to merge into neutrons. The power from the supernova that created the star causes it to spin up to 43,000 times a minute gradually slowing over time. The neutron stars which are still spinning emit electromagnetic radiation that we can detect when it’s pointing towards earth (much like a lighthouse). These neutron stars are known as pulsars. The magnetic axis of the pulsar is what determines the direction the beam will fire off in. However this is not necessarily the same as the rotational axis and this misalignment is what causes pulsars to appear to pulse. There are currently three different types of pulsars that astronomers are aware of. The first is rotation powered pulsars which the radiation given off is caused by a slowing down of the rotation of the star. Accretion powered pulsars occur when the gravitational potential energy that falls onto the neutron star causes X-Ray’s that can be received from Earth. Finally there is magnetars where the radiation is caused by an extremely strong magnetic field losing energy.

anonymous asked:

Tbh I think that lord Sirius isn't actually the blue star since Sirius (the actual star) isn't even a blue star. There is, however, a very large blue star directly below it. Giving all the stars the title "lord" would imply that they're all of the same status. It also means that there is a caste system at sphere music hall. But the blue star is never referred to as lord, only the "blue (or pale) star". It's like when there's lords and a ruler, the ruler isn't a lord since he's higher than that.

Sigh… Sirius is a BINARY star system – a huge blue Sirius A, and a white dwarf Sirius B. Sirius B used to be blue and more massive (and brighter) than Sirius A, but then it collapsed, becoming the white dwarf we see today. This is also probably why the Sirius system is being used to denote blood type AB, because it has BOTH.

At this point, it’s hard to tell who is Sirius A… and who is Sirius B. Perhaps Blavat calls Lord Sirius “Blue Star” only when talking to certain people, OR perhaps he’s saying this was all a trap to get the earl, making the earl the “Blue Star”, the one who (now) shines brighter.

Either way, there is the company Blue Star Line, and it is probably controlled by Lord Sirius. Perhaps Lord Sirius considers himself to be Sirius A, but others know he’s now the white dwarf Sirius B.

PERSONALLY, I’ve come to the headcanon conclusion that Lord Sirius is the once-bright blue star who became the white dwarf shell of his former self (when he died and was turned into a Bizarre Doll), while the earl is the remaining blue star who still shines bright…. They revolve around each other, tugging at each other, getting ever closer until the collide, just like the real Sirius A and Sirius B….

About the lords of the stars, they are not given the same status. Lord Polaris is a butler and stays in a destroyed room with few appointments. Lord Canopus is also in a basic room. The two Lord Vegas are higher class in a nice bedroom, and Lord Sirius is in a stately bedroom…. Even Blavat says some stars are a higher magnitude that others, Sirius being first magnitude, Canopus being second magnitude, etc. Ch127 suggests that Lord Polaris is actually the butler to Lord Sirius. They are only called “lords” because they are the representatives of their stars/blood types for the purposes of the Blue Sect….