White Dwarfs : The Remnants Of Stars

When stars died, chemicals other than hydrogen and helium formed, which led to the next level of complexity—Heavier Chemical Element. Most stars spent about 90% of their life over billions of years on during protons and hydrogen nuclei into helium nuclei. When they run out of fuel, the furnace at the center of the star stopped supporting the star, and gravity took over. Small stars did not have much pressure at the center. They burned hydrogen slowly over billions of years at relatively low temperatures. When they died, they would slowly fade away. However, great stars had so much mass that they can create enormous pressures and temperature, and when the giant stars ran out of hydrogen, the temperature got cranked up even higher, which led the star to collapse. The high temperature that the collapse caused was able to make helium nuclei fuse into nuclei of carbon. When a star used up its helium, it collapsed again, and the cycle started over. The star heated up and began to fuse carbon to form

One solar mass is equal to the mass of the Sun, about 2 nonillion kilograms. If a white dwarf were to exceed ~1.44 solar masses, its electron degeneracy pressure would not be able to support it.

2) The force that causes a neutron star not collapse further is called Neutron degeneracy pressure. When a white dwarf reaches a mass greater than the Chandrasekhar limit the electron degeneracy pressure is no longer strong enough to prevent further collapse. Neutron degeneracy is more powerful than electron degeneracy and can withstand greater pressure. Neutron degeneracy refers to the principle that two neutrons cannot occupy the same space and therefore have a repulsive force on each other.

Pulsating white dwarf stars are a special subclass of white dwarfs, and they are very useful tools for studying the interiors of stars. As the interior of the white dwarf changes and oscillates, the light signal from the star will pulsate at numerous frequencies. By determining the frequencies at which the star pulsates and using these as boundary conditions in stellar models, astronomers can determine the interior properties of white dwarfs. This summer I was involved in using data from the Whole Earth Telescope and CCD images to determine the frequencies at which two different white dwarf stars pulsate.

At that point, the star begins to fuse helium into carbon in the core. This is called helium fusion. In order for this to happen, the core’s density has to increase and the temperature has to reach about 100 million Kelvin. However, a complication arises when helium fusion begins. The star’s core is degenerated and the burning becomes unstable since the core is not able to accommodate the fusion. The increase of internal pressure and temperature caused by the burning of the helium leads to an astronomical increase in outward pressure. This is, eventually, able to regulate and the core is able to expand and decrease its

As this slow contraction continues, the core temperature, density, and pressure of the star continues to increase. As the star shrinks it becomes so dense that it starts to compress helium. This results in the star to swell due to the hot core and leaving a relatively cool surface. Eventually the outer layers of the star expand outwards, increasing the size of the star. As the layers continue to expand, the surface temperature continues to cool, forming a relatively large star called a red giant.

One day the universe will turn dark forever as the last star fizzles out and that star will most likely be a red dwarf. When a red dwarf star forms it possesses important properties that give it the potential to host rocky planets similar to Earth. Therefore the creation and resulting properties of red dwarfs form stars that can provide energy to planets which may one day be hospitable to life forms. First the process of formation of red dwarfs will be explained. Then, the properties of these stars will be examined. Finally, the importance of red dwarf stars’ existence will be considered.

(2) Sub-stellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are brown dwarfs, no matter how they formed nor where they are

This star is formed after a large star has had a supernova explosion. These stars are usually very dense and will eventually produce a black hole. Magnetar is a neutron star with an extremely strong magnetic field. Magnetar stars are highly magnetic objects, they are even stronger than Earth. It is also 100 to 1,000 times stronger than radio pulsar. Because we are unsure how this star can be as strong as it is, theorist say it would have to rotate between 100 to 1,000 times per second. Brown Dwarfs is the in between size of a giant planet and a large star. This star is also a very dense star, but not as dense as the white dwarf. When a star is dying it squeezes all its matter into a tiny space, this is called a Black Hole. Their gravity is so strong from all the matter in a tiny space that nothing, not even light can escape. You can’t detect a Black Hole with the naked eye because it's actually invisible, you need a science telescope to identify them. The Cepheid Variable stars light brightens and dims many times. It’s like when the sun is out then goes behind a cloud then comes back out

The Super Soft Source (SSS) phase of novae is the last major evolutionary phase during which the hottest layers closest to the surface of the white dwarf can be observed until the hydrogen content of the accreted material is consumed or ejected. The X-ray and UV evolution of novae during their outbursts has been determined using Swift monitoring observations. Deeper, continuous XMM-Newton and Chandra observations have been taken, guided by the long-term evolution determined by Swift. The time when bright SSS emission becomes visible, the turn-on time of the SSS phase, depends on the evolution of the nova ejecta. Accurate predictions are currently not possible from evolutionary models, but empirical scaling relations have recently been derived from population studies (Henze et al. 2013; Schwarz et al. 2011).

Neutron stars are “an incredibly object made of neutron’s, like a giant atomic nucleus.” In the year 1934 two astronomers at CIT made predictions that a collapse of a large star or sun would produce a neutron star. When a star 's mass exceeds roughly 1.4M and has a iron core. It is no longer able to support itself, the core collapse from exponential forces. This is referred to as a type ii supernova or a core-collapse supernova. These newly discovered neutron stars had notable characteristics. A smaller radius of around six miles and masses that were on average between “one and several times the sun”. Neutron stars also had capacity for how large their masses could be, at max it could be two to three solar masses. Although these neutron

If it has a whitish appearance its temperature is somewhere in between like our Sun. We can see how this happens and how we can then divide stars by mass into three main groups (Red Giants, Main Sequence Stars and White Dwarfs [bluish]) on the Hertzsprung-Russell diagram. An HR Diagram is a graph that plots stars as points by measuring their stellar luminosity in typical solar units (x axis) and surface temperature in multiple luminosity of the Sun (y axis). The diagram provides information about stellar radii, because a star’s luminosity depends on both its surface temperature and its surface area or radius. As you can see on the graph stellar radii increase as we go from the high-temperature, low-luminosity corner (lower left)[White Dwarfs] to the low-temperature, high-luminosity corner (upper right) [Red Giants].

If we look over the the hertzsprung Russell diagram, supergiants occupy a spectral range between O-M. This corresponds to temperatures ranging from 3,500 - 30,000K. All supergiants are extremely luminous; being at least over 30,000 the luminosity of the sun.

For the low-mass stars, the expansion to the red giant phase will begin when about 90% of its hydrogen has been converted to helium. During the contraction of its core, a complicated sequence of events occurs. The shrinkage required to produce the energy radiated by the large giant causes the core to shrink to the dimensions of a white dwarf, while hydrogen continues to burn by nuclear fusion in a thin shell surrounding the core. This shell provides most of the energy that is radiated away by

Main sequence stars like our own sun enduring in a state of nuclear fusion during which they will produce energy for billions of years by replacing hydrogen to helium. Stars change over billions of years. When their main sequence phase ends they pass through other states of existence according to their size and other characteristics. The larger a star's mass, the shorter its lifespan is. As stars move toward the end of their lives, much of their hydrogen will be converted to helium. Helium sinks to the star's core and raises the star's temperature—causing its outer shell to expand. These large, puffy stars are known as Red Giants. The red giant phase is actually a prelude to a star shedding its outer layers and becoming a small, dense body called a White Dwarf. White dwarfs cool down for billions and billions of years, until they finally go dark and produce no energy at all. Once this happens, scientists have yet to observe, such stars become known as Black Dwarfs. A few stars avoid this evolutionary path and instead go out with a bang, exploding as Supernovae. These violent explosions leave behind a small core that will then turn into something called a Neutron Star or even, if the remainder is large enough, it is then turned into something called a Black Hole.