What are facts about a high mass star?

Answer 1

For HIGH mass stars- 1. the hydrogen in the core burns until only helium is left. 2. Then the core contracts, while the outer layers expand. 3. It expands into the red-giant stage and 4. then to the super-giant stage. 5. It will finally die in a supernova explosion, 6. leaving behind a white dwarf (if its final mass is less than 1.4 solar masses), a neutron star (if the final mass is between 1.4 and 3 solar masses) or a black hole (if the final mass is more than 3 times that of the Sun).

Answer 2

For stars more massive than the sun the process is predominantly the same as for sun-like stars. Some differences should be noted however.

First off, for massive stars the processes are all significantly faster and hotter than for smaller stars. For example, hydrogen burning in the center of a massive star occurs at a temperature of approximately 40 million Kelvin, as compared to 10 million Kelvin in the center of the sun. In addition, a sun-like star may spend 9 billion years on the main sequence, whereas a massive star may spend less than one billion years on the main sequence. The position of the protostar and the main sequence star on the HR diagram will also vary with the mass of the star. Massive stars will be along the upper left portions of the main sequence while low mass stars fall upon the lower right portion.

Sun-like stars are unable to burn beyond the helium stage, however, high mass stars are capable of burning carbon and oxygen and beyond, depending upon their mass. In many cases the star will reach a point where silicon undergoes nuclear fusion being converted into iron. This is the final possible stage for any nuclear burning in any star. This is because in all cases of fusion, energy is produced during the burning process. That is to say, by Einstein's theory of relativity, the mass of the byproduct is less than the mass of the nuclei used to create it. But this trend ceases at iron. In order to convert iron nuclei into a heavier nucleus, energy must be added to the process. This will not be performed under normal circumstances.

When the stellar core is completely iron and no energy is being produced the core will once again collapse under gravitational pressure. This collapse will eventually cease due to electrons becoming too close as was seen in the case of the helium flash. The electrons will support the core against collapse but only to a certain point. If the mass of the core exceeds an upper value, referred to as the Chandrasekhar limit, then the gravitational force will be stronger than the electron force and core collapse will continue.

At the point the Chandrasekhar limit is exceeded, the core temperature and density will reach values far beyond anything experienced within the star to this point. As the temperature of the core rises the radiation generated falls within the gamma ray portion of the spectrum. These high-energy gamma rays will strike through the iron nuclei like a cue ball through rack of billiard balls. The iron nuclei will be broken into individual neutrons and protons. This process is referred to as photodisintegration. The loose protons and electrons will be forced so closely together that they will combine to form neutrons. This process is referred to as neutronization. Neutronization produces a large number of neutrinos. As the core continues to collapse it will compress to densities beyond the density of a single nucleus.

Meanwhile, the outer shells are not waiting idly by. The silicon shell is continuing to produce iron and this iron is sinking towards the neutron heavy core. When the iron nuclei strike the core they will bounce off at huge speeds. The recoiling nuclei will progress outward along with the shock wave which will rip the outer portions of the star completely apart. This explosive force is referred to as a supernova explosion. The Crab nebula shown below is the remnants of a supernova explosion.Credit: FORS Team, 8.2-meter VLT, ESO

After the supernova explosion there may be three possibilities for the highly compressed core. One possibility is that the core is destroyed and only the shattered star remains. Another possibility is that the core survives and is referred to as a neutron star. Lastly, the core may compress even further and become what is known as the black hole. Of these three possibilities the first is relatively uninteresting but the last two deserve some discussion. In both cases, the neutron star and the black hole, detection can be difficult. This is because both objects are very small in radius and give off little or no light.

Let's look first that the neutron star. The neutron star is going to be spinning at a very high rate due to conservation of angular momentum. Conservation of angular momentum is most often experienced when watching an ice skater spin on the axis of the skates. The skater begins with arms outstretched and a low rate of spin, but when the skater's arms are brought in, the rate of spin increases. This is conservation of angular momentum. In a similar fashion, the matter in the neutron star or the core of the star previous to the supernova explosion, is compressed to a small radius. All stars undergo a certain amount of rotation and therefore after compression the rate of rotation is increased dramatically. In the case of the neutron star, the rate of rotation may be ten or 100 or more spins per second. This rapid rotation creates a strong magnetic field in the vicinity of the neutron star. This strong magnetic field focuses the radiation from the neutron star out through the north and south magnetic poles. Therefore light from the neutron star is only detectable, if the observer is along the line of the north or south magnetic poles. In addition, the observer will only be along the line of site when the pole flashes by, much like a boat will only see the light from a lighthouse when it is pointing in its direction. Therefore detection of this light shows spikes or flashes in a very regular, or repeating, fashion.Credit: http://imagine.gsfc.nasa.gov/docs/science/know_l1/pulsars.html

An alternative method of detection can occur if the neutron star or the black hole is a member of a binary pair. In this case, the secondary star will oftentimes deposit matter onto the more evolved neutron star or black hole. When this occurs the matter from the secondary star spirals into the black hole or neutron star creating a donut of matter around the more evolved companion. This donut is referred to as an accretion disk. When matter falls upon the accretion disk it heats up and this allows the accretion disk to oftentimes give off x-rays. Detection of these x-rays then indicates the existence of the accretion disk and therefore the more evolved companion, although the companion itself is not detected.Credit: NASA, HST Artist's Visualization

Recall that in the case of a binary system the mass of both members can be determined. In this scenario, the mass of the more evolved companion will tell us whether or not it is a neutron star or black hole. If the mass is under about three solar masses than the companion is generally a neutron star, if the mass is more than about three solar masses the companion must be a black hole.

The physics behind a black hole is relatively complicated. To keep things simplified we need only state that the escape velocity at a certain position around the centralized mass reaches and exceeds the speed of light. The point at which this occurs is referred to as the event horizon. Nothing, neither matter nor energy, can escape the gravitational warp in space created by the central mass once it is inside the event horizon (regardless of what movies and TV would have you believe).

Answer 3

Depends on the mass. Stars can come in many different colors, and no color at all -> if the mass is high enough, the star is considered a black hole, where the mass generates so much gravitational force that nothing, not even light, can escape.

Answer 4

Mainly, a high mass star has a very short lifetime, because it uses its fuel in a much more wasteful manner: due to its higher mass, it will get much hotter, and the fusion will occur much faster.

Answer 5

A high mass star is a star which is anything over 8 times the mass of the Sun.

Answer 6

During their helium-burning phase, stars with about 9 solar masses or above are termed massive stars.

Answer 7

Between 8 and 100 solar masses.