Sentences with phrase «core hydrogen fusion»

© American Scientist (Artwork by Linda Huff for Martin et al, 1997; used with permission) Although brown dwarfs lack sufficient mass (at least 75 Jupiters) to ignite core hydrogen fusion, the smallest true stars (red dwarfs) can have such cool atmospheric temperatures (below 4,000 ° K) that it is difficult to distinguish them from brown dwarfs.

According to Professor Jim Kaler at the University of Illinois» Department of Astronomy, Rana started life as a main sequence F8 dwarf (somewhat hotter and brighter than Sol with slightly greater mass) around 7.5 billion years ago, but core hydrogen fusion has ceased causing the star to expand and cool as an active subgiant before becoming much brighter and larger «as a true giant star» through core helium fusion.

Not exact matches

This «quarksplosion» would be an even more powerful subatomic analog of the individual nuclear fusion reactions that take place in the cores of hydrogen bombs.

Because all elements in the universe heavier than hydrogen, helium, and lithium have been forged by nuclear fusion in the cores of stars and then scattered into space by supernova explosions, the find indicates that the galaxy, at the age we're now observing it, was old enough for at least one generation of stars to have formed, lived, and died.

Stars are powered by nuclear fusion, converting hydrogen into helium in their cores.

A star begins to die when the last of the hydrogen fuel at its center succumbs to the star's fusion furnace and the center collapses into a highly compressed, white - hot core.

The heat becomes so intense that helium, a fusion by - product, begins to burn both within the core and just outside it, along with hydrogen remaining outside the core.

It could weaken, particularly as its plutonium core bombards it with radiation over time, subsequently failing to contain the primary fission explosion long enough to generate the high temperatures needed for fusion to take place in creating the secondary hydrogen detonation.

NIF uses the world's highest energy laser to crush peppercorn - sized targets filled with fusion fuel (a combination of hydrogen isotopes) to a temperature and pressure greater than in the core of the sun.

According to standard models of stellar evolution, around that time the sun will largely deplete the hydrogen reserves in its core and begin to balloon as its fusion reactions migrate outward.

In the meantime, however, the exposed core becomes a violent scene of fusion reactions among remaining hydrogen and helium nuclei, which release a torrent of energetic photons, mostly in the form of ultraviolet rays.

Long before descending into scientific infamy, Hoyle made what should have been a lasting contribution with a 1954 Astrophysical Journal paper laying out a process by which stars heavier than 10 suns would burn hydrogen and helium at their cores into heavier elements through a progressively hotter series of nuclear fusion reactions.

Other photographed objects have been too massive to be conclusively labeled planets, falling instead into the brown dwarf category (objects about eight to 80 Jupiters in size that lack sufficient mass to ignite hydrogen fusion in their cores, thereby never becoming true stars); have been found to themselves orbit brown dwarfs rather than stars; or have not been shown to be gravitationally bound to a star.

Brown dwarfs are not considered stars because they are too small to fuse hydrogen in their cores — they don't have the gravitational oomph in their core to sustain hydrogen fusion, but, depending on how massive they are, they do have enough mass to sporadically fuse elements like lithium and deuterium.

The total amount of energy that a star can generate through nuclear fusion of hydrogen is limited by the amount of hydrogen fuel that can be consumed at the core.

After a star has formed, it generates energy at its hot, dense core through the fusion of hydrogen atoms into helium.

Upon reaching a suitable density, energy generation is begun at the core using an exothermic nuclear fusion process that converts hydrogen into helium.

When their central temperatures reach values comparable to 107 K, hydrogen fusion ignites in their cores, and they settle down to long stable lives on the main sequence.

It continues until the core helium supply is exhausted, after which helium fusion is limited to a shell around the core, just as was the case for hydrogen in an earlier stage.

For higher mass stars with up to 10 solar masses, the hydrogen surrounding the helium core reaches sufficient temperature and pressure to undergo fusion, forming a hydrogen - burning shell.

If HD 181433 has a mass less than Sol's but is more evolved (i.e., where it may have already shut down hydrogen fusion in its helium - rich core), then it may be significantly older than Sol's 4.6 billion years.

The primary, component A, is a Sun - like star [10] with a stellar classification of F8 V, [5] indicating it is an F - type main - sequence star that is generating energy via hydrogen fusion at its core.

As a star that has evolved out of the «main sequence,» Gacrux has shifted fully from the fusion of hydrogen to helium at its core to the fusion of helium to carbon and oxygen, with trace activity of other nuclear processes.

This finding suggests that the star has had many billions of years to deplete its core hydrogen through fusion into helium.

According to James B. Kaler, hydrogen fusion at its helium - rich core may already have died out.

It rotates more slowly than Sol with a period at 34 days (Baliunas et al, 1996) and appears to be further along in core hydrogen - fusion, with a relatively weak 11 - year cycle of star spots and related chromospheric activity.

As a star that has evolved out of the «main sequence,» Arcturus has fully shifted from the fusion of hydrogen to helium in at its core to the fusion of helium to carbon and oxygen, with trace activity of other nuclear processes.

Imagine... After millions of years of nuclear fusion, a massive star depletes its core of hydrogen and helium.

Within the Sun's core, nuclear fusion reactions take place, with hydrogen nuclei being fused into helium nuclei.

As a star that has evolved out of the «main sequence,» Pollux has fully shifted from the fusion of hydrogen to helium at its core to the fusion of helium to carbon and oxygen, with trace activity of other nuclear processes.

The temperature at its core has been estimated about 15,000,000 K. Energy is produced in its core by nuclear fusion, converts hydrogen atoms and releases huge amounts of energy.

It is frequently applied to the coolest objects, including K - and M - dwarfs, which are true stars, and brown dwarfs, often referred to as «failed stars» because they do not sustain hydrogen fusion in their cores.

All stars, including our sun, will eventually run out of the hydrogen gas that fuels the nuclear fusion reactions in their cores.

During that time, it will continue to convert hydrogen into helium in its core through a process called nuclear fusion.

Hydrogen is still available outside the core, so hydrogen fusion continues in a shell surrounding tHydrogen is still available outside the core, so hydrogen fusion continues in a shell surrounding thydrogen fusion continues in a shell surrounding the core.

The effect is in the ballpark of 5 %, since the sun is 30 % brighter than when it formed 4.5 billion years ago and the brightening trend accelerates as a star ages (A little educated guessing here, but the rate of fusion increases in proportion to the star's luminosity and the pressure needed in the core is an inverse relationship to the hydrogen concentration in the core — simple linear interpolation would give a 3.3 % increase in luminosity).

If the Sun were a massive ball of hydrogen, heated by a H - fusion reactor at its core, then changes at the solar core would be delayed by about 30 My (million years), the diffusion time for radiation from the core of the Sun to its surface [See William A. Fowler, «What cooks with solar neutrinos?»