In it, he theorized that a technologically advanced extraterrestrial civilization might completely surround its native star with artificial structures in order to maximize the capture of the star's available energy.

A key indicator of this energy distribution is given by the color index, B − V, which measures the star's magnitude in blue ( B ) and green-yellow ( V ) light by means of filters.

The ratio of M to R increases by a factor of only three over 2. 5 orders of magnitude of M. This relation is roughly proportional to the star's inner temperature T < sub > I </ sub >, and its extremely slow increase reflects the fact that the rate of energy generation in the core strongly depends on this temperature, while it has to fit the mass – luminosity relation.

For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space.

The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes.

The onset of nuclear fusion leads relatively quickly to a hydrostatic equilibrium in which energy released by the core exerts a " radiation pressure " balancing the weight of the star's matter, preventing further gravitational collapse.

A star also radiates neutrinos, which carry off some energy, about 2 % in case of our Sun, producing a stellar wind and contributing to the star's total luminosity.

About 90 % of the CNO cycle energy generation occurs within the inner 15 % of the star's mass.

These planets may have vast differences in temperature between their day and night sides which produce supersonic winds, although the day and night sides of HD 189733b appear to have very similar temperatures, indicating that planet's atmosphere effectively redistributes the star's energy around the planet.

Outside of this region, in the star's envelope, energy is carried to the photosphere by plasma convection, where it radiates into space.

This release of energy may be observed as in increase in the star's luminosity with a space telescope, and is called an X-ray burst.

This energy is being radiated from the star's outer atmosphere at an effective temperature of 3, 180 K. This gives it the cool orange-red glow of an M-type star.

: ( energy is consumed and the star's core collapses )

Due to core nuclear reactions being slightly slower, the star contracts and since very similar energy is coming from a much smaller area ( photosphere ) then the star's surface becomes much hotter.

This runaway reaction quickly climbs to about 100 billion times the star's normal energy production ( for a few seconds ) until the temperature increases to the point that thermal pressure again becomes dominant, eliminating the degeneracy.

* Stellar-wind bubble, a large cavity in the interstellar medium created by a star's energy

The simplest system for star lifting would increase the rate of solar wind outflow by directly heating small regions of the star's atmosphere, using any of a number of different means to deliver energy such as microwave beams, lasers, or particle beams – whatever proved to be most efficient for the engineers of the system.

To inject energy into the star's atmosphere the ring current would first be temporarily shut down, allowing the particle accelerator stations to begin falling freely toward the star's surface.

As a star's mass is reduced by star lifting its rate of nuclear fusion will decrease, reducing the amount of energy available to the star lifting process but also reducing the gravity that needs to be overcome.

If the star's mass, when on the main sequence, was below approximately 0. 5 solar masses, it is thought that it will never attain the central temperatures necessary to fuse helium .< sup >, p. 169 .</ sup > It will therefore remain a hydrogen-fusing red giant until it eventually becomes a helium white dwarf .< sup >, § 4. 1, 6. 1 .</ sup > Otherwise, when the core temperature reaches approximately 10 < sup > 8 </ sup > K, helium will begin to fuse to carbon and oxygen in the core by the triple-alpha process .< sup >,§ 5. 9, chapter 6 .</ sup > The energy generated by helium fusion causes the core to expand.

If the central star's energy output suddenly decreases, even for a relatively short while, the planet's water may freeze.

Conversely, if the central star's energy output significantly increases, the oceans may evaporate, resulting in a greenhouse effect ; this may preclude the oceans from reforming.

Also, if the nuclear burning is not stable, or the star's core is rapidly collapsing, an entropy term must be added to the energy equation.

Although there is a high level of noise in the radial velocity data due to magnetic activity in the star's photosphere, any periodicity caused by this magnetic activity is expected to show a strong correlation with variations in emission lines of ionized calcium ( the Ca II H and K lines ).

The source for this strong X-ray emission is the star's hot corona.

Hubble's Variable Nebula is illuminated by R Monocerotis, a young variable star embedded in the nebula ; the star's unique interaction with the material in the nebula makes it both an emission nebula and a reflection nebula.

The star's magnetic field is created by convection throughout the stellar body, and the resulting flare activity generates a total X-ray emission similar to that produced by the Sun.

For Be stars such as this, the emission lines are produced by a rotating circumstellar disk of gas, made of material that has been ejected from the star's outer envelope.

By the time of William Herschel astronomers recognized that the telescopic disks of stars were spurious and a function of the telescope as well as the brightness of the stars, but still spoke in terms of a star's size more than its brightness.

The vibrational and rotational signatures of molecules such as titanium oxide, cyanide, and carbon monoxide can be seen in this wavelength range and can give a clue towards the star's spectral type.

When the star's or planet's net emissivity in the relevant wavelength band is less than unity ( less that that of a black body ), the actual temperature of the body will be higher than the effective temperature.

where is the star's luminosity distance in parsecs, wherein 1 parsec is approximately 3. 2616 light-years.

where p is the star's parallax in arcseconds.

Since the telescope has been adjusted by the angle SES ′, the star's apparent position is hence displaced by the same angle.

For approximately two to three weeks on either side of November 30, Antares is not visible in the night sky, because it is near conjunction with the Sun ; this period of invisibility is longer in the Northern Hemisphere than in the Southern Hemisphere, since the star's declination is significantly south of the celestial equator.

The Chandrasekhar limit is the mass above which electron degeneracy pressure in the star's core is insufficient to balance the star's own gravitational self-attraction.

Variations in the star's radial velocity — that is, the speed with which it moves towards or away from Earth — can be detected from displacements in the star's spectral lines due to the Doppler effect.

Some of these may have once belonged to a star's planetary system before being ejected from it ; the term " rogue planet " is sometimes applied to such objects.

They also contain a small proportion of heavier elements, and this fraction is referred to as a star's metallicity ( even if the elements are not metals in the traditional sense, such as iron ).

In Niven's novel Ringworld's Children the Ringworld itself is converted into a gigantic Quantum II hyperdrive and launched into hyperspace while within its star's gravity well.

Ringworld's Children reveals that there is life in hyperspace around gravity wells and that hyperspace predators eat spaceships which appear in hyperspace close to large masses, thus explaining why a structure as large as the Ringworld can safely engage the hyperdrive in a star's gravity well.

During this stage of the star's lifetime, it is located along the main sequence at a position determined primarily by its mass, but also based upon its chemical composition and other factors.

That is, for a given mass and composition, there is a unique solution for determining the star's radius and luminosity.

By this theorem, once a star's chemical composition and its position on the main sequence is known, so too is the star's mass and radius.