Hydrogen nuclei via photodisintegration
Carbon and oxygen nuclei
The helium is transformed completely to ƒ× rays, a form of pure electromagnetic energy.
Star in its first red giant phase.
Cool main sequence star.
Neutrinos, which escape easily from the core of a star but react with the cool hydrogen at its surface to form carbon.
Helium flash, in which the explosion blasts carbon from the core into the surface layers.
Dredge-up, in which the convective envelope transports material from a star's core to its surface.
Mass loss, which strips away the outer envelope from an old star and reveals the carbon-rich core.
An object like Jupiter which was not massive enough to become a star.
A low-mass star at the end of its life.
A hot, main-sequence star.
A type of protostar. star.
Iron nuclei cannot participate in nuclear reactions.
When iron nuclei undergo nuclear reactions, they always absorb energy.
When iron nuclei undergo nuclear reactions, they always give out energy.
Iron nuclei make the core magnetic.
Explosion of a massive star that has lost its hydrogen-rich outer layers through a stellar wind or mass transfer in a binary star system.
Explosion of a white dwarf in a binary star system after mass has been transferred onto it from its companion.
Collapse of a blue supergiant star to form a black hole.
Explosion of a massive star after silicon burning has produced a core of iron nuclei.
That of the Sun.
That of an average city, about 30 km.
That of Earth, 12,800 km.
A period of 1.337 seconds corresponds to a very low wave frequency of 0.7479 Hz.
A pulsating white dwarf star, fluctuating rapidly in brightness
A rapidly rotating neutron star, producing beams of radio energy and in some cases, light and X-rays
A rotating black hole, producing two jets of gas in opposite directions and pulses of gravitational energy
A Cepheid variable star with a period of a few days
Emitters of relatively narrow beams of radio energy and other electromagnetic radiation
Rotation rates from one to thirty times each second
Strong gravitational fields but weak magnetic fields
Composed almost entirely of neutrons
Slowing down, because rotational energy is being used to generate the pulses
Absolutely constant, pulsars providing ideal frequency standards or clocks.
Varying periodically as the neutron star undergoes periodic expansions and contractions.
Speeding up, as the neutron star slowly contracts under gravity.
Superconducting neutrons and superfluid electrons.
Superfluid neutrons and superconducting protons.
Superfluid neutrons and superconducting electrons.
Superconducting neutrons and superfluid protons.
Gas pressure, very similar to that described by the ideal gas equation.
Degenerate electron pressure.
Both degenerate electron pressure and degenerate neutron pressure.
Both degenerate neutron pressure and the repulsive hard core aspect of the nuclear force between neutrons.
At the same rate in a gravitational field if it is an atomic clock but at a slower rate if it is a mechanical clock.
At the same rate wherever it is placed in a gravitational field.
Faster, the closer it comes to the source of gravity.
Slower, the closer it comes to the source of gravity.
Space around the Sun is curved and Earth follows this curved space.
The Sun exerts a gravitational force on Earth across empty space.
Matter contains quarks, and Earth and Sun attract each other with the “color force” between their quarks.
Earth and the Sun are continually exchanging photons of light in a way that holds Earth in orbit.
Strongly curved space
A star with a temperature of 0 K, emitting no light.
The point at the center of every star, providing the star's energy by gravitational collapse.
Densely packed matter inside a small but finite volume.
In every known galaxy.
Nowhere in our observable universe, though the existence of such black holes has been predicted by theory.
In several dozen galaxies.
In only one galaxy, our own Milky Way galaxy.
At the point where escaping X-rays are produced
At the point where clocks are observed to slow down by a factor of 2
At the event horizon
At the singularity
Gravity in the neutron star is balanced by an outward force due to neutron degeneracy.
Neutron stars are held up by the centrifugal force due to their rapid rotation.
Neutron stars are solid, and like other solid spheres they are held up by the repulsive force between atoms in the solid.
Gravity in the neutron star is balanced by an outward force due to gas pressure, as in the Sun.
Nothing, not even electromagnetic radiation, can escape from inside them.
Only nonvisible radiation longer than about 1,000 nm wavelength (infrared and radio radiation) can escape from them.
They are always surrounded by an accretion disk which absorbs all light escaping from the inside of the black hole.
They emit an electromagnetic spectrum which matches that of a perfect blackbody.
There are so many stars in our galaxy that the more distant ones are hidden behind the nearer ones.
Distant stars are obscured by dust in interstellar space.
Expansion of the universe has carried the more distant stars out of our view.
Distant stars are obscured by gas in interstellar space.
White dwarf star behavior.
Distance, particularly to stars in our galaxy and to nearby galaxies.
Stars with very high speed motion.
The mechanics of eclipsing variable stars.
Diameter 80,000 light-years; thickness, 6,500 light-years.
Diameter 6,500 light-years; thickness 2000 light-years.
Diameter 2000 light-years; thickness, 160,000 light-years.
Diameter 160,000 light-years; thickness, 2000 light-years
It absorbs light from distant galaxies and quasars and obscures them.
It emits synchrotron radiation.
Its gravitational pull affects orbital motions of matter in the galaxy.
It blocks out the light from distant stars in the plane of our galaxy.
It is not in a galaxy, but in intergalactic space.
In the galactic halo
In the galactic disk
In the galactic nucleus