Final answer:
The most distant observable objects in the universe are galaxies and quasars billions of light-years away. Stars are supported against gravity by nuclear fusion in their cores. The North Star won't always be the pole star due to Earth's axial precession, and comets are composed of ice, dust, and rocks.
Step-by-step explanation:
The most distant objects in the universe that we can currently observe are galaxies and quasars billions of light-years away. To determine distances in space, astronomers use a variety of methods, such as standard candles like certain types of supernovae or variable stars whose luminosity we understand.
What supports stars against gravity is the process of nuclear fusion occurring in their cores, where hydrogen is converted into helium, releasing energy that provides an outward pressure. This pressure balances against the inward pull of gravity, a state known as hydrostatic equilibrium.
The North Star, or Polaris, will not always be the pole star due to the precession of Earth's axis, which causes the celestial pole positions to change over a cycle of approximately 26,000 years. Eventually, other stars will take its place as the North Star.
Comets are made of ice, dust, and rocky materials. As they approach the sun, they heat up and release gases and dust, forming a glowing coma and sometimes a tail that extends away from the sun.