Star
A large ball of gas that creates and emits its own radiation.
Welcome to the unknown
As many as half of all stars in the universe lie in the vast gulfs of space between galaxies, an unexpected discovery made in a new study using NASA rockets. These stars could help solve mysteries regarding missing light and particles that theory had suggested should exist, scientists say.
In the study, astronomers investigated the extragalactic background light, the sum of all light emitted by stars in the universe throughout history. Prior research had detected fluctuations in this light that did not appear to come from any known galaxies. Scientists had suggested these fluctuations might come from primordial galaxies, the very earliest galaxies, whose light has yet to be detected.
Galaxy
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
Nebula
A nebula is a giant cloud of dust and gas in space.