Astronomers theorize that they may be a rare type of x-ray emitting binary stars or intermediate-mass black holes.

Astronomers theorize that powerful jets of particles, possibly accelerated by an unseen, massive black hole at the center, point directly at Earth from millions of light-years away.

Astronomers theorized that it could have been a supernova, but the unique filtering properties of the foreground galaxy made it difficult to decide definitively.

Astronomers theorize however that most, if not all, novae are recurrent, albeit on time scales ranging from 1,000 to 100,000 years.

Astronomers have theorized that glitches occur when fluid inside the star rotates faster than the crust and suddenly transfers some extra momentum during a disturbance.

Astronomers theorize that these isolated stars were displaced from their home galaxies as a result of galactic mergers or tidal forces from nearby galaxies.

Astronomers theorize that a pulsar is formed when an exploding star collapses into an extremely dense mass of closely packed neutrons.

Astronomers theorize that cosmic gamma radiation may come mainly from supernovas, and the new polar telescope will test this theory.

Astronomers theorize that a collision with a smaller companion galaxy near the core of the main galaxy could have led to the unusual spiral structure.

Astronomers theorize that such an orbital migration, powered by a gravitational tug--of-war with other cosmic bodies, would take hundreds of millions of years.