Astronomers have obtained remarkably detailed images of two stellar explosions -- called novae -- just days after they began.

Physicists have started to treat a once-fringe idea with surprising seriousness: that our entire observable universe might be ...

The roots of Russia's invasion of Ukraine go back decades and run deep. The current conflict is more than one country fighting to take over another; it is — in the words of one U.S. official — a shift ...