Overwintering monarch butterflies rely on a temperature-sensitive internal timer to wake them up to make the trip back north, researchers report.

On August 7, 8 and 9, 2019, watch as the moon moves out from in front of the constellation Libra, then sweeps in front of neighboring Scorpius and past the bright planet Jupiter.

Jupiter and Saturn have appeared close on our sky's dome throughout 2019, but they're due to get even closer in the coming months. Their conjunction will come on December 21, 2020. Here's how to watch them.

Mercury will be over 18 degrees west of the sun - that is, visible in our eastern sky before sunrise - all this upcoming week, from about August 7 to 14, 2019. With Mercury getting brighter by the day, you might it before sunrise for the next 2 weeks at northerly latitudes.

Io's volcanoes have fascinated scientists since the Voyager 1 spacecraft first discovered them nearly 40 years ago. Now a comprehensive new report - based on ground-based studies - unveils new mysteries about the most volcanically active world in our solar system.

Most people don’t associate the US Pacific Northwest with earthquakes, but maybe they should. It’s home to the 600-mile (1,000-km) Cascadia megathrust fault, stretching from northern California to Canada’s Vancouver Island.

For mosquitoes, finding the next blood meal is all about smelling and seeing. It's our breath that gives us away.

On August 4 to 6, 2019, the moon is a waxing crescent in the sunset direction. Look for it shortly after sunset, as day fades to night. The moon will be below Spica August 4, closest to it August 5 and above it August 6.

The newfound dynamic duo of white dwarfs- called ZTF J1539+5027 - orbit each other every 7 minutes.

Here's a reconstructed "perspective view" of the tallest mountain on Ceres, which in turn is the largest world in the asteroid belt between Mars and Jupiter. Earthly astronomers call the mountain Ahuna Mons.