Pollux, the brighter of the twin stars of Gemini, is a giant. Its expanded to about nine times the diameter of the Sun a beach ball to the Suns golf ball. Thats made Pollux much cooler than the

The planets that flank Earth huddle close together in the dawn sky over the next few days. Venus and Mars are quite low in the east-southeast during the waxing twilight, so you need a clear horizon to

Hydra, the water snake, is the largest of all the constellations and by far the longest. It spans more than 100 degrees almost a third of the way around the sky. So it takes a long time to climb i

The Moon slides along one of the horns of Taurus tonight. At nightfall, the bulls bright eye, the star Aldebaran, is to the lower right of the Moon. And the tip of the horn, El Nath, is closer to the

The Suns birthplace has long since fallen apart. The Sun almost certainly was born in a cluster, with anywhere from dozens to thousands of siblings. Over a few hundred million years, though, the clus

The Sun is near the top of its class class G. Such stars all have about the same temperature, so they look yellow. Members of the class that are in the prime of life, as the Sun is, are also close

The average depth of the oceans on Earth is a little more than two miles. And the greatest depth is about seven miles. But thats little more than a big puddle compared to the ocean on Ganymede, the b

Astronomers use many techniques to find planets in other star systems. One of those is looking where there doesnt appear to be anything wide gaps in disks of dust around young stars. Most of these

The Vikings liked to see the world. For a couple of centuries, they plied northern oceans, exploring much of Europe, establishing colonies in Greenland, and even reaching North America. They did so wi

We can never just look up in the sky, point to one of the dots of light there, and say, Oh, yeah thats Neptune! Although its the fourth-largest planet in the solar system, Neptune is so far that