Our Star, the Sun
The Sun was born about 4.6 billion years ago from the gravitational collapse of a vast cloud of gas and […]
Mercury
Mercury's surface closely resembles the Moon's. It is covered by impact craters, ancient lava flows, and quake fault lines. Mile-high
What causes the bright halo that sometimes surrounds the Moon?
This bright ring of light is quite common. It’s related to the same process that creates rainbows: refraction. In this
What causes the bright halo that sometimes surrounds the Moon? Read More »
Who built the first observatory?
Observatories, like so much of astronomy, are truly ancient features of human culture; retracing the steps of the first person
Who made the first map of the universe?
Maps of the stars are nearly as ancient as human culture itself; inscriptions describing the positions of stars and constellations
How was the size of Earth first measured?
Earth’s circumference was first accurately measured more than 2,000 years ago by the Greek astronomer Eratosthenes, who at the time
What is the nearest star?
Of course, the nearest star to Earth is the one we see every day — our dear old Sun. At
How big is the solar system?
The farthest known object orbiting our Sun is a ball of ice and rock unofficially called FarFarOut, which lies about
Is there a tenth planet in our solar system?
No. On August 23, 2006, the International Astronomical Union decided that the solar system contains only eight planets. Pluto, which