Betelgeuse - the somber red star in the shoulder of the constellation Orion the Hunter - is one of the largest stars visible to the eye alone. Massive stars like Betelgeuse will eventually explode as supernovae. Astronomer Brad Schaefer told Earth & Sky that Betelgeuse could become a supernova any day now.

In 2007, scientists took a step forward in finding evidence for former life on Mars. A rock split open by the wheels of the Mars Spirit rover revealed that it, and rocks surrounding it, were made of more than 90 percent silica. These silica-rich rocks might be deposits from former hot springs on Mars, similar to hot springs found at Yellowstone National Park.

In 2007, astronomers discovered Gliese 581c, a planet whose radius is 50% larger than that of our Earth. Using computers to investigate the properties of distant worlds like this one, these scientists believe that plate tectonics - shifting land plates - might be possible. That's significant because plate tectonics on Earth drive a key mechanism for earthly life.

Evidence from the Voyager spacecraft reveals that the shape of our solar system is 'squashed.' Ed Stone, Chief Scientist of the Voyager Mission, told EarthSky that the sun creates a bubble around itself. He said that in August of 2007, Voyager 2 reached the edge of the bubble about a billion miles closer to the sun than Voyager 1 did in 2004.

Astronomers can figure out the mass of a star using a formula based on Kepler's Law. They can also deduce mass by analyzing a star's color.

The giant gas cloud measures 11,000 light-years long and 2,500 light-years wide, and it's moving toward the Milky Way at a speed of 150 miles every second.

The star that is the sun's new twin is called HD 101364 (or HIP 56948). Astronomers say it's almost identical to the sun. And that's interesting because our sun shines on a life-bearing planet. Stars like our sun are rare, according to astronomers. They account for only 4 percent of all stars in our Milky Way galaxy.

Astronomers have seen more evidence of dark matter, in a massive ghostly ring 5 billion light-years away. Astronomer Dan Coe said, "Dark matter is ghostly because it's everywhere in our universe. It's all around us. But we can't see it and we can't feel it. In fact, right now there might be a billion dark matter particles passing through your body every second."

NASA has searched for extraterrestrial life in our solar system. A 2007 report from the National Research Council recommended widening the search.

The "faint sun paradox" has to do with the relationship between the sun's size and Earth's climate.