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.

In 2007, a Penn State astronomer led a team that discovered an extrasolar planet around a red giant star. The star is HD 17092, located 300 light-years away in the direction of the constellation Perseus. Earth & Sky interviewed this astronomer.

Queen's Brian May told Earth & Sky, "I think that rock stars could be accused of losing their sense of perspective quite often. And this keeps me with one foot in a different kind of world, where it's necessary to be very humble."

Rock star Brian May is the guitarist for Queen. He's also co-author of a book about the other kind of stars. It's called, "Bang! The Complete History of the Universe."

Is our universe shaped like a sphere, a saddle, or flat? It depends on how you look at it. That will tell us if the universe is open or closed. Read more here.