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.

Will Earth survive an expanding sun? Let's take a look at the star V 391 Pegasi, 45,000 light-years away. It might reveal a possible future for our planet Earth.

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."

Fluorescent proteins move from the ocean to the lab. Read more in "Glow in the Light".

Scientists believe that Earth's water was brought here early in Earth's history. They think icy comets and asteroids bombarded the young Earth for hundreds of millions of years. According to astronomer Bob Kandel the impacts heated the ices, causing them to evaporate. Eventually there was so much water vapor in the atmosphere it would have rained out onto Earth's surface.

How does the media portray the deep sea, and how does this coincide with what scientists discover about it? Read more about perceptions of the deep sea.

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

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.

A recent study suggests that, by the 2080s, extreme summer warming in cities such as Chicago and Atlanta could hover above 100 degrees Fahrenheit. Read more.