Betelgeuse, a bright reddish star in the constellation Orion. It is about 495 light-years from the earth, though some measurements put it at about 640 light-years away. Its color indicates a relatively low surface temperature of about 5,000° F. (2,800° C.), about half that of the sun. Betelgeuse is a variable star that fluctuates irregularly in size and brightness. At its smallest, Betelgeuse has a diameter some 300 times that of the sun; its greatest diameter is about one-third larger than this. Betelgeuse is classified in the group of largest known stars, the supergiants.
Since the 19th century, humans have wondered about the prospect of life on Mars. While we haven't sent anyone to the Martian surface, we have sent spacecrafts, which have gathered a good amount of information on what it's like on Mars. How is it different from Earth? How is it similar? And could life really have existed there long ago, or exist in the future?
Neptune is the eighth planet from the sun, the fourth largest, and a gas planet. It is named after the Roman god of the sea. Neptune is four times the size of Earth, and its day lasts a little more than16 hours. Its year is about 165 Earth years. Neptune's orbit is a perfect circle. The last stop on spacecraft Voyager's epic trip through the solar system was the gas giant Neptune.