The red giant phase is pretty crazy. The star's outer atmosphere can expand to hundreds of times its initial size; some projections of the Sun's future – due to start becoming a red giant in about 5 billion years or so – predict it could grow as large as out to the orbit of Mars, engulfing Mercury, Venus, and Earth in the process.

A small asteroid will join Earth's orbit around the sun for two months beginning Sunday, becoming a 'mini-moon.'

Earth's moon will soon have some company — a “mini moon.” The mini moon is actually an asteroid about the size of a school bus at 33 feet (10 meters). When it whizzes by Earth on Sunday, it will be temporarily trapped by our planet's gravity and orbit the globe — but only for about two months.