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Moon and Jupiter
The Moon and the planet Jupiter keep close company tonight. Jupiter looks like a brilliant star quite close to the left or upper left of the Moon as they climb into good view in mid evening. And Regulus, the brightest star of Leo, is not far to their lower left.
Jupiter is the largest planet in the solar system — about 80 times the diameter of the Moon.
Over the next few months, we’ll get our first good looks at some worlds that are smaller than the Moon — two of the solar system’s “dwarf planets.”
First up is Ceres, the largest member of the asteroid belt. The Dawn spacecraft is scheduled to enter orbit around it in early March.
Water seems to have played an important role in the history of Ceres. Much of its surface consists of clays, which form in the presence of liquid water. And a space telescope found water vapor around Ceres. That suggests that liquid water still pools below the surface, and squirts into space through cracks in the crust.
Not long after Dawn settles into orbit, the New Horizons spacecraft will be turning its cameras toward its target, Pluto. The craft is scheduled to fly just a few thousand miles above Pluto in July.
Despite its small stature, Pluto is a complicated system. It has a moon that’s about half its own size, plus four smaller moons. And its thin atmosphere may be starting to freeze out, forming a layer of fresh ice on this tiny but popular world.
More about dwarf planets tomorrow.