Sunday, 8 March 2015

NASA's Dawn mission arrives at Ceres

Exciting news this weekend from NASA's Dawn mission, which went into orbit around the dwarf planet Ceres after a successful orbital manoeuvre. It became the first ever man-made satellite to orbit a dwarf planet, and only the seventh planet of any sort to achieve such status.

Two views of the dwarf planet Ceres, as seen by NASA's Dawn mission as it went into orbit around
the dwarf planet on Friday (Credit: NASA)

Ceres, named after the Roman god of farming, was discovered on New Year's Day 1801 by Giuseppi Piazzi, and at the time was the 6th celestial planet to be discovered. A few years later another planetary body was discovered in the same region and named Pallas.

These two objects were noted by astronomers to be significantly smaller than the other planets and could not be resolved into a disc like the other planets, even with the best telescopes of the day (Ceres itself is less than 1000 km wide, a fraction of the size of our Moon). Because of this, Sir William Herschel proposed in 1802 that these two objects be re-labelled as asteroids, from the Greek meaning star-like.

Many more asteroids were discovered in the same region of space throughout the 19th century leading to the idea that these asteroids were distributed in a ring between the orbits of Mars and Jupiter, a ring which came to be known as the asteroid belt. Ceres, which is sometimes referred to as a dwarf planet, is the largest object in the asteroid belt, composing approximately a third of the total mass of all the objects in the asteroid belt. Ceres could therefore be very important for understanding the origin of the asteroid belt and for learning more about how our Solar System formed.

Now the Dawn Mission is in orbit around Ceres we can expect some beautiful images and many interesting scientific discoveries in the near future, hopefully starting with some explanation of what that bright white spot on the surface of Ceres is.

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