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.

Where stars form

Yesterday we were treated to a stunning image on the Astronomy Picture of the Day website, which showed off one of the regions in our galaxy where stars are in the process of forming. The image is shown below in infrared light, using data from NASA's Spitzer Space Telescope.

The W33 star forming region as seen in infrared light (Credit: NASA / Spitzer Space Telescope)

This region is called W33, so called because it was the 33rd object catalogued by Gart Westerhout in his survey of radio sources in our Galaxy. Many of the sources catalogued by Westerhout are regions in which stars are forming, such as this one.

Astronomers refer to these regions as massive star forming regions, not just because they are massive (this image is about 100 light years wide!), but also because they are the sites where massive stars are forming. Massive stars are the hottest and most luminous stars that exist, and they play an important role in how a galaxy evolves thanks to their luminosity, the strong winds that emanate from their surfaces, and the supernova explosions in which they end their lives.

For these reasons, and because of their short lives and inherent rarity, massive stars are important objects to study. Furthermore astronomers aren't entirely sure how they form, so regions such as this where massive stars are known to be forming, are important to study.

Ever wanted to name something in astronomy?

Have you ever wanted to name a star? Or a planet? Or maybe a whole galaxy? Maybe you paid someone to name a star for you and even received an offical-looking certificate in the post to prove it, only to then find out that no-one actually used your name.

Well if this sounds familiar, then I have some good news for you! The International Astronomical Union (IAU) has launched a competition to officially decide names for five new impact craters discovered on the planet Mercury, and they need your help to do this!

A map of Mercury's surface taken by the MESSENGER spacecraft, showing all the impact craters (Credit: NASA)

The impact craters were discovered by NASA's MESSENGER spacecraft, which has been orbiting the planet Mercury since March 2011. The spacecraft is only the second mission to successfully reach Mercury, and is the first to orbit the planet, which is quite an achievement due to how close Mercury is to the Sun!

The mission has been an immense success. Since the spacecraft arrived in orbit around Mercury four years ago it has been continually studying and imaging the planet's surface. Using these images scientists have discovered many new features on the surface of Mercury that were previously unknown, including lots of new impact craters.

It is important that these craters, which are of great scientific interest, be named in the long-held tradition of naming astronomical objects and features. Impact craters on Mercury are traditionally named after important people in the arts and humanities from anywhere in the world.

So the IAU would like your help in nominating who to name these craters after. According to their rules they will accept nominations for names of people in the arts and humanities who have been famous for at least 50 years and have been dead for at least 3 years (so no self-nominations unfortunately). You can find a list of existing named craters on Mercury here.

You can submit your nomination here: http://namecraters.carnegiescience.edu. Nominations are open until 15 January 2015.