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2015: The Year of Dwarf Planets and Small Solar System Bodies

We’re currently living through a very exciting time in space exploration, with a small armada of robot space probes visiting previously unexplored corners of our solar system. Here’s just a few of the amazing discoveries we’ve made in the past few weeks.

New Horizons

New Horizons

This year sees us make close encounters with two of the largest dwarf planets, as New Horizons flies past Pluto for the first time, and Dawn continues to orbit the giant asteroid Ceres. All this as the Philae Lander continues to try to make contact with us from the surface of Comet 67P/Churyumov-Gerasimenko as its parent spacecraft Rosetta follows the comet around the Sun.

Each of these missions is very exciting in its own right, but to have all three happening at once is incredible.

Rosetta and Philae Latest

The Rosetta Orbiter arrived at Comet 67P/Churyumov-Gerasimenko in August last year, and the Philae lander descended onto the comet’s surface in November, carrying out its science mission for 60 hours before its batteries died. Rosetta has continued to produce great science since then; its latest scoop was the discovery of what appear to be sink-holes on the comet’s surface.

Sink Holes on Comet 67P

Sink Holes on Comet 67P

All this while Philae tries to make contact with us, and Comet 67P begins the outgassing that will eventually form its tail as the comet makes its closest approach to the Sun on 12 August 2015.

Comet 67P/Churyumov-Gerasimenko begins outgassing

Comet 67P/Churyumov-Gerasimenko begins outgassing

Dawn Latest

The Dawn spacecraft arrived at Ceres in March 2015, after having spent over a year orbiting the smaller asteroid Vesta. Ceres is the largest of the asteroids, so large in fact that it’s considered a dwarf planet, its gravity having pulled it into a spherical shape.

More and more mysteries are arising as a result of Dawn’s asteroid mission including: what are these bright patches inside craters on Ceres’ surface?

Bright spots in the surface of the Dwarf Planet Ceres

Bright spots in the surface of the Dwarf Planet Ceres

and: what’s a mountain doing on an asteroid?

A mountain on an asteroid

A mountain on an asteroid

New Horizons Latest

Stay tuned for even better images of Pluto as New Horizons speeds towards its 14 July flyby at close to 60000kph. For now the best images we have of Pluto and its moon Charon are from New Horizons’ Long-Range Reconnaissance Imager, which shows features on the surface of the distant Dwarf Planet, which we’ll see in better detail in the next couple of weeks.

Pluto and Charon, real colour

Pluto and Charon, real colour

Other Missions

This is on top of all of the other missions going on up in space right now: Cassini continues to send back breath-taking images and data from the ringed planet Saturn and its moons; no fewer than five spacecraft are currently in orbit around Mars – NASA’s 2001 Mars Odyssey, , Mars Reconnaissance Orbiter, and MAVEN, ESA’s Mars Express, and India’s Mangalyaan – while two intrepid rovers – Opportunity and Curiosity – explore Mars’ surface; and our own Moon is orbited by the Lunar Reconnaissance Orbiter.

We’ll add to this over the next few years, as the Juno probe reaches Jupiter in summer 2016, and as the Japanese mission Hayabusa 2 enters into orbit around an asteroid in 2018 and returns a sample to Earth on 2020.

Close Encounters with Asteroid 2005 YU55

November 8, 2011 Leave a comment

This evening (8 November 2011) at 2328 GMT a 400m diameter asteroid will hurtle past the Earth, missing us by an astronomical whisker, less than 200,000 miles. The chunk of space debris in question is snappily titled 2005 YU55.

Radar image of 2005 YU55 taken at 1945UT on 7 November 2011, when the asteroid was 1.38 million km away

This kind of asteroid fly-by is rather rare. The last time that something this size passed so close to us was in 1976, and the next time it’s due to happen (that we know of) is 2028. Still, tonight’s pass poses absolutely no risk to the Earth.

Asteroid 2005 YU55 was discovered, as its name suggests, is 2005. This designation method is used by the Minor Planet Center, and designates minor planets until a proper name is given (if ever). Upon discovery it became clear that this asteroid was one of the Apollo asteroids, near-Earth asteroids named after 1862 Apollo, the first of the group to be discovered. The Apollo asteroids are all Earth-crossing asteroids, and so warrant special attention. The fact that their orbits cross that of the Earth does not automatically mean they pose a threat of impact, but does mean that we need to very carefully monitor their orbits in case they are on a collision course with us in the future.

Astronomers rank near-Earth asteroids relative to the risk they pose to us using the Torino Impact Hazard Scale. This ten point scale runs from 0, meaning that “the likelihood of a collision is zero, or is so low as to be effectively zero”, to 10, meaning “a collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it”. 2005 YU55 is currently ranked at 0 in this scale. There are no asteroids currently known that are ranked higher than 1. The highest ranking ever given was 4, given briefly to asteroid Apophis, meaning “a close encounter, meriting attention by astronomers…[with] a 1% or greater chance of collision capable of regional devastation”, but this has since been downgraded to a 0 based on new observations refining its orbit.

Torino Scale

Asteroid 2005 YU55 will not be visible to the naked eye, but amateur astronomers with good telescopes, and knowledge of how to use them, might locate it. See Robin Scagell’s excellent description of how to find it over at the Society for Popular Astronomy.

If 2005 YU55 did hit the Earth (it won’t) it could certainly destroy a large city and cause significant loss of life (to find out what would happen head over to the Down 2 Earth Impact Simulator) which is just one of the reasons that asteroid observation projects are so important.

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