Weird Orbits

When I thought about getting somewhere in a spaceship as a 13 year old it seemed pretty simple – just point the ship in the right direction and hit the go button. Most SF seems to feature ships with plenty of power, certainly for interstellar travel it seemed a case of point and shoot.

But travel in the solar system is all about conserving the precious fuel. The latest navigational schemes are all about maximising the efficiency, usually at the expense of the time of travel. Of course we are talking robotic probes here, so preserving the human cargo is not an issue, just the patience of the organisation that sends the probe (and the engineers and scientists anxiously watching it do its thing).

When Apollo 11 went to the moon in 1969, it followed the Hohmann transfer orbit (see below).

 220px-Hohmann_transfer_orbit_svg

Relatively straightforward in concept, this basically takes the ship from one orbit to another orbit (1 to 3), with one half of an elliptical orbit (2) as the intermediate transfer step. This is nice and neat if you have high-thrust engines that can accelerate or decelerate (i.e. for going the other way) from orbit to orbit in a way that’s virtually instantaneous. In reality, you might have lower thrust, so the orbits are changed over a number of timed bursts, gradually increasing the orbit. These lower thrust manoeuvres require more Delta-v than the two thrust orbit transfer, however a high-efficiency low-thrust engine might be able to accomplish them with lower overall reaction mass. This is an advantage for small satellites where reducing the total fuel mass is critical.

The other alternative is to use the slingshot effect. The principle here is conservation of energy. The spaceship uses the gravity of a planet to increase its speed. The planet is slowed down by the smallest of margins, but for very little applied thrust the ship can pick up a real burst of speed. The Cassini probe used this approach when it journeyed to Saturn. It first set off toward the centre of the solar system undergoing two close encounters with Venus, then swung back past Earth and onto Jupiter before turning to Saturn. Again, like the Hohmann transfer that took us to the moon, this is all about swapping orbits via an intermediate orbit. What about just changing directly from one to the other?

There is another subtle approach that is being used to bring spacecraft to their destinations while using the lowest amount of fuel possible. This exploits strange regions of chaos that can occur in areas where the gravitational force of two (or more) bodies cancel out. The most well known of these are the Lagrange points in the Earth-Moon system, where I still imagine the O’Neill colonies spinning away.

This approach exploits the orbits that intersect with these ‘null’ points. Once inside the null point, a ship can apply a very low amount of fuel – and taking its time – cruise out of the zone and straight into a new orbit without having to blast away its fuel in a high-cost Hohmann transfer manoeuvre.

This scheme was used to bring the Japanese space probe Hiten back from Earth orbit to the Moon after it had all but run out of fuel. Edward Belbruno, an orbital analyst at JPL, came up with a scheme that allowed the probe to visit the Moon’s Trojan points (where gravity and centrifugal force cancel out) to examine cosmic dust. The scheme used the L1 Lagrange point.

Astronomers have observed a strange orbital network in the solar system where natural bodies take advantage of the ‘chaos’ in these null zone to swap orbits. One example is the comet Oterma, which was orbiting the sun in 1910, it changed orbit a few times, orbited Jupiter for a while, and then orbited the sun in a new orbit that brought inside the orbit of Jupiter. Then it had enough of that and went back to orbiting Jupiter again, then looped back outside the orbit of Jupiter to orbit the sun again (where it is now). Crazy but true.

Natural bodies seem to have a  propensity to ‘change stations’ at these cosmic transfer points. The strange thing is that these points are truly chaotic – there is no predicting what will happen if a body crosses into them. They might emerge in the same orbit, or into one fundamentally different. We can exploit these by forcing the change – using a precisely timed bit of thrust. Of course the down side is it takes longer.

Just think where we could travel in the solar system if some form of ‘suspended animation’ and the length of journey was not such an issue?

Nice to think of these natural orbital transfer points housing space colonies and tourist resorts. Maybe casinos?

Crowd Sourcing a Space Program – Mars One Colony & Asteroid Mining

Crowd sourcing of funds for new projects is an interesting development for any artist. The approach has been used quite successfully by many writers, although these writers already had a large following to begin with. To get an idea of how far this can go, have a look at musician Amanda Palmer’s ted.com talk The Art of Asking. It’s clear the sort of way-out extrovert/sociopathic personality you need to take this to an extreme – hell I couldn’t do it. But it is fascinating. And the possibilities are there.

What is also interesting is how this concept is being applied to the development of the space industry and also space exploration.

Aspiring asteroid miner Planetary Resources is developing a series of spacecraft designed to study solar-system asteroids. The company has just launched a crowd funding campaign to support the development of their Arkyd spacecraft. The deal is, if you donate, you get to use the Arkyd, including potentially directing the vehicle’s space telescope at your own objects of interest.

Planetary Resources aim to mine near-Earth asteroids for precious metals and water, both for use in space and also to supply Earth’s needs. The company has some high-profile support, including James Cameron and Google-man Larry Page.

 Planetary Resources have just launched a campaign to raise $1 million through public funding. They are waiting to see how much support they gather before deciding whether to also public-fund additional Arkyd spacecraft. For $25 you get a ‘space selfie’ a photo of an uploaded digital image of yourself taken against the background of the telescope in orbit. (Your image appears on a screen on the spacecraft, allowing your image to be in the shot). $99 buys 5 minutes of observation time, while for $150 you can point the telescope at any object of interest you choose and receive a digital copy of the Arkyd photo. That’s pretty cool. I wonder if they would let you drive it?

Explorers Mars One want to establish a permanent human settlement on Mars by 2023 – an ambitious timetable in anyone’s book. They recently opened for applications for colonists, so if you’re keen to leave the planet permanently, check out the site. While you’re at it, you can look at the profiles of the 80,000 people who have already applied.

Mars One do not intend to be technology developers, instead proposing to use a suite of existing/proven technologies under licence – such as Space X’s Falcon Heavy launcher, a lander envisaged as a variant of Space X’s Dragon capsule – as well as a Mars transit vehicle, rovers, suits, communications systems etc. They already have an impressive list of advisors and ambassadors for the project.

The Mars One model depends on revenue from donations, merchandising and from broadcasts leading up to the event that will focus on a 24/7 ‘Big Brother’ style converge of astronaut candidates. Opponents of Mars One’s approach compare the Mars One concept unfavourably to reality television, and believe the need for ratings will overshadow safety concerns. I wonder what happens when you get voted off the planet?

You can already by the Mars One T-shirt, coffee mug,  hoodie or poster.

What do you think about public-funded projects to get us off the rock? Is this an exciting or frightening development? Should space exploration be left to governments?

Juggling Molecules on Mars

So much of what we come into contact with is made of four elements – carbon, hydrogen, oxygen and nitrogen – the main elements of living systems. Add phosphorous and sulphur and you have what comprises 98% of all living systems.

The chemistry for juggling these four atoms – C, H, O, N – has been around for a long time.

Engineers and scientists have been confident enough in the chemistry and the various ways of manipulating them to propose various sets of reactions for use in gathering resources out in the vast reaches of space, as part of human exploration. This is part of a wider field of study called In Situ Resource Utilisation (ISRU), which has formed a key part of plans to explore other part of the solar system, particularly Mars, for the better part of two decades.

In the Mars Direct concept Robert Zubrin proposed using the well known Sabatier reaction:

CO2 + 4H2 => CH4 + 2 H2O

To react hydrogen with the Martian atmosphere to produce methane and water – very useful things to have on the red planet. The methane would be stored and kept for use as rocket fuel.

Methane and oxygen are a handy combination. In terms of chemical rocket propellant candidates, the Specific Impulse (Isp) of Methane and Oxygen at 3700 m/s is second only to Hydrogen and Oxygen at 4500 m/s (to convert to seconds of impulse multiply by 0.102).

Meanwhile the water from the Sabatier reaction would be split via very familiar electrolysis reaction:

2 H2O => 2H2 + O2

The idea was that only the hydrogen would need to be transported to the Red Plant. H2 weighs a lot less than CH4, freeing up space and payload for the 6 months transit to Mars.

Various test rigs were constructed on Earth, using analogues of the Martian atmosphere, which has been well characteristed since Viking. Mars has a lot of CO2 – more than 95% of the atmosphere – and a nice analogue of the Martion atmosphere right down to the low pressure could be similated for the rig. The CO2 is initially absorbed onto zeolite (an ever popular sorbent) under conditions simulating the Martian night. During the Martian ‘day’ the CO2 desorbs and passes into the Sabatier reaction vessel with the H2, which is heated to 300C. Reaction then occurs in the presence of the right catalyst (in this case pebbles of ruthenium on alumina). The water from the reaction is condensed out and passed to the electrolysis unit.

Still awake?

OK. Not surprisingly scientists and engineers planning Mars missions were concerned about overly complex systems forming such major part of a critical path.

Current plans for ISRU on Mars revolve around direct dissociation of the Martian atmosphere i.e.

2 CO2 => 2 CO + O2

[BTW if you could pull off this reaction at room temperature on Earth you would be an instant billionaire]

The current Mars Design Reference Mission proposes the production of oxygen on Mars through direct dissociation. Methane will be transported directly from Earth, with the ascent vehicle still using the tasty combination of methane and oxygen in its rocket engines.

So how is the CO2 pulled apart? There are many contenders, all of which uses a lot of energy. On Mars that energy is currently planned to be delivered by a 30 kW fission power system.

The front-runner for CO2 dissociation is thermal decomposition, followed by isolation of the O2 using a zirconia electrolytic membrane at high temperatures.

This system was developed for its first flight demonstration as the Oxygen Generator Subsystem (OGS) on the defunct Mars Surveyor Lander, which would have been launched in 2001 (but was cancelled following a string of Mars mission failures – Mars Climate Orbiter (1999), Mars Polar Lander (1999), Deep Space 2 Probes 2 (1999). That was a bad year. ).

The OGS was to demonstrate the production of oxygen from the Martian atmosphere using the zirconia solid-oxide oxygen generator hardware. This unit was designed to electrolyze CO2 at 750C (1382 F). The Yttria Stabilized zirconia material – once a voltage is applied across it – acts as a oxygen pump allowing the O2 to pass through it and be collected. The plan was to run the unit about ten times on the surface.

As I mentioned there were various contenders for the process. Such as molten carbonate cells, which operate around 550C with platinum electrodes immersed in a bulk reservoir of molten carbonate. Personally, the engineer in me shudders at the thought of trying to manage any sort of molten system that remotely.

The final system for CO2 decomposition used on Mars is probably still a work in progress. It will be interesting to see what develops there.

The fact is the initially proposed Sabatier reactions did not produce enough O2 to react with the methane, so some form of CO2 splitting process was still required.

So there are some things we can do to juggle molecules when we get to Mars.

Is everyone out there looking forward to getting to the Red Planet and grappling with what we find there? Who thinks we should not go? And why not?

Planet-Hunting Goes to the Next Level

This really is the age of planet-hunting. The number of confirmed exoplanets now exceeds 800, and there are more than 2,700 other candidates waiting for entry into the hall of fame. When you consider how far away some of these suckers are, it really is astounding.

Up until now we have been able to get estimates of orbit,  general size and mass. Combined with knowledge of star type, this has enabled astronomers to place the exoplanets in relation to the ‘Goldilocks’ or habitable zone, where liquid water is possible (seen as a likely precursor for the development of life (as we know it, Jim)).

Now the analysis of these targeted systems has gone to the next level. Astronomers are beginning to install infrared cameras on ground-based telescopes equipped with spectrographs. This will enable tell-tale signatures of key molecules to be detected. One key feature of this work is figuring out ways of blocking the glare of the planet’s adjacent star. NASAs planned James Webb Space Telescope will also use a similar strategy to study the atmospheres of planets a little bit bigger than Earth.

Two factors can improve the view. Young planets have more heat left over from their formation, increasing the infrared signal for the spectrographs. The other approach is to look at planets further out from their stars, helping to isolate their spectra from the star’s light. Of course looking that far out means starting with Jupiter-sized planets, but astronomers hope to be able to refine their technique to allow the atmospheric compositions of smaller – and older –planets to be examined.

The Holy Grail is finding an Earth-sized planet in the habitable zone with molecules that indicate the probable presence of life. We might have to wait for the proposed Terrestrial Planet Finder before we can crack this.

Still, it’s pretty exciting stuff!

Watching the Asteroids

Asteroids are always intriguing. Little planetoids that fly around the solar system in mysterious orbits, often swinging dangerously close to Earth. It’s that element of the unknown as well as the potential threat to life on Earth that always ensures their popularity.

There is a lot of work going on behind the scenes in modelling asteroid orbits and tracking them. The NASA Near-Earth Object Observations Program – dubbed Spaceguard – detects, tracks characterises both asteroids and comets passing by Earth (anything inside 28 million miles of Earth is regarded as Near-Earth). It uses both ground and space-based telescopes. This information is used to predict their paths, and to determine any potential hazard.  At any given moment some of the world’s most massive radar dishes are on the case.

A new space-based asteroid-hunting telescope is being planned. NASA scientists recently tested the Near-Earth Object Camera – a key instrument. That will be interesting to watch for, potentially doing for asteroids what Kepler did for planet-hunting.

One favourite way to get to know an asteroid is hitting it hard with another object (not recommended in personal relationships). Those collisions can tell us a lot about their structural integrity and composition. Trying to get that little probe to actually hit anything travelling at hypervelocity (11,000 km/h or above) is a feat in itself.

Knowing where an asteroid will be, and its structure and composition are vitally important things to know if we plan to move asteroids around or want to explore them for valuable materials.

Potential targets can be quite small – as tiny as 50 metres wide. One little-known complication of creating a scientifically significant impact is that they can also have their own little family of tiny moons orbiting around them. Trying to track down those secondary orbiting bodies can be a challenge, but critical to the success of any ultimate impact.

At least with asteroids you do not have the complication of jets of material firing into space, which you have with comets. These can upset imaging and guidance systems.

One likely candidate is the asteroid 1999 RQ36, which is the target of a NASA mission called OSIRIS-Rex. The currently slated launch date is September 2016, with the ‘landing’ in 2023 (now that’s long-term planning). Not only do the NASA scientists need to co-ordinate the impact, they have to ensure that the OSIRIS-REx spacecraft, with its crucial observing instruments, can monitor the results of the impact from a safe distance. This little craft will do a loop around Mars then close with its target at the rate of 49,000 km/h (8.4 mi/s). Needless to say mission scientists will be executing several deep space manoeuvres to refine its position during its approach. The spacecraft’s own automatic navigation system will take control only two hours from impact, executing three planned corrections at 90min, 30min and 3min from the impactor ‘landing’. At this point the spacecraft will be a mere 2,400 km away from RQ36. Cosmic spitting distance!

Two Spacecraft Crash into Moon Mountain!

Yes, really! But not by accident.

On December 17 2012, NASA’s twin GRAIL (Gravity Recovery and Interior Laboratory) spacecraft were steered into a mountain near the Moon’s north pole. Both were about the size of a washing machine with a mass of around 200 kg (440 lbs). The aim here was to squeeze one last bit of science out of the spacecraft and take a look at the Moon’s interior.

The crashes alone could not achieve that. The twin impacts created twin plumes, but another spacecraft had to be on hand to analyse what the nature of these implied for the Moon’s composition. In this case it was NASA’s Lunar Reconnaissance Orbiter (LRO).

In the case of the NASA team driving the LRO it was a mad scramble to get the spacecraft into position to observe the impacts. LRO’s team had only three weeks’ notice of the ultimate position of the two GRAIL’s resting places and had to make sure their baby was on hand to focus on the columns of ejecta.

LRO was about 160 km (100 mi) from the lunar surface when the two spacecraft made impact. Because the site was in shadow at the time of the impact the LRO had to wait until the plumes rose high enough to be in sunlight before making its observation. In this case, the LRO used the LAMP instrument (Lyman Alpha Mapping Project), which is an ultraviolet imaging spectrograph. The LAMP saw mercury and enhancements of atomic hydrogen in the plume.

The results are interesting because the presence of mercury was also noted from the LCROSS (Lunar Crater Observation and Sensing Satellite) impact in October 2009, however that impact was at the bottom of the Moon’s Cabeus crater, which has not seen sunlight in an estimated billion years and is likely to be quite cold.

Now two craters around 4-6m in diameter dot the side of the unnamed mountain at an elevation of around 700m above the surrounding plain, around a third of the way up the 2,500m tall massif. Each has a faint, dark ejecta pattern. The dark ejecta is unusual since  impact craters on the Moon are usually bright. One theory is that the dark pattern is a result of the spacecraft remnants being mixed with the local materials.

If Elon Musk can get the price of space travel down by his claimed factor of 100, then maybe I can send my old washing machine up to the Moon for a scientifically relevant impact. Now that would be something.

Who Shrank the Shuttle?

If you see a picture of the X-37B unmanned spaceplane, you would be forgiven for mistaking it for a slightly modified Space Shuttle. If you look closer you realise it’s a mini-version of a Shuttle, around 9m (29ft) in length and 5 tonnes (11,000 pounds), with a payload of your average pickup truck.

Here is a picture of it in its hanger [CREDIT: space.com].

 X-37B mini shuttle

Looks awesome. I like the V-shaped rear wings. Looking at this I’m thinking all that money spent in Shuttle development wasn’t as wasted as I thought.

Two have been built so far (reportedly), and one has been in orbit around Earth since December, although no one knows exactly what it’s doing up there.

The X-37B went into orbit on top of an Atlas 5 rocket from Florida’s Cape Canaveral on December 11 2012. The current mission is designated Orbital Test Vehicle-3 (OTV-3), as the third classified mission under the US Air Force’s X-37B program.

The little robotic vehicle is on the USAF’s books as USA-240.

The vehicle lands on a strip, just like its bigger (defunct) cousin, but even more impressively it does so autonomously. Pretty cool, huh? I thought maybe I could sneak into the back in a spacesuit for some spacewalking next time it goes up, but then realised I could never hope to pack enough oxy-mix – the little craft was up in orbit for 469 days for OTV-2. That’s a long time to hold your breath.

OTV-2 ended on a special strip at Vandenberg  on June 16 last year, although the jury is out as to whether OTV-3 will end there or back at the good old shuttle strip at Kennedy Space Centre.

Anyone heard anything about what the X-37B’s doing up there?

Astronomical Visitors – Hello 2012 DA14

Next Friday a 46m (151 feet) diameter asteroid is going to be making a fly-by of Earth. The microscopic aliens who inhabit the little world, roughly the mass of an aircraft carrier, have prepared their miniature cameras to get nice snaps of the weird ‘big people’ below as we go about our daily lives. We’ll be watching too.

The asteroid, poetically dubbed 2012 DA14 in accordance with the naming convention, will pass within 27,680 km (17,200 mi) of Earth. Geosynchronous orbit is at 36,000km, so this visitor will actually pass between the orbit of various GPS and TV satellites and Earth. NASA scientists assure there is no chance of collision.

It will zip past at around 27,000 km/h (17,500 mph), and should be visible through binoculars and telescopes.

The best viewing location will be Indonesia, but Australian watchers should get a pretty good view as well. It will be visible from around 0624 Australian Eastern Daylight Time (i.e. Sydney, Melbourne, Canberra etc) on February 16 – that 524am for us Brisbanites (that’s our Saturday morning). The asteroid should be visible as a small star moving against the background of stars.

A telescope at NASA’s Marshall Space Flight Center in Huntsville will broadcast its view of the event from 6pm to 9pm USA ET on February 15.

Conventional wisdom says that asteroids of around 50m in diameter pass by Earth every 40 years or so, but are only expected to impact the Earth around every 1200 years.

The asteroid is thought to be similar in size to the object that exploded over Tunguska, Siberia, in 1908. The shockwave levelled hundreds of square kilometres of forest. Whether an asteroid makes impact or detonates in mid-air is down to its composition. The Tunguska explosion was thought to result from a rocky asteroid, as opposed to more metallic asteroids that have more structural integrity and stay intact up to impact.

This is the closest approach on record to Earth for an asteroid of its size.

Observations from the fly-by will hopefully gives clues on the asteroid’s composition and structure.

Any plans to watch the asteroid fly past?

Slingshots and Cosmic Coincidences

It’s easy to get dizzy thinking of humanity reaching out into the Universe. Especially if you have a head full of space opera with FTL drives, wormholes and other ‘standard’ transportation techniques.

No wonder it feels disappointing in the extreme to watch the progress of us Earth-dwellers into the local space.

Our first steps into the solar system will be much along the lines of what has gone before. Chemical propulsion will likely remain the standard for planetary lift-off for some time to come. If we are lucky, perhaps we can satisfy the EPA and use Nuclear Thermal Rockets, which might double the available impulse. Reentry will remain much more economical with technology used since the space race – i.e. heat shields and parachutes – while space vehicles of the like of the Shuttle will retire to museums.

When it comes to getting around the solar system, again we will probably be relying on chemical propulsion – all the currently proposed manned Mars missions are based on this. Again NTR rockets may offer potential in the future if the safety concerns can be addressed. For missions where time is not no much of an issue, electric rockets (ion drives) with their highly respectable exit velocity of 30 kilometers per second are capable of bringing spacecraft to high interplanetary velocities (but their low thrust means they will never get us to orbit).

Here’s where the slingshot manoeuvres come in. These have been used to great success in the early interplanetary probes such as the Voyagers. Basically, these rely on the principle of conservation of momentum. The same principle as slamming a cue ball into a billiard ball to get the billiard ball in the pocket. The momentum is transferred from the cue ball into the billiard ball but the momentum of the whole system stays the same. In this case it is the angular momentum of the two bodies movement around the sun that is conserved. The tiny spaceship takes a low trajectory over a big planet like Jupiter, and is shot out of the planet’s gravitational field at ninety degrees to its original direction of travel. The spaceship is now on a new trajectory that does not centre on the sun, and its angular velocity has increased by the same amount as Jupiter’s Sun-orbital velocity of 13 kilometers per second (while Jupiter’s angular momentum decreases by a minuscule amount).

Voyager 1 used a gravity slingshot manoeuvre to get to its present velocity of 17 kilometers per second. (Try not to think about the fact that it would take 70,000 years at this speed to reach our closest stellar neighbours.)

If a spaceship can apply thrust during a slingshot manoeuvre it can capitalise on the orbital mechanics even further. If a probe approaches the sun within 1.5 million kilometers along a parabolic solar orbit, then increases its velocity by 2 kilometers per second, it will leave the Solar System at an impressive 41 kilometers per second.

NASA’s Mariner 10, which performed flybys of Mercury in 1974 and 1975 relied on Venus gravity-assist manoeuvres to get it into position.

The Messenger probe to Mercury – the first probe to visit the planet in 30 years – went into orbit around Mercury on the 18th March 2011. It was the first space craft ever to do so. So far its found significant water in the planet’s exosphere, evidence of past volanic activity and evidence for a liquid planetary core. To get some idea of the crazy orbital scheme required to get it there, here is a diagram of its journey since launch.

Messenger Since Launch
Talking about cosmic coincidences, has anyone noticed that the gravity of both Mars and Mercury is 38% of Earth standard? I had to check that twice. Given the fact that Mercury may have water in its dark side craters (its tidally locked), it makes you think of the possibilities.

The other one that always gets me is that both the Moon and the Sun are exactly the same angular size in the sky.

What other cosmic coincidences have you noticed?

Weird Planets

exoplanet

This year has produced some amazing discoveries in the planet-hunting arena.

Notable among these is the announcements of more ‘super-Earths’.

The planet HD 40307g is the most distant from its sun of six planets found in its system, and takes 200 days to orbits its star. At seven times Earth-mass, bets are on as to whether this planet is rocky or a Neptune-like world. Astronomers put it at about 50:50. The system is around 42 lightyears away. Not only does it orbit in a habitable zone, the target system is also close enough to potentially image directly in the future using the next generation of space-based telescopes. Bring it on!

Gilese 163c is another planet in its stars habitable zone, also estimated at seven times the mass of the Earth. The planet orbits a red dwarf slightly dimmer than old Sol and zips around it in 26 days [red dwarfs are the most common star type in the Milky Way].

Other discoveries showed planets where you least expect to find them – in multiple star systems. Solving multiple-body problems like that give even the most brilliant mathematicians a severe headache. But that does not stop us from seeing what’s out there.

The gas giant PH1orbits a pair of stars that are part of a four-star system [in this case it would orbit the centre of mass of the two stars]. The first planet found in a four-star system. It is bigger than Neptune, and easily big enough to host rocky moons approaching Earth-size. Unfortunately its location makes it too hot for liquid water – its temperature is estimated to range between 251C to 340C (484-644F).

The best thing about PH1 is that it was discovered by two amateur astronomers as part of the Planet Hunters program. So non-professionals get to play too!

A number of binary systems with planets have now been found, some with planets near the habitable zone, such as Kepler-34b and Kepler 35b. Each would get that double-star sunrise, just like Tatooine. Both planets are big, and around 5000 lightyears from Earth. So no exploring just yet.

As for the closest planet, that is a rocky planet orbiting Alpha Centauri B, 4.2 lightyears from Earth. No need to pack the swimsuit – unless you like doing laps in lava. It orbits its sun in a little over 3 days at a distance one tenth of Mercury’s orbit. Ouch.

Find more info and some good pics here.

What were your favourite discoveries of the year?