Now, let’s put the audacity of this venture in perspective. Exomoons are pretty much invisible in radial velocity (or Doppler Wobble) measurements, unless you have a superhuman spectrograph that’s absurdly sensitive to minute shifts in velocity. The best way to detect them is via transits (hence the current attempt to use Kepler). You’re unlikely to “see” the moon itself. What you’re more likely to see is the host exoplanet’s transits “wobbling”, as the moon tugs on the planet (see pic below).

Diagram of the star-planet-moon system (moon not shown, taken from Kipping 2009)

The first type of “wobble” is referred to as Transit Timing Variation (TTV), where the period of the transit (i.e. the time interval between two transits) changes with a well-defined sine curve. The second is Transit Duration Variation (TDV), where the length of time a single transit takes changes.

TTV is pretty good, but it is degenerate: this means that it can only measure the exomoon mass and orbital radius as a combined entity, not separately. TDV is also degenerate in a similar way, but measuring both signals together allows scientists to disentangle mass and orbital radius. Transit variations can be used to detect non-transiting planets in the same system as transiting planets, but this has never been achieved for exomoons.

HEK will perform an automated analysis of all planet candidates found by Kepler (over 2300 at last count), and search for positive detections. Even the null detections will allow an estimation of what fraction of exoplanets have a massive moon, which will be an important value for planet formation theorists to understand and explain.

The HEK project is likely to be our best shot of achieving exomoon detection. We expect Kepler to be able to detect exomoons down to about 0.2 Earth Masses. These are pretty massive moons compared to the Solar System (for comparison, Jupiter’s most massive moon, Ganymede, is 0.025 Earth masses), but detecting such a tiny object at such large distances would be a triumph of modern astronomy.

Lastly, I should note that the HEK paper is headed up by none other than David Kipping, who is a friend and colleague (we began our PhDs in the same year). I look forward to seeing his name pasted across the papers when the first exomoon is detected!

Image Credit: NASA/Ames/JPL-Caltech

Details on the Kepler-22 system are frustrating thin – it’s too soon for the data to appear in the web archives such as exoplanet encyclopaedia, so we have to rely on the scraps of data that appear in the press release.

Kepler detects exoplanets via transits (where the planet eclipses its parent star, and the starlight dips in intensity).  Because of this, Kepler measures the area of the planet, relative to the star’s area.  As the star is a typical G type (like our Sun), the team can calculate the absolute size of the planet, which has a radius about 2.4 times that of Earth (the above graphic shows the planets approximately to scale – you can see how Kepler-22b dominates over the others).  They can also measure the period of the orbit, which is about 290 days (cf Venus, whose orbit is 224 days).  This might seem like bad news for Kepler-22b-ites, but thankfully the star, Kepler-22, is about 25% less luminous than the Sun.  If we placed Earth where Kepler-22b is, the temperature would (apparently) be a rather nice 22 degrees Celsius.

But remember that Kepler-22b has a radius 2.4 times the Earth’s.  If it has a similar chemical composition, the mass of Kepler-22b could be about 14 times the mass of Earth.  Surprisingly, this still makes it quite a low-mass planet – a Super-Earth – and this value is probably an upper limit.  Without any knowledge of the planet’s composition, scientists will have to guess its mass.

The only way we’ll be able to confirm the mass of this planet is to carry out a follow-up survey, using radial velocity (or Doppler Wobble) techniques. These directly probe the gravitational forces in the system, and by extension the masses.  And it just so happens that Edinburgh University is part of the HARPS North consortium, which plans to build an instrument to do just that.

The Telescopio Nazionale Galileo in the Canary Islands, destination of the HARPS-North instrument (Source: University of St. Andrews)

The Kepler Space Telescope is ploughing an exciting furrow in exoplanet research, and telescopes like the one above will be following in its path, honing and refining its discoveries.  HARPS-North will certainly be in demand: after all, I doubt this is the last habitable planet that Kepler will see.  They have 54 candidate habitable planets still in the pipeline, awaiting confirmation, and that list can only grow.  We’ve never been closer to seeing our sister world in the skies, and we’re about to get closer still.

I’ve been pretty ambivalent about the whole thing, to be honest.  I think the reason I haven’t been able to come to a conclusion about them is because of how nebulous the whole thing is.  Apart from the admittedly pithy “we are the 99%”, I haven’t been able to divine the purpose of #OWS.

Historians will definitely remember 2011 as the year of protests.  The Arab Spring has changed the face of political discourse, and reignited the passions of disaffected youth.  Even now, the recent events in Egypt suggest a second revolution in nine months, as the military begins to cave to sheer force of civil will.  Kindled by all this fervour, economic catastrophe has compelled many to protest the actions of bailed-out banks and corporations, and to generally express anger about the machinations of modern capitalism.

And of course, the conservatives bared their teeth immediately (surprised?).  The recent horrible events at UC Davis have shocked the world, but left Fox News commentator Megyn Kelly thoroughly unimpressed, claiming that pepper spray is merely “a food product”.  Wikipedia describes the effects of pepper spray thus:

For individuals not previously exposed to OC [pepper spray] effects, the general feelings after being sprayed can be best likened to being “set alight”. The initial reaction should the spray be directed at the face, is the completely involuntary closing of the eyes (sometimes described as leading to a disconcerting sensation of the eyelids “bubbling and boiling” as the chemical acts on the skin), an instant sensation of the restriction of the airways and the general feeling of sudden and intense, searing pain about the face, nose and throat. Coughing almost always follows the initial spray.

Subsequent breaths through the nose or mouth leads to ingestion of the chemical, which feeds the feeling of choking. Police are trained to repeatedly instruct the target to “breathe normally” if they complain of difficulty, as the shock of the exposure can generate considerable panic as opposed to actual physical symptoms.

The burning reaction lasts, in some cases, for up to 4 hours. Intense headaches can result in some situations. On occasion seasoned offenders have complied immediately after production of OC spray cannisters, often requesting TASER usage as opposed to OC spray usage due to total time of effects.

Yummy.  Fancy some on your pizza, Megyn?

But I digress.  And it’s difficult not to – this whole thing is getting incredibly visceral.  Claims that a pregnant woman miscarried as a result of police aggression make the whole thing even harder to consider rationally.

And all the while the issues that sparked the movement continue to simmer under the surface of stories like these.  The eurozone teeters, its members and interested parties jettisoning cash at an incredible rate to keep the ship of seventeen states afloat (essentially plugging its holes with taxpayer’s money).  The whole situation seems a bit like a jalopy with the brakes cut and twenty hands on the steering wheel.

Yeah, I feel like yelling too.  But even that won’t make me go to St. Andrews Square and join the Occupy Edinburgh protesters.  The aims are unclear, apart from “we don’t like what is currently happening”.

The protests most successful in bringing about change had well-defined aims.  We knew very well what Martin Luther King meant when he said “I have a dream”.  Even the protests that coalesced around Hu Yaobang’s death had a clear purpose when the tanks faced a man with a shopping bag in Tianamen Square.

Human beings respond strongly to figureheads, whether it’s MLK’s inspirational speech or Herman Cain saying something unbelievably obtuse (or perhaps just plain dumb) about #OWS.  I wonder if what this movement needs is an individual around which it can nucleate, and take truly solid form.  I might be able to get on board if I saw the movement had clear leadership and direction.  As a secondary effect, the movement might develop a more concrete set of beliefs and policies.  Yes, the current economic situation is unfair, and in many ways isn’t even capitalism (corruption at the highest levels was certainly not Adam Smith’s idea of an invisible hand).  But how to change it? There’s a lot of problems to fix, and the system is toxic all the way up.

A political movement needs a clear set of policies.  And I would love to hear what the Occupy movement has to say.

My thought is this: to design such a steady state, which will depend strongly on demographic changes and economic turbulence, surely simulations of the system are needed.

I’m thinking about developing an agent-based simulation of the academic career progression (if Ken is reading, it won’t be during office hours!), but I’m interested in canvassing opinion. Is this a good idea? What variables would need to be tracked – gender, age, relationship status?

Feel free to tweet me or leave a comment – I look forward to hearing your suggestions!

I’ve decided instead to share with you a little nugget of news that might not have gone very far, about Scotland’s internet status.  There have been fresh efforts to lobby for a .scot web domain, led mainly by the Dot Scot Registry, with the backing of the Scottish Government (the UK government is considering whether to support the bid).  The Dot Scot Registry has been lobbying for this since its inception in 2009, and a golden opportunity is fast approaching.

The International Corporation for Assigned Names and Numbers (Icann) is a not-for-profit corporation which controls the naming system of websites, in particular controlling the top level domains (such as .com).  In January 2012, they will be hearing suggestions for new top level domains, partly in response to the massive growth of the Internet outside the Anglosphere.  This is no small increase – the current total is 22, and the expectation is that this number will increase to several hundred.

Critics of the campaign have argued that the real issue for Scotland is connectivity, not domains.  There are still large swathes of the country without access to broadband, and improving this is an important milestone for Scottish commerce.  Focusing efforts on a name seems like focusing on the wrong problem.  Having said that, there is still a good case for rebranding – it would certainly lend an air of credibility to the country’s online presence.  After all, if Antarctica and Liechtenstein have their own domains, why not Scotland? A country that generates £4bn a year in tourism revenues needs to have well crafted websites with a memorable name – www.tourism.scot does have a nice ring to it.

But it’s not all that simple.  Icann aren’t just giving these things away.  Prospective bidders will have to prove that they are worth the domain – they need to have well-established IT capabilities, a legal system that deals with intellectual property correctly, and sufficient manpower to track down and remove abusive pages (although what abusive means in this context isn’t clear to me).

In the end, I’m not sure how much all this change would really affect me.  It would be quite nice to host this blog on a .scot domain.  That is, if I’ve not forced enough Scottishness down your throat…

Schematic of the Kepler-16 system (taken from Doyle et al 2011, Science, in press)

The discovery of such an unusual system illustrates the progress of planet detection.  Detecting a planetary transit signal amongst the din of stellar transit signals (after all, star A will transit star B and vice versa) is a real achievement, and a testament to the Kepler instrumentation.  With the Extreme Solar Systems conference taking place this past week, we’ve seen a whole raft of announcements about planet discoveries.  The HARPS team have announced an interesting crop of 50 exoplanets, with a surprisingly large fraction of Super-Earths in the mix.  We’ve also had the recent discovery of the controversial “diamond planet“, which is most likely a stellar remnant rather than a bona fide planet.  This doesn’t make the discovery any less exciting – after all, this planet is probably the core of a white dwarf with its atmosphere stripped away, something we’ve never seen in the wild before.  Any details we can glean from this gives us vital forensic evidence regarding the last stages of a star’s life.

All these milestones edge us closer to the Holy Grail of planet detection – an Earth analogue, orbiting a solar type star in the habitable zone.  We’re still not quite there yet, but each of these unusual discoveries sharpens our tools (both instrumental and theoretical), bringing us closer to seeing the first of our planet’s cousins.

Craziness aside, there are two salient points we can draw from what is almost certainly a publicity stunt:

1) Private investment (alongside government funding) is probably necessary if we want a permanent presence on the Moon.  It’s definitely a good thing – look at the Panama Canal (an example I’ve cited before in a paper about another crazy expensive scheme).  We’re already seeing a budding private space industry in attempts to build astronaut taxis for the ISS – setting up lunar colonies would be the ultimate high-hanging, game-changing fruit for such an industry.

2) Permanent presences are all about the infrastructure.  We’ve been able to send capsules to the Moon in the past, but they haven’t been able to stay very long.  Apollo 17 was only able to remain on the lunar surface for a couple of days.  Staying for any length of time requires supply chains to be set up, either by exploiting resources available on the Moon or frequent deliveries from Earth, such as the ISS gets (or doesn’t get, as the case may be).  Setting a target like being able to run restaurants on a lifeless rock is one way to focus on solving fundamental logistical problems relating to living on other planets.  Let’s face it, if you can make pizza on the Moon, what can’t you do?

OK, so this is not going to happen anytime soon.  Domino’s Japan apparently only has about $5m in capital, so they’ll not be funding a moonshot at $21 billion (not factoring in ballooning project management costs, as Edinburgh residents know all too painfully).  What I think is important about ideas like this is that they assume that future humans will regard inhabiting the Moon as an everyday occurrence, just as Europeans view inhabiting North America as normal.

So normal in fact, that they’ll demand that desirable lunar residences have good amenities nearby.  Fair enough, not everyone wants Domino’s down the road, but they’ll want some breed of restaurant.  And the latest fashions, Apple products, Internet access, the whole nine yards.  The first colonists will not live on a Moon of all mod cons, but if human history is anything to go by, then one day their descendants will.  In a time where space exploration is at a particularly low ebb, it’s nice to know that the dream is being kept alive – even if it is for PR reasons.

Credit: NASA (Viking 1)

Well, let’s find out.  The distance to the horizon d is

R is the radius of Mars (3,396 km) and h is the height of the observer in the canyon (6 feet, say).  Plugging in the numbers gives the distance as about 3.5 km, way less than the canyon’s width.  Even on Earth, the horizon distance is only about 5 km, so a Marineris-sized canyon would be invisible to us here too.  In fact, if you wanted to just be able to make out the canyon face (assuming an infinitely clear day of course), the planet you were standing on would have to be about 2 million kilometres in radius! That’s about 4 times the radius of the Sun! As you can see from the scale model (left), that is very, very big.  Indeed, it’d be very unlikely that a terrestrial planet of that size could ever exist in the Universe (not least because gathering up that much rocky material is very difficult).  So Marineris truly is an invisible valley – and at 7 km deep (i.e. 7 El Capitans high), quite a challenge for any would-be extraterrestrial climbers.

Credit: NASA (Viking 1)

The rift is extremely visible from space, but is it visible from inside the canyon itself?  In canyons on Earth, it’s reasonably straightforward to confirm that you are in fact in a canyon.  One quick glance at the cliff face on either side of you will ensure you are well informed.  But what about Marineris?

At lunch, a colleague informed me that Marineris is so wide, that if you stood in the centre of the canyon, the curvature of Mars hides the cliff faces on both sides.  In effect, you would think you were standing on a relatively featureless plain, with the canyon walls safely hidden behind the horizon.  A pretty extravagant claim, no?  You can answer this question for sure with some simple geometry, as long as you know the depth (7km) and width (200km) of the canyon, and the radius of Mars (which is 3,396 km).  I could tell you the answer now, but I’m interested in what you think.  So let’s put it to the vote:

I’ll let you know the answer next week!

First off, let’s talk about my friend David Kipping’s latest work on the darkest world ever discovered.  They used data from the Kepler Space Telescope to study the Jupiter type planet TrES-2b.  Watching how the light from the star varies as the planet moves around and behind the star allows them to measure how much light the planet itself is either emitting or reflecting both at “day” and at “night”.  They find that this world is very dark indeed – the albedo (or what fraction of starlight is reflected by the planet) is less than 1% .  Just to compare, Earth reflects around 30% of the Sun’s light in the non-ice regions.

Artist's impression of the Darkest Planet

As David says, this makes the planet “blacker than coal”.  A well roasted planet, its surface temperature is 1200C  – partly because of its extremely low albedo, but also because it’s about 300 times closer to its star than Earth is to the Sun.  How could it be so black? Probably some exotic chemistry is at work, but we’ll need to revisit this system with more upcoming Kepler data to be sure.

Back on the less weird side of things, the HARPS (High Accuracy Radial Velocity Planetary Search) project has made some exciting discoveries of very low mass planets (ranging from 2.7 to 4.8 Earth masses) around sunlike stars.  While these are all a little closer to their stars than Earth is (about 0.13 to 0.4 times the Earth-Sun distance), one in particular (the snazzily named HD 85512b) is an extremely good candidate for habitability, provided it has at least 50% cloud cover.  In fact, the authors of another paper on the subject say that

HD 85512 b is…[one of ] the best candidates for exploring habitability to date, a planet on the edge of habitability.

The Telescopio Nazionale Galileo in the Canary Islands, destination of the HARPS-North instrument (Source: University of St. Andrews)

Very exciting! Even more exciting is that Edinburgh is now a member of the HARPS-North collaboration, which will be attempting to make similar discoveries in the Northern Hemisphere of the sky.  It will be able to study the same patch of sky that Kepler is looking at right now, and allow us to confirm and hone their discoveries.  One day, I’ll hopefully be writing a PlanetWatch with an amazing planet discovery from Edinburgh astronomers!