We choose to do these things because they are hard

In 1962 John F Kennedy made what is probably the iconic speech on space travel,

One of the key points in the speech was answering “why go to the Moon?”,

“But why, some say, the moon? Why choose this as our goal? And they may well ask why climb the highest mountain? Why, 35 years ago, fly the Atlantic? Why does Rice play Texas? We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too”

Today I was thinking about this speech and I thought, how many times have these hard things been done since then. Well here’s the answer,

Slide1

Sources, flights (I couldn’t find long-term historical traffic data), Everest (-9 ascents pre1962), Rice vs Texas. For the non-Americans the last example was because the speech was made at Rice University and every few years Rice plays the University of Texas, a school 16 times its size, at American football.

And if you think it’s bad for Rice try being a Hawaii Rainbow Warriors (7-28 last 3 seasons) fan like me.


Henderson, the first distance to a star and Scottish confidence

One hundred and seventy five years ago a Scottish astronomer published the result that he would become famous for. Unfortunately it was the timing of the result that was the most note-worthy thing.

Thomas Henderson didn’t follow what we would now consider a typical astronomical career. He started out in Dundee as an apprentice to a lawyer. Six years later he moved to Edinburgh to further his law studies eventually becoming secretary to the Lord Advocate (similar to the Attorney General in other countries). All the while Henderson had been developing his astronomical hobby, focussing on computational methods. It was his brilliance in this that resulted in him determining more accurate methods to work out the timing of the Moon’s passage infront of stars. This calcualtion brought him to the attention of Thomas Young who at the time was running the Naval Almanac Office, in-charge of accurately calculating the timing of astronomical events. He applied for a job at the Almanac Office after a posthumous reccomendation by Young but was turned down. He was also turned down for a job at Edinburgh University around this time. Henderson then took a job working at the Cape Observatory (yes, he had to move halfway round the world to stay in astronomy, how modern). He spent a year there, working ridiculous hours making a massive number of astronomical observations. This appears to have burnt him out and he moved back to Edinburgh to become the first Astronomer Royal for Scotland. But he brought back with him the dataset that would see his name go down in history.
The distance to stars can be pretty hard to measure. While the noted astronomers of antiquity had noted “the fixed stars” as opposed to the wandering planets, by Henderson’s time it was understood that stars moved slowly across the sky. This indicated that the stars weren’t infinitely far away and (due to its high motion) that Alpha Centauri was probably quite close. The best way to estimate the distance to a star is using trigonometric parallax, taking advantage of the subtle changes in the point of view a star is observed from at different stages in the Earth’s orbit.
This first step on the stellar distance ladder became one of the big science goals of the mid-19th century. Henderson was one of the best in the world in astronomical calculations and soon after returning from the Cape, he had noticed an oscillation in the position of Alpha Centauri. This was about an arcsecond, roughly the size of a Coke can viewed 440km away. This made Alpha Centauri about 3.25 light years away (compared to the true distance of 4.4 light years). However Henderson wasn’t sure, he thought his instrument may be suspect so he waited for more observations from the Cape to confirm his results. Unfortunately his lack of confidence bit him, he was beaten to the first parallax measurement by the Prussian astronomer Friedrich Wilhelm Bessel nipped in and measured the parallax of another fast-moving star 61 Cygni in 1838, two months before Henderson’s publication.
Henderson’s lack of confidence may have stemmed from previous parallax measurements which were later shown to be nonsense. However it may have stemmed from the inherent lack of confidence Scots have. Scottish people are among the least confident in the developed world, Scottish satire writers pick “Lloyd, I’m ready to be heartbroken” to sum up the Scottish national football team. Perhaps the best summation of this is Gordon McIntyre’s, “I hate the way we expect to fail, and then we fail, and then we get bitter because we fail.” A nation defined by glorious failure, shy about its history of discovery, doesn’t produce risk takers.All that said, if I’d have been in Henderson’s position, I would have done the same. We’ve all seen massive “discioveries” knocked down by data released soon after and in science it should be more important to be right than to be first at all costs.


World Cup heat, maybe not such a factor

So far in this World Cup we’ve been hearing that the heat in Brazil is responsible for a series of massive upsets and for the generally high number of goals scored in the tournament so far. In addition the old mantra of “European teams can’t play in the heat” has been trotted out. I decided to do a very rough analysis on the group games in the tournament to see if I could find any statistical evidence that any of this was true. Firstly I tabulated all the results from the group games and added the relative humidity and temperature from FIFA’s own match reports. For one match (England vs Italy) I couldn’t find a FIFA number for the humidity so I took it from a number of match reports in the press. As well as who won each game and how many goals were scored I also added a column for the number of goals scored after the 70th minute of the game.

To try to quantify the conditions in a single number I used the NOAA Heat Index* calculation to estimate how hot it felt to the players. This is a relatively crude instrument and doesn’t include direct solar irradiation but, meh, I don’t have time to do more. I also didn’t attempt to factor in the relative strengths of each side (Mexico beating Croatia was not as big a shock as Costa Rica beating Italy), that is probably worth doing so if you want to do that yourself, go ahead.

Anyway results,

1. There seems to be no correlation between goals scored and conditions. This also extends to goals scored in the last 20mins of games. I estimated the Pearson Correlation Coefficient to identify a correlation between goals scored and Heat Index. For the full match this came out at -0.051 and for the last twenty minutes -0.052. Hence there’s pretty well no correlation between high scoring games and conditions. See plot below,

goals_HINote in this plot I’ve isolated the matches between European teams and those from other continents. This leads me on to my second point,

2. The matches which were won by European teams were not that much warmer than the ones they lost or drew. Below are the histograms for the games won, lost and drawn by European teams when they face opposition from other continents.

Heat index of games played between European teams and those from other continents.

Heat index of games played between European teams and those from other continents.

So on first inspection it appears that the European teams did better in cooler games. I did a KS test to see if the games European teams won were drawn from the same distribution of conditions as the games they lost. This resulted in a 43% chance that they are drawn from the same distribution, i.e. it’s a 43% probability that the heat had no effect. This is a fairly ambiguous region of probability space so I wouldn’t shout from the rooftops that European teams are more affected by the heat than those from other continents. There of course a flaw here, France would probably beaten Honduras if all the players had been forced to wear parkas and the game had been played in an enormous sauna run by a particularly psychotic Finn. Hence there are datapoints in this calculation which would have likely turned out as win for the European team no matter what and there are much closer games which one might expect could be effected by the heat. Hence this rather simple analysis could be affected by small number stats (it would be a truly momentous upset if European teams were to lose all games in hot conditions and win all the colder games no matter what the opposition) so it probably isn’t worth drawing too many conclusions from it. Perhaps a more in-depth analysis involving pre-match betting odds/spreads would help to get rid of that effect.

 

In summary I’d say

It’s often stated that hot, humid conditions lead to high-scoring matches with European teams underperforming. The results from the group stages do not significantly support these hypotheses.

One final note  to give this a vague link to astronomy. Astronomical telescopes close in conditions of high humidity to stop condensation forming on the mirrors and electronics. The specific level at which telescopes close varies between observatories. 30 out of the 48 group matches were at a sufficiently high humidity (>60%) that the ESO Very Large Telescopes would not have been able to conduct observations. 25% of games failed the 75% humidity test used by some observatories on Mauna Kea. This is one of the reasons large astronomical telescopes are not situated next to football stadia in Brazil.

*Yes, I know, it’s in Fahrenheit, I don’t like it either.


A record-breaking brown dwarf: as cold as ice and just 6 lightyears away

About a year ago I wrote about how Kevin Luhman at Penn State had discovered a pair of brown dwarfs that were the just 2 parsecs (about 6 lightyears) from the Sun. Well he’s gone and done it again, discovering another brown dwarf at about 2pc, only this time it’s colder, much, much colder.

A decade and half ago, we astronomers (being rather odd) were getting very excited about some new odd objects we were finding by looking at the sky in infrared light. These brown dwarfs bridged the gap between very low mass stars (which can go down to about 8% of the mass of the Sun) and giant planets like Jupiter (with a mass of about 0.1% of the mass of the Sun). Brown dwarfs can’t fuse hydrogen in their cores so they don’t have a stable brightness like stars do and hence cool with time. This means that a very cold brown dwarf could be very low mass or just very old. Anyway, the things we were getting excited about 15 years ago had temperatures of about 1100C. At this point the cloud physics of these objects change dramatically, their upper atmospheres clear and their colours in near-infrared light changes significantly.

A decade or so went along and we started to get more excited as we crept to lower and lower temperatures, getting down to about 400-500C. Then we got a stroke of luck, Kevin Luhman (yup, same bloke) published the discovery of a really cold brown dwarf around a dead star called a white dwarf. This has a temperature of 25-80C, so between a pleasant summers day and a hot cup of tea. This object was joined by a few other slightly hotter objects which formed a newly defined class of cold brown dwarfs, the Y dwarfs. These big balls of gas about the size of Jupiter could have water clouds in their atmospheres.

So now we have a new coldest brown dwarf. It was found by looking at images from the WISE satellite which studies the universe in mid-infrared radiation. Nearby stars and brown dwarfs move slowly across the sky compared to background stars due to proper motion. This can be pretty slow, a very nearby star might move at one arcsecond per year, about the apparent angular speed of a tortoise walking at the distance of the Sun. So Luhman looked for objects that had moved a lot between different WISE images and found one which he published last year. This was a pair of cool brown dwarfs with temperatures of about 1100C. Now he’s published another that is moving even faster, about 8 arcseconds per year. Despite this, it is about the same distance as the previously published one, 2.2pc (a bit more than 6 lightyears). This distance was determined by follow-up Spitzer Space Telescope observations using a trick called trigonometric parallax.

So what is this thing? Well, we know it is bright in the mid-infrared, light which it is difficult to observe from Earth and which is way beyond what the human eye can see. And that’s where the observations of it stop, well not really, we can tell a bit about this object from what we don’t see, near-infrared light. Luhman’s new object was observed by the VISTA telescope in Chile a few years back. Well I say observed, it didn’t see it, neither did Luhman’s follow-up observations with Gemini. But from those observations one can set a limit of how bright this object is in the near-infrared and hence constrain its properties. Luhman used these along with his measurement of how bright the object was in the mid-infrared to find that the temperature was -48 to -13C, colder than ice on Earth, you’d even struggle to play at Lambeau Field in those temperatures. Not that this is a solid, icy planet, it’s about 3 to 10 times the mass of Jupiter and about the same size. It’s also a bit warmer than Jupiter which has an effective temperature at the top of its clouds of about -160C.

What more will we find out about it? Who knows. Last year’s spectacular Luhman discovery sent astronomers into a frenzy, studying the weather on the objects, even mapping its clouds. This one will be harder as the object is so cold and faint, but I’m sure observers will be furiously writing proposals to observe this immediately. Wait, why am I blogging? I should be proposal writing. And I’m sure this object will be one of the first things the mid-infrared JWST will look at when it launches.


Don’t call me Colin

Recently the International Astronomical Union decided that planets might start getting named after things. Previously they’d been given a lower-case letter after the name of their host star. Now they could get other names, something that inspired this memorable XKCD cartoon.

Well it turns out some of the planets aren’t terribly happy about the prospect too. In-fact Gliese 581d is pretty miserable about the idea of getting a dull or bizarre name, especially if you decide to name it after your cat, Colin. Gl 581d is a planet that’s a bit more massive than the Earth orbiting a faint, red star in the constellation of Libra. It might have a temperature that means it isn’t too hot or too cold to have liquid water (the so-called “Goldilocks zone“). This means it might have life. All it wants is to get a nice mythical name like the planets in the Solar System, preferably Norse but any pantheon would do. It really doesn’t want to be called after a celebrity or your mum or Permadeath, just a nice normal, mythical name. It’s been bombarded by comets for a billion years so don’t you think it deserves a break?
Be careful however, there are some mythical names are a bad choice, particularly Vulcan. This was a planet proposed around the Sun to explain the unusual orbit of Mercury. However it wasn’t there, the change in Mercury’s orbit was due to a subtle gravitation effect that wasn’t properly understood until Einstein came along with his theory of General Relativity.

Sometimes people have named stars for monetary or patriotic reasons like Herschel originally naming Uranus “George’s Star” after the British king at the time, so steer clear of that. Also a lot of asteroids have unusual names like Moomintroll, and it isn’t keen on that either. So please give a planet a break and name it something sensible.

Thanks to @ruthangus for doing the drawing, @emilulu and Russ for helping record this at AMNH, @astrodrian for lending me his guitar, @noisyastronomer for her camera and to .astronomy and the NERD Centre. The video was partly inspired by “Hey There Andy Murray” by Far-In Jim.

The audio file is also on Soundcloud.


A really, really nearby brown dwarf binary

OK I’m going to break my blogging silence and my aversion to blogging in my subject area to post about a really cool result that came out earlier this week.

Looking up at the night sky you see a hodge-podge collection of stars, perhaps a few thousand of the hundreds of billions of stars in the Galaxy. Some are extremely bright types of star that are really far away. Others like the Sun’s nearest neighbouring system Alpha Centauri are fairly run of the mill but appear bright because they are so close. But not all stars close to the Sun can be seen with the naked eye. Take Barnard’s Star, the second closest system to the Sun, it’s situated roughly twice as far away from us as Alpha Centauri but because it’s a red, faint type of star, it’s over 6,000 times fainter and 25 times too faint to see with the naked eye. This means that even though some stars are very close to us, they are so faint that we need to use a few tricks to pick them out from bright background stars.

One of the best tricks to use is to take a picture of the sky and look back a few years later and compare the positions of stars. Stars move around the Galaxy with different orbits and hence every star has a velocity with respect to the Sun. Due to their closeness, nearby stars appear to move  more compared to background stars (their proper motion). This is simply a perspective effect, they aren’t actually moving through space faster. Hence if you look for stars moving quickly across the sky, chances are a lot of them will be near the Solar System. This isn’t simply a matter of cartography, if you want to pick out a population of faint objects, your best bet is to look close-by.

And that’s exactly what Kevin Luhman did. By taking the positions of objects observed by the WISE satellite, he found one which stuck out. It moved across the sky pretty fast and was very bright in infrared light. Looking back at images taken by other surveys he also found it detected there. This often happens in astronomy, sometimes you find an object nobody had noticed was interesting before but which may have been first detected 50 or even 100 years ago. Anyway, the object Luhman found was moving across the sky pretty fast. Well actually it wasn’t, nearby stars tend to have their motions measured in arcseconds per year. One arcsecond per year is the same angular speed as seeing the average tortoise walking at the distance of the Sun from Earth. The newly discovered high proper motion object was moving at about 2.8 Solar Tortoises, which is pretty big for stars. Well I say star, but it isn’t, it’s a brown dwarf, well actually not “a” brown dwarf.

Stars are fuelled by nuclear reactions in their core. These work because of the huge temperatures in their cores caused by all the mass above pushing down. It’s like the atomic nuclei in the core are caught at the bottom of a really big rugby ruck*. Anyway, they get so hot that they can sometimes overcome their mutual repulsion and fuse together. However some objects, with masses below about 8% of the Sun can’t reach the appropriate minimum temperature to begin stable fusion and hence are “failed” stars or brown dwarfs. When Luhman took a spectrum of his object, he found it was a brown dwarf, well actually while taking the observation he found that it was actually two brown dwarfs in orbit around one and other. Finally, using the data from the WISE satellite and other surveys he was able to work out its distance from an effect known as trigonometric parallax. This showed the two brown dwarfs are about 6.5 lightyears away, slightly more distant than Barnard’s Star.

My reaction to this was probably like others in my field, “how did we miss this?” Well the answer is simple, the system lies close to the Milky Way. The density of stars on the sky increases sharply as you go close to the plane of the Milky Way, meaning searches of nearby stars are often flooded with spurious candidates. Additionally the gas and dust in the plane make background stars appear redder and faint in the optical but still bright in the infrared. This can mimic the colour of brown dwarfs, again contaminating searches. Brown dwarf searches therefor often avoid the region around the Milky Way to make sure they can have clean samples without wading through a load of junk. Hence the extremely nearby, bright brown dwarf lay undiscovered for decades after it had first been detected.

And that brings me to my last point, this is a really cool discovery yet it hasn’t got the attention it deserves. The third closest system to the Sun was just found, that should at least be on the BBC News front page.

*There are no known instances of a rugby ruck leading to nuclear fusion


Alpha Centauri, a quick biography

So you’ve probably heard the exciting news, that a small, earth-mass planet has been identified around one of the components of Alpha Centauri. It’s the nearest neighbouring system to our Sun. Despite that it isn’t the brightest star in the sky (that’s Sirius), also it’s a southern star so is not very familiar to those of us who live in the Northern hemisphere. In-fact I didn’t see it until I was 28 and had moved to Hawai`i. Here’s a picture I took of it rising above Kilauea.

Alpha Centauri over Kilauea

Alpha and Beta Centauri rising over Kilauea. Alpha Centauri is itself a double star with a planet around one of them and a wide third star in the system called Proxima Centauri.

Because it was so far south, Alpha Cent. wasn’t well studied by early European astronomers. In the 1830s Thomas Henderson, the first Astronomer Royal for Scotland measured its distance using trigonometric parallax. This was the first distance measurement to a star other than the Sun. However he hesitated in publishing the result and Bessell scooped him to the first published distance to a star (61 Cygni).

The system itself actually consists of three stars. The two brightest components appear as a single source to the naked eye. The two stars orbit each other at a distance about 17-18 times the Earth-Sun distance. There’s third star in the system, Proxima Centauri. It’s 100 times too faint to see with the naked eye and while the two brighter components are of similar mass to the Sun, Proxima is less than an eighth of that. That said for people like me who study low mass stars, it’s still not that low mass. It was discovered by another Scot, Robert Innes who worked as a wine merchant in Australia before taking up astronomy fulltime. Simply, he found a star with a similar motion across the sky to Alpha Centauri and given their close positions (yet it’s still 17,000 times the Earth-Sun distance from Alpha Centauri AB), deduced they were a pair. This is what I do a lot in my research, but I use large catalogues produced by data pipelines, he used many painstaking measurements by hand. Sometimes I feel like modern astronomy is cheating. One interesting side-note, this double star with a wide companion set-up seems to be more common than a single star with a wide low mass companion. A rather nice  recent paper by Peter Allen and others quantified this and indicated that this may say something about how these systems form.

A quick note about the planet. It appears to be too close to the star to sustain liquid water and hence life. This system has a fairly complicated Habitable Zone. The planet is orbiting the smaller of the two stars but it will also be heated by Alpha Centauri A. Duncan Forgan wrote a paper about this earlier this year saying the difference will be small but will induce oscillations of a few degrees. Also sometimes on the surface of the planet Alpha Centauri B will have set but the planet will still be lit by Alpha Centauri A. This will of course change as the two stars orbit each other. Duncan has a nice blog post about the paper where he also talks about sleeping rhythms on a hypothetical planet around Alpha Cent B. When Alpha Centauri A is on the other side of Alpha Centauri A from the planet I guess sunset will look a bit like that on Tatooine. Although with a different brightness ratio between the two stars.

So it’s Alpha Centauri has a planet. It isn’t able to support life, but maybe there’s another one in the system that can. What this discovery makes me think of is Civilisation. No, not the noted BBC TV series, but the classic Sid Meier strategy game. One of the victory conditions was to send a spacecraft to Alpha Centauri. I never got that far, on more difficult levels my civilisation would die in the Bronze Age and in the harder levels I’d get bored of nuking phalanxes in about 1900 and give up. However if I hadn’t given up perhaps I could have built a ship to head for what the Nature press release calls a “scorched barren rock”.