Archive for January, 2013

Look up into the night sky and you’ll see thousands, if not millions (and with a good telescope, billions) of stars. Now as it turns out, you may also be seeing millions of planets!

This is the conclusion of a study by the California Institute of Technology (CALTECH) adding even more evidence to the idea that planetary systems are actually the galactic norm, rather than a lucky fluke. The team at CALTECH made there calculations after observing the planets orbiting the star Kepler-32, a star system, they believe, is actually representative of most of the stars in our galaxy, the milky way.

“There’s at least 100 billion planets in the galaxy—just our galaxy,” says John Johnson, assistant professor of planetary astronomy at CALTECH and co-author of the study

“It’s a staggering number, if you think about it,” adds Jonathan Swift, a post-doctorate at CALTECH and lead author of the paper. “Basically there’s one of these planets per star.”

The star system serving as the astronomers master copy, the Kepler-32 system, has a series of 5 planets (2 have so far been confirmed by other institutes and independent astronomers) orbiting around a M type star (a red dwarf) a star about half the brightness of our star, the sun. This type of star accounts for nearly three quarters of stars in the milky way. The five planets, which are similar in size to Earth and orbit close to their star, are also typical of the class of planets that the Kepler telescope has so far discovered orbiting other M type dwarfs. This has led CALTECH to their conclusion that most of the stars in our galaxy have at least one orbiting planet, if not many more.

So while this system in particular may turn out to be very common, one thing makes it very special for astronomers and physicists the world over. The orbits of the planets lie in a plane that’s positioned such that Kepler views the system side-on. Due to this rare orientation, each planet blocks Kepler -32′s starlight as it passes between the star and the Kepler telescope. This gives scientists the rare opportunity to study the planets’ characteristics, such as their sizes and orbital periods. This orientation therefore provides an opportunity to study the system in great detail—and because the planets represent the vast majority of planets that are thought to populate the galaxy, the team says, the system also can help astronomers better understand planet formation in general.

One of the fundamental questions regarding the origin of planets is how many of them there are. Like the Caltech group, other teams of astronomers have estimated that there is roughly one planet per star, but this is the first time researchers have made such an estimate by studying M-dwarf systems, the most numerous population of star systems known.

To do that calculation, the Caltech team determined the probability that an M-dwarf system would provide Kepler-32′s edge-on orientation. Combining that probability with the number of planetary systems Kepler is able to detect due to its resolution, the astronomers calculated that there is, on average, one planet for every one of the approximately 100 billion stars in the galaxy. But their analysis only considers planets that are in close orbits around M dwarfs—not the outer planets of an M-dwarf system that Kepler struggles to ‘see’ due to irregular orbits of weak starlight, or those orbiting other kinds of stars, like our own G type star. As a result, they say, their estimate is conservative. In fact, says Swift, a more accurate estimate that includes data from other analyses could lead to an average of two planets per star.

This huge prediction in planet numbers has come in the wake of planets being discovered left, right and centre by the Kepler space telescope and other observatory’s  and their numbers are only likely to increase. And who knows, maybe they’ll find a planet close enough for us to visit someday?…

Alex Davis



When we’re little (and in some strange cases, into adult hood), the story of Father Christmas, the fat old man adorned in red and white robes, pervades our lives, (hopefully) making us think about our actions due to the threat of being branded a “naughty child” and getting coal as a present instead of that new PlayStation game you really wanted. However, there comes a time in every child’s life where they learn the truth of Christmas. The truth that an old man doesn’t break into you’re house, leaving gifts, but that instead your parents quietly hide presents in the loft until you’ve gone to sleep on Christmas eve.

And for those of you that still believe, sorry, but the truth hurts.

But, as a bit of an annoying child, one thing always puzzled me, if this legendary man DID exist, how would he get around the world, and all its good children, in only one night? would it even be possible?

Well lets start with the children. There are roughly 2 billion under 15’s on earth at any one time (lets assume this is the point you stop believing in farther Christmas and start buying people gifts instead, you cheapskate). However, since St Nick does’t visit children of Muslim, Hindu, Jewish or Buddhist (except maybe in Japan) religions, this reduces the workload for Christmas night to about 33% of the total, around 660 million children, and with a global average fertillity rate of around 2.5 children per woman (and therefore household) this amounts to about 250 million households, assuming there is at least one good child in each.

Now, farther Christmas has circa 31 hours (if we include things like the rotation of the earth and differing time zones) to make his round trip of the world and its homes, this works out as 2240 visits per second. That is to say, St Nick has around 1/2500 th’s of a second to park up on your roof, break into your house, fill your stockings, place your presents, eat any food left for him, get out again and reach the next house.

Assuming these 250 million homes are evenly distributed around the world (which, of course, they wouldn’t be), we’re now talking 0.23 miles per household, a minimum trip length of 131.1 million miles, without diversions around storms, aeroplanes or mountains.

This means our dear old Father Christmas has to be travelling at a speed of around 1175 miles per second (4,226,000 miles per hour) this is about 5500 times the speed of sound. In comparison, the fastest ever man made object is the Helios space probes, which orbit the sun with an average speed of 44 miles per second, your run of the mill reindeer can run at about 0.00416 miles  per second (15 miles per hour).

The payload of the sleigh adds another interesting element. Assuming that each child gets nothing more than a medium sized LEGO set (two kilograms), the sleigh is carrying over 500 thousand tons, not counting Father Christmas himself. While on land, a conventional reindeer can pull around 150 kilogrmas. Even granted that flying reindeer can pull 100 times this, St Nick would need more than 8 or 9, he would need 33,000 of them. This increases the payload even further, adding another 5000 tonnes to the sleigh. This makes it similar in weight to the Seawise Giant, the longest ship ever built, and by many standards, the largest man made, self-propelling object ever.

500,000 tonnes moving at 1175 miles per second is going to produce a lot of air resistance. It would be equivalent to a spacecraft re-entering the earth’s atmosphere 168 times faster than its supposed to. As a result, the reindeer would almost instantly evaporate into a superheated cloud of atoms and molecules.

Not that it matters much, since St Nick, as a result of accelerating from a dead stop to 1175 miles per second in 0.0004 seconds, would be subjected to acceleration forces of 22 million g’s. A 115 kilogram Father Christmas (which seems ludicrously slim) would be pinned to the back of the sleigh by 217 million newtons of force, instantly crushing his bones and organs and reducing him to a quivering blob of pink goo.

Therefore, if Father Christmas did exist, he doesnt now.

Hope you had a good Christmas, and happy new year!

Alex Davis


New Eyes on the Sun: A Guide to Satellite Images and Amateur Observation by John Wilkinson