ETs and exoplanets

There’s been a few news items related to extrasolar planets and extraterrestrial life out today.

Firstly, Astronomy Now has augmented its April focus on the anniversary of SETI with three new articles on the Drake Equation, which Frank Drake used to estimate the number of radio noisy civilisations there should be out there. The full series of articles, including the new three, are packaged here.

Drake himself is still alive and celebrated the half centenary of his search by recreating his observations of two stars with the Green Bank radio telescope, this time in front of the cameras. Full story at Discovery.

Still, if life isn’t that easy to see, at least planets can be picked up and their orbital characteristics determined simply, right? Well, not as simply as you may think. Take the radial velocity method that accounts for about three quarters of all discoveries. Astronomers measure the radial velocity of a star, hoping to pick up the signal of the star orbiting a common centre of mass with a planet (inducing a ‘wobble’ or radial velocity). Astronomers measure this for a given star time and time again. But the trouble is there are times when it cannot be measured – daytime, seasons when the star is unavailable, times when the Moon is in the way or so totally out of the way that others want to make use of the telescope. Being several observations short of a full dataset is never a good place to be. It can lead to so called ‘aliases’ – apparent orbital frequencies that just aren’t – being mistaken for actual frequencies. Now a paper is out that aims to define a method to identify these frequencies and eliminate them from an otherwise carefully honed dataset.

And it is important in such a thing that a universal method is found that can be applied to any observation, because some exoplanets just don’t conform to our idea of a sensible orbit. Exoplanets with years lasting less than a day for example. Or the Upsilon Andromeda exoplanets mentioned in this Discovery article that chose to have one of them on an orbital path more often associated with a comet. It seems that a second star has been interfering with the planets and given them a gravitational boost every now and again, altering the outer one’s orbit so the inclination and eccentricity are enhanced, while the middle of the three known planets has a lower inclination and little eccentricity and the inner planet seems to have escaped the rogue star’s attentions.

These bizarre conditions could lead to bizarre worlds, as will be discussed in the BBC Focus Magazine’s next edition. Diamond planets, water worlds, they’re all there.

And finally, want the latest news on exoplanets straight from to your phone? There’s an app for that.


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