Exciting exoplanet news today: rogue planets and an Earth-hunting nanosatellite the size of a loaf of bread

Thursday, May 19, 2011

Lots of exciting exoplanet news today. Let's start with the big story: it seems that space is absolutely filled with rogue planets, planets that don't orbit a star or have an extremely weak connection to one. In fact, the predicted number of these planets is actually twice the number of planets that orbit stars, which means hundreds of billions in the Milky Way alone - in other words, very very good news.

The estimate for the number of rogue planets was done through gravitational lensing, where a heavy body passes in front of a star and bends its light in a certain way, and the particularly short period of time means that the planets (ten of them were detected) have to be at least 10 AU away from the parent star...and the most important part of this is that Jupiter-mass planets aren't supposed to be common (or exist entirely?) at that distance. So it seems that rogue planets are the most likely explanation. On top of that, along with everywhere else in space the smaller the planet the more of them there should be, so planets our size will be even more common than the Jupiter-sized ones the team picked up.

I'm not all that surprised by the news however, as our knowledge of rogue planets thus far has been exactly zero, but their existence is certainly not even close to unlikely: all you need is a planet that has been knocked out of a star's orbit or developed on its own, certainly not the rarest event in the universe. Having more rogue planets than actual star-orbiting planets also means that in theory there should be a number of them in between us and Alpha Centauri, and heading in who knows what direction. Add to that the impending discovery of brown dwarf stars by WISE (and what the f*^& is taking them so long to announce anything?!) and our solar neighborhood is due to become a lot more interesting in the near future.

Finally, life on a rogue planet is certainly possible, and many papers have been written on this. A rogue planet would have an easy time retaining an atmosphere (no solar wind to blow it away) and if the planet remains warm for long enough then the planet's surface and oceanic conditions would be pretty mild. For a moon of a rogue planet of Jupiter's mass, there is also tidal heating to keep it warm.

And now the second article! See here. A nanosatellite the size of a loaf of bread is to be launched next year. It's called ExoPlanetSat and is being developed by MIT and Draper Laboratory, and as the name suggests it is used to detect exoplanets. There are two things that make this satellite interesting. One is that this tiny satellite is capable of locking onto a single star (as opposed to Kepler with 150,000 at a time) to detect exoplanets, with a precision capable of finding planets of our size. Being able to only focus on one star at a time is unavoidable with a satellite this small and cheap (more on that in a bit), but the advantage here is that ExoPlanetSat can observe stars that we consider to be potentially interesting.

Why is that important? Kepler shows us why. Because Kepler is capable of imaging 150,000 stars at a time, scientists chose a part of the galaxy that has a particularly large amount of them in its point of view, in preference to Alpha Centauri's solar neighborhood for example, because though Alpha Centauri is of particular interest to us it is not in an area (from our point of view) particularly populated with stars and would not help to give us the statistical data we need to make predictions about extrasolar planets.

ExoPlanetSat, on the other hand, can focus on any star its team wants, and the team is particularly interested in Alpha Centauri.

Finally, the cost. This is one of the most exciting parts of the project for me, as I have often written about the wish to see a single cheap mission that can be repeated over and over again at a lower cost each time. ExoPlanetSat is exactly this: the first one is to cost $5 million to build, but after that the cost will drop to $600,000.


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