Keeping on the exoplanet series, after the general introduction and the presentation of the oldest one (so far) discovered, today I am going to address another interesting characteristic: distance.
Distance matters, no discussion about it. I have already mentioned the importance of the HD – Habitable Zone – which is obviously in relation to the planet’s distance from its star. Earth is a good example of one not too close, not too far, therefore enjoying conditions favourable to life. In the case of the Solar System, we have quite a variety in terms of distance from the Sun.
(CREDIT:NASA)
However, and surprisingly enough these are not the most extreme distances we can expect in a planetary system – even assuming, for the sake of simplicity, there’s just one star (in the case of a binary system, things can dramatically change). Just a couple of months ago, researchers at the University of Montréal made the news identifying a stunning planet, many times the mass of Jupiter, at an incredible distance from its star: 2000 AU. To give you an idea, roughly 40-50 times Pluto’s distance from the Sun (yes, distance too varies). Simply amazing, considering that planets so far away challenge all current theories about planet formation. GU Psc b – that’s the name of this little wonder – is so distant from its parent star that the Gemini telescope, a wonder in its own right, was even able to photograph it without any adaptive optics (and you will need to read the whole story here to really understand how amazing it is. Otherwise, just trust me on this one).
And here it is, a tiny, independent point of infrared light, separate from its star. This is fundamental for a series of reasons – to test planet formation and mechanics model, for instance, and even its physical properties, such as mass, or temperature, usually difficult or impossible to properly evaluate because of the parent star.
And what about the opposite, then? How close a planet can be to a star to avoid being eaten (and not metaphorically: this actually happens, and we have the proof. But this is for another post.)? At this stage, it’s a question almost impossible to answer: the closer the planet, the more difficult the detection. We can only rely on theories and models – the same GU Psc b has proved abundantly flawed, when not plainly wrong.
There is instead another question we can answer: which one is the closest exoplanet to our system? We do have a good candidate.
(CREDIT: NASA, ESA)
Its name is Epsilon Eridani b, and it orbits a pretty, orange Sun-like star just 10.5 light years away from Earth. Next door, in astronomical terms, and in the range of our telescopes – so images of this baby may well pop up in the near future.