It’s been a while since I’ve posted here – now that the New Year is well and truly in, I’ll bring you up to speed over the next few weeks with some of the papers I’ve published recently. For now, here’s what I wrote about dubious claims of finding extraterrestrial life at Research the Headlines:
Originally posted on :
Is Earth the only object in the Universe that can boast biological organisms? This question burns in the minds of astrobiologists, scientists from many disciplines (astronomy, physics, chemistry, geology, biology and many more) who investigate how life appeared on Earth, and whether other worlds possess the necessary conditions for life.
We all know that life on Earth depends on the Sun, and not just to keep the cold out. Plants convert sunlight into energy through photosynthesis, giving us oxygen to breathe, and in one way or another, the whole food chain relies on our parent star for support.
But what if our solar system had two stars? We know that there are several exoplanet systems out there that have the luxury of multiple host stars. In the case of the Kepler 47 system, there is a planet in the habitable zone (confirmed by several teams of astrobiologists, including myself). Kepler-47c orbits a star quite like our Sun and a cool red dwarf star (see graphic below), and so we refer to it as a circumbinary planet.
But what would it be like to live on a planet like Kepler-47c, and gaze at a double sunset like Luke Skywalker? Would life be all that different? In a paper recently accepted for publication by the International Journal of Astrobiology, we explored this question.
Strictly speaking, it would probably be quite hard to stand on Kepler-47c, as it’s probably a gas giant comparable to Neptune, so we imagined that Kepler-47c was in fact an Earthlike planet – after all, chances are that there is a planetary system out there like this. We considered how the radiation from the two stars hit the planet’s surface, mapping patterns of light and darkness.
Because the two stars in the Kepler-47c system are so different in mass, they produce radiation at very different wavelengths – the sunlike star emitting a spectrum that terrestrial plants would happily photosynthesise, and the other star emitting much more red and infrared radiation, which some forms of anaerobic bacteria would photosynthesise (see more here). So depending on the time of year and time of day, different organisms would take the lead in converting starlight to energy.
But it’s not just the light patterns that are interesting. The darkness patterns show that above the polar circles (on earth, these are the Arctic and Antarctic circles), summer and winter become rather peculiar.
Above the arctic circle on earth, winter begins when the sun sets, and stays set until winter ends a few months later. On our Tattoine planet, there are two stars in the sky, so the arctic winter begins when both stars drop below the horizon. But the planet orbits the centre of mass of the system, as do the stars. This means that depending on the arrangement of all three bodies, some years have a winter that is a few days too short, and others have winters that are a bit too long. If you’re an animal counting on the end of winter to end your hibernation cycle, you need to know whether this year’s winter will be long or short!
Judging by life on earth, it seems likely that animals will be able to develop instinctive and biochemical rhythms to cope with these fluctuations, just as we have circadian rhythms to cope with day and night time. In fact, some organisms on Earth already obey the influence of a second star – except it’s not really a second star, it’s just the Moon!
In short, life on circumbinary planets will be a slave to the rhythm, just like life on Earth. But there will be many more rhythms to choose from!
I gave a quick 8 minute talk in the “IMF: Facts and Myths” session on the properties of brown dwarfs – those awkward objects that are too small to be stars, but too big to be planets. These in-betweeners turn out to be a very sensitive probe of planet formation theories, and observing the mass distribution of brown dwarfs should tell us whether they are more starlike than planetlike (more on that in a future post).
Alongside my usual conference activities, I took part in the first ever NAM hack day. Hack days are an opportunity for programmers and like-minded people to spend a day creating something useful or fun from scratch. “Hack” is the operative word here – throwing together something in a few hours is never that polished :)
My effort was inspired by Pythagoras’ musica universalis, or “music of the spheres”. Pythagoras, and others like him, were convinced that there was a deep relationship between mathematical concepts and music. Music theory depends heavily on mathematics, but Pythagoras believed that mathematics itself was inherently musical, and that the Universe moved to a deeply beautiful set of rhythms and harmonies. For example, he believed the motions of the planets produced a music that, if humans could hear it, they would not only consider it beautiful, but discover a deeper understanding of how the Universe worked.
So, I thought about the music in planetary systems. We have the benefit of knowing many more planets than Pythagoras did, orbiting stars other than our Sun. Even for a musical dunce like myself, it’s easy to create musical notes from the properties of planets. And that’s exactly what I did for my hack: I took exoplanet data from the Open Exoplanet Catalogue, and made repeating notes for each planet. The period of the planet’s orbit dictates how frequently a note is played. If a planet orbits its star once a year, then its note will play once per second. The pitch of the note is determined by the planet’s size – small planets play a high pitched tone, and large planets play a low pitched tone.
So here’s what the Solar System sounds like as a song (headphones recommended for the full bass experience):
The inner planets orbit the Sun quickly, and make a series of high pitched ringing sounds, with the giant planets beating out a slow, ponderous bass line.
The code I wrote to make this music is open-source on Github – you can find it here. It’s written in Python, and has a reasonable user interface (remember it’s a work in progress!). Happy music making!