In 2009, a mission was launched that according to NASA could discover thousands of planets around other stars and revolutionise our place in the universe. That spacecraft was Kepler, and for nearly 4 years it has stared constantly at the same tiny patch of the Milky Way looking for the characteristic dips of light as exoplanets wander across their parent stars. But now, with a mechanical error threatening the entire mission, questions are being asked if the $600million mission really was such a revelation.
9857. That’s the number of stars Kepler has seen glitter with the tell-tale sign of nearly 16000 exoplanets. It is remarkable then that 99.2% of these remain unconfirmed, with only 120 being recognised by the astronomical community as planets. It’s not just because NASA is swamped with data: to be confirmed every planet discovery must be analysed by a different method. This usually involves ‘weighing’ the planet using the motion of the star to determine how strong the gravitational attraction of the planet is. More intriguingly, follow-up observations can even reveal the atmospheres of such exoplanets, paving the way for the search for alien life.
Here comes the downside; finding a planet’s mass or studying its atmosphere is only possible when it circles a bright star. Kepler, on the other hand, has been searching for small planets around dim and distant stars. It has, effectively, spent 4 years and hundreds of millions of dollars looking for planets that will forever remain unconfirmed and uncharacterised. This is especially pertinent when compared with the much cheaper ground-based surveys that have found more confirmed planets around bright stars.
While it is certainly a disappointment that these planets may never be seen again, can’t NASA just assume their haul of ‘planetary candidates’ are all real? According to a recent study, the answer is no. Astronomers at the Observatoire de Haute Provence went hunting for Kepler’s planets. They found that more than a third of these so-called planets were anomalies produced by a second star. Without knowing how many planets are phantoms, even the recent predictions of a 100 billion planets in the galaxy may be stabs in the dark.
But, despite a few negatives and some overly optimistic goals of the NASA team, Kepler has been successful. The majority of its planets will turn out to be real, including a handful of Earth-like worlds that could support life (even if we never get a closer look). And if the ‘bias’ in Kepler’s results can be figured out, it could provide us with fascinating statistics showing just how common solar systems like our own might be.
That makes it an even greater shame that the spacecraft is wounded. To keep Kepler staring at the same patch of sky, it makes use of 3 ‘reaction wheels’. But after the failure of one of these stabilisers last July, the discovery of wear and tear on a second wheel in January 2013 could prove fatal. For those working on Kepler, the next few weeks will be anxious as they try to fix the problem from the ground, and, despite its shortcoming, I hope they manage it.