I have made a few mentions to the Kepler Mission in my previous posts. It really is one of the most amazing and fantastic missions that NASA has going on right now. And recently, they released the data on 155,000 stars. This wasn't even the entire sample taken by Kepler, the rest of the stars were released to the public through stuff like PlanetHunters.org. And Kepler is still running! Which means there will be more observations, and more planets observed. The first set of data was taken over 4 months. So every planet that transits a star in that 4 month period is observed. If we are looking for Earth-sized planets, that is only 1/3 of Earths entire year. So the longer Kepler looks, the more planets will become observable as they transit.
Now, from the 155,000 stars released there included 1,235 candidate planets. Those numbers split as 68 Earth-size, 288 super-Earth-size (about twice the size of Earth), 293 are Neptune-size (about four times the size of Earth), and 165 candidates are the size of Jupiter (11 times the size of Earth). Those numbers themselves, from a relatively tiny patch in the sky, triple the known number of planets.
More after the page break.
So this is where the fun begins. Using these numbers and making estimates based on them and other known planets, the astronomers on the Kepler team have determined that 1 our of 2 stars has planets. Now that might not seem right from comparing 1,235 candidate planets to 155,000 stars. But the important things here are that this data is only 1/3rd of an Earth-like year, so these numbers need to multiplied by at least 3 to account for that. If the planet is further out, then the orbital period is longer. So, even by multiplying by 4 as a benefit of the doubt to Earth-like planets, we end up with 4,940 planets. Jupiter takes almost 12 years to orbit our Sun.
Now that aside, not all planets transit in front of their host/parent star. This depends on where there orbital plain is aligned. We are lucky to see so many in line such that the transits are visible from our solar system. But that isn't really luck, it lends to the idea that orbital plains are not uniform, but unique to each star system. In fact, one of the other forms of detecting planets is watching for the slight jiggle of a star as a planet orbits. So taking into account all these possibilities for planets, these astronomers have arrived at roughly every other star having planets.
Even more amazing then that, roughly 1 star out of 200 have planets in the habitable zone. There are at least 100 billion stars in the Milky Way galaxy (our home). So at least 50 billion planets, and at least 500 million in the habitable zone. The not-to-hot, not-to-cold sweet spot where life could exist.
500 MILLION possibilities for life to arise in our galaxy alone. This is a number that I never thought I would see in my lifetime, and I consider myself young, a month away from 25. It is an important number that satisfies the first three values of the Drake Equation. The Drake Equation if you do not know is used to estimate the number of detectable extraterrestrial civilizations in the Milky Way, and it looks something like this:
- N = the number of civilizations in our galaxy with which communication might be possible;
- R* = the average rate of star formation per year in our galaxy
- fp = the fraction of those stars that have planets
- ne = the average number of planets that can potentially support life per star that has planets
- fℓ = the fraction of the above that actually go on to develop life at some point
- fi = the fraction of the above that actually go on to develop intelligent life
- fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
- L = the length of time for which such civilizations release detectable signals into space.
But perhaps we did win the cosmic lottery for our Galaxy, maybe even the Universe. Now that we have real numbers to look at, things look a bit clearer, but more questions are raised. There are several practical, religious, cultural, and societal implications that come from this knowledge. Generally this arises from the Fermi Paradox. The Fermi Paradox simply asks, 'Where are they?' Where are the extraterrestrial intelligences despite the high estimates for their existence. And this is where I will pick up next time, I will look at the Fermi Paradox in relation to the Kepler Mission findings.
A couple of sources and interesting reads: