Kepler: An Evolution and a Shift

The announcement by Kepler a little more than two weeks ago was undoubtedly huge. The discovery and confirmation of a really interesting planetary system consisting of six confirmed planets was released. This announcement was coupled with the discovery of over 1200 other planet candidates. In the time since the announcement, I have been struggling to fully comprehend the immense size of the numbers. Now, I have started to just realize that the numbers may not be the most interesting idea to keep in mind. We also have to step back from the recent news and see that the Kepler announcement may be the representation of the start of a new era and a giant shift in looking for life outside of the Earth.

At one level this Kepler announcement represents the evolution of our exoplanet detecting skills, and the number of planets discovered does tell a huge story. The rapid pace we have achieved in detecting exoplanets is no small feat. About 15 years ago, the first extrasolar planets, about the size of Jupiter, were just beginning to be detected. Before these discoveries, many scientists doubted ever being able to detect an extrasolar planet. Now, including great contributions being made by the Kepler spacecraft, we may have about 1500 planets detected and confirmed soon, a remarkable jump especially since many of these planets are much smaller than Jupiter. The Kepler announcement is also encouraging in that its discoveries are only being made in a single patch of sky. This area covers only about 1/400 of the area of the entire sky. Admittedly, other patches of the sky may not be as rich of stars containing planets as Kepler’s field of view, but it is extremely likely a huge amount of planets are still waiting to be discovered.

What really excites me though is that this announcement marks a shift in our search for extraterrestrial life. Although Kepler’s mission is to look for planets and not life, I feel that  the scientific community and the rest of society is particularly interested in exoplanets because they may offer clues as to whether Earth life is an anomaly or the norm. This is why in every news piece I have read about the announcement so far, the fact about the list of potential Kepler candidates containing 54 planets about the size of the Earth located in the habitable zone is particularly emphasized. Any of these planets could contain life that is similar to ours and therefore their discovery captures our attention. The Kepler mission in particular represents a new era, in which our search for life outside our solar system is passing from a passive approach to a more active approach. In the era before Kepler, finding life outside of the solar system meant relying on projects such as SETI (Search for ExtraTerrestrial Intelligence). SETI attempts to detect signals that intelligent life may be broadcasting. This relies on the lifeforms having evolved and progressed as a society far enough so that they are able to regularly broadcast signals in the specific frequency ranges that Kepler is able to detect. Kepler, on the other hand, is taking a more active role. Kepler actually searches for planets that may be hospitable to life. Afterwards these planets can be examined in detail for traces of life, which do not necessarily have to be left behind by intelligent life.

The change, I think, is extremely important. Our search for life has become much more efficient and likely more fruitful. It as if we no longer have to face an expansive ocean hoping intensely that something in it will make contact with us. We can now wade in, start turning over rocks, and examine what we find. This is why I have been very obsessed and excited about the announcement. I believe when looking back after a number of years, the Kepler project and announcements like this will mark the point in history when we no longer sat back, but stood up and got our feet wet.

A Planet with a Tail

An artist's interpretation of how extrasolar planet HD 209458b may look.
Image: NASA, ESA, and G. Bacon (STScL)

A giant gas extrasolar planet, HD 209458b, has recently been confirmed to possess a tail, resembling something like that of a comet. The planet is similar to Jupiter, but unlike Jupiter it orbits very close to its star, completing an orbit every 3.5 days¹.

The planet, about 153 light-years from Earth, has been heavily studied since its initial discovery because it was one of the first discoveries of an extrasolar planet transiting its star. This is a special case where the orbit of the planet allows it to eclipse its star, as seen from the Earth. The rare position essentially allows astronomers to study the atmosphere of the planet, finding out what chemicals make it up (the process is detailed for a similar case here). Astronomers studying HD 209458b discovered that the planet’s atmosphere contains heavy elements including carbon and silicon. Since the atmosphere is exposed to the scorching heat of the star due to their close proximity, the heavy elements can escape.

Eventually, these materials come together to form a large flow of gas coming out from the planet. On the Earth, astronomers have detected the gas to be coming towards us at 22,000 miles per hour. When the stellar wind from the star picks up the gas, the tail, resembling one of a comet’s, is formed. Still, despite the large outflow of gas, the planet is not likely to completely “evaporate” anytime soon. It is estimated that it will take a trillion years for that to happen.

The recent finding is important in that it further helps us realize how our star is not unique in harboring planets, as the numerous other discoveries of extrasolar planets have proved. However, perhaps more importantly, it shows the intense variety of what can be found in the universe.

Footnotes

1: Extrasolar planets are planets that are found outside of our solar system, orbiting other planets. Recently, there has been an explosion in the discovery of extrasolar planets, and the number of total extrasolar planets discovered so far is currently a little over 450.