January 30, 2012
In the days before Christmas celebration, announced the discovery of two new planets "extrasolar", ie orbiting other stars beyond our solar system.
But this is not new. After all, more than a decade are finding extrasolar planets. What is significant is that it is the planet most like our Earth discovered to date.
These new worlds are part of a system of at least five planets circling around the star Kepler 20, located about 1000 light years from our Sun in the direction of the constellation Lyra.
The system was discovered by the Kepler orbiting telescope from NASA. Of the five planets, called Kepler Kepler 20e and 20f have masses similar to Earth: a 13 percent and 3 percent, respectively.
The finding is important. François Fressin, the Harvard-Smithsonian Center for Astrophysics (USA), principal author of the study, said: "The discovery shows for the first time the existence of planets the size of the Earth around other stars and are able to detect ". The latter is not false modesty. Is that to discover the tiny signals that reveal the presence of these bodies, astronomers technology should require all that it can give.
There are several ways to detect extrasolar planets. One of them is to observe the transit of the body to its star, ie how the sun passes in front, causing a tiny eclipse.
This requires that the planet's orbit takes it passed in front of its star as seen from Earth. In many cases, the planets may be overlooked by the absence of this alignment, but in this case, there are other techniques available.
The variations in the brightness of the star caused by these eclipses are really sensitive. To understand this, imagine that someone in Buenos Aires tries to measure the dimming caused by a mosquito that crosses in front of a luminaire in a square ... Mar del Plata! (Obviously, the curvature of the Earth and the presence of buildings and trees would be impracticable this observation, but these are not obstacles in astronomical observations.)
This is what the Kepler observatory aims to measure and it has a huge capacity for observation. His list of objects to observe star reaches 150 000 and each one sends data about its brightness every 30 minutes. Also, being out of the atmosphere, the stars are not affected by the "flash" caused by the air. In sum, the satellite provides a large amount of high-precision data: a "paradise" for science.
In fact, the data are so numerous that we have organized a website for anyone to help them discover these small variations. In www.planethunters.org, after a brief tutorial (in English), you can join thousands of volunteers planet finders.
The search for extrasolar planets led much of the twentieth century, but only from the 90 instruments had astronomers sufficiently accurate. In 1995, Swiss astronomers Michel Mayor and Didier Queloz announced the world that the first exoplanet confirmed revolved around 51 Pegasi, a star about 50 light years from Earth. Then, the advancement of technology facilitated the detection and in recent years the pace of discovery has accelerated significantly.
Currently there are over a hundred search programs observatories around the world and from space telescopes. Until late last year found more than 700 exoplanets, and a long list of candidates still in the process of verification.
The motivation is understandable, as there are several questions await an answer: what fraction of stars have solar systems and where are they? How common are planets like our Earth? Is there life on them?
Most discovered so far are completely different from ours. On the one hand, are too large, more like Jupiter or the other giant planets of the Solar System. Worlds are no solid surfaces and liquefied gas compounds by the tremendous pressure of the interior. On the other hand, lie too far or too close to their "habitable zones" (see separately), which makes the world too hot or cold to sustain life forms as we know it.
According to the Planetary Habitability Laboratory at the University of Puerto Rico, of the 716 exoplanets discovered, 84 are in their habitable zones for their respective stars, of which only two can be considered "land".
The two candidates are called Gliese 581d and HD85512b and were discovered in 2011 from the La Silla Observatory in Chile. Both are much larger than the Earth (4 and 7 times its mass, respectively) and, therefore, their gravities are higher than ours. The observations suggest that the average temperature in these worlds would be about +65 ° C and -65 ° C, respectively. In these extreme temperatures and high gravities, researchers assume that the best could support microbial life.
The planets Kepler and 20f 20e, however, are more like Earth, but they are too close to its central sun and, therefore, far from the occupied zone.
Can you in any case contain strange life forms, capable of withstanding very different from our planet? A reasonable question: after all, there are fish that live at great depths, almost independently of the sun and the atmospheric air. There may very exotic life forms, but no one knows yet.
In general, scientists proceed with caution, based on what they know to explore the unknown. The discovery of these "cousins" of the Earth is a first step. We will have to look any further. Other scientists also seek evidence for intelligent life years mixed in radio signals (from natural sources) that reach us from outer space.
In summary, 2012 starts with no known planets that meet both conditions simultaneously: having a size and structure similar to Earth orbit within their habitable zone.
The search will continue this year. Having a map showing the location of potential terrestrial planets, exobiologists (scientists searching for life beyond Earth) may direct some of their efforts towards these worlds. While it is important to remember: the discovery of planets with characteristics very similar to ours, even with air, water and temperature, does not necessarily imply that these worlds are inhabited.
But there will, no doubt, a huge motivation to look for evidence that potential life forms may be left in their soil or atmosphere. This is also reasonable, judging by the tracks the activity of our civilization is leaving on his own planet.
Publicado por Nadir Sosa en 2:28:00 AM