Since the early 1990s, astronomers have found more than 300 planets orbiting sun-like stars, nearly all of which are giants like Jupiter. Modern space telescopes like new ones launched for NASA's Kepler mission will help find tiny planets but more like the Earth outside the solar system (also known as exoplanets) become easier.
But observed from tens of light years away, earth-like exoplanets from a telescope's perspective are only slightly smaller than a faint blue point - the term is used by astronomer Carl Sagan. depicting the Earth's image in a 1990 photograph by the Voyager spacecraft when it is near the edge of the solar system.
Using Deep Impact spacecraft tools - a group of astronomers and cosmologists have created a new technique to know if a planet contains liquid water, from which Can you know if the planet can support life?
Nicolas Cowan - a student pursuing a doctorate at the University of Washington in astronomy and the main author of an article explaining the new technique, was published in the Astrophysical Journal - said: 'Water liquid on the surface of a planet is the gold standard people seek '.
As part of NASA's planetary extermination and classification program, the scientists conducted two separate 24-hour observations of light intensity from seven bands of light observed from the steps Short light near ultraviolet light to long light wavelengths near infrared. The earth is gray in most wavelengths of light because it is covered by clouds , but it is green in short wavelengths of light under the influence of the same atmospheric phenomenon that makes the sky blue under her. our eyes.
The researchers studied the small difference in average colors caused by surface characteristics such as the appearance of clouds and oceans inside and out of sight. They discovered two dominant colors - a reflective color at longer wavelengths, and the other at short wavelengths - red and green. Red is the color of the soil and green is the color of the oceans.
Analysis has been conducted 'as if they were aliens who are looking at the earth with the tools we can own in the next 10 years' but have yet to provide information about the composition of the earth. , follow Cowan. 'We aggregate the brightness into a pixel in the telescope's camera, when the earth is really a faint blue point'. Because the color of the earth changes during the 24-hour observation period, scientists mapped the earth in the main red and green colors, then compared what they read from Map with real locations of continents and oceans on the planet.
Cowan said: 'You can say there are oceans containing liquid water on the planet. It is assumed that somewhere has liquid water on the planet, it must be in the habitable zone of the system. But being in a living area cannot guarantee liquid water. '
Observations were made on March 18 and June 4, 2008, by the mission ship when it was located between 17 million and 33 million from Earth and was right above the equator. Observations carried out on the polar regions are all white images. In the next few years telescopes capable of conducting similar observations to search for Earth-sized planets will be launched into the sky, but current techniques can pave the way for construction. build the state-of-the-art equipment. While extraterrestrial planets are still far away, the technique is still applicable.
Cowan said: 'You will still have all the information about misery, and more importantly, there must be information to see how the brightness of a small spot changes.'
Co-authors of the study include Eric Agol, Victoria Meadows and Tyler Robinson of Washington University, Timothy Livengood and Drake Deming of the Goddard Aerospace Center (NASA), Carey Lisse of Johns Hopkins University, Michael A ' Hearn and Dennis Wellnitz of the University of Maryland, Sara Seager of the Massachusetts Institute of Technology, along with David Charbonneau of the Harvard-Smithsonian Center for Astrophysics. The research was funded by the Canadian Council for Natural Science and Technology Research, the National Science Foundation and NASA's Discovery Program.
Cowan also stressed that some of the non-life-supporting planets, such as Neptune, are green, but the colors are quite stable due to methane in the atmosphere. He said: 'It is green from every angle and is always constant. If there is an ocean on the planet, it will have that color. But we can perform other tests to determine. For the earth, green changes from one place to another, indicating that it is not because there is something in the atmosphere. ' The article will be published in the August 2009 issue of the Astrophysical Journal.