Monday, June 30, 2008

Life On Other Planets

European scientists have recently found three "super-Earths", planets very similar to Earth's size with distances from their host star proportional to our distance from the Sun. This exciting new research is hoping to find planets where life is likely to be found. The key is finding planets with the same characteristics as Earth, and although there are unimaginably huge numbers of planets, finding one just like ours isn't as easy as it seems.

Scientists agree our twin planet would have to orbit a single star; about half the systems in the galaxy are binary stars, with gravity too harsh for life to develop. Additionally, the planet would have to be a terrestrial world like ours, not a gas giant like four of the planets (Jupiter to Neptune) in our system. The planet would have to have a suitable temperature, a breathable atmosphere, and reasonable protection from radiation.

The photo at the left is one of the first taken of Earth from outer space. One of the critical questions astronomers are trying to answer is: are planets like ours rare in the Universe, or are they quite common?
Traveling within our own Solar System is still very difficult, risky, and expensive. Finding extraterrestrial life almost certainly involves visiting other systems, a journey which is a million times more arduous. For this, it would help if we knew where we were headed. 

Using powerful telescopes here on Earth, or in orbit, has helped scientists see what kind of planets other stars have. Since the early 1990's, when the first planets outside our solar system were discovered, hundreds of planets with characteristics similar to Earth's have been found.

What makes this job difficult and time-consuming is how unimaginably big the sky is: even a tiny patch may contain hundreds of thousands of stars.Once planets considered "likely" to support life are found, there's the additional challenge of traveling farther into space than humans have ever traveled before to reach them. No one knows how to overcome this obstacle, just yet.

Still, this is an exciting discovery: to find three planets similar in size and composition to Earth orbiting a single star. The smallest of the three is about four times as large as Earth. That may sound like a lot, but it's still much closer to our planet's size than the giant planets in our own Solar System.
Additionally, the discovery demonstrates that there are planets in many unexpected places throughout the Universe. These were found in a section of space previously thought to be devoid of planets. Scientists are more interested in the broader implications of the findings: that the Universe is far more teeming with planets than was previously thought.

Last week a UK team discovered a planet thought to be less than 2000 years old, in its infancy. Studying this phenomenon will help us understand how planets form and develop in a way which encourages or prohibits life. How many stars feature planets comparable to Earth, and are there pockets of space which are particularly rich and worth exploring?

So far we've sent spacecrafts only to celestial bodies already known to be barren and lifeless. One day soon, we may send explorers to a planet just like our own.

For my previous posts on astronomy and the Universe, click here.

If you're interested in a terrific book about space exploration, with lots of glossy pictures, please check out Astronomy: A Visual Guide, by Mark A. Garlick.

No comments: