

GUEST EDITORIAL: Existence of Earth-like planets raises possibilities

11:11 AM, Nov. 7, 2013  |  Comments
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Sometimes it is refreshing to set aside the strife and stress of earthly life, look up at the night sky and contemplate the possibilities teeming in the universe.

There are more planets in our galaxy that are similar to Earth than there are people alive on Earth today.

And that's just in the Milky Way. Astronomers also have discovered an Earth-like planet in a galaxy far, far away.

Astronomers using NASA data have calculated for the first time that in our galaxy alone, there are at least 8.8 billion stars with Earth-size planets in the habitable temperature zone, The Associated Press reported this week.


There are about 200 billion stars in our galaxy, with 40 billion of them like our sun, study co-author Geoff Marcy, a researcher at the University of California at Berkeley, told the AP.

The researchers examined 42,000 stars - a small sample of the Milky Way - to find the number of planets similar to Earth. They then extrapolated that figure to the rest of the galaxy.

About 20 percent of the stars in the Milky Way that are like the sun in size, color and age have planets that are roughly Earth's size and are in the habitable zone where life-crucial water can be liquid, according to intricate calculations based on four years of observations from NASA's now-crippled Kepler telescope.

The first finding of a planet similar in size and composition to Earth outside the Milky Way was reported last week in the journal Nature by scientists at Florida's Cape Canaveral.

Early astronomers were never able to discover an "exoplanet," the term for a planet outside our solar system. In 1992, astronomers for the first time confirmed the existence of an exoplanet. After that, planet discoveries seemed to come in droves, with more than 1,000 confirmed so far and another 3,500 "candidate" planets waiting in the wings.

Most of the early planet discoveries were of gas giants, impressive but totally inhospitable to any kind of life form. Kepler has identified 10 planets that are about Earth's size circling sun-like stars and are in the habitable zone.

Kepler-78b is the first exoplanet found to be about the same size as Earth (it is slightly larger) and the same density, suggesting that, like Earth, it is made of rock and iron. It is 400 light-years away in the Cygnus constellation.

Kepler-78b is not in the habitable zone. It is so close to its sun that the planet is at least 2,000 degrees hotter than Earth.

The Earth-like planets in the Milky Way, however, are much more hospitable to life. What are the odds that there is life somewhere out there? Marcy said it means "just in our Milky Way galaxy alone, that's 8.8 billion throws of the biological dice."

So, the next time you gaze at what Irish novelist James Joyce called "heaventree of stars," remember that something just might be staring back at you.

- Knoxville News Sentinel

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