Category Archives: exoplanets

exoplanets, Kepler mission

Kepler in Search of Distant Earths

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A Near-Earth-size Planet Isn’t Necessarily JUST Like Earth

A artist's concept of Kepler-452b, a near-Earth-sized planet discovered by the Kepler space telescope. Courtesy NASA/Kepler
A artist’s concept of Kepler-452b, a near-Earth-sized planet discovered by the Kepler space telescope. Courtesy NASA/Kepler

The news last week that the Kepler telescope had found a close “cousin” of Earth circling a sun-like star really brought out the speculation among people who don’t actually study planets for a living. The press, of course, ran with the story, calling it “Earth 2.0” and “Earth-like”, neither of which is quite true. However, despite the tendency of supermarket rags as well as serious press to jump on stories like this and carry them to illogical extremes, the discovery of this planet IS a milestone in exoplanet research.

Kepler-452b IS likely to be a rocky world similar to Earth, although astronomers haven’t confirmed that yet. It’s in the habitable zone of its star, so that means liquid water could exist on its surface. Whether it has water, or even an atmosphere, is all still to be determined. This planet is near-Earth-size, meaning it’s close to our planet’s size. Actually, it’s 60 percent larger than Earth, and its 385-day year is slightly longer than our 365-day year. It’s about a billion and a half years older than Earth, which has interesting implications for the evolution of life. Life began on Earth some 3.8 billion years ago, and this new planet has had a LOT longer than that to cook up some life.

Still, that’s not enough to make it Earth 2.0.

Yet.

For that to happen, we’ll need to know more about its atmosphere — including finding any telltale tracers for life. The planet’s star is very much like our Sun, and in the grand scheme of things, since life evolved to take advantage of what the Sun has to offer, it will be interesting to find out, someday in the distant future, what sort of life Kepler-452b has got on its surface.

All of us who read science fiction know about the countless worlds that populate the stories we read. Many times they ARE Earth-like, but supporting entirely different forms of life than what we have here. That makes sense — the universe is the ultimate generator of infinite diversity in infinite combinations. The boundary conditions — that is, the starting collection of compounds from which life can arise — may well be slightly different from what we know here on Earth. Or, it could be a LOT different. And those differences all but guarantee that life elsewhere isn’t going to look like us.

But, it’s fun to think about life elsewhere as we gaze at a starlit sky, or browse through the artist’s concepts of worlds that Kepler and its partner observatories have found. That’s the sort of stuff that keeps us going, striving to explore ever further out in the galaxy. It’s what we do.

astronomy, exoplanets

Where are Planets the Most Common in Our Galaxy?

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Maybe Everywhere, It Turns Out

This shows where Kepler has aimed its planet-finding instruments (where it says “most known exoplanets”; OGLE is scanning the entire sky, and has found several planets between the Sun and the galactic bulge. Courtesy NASA.

As everybody knows, the Kepler Mission has been finding planets in the little section of the galaxy it has been studying for some years now. More than 4,000 planet candidates are out there, spied out by Kepler’s instruments. But, are those the only planets “out there”? Of course not. Astronomers think that exoplanets are ubiquitous—that is, they’re everywhere. One in five stars has Earth-similar planets orbiting in their habitable zones (the regions where liquid water could exist on their surfaces). Most stars in our galaxy have at least one planet.

That’s pretty reassuring if you’re into the search for other worlds. So, here’s some more good news: Spitzer Space Telescope and a ground-based observatory called the OGLE Warsaw Telescope at Las Campanas Observatory in Chile, spied a gas giant planet about 13,000 light-years away from us toward the central bar of the Milky Way Galaxy. OGLE was built to survey the sky looking for planets, and Spitzer is uniquely positioned to give us an infrared look at planets once they’re found.

This artist’s conception shows a planet half as massive as Jupiter located 13,000 light-years from Earth. It was detected by the Optical Gravitational Lensing Experiment and NASA’s Spitzer Space Telescope using microlensing. Spitzer provided parallax measurements that allowed scientists to determine how far away the planet is. Christine Pulliam (CfA)

Astronomers are interested to find out if planets are more common in the region where this one was found, part of the galaxy’s central bulge. The center of the galaxy is likely to give us a view of more stars, and more stars means more chances for an event called “microlensing” to take place. That happens when one star passes between us and other one; as it does, the nearer star’s gravity acts as a lens to magnify and brighten the more distant star’s light. It can also reveal the presence of a planet circling the foreground star.

Astronomers are using microlensing to find and characterize planets up to 27,000 light-years away in the central bulge of our galaxy, where star crossings are more common. This technique has yielded about 30 planet discoveries so far, and the most distant known planet it has found is about 25,000 light-years away from us.

Astronomers use OGLE to find the planets, and Spitzer to pinpoint their exact locations, which is a long and complex process. The results, however, are expanding the number of known planets and their locations, and giving even more evidence to astronomers that planets are pretty commonplace across the galaxy.