Finding a Habitable Planet

Not Too Far Away

An artist's concept by Lynette Cook of the planet found around Gliese 581.

The news of a new planet only three times the size of Earth and orbiting in its star’s potentially habitable zone spurs on the great speculation that it’s only a matter of time before we find a planet with some sort of life on it.

The star is called Gliese 581, a red dwarf that lies only 20 light-years from Earth. The planet is called Gliese 581g. This discovery was the result of more than a decade of observations using the W. M. Keck Observatory in Hawai’i.

Finding a planet in a potentially habitable zone means that the planet lies in an orbit around the star that is just far enough away (but not too far away) that liquid water could exist on the planet’s surface.  That water hasn’t yet been found on the Gliese 581g, but the fact that it’s in the right place — the so-called “Goldilocks zone” is important.

Water is one of the prime ingredients for life, along with warmth and organic material.  If water is eventually found on the newly discovered planet, that would make it the most Earth-like exoplanet yet discovered and the first strong case for a potentially habitable one.  To astronomers, a “potentially habitable” planet is one that could sustain life, not necessarily one where humans would thrive.  Having habitable status depends  on more than just water and an atmosphere, but those two factors really raise the odds of the planet being hospitable to life.

So, how did astronomers find this planet?  The research is based on 11 years of observations of Gliese 581 using the HIRES spectrometer on the Keck I Telescope. That instrument lets astronomers make precise measurements of a star’s radial velocity (its motion along the line of sight from Earth). Changes in that radial velocity might indicate that something is tugging on the star, inducing slight changes in its motion in space.  The gravitational influence of an orbiting planet is one reason why we might see periodic changes in the radial velocity of a host star. Multiple planets induce complex wobbles in the star’s motion, and astronomers use sophisticated analyses to detect planets and determine their orbits and masses.

NO Intelligent Life.. or Any Life… Yet

As you might expect, some commentators and reporters in the media and Web-based React-O-Sphere are already breathlessly reporting the discovery of life on that planet.   It isn’t so.  Hasn’t been found. Yet.  The discovery is of a “potentially habitable planet” not an inhabited one. There’s a distinct difference when you stop to think about it.

But, that hasn’t stopped the React-O-Sphere from saying it.  It tells me that those commentators either didn’t read the press releases carefully or didn’t understand them.  This story is a great case for the value of reading comprehension on the part of the media and Web commentators.

For the straight scoop on what HAS been found, check out the link at the top, or go here or here.  That way you can get more of the story — straight from the sources who made the discovery.

Raise Your Hand if You Think Space is Pristine

It’s Not

We all carry around in our heads this vision of interplanetary space as dark, cold,  lonely, devoid of stuff.  Well, it is. Except for all those planets, moons, rings, comets, and asteroids.  And dust.  And charged particles from the solar wind. Other than all that material, yeah, the space around the planets looks empty. But, it’s not.  Don’t be fooled.  Our solar system is full of stuff and we’re learning more about it all the time.

Some of the “stuff in empty space” comes close to Earth pretty often. There’s nothing mysterious about that.  There are many asteroids orbiting in the solar system, some far away, others in Earth’s neighborhood. It’s no surprise that astronomers spot wandering chunks of rock that sometimes come close to Earth.  Now that we have more cameras looking for such material — cameras and instruments that are sensitive to the faint light these things reflect — we are spotting more of them.  It doesn’t mean there’s MORE of that stuff out there all of a sudden. It’s always been there.  We just haven’t always had the instrumentation to find it.  Now we do, and the sudden prevalence of near-Earth asteroid discoveries simply means that now that we can spot those objects, we ARE spotting them.

Asteroid 2010 ST3 (circled in green) taken by PS1 on the night of September 16 moving against the background field of stars and galaxies. Each image is about 100 arc seconds across. Credit: PS1SC

The University of Hawai’i’s Pan-STARRS PS1 telescope just discovered an orbiting chunk of rock that will come within 4 million miles of our planet in mid-October.  It’s not a huge chunk — not planet-sized or even moon-sized. It’s about 150 feet across — enough to make a prominent entry into our atmosphere. It’s likely it would break up in the atmosphere, but there would still be a blast wave on the surface that would devastate several hundred miles of territory.

Now, this object, called 2010 ST3 is NOT going to enter our atmosphere on this pass.  But, it could (and I stress the word “COULD” because there ARE people who will take this as a sign of the impending apocalypse and start raising all kinds of irrelevant points no matter how carefully one points out that “could” and “will” are not semantically equal) hit Earth in 2098 and cause damage. But, it’s not going to hit this time, even though it is potentially hazardous. It’s one of many, many chunks of solar system that are orbiting out there, part of the system of solar system objects that astronomers are still learning about, counting, charting, categorizing, and warning us about.  Learning about objects like 2010 ST3 is part of planetary science and part of the exploration of our solar system.