The Goldilocks Zone

As I mentioned in an earlier post, my move from the suburbs of Columbus to the mountains of Northeast Pennsylvania was a bit of an adjustment.  However, one of the two things I love about this area that I did not get in Ohio is a dark, clear sky.  It is not quite up to the standards of the Southwestern United States, which are the most gorgeous skies I have ever seen in person, but it is certainly an improvement over the light, humid, and often cloudy skies of my childhood.  

I have recently had a renewed interest in the night sky due to some exciting astronomical news.  Years ago I owned a ten inch Meade LX200 telescope that I used on occasion to go stargazing with friends, however due to the extreme hassle of moving it over and over again, I was forced to sell it.  Since then I have tried to keep up with the news in the field of astronomy, as anything to do with space has always been a fascination of mine. The past ten years or so have been especially exciting, with the continual discovery of extrasolar planets, those that orbit around a star other than our own.

A diagram of our solar system and the approximate
range of the Goldilocks zone around the Sun.

The Goldilocks Zone

Around every star, in every galaxy, exists a Goldilocks zone (Circumstellar habitable zone to astronomers, but we'll keep it light for this crowd), a region in which a planet is likely to have water in a liquid state.  As all life as we know it requires liquid water to function, any planet found in this region around its host star is of particular interest to astronomers, scientists, and really should be of interest to everyone.  I know for me, the discovery of extrasolar planets, especially those in the Goldilocks zone, is one of the most exciting discoveries made in the past hundred years.

Last week it was announced that six planets have been discovered around star Gliese 667C (catchy name, I know), and three of these planets appear to be within the star's Goldilocks zone.  Better still, these planets do not appear to be gas giants like Jupiter, but are thought to be Super Earths, planets that are larger than Earth, but are significantly smaller than gas giants.  And the kicker: they are only twenty-two light-years away. (or a completely incomprehensible 129,326,996,000,000 miles, or 208,132,000,000,000 kilometers)

Interstellar Space Travel

The Milky Way, showing the location of the Sun
and the region most extrasolar planets have
been found.

One idea that scientists and astronomers keep trying to put into context, but often fail to do due to the inability to compare to something relatable, is how far this really is.  Twenty-two light-years doesn't sound very far, and it isn't on a galactic scale.  Gliese 667C can be considered a close neighbor. Maybe not next door, but only a few houses down.

When you try to put this number into units you use every day, like miles or kilometers, you end up with numbers in the hundreds of trillions or greater.  What is 129 trillion miles?  Nearly six billion trips around the Earth.  I've never gone all the way around once.  700 million round-trips to the sun and back.  I've never left the atmosphere.  These comparisons just don't help.

Trying to put the distance in the context of time seems to help a bit.  The fastest spacecraft on the drawing boards right now is the Solar Probe Plus, a NASA mission to study the Sun currently slated to launch in 2018, with a planned top speed of 450,000 miles per hour (200 kilometers per second).  This is pretty easy for this mission, namely because it is flying towards the sun, not away.  For simplicity's sake, lets assume we can achieve this speed flying away from the sun, and the sun's gravity will not slow the spacecraft down as it travels away (bad generalization when talking about interplanetary travel, but on an interstellar scale it is alright).

So we are traveling 450,000 mph away from Earth, directly towards Gliese 667C.  In this scenario it would only take the spacecraft around 33,000 years to get to the star system, which is about the same amount of time between when our ancestors started colonizing Europe and today.  Had only the first cavemen who set foot in the area that is now Spain launched an interstellar probe, it would only be 3,000 years away from its destination.  And that is only the difference between now and the time of Solomon.  (Actually we would still be about thirty years away, my entire current time on Earth, from reaching Gliese 667C, but its pretty close.)

Once our stone and stick spacecraft reaches the star system, lets say it starts streaming back pictures of the planets.  We would only have to wait another twenty-two years to see what it sees.  After waiting 33,000 years, twenty-two more doesn't really seem like much.

Who Cares About Exoplanets?

It's hard to explain my excitement about finding evidence of planets in other star systems, when there is no reasonable chance we will ever get to visit them in our lifetimes, our children's lifetimes, our grandchildren's lifetimes, et cetera, et cetera, et cetera.  Using today's rocket technologies, you would have to convert the entire mass of the Earth into rocket fuel to get a small spacecraft anywhere near the speed of light, required and that is ignoring the fact that you then need another Earth converted to fuel to slow down. (there is nothing in space to slow the ship down, so it would just keep going and going) 

Nonetheless, the discovery of any extrasolar planets excites me.  Just the knowledge that we are finally able to detect planets outside our solar system, something that had always been assumed, but never proven, is enough for me.  My hope is that over the next couple decades, as we discover more and more planets, a good list of places we want to visit will emerge.  Once that is done, humans will have the will to travel to an extrasolar star system. All we will need then is for technology to meet our desire to get there in less than a human lifetime.  I am cautiously optimistic that this will happen before the turn of the century.