I had to share this animation, taken from a press release made by NASA this morning, and YouTube’d by the ever-awesome Phil Plait (who has a great blog post about it here).  It’s an exceptionally clear and powerful illustration of just what that high-tech toy known as the Kepler Space Telescope is doing way up there in orbit.  Kepler was only just launched in March, and this data is the result of a quick test of her abilities on a previously discovered planetary system — specifially, the roughly Jupiter-sized planet known as HAT-P-7b, which is so close to its own star that it completes an orbit in a mere 2.2 days.  Measuring the exceedingly miniscule changes in the brightness of a distant star sounds like an awfully difficult means of inferring the existance of extra-solar planets (and it is!), but the animation does a spectacular job of illustrating just what the results mean.  The first big drop in brightness shown is the planet transiting its star.  The second is, amazingly, the star occulting the planet.  And the remaining fluctuations?  Those are the phases of HAT-P-7b as it orbits — just like the amount of light we see reflected off the Moon changes as it goes from new moon to full to new again!

This data shows that Kepler will be sensitive enough to detect Earth-sized planets, once her planet seeking begins in earnest.  Most of the over 350 known extrasolar planets are broiling gas giants, but little rocky planets like ours are predicted to be more numerous.  They’re out there, and Kepler will find them.

And once we do … then what?

We can use what we know about a star to determine where its habitable zone is — that Goldilocks region of not-too-hot and not-too-cold needed for liquid water to be present.  We can determine approximately how old the system is, and thus whether or not there’s been enough time for life to evolve.  And once we have a good candidate, we can do something like what LCROSS (Lunar CRater Observation and Sensing Satellite) did last week when it turned its instruments to Earth:

LCROSS: Near-infrared spectrum of Earth (NASA).

LCROSS: UV/Visible spectrum of Earth (NASA).

Yes, it’s more graphs. No shiny animation to accompany them this time, but this is still pretty cool.  These are measurements taken by LCROSS’s spectrometers, showing the spectra of our planet’s reflected light.  There’s lots of methane (CH₄), and ozone (O₃), and carbon dioxide (CO₂), and other things you can find on plenty of lifeless planets.  But there’s also oxygen gas (O₂), which is something you generally don’t find unless there’s some process continually producing it.  Oxygen is unstable, and it gets eaten up pretty quickly by various chemical processes, but here on Earth we have organisms to replenish it. Which brings us to something else showing up in this spectral analysis — a signature that could be attributed to the large amount of vegetation that covers the Earth’s surface.

This is why science is just so damn cool.

From January 6 to February 3, 1979, the Voyager I spacecraft covered a distance of 27 million kilometers during its approach of Jupiter.  A selection of photos from this period, taken at the same longitude each Jovian rotation (about once every ten hours) was assembled into a time-lapse animation by the folks back on Earth (click to watch):

Voyager I approaches Jupiter (NASA).

We’re accustomed to seeing photos of Jupiter as a beautiful but silent orb, and yet here it is, chaotic and tumultuous: a living planet, with gushing arteries of atmospheric clouds surrounding the swirling vortex of the Great Red Spot (a massive storm system several times larger than the Earth itself).

Voyager I and her sister ship, Voyager II, are still out there, thirty years later.  Still talking to us.  Still travelling.  What would you see, if you had an eternity to wander the vastness of space?

Can you see us?

Photo: NASA

The Earth, as a tiny pale dot caught in a shaft of scattered sunlight as seen from the Voyager I spacecraft, at a distance of six billion kilometers away.

Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.
– Carl Sagan, 1996