23 Mar 2009
There is a brand new satellite above called Kepler, and orbiting with it is a whole new wave of science rhetoric. Kepler has rejuvenated the question that really needs no rejuvenation: the perennial question about whether another Earth-like planet exists which could harbor life.
Kepler's whole purpose is to pick up the very slight dimming of stars as tiny orbiting planets move in front of them. With enough data one can estimate the size and orbit of those planets. The hope is to find "earthlike" planets, something up until now we have been unable to detect.
But what exactly does "earthlike" mean?
Well, what "earthlike" means, compared to what it implies, are two vastly different things. According to the Kepler team it is simply defined as a rocky planet that abides somewhere in what is called the "habitable zone" around its star. That would be an orbit which allows it to have water in its liquid state; not too far from its sun so as to freeze its water, not so close so as evaporate it all away.
But the more popular understanding of "earthlike" heavily implies a duplicate earth: A big blue planet with continents and oceans and clouds - and life.
We all know that if Kepler does find a planet roughly the same size as Earth and orbiting in the habitable zone, that many in the popular press and some scientists will leap onto that to quickly conclude that life must be there. It will be an unfounded conclusion which will make headlines everywhere.
But before readers here jump on that inevitable Bandwagon of Life we should ask some questions - and lots of them. Here is a very small check list.
Is the planet's star the correct type of star, not too big, not too small? Is the parent star alone or does it have some orbit-disrupting partner? Does the planet have the just-right size to hold on to a just-right atmosphere? Does the planet have any water at all? Does it have giant planets perfectly placed in outer orbits and locked there, protecting it from life-destroying bombardment? Is the planet's orbit nearly circular, if not perfectly circular? Does it have a life-giving, perfectly placed moon to keep it steady? Has it cooled to a solid rock or is it alive with plate tectonics?
The list is endless. But if you want a home for life, especially complex life, you had better have the perfect planet, not just a rock in the right place. But there is one more thing, one more very important thing. Even if a newfound planet were an exact doppelgänger of Earth in every way, it doesn't follow that life must be there. But that's a subject for next time.
09 Mar 2009
More than 30 years ago this week, a discovery was made which all of six people in the world will celebrate - the discoverers and their moms. But it was a fascinating revelation, and in our attempt here to honor the disenfranchised niches of astronomy and to give you insight into the crazy, serendipitous things that happen in the land of science, today we will look at how the rings of Uranus were discovered.
When I was a kid, way back when, only Saturn had rings. The other big guys out there - Jupiter, Uranus and Neptune - were ringless balls of gas.
But then, on 10 March 1977, astronomers studying the atmosphere of distant Uranus were surprised to find blips in their data. Here’s what happened.
The big planets out there are so very far away it is difficult to get much detail about them from here. So astronomers have to think of ingenious ways to bleed them of useful data.
One way is to allow distant stars to help. How? When a planet passes in front of a star the star’s light is, obviously, hidden from us. But in those moments just before it disappears behind the planet, the starlight has to pass through the atmosphere of yon planet. The waves gets distorted and certain wavelengths get kidnapped altogether. Really smart people can read the light we get - or don’t get - from the star and deduce what was in the planet’s atmosphere that ran interference.
Well, this very scenario was about to play out for three astronomers, James L. Elliot, Edward Dunham, and Douglas Mink back in 1977 when they noticed something strange. Before the star even got near to Uranus’ atmosphere, the distant star’s light dimmed and brightened, five times in total, like it was blinking on and off. Then, after the star reappeared on the other side of the planet, it did the same thing!
The only possible explanation of successive blinkings, mirrored on both sides, was that Uranus must have a tiny ring system around it, composed of at least 5 thin rings.
In fact, it did! The spacecraft Voyager 2 imaged those rings in its 1986 fly-by. They were just several kilometers thick and made of darker material than Saturn’s famous system which are the reasons why they escaped detection for so long. There are now a total of 13 known rings around Uranus.
But it wouldn’t end with Uranus. In 1979, Jupiter’s almost invisible rings were discovered, and in 1989 distant Neptune was caught with some.
But how those were all discovered is a story for another day.
Until next time, clear skies!