Direct Imaging: Say “Cheese/Vortex Coronagraph”!
In a more convenient universe, an astronomer could simply treat his $8,000,000 mountain telescope like a Nikon camera and take glamorous snapshots of unsuspecting planets while their backs are turned. Unfortunately, distant planets tend to be more elusive.
For now, the closest thing we have to such a photographic means of planet viewing is
Direct Imaging. The method holds much potential, including the ability to find planets in wider orbits than usual, and to characterize planetary atmospheres. Recent advances in 2010 have allowed for much better images, thanks to
adaptive optics, which break through atmospheric distortions, and the
vortex coronagraph, a telescopic attachment which blocks out the direct light from a star. This allows nearby objects (like exoplanets) to be viewed, unhidden by star-glare
(Thompson, Space).
Direct Imaging Used In Planet Hunting
That being said, direct imaging’s overall strength as a detection method is thus far limited Prior to 2010’s advances, its successful targets have been limited to planets much larger than Jupiter, wide in orbit from their sun, and yet still hot enough to emit infrared radiation intense enough to pick up. Suffice to say, this net doesn’t dump mountains of fish.
In fact, many of the challenges to direct imaging are representative of the challenges to planet hunting as a whole. As you may have heard, the universe is big. Hunting for planets in a near limitless and constantly moving sea of stars from our limited vantage point has some serious obstacles. First, there is distance: seeing something so far and so small through the glare of a star (up to 10 million times brighter than the planet itself) generally forces us to look at planets indirectly
(Clavin, NASA).
Then there’s the matter of angle. From the Earth’s vantage point, our views of other planets are inherently limited to the angle afforded by our place in the universe. That means exoplanets could be orbiting at an angle which does not pass between Earth and that planet’s sun, which to us is as good as invisible. These factors make direct imaging largely impractical for the time being. Meanwhile, the two following methods discussed in this series, which serve as the primary methods of exoplanet detection, owe their success to far more indirect means.
Next in The Planet Hunting Series
Tune in for the next part of our planet hunting series as we investigate the
Transit method, and see how the twinkling of stars might betray a planet's presence.
