Transit of Exoplanet TrES-1b From My Backyard
It might seem silly to suggest that you can see a planet many hundreds of lightyears away orbiting another star from your own house with off-the-shelf equipment, but amateur astronomers like myself have been doing it for over a decade! How? Using the same method professionals do - specifically the transit method. Modern commercial CCD and CMOS cameras are sensitive enough to detect the minuscule change in brightness as an exoplanet passes between its parent star and us. And it is a tiny drop in brightness, between 10 and 20 parts per thousand for the largest of planets.
It's these large, close-in planets that are accessible to amateur astronomers, thanks to the relatively deep transits and fast orbits that are easily detectable and can be fully captured in a single night of imaging. This is one of my most recent observations of such a transit. The planet in question is TrES-1b, a world a little larger than Jupiter in a scorchingly-tight orbit that lasts just 3 days. Such planets are called hot Jupiters for obvious reasons. They are large, low-density volatile-rich worlds whose proximity to their star heats their atmospheres to many hundreds to thousands of degrees. In the case of TrES-1b, the average temperature was directly measured with the Spitzer infrared space telescope to be Over 786 °C.
Using the software package AstroImageJ, I produced a lightcurve showing the change in brightness over the course of the night. It is readily apparent when the transit begins, as the star's light drops off and then stabilizes. There's a lot that can be inferred from just this portion of the plot, but the primary information that can be gleaned is the planet's radius (from the depth of the dip) and the length of the orbit (from the frequency of transit events and the duration of each transit). The field image on the right shows the target star itself (circled in green) and the comparison stars (in red) used as references to measure the brightness against.
