Trials and Tribulations of Hunting Needles in Hay Stacks
I thought it might be worth briefly talking about what it is I'm actually aiming to study, and then discuss what the challenges are that I'm going to be facing.
The light curves have very distinct features, which can tell us a lot about the planet itself. The horizontal parts of the curve are the normal 'brightness' of the parent star, in this case normalized to a flux of 1. As the exoplanet begins to transit across the limb of the star (ingress), the brightness begins to dip. The flat bottom of the curve is the period of the planet passing across the disc of the star, and this is the minimum flux intensity. Then as the planet transits across the second limb (egress) the flux begins to increase, once again reaching the pre-transit flux of one.
The duration of the minimum flux (i.e. when the planet is transiting across the face of the star) can tell us information about the distance between planet & star. How fast the planet is moving around the star (i.e. its orbital period) and also give the opportunity (with the correct equipment) to gather a spectra of the exoplanets atmosphere, though that is currently beyond the scope of the project.
The next important challenge that I face for this project are more out of my control. The first is transit time. When the planet will actually transit the face of the star. Obviously, this has to be at a point when it is A) Dark in the UK, and B) observable in the Northern Hemisphere. This limits the number of targets greatly, but does not rule out the project completely. The NASA Exoplanet Archive (The button at the top of this page) has a great calculating spreadsheet which allows you to figure out which targets are ideal for your observing location and times.
The next physical challenge is the exoplanets orbital inclination. If the planet passes directly across the centre of the stellar disc as observed from earth, this makes the transit light curve very obvious. If the planet has an orbit which is inclined above or below the centre of view (as seen from Earth) this can alter the light curve, making the depth of the curve much shallower. Its this that can then make observations for small telescopes far more tricky.
These factors have been what I have worked from to select a preliminary lists of targets, & once I've resolved some of the other issues, these will be the first to be observed.
Until now, the science of exoplanet detection has been the domain of the professional, with equipment that was paid for by a conglomerate of countries. It is a fairly recent thing that amateurs have attempted to do exoplanet detection. The famous planet hunting space telescope Kepler has confirmed detections of several hundred exoplanets, and it is this which I will be using as a primer for my own work down the line.
As I mentioned earlier, the telescope has a very long focal length (of about 3m) which makes pulling an image to focus on the CCD a real challenge. its taken a number of nights of head scratching and 'going back to the drawing board' to get a first image.
From this point, I intend to refine the exposure of the CCD, and to attempt basic photometry, on some variable stars as another preliminary activity, before moving on to the exoplanet work.
It is my intention to report on this as time goes on.