SON: Methods


Transit Method

The transit method detects the slight drop in starlight that occurs when a planet crosses in front of its parent star.  Planet hunting and follow-up is achieved by taking gigabytes of data over a period of time. The geographical locations of our sites enable 24 hour continuous observations.

Targets are selected using the ETD – Exoplanet Transit Database. ETD provides the necessary information for exoplanet transit observation which includes the Start of Transit, Mid Transit, End Transit and also the duration and depth of a transit.  The star coordinates RA and Dec and epoch are input to the observation plan. 

The database consist of images of star fields centered on the target star. Advanced software developed by SON analyze the variations in stars’ brightness. Various techniques are employed to extract light curves that represent a planet in transit as opposed to those associated with other variable stellar parameters.

To detect planetary transits the orbits must be perfectly aligned with the earth. The probability of a planetary orbital plane being directly on the line-of-sight to a star is the ratio of the diameter of the star to the diameter of the orbit. About 10% of planets with close orbits have such alignment, and the fraction decreases for planets with larger orbits. To enable us to scan large areas of the sky containing an eight element search instrument is under construction in Chile. Called The All Sky Survey SpaceObs,  this instrument is capable of scanning hundreds of thousands of stars at once.

Follow-up observations of known planets are designed to detect variations in the timing of the transit. These observations can be employed for detecting additional planets in the system with sizes potentially as small as Earth-sized planets.


Polarimetry Method

The method is designed to detect and measure the very small polarizations produced when a parent star’s light is scattered by an extrasolar planet’s atmosphere. The instrument detects starlight scattered from the atmosphere of the planet as a polarization signal which contains information relating to the planetary atmosphere or surface.

The radius of the planet and the planet temperature can be determined from the measured albedo. The position angle of polarization will enable the mass of planets to be detected through radial velocity measurements.  Astronomical polarimeters are being constructed for the Haleakeal Summit, Maui telescope and Bisdee Tier, UTas telescopes. These instruments are capable of detecting the polarized light and rejecting the unpolarized beams (starlight).