Science Projects

Exoplanets with the University of Portsmouth

Exoplanets

(Planets orbiting stars other than the Sun)

Before 1992 we could only speculate about the existence of planets outside of the solar system. Then Aleksander Wolszczan and Dale Frail discovered three planets orbiting a neutron star (P1257 +12) from radio observations made at the Arecibo Observatory in Puerto Rico, and three years later Michel Mayor and Didier Queloz found a massive planet around the star 51 Pegasi using spectroscopy to detect its wobble caused by the planet (Radial velocity method).

Over the last quarter of a century the number of confirmed exoplanet discoveries has risen to 3,791 (as of September 2018) using the methods shown in table 1 below:

Confirmed Exoplanet Statistics (NASA Exoplanet Archive)
Discovery Method Number of Planets
Astrometry 1
Imaging 44
Radial Velocity 686
Transit 2958
Transit timing variations 15
Eclipse timing variations 9
Microlensing 64
Pulsar timing variations 6
Pulsation timing variations 2
Orbital brightless modulations 6

By far the method that accounts for the majority of these discoveries is the Transit method, where the exoplanet’s orbit takes it directly across our line of sight to its star. This trajectory causes the star’s brightness to dip by a small amount, which depends on the radius of the planet relative to that of the star. For larger exoplanets orbiting close to their star (hot Jupiters) this dip in brightness is large enough to be detected with our 24” Ritchey-Chr├ętien reflecting telescope using a sensitive CCD camera. Over a number of years we have been mentoring students from University of Portsmouth in projects to observe Transiting Exoplanets, and to produce and analyse light curves from this data. An example of such a light curve is shown in figure 1 below:

Figure 1 - Light curve of Transit of WASP-10 b - 20/21 October 2016

We make extensive use of the Exoplanet Transit Database operated by the Variable Star and Exoplanet Section of the Czech Astronomical Society to determine suitable exoplanets to observe.

We hope to start using different photometric filters to produce light curves of different wavelengths, and possibly use our spectrograph to see if we can detect any differences between the spectra in and out of transit.

This article has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.