Work experience students observe exoplanet transit with FT South

An FT “Themed Observing Day” on Wednesday 20th June saw several schools (including Glenlola Collegiate, Sint Augustinus Institut, Paulet High School, Whitchurch High School and Ercall Wood Technology College) observing Corot-2b using FT South. The users took many images of the target CoRot-2b, each with the same exposure time between 11.30 and 15.00 UT. 

As part of their work experience week with the FT team at Uni. of Glamorgan, 6th formers David Hardy (Bishop of Llandaff HS) and Thomas Ham (Glantaf HS) obtained data as part of the programme, and then carried out a quick analysis to see whether a transit had been detected. Their results (below) show a very clear dip in the brightness of the star, as the planet blocks out some of the light.

 Corot-2b was discovered on 20th December 2007 by the French CoRot telescope, and was the second extra solar planet to be discovered by the mission. Corot-2 is a G type yellow main sequence star that is slightly cooler than our Sun, but a lot more magnetically active. It is located 930 light-years away towards the constellation of Aquila. The apparent magnitude of this star is 12 and thus it cannot be seen by the naked eye and requires a telescope to be observed. 

Corot-2b is classed as a large hot Jupiter. Hot Jupiter’s are a class of extra solar planets which are close to or larger than the mass of Jupiter. It orbits its star once every 1.7 days, so the transit of the planet can be regularly observed. It takes about 125 minutes for CoRot-2b to transit its star. Due to how close the planet is to the star, it is very hot. However the temperature is even hotter than would be expected, which hints at a possible past gravitational interaction with another planet, similar to the interactions between Io and Jupiter. Because of these factors, the planets surface temperature stays at around 1500K. The radius of Corot-2b is 1.429 times that of Jupiter and as a result the planet is around 3.3 times the size of Jupiter.The large mass of the planet means it also has a large gravitational field, nearly 4 times the gravity on Earth. 

The transit of the planet is measured by analysing the light intensity (coming from the planets parent star) over an extended period of time. The data is then collected and can be graphed. When the light received from the parent star is at its lowest level, the planet has passed in front of the star and is blocking some of the light. Finding the time duration of this intensity change makes it possible to measure the diameter and consequently the size of the planet. This also makes it possible to calculate the mass and gravity of the planet, which is why scientists are so keen to observe such transit events. 

Report by David Hardy and Thomas Ham.