transit

Measuring an exoplanet transit

Objectives: 

After doing this activity you should be able to:

  • Use SalsaJ to do photometry for an exoplanet transit
  • Use a spreadsheet to create a light curve showing how the brightness of the target star changes over time 
  • Describe how the light curve shows that as the planet goes in front of the star it blocks some of the light
This activity, like Agent Exoplanet, allows you to use sample data to measure the change in brightness of a star as a planet passes in front of it. In this activity you will use SalsaJ, a free amateur photometry software program, to measure the brightness of the star by hand. You will then use a spreadsheet to plot your results as a graph and see if you can see your light curve.

WASP-41b: A Transiting Hot Jupiter Planet Orbiting a Magnetically Active G8V Star

We report the discovery of a transiting planet with an orbital period of 3.05 days orbiting the star TYC 7247-587-1. The star, WASP-41, is a moderately bright G8 V star (V = 11.6) with a metallicity close to solar ([Fe=H] = -0.08 +/- 0.09). The star shows evidence of moderate chromospheric activity, both from emission in the cores of the Ca II H and K ines and photometric variability with a period of 18.4 days and an amplitude of about 1%. We use a new method to show quantitatively that this periodic signal has a low false-alarm probability.

Published in PASP, 2011, 123, 547-554

The WASP-South search for transiting exoplanets

Since 2006 WASP-South has been scanning the Southern sky for transiting exoplanets. Combined with Geneva Observatory radial velocities we have so far found over 30 transiting exoplanets around relatively bright stars of magnitude 9--13. We present a status report for this ongoing survey.
To appear in the proceedings of the OHP conference "Detection and dynamics of transiting exoplanets", 23-27th August 2010

Extrasolar Planets History and Detection

Extrasolar planets are planets orbiting stars outside our solar system.The first extrasolar planet discovery was confirmed in 1992, although they had been predicted long before. Planets are difficult to detect directly because they are so much dimmer than the stars they orbit. The Sun is a billion (109) times brighter than Jupiter and 10 billion (1010) times brighter than the Earth. 708 extrasolar planets have been discovered as of 7 December 2011. Astronomers use 5 main methods to find extrasolar planets.

Photometry of an Exoplanet Transit with SalsaJ

Discipline: 
Education

Download SalsaJ from the European Hands On Universe Website. (Until further notice, please download version 1.4, not version 2.0, which does not yet have full photometry features.)

Launch SalsaJ and download our lightcure plotter spreadsheet ( you will need a spreadsheet application such as Excel, OpenOffice Spreadsheet or Numbers).

Download and unzip sample data for one of the extrasolar planets below:

Tags: 
transit
exoplanets
photometry
SalsaJ

CoRoT-9b, the first transiting temperate exoplanet

The CoRoT satellite, operated by the French space agency CNES, has discovered a Jupiter- sized planet orbiting a star similar to the Sun in the constellation Serpens Cauda at a distance of 1500 light-years from the Earth. The parameters of this gas giant, which has features in common with the majority of exoplanets discovered so far, represents a valuable standard model when it comes to identifying new Jovian-type bodies with moderate temperatures.

WASP-17b: an ultra-low density planet in a probable retrograde orbit

We report the discovery of the transiting giant planet WASP-17b, the least-dense planet currently known. It is 1.6 Saturn masses but 1.5-2 Jupiter radii, giving a density of 6-14 per cent that of Jupiter. WASP-17b is in a 3.7-day orbit around a sub-solar metallicity, V = 11.6, F6 star. Preliminary detection of the Rossiter-McLaughlin effect suggests that WASP-17b is in a retrograde orbit (lambda ~ -150 deg), indicative of a violent history involving planet-planet or star-planet scattering.
WASP-17b's bloated radius could be due to tidal heating resulting from recent
Anderson et al. 2009, submitted to ApJ

WASP-19b: The Shortest Period Transiting Exoplanet Yet Discovered

We report on the discovery of a new extremely short period transiting extrasolar planet, WASP-19b. The planet has mass Mpl = 1.15 ± 0.08 MJ, radius Rpl = 1.31 ± 0.06 RJ, and orbital period P=0.7888399 ± 0.0000008 days. Through spectroscopic analysis, we determine the host star to be a slightly super-solar metallicity ([M/H]=0.1 ± 0.1 dex) G-dwarf with Teff=5500 ± 100 K.
Hebb et al. 2010, ApJ, 708, 224

An orbital period of 0.94 days for the hot-Jupiter planet WASP-18b

The ‘hot Jupiters’ that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which they were born, or by an alternative mechanism such as planet–planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only 0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory.
Hellier et al. 2009, Nature, 460, 1098

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