Detection of an exoplanet by spectroscopy: 51 Pegase b

Subject:

The objectives of this activity are to understand the method of detecting exoplanets by measuring variations in the radial velocity ^? of the star, how to deduce certain properties of the planet from these measurements, and to understand the limitations of this method.

Level: High school
Time: approximately 1 hour

Prerequisites:

• Methods for detecting exoplanets: Radial velocities
• The Doppler effect
• Kepler’s laws
• Gravitational force
• Dual system and uniform circular motion
• Light or the electromagnetic spectrum
• Sinusoidal waves

Objectives:

• Analyse the spectroscopic data of the star 51 Peg and detect the variation in its radial velocity ^? to deduce the presence of a planet.
• Calculate its orbital period ^? and the maximum amplitude of the star’s velocity in its orbit.
• Determine the distance of planet 51 Peg b from its star and its mass based on the previous analysis.
• Consider the limitations of the spectroscopic method for detecting exoplanets.

Equipment required:

• Ruler.
• Pencil, eraser.
• Calculator.
• Tracing paper.

Subject, Appendices and correction:

• Sujet
• Correction

Author : Caroline Barban, LIRA/UFE, Observatoire de Paris