(Later, we’ll relax this restriction.) Radial velocity measurements of Proxima Centauri collected over the past 16 years are compiled in Figure 2. We will also assume that their orbits are circular, which is consistent with observations, and begin by treating the simplest case where the orbits are viewed edge-on from Earth. In the following, we will assume, where and are the masses of the planet and star, respectively. Calculating the exoplanet’s mass and orbital radius Our goal is to help students share the excitement of this new discovery through their understanding of introductory mechanics.Ī. In this post, we will use the data reported in Reference 1, plus the strategy presented in Section 8.12 of PPE, to calculate the mass and orbital radius of the exoplanet Proxima Centauri b. Red dwarfs are the most common stars in our galaxy, so if this particular red dwarf harbors a life-supporting planet, it is likely that the Milky Way, which contains over 100 billion stars, is brimming with life.
The discovery of Proxima Centauri b is exciting because its orbit lies within the “Goldilocks,” or temperate, zone of the star, where the planet’s surface temperature would allow water to exist in liquid form – a likely prerequisite for life. The planet, called Proxima Centauri b, was detected by the radial velocity method: the orbiting planet causes the star to execute a much smaller orbit of its own (as required by momentum conservation), and light from the star is Doppler-shifted due to its radial motion relative to Earth. In August (2016), astronomers at the European Southern Observatory in Chile announced the discovery of an Earth-sized exoplanet orbiting the red dwarf Proxima Centauri, the nearest star to our Sun (Ref.
Inset: Proxima Centauri is the Sun’s nearest neighbor, 1.294 pc (4.224 ly) away. The binary star Alpha Centauri is also visible.
Figure 1: Artist’s conception of sunset on Proxima Centauri b.
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