Final answer:
Astronomers use the radial velocity and transit methods to measure a planet's mass and size, which allows them to calculate its density and hypothesize about its composition. For instance, a high-density.
Step-by-step explanation:
To determine the density of a planet around the star 83 Per in the Perseus constellation, astronomers use both the radial velocity technique and the transit method. The radial velocity technique measures shifts in the star's spectrum due to the gravitational influence of an orbiting planet, providing an estimate of the planet's mass. The transit method determines the size, or radius, of the planet as it passes in front of its star, causing a temporary dimming. Density can be calculated by the formula ρ = mass/volume. Knowledge of both mass and volume enables astronomers to classify the planet. For example, a low density would suggest a gaseous planet, like a hot Jupiter, while a high density indicates a rocky planet, akin to a super-Earth.
Comparing this planet's density with those in our solar system helps in determining its composition. Terrestrial planets like Earth or Mercury have higher densities due to their rocky composition, while gas giants like Jupiter and Saturn have much lower densities. As the text mentions, super-Earths and mini-Neptunes have masses 3-10 times that of Earth and can be primarily rocky or have substantial gaseous envelopes. Planets in the mass range of more than 10 times that of Earth typically have significant gaseous atmospheres, similar to Uranus and Neptune.