Glossary P

Parallax: The apparent shift in position of an object when it is observed from different locations.

Parsec: A distance equal to 3.26 light-years.

Perigee: The point on its orbit at which a body that is revolving around the Earth is at its closest to the Earth.

Perihelion: The point on its orbit at which a planet or other Solar System body is closest to the Sun.

Photosphere: The thin gaseous layer at the base of the solar atmosphere.

Planet: A body that is much less massive than a star, revolves around a star and shines by reflecting that star’s light.

Planetesimal: One of a large number of small bodies, composed of rock or ice from which the planets were eventually assembled.

Prominence: A flame-like plume of gas that follows magnetic field lines in the solar atmosphere.

Pulsar: A rapidly rotating neutron star from which we receive brief pulses of radiation.