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Precession
The “wobble” of the Earth’s rotational axis, which sweeps out an imaginary cone, much like a spinning top, once every 26,000 years. Precession changes the pole star as seen from Earth. Thuban, the brightest star in the constellation Draco, was the pole star while the Egyptians built the Pyramids in Egypt. Since that time, the motion of precession has rotated the Earth’s axis away from Thuban and towards Polaris, the current pole star. In 13,000 years, Earth’s rotational axis will point towards Vega, the new pole star.
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Procyon
A white subgiant, called the “little dog star,” 11.2 light-years away in the constellation Canis Minor.
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Proxima Centauri
The closest star beyond the Sun. Proxima Centauri is a red dwarf and is far smaller, cooler, and less massive than the Sun. Proxima Centauri produces frequent outbursts of X-rays — big flares that could be deadly if you flew too close. It also has a strong magnetic field due to the hot gases rising from the star’s core, cooling as it reaches the surface, then dropping back to the center.
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Ptolemy
An ancient astronomer who codified the Greek geocentric view of the universe through his study of eccentric circles.
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Pulsars
A spinning neutron star with a magnetic field on the order of one trillion Gauss. This magnetic field accelerates electrically charged particles along the magnetic poles, forming a beam of energy that shoots into space from the poles. If the beam shines toward Earth, astronomers see a flickering beacon. The most famous pulsar, the Crab Nebula, pulses 30 times a second.
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