The Dilemma: You boned up all night on Miss Cleo and star signs only to find out her passion’s actually astronomy.

People You Can Impress: astrophysicists, astronomers, and Jodie Foster’s character in the movie Contact

The Quick Trick: Pulsars are pulsing stars. Quasars are quasi-stars.

The Explanation:
When a huge star goes supernova, it collapses into a dense, dark neutron star. This thing is pretty odd—a small star that’s about as big across as the length of Manhattan, but more massive than the sun. They’re too massive to be a white dwarf (a threshold of 1.4 times our sun’s mass), but not massive enough to be a black hole.

The pulsar, a rapidly spinning neutron star, was discovered in 1967 by Antony Hewish and Jocelyn Bell. Together the pair detected electromagnetic radiation being “broadcast” at regular intervals, which they believed might have been signals from aliens. Their half-serious theory of “little green men” spurred them to jokingly dub their discovery LGM-1. It now goes by the more appropriately sedate designation PSR 1919 + 21 (that means it’s a pulsar located at right ascension of 19 hours, 19 minutes, and 21 degrees declination. Astronomers, you see, do not like the funny).

Pulsars are so called because they “pulse” with emissions at a steady rate. For example, PSR 1919 + 21 pulses every 1.337 seconds. Of course, there are several varieties, but the most common are rotation powered. These pulsars rotate incredibly fast, throwing off beams of radio waves or X-rays from their magnetic poles. Like a lighthouse, which to a distant observer would appear to “pulse,” pulsars only appear to pulse. We only see the light when the beam points our way.

Quasars also emit radio waves and radiation but are not technically stars. They’re said to be starlike because they emit light. In fact, they are the brightest objects in the universe, more luminous than several thousand galaxies put together. So why aren’t they that bright from where we’re sitting? And more important, how did they go undetected until the 1950s? Well, the answer is that they’re just too old, meaning they were a feature of the earlier universe. Remember, the farther away something is in the universe, the older it is, because the light takes so long to get here. Plus, they’re moving away from us at an amazing clip.

Today eggheads are still arguing about what quasars actually are. Some say they are a type of galaxy formed around a supermassive black hole. Some even believe that our galaxy was once a quasar. If that’s the case, all you parents out there worried that your lil’ galaxy might be a quasar, relax. It’s just a phase.