Pulsars: How The First ‘False Alien’ Signal Opened Up A New World In Astronomy

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Sometimes, what nature gives you is even better than what you hoped for.

“Science doesn’t always go forwards. It’s a bit like doing a Rubik’s cube. You sometimes have to make more of a mess with a Rubik’s cube before you can get it to go right.” –Jocelyn Bell-Burnell

If you wanted to search for aliens, you might look into space for regular broadcast signals similar to what we create on Earth.

*This all-sky map shows 24 pulsars — including 16 new ones — measured and identified by NASA’s Fermi satellite. Image credit: NASA/DOE/Fermi LAT Collaboration.*

In 1967, a radio source emitting regular, 0.04-second long pulses every 1.3373 seconds was found for the first time using a scintillation array.

The data from the first pulsar ever found visualized and stacked. Image credit: Graphis Diagrams: The Graphic Visualization of Abstract Data, edited by Walter Herdeg, The Graphis Press, Zurich, 1974. Later made much more famous as a Joy Division album cover.

After the “noise” explanation was ruled out, the next thing people turned towards were intelligent extraterrestrials.

Artist’s conception of worlds around PSR 1257+12, the first system (discovered 1992) with verified extrasolar planets. Pulsar systems can have planets, but they themselves are not indicative of aliens. Illustration credit: NASA/JPL-Caltech/R. Hurt (SSC).

There was no natural mechanism in existence that would have explained it at that time, so turning to aliens was logical, if ultimately incorrect.

Instead, it turned out to be radio emissions from a pulsar, PSR B1919+21, the first one ever identified as such.

*The Vela pulsar, like all pulsars, is an example of a neutron star corpse. Image credit: NASA/CXC/PSU/G.Pavlov et al.*

Formed when the core of a star going supernova collapses, pulsars are rapidly-rotating balls of neutrons, where the surrounding matter is accelerated by an incredible magnetic field.

A pulsar, made out of neutrons, has an outer shell of protons and electrons, which create an extremely strong magnetic field trillions of times that of our Sun’s at the surface. Image credit: Mysid of Wikimedia Commons, based on work by Roy Smits.

As the neutron star rotates, two jets change their position through space, causing you to see a “tick” of a pulsar each time it passes by a location.

*Pulsars can also turn on or off by the presence of infalling matter, where streams disrupt the pulses temporarily. Image credit: NASA / GSFC.*

In binary orbits, we’ve seen pulsars precess where they become invisible and then visible again.

As two neutron stars orbit each other, Einstein’s theory of general relativity predicts orbital decay, and the emission of gravitational radiation. Image credit: NASA (L), Max Planck Institute for Radio Astronomy / Michael Kramer.

The oldest are the Universe’s most stable natural clocks, accurate to 10–15seconds over decades.

*One of the goals of gravitational wave observatories like LIGO and LISA are to detect the gravitational waves emitted by pulsar orbits. Image credit: ESO/L. Calçada.*

Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals and no more than 200 words.

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Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all