Although they sound like a cousin to the phaser, quasars aren’t a form of futuristic technology. In fact, their name is an abbreviation of the more technical-sounding quasi-stellar radio source. Despite their name’s similarity to pulsars, quasars aren’t stars. They are the nuclei of galaxies located extremely far from Earth. Astronomers can see them despite this distance because they are extremely bright and emit incredible amounts of radiation across the electromagnetic spectrum. Quasars’ brightness outshines the entire rest of the galaxy to which they belong. These distant, luminous beings offer valuable clues about how galaxies evolve.
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RADIO SOURCE The first quasars were spotted in the late 1950s and early 60s. Astronomers were puzzled by these star-like objects that emitted radio waves. Astronomers Allan Sandage and Thomas Matthews were the first to record and identify an emission spectrum of a quasar. Another astronomer, Maarten Schmidt, hypothesized that the seemingly bizarre emission spectra were normal, but shifted towards the red end of the electromagnetic spectrum. This indicated redshift and meant that the light from the objects was coming from extremely far away.
GUNN-PETERSON TROUGH The distance of quasars from us results in many strange effects that can be seen in their emission spectra. The Gunn-Peterson Trough refers to a visible suppression of electromagnetic emissions at wavelengths below a certain value. That value is known as the Lyman-alpha line. The physics behind the Lyman-alpha line are too complex to get into here, but suffice it to say that this spectral pattern is observed in quasars.
BL LAC OBJECTS
BL Lac Objects, short for BL Lacertae Objects, refer to a type of galaxy with an extremely compact and highly luminous nucleus. These galaxies possess Active Galactic Nuclei (AGN). BL Lac objects belong to a broader class of AGN known as blazars. Blazars, in turn, are differentiated from quasars due to the fact that their emission jets are pointed directly towards the observers. Although BL Lac Objects are very bright, like quasars, they can be distinguished due to relatively weak emission spectral lines.
GRAVITATIONAL LENSING
Gravitational lensing refers to the warping of space-time by massive objects. This effect impacts how we perceive quasars on Earth. Due to the supermassive black hole at the center of quasars, their light is bent as it travels towards Earth. Warped areas of spacetime bend and magnify light so that a single source of light can appear as a ring with four points of light. This phenomenon is known as an Einstein Cross.
SUPERMASSIVE BLACK HOLE
What powers these brilliant quasars? Scientists believe that at the center of every quasar is a supermassive black hole. The gas surrounding the black hole forms an accretion disc that, when heated, releases energy in the form of electromagnetic radiation. This accounts for quasars’ intense luminosity.
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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out:
It can be hard to keep all these astronomical terms straight. Here’s a helpful guide to differences between quasars and blasars..
Read about the circumstances surrounding the discovery of quasars.
Our humble Milky Way galaxy may have once been a quasar! Check out this article to see how this might have played out.
If you’re interested in hypotheticals, here’s a doozy for you: What would happen if a quasar entered our solar system? Hint: Nothing good.
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