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Among the first principles of the great fundamental mysteries of astronomy is that when we gaze up at the stars we’re not only gazing into space but also that we’re looking back through time. And because of the limitations of the speed of light and distances involved, the furthest objects we can see are in fact just the light of them from millions and billions of years ago. That has always left astronomers and cosmologists with a difficulty in mapping the stars, how can you tell precisely how far away objects are and therefore how old they are? The answer has so far been in what’s called a Type 1A Supernova. These particular stellar explosions detonate with approximately the same brightness no matter where they are, they are constant, and that provides astronomers with what they call in the ancient tradition of Copernicus and Galileo “standard candles” by which to measure distance and therefore: age.
Cosmos explains the math:
“A standard candle is an astronomical object that has a known absolute magnitude. They are extremely important to astronomers since by measuring the apparent magnitude of the object we can determine its distance using the formula:
m-M = 5 log d – 5
where m is the apparent magnitude of the object, M is the absolute magnitude of the object, and d is the distance to the object in parsecs.
The most commonly used standard candles in astronomy are Cepheid Variable stars and RR Lyrae stars. In both cases, the absolute magnitude of the star can be determined from its variability period.
Type Ia supernovae are also normally classed as standard candles, but in reality they are more standardisible candles since they do not all have the same peak brightness. However, the differences in their peak luminosities are correlated with how quickly the light curve declines after maximum light via the luminosity-decline rate relation, and they can be made into standard candles by correcting for this effect.”
Much like picking up a map at a gas station (age check), that’s all well and good for our local region of galactic space, but as we get further out and further back in time we run into some problems.
As Popular Science’s Charlie Wood wrote,
“With current telescopes, researchers can’t see type 1a supernovae beyond nine to ten billion years ago (because light takes billions of years to reach earth, looking out into space also means looking back in time.) Without any visible supernovae, cosmologists—researchers who specifically study the evolution of the cosmos as a whole—are left largely in the dark as to what went on during the universe’s first four billion years.”
In short: to see further out and properly gauge distance and time… we need a new candle. Enter Quasars and an amazing new discovery from Italy.
The Mysteries of Quasars Are Starting to Be Revealed.
A Quasar or ‘Quasi Stellar Object’ is what you get when a Supermassive blackhole, usually at the center of a galaxy pulls so much matter toward itself that it burns with so much intensity that the white-hot energy and radiation released quite literally outshines its whole galaxy. Here’s the bonus and what makes it all work: Quasars have been around for a very, very long time, almost all the way to the beginning of the cosmos researchers think. Point blank: we can detect them further out than type 1A Supernovae.
Now, thanks to some very intrepid astronomers, researchers believe Quasars can serve as the new “standard candle” to gauge distance and time. Chris Wood again explained, “Since astronomers can pick out the blaze of quasars during the universe’s first billion years, could these objects serve as brighter, more penetrating standard candles?”
“Some astronomers believe that they can, thanks to one crucial property. Quasars pump out ultraviolet light, and some of these ultraviolet rays smash into a surrounding cloud of hot electrons, unleashing higher energy X-rays. Because the ultraviolet light makes X-rays in a predictable way, a quasar’s X-ray brightness is tied to its ultraviolet brightness in a fixed manner, no matter how far away the galaxy is. By comparing the ultraviolet and X-ray emissions with how bright or dim a quasar appears overall, astronomers can use it as a cosmic mile marker.”
Remember the team in Italy? Well a theory is just a theory until we can prove it, and it looks like a team of Italian astronomer using the Sloan Digital Sky Survey and the Chanra X-Ray Observatory might have it locked down. They claim that the relationship between ultraviolet and X-Ray emissions from quasars can be traced all the way back to approximately 1.3 billion years after the Big Bang.
Susanna Bisogni, an astrophysicist at the National Institute for Astrophysics in Milan, Italy said “This was a necessary check for us to be able to use this method for measuring distances and to be sure that we were not using a tool that’s changing in time,” Bisogni’s team published their findings in the journal Astronomy & Physics on Sept. 7th, and of course peer review is going to take a long, long time as it should. So don’t look for the “standard candle” to change tomorrow, but if these massively bright, streaming beacons in the night can guide our exploration of the cosmos, then it’s pretty wild to think that these extremely convenient mileposts were left for those clever enough to look.
