Quasars are the most energetic objects in the universe. They are so bright they
can be seen from across the universe and so distant that they take us back to a
time when the universe was very young. Now astronomers using the Hubble Space
Telescope have found the brightest quasar in the early universe; an object
600 trillion times the intensity of the Sun. At least that's what it appeared to
be at first. The reality turns out to be far more interesting. Welcome back to
Launch Pad, I'm Christian Ready, your friendly neighborhood astronomer. At the
233rd meeting of the American Astronomical Society, a team of
astronomers announced the discovery of the most powerful quasar ever found in
the early universe. Suffice to say, this created a lot of news, but I think
something important got lost in the translation. And that's a shame because I
think the reality of this story is actually much more interesting than
what's being reported. Now before we get into the story, let's just talk briefly
about what quasars are in general so that we're all on the same page. All
galaxies have supermassive black holes at their centers, and by "supermassive", we
mean anywhere from several million to billions of times the mass of our Sun, so
they're called "supermassive" for a good reason.
As matter from the surrounding galaxies falls in order toward the black hole, it
forms a superheated whirlpool of plasma called an accretion disk. The accretion
disk is no larger than the solar system, yet it outshines the entire surrounding
galaxy. They release so much energy into the surrounding galaxy, that they
can generate thousands of new stars every year. By comparison, our Milky Way
creates less than one star a year. Because quasars are so bright, they can
be seen from across the universe. But because light moves at a finite speed, we
see the quasars as they appeared billions of years ago. But the universe
is expanding, carrying the distant galaxies and quasars away from us. This
means that the farther away a galaxy or quasar is from Earth, the more its light
is stretched out to longer or redder wavelengths. This stretching of the light
to red wavelengths is called "redshift", and
astronomers can measure a quasar's redshift to quickly get an idea of how
far away it is, and therefore how far back into the past
they are looking. The quasars in the early universe were fairly bright but
they actually got a little bit brighter as time went on. So by the time the
universe was, say, a few billion years old, the quasars were enjoying a kind of a
cosmic heyday. So imagine the surprise a team of astronomers had when they
discovered an ultra bright quasar at a redshift when the universe was less than
a billion years old! Now I'm going to talk about this discovery in just a
moment, but first I want to thank my Patreon supporters for their generous
support: Patti Broussard, Neil from Crypto Cruising, Eric the modern day family man,
and I'm delighted to welcome my three new supporters John Cannon, Erynn Wilson,
and Gorothbalion. Thank you so much for your generous support! A team led by
Xiauhui Fan at the University of Arizona noticed a high-redshift quasar
in the Sloan Digital Sky Survey the quasars called J043947.08+163415.7...
rolls right off the
tongue doesn't it? Let's just call it J0439 for short.
Anyway, this quasar was discovered at a redshift of 6.5, which places it a little
less than a billion years after the Big Bang, so this is a very high redshift
early universe quasar. Quasars of this epoch in the early universe had
luminosities of tens of trillions of times our Sun. That's still very bright
but J0439 clocked in at something like 600 trillion times the Sun! That would
make J0439 the brightest quasar in the early universe! But was it really as
bright as it seemed? Fan's team wondered if there was in
fact a kind of natural magnifying effect at work here - specifically, they suspected
a gravitational lens. A gravitational lens is a prediction of Einstein's
theory of general relativity, which states that a
sufficiently massive object, such as a galaxy that's placed between us and a
background object, will bend the light from the background object around it,
boosting the brightness and intensity of the background object, and allowing us to
inspect the background object in greater detail than would otherwise be possible.
Quasars have been studied through gravitational lenses before, but they
always happen to be at relatively lower redshift, which puts them a few billion
years after the Big Bang. J0439 however was at a much higher redshift, which
would put it less than a billion years after the Big Bang!
So they examined the object through several large ground-based telescopes.
They were able to determine that the object was a little bit extended on the
sky, which suggested maybe there was a gravitational lens at play here, but it
wasn't until they used the Hubble Space Telescope that they finally
distinguished a foreground galaxy that was lensing the quasar into three
separate images. The foreground galaxy's gravitational lens boosted the
background quasar's brightness from 11 trillion to an apparent 600 trillion
times the luminosity of our Sun! That's a factor of 50 increase in brightness! That
makes J0439 the highest redshifted quasar, and therefore the earliest quasar
ever viewed through a strong gravitational lens.
This means astronomers now have a powerful new window into this quasar's
early past and can probe the quasar and its surrounding environment in
unprecedented detail. And the other cool thing is that this is a completely
serendipitous discovery. They weren't expecting to find such highly redshifted
quasars that would be strongly gravitationally lensed. If they stumbled
upon the J0439 gravitational lens, perhaps there are other early universe
quasars that are also being strongly gravitationally lensed?
So no, it's not that this quasar is 600 trillion times brighter than our Sun in
real life. Rather, it's merely 11 trillion times brighter than the Sun. But the fact
that we're seeing this through a gravitational lens at such a high
redshift is new territory for us, and now we have
a new window into the early universe. Now if you like to learn a little bit more
about quasars, I'll have some videos posted to them here and in the
description below. And if you would like to join me on this journey through this
amazing universe of ours, please make sure to subscribe and ring that
notification bell so that you don't miss out on any new videos. Until next time,
stay curious, my friends.