Results beyond what could possibly have been dreamed up are back from the James Webb Space Telescope (JWST). Y’all submitted a stack of great questions. Since this is one of those ‘our understanding of the universe is changing’ deals, let’s take our time and explore our newfound backyard.
Today’s Moment of Science…. The view from the edge of the universe, part 1.
“I know the pictures are sparkly and shit, but why is every scientist I know with a passing interest in astronomy freaking out about this?” A few reasons, the first one being that it actually goddamn worked. A project fifteen years late and $9.5b over the initial $500m budget, there were 344 potential single-point failures that could have fucked the whole thing to kingdom come after launch. The month-long voyage from Earth to its celestial home was often referred to— only somewhat in jest– as ‘30 days of terror.’ The new pictures from old twinkling bits of universe are both a reward for the hard work of countless scientists… and perhaps a huge sigh of ‘thank christ fucking Craig didn’t flick a booger on the lens back at NASA’ relief.
“Where the fuck do you crash a telescope if you want to look further back in time than ever before?” JWST technically orbits the sun. It hangs out a bit shy of a million miles past the Earth in orbit around Lagrange point 2, or just L2. Named for one of two scientists who discovered these five fixed points of equilibrium and relative stability under the gravitational influence of two much larger celestial bowling balls, it’s a delightful bit of astrophysics courtesy of the 1700s.
“Why a million miles from Earth and not close enough to fix a loose lug nut?” Part of the deal with getting good images from this one is keeping it cooler than being cool, and that’s less than seven degrees Kelvin above absolute goddamn zero. Or as my Canadian relatives would call it, “a light winter.” The cold helps suppress any interference from infrared background noise. The low temperature is maintained both actively with a cryocooler, and passively through parking the telescope and its sun shield the size of a tennis court a million miles further away from the sun than us.
“This can’t possibly work on the same principles as the telescope I had as a kid, right?” Optical telescopes all accomplish pretty similar goals through wildly varying designs. TL;DR- using some strategically placed curved mirrors, lenses, or a combination of both, the instrument gathers more light than the human eye could do naturally to create a magnified image. Drastic oversimplification, but the bigger the mirror and/or lenses you have to bounce light around with, the more tardigrades on Tatooine you can spot.
“What’s up with the giant golden honeycomb?” These mammoth hexagonal beryllium mirrors have an extremely thin coat of gold on them. Like, thousandths of an inch thick.The hexagons fit into a compacted structure for transport, then unfold in space with the mirrors fitting together snugly. Beryllium was used because it’s light, strong, and unlikely to become warped in the fuckery of space travel. The gold plating improves the reflectivity of infrared light to focus every last photon into the instruments.
“‘Splain the giant shiny silver cake, science lady.” The five layer sunshield, about 21m x 14m, is made of a thermally stable polymer called Kapton that’s coated in aluminum and silicon. The shield is positioned between the main instruments and local sources of interference, namely the Earth and sun. The golden mirror is facing out to the universe with as much light and heat interference blocked as possible. Neat fucking cake.
“How in sweet deep fried Jesus’ ass is this ‘optical’ if what we’re seeing is invisible to the naked eye?” Optical telescopes all detect light from the visible part of the electromagnetic spectrum, but they’re not limited to that range. For instance, Hubble detects visible, near-infrared (IR), and ultraviolet (UV) light. JWST can detect some visible light (orange and red), along with near and mid-IR.
“What’s the difference between JWST and Hubble?” About $8.5 billion and Al Gore isn’t trying to shut JWST down (true story the early 90s were fucking bananas). They’re reasonably being compared because both are uniquely advanced compared to every other telescope floating in our part of the galaxy. They’re unreasonably being compared to talk shit about Hubble. In 1996, the Hubble Deep Field image was released. A composite from aiming the telescope at what they thought was a blank speck of sky over the course of ten days, it was a peek thirteen billion years back in time to see over 3,000 galaxies.
It’s easy to look back now and say “of course it wasn’t a waste of ten days with a zillion dollar piece of circuitry and optics,” but aiming at nothing and finding creation wasn’t a given. It was a paradigm shift.
While both telescopes interpret signals from IR light, JWST’s primary mirror is over six times the area of Hubble’s. JWST can get its deep field image in a comparably short 12.5 hours. The wavelengths of light it can detect from four advanced spectrographic instruments give us a view almost to the backdrop of existence. Which is “only” another half a billion years back in time, but damn if it’s not a super important half a billion years.
Let’s save how light lets us see back in time for tomorrow.
This has been today’s Moment of Science, asking if anyone has directions to the restaurant at the end of the universe.
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Let’s get into the finer details of how a telescope is kindasortareally a time machine.
Today’s Moment of Science… The view from the edge of the universe, part 2.
Light is the convenient and visible bit of the electromagnetic spectrum. When you hop slightly outside of that range, a good guideline is that the shorter the wavelength, the bigger the deathray. Just below the last perceptible bit of violet, at around 400nm, you find those charming ultraviolet rays. Shorter than 10nm we get to the highly energetic ionizing douchelords, X and gamma. On the other end, red has the longest visible wavelength at about 740nm, after which comes infrared, microwaves, then utterly lethargic radio waves, which can stretch over 100km long.
So, neat fucking trick that quantum mechanics pulled; each element has a unique emission spectrum. One atom will show you just one spectral line, but with a typical sampling of an element, an appropriate spectrometer will show you the full emission spectrum. Once they’d been sorted for each element, astronomers could look at the stellar spectra of distant stars and figure out their composition. Through their spectra, they could easily be recognized and grouped as red giants, white dwarfs, and other problematic Disney characters.
But light has a self-imposed speed limit and exists in this expanding universe. Even traveling at the speed of itself, that constant expansion for fourteen billion years pushed the borders of space so far apart that the most distant galaxies haven’t a prayer of being visible from here.
This is where the less convenient types of light are conjured to shine.
The Doppler effect was proposed in the 1840s by German scientist Christian Doppler to explain the apparent color of stars. The basic idea that we now refer to as ‘redshift’ was in there. There are several ways the term is used and calculated in physics; we’re dealing with cosmological redshift here, but let’s not get bogged down with the numbers. When an electromagnetic wavelength gets longer and less energetic, it’s considered redshifted.
Looking at the concept with soundwaves offers something we tangibly understand more easily because we’ve felt this happening in real time. When a car passes an observer while blaring my favorite song and yours, Wannabe by the Spice Girls, it’s understood that the fab five are not turning into baritones as the vehicle moves away from the observer. The same tune is playing, but the source continually moving away means it takes more and more time for each successive wavefront to hit you. The hum of Mel B saying ‘slam your body down and zigazag ah’ might still reach your ears, but because of the time it takes for sound to travel, you’ll hear it from the past, a stretched version of the wavelength.
Light does the exact same shit, but instead of making a super creepy remix when those wavelengths get longer, they eventually crash into the infrared part of the electromagnetic spectrum. Based on a bunch of fancy pants math, the degree to which an emission spectra will redshift is a knowable, predictable thing. With methods to detect infrared light, we’re just a bunch of conversion factors away from a visual time machine.
Now that you know all that.
JWST’s task isn’t merely acting as a long exposure camera to get snaps of some reddish galaxies. After upwards of thirteen billion years of space travel, that giant honeycomb mirror collects every weary infrared photon it can grab. With several spectrometers on board for different wavelength ranges, the complex spectral data from those old tired photons are analyzed and converted into stunning images.
This morning, we already got news that we have a new contender for the oldest galaxy that’s been identified. Named GLASS-z13, it’s believed to have formed a mere 300 million years after the big bang. Earth wasn’t even the planetary equivalent of a sperm yet, you pay your elders some goddamn respect. The previous oldest identified galaxy, GN-z11, is about a hundred million years younger.
At the end of these galaxy names are their redshift values. It’s dimensionless quantity, with a variable typically set to ‘z.’ But what the fuck does that even mean when it’s a value that has no units? Since this is the cosmological redshift, it’s all about the expansion of space and the size the universe was when the photon flew off that ancient cluster of stars. To show you the pattern, a hypothetical galaxy with a redshift of 2 means the universe was ⅓ the size the light left it. GN-z11’s redshift of 11 means we saw light that started traveling when the universe was 1/12th the size it is now.
The light from GLASS-z13, with a redshift of 13, started its journey to our little miracle of circuits and optics well over 13 billion years ago, when existence was 1/14th what it is now. Which is exactly why a telescope is a time machine.
This has been your Moment of Science, just letting you know that my autocorrect changed ‘wannabe’ to ‘wallaby.’
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