By Nancy Rynes, author of Awakenings from the Light
Article copyright Nancy Rynes, 2022
Have you ever looked up at the stars in the night sky and wondered if there was someone on the other side of the galaxy, on a planet similar to ours, looking back at you?
That's exactly how I spent many summer evenings when I was a child. My family lived in the middle of Illinois farm country where the sky was relatively dark, so seeing the bright splash of the stars of the Milky Way (our own galaxy) across the black background of night was a common sight. Even at my youngest, I would look up at all of those stars and wonder who else was out there looking back at me.
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| The Milky Way, our own galaxy |
In high school and college, I managed to save enough money to buy an 8-inch telescope. It was a beginner model and wasn't built for photography, but it opened up the universe to me even more. Now I could easily see the rings and moons of Saturn, the wisps of dust and gas from far-off places where stars were born such as the Pleiades, and even the fuzzy outlines of very distant galaxies. Galaxies much like our own, with perhaps 100 billion stars each, expanded the chances that maybe, just maybe, there was someone else out there gazing at our galaxy and wondering if there was anyone here looking back at them.
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| The Pleiades Star Cluster |
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| The Andromeda Galaxy with satellite galaxies M32 and M110 |
But college is where I left my active interest in astronomy behind. My studies in geology and archaeology left me little time to go out and look at the night sky with my own telescope. Instead I got my astronomy fix by viewing the images sent back from the Hubble Space Telescope. The Hubble started off its career with some optical challenges, but once those were fixed by the astronauts of the Space Shuttle, the images brought all of us breathtaking views of things in space that we had only dreamed of seeing before then (see below). And after Hubble came the Kepler Space Telescope and TESS (Transiting Exoplanet Survey Satellite), both designed to look for planets around other stars in our galaxy (exoplanets) in fixed regions of the sky. And then there was the Spitzer Space Telescope, a pioneer of imaging in the infrared bands of the spectrum. All of these telescopes gave us more than we ever counted on seeing, especially Kepler and TESS, who have shown us the truly astounding numbers of planets that exist outside of our own solar system (we now believe that there is an average of one planet per star in the galaxy, but I suspect this number is actually quite low).
Even with all of these amazing exoplanet discoveries, though, we still don't have definitive telescopic proof of the existence of civilizations outside of our own.
But now we have another new space telescope that's considered to be a successor to Hubble, Kepler, TESS, and Spitzer. The James Webb Space Telescope (JWST) has an ambitious mission:
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| Image from the Hubble Space Telescope showing a deep-space view of a cluster of galaxies. Each of those smudges you see is a separate galaxy, each with 100 billion or more stars. |
But now we have another new space telescope that's considered to be a successor to Hubble, Kepler, TESS, and Spitzer. The James Webb Space Telescope (JWST) has an ambitious mission:
- Early Universe and Galactic Evolution: The JWST will look for the most distant galaxies using the infrared bands (IR) of the light spectrum spectrum. With its increased light-gathering capacity and its ability to detect information in the IR bands, we should get more information about the early universe and its evolution.
- Our Solar System: With its powerful infrared imaging capability, the JWST will be an invaluable tool in finding out more information about our own solar system, such as the "ocean worlds" of Jupiter's moon Europa and Saturn's moon Enceladus.
- Star Lifecycle: Webb will be able to give us more information about the births, maturation, and populations of stars, as well as their relationships to each other and their planets.
- Exoplanets: And finally, and for many of us the most exciting part, is JWST's ability to give us more information about the atmospheres of planets outside of our own solar system. Can we find the signature of life on exoplanets closest to us in the Milky Way? Can we see evidence of aliens' impact on their planets, such as atmospheric pollution? There is the real possibility with JWST of finding the first evidence for life outside of our own planet.
And as with Hubble and our other space telescopes, we may end up with even more amazing discoveries than these. But the JWST is not the Holy Grail of astronomy. While it's definitely a huge step forward in space-based research, it has its limits.
Signs of Life
Recently I was listening to a radio host wax poetic on the vast capabilities of the JWST, that with it "we could peer anywhere and see anything we wanted in the universe." If there was an alien city on a distant planet on the other side of the Milky Way, we'd be able to see it and all of its sister-cities too.
If only that were true!
Think about it this way: a planet is tiny and dark as compared to its host star, and we are a huge distance away from even the nearest exoplanet. That closest exoplanet is over 21 trillion miles (40 trillion kilometers) away. While Webb should be able to detect the chemical signatures of the atmospheric components of the closest exoplanets, which itself is an incredible feat, we are not going to be able to see alien beings zooming around their planet's surface in space-cars.
While I loved his enthusiasm, our radio show host held out a little too much hope for this generation of telescope. JWST cannot see everywhere in great detail, or tell us everything about the universe. It is not powerful enough to see individual cities on the surface of exoplanets for example, and it just was not designed to look at the atmospheres of exoplanets that are far away from us.
But it can help us search for nearby habitable planets, and for planets that have certain components in their atmospheres that tell us life might already exist there. It does this through its ability to deduce specific components of an exoplanet's atmosphere when that planet passes in front of its host star. This is called transit spectroscopy.
How Transit Spectroscopy Works
Basically, the light emitted from a star has a certain characteristic spectral (light) signature based on the chemical composition and age of the star. In other words, it doesn't emit light evenly across the entire electromagnetic spectrum; rather, it emits only certain wavelengths or bands of light based on the chemical composition of the star. It's essentially seeing the star's unique fingerprint. Once we know the star's own spectral signature or fingerprint, we wait until one of the star's planets passes in front of it.
When a planet passes in front of its star, light from the star illuminates the planet's atmosphere, assuming it has one (if it doesn't, we can detect that too). The gases and particles in the planet's atmosphere absorb and transmit light from the star in different ways depending on those individual atmospheric components. Our telescope can then collect that light coming through the planet's atmosphere and analyze it. By comparing the light as it comes directly from the host star with the light as it is filtered through the planet's atmosphere, we can deduce the composition of the planet's atmosphere.
Scientists seeking signs of life as we know it on the nearest exoplanets will be looking for a variety of things in those atmospheres, such as water vapor, oxygen and ozone, methane, phosphene, nitrogen, nitrous oxide, carbon dioxide, and more. Signs of atmospheric pollution could indicate the presence of a civilization, although no one is really counting on seeing this. But this approach really only applies to those exoplanets that are relatively close to our solar system...even though it is a huge leap forward in telescope design, the JWST just cannot get much detail on the more distant exoplanets.
Instead, this telescope is designed to gather information on the early days of the universe, and whether the conditions for life as we know it are relatively rare or common across our own solar system. It will be able to get us more information on black holes, as well as the births and deaths of stars. And yes, there is a chance that we will detect the first signatures of life in the atmosphere of a planet outside of our own solar system.
While I think it would be pretty cool to see an E.T. flying around its planet's atmosphere in a space-car, how would you feel about it? Would your view of life change in any way if scientists found definitive proof that life existed on planets outside of our solar system?
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