It’s a big universe out there. But with astronomers producing remarkable cosmic discoveries and insights every day, you might think we have everything covered, with the collective power of Earth-based telescopes giving us complete situational awareness of the sky.
Nothing could be further from the truth. Despite the existence of all our advanced observatories, there are still parts of the electromagnetic spectrum (and beyond) that we study. not see and places where we need more (or all) telescopes.
By definition, the spectrum, that is, the different types of light, has an essentially infinite range. But despite everything, the visible The spectrum span from violet to red is only a factor of two in wavelength, while the vast range from longwave radios to gamma rays covers more than 20 orders of magnitude. So it should come as no surprise that we haven’t covered everything.
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What is more surprising, in fact, is the extent to which we to have managed to cover! Thousands of visible light telescopes are in operation at any time; I have a personal one that I use myself when the bugs outside aren’t too bad. Professionally Speaking of which, there are dozens of large observatories on the ground and in orbit above, and many next-generation facilities are in the works, including the soon-to-be-launched one. Nancy Grace Roman Space Telescopewhich will have the sharp vision of the Hubble Space Telescope coupled with a much wider field of vision. And it’s also important to note archival data, because most things in the sky don’t change significantly on the human time scale, making in-depth investigations still relevant even if they take place over years or decades.
For example, in infrared, we had the wide field infrared survey explorerwho scanned the entire sky to provide insight, and, of course, we still have the James Webb Space Telescope giving us the sharpest, deepest views ever seen in this spectral range. The Wilkinson microwave anisotropy probe (WMAP) and the Planck an observatory mapped the sky using microwaves; today, the large millimeter/submillimeter network of Atacama (ALMA) covers smaller wavelengths. And overall, there are almost as many operational radio telescopes as there are visible light radio telescopes.
On the other end of the spectrum, the Galaxy Evolution Explorer (GALEX) studied the sky in ultraviolet, and Hubble still has two UV cameras in operation. Several orbiting telescopes detect X-rays, including the venerable Chandra X-ray Observatory, XMM-Newton, Neil Gehrels Swift Observatoryand more. Even gamma rays are having their day in the sun (so to speak), with the Fermi Gamma-Ray and Swift Space Telescope still operational and producing amazing data.
There are some gaps in our coverage, but even those have suggestions to fill them. One of the most glaring discrepancies is between infrared and millimeter wavelength radio observations, but the Far infrared probe mission for astrophysics (PRIMA) would fill a large part of it. Another gap exists for radio waves with a wavelength of 10 meters or more, which are reflected from the Earth’s ionosphere; to observe them, astronomers proposed build radio telescopes on the far side of the Moon. One, called the Lunar Crater Radio Telescopewould be a staggering kilometer. Such telescopes would be sensitive to radio waves emitted by the gas the cosmic “Dark Ages” the period a few hundred million years after the big bang but before the birth of the first stars, a time about which we know very little.
And even for the parts of the spectrum that are already largely covered, it’s not necessarily greedy to want more! Different telescopes have different functions. Some observe large areas of the sky to take surveys, while others identify specific targets; some take images, while others take spectra, dividing incoming light into different energies (or colors, wavelengths, or frequencies, which are all different terms for essentially the same thing). Such spectroscopy is a powerful technique for the in-depth study of celestial objects, capable of revealing their rotation, motion, composition, distance and much more. I think it stands to reason that the more telescopes we have, the better we can understand the universe.
But focusing on gaps in our spectrum coverage can lead us to ignore other viable areas of observation.
On the one hand, we have a penchant for the study of light. But other cosmic messengers exist.
For example, accelerated masses create gravitational wavesliteral ripples in the fabric of space-time. For the vast majority of objects in the universe, these waves are too soft to be detected, but very massive objects accelerating very quickly emit much more defined waves. Black holesin particular, lend themselves to this approach, especially since they do not directly emit any light.
The Laser Interferometer Gravitational Wave Observatory (or LIGO) detected the first waves of this type in 2015recording the otherwise invisible merger of two stellar-mass black holes. It was an extraordinary achievement; Albert Einstein predicted the existence of gravitational waves, but it took technology a century to catch up with his calculations. Since then, several other similar observatories have come online to observe hundreds more events, but all this activity represents a narrow range of gravitational waves, those created when relatively small neutron stars or black holes collide.
The European Space Agency Space antenna for laser interferometer (LISA), scheduled to launch in 2035, will detect the much longer gravitational waves created when gigantic supermassive black holes spiral and collide. Such collisions are believed to be the most energetic events in the known universebut we still know very little about them. Made up of three separate spacecraft separated by 2.5 million kilometers, LISA is too big and too sensitive for our small, noisy planet. Which is why, of course, it has to be sent into space.
Dark matter is another problem. We know it exists and is responsible for forming much of the structure of the universe, but it emits no light and apparently does not interact with normal matter at all except through gravity. We can detect it indirectly in the distant universe using gravitational lensing. and other methods, but we still have no way to detect it directly here on Earth, even though dark matter particles are probably circulating through you and everything else on the planet as you read this! In fact, we still don’t know if dark matter is a particle. None of the many experiments that have attempted to detect such particles have found them unequivocally. And more broadly, all this is part of a rich and booming field in which our “telescopes” are detectors studying neutrinos, fragments of atomic nuclei and other non-electromagnetic celestial emissaries.
But there’s still so much more we can’t see, and it might surprise you: we have vast gaps in our knowledge of our own solar system! The region beyond Neptune is populated by billions of rocky and icy bodies called trans-Neptunian objects (or TNOs) left over from the formation of the solar system. Only a few thousand are knownHowever. They are incredibly weak and difficult to find. THE Vera C. Rubin Observatory is expected to discover tens of thousands of them, which will hopefully allow astronomers to better classify them and better understand what the solar system was like in its infancy. And Rubin will also discover much more than just TNOs, thanks to his focus on time-domain astronomy, the study of objects such as asteroids, novae, supernovae, and active galaxies that move and vary in brightness. Although Rubin only takes visible light images, the ability to show us the change it is in these images that its true power lies.
Our more “local” limits are not limited to the outer solar system either; we also don’t know much about the region near the sun. THE Parker solar probe has bombarded the sun several times since its launch in 2018 to measure for the first time the solar environment very close to the surface of our star. Somewhere in this barely explored neighborhood south of Mercury, there could be a population of small asteroids from 100 meters to six kilometers in diameter; called volcanoidsthey would be too close to the powerful glare of the sun for us to easily see them from Earth. If their existence were one day confirmed, they would tell us a lot about the evolution of the solar system.
We also cannot currently search potentially dangerous asteroids coming from inside Earth’s orbit for the same reason, but NASA’s Near-Earth Object Investigatorscheduled to launch in 2027, will park in a gravitationally stable position about a million miles closer to the sun than Earth to search for asteroids as close as 45 degrees in the sky to our star. The plan is to catalog two-thirds of the asteroids larger than 140 meters in diameter in this volume of space.
The universe starts right above your head and continues for a while. very a long way. We humans have a pretty decent view of it, which we take advantage of to learn more about our origins and our cosmic environment. And while there are certainly gaps in our view, we have a pretty good idea of where they are and we should do our best to fill them.
