We’ve come fantastically far in our understanding of the distant Universe. Here’s how we’ll go even farther.
Sometime in 2021, NASA’s James Webb Space Telescope will launch, deploy, and begin science operations.
The James Webb Space Telescope vs. Hubble in size (main) and vs. an array of other telescopes (inset) in terms of wavelength and sensitivity. It should be able to see the truly first galaxies, the earliest, most pristine stars, the smallest directly imaged planets and more. Its power is truly unprecedented. (NASA / JWST SCIENCE TEAM)
With seven times Hubble’s light-gathering power, better resolution, and extended infrared capabilities, numerous cosmic records will fall.
As we’re exploring more and more of the Universe, we’re able to look farther away in space, which equates to farther back in time. The James Webb Space Telescope will take us to depths, directly, that our present-day observing facilities cannot match, with Webb’s infrared eyes revealing the ultra-distant starlight that Hubble cannot hope to see. (NASA / JWST AND HST TEAMS)
Although it will almost certainly make unforeseen discoveries, Webb is poised to shatter four separate cosmic records.
The most distant galaxy ever discovered in the known Universe, GN-z11, has its light come to us from 13.4 billion years ago: when the Universe was only 3% its current age: 407 million years old. The distance from this galaxy to us, taking the expanding Universe into account, is an incredible 32.1 billion light-years, and is only possible because of a serendipitous lack of light-blocking dust along the line-of-sight to this galaxy. (NASA, ESA, AND G. BACON (STSCI)) 1.) Most distant galaxy. Presently, the Hubble Space Telescope holds the record, discovering GN-z11 from just 407 million years after the Big Bang. This artist’s impression of an early, massive galaxy that forms from the merger of smaller-protogalaxies shows how it should be obscured by dust during the most rapid phases of star-formation. James Webb’s infrared eyes might allow it to penetrate this dust, revealing details of the earliest stars ever seen. (JAMES JOSEPHIDES/CHRISTINA WILLIAMS/IVO LABBE)
Webb’s infrared eyes will see through the cosmic dust that obscures Hubble’s vision, revealing galaxies
as little as 200–275 million years old. When a planet transits in front of its parent star, some of the light is not only blocked, but if an atmosphere is present, filters through it, creating absorption or emission lines that a sophisticated-enough observatory could detect. If there are organic molecules or large amounts of molecular oxygen, we might be able to find that, too. at some point in the future. The best current limits have revealed only Saturn-sized atmospheres around Sun-like stars and Neptune-sized atmospheres around red dwarfs. (ESA / DAVID SING) 2.) The smallest exoplanets’ atmospheres. With enough light, advanced telescopes can measure exoplanet atmospheres via transit spectroscopy. The atmosphere of the exoplanet WASP-33b was examined as starlight filtered through the planet’s atmosphere before arriving at our eyes. Similar techniques could work for other exoplanets as well, but to image the atmosphere of Earth-sized planets, as opposed to the Jupiter-sized WASP-33b, we require observatories that are larger and more advanced than the ones we have today. NASA’s James Webb Space Telescope will break all the transit spectroscopy size records we currently have today. (NASA / GODDARD)
Hubble can measure Saturn-like worlds around Sun-like stars, but
Webb will get mini-Neptunes around Sun-like stars, plus Earth-sized worlds around red dwarfs. An illustration of the galaxy CR7, which was originally hoped would house multiple populations of stars of various ages (as illustrated). While we have yet to find an object where the brightest component was pristine, with no heavy elements, we fully expect them to exist, often alongside a later generation of stars that formed earlier. James Webb should reveal the most pristine stellar populations of all, easily breaking the current record. (M. KORNMESSER / ESO) 3.) The earliest stars. The very first stars should consist of hydrogen and helium alone, untouched since the Big Bang. The first stars in the Universe will be surrounded by neutral atoms of (mostly) hydrogen gas, which absorbs the starlight. The hydrogen makes the Universe opaque to visible, ultraviolet, and a large fraction of near-infrared light, but longer wavelengths may yet be observable and visible to near-future observatories. (NICOLE RAGER FULLER / NATIONAL SCIENCE FOUNDATION)
With capabilities to see faint, distant objects at infrared wavelengths,
Webb should discover truly pristine stars. There are four known exoplanets orbiting the star HR 8799, all of which are more massive than the planet Jupiter. These planets were all detected by direct imaging taken over a period of seven years, with the periods of these worlds ranging from decades to centuries: much larger and more distant than Proxima c. (JASON WANG / CHRISTIAN MAROIS) 4.) Imaging the smallest planets. Direct imaging requires bright planets well-separated from their parent star. The exoplanet Proxima b, as shown in this artist’s illustration, is thought to be inhospitable to life due to the atmosphere-stripping behavior of its star. It should be an ‘eyeball’ world, where one side always roasts in the Sun and the other side always remains frozen. With a telescope like James Webb, direct imaging and spectroscopic measurements, including a search for CO2, should be possible. (ESO/M. KORNMESSER)
With Webb’s tools,
especially its coronagraph, the smallest exoplanets to date will be directly revealed. The Starshade concept could enable direct exoplanet imaging even superior to what Webb will offer, and could be attached to a proposed observatory like WFIRST or LUVOIR to at last reveal Earth-sized planets around Sun-like stars. With its mathematically ideal shape, this could enable imaging and characterizing planets at ~1 AU that are up to 10 billion times fainter than their parent star. (NASA AND NORTHROP GRUMMAN) Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more. Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.