The very first telescope, created in 1608 by Dutch optician Hans Lippershey, set the stage for groundbreaking technologies that transformed our comprehension of the universe. His initial design utilized basic lenses to magnify objects up to three times their size, which later scientists expanded upon to explore the vastness of space.
However, not all telescopes are created equal. Some are significantly more powerful than others, granting astronomers the ability to observe distant stars and galaxies, as well as extreme phenomena like black holes and Einstein rings. So, which telescope holds the title for the most powerful, and just how far can it see into the cosmos?
The answer, likely not so surprising to those keeping up with recent news, is the James Webb Space Telescope (JWST). Launched in December 2021, it is designed to detect infrared and near-infrared wavelengths, which are part of the electromagnetic spectrum that humans can’t directly see but can experience as heat. Its predecessor, the Hubble Space Telescope, focused mainly on visible spectrum and ultraviolet light, the latter often emitted by young stars.
In space, many celestial objects don’t produce or reflect enough visible spectrum light to be perceived by the human eye or detected from afar. On the other hand, infrared light, being longer in wavelength, can be identified over vast distances. This property also allows infrared light to penetrate through clouds of dust, making it particularly advantageous for astronomers who wish to delve into the universe’s deeper mysteries.
Interestingly, even the newly launched Vera C. Rubin Telescope in Chile struggles to reach these distant realms due to obstructions such as dust particles.
At the universe’s inception, everything was compacted into a hot, swirling mass of particles. As it expanded and cooled, the first stars and galaxies began to form. The earliest of these visible stars date roughly to about 13.7 billion years ago, occurring just a little over a hundred million years post-Big Bang.
“The James Webb Space Telescope has managed to see 98% of the way back to the Big Bang,” stated Peter Jakobsen, an astrophysics professor at the University of Copenhagen, via an email to Live Science. “It has surpassed what many of us anticipated during the planning stages for the JWST.”
How does the JWST see so far?
The JWST’s power largely stems from its expansive primary mirror, as noted by astrophysicist Carol Christian at the Space Telescope Science Institute.
This primary mirror has a diameter of 21.3 feet (6.5 meters), granting it a collecting area of over 270 square feet (25 square meters). In contrast, Hubble’s mirror is only 8 feet (2.4 meters) across, with a collecting area of nearly 50 square feet (4.5 square meters). Nevertheless, both telescopes can observe celestial objects located billions of light-years away, as they operate beyond Earth’s atmospheric limitations.
Complementing its design, the JWST is additionally outfitted with infrared light detectors that help absorb the redirected light from its large mirrors. This enables the JWST to identify distant light that the Hubble cannot detect.
Earth’s atmosphere presents unique challenges for telescopes located on the surface, including light pollution and “atmospheric turbulence,” which can blur images and restrict how deeply one can observe the cosmos. In contrast, space remains free of these complications, which is why many of our most powerful telescopes are situated beyond the atmosphere.
The JWST is positioned nearly one million miles (1.5 million kilometers) from Earth at a gravitationally stable Lagrange point.
How far can the James Webb Space Telescope see?
When gazing at the night sky, we’re effectively looking back in time. Since light travels at about 299,792,458 meters per second (or 186,282 miles per second), the light reaching us from distant objects is, well, older than when it was first emitted. For example, it takes light from the sun about 43.2 minutes to reach Jupiter, but only 8 minutes to make it to Earth. When we talk about the farthest reaches of the universe, though, it gets much more complicated. So, measuring how far a telescope can see isn’t straightforward, according to Jakobsen.
A couple of challenges include the universe’s expansion and the fixed speed of light. To navigate these complexities, astronomers often measure the redshift of distant celestial bodies.
Redshift refers to how we perceive celestial objects moving ever further away from us. As the universe continues to expand, the light emitted from those objects is stretched to longer and “redder” wavelengths. Thus, the farther the light travels, the more notable its redshift becomes.
Currently, one of the most distant known contenders is the galaxy JADES-GS-z14-0, which dates to approximately 290 million years after the Big Bang.
There’s another contender, still awaiting peer-reviewed publication, called MoM-z14, dated to just 280 million years post-Big Bang. Its redshift is 14.44, surpassing the redshift of JADES-GS-z14-0, which sits at 14.18.
One study explored a selection of particularly large and distant galaxies spotted by the JWST, suggesting that they might be older than current universe models anticipate.
The JWST has successfully demonstrated that it can explore deeper into space than Hubble, which has only been able to view back 13.4 billion years.
While the JWST currently reigns supreme in investigating our cosmic history, competition is brewing. China is developing a new space telescope—dubbed the China Space Station Telescope—that will employ technology capable of capturing a wider range of light frequencies than the JWST, potentially gleaning even more information from the cosmos.
