The Hubble telescope launched in 1990 after years of delay—and was repaired in an amazing feat of space engineering in 1993 to correct a flaw in its mirror that was causing blurry images. Then, in 2022, the James Webb telescope opened flawlessly in space and sent back breathtaking images of galaxies, stars, and space dust in never-before-seen detail. But what’s the difference between the Webb and Hubble telescopes? Are Hubble images still useful? And what new discoveries might be made with the Webb telescope?
Complementary, Not Competitive
The Hubble Space Telescope excels at observing ultraviolet and visible light ranging from 0.1 to 2.5 microns in wavelength. The Webb telescope can see much deeper into infrared light of longer wavelengths, from 0.6 to 28.5 microns.
Because the two telescopes are designed to look for different wavelengths of light, they “see” different aspects of the universe in both visible and invisible (to the human eye) light. While Webb is far more powerful, Hubble’s observations are still useful and can provide insight into the new understanding gained from Webb’s more detailed images.
The Difference Distance Makes
The Hubble telescope’s designers anticipated that maintenance and modifications might be necessary over time. Because Hubble orbits the earth just beyond its atmosphere, repair and modification missions completed by astronauts visiting from the space shuttle were possible. The Hubble is also significantly smaller than the Webb because it was made to fit within the space shuttle’s cargo bay to deliver it to its orbit and one day retrieve it from space.
The Webb telescope traveled to a point in our solar system called “L2,” which is four times farther away from earth than Hubble—a million miles beyond our planet. At that distance, with its sophisticated shielding, the Webb telescope can stay extremely cold. This allows its sensors to capture the faint heat of extremely distant stars and galaxies. Webb’s sensors can also collect infrared radiation without interference from interstellar gas and dust, allowing it to “see” exoplanetary atmospheres, perhaps even detecting conditions conducive to supporting life.
Light Is a Time Traveler
Both telescopes can “see” objects in the universe that are unimaginably ancient. The light the telescopes gather has traveled vast distances from its point of origin to the telescopes’ mirrors. Einstein taught us the speed of light, 186,000 miles per second. A light year is the distance light can travel at that fixed speed in an earth year’s time. So, when either telescope captures an image from a far distant object, it’s actually showing what the object looked like thousands, or even hundreds of millions, of years ago.
A significant difference between the Webb and Hubble telescopes is Webb’s ability to capture much longer wavelengths in the infrared spectrum. This allows it to look further back in time than the Hubble. Scientists who regularly use optical equipment in their research were flabbergasted at the stunning detail of the images Webb’s observations created. And they were even more excited about the possibility of “seeing” back in time to just 200 million years after the “Big Bang,” regarded as the moment the universe began.
While we could repair or even conceivably retrieve the Hubble telescope, the Webb telescope is beyond our reach, a million miles away. Its flawless deployment will go down in history as one of the most astonishing accomplishments of human engineering, and it will continue to provide new observations for an estimated 5 years and a hoped-for 10.
While the Webb relies on the gravitational pull of our sun to keep it at its chosen location, L2, in our solar system, it also uses fuel to make small adjustments to maintain its precise location. That fuel will eventually run out. At that point, scientists and space buffs alike can hope that an even more spectacular space telescope will be ready.