Astronomers will soon use the James Webb Space Telescope (Webb) to look farther into space than even the Hubble Space Telescope has been able to.
They’ve already gathered an incredible amount of data and breathtaking images from NASA’s Hubble Space Telescope. Despite these gains, so much about space is still unknown. One of the fundamental facts that still hasn’t been answered is what the most distant galaxies in the universe are like. The Webb telescope will extend Hubble’s capabilities and help astronomers catch a glimpse of the most distant galaxies in the universe.
Throughout history, philosophers and scientists have grappled with deep questions about humanity’s relationship to space. Back in Aristotle’s day, people thought Earth was the center of everything, and that everything else revolved around it. This misconception was eventually dispelled by Copernicus and Galileo (and many others in between), when Galileo pointed a telescope at the stars and used evidence to prove that the universe doesn’t revolve around Earth.
Centuries later, astronomers debated the size of the Milky Way. The BBC reports that in a 1920 debate between astronomers, estimates ranged from 30,000 to 300,000 light-years in diameter. It turns out that those estimates were either three times too small or three times too big. Today, astronomers measure the Milky Way to be 100,000-150,000 light-years across.
In the 1920s American astronomer Edwin Hubble was the first astronomer to determine that other galaxies existed beyond the Milky Way. Until then, most astronomers thought the fuzzy patches they saw through their telescopes were nebulous gas clouds within the Milky Way. Hubble’s discovery expanded our modern understanding of space.
During this time period, scientists also believed that space was static, according to NBC News. And yet when Albert Einstein developed his theory of relativity, it predicted a universe that must either expand or contract. To fix the disagreement, Einstein hedged his theory with a “cosmological constant” to produce a static universe. Then, astronomers like Vesto Slipher and Edwin Hubble measured the motions of galaxies for the first time and found that most appeared to be speeding away from us. In other words, the universe is expanding.
Measuring the Observable Universe
The universe is larger than we can possibly comprehend, and it is still expanding. Now, a century after Hubble’s discovery, his namesake telescope continues to reveal galaxies that are billions of light-years away. Thanks to the Hubble Space Telescope, we now know that there are 100 to 200 billion galaxies, according to Space.com. When the Webb Telescope launches, it will reveal even more information about the farthest galaxies.
When we talk about the distance of anything in space, we’re also talking about time. Looking at the night sky is like time traveling. The shiny things that we perceive as stars are actually like snapshots of what those stars looked like in the past, according to LiveScience. Stars and other objects in space are so far away that their light can take thousands or even millions of years to reach Earth. The farthest objects are so far away from us that their light still hasn’t reached Earth.
What Is a Light-Year?
A light-year is the distance light travels in one Earth year. According to NASA, one light-year is equal to 6 trillion miles, or 9 trillion kilometers.
Astronomer Dr. Katie Mack explains that everything you look at is in the past. The farther away in space, the longer that light has been traveling. Even if you hold up your hand in front of your face, you’re actually seeing your hand as it was a nanosecond ago, because that’s how long it takes light to travel the distance between your hand and your eyes. It takes approximately eight minutes for light to travel from our sun to us, and several years for light to travel from our next-door neighbor Alpha Centauri. Astronomers can use the world’s most powerful telescopes to see galaxies that are more than 13 billion light-years away.
Scientists know that the universe is approximately 13.8 billion years old, according to LiveScience. So, is it 13.8 billion light-years wide? No; it’s more complicated than that. That pesky expansion that Hubble observed means that while the farthest light traveled to us, outer space continued to expand. When accounting for the expansion, scientists estimate that the edge of the observable universe is now 46.5 billion light-years away.
But what about the galaxies that we can’t see? LiveScience reports that astronomers have used models to estimate that the universe could be at least 250 times the size of the 46.5 billion light-years we can actually see.
Webb Will See Farther
The edge of space — if there is such a thing — will always be beyond our grasp. As Hubble noted, space is expanding. As a result, the farthest galaxies are moving away from us faster than the speed of light, so we can’t “see” them, no matter how awesome modern telescopes may be.
The Webb telescope will peer into our universe’s history by observing the most distant stars and galaxies. The telescope is 100 times more powerful than Hubble. While its predecessor orbits Earth at an altitude of approximately 570 kilometers, Webb will sit deeper in space, 1.5 million kilometers from Earth. From that vantage point, the largest telescope ever launched into space will observe infrared light. It will use a suite of scientific instruments to capture faint objects that could be more than 13 billion light-years away, including young galaxies that were born just a few hundred million years after the Big Bang occurred.
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