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If the James Webb telescope was 10 times more powerful, could we see the beginning of time? – Sam H., age 12, Prosper, Texas
The James Webb Space Telescope, or JWST, is one of the tallest telescopes ever built. Planning for JWST began over 25 years ago, and construction efforts lasted over a decade. It was launched into space on December 25, 2021, and within a month it reached its destination: 930,000 miles from Earth. Its position in space allows a relatively unobstructed view of the universe.
The design of the telescope was a global effort, led by NASA, and intended to push the boundaries of astronomical observation with revolutionary engineering. It is a huge mirror – about 21 feet (6.5 meters) in diameter. That’s almost three times larger than the Hubble Space Telescope, which was launched in 1990 and is still working today.
It is a telescope mirror that allows it to collect light. JWST’s is so big that it can “see” the faintest and most distant galaxies and stars in the world. Its state-of-the-art instruments can reveal information about the composition, temperature and motion of these distant cosmic objects.
As an astrophysicist, I’m constantly looking back in time to see what stars, galaxies and supermassive black holes looked like when their light began its journey towards Earth, and I’m using that information to to better understand their growth and evolution. For me, and for thousands of space scientists, the James Webb Space Telescope is a window into that unknown universe.
How far back can JWST peer into the cosmos and the past? About 13.5 billion years.
Time travel
A telescope does not show stars, galaxies and exoplanets as they are right now. Instead, astronomers are getting a glimpse of what they were like in the past. It takes time for light to travel through space and reach our telescopes. Basically, that means looking into space is a trip back in time.
This is true even for objects that are quite close to us. The light you see from the Sun left it about 8 minutes, 20 seconds earlier. That’s the distance it takes for light from the Sun to travel to Earth.
You can easily do the math on this. All light – whether it’s sunlight, a flashlight or a light bulb in your home – travels at 186,000 miles (almost 300,000 kilometers) per second. That’s just over 11 million miles (about 18 million kilometers) per minute. The Sun is about 93 million miles (150 million kilometers) from Earth. That comes out to about 8 minutes, 20 seconds.
But the further away something is, the longer it takes to reach us. That’s why the light we see from Proxima Centauri, the closest star to us other than our Sun, is 4 years old; that is, it is about 25 trillion miles (about 40 trillion kilometers) away from Earth, so light takes just over four years to reach us. Or, as scientists like to say, four light years.
Recently, JWST observed Earendel, one of the most distant stars ever detected. The light seen by JWST from Earendel is about 12.9 billion years old.
The James Webb Space Telescope is looking much further back in time than previously possible with other telescopes, such as the Hubble Space Telescope. For example, while Hubble can see objects 60,000 times smaller than the human eye can, the JWST can see objects almost nine times smaller than even Hubble can.
The Big Bang
But is it possible to look back to the beginning of time?
The Big Bang is a term used to define the beginning of our universe as we know it. Scientists believe it happened about 13.8 billion years ago. It is the most widely accepted theory among physicists to explain the history of our universe.
The name is somewhat misleading, however, as it suggests that some kind of explosion, like fireworks, created the universe. The Big Bang represents the appearance of rapidly expanding space everywhere in the universe. The environment immediately after the Big Bang was like a cosmic fog that covered the universe, making it difficult for light to travel beyond it. Eventually, galaxies, stars and planets began to grow.
That’s why this era is called in the universe the “dark Cosmic ages.” As the universe continued to expand, the cosmic fog began to lift, and eventually light was able to travel freely through space. In fact, a few satellites saw the light left by the Big Bang, about 380,000 years after it happened. These telescopes were built to detect the splotchy glow left over from the Big Bang, whose light can be traced in the microwave band.
However, even 380,000 years after the Big Bang, there were no stars and galaxies. The universe was still a very dark place. The cosmic dark ages would not end until a few hundred million years later, when the first stars and galaxies began to form.
The James Webb space telescope was not designed to look as far back as the Big Bang, but instead to see the period when the first objects in the universe began to form and emit light. Before this time period, there was not much light to observe with the James Webb Space Telescope, given the conditions of the early universe and the lack of galaxies and stars.
It’s not just a bigger mirror looking back at the time period close to the Big Bang – astronomers have already done it using other satellites that look at microwave emission from very soon after the Big Bang. Thus, the James Webb Space Telescope observing the universe a few hundred million years after the Big Bang is not the limit of the telescope. Rather, that is really the mission of the telescope. It is an indication of where in the universe we expect the first light from stars and galaxies to emerge.
By studying ancient galaxies, scientists hope to understand the unique conditions of the early universe and gain insight into the processes that helped them form. This includes the evolution of supermassive black holes, the lifetimes of stars, and what exoplanets are made of – life outside our solar system.
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This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. It was written by: Adi Foord, University of Maryland, Baltimore County
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Adi Foord does not work for, consult with, share in, or be funded by any company or organization that would benefit from this article, nor has he disclosed any relevant affiliations beyond their academic appointment.
