The James Webb Space Telescope (JWST) has had a major impact on astronomy since it began sending data back to Earth in 2022. One of its most revolutionary results is The most distant galaxy It is the largest galaxy ever seen, but because light doesn’t travel instantaneously – it travels at about 300 million meters (985 million feet) per second in a vacuum – the galaxy we see is not as it is today, but as it was billions of years ago.
Furthermore, our universe is estimated to be 13.8 billion years old. Therefore, we must assume that the most distant galaxy we can see is within 13.8 billion light years. (A light year is the distance light travels in one year.)Cosmic Horizon” and anything beyond that can’t be seen with a telescope. And since nothing can travel through space faster than c, it’s impossible for galaxies that are more than 13.8 billion light years away to have any effect on Earth. Right?
No. I wish the universe were that simple.
“A Cosmic Horizon “This is the maximum distance at which we could potentially get information,” Jake Helton, an astronomer at the University of Arizona and part of the JWST Advanced Deep Space Exploration (JADES) team, told Space.com.
“There are a few different types of cosmic horizons,” Helton continues, “each with a different definition and dependent on different cosmological quantities. The most important one here is the cosmic horizon, which is the maximum distance from the cosmic horizon that light can reach to Earth. Age of the UniverseThis defines
The edge of the observable universe.”
Related: James Webb Space Telescope discovers most distant galaxy ever (image)
March 2024, Jade Scientists have revealed that powerful telescopes have discovered JADES-GS-z14-0, the most distant and earliest galaxy humanity has ever seen. However, there are contradictory findings. Jade-GS-z14-0 It is located approximately 33.8 billion light years away.
How can we see light from objects so far away that the universe is still too old for light to reach us? JADES-GS-z14-0 is 33.8 billion light years away, so wouldn’t that mean we would see it as it was 33.8 billion years ago? Surely this would challenge estimates of the age of the universe?
Not so. Again, this is proof that the universe has a way of subverting sensible logical conclusions.
“How can we see a distant galaxy like JADES-GS-z14-0, which is more than 13.8 billion light years away and whose light would take longer to reach us than the age of the universe?” Helton asked rhetorically. “The answer is The expansion of the universe“
Seeing a galaxy older than time itself
If the universe was stationary, it would take 33.8 billion years for light from a galaxy 33.8 billion light years away to reach Earth. That would be the end of it. However, in the early 1900s, Edwin Hubble discovered that distant galaxies appear to be moving away from each other, and the farther apart they are, the faster they are moving. This means that the universe is not stationary, but is expanding.
In 1998, as the 20th century drew to a close, two separate teams of astronomers discovered that not only is the universe expanding, but that its expansion is To accelerateThe force responsible is a mystery but has been tentatively named “dark energy.”
The 13.8 billion year history of the universe has seen two very distinct periods of expansion. The first is what is now commonly referred to asbig bang”
During this inflationary period, the volume of the universe increased by a factor of 10^26 (10 followed by 25 zeros), which is the equivalent of your fingernail suddenly growing from one nanometer per second to 10.6 light years (62). Trillion The universe was a mile long. During this time, the universe was dominated by energy. An era dominated by energy.
47,000 years after the Big Bang, the epoch of matter began. Eventually, the expansion of the universe cooled it down enough that proton Formed from quark and Gluonand the protons bond Electronic The first hydrogen atoms were formed, which then formed the first stars and galaxies. During this period, the expansion of the universe due to the Big Bang slowed down and nearly stopped.
The matter-dominated epoch came to a surprising end when the universe was just under 10 billion years old, when the universe suddenly began to expand rapidly again. And that expansion accelerated and accelerated, and is still accelerating today. This third critical period in the universe is called the dark energy-dominated epoch, the epoch we live in today.
Thanks to these periods of cosmic expansion, the light from JADES-GS-z14-0 actually traveled only 13.5 billion years to JWST and Earth, even though its source is much farther away than that today. This means that JWST is looking at JADES-GS-z14-0 as it was 300 million years after the Big Bang. Without the expansion of the universe, JADES-GS-z14-0 would still be about 13.5 billion light-years away, but small local motions would still be moving nearby galaxies closer and further apart. However, such galaxy motions would be far from the kind caused by the expansion of the universe.
According to Helton, the cosmic horizon, or “photon horizon,” is a sphere bounded by the expansion of the universe at a distance of about 46.1 billion light years. This is the actual horizon beyond which we can no longer “see” galaxies. Galaxy JADES-GS-z14-0 lies right within that horizon.
To avoid confusion, astronomers actually use two scales of distance measurement: the comoving distance, which excludes the expansion of the universe as a factor, and the proper distance, which includes it. So, JADES-GS-z14-0 has a comoving distance of 13.5 billion light years, but a proper distance of 33.8 billion light years.
However, JADES-GS-z14-0 and other distant, ancient galaxies aren’t always visible.
We are fortunate to live in an age where we have the James Webb Space Telescope.
The fact that JWST can see JADES-GS-z14-0 was onceThere is a causal relationshipIn other words, signals from JADES-GS-z14-0 could potentially reach us in the Milky Way, and thus the “cause” of this ancient galaxy could “influence” our galaxy in this modern time in the universe.
“Every galaxy we can observe lies within the particle horizon and must have had a causal relationship with us at some point in the history of the universe,” Helton said.
But this is no longer the case: galaxies like JADES-GS-z14-0, and others discovered by JADES, are now so far away, and moving so rapidly away from us due to dark energy, that a signal sent to them today would not reach us. That’s because their photon horizons are moving away from us at the speed of light. Really The space between distant objects, the Milky Way, and their galaxies is expanding Faster than The speed of light.
This may be hard to believe, but Albert Einstein’Theory Special theory of relativity The speed of light is set as the universal speed limit, but this is only the rule for moving objects with mass. Through These are rules of space, not rules of the structure of space itself.
About 2 trillion years after Earth and humanity are gone, the expansion of the universe will prevent us from seeing any galaxies outside our own Milky Way, whatever intelligent life there may be replacing us (if there is one). Local Groups Its diameter is about 10 million light years.
It’s a solemn thought, and it means humanity is living at a unique point in the history of the universe, when the most distant galaxies are still within our field of vision. We can learn more about the universe and its origins than any intelligent life that comes after us. Astronomers, including Helton, intend to use the JWST to make the most of this cosmic privilege.
“In cooperation with JWST, JADES collaboration “Writing scientific papers on JWST has been a great experience,” Helton said. “Like the paper I wrote recently,
JADES-GS-z14-0 was a most rewarding and exciting experience
This was the beginning of my research career.”
