(ORDO NEWS) — It’s been an exciting week of amazing photos of our universe taken by the James Webb Space Telescope (JWST).
Images such as the one below give us the opportunity to see dim, distant galaxies as they were more than 13 billion years ago.
This is the perfect time to take a step back and appreciate our first-class ticket to the depths of the universe and how these images allow us to glimpse into the past.
These images also raise an interesting question about how the expansion of the universe affects how we calculate distances on a cosmological scale.
Modern time travel
Traveling into the past may seem like a strange concept, but this is exactly what space explorers do every day.
Our Universe is limited by the rules of physics, one of the most famous “rules” is the speed of light. When we talk about light, we are referring to all wavelengths of the electromagnetic spectrum, which travel at about 300,000 kilometers (about 186,400 miles) per second.
Light travels so fast that in our daily life it seems to be instantaneous. But even at such breakneck speeds, it takes some time for light to travel anywhere in space.
When you look at the Moon, you see it as it was 1.3 seconds ago. It’s just a tiny look back in time, but it’s still the past. The same thing happens with sunlight, only photons (particles of light) emitted from the surface of the Sun travel a little over 8 minutes before reaching the Earth.
Our galaxy, the Milky Way, spans 100,000+ light years. And the beautiful newborn stars seen in the JWST image of the Carina Nebula are 7,500 light-years away.
In other words, this nebula, shown in the picture, appeared about 2,000 years earlier than in ancient Mesopotamia, where the first writing is believed to have been invented.
Every time we look far away from Earth, we look back in time to see how things once were. This is a superpower for astronomers because we can use the light observed over time to try to unravel the mystery of our universe.
What makes JWST impressive
Space telescopes allow us to see certain ranges of light that cannot pass through Earth’s dense atmosphere. The Hubble Space Telescope has been designed and optimized to use the ultraviolet (UV) and visible portions of the electromagnetic spectrum.
JWST has been designed to use a wide range of infrared light. And this is the key reason JWST can see further into the past than Hubble.
Galaxies emit a range of wavelengths of the electromagnetic spectrum, from gamma rays to radio waves and everything in between. All of them give us important information about the various physical processes taking place in the galaxy.
When galaxies are close to us, their light hasn’t changed much since they were emitted, and we can explore a wide range of these wavelengths to understand what’s going on inside them.
But when the galaxies are very far away, we no longer have that luxury. The light from the most distant galaxies as we see it now has been stretched into longer, redder wavelengths due to the expansion of the universe.
This means that some of the light that would have been visible to our eyes when it was first emitted has lost energy as a result of the expansion of the universe. Now it is in a completely different region of the electromagnetic spectrum. This phenomenon is called cosmological redshift.
And this is where JWST really shines. The wide range of infrared wavelengths detected by the JWST allows it to see galaxies that Hubble could never see. Combine these capabilities with JWST’s huge mirror and superior pixel resolution and you have the most powerful time machine in the known universe.
Light age is not equal to distance
With JWST, we will be able to capture extremely distant galaxies as they were just 100 million years after the Big Bang, which happened about 13.8 billion years ago. Thus, we will be able to see the light 13.7 billion years ago.
However, what will blow your mind right now is that these galaxies are not 13.7 billion light years away. The actual distance to these galaxies today is ~46 billion light years.
This discrepancy is explained by the expansion of the universe and makes it difficult to work on very large scales.
The universe is expanding thanks to something called dark energy. It is believed that this is a universal constant that acts the same in all areas of space-time (the fabric of our Universe).
And the more the Universe expands, the more influence dark energy has on its expansion. This is why, although the universe is 13.8 billion years old, its real size is about 93 billion light years.
We cannot observe the influence of dark energy on a galactic scale (within the Milky Way), but we can see it at much greater cosmological distances.
Sit back and enjoy
We live in an amazing time of technology. Just 100 years ago, we did not know about the existence of galaxies outside our planet. Now, by our estimates, there are trillions of them, and we are spoiled for choice.
And for the foreseeable future, JWST will take us on a journey through space and time every week.”
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