Thursday, August 11, 2022

The James Webb Space Telescope is like a cosmic time machine. this is why

It’s been an exciting week with the release of stunning photos of our Universe from the James Webb Space Telescope (JWST).

Images like the one below give us the chance to see faint, distant galaxies as they were more than 13 billion years ago.

It’s the perfect time to step back and appreciate our first-class ticket to the depths of the Universe and how these images allow us to look back in time.


Above: The SMACS 0723 deep-field image was taken with an exposure of just 12.5 hours. The faint galaxies in this image emitted this light more than 13 billion years ago.

These images also raise interesting points about how the expansion of the Universe influences the way we calculate distances on a cosmological scale.

modern time travel

Looking back in time may seem like a strange concept, but it’s what space researchers do every day.

Our Universe is subject to the rules of physics, one of the best known ‘rules’ being the speed of light. And when we talk about ‘light’, we really mean all wavelengths of the electromagnetic spectrum, traveling at a whopping 300,000 kilometers (about 186,400 miles) per second.

Light travels so fast that in our daily lives it appears to be instantaneous. Even at these breakneck speeds, it still takes some time to travel anywhere in the cosmos.

When you look at the Moon, you actually see it as it was 1.3 seconds ago. It’s just a little glimpse back in time, but it’s still the past. The same goes for sunlight, except that photons (particles of light) emitted from the Sun’s surface travel just over 8 minutes before finally reaching Earth.

Our galaxy, the Milky Way, spans more than 100,000 light-years. And the beautiful newborn stars seen in JWST’s image of the Carina Nebula are 7,500 light-years away.

In other words, this nebula, as shown in the image, is from about 2000 years before the first writing is believed to have been invented in ancient Mesopotamia.

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The James Webb Space Telescope is like a cosmic time machine. this is whyThe Carina Nebula is a birthplace of stars. (NASA, ESA, CSA and STScI)

Every time we look away from Earth, we are looking back in time at how things once were. This is a superpower for astronomers because we can use light, observed over time, to try to unravel the mystery of our Universe.

What makes JWST spectacular

Space telescopes allow us to see certain ranges of light that cannot pass through Earth’s dense atmosphere. The Hubble Space Telescope was designed and optimized to use the ultraviolet (UV) and visible parts of the electromagnetic spectrum.

The JWST was designed to use a wide range of infrared light. And this is a key reason why JWST can see further back in time than Hubble.

The James Webb Space Telescope is like a cosmic time machine. this is why(NASA, J. Olmsted, STScI)

Above: The electromagnetic spectrum with the Hubble and JWST ranges. Hubble is optimized to see shorter wavelengths. These two telescopes complement each other, giving us a more complete picture of the Universe.

Galaxies emit a range of wavelengths in the electromagnetic spectrum, from gamma rays to radio waves and everything in between. All of these give us important information about the different physics that occur in a galaxy.

When galaxies are close to us, their light hasn’t changed much since it was emitted, and we can sample a wide range of these wavelengths to understand what’s going on inside them.

But when galaxies are extremely far away, we no longer have that luxury. Light from more distant galaxies, as we see it now, has been stretched to 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 the Universe has expanded. You are now in a completely different region of the electromagnetic spectrum. This is a phenomenon called a cosmological redshift.

And this is where the JWST really shines. The wide range of infrared wavelengths detectable by JWST allows it to see galaxies that Hubble never could. Combine this capability with the JWST’s huge mirror and superb pixel resolution, and you have the most powerful time machine in the known Universe.

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The age of light is not equal to the distance.

Using the JWST, we will be able to capture extremely distant galaxies as they were only 100 million years after the Big Bang, which occurred about 13.8 billion years ago. So we can see the light of 13,700 million years ago.

What’s about to mess with your brain, though, is that those galaxies aren’t 13.7 billion light-years away. The actual distance to those galaxies today would be ~46 billion light-years.

This discrepancy is all thanks to the expansion of the Universe, and it makes working on a large scale tricky.

The Universe is expanding due to something called dark energy. It is believed to be a universal constant, acting equally in all areas of space-time (the fabric of our Universe).

And the more the Universe expands, the greater the effect dark energy has on its expansion. So even though the Universe is 13.8 billion years old, it is actually about 93 billion light-years across.

We cannot see the effect 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 extraordinary age of technology. Just 100 years ago, we didn’t know that there were galaxies outside our own. Now we estimate that there are trillions, and we have many options.

And for the foreseeable future, JWST will take us on a journey through space and time each and every week.

Sara Webb, Postdoctoral Research Fellow, Center for Astrophysics and Supercomputing, Swinburne University of Technology.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Nation World News Desk
Nation World News Desk
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