James Webb’s photos aren’t the deepest

The ace first scientific images from the James Webb Space Telescope they all left us in awe of their great resolve. With them, we were able to travel to distant places in the universe, located billions of light-years away. We have seen the light of objects that formed in ancient times and close to the big bang, the explosion that started it all. But does this mean that we have already hit rock bottom? Can’t there be instruments capable of going further than the James Webb? The truth is that there can be. In fact, they existed long before he left for his destination.

These are the instruments that study what is called microwave background radiation. This generally encompasses millimeter wave and microwave radio telescopes, located both in space and here on Earth. In the lyrics of David Galadidoctor of astrophysicism and resident astronomer at the Calar Alto observatory, “we already have telescopes that reach the bottom of the pool, what happens is that there is a lag between the background radiation and up to telescopes like the James Webb, and this Help us reduce this gap”.

But what is this background radiation? And what does distance have to do with the age of objects? To answer these questions, you have to take a long journey through time. As big as the age of the universe itself.

Basic concepts: distance and retrospective time

When talking about distances in space, the terms light years as a unit. These refer to the distance traveled by light in a certain number of years. For example, if we say an object is 20 light years away, that means that is the distance that light would travel in 20 years. Knowing that the speed of light is approximately 300,000,000 m/s and therefore travels 300,000,000 meters in a single second, the exact distance in meters can be calculated. Although this is a huge amount, that’s why other units are used.

There is another important concept, which is retrospective time or, which amounts to the same thing, the time that light spends traveling until it reaches where we are. For short distances, the two concepts are equivalent. But, as we increase these values, they stop matching due to the expansion of the universe. David Galadí explains it to us with an example.

“The Moon is 1.3 light-seconds away, and furthermore, the light reaching us left 1.3 seconds ago. But for more distant objects, it begins to count the expansion of the universe. Imagine a distant object from which we now receive light that it emitted 2 billion years ago. This is its retrospective time, we see it as it was 2,000 million years ago. However, during these 2,000 million years that light has traveled, the space between this object and our Galaxy has grown due to the expansion of the universe. Therefore, the distance to this object today is more 2000 million light-years away.

David Galadi, astrophysicist

How far can the James Webb measure?

The James Webb is capable of reaching objects at great distances, close to 13.8 billion light years. This is a key value, since the Big Bang, the great explosion that marked the beginning of the universe, is calculated to have occurred a few 13.8 billion years old. Would we then be witnessing the birth of the universe?

Not so fast, let us recall the notions of distance and retrospective time. “With this by James Webb, they tell us that we see things as they were 13,800 million years ago, practically the origin of the universe, as they say,” says Galadí. “But it’s his setback. During this time that photons have traveled, space has grown, and objects with a lookback time of 13.8 billion years are now at distances well over 13.8 billion light-years.”

Therefore, there is still uncharted territory. It would be appropriate to observe beyond where it seems that the James Webb. But what could we find?

At the moment we know that, also considering these concepts, if we look further, we continue to travel in time. Therefore, there would come a time when some of the celestial objects that we know would no longer be there, simply because they wouldn’t exist yet. “If the telescope is powerful enough, then we can see galaxies further and further away, and therefore in most primitive states of its evolution or its formation”, relates the astronomer consulted in this way. “Further on, we will see embryonic galaxies and there will come a time when, a little further on, we will see no more galaxies for the simple reason that they have not yet formed.”

Although that doesn’t necessarily mean you couldn’t see anything at all. “We’ll see if collapsing gas clouds, protogalaxies or whatever, but if you look far enough, there will come a time when there will be nothing left to see,” he explains. “And it’s not about a bigger or smaller telescope, it’s that if no stars or galaxies have formed yet, then they can’t be seen, period. As simple and as complex that.

L2, primary mirror, sunshade, James Webb Space Telescope
Credit: NASA.

What makes it different from other telescopes?

Part of the great potential of the James Webb lies in its ability to operate in the infrared range of the electromagnetic spectrum. This is very interesting, because the obscuration generated by gas and dust clouds can be better penetrated. But it’s not the main factor that differentiates it from Hubble. Indeed, if this telescope works mainly in the visible, it can also work in the near infrared.

Therefore, another of Super powers of the James Webb is related to your mirrors. Its primary mirror, with 6 meters in diameteris much larger than that of Hubble, which he was only 2.4 meters tall. This gives it a much higher sensitivity and resolution, just see the comparisons of the photographs of one and the other.

Thanks to these and other factors, he was able to eliminate what is considered the deepest and sharpest infrared images until. But that doesn’t mean it’s the deepest images. And it is that for decades there have been telescopes capable of going far beyond the reach of James Webb.

If we continue to travel through time, we will find the exact point at which these telescopes arrive. We have already seen that there comes a time when there would not even be any galaxies. We might see clouds of gas collapsing. But the James Webb couldn’t get in there, because not ready for this. Moreover, according to what David Galadí tells us, “this gas is essentially transparent”.

In fact we can go further than the James Webb

But we can always travel backwards, beyond the gas clouds. The universe, more and more primitive, becomes more and more “dense and hot”. We are approaching the big bang. “There comes a time when, if I look further afield, the gas (almost just hydrogen with a little helium) is so thick and warm which begins to be ionized. And here is almost the culmination of our story. it appears that ionized gas is opaque. Therefore, it becomes a curtain that covers everything and does not allow us to see beyond. In Galadí’s words, it’s “like trying see in the distance on a foggy day”. “No matter what telescope you use, you can’t see beyond it.”

So we arrived at the above swimming pool bottom. A background that James Webb cannot see. But this does not mean that there is no instrument capable of detecting it. The key lies in a second property of ionized gas. And it is that in addition to being opaque, shines more or less like sunlight.

“The light from it has been redshifted on its way through space, due to the expansion of the universe, so the cosmic background of ionized hydrogen light is no longer visible in visible light,” says Dr. Astrophysics. “It is so red-shifted that it is now observed in the microwave region.” We would therefore find ourselves facing the famous microwave background. A region of the universe that has been mapped using instruments such as the Planck satellite, that the European Space Agency (ESA) sent into space in 2009!

Microwave background card.

But, if it is the most powerful of the satellites dedicated to this purpose, others were launched before it, such as NASA’s WMAP, which supplemented the data taken by a multitude of telescopes and devices, on land and in space. We’ve spent decades getting information from this curtain of mist that the James Webb can’t reach. Therefore, it is true that we have images of the universe much deeper than any that this new telescope can give us. Does this mean that what we saw yesterday is not surprising? Quite the contrary. The James Webb deserves to be the mass leader he has become. The problem is that their success made us forget other legendary rock stars. Stars who also continue to work as on the first day. Let’s not forget them.

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