Five things that James Webb will not be able to observe and discover

The James Webb Space Telescope is the largest space telescope ever designed, built, and sent into space by man. It was launched with an Ariane V rocket on December 25, 2021 and is traveling towards the Lagrangian point L2 of the Earth-Sun system, where it will remain at least for the next 10 years.

This extraordinary masterpiece of engineering, technology and science will be able to observe space like never before, for its position and for the instrumentation at its disposal. It will answer many of the great questions that man has been asking himself for centuries, allowing new studies and cutting-edge research projects so far only hoped for. However there are a number of answers that the Webb will not yet give. Over the past few weeks we have collected some of the questions like “Will the James Webb observe …?” Asked on the Webb, and some of these have been definitely curious.

The Big Bang

The James Webb with its 6.5 meter diameter mirror will be able to collect a lot of light, even the faintest light coming from the early Universe. It is in fact one of the scientific objectives of the telescope to see the formation of the first stars, galaxies and black holes. This will be possible because light travels at finite speed, so looking far beyond space we see the celestial bodies as they were at the time of the emission of the light we collect, not as they are now. But will the Webb be able to observe exactly the Big Bang, which is what the Universe began with?

According to the most accredited cosmological theory today, the cosmos as we know it was born from the initial explosion of one singularity, a very dense and limited region of space. All the initial mass was concentrated in it, which would later go to make up the Universe itself, in the form of energy at a very high temperature. So no radiation, just a dense lump of energy. In an initial instant t = 0 this singularity “exploded” and then expanded in all directions, giving rise to the Universe. This, according to data provided by ESA’s Planck Surveyor, would have happened 13.7 billion years ago.

In the first moments after this “great explosion”, the Big Bang in fact, most of the evolution of the Universe took place. The density decreased, the temperature also decreased, and this cooling allowed the formation of the primordial matter. The first stars lit up 400 million years later as a result of the gravitational attraction of matter. The Universe was thus out of its dark era (in English Dark Age).

Universe Evolution
History of the evolution of the Universe since the Big Bang. Credits: ESA, Translation: Astrospace

Therefore the Webb not he will be able to observe the great explosion with which the cosmos was born. It can tell us a lot about the very first objects that grew out of the Big Bang material, and that could be very different from what we see today. There is also the possibility that they have grown rapidly and been destroyed, so that no more traces will be found in recent material. However the first million years of the universe’s life were completely dark. So there is no light to capture, and the Webb will have nothing to observe in the Dark Age that preceded the formation of the first stars. This is if the Big Bang theory, the most accredited to date, is true as we know it.

Russel’s teapot

Someone has actually wondered if the James Webb will be able to observe Russel’s teapot. The answer is obviously no. Russel’s teapot is in fact a metaphor, a psychological experiment introduced in the 1950s by the English mathematician and philosopher Bertrand Russell. It hypothesizes that in orbit around the Sun, between Mars and the Earth, there is a small porcelain teapot, and that since it is small, it does not emit its own radiation and does not reflect that of the Sun (significantly) it would be impossible to observe. . The imaginary experiment ends by saying that just because it is not possible to observe or detect it, no one would really believe in the presence of a teapot orbiting the sun.

The metaphor introduced by Russell served to demonstrate, in a somewhat goliardic way, the principle according to which the burden of proof does not lie with the skeptic. In fact, if someone believed in the existence of this teapot, it would be up to the believer to prove its existence and not to the skeptic who doubts its presence. But could the Webb really look for this teapot? The telescope is primarily aimed at outer space. A teapot in orbit between Earth and Mars would therefore be too close to observe, even if it were there. Furthermore, since the telescope is primarily suited to observing in infrared radiation, a small teapot that does not emit this radiation would be impossible to detect.

The landing sites of the Apollo missions

Another recurring question is whether the James Webb Space Telescope would be able to observe the landing sites of the Apollo missions and the infamous “flag on the moon”. This question has often appeared in conspiracy circles where the 1960s moon landing is denied. Wanting to answer this question, it is important to immediately note again that the Webb will not be able to observe the Moon, being “behind it”.

To function, the telescope needs to keep its mirrors at temperatures of over -200 ° C. To do this, it protects itself from radiation from the Sun, the Earth and even the Moon, with a thermal shield. “Turning” to observe the Earth and the Moon would be in effect suicide. Furthermore, it should be noted that several probes in orbit around our satellite have already observed the traces left by the Apollo missions on the lunar surface.

The landing site and the tracks left by the astronauts of the Apollo 17 mission, photographed with NASA's Lunar Reconnaissance Orbiter (LRO).
The landing site and the tracks left by the astronauts of the Apollo 17 mission, photographed with NASA’s Lunar Reconnaissance Orbiter (LRO).

The alien

With the Webb it will be possible to observe many more exoplanets than has been done so far. In particular, with the data that the telescope will collect, researchers will be able to establish their constitution more accurately and investigate the presence of water, even in the liquid state. Certainly among the ambitions of the scientific community is that of being able to identify other forms of life in the cosmos, perhaps in our galaxy. However this does not mean that the Webb “will find the aliens”.

Since the Webb will hunt for exoplanets of the habitability range, in the event that on one of them there was life according to the scientists, the telescope could reveal it in about sixty hours of observation. To achieve this, first of all, the discovery of biosignatures in the atmospheres of exoplanets, which is possible through spectroscopy. The compounds that can indicate the presence of life, in particular, are methane and carbon dioxide.

A promising candidate is TRAPPIST-1e. The researchers found that the Webb may only need 5-10 planet transits measured with the telescope’s Near-Infrared Spectrograph (NIRSpec) to confirm important revelations about its atmosphere. However, this will only happen if the atmospheric pressure of its cloud layer falls within a certain range. Otherwise, observation of up to 50 transits of TRAPPIST-1e in front of the star may be required, which could require more than 200 hours of observation with the Webb!

There are many potential candidates among the habitable planets, possibly millions in our galaxy, but that does not mean that we should expect to discover humanoid beings living in conditions similar to ours on planet Earth. Rather they are trying to find themselves on other planets the same characteristics that here allow the birth of life forms even in their simplest constitution. Yes, the Webb could find out, providing important clues to the big question mark about our loneliness in the Universe.

The Hubble photographed by the Space Shuttle Discovery.  Credits: NASA.
The Hubble photographed by the Space Shuttle Discovery. Credits: NASA.

The Hubble telescope

Many have also wondered if the James Webb will be able to photograph the Hubble Space Telescope. The question is curious and surely NASA has thought of something more important for the largest and most powerful space telescope ever built to do. But assuming someone really wants to observe the Hubble, would it be possible to do so? No.

The answer is similar to the previous ones, the Hubble telescope is in orbit around the Earth, at about 600 km of altitude. In order to observe it, the Webb should therefore “turn around”, with the consequence of exposing its mirrors to the heat of the Sun. The Lagrangian point L2 on which it is located is in fact a privileged position to observe external space, precisely because it is located on an imaginary line connecting Sun, Earth and point L2. Furthermore, in the hypothesis that the Webb were able to turn around, it would only see a bright dot, too small to be observed precisely.

To learn more about the technical characteristics of the James Webb and more, our guide is available here.

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