Seven amazing conclusions that can be drawn based on the first image of the "deep field" from the James Webb telescope
Even taking into account the exposure of only 12.5 hours, the James Webb telescope managed to take such a picture of the "deep field", from which we can learn many valuable lessons.
Ethan Siegel
On July 11 and 12, 2022, our understanding of the universe changed once and for all. These days, the whole world saw the first images taken by the James Webb Space Telescope. In contrast to the previous releases of images taken by this telescope, which were only images used for calibration, testing and launching equipment, new images:
- Were made using a variety of tools and filters;
- Were made in order to collect scientifically valuable data;
- They were made so that for the first time in history they can be folded into full-color images that truly delight and delight the eye.
The very first published image was the image of the "deep field" – the massive star cluster SMACS 0723. Using a number of filters and instruments, the James Webb telescope "observed" this section of outer space for 12.5 hours. Although this may seem like a very long time, it is only 2% of the time that the Hubble Telescope spent on its deep field image: it created its first deep field image from 342 images over 23 days.
Based on the first image of Webb, we can draw seven stunning conclusions that will have a significant impact on the future of science.
1. The James Webb Telescope surpasses Hubble to a greater extent than we expected.
If we compare the capabilities of Webb and Hubble, it becomes clear that our newest space telescope can do much more in less time. Hubble has only a main mirror with a diameter of 2.4 meters, while Webb has a segmented mirror with a diameter of 6.5 meters. As a result, Webb's resolution is 270% higher (for light with the same wavelength), and its aperture is 730% higher than that of Hubble. If we think from the point of view exclusively of the laws of optics, exactly how much "Webb" should be better and faster than "Hubble" – without taking into account the advantages that "Webb" has in terms of cooling, wavelength range and instruments.
In other words, during the same observation time, Webb should "collect" 730% more light than Hubble. However, "Webb" – as you can see for yourself above, comparing the image of the galaxy cluster SMACS 0723 made by him with the image of "Hubble" – works even better.
Hubble's operating time is divided into "orbits": so, from its position in low Earth orbit, it makes a complete revolution around our planet every 96 minutes. In total, Hubble needed six "orbits" to create a composite image: four in the optical range and two in the infrared range. Based on simple mathematics, it can be calculated that six revolutions multiplied by 96 minutes per revolution will equal 9.6 hours (576 minutes).
However, the final image taken by Hubble included only the data it collected in 3.4 hours or 203 minutes, although the telescope devoted almost three times as much time to observing its object. For comparison, "Webb watched his target for 12.5 hours and received data in total for all these 12.5 hours.
What is the difference?
In the place where the surveillance is conducted. Since Hubble is orbiting the Earth, it spends more than 50% of its time interacting with the Earth (and the Earth's atmosphere) and can receive useful data only when nothing prevents it from observing its main target.
Meanwhile, "Webb" is located about 1.5 million kilometers from Earth, at the L2 Lagrange point. It is always facing away from the Sun, from the Earth and from the Moon. He does not have to face these obstacles in his observations at all. As a result, the effectiveness of its observations is almost 100%, while Hubble's is less than 50%. Such a high efficiency indicator will extend to all Webb observations, so the new telescope will provide scientists with higher-quality data at a faster rate than Hubble has ever been able to.
2. In those parts of space that are commonly called cosmic entrances, it is not always empty
In theory, we knew that this was the case, but after receiving the first images of the "deep field" made by Webb, we found the necessary evidence. There are vast areas of space in which there are no stars or galaxies at all. Ever since these "voids" were discovered, scientists have wondered if there could be objects too dim, small, low-mass or too far away for us to see them with the technology we had, or if these voids were actually 100% empty.
As the first images from the Webb telescope showed, there are many areas of space that seemed empty to Hubble, but in which Webb was able to see a lot of different objects. Yes, these areas do remain relatively "sparsely populated" areas of space, but they are not empty, as some hoped or feared. Webb can not only find these objects, but in many cases it is good to see and study their properties, while Hubble has not even been able to see them. This will help us achieve one of the main scientific goals of the James Webb project, namely, to tell us in great detail about how our universe originated and how it became what it is today.
3. We will finally be able to see the structure of the largest, most massive early galaxies
If you look at the faintest, most distant objects that the Hubble Space Telescope was able to detect, they most often look like ordinary "spots" in the sky. But with the improved Webb resolution, we can see that these distant objects are galaxies and that these galaxies often have a distinct structure.
We know that accretion and mergers play an important role in the evolution of galaxies and that the relative proportion of stars that arise under the influence of each other changes over time. In addition, we already know that galaxies within galactic groups or clusters evolve differently in terms of their shape (astronomers call this "morphology") than more isolated galaxies.
But here it is important to pay attention to the following point: an increase in resolution by 270% in reality means an increase in the number of pixels per light source by about 700%. A galaxy only 3×3 pixels in size for Hubble will already be 8×8 pixels in size for Webb. By seeing how the shapes and configurations of galaxies change in cosmic time and space, we will be able to understand how our universe has grown throughout its history.
4. The era of "cheating galaxies" has come to an end
If you are not a professional, you most likely have not heard about this problem: many of those galaxies that we at some point declared "the most distant", in fact turned out to be not galaxies at all. The reason is simple and banal: with the current technology at our disposal, we could not conduct a full-fledged spectroscopy of the most distant objects.
What do I mean by "full-fledged spectroscopy"?
Spectroscopy involves splitting incoming light into waves of different lengths and searching for either emission lines (peaks at certain wavelengths) or spectral absorption lines that correspond to quantum mechanical transitions of certain elements. If you are able to get a lot of lines by observing this or that element, you can determine how much the length of the emitted wave has changed due to the expansion of the universe.
With the help of the Hubble telescope, we cannot conduct such an analysis with respect to the most distant galaxies, because its wavelength sensitivity does not cover the infrared range. If we talk about the most distant "candidates" for galaxies, we have not conducted a full-fledged spectroscopy for about ten years.
However, with the advent of the James Webb telescope and its extremely high sensitivity to waves less than 2,000 nanometers in length, all these unknowns will simply disappear. Any galaxy with a redshift in its spectrum, such as HD1 and GN-z11, will now have to undergo a full-fledged spectroscopic "confirmation" procedure, which has never happened before. As the first spectra obtained from Webb show, now we can do this for all the galaxies that we want to check, and we will get data on the presence of oxygen, hydrogen and neon lines in the spectra of galaxies, if they are there.
Astronomers most often come in two types: those who make sensational statements about what is happening in space, having only a hint of the necessary evidence, and those who do not accept such statements until the evidence in their favor becomes irrefutable. Now that we have "James Webb", we finally have the opportunity to collect the irrefutable evidence necessary to accurately determine the properties of galaxies, and there is no need to guess and make assumptions anymore. Science is not about analyzing scarce data and choosing what to believe. Science should show us what is real, true and beyond doubt. Thanks to the possibilities of "Webb" in our reasoning about the universe, we will very soon replace "we think" with "we know".
5. We will have the opportunity to refute all variations of the modified gravity hypothesis
One of the most beautiful properties of the theory of dark matter is that it explains a huge variety of observed phenomena in so many different angles with the help of just this one addition. The theory of the universe in which dark matter is present can explain:
- How individual galaxies rotate and interact;
- How galaxies cluster and form clusters;
- How galaxies move inside clusters;
- How Gravitational Lensing Distorts and Magnifies objects located behind galaxies;
- What the large-scale structure of the universe looks like.
However, scientists are trying to explain some of these phenomena not with the help of dark matter, but with the idea of changing the laws of gravity. In the process of analyzing many properties of individual galaxies, this hypothesis looks quite promising if we consider them in isolation, but otherwise it does not help so well.
Some versions of the modified gravity hypothesis predict that the behavior of rotating galaxies will change over cosmic time; other versions indicate that young rotating galaxies and old rotating galaxies should have similar rotation curves. Now that we have Webb's resolution and spectroscopic capabilities at our disposal, we will be able to apply them to rotating galaxies observed throughout the universe and refute certain variations of the modified gravity hypothesis. It also means that now we will be able to test our theories of dark matter, which we could not do before. Whatever we find out as a result, it will be data about how the universe actually behaves.
6. We will get more detailed images of the centers of galaxy clusters
Have you ever wondered, looking at a massive cluster of galaxies, what is happening in the very center and on the outskirts of the brightest, most massive galaxy located in the middle of the cluster? We were able to see only the closest clusters of galaxies to us, and we only learned:
- How much gas is there;
- What do the stars look like inside them;
- How many globular star clusters are there inside them;
- How many dim satellite galaxies are around them.
However, in the case of most galaxy clusters, we can only see scattered, excess light, called intracluster light, which comes from them.
But now, with Webb's capabilities at our disposal, we will be able to see what structures are present around the central galaxies. This telescope will be able to see even small, dim galaxies, which otherwise would simply "merge" together at a lower resolution. We may even be able to use the data obtained to explain the distribution of light sources inside the cluster, as well as to reveal the properties of satellite galaxies and globular clusters in the halo of galaxies, which has never happened before. In the very first image of the "deep field" made by Webb, we already see something that would simply be inaccessible to us without it.
7. Webb's images in the mid-infrared range make it possible to detect the presence of organic substances, such as hydrocarbon compounds, throughout the universe
Yes, it's true: purely visually, the pictures taken by Webb on shorter wavelengths are the most exciting. The images taken by NIRCam, which contain wavelengths of approximately 600 to 5,000 nanometers, have a much higher resolution than MIRI images, which span wavelengths of 5,000 to 28,000 nanometers. After all, the resolution of your telescope is determined by the number of wavelengths of light that can fit in the diameter of its main mirror, and with a fixed diameter mirror of 6.5 meters, NIRCam images will give you a higher resolution each time than MIRI.
But the ability to capture the wavelengths of the mid-infrared range makes it possible to see what cannot be seen when shooting in the near infrared range, namely cosmic dust. This neutral matter is not only the main "ingredient" in the process of star formation, but also contains molecules that emit light only in a certain range. The galaxies glowing "green" in the MIRI images contain various chemical compounds, including hydrocarbons, which indicate the ability of these galaxies to host habitable worlds. All these data, put together, will help to reveal the greatest number of secrets of our universe.
The conclusions listed above are just the beginning of the great space science, which starts together with the first images obtained from the James Webb telescope. Many of the galaxies that are elongated into arcs or visually appear very red are subjected to gravitational lensing, and the first data obtained from Webb is good enough to immediately tell us which points of light are multiple images of the same galaxy, and which are different galaxies. Now that all of Webb's instruments have started working at full capacity, this deep field image has shown us the universe in a way we've never seen it before.
The most important thing to remember is that this "deep field" image, like all the images that were included in the first batch of published images from the Webb telescope, represent data collected in less than a day. For comparison, Hubble has been operating for 32 years, that is, Webb is able to surpass it on many fronts. We have more than 20 years of work with James Webb ahead of us, and new discoveries are just beginning. As Edwin Hubble eloquently put it, "with increasing distance, our knowledge becomes more and more scarce and disappears altogether. Eventually we reach the dim limit–the extreme limit of the capabilities of our telescopes. There we begin to measure shadows, to look among the ghostly errors in measurements for some landmarks that can hardly be called significant. The search will continue. And only when our empirical resources are exhausted will we have to move into the nebulous space of hypotheses."
With the unprecedented capabilities of the James Webb Telescope at our disposal, we are just beginning to see our universe–literally – in a completely new light.
