These days, the Web Space Telescope is expected to take the place of the Hubble Space Telescope after more than 30 years of operation. How far in space and time (!) Will Web be able to reach? What does he see that a human eye is unable to perceive? And how can he help us discover the secrets of the creation of the universe?
Reporter: Gilad Yasur, Young Galileo
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On April 24, 1990, the Hubble Space Telescope was launched. Over the years he has provided us with spectacular images and made countless discoveries that have advanced science. A new space telescope is being launched these days – the James Webb Space Telescope. Thanks to it we can make distant observations of the universe as it was not long after the Big Bang, look at the hidden places where stars are born to deepen our knowledge of the process of their formation, and explore extrasolar planets (planets that are outside the solar system).
What’s special about a space telescope and how we can discover all these things? First of all it is big, very big. Hubble’s main mirror diameter is 2.4 meters. It is the main appearance of a telescope that allows it to collect light. Unlike the first telescopes made with lenses, modern telescopes, especially the large ones, are based on mirrors. The larger the mirror, the higher the light collection capacity of the telescope. Webb’s main mirror diameter is 6.5 meters, which means it will be able to collect much more light than mourning and observe dim and very distant objects.
Another uniqueness of it is the type of radiation it is able to absorb. Humans are able to see light in the color range between red and purple – the visible light range. But this is only a very small part of all the types of radiation that exist in nature. Every hot body, for example, we emit infrared radiation – light that we are unable to see. Different animals are able to recognize this light, and for example the mosquitoes know how to find us even in the dark. What about the web and mosquitoes? Before that we will explain about the expansion of the universe.
Looking to the past
In the late 1920s, scientist Edwin Hubble (after whom the Space Telescope is named) announced his revolutionary discovery: the universe is expanding. He looked at many galaxies in the universe and saw that they were moving away from us. He recognized that the farther away the galaxy is, the faster it moves away from us. What can explain this?
Are we a very unpleasant galaxy and everyone wants to get away from us, or is this a general phenomenon of the universe? The second possibility is more plausible, so Hubble realized that the only way any point in the universe would see the rest of the universe move away from it, is if the universe itself expands.
The expanding universe can be likened to a loaf of puffed bread with raisins. As the bread swells, the distance between the raisins increases, and each raisin sees the others move away from it. If we were a raisin, the farther we look at a raisin, the farther it will go, because the distance between us is full of puffed dough. If there was a wire that connects two raisins before swelling, in order to continue to connect them it would have to lengthen and lengthen all the time.
We’ll be back to the web. And is planned to be viewed very, very far. In space, and in time. The farther he looks, he will see galaxies whose light took longer to reach us, so in fact he will look to the past! And is designed to look back more than 13.5 billion years in time, almost to the beginning of time, toward the galaxies farthest from us, thus exploring the young universe after the Big Bang.
And in watching so far, that is why the light he will see moves in the universe billions of years. The light also shifts to red because blue light changes to red and red light changes to sub-red (the general phenomenon is called the Doppler effect; most of you are familiar with it because the sound of an ambulance horn changes from high to low as the ambulance passes you).
And will look so far that the distraction effect of red will make the light, which was originally in the realm of visible light, appear to us to belong to the realm of the sub-red. Therefore, like mosquitoes, and in looking at this frequency range.
Seeing stars are born
Focusing on the infrared will help Web also watch new stars. Many of the stars are born in nebulae. A nebula is a huge cloud of matter (made mostly of hydrogen and helium) that collapses into itself, until the density of matter is high enough for a star to form. Because the process takes place in the heart of the nebula, the abundant material around interferes with seeing all the action taking place in the center.
Even though the substance interferes with visible light, the infrared radiation passes through the nebula almost uninterrupted. This way he will be able to see the formation of the stars.
How do you launch a giant into space?
We said a web is a giant telescope, it’s actually bigger than any spacecraft. So how do you launch it into space? To get into the launcher it folds, just like origami.
Unlike Hubble’s main mirror, which is one complete mirror, Webb’s main mirror consists of 18 small hexagonal mirrors, all of which together form one large mirror. During launch, six mirrors (three on each side) fold out, thus entering the launcher. Only about two weeks after launch, when it is already farther from us from the moon, will it deploy the side mirror parts, and the main mirror will be completed.
In addition, the place of and in space will be very different from that of mourning. Hubble orbits the earth at an altitude of 540 kilometers, but the distance of Webb from us will be much greater. Why?
Like we said, every hot body emits infrared radiation. The earth itself is a source of much infrared radiation, as are the moon and sun. If he wanted to keep his observations from a place similar to that of mourning, it’s like a bird would want to go out and listen to a bird sing a rare, gentle and silent song from the middle of bustling Tel Aviv.
So the goal is to launch V and away from Earth, but not too far, so that he can communicate with us easily.
Where is there telescope parking?
The grunge points of the sun and the earth are five special points in space in which if a spacecraft is parked, it will stay there and attack the sun at exactly the same speed as the earth orbits it. And is launched towards a point to the second grange – L2. To reach it, it takes off from Earth in the opposite direction from the sun, and flies a distance of a million and a half kilometers. The journey will last about a month.
That is, and will be almost 3,000 times farther from mourning. There, at point L2, the Earth’s and moon’s radiation will be much weaker, but will not disappear completely. And so that it does not heat up and burn due to the proximity to the sun, a “blanket” of five layers is installed on it, whose function is to protect it from the sun and keep it at a very low temperature. This “blanket” will help him maintain a temperature of minus 223 degrees Celsius. This way he will be cold enough that his self-heat radiation will not interfere with his sensors making the observations. Like the takeoff, those same protective layers remain folded at takeoff and will open fully, to the size of a tennis court (!), Only about six days after takeoff, during its journey to the L2 point. The process must be extremely slow and delicate, since the thickness of each of the layers is a few microns, less than the thickness of its hair.
And is the next great step that humanity seeks to climb in its path of understanding the universe and all that is in it.
The author is a graduate student in physics at the Hebrew University and an instructor at the “Big Bear” Association for Observational Astronomy dubagdola.com
The article was published in the January 2022 issue of Young Galileo Magazine
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