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The space telescope - the next generation is coming

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The telescope, named after James Webb, one of the leaders of NASA in its establishment and management for several years, will be placed at the Lagrange point, with a huge sunshade. The space telescope that will replace the old Hubble will make it possible to learn about the ancient stars and galaxies

Avi Blizovsky

Imaging the Space Telescope and B. A mirror six meters in diameter
Imaging the Space Telescope and B. A mirror six meters in diameter

One of the well-known Christmas carols is called "Silent Night", but the real night sky is neither quiet nor bright at all: supernova explosions spread, galaxies collide, black holes swallow whole stars. As far as silence is concerned. In these events, huge amounts of energy are released, but they take place at a distance of many light years. So much for clarity.

In order to get a clearer picture of these exciting events, astronomers strive to launch larger and more sophisticated telescopes into space. These efforts, which began back in the days of Lyman Spitzer, who first proposed the idea in 1946, were designed to allow scientists to observe space without the disturbances of the Earth's atmosphere and draw more precise conclusions.
After a hesitant start, the most famous telescope of this type, the Hubble, managed to deliver spectacular results. The device is named after one of the most important astronomers of the twentieth century, the man who proved beyond any doubt that the universe is vast and expanding and who made the first breakthrough in trying to estimate its age.

The planned successor of the Hubble telescope will not bear the name of a scientist, but rather of a bureaucrat. Probably one of the signs of the times. James Webb was the second director of the American space agency, NASA. If the plans do not go wrong, the Bev space telescope will be launched in 2010. During his tenure, James Bev succeeded in fulfilling NASA's plan to land a man on the moon in less than ten years; The schedule for the launch of the telescope that bears his name seems more relaxed.

Astronomers have learned to be grateful for every shred of real science that falls from the desks of the space station, controlled by NASA. If the Bev telescope is indeed built and launched (preliminary contracts for the implementation of the plan were already issued a few months ago), they are in for a rather rich feast.

Astronomical telescopes collect light using concave mirrors. The larger the mirror, the greater the power of the telescope. But the dimensions of a telescopic mirror in space depend on the dimensions of the rocket carrying it. To overcome this problem, the mirror of the "V" telescope will consist of 36 parts, which can be folded and stored in a compact space. When the mirror is deployed, it will reach six meters in diameter. Therefore, the light gathering capacity of Bev will be seven times that of Hubble.

The mirror parts will be thin. Thicknesses will not exceed two millimeters and it will be possible to make them from beryllium, the second metal in the list of light metals (glass is also a reasonable possibility). In space weight equals money, so this is a clear advantage. But such a thin mirror can be flexible. This is not a good feature: to prevent distortion in images it makes the mirror rigid. In an attempt to overcome this problem, each of the mirror parts of the telescope will be equipped with four fixings.

The smartest thing about the B telescope will probably be its location in space. The Hubble telescope orbits the Earth, and therefore significant parts of the sky are hidden from it in each rotation. This fact makes it difficult for him to look in a certain direction for a long time. And, on the other hand, it will hover in a strange region known as the Lagrange point, where the gravitational fields of the Earth and the Sun balance each other out and create a neutral zone. Therefore, if the scientists are interested in it, he can observe continuously in a certain direction.

The position of the telescope will also make it possible to protect it from the radiation of the sun and the earth (which reflects a large amount of light) with the help of a huge sunshade. Such protection cannot be provided to the holiday telescope around the Earth, because the Sun and the Earth constantly change their relative positions. The sunshade is essential, because the B telescope will not be tracking visible light, but infrared signals. In other words, it will absorb heat emission. To receive such signals, it must be cooled as much as possible; Its operating temperature is 35 degrees above absolute zero. To do this, the sunshade must return or dissipate all the solar energy reaching the telescope, except for one particle in 13 million.

The Bev telescope is designed to detect infrared radiation, because its mission is to look further into space (that is, also further back in time) than any other telescope. Because the universe is expanding, distant objects are rapidly receding from Earth. For this reason, their light appears redder than it would without motion. The reason for this is the Doppler effect, which in the sound field makes the sound of a receding siren deeper than that of a fixed siren.

Astronomers hope to use the telescope to observe the formation of galaxies, and even the formation of the earliest stars. No one has yet observed this first generation of stars, formed directly from the primordial hydrogen and helium created in the Big Bang. All the stars that can be seen today are relatively young. They contain relatively heavy elements, which - if the cosmological theory is correct - could only have formed in the cores of the earliest stars.

Hubble, as well as large telescopes on Earth, have provided some glimpses of early galaxies, some of which look different from the more common spiral and elliptical galaxies Maran is more familiar with. According to John Mader, a senior scientist in the telescope development program at NASA's Goddard Space Flight Center in Greenbelt, Maryland, it is supposed to track many ancient galaxies and provide information about the changes that have taken place in them. The study of these galaxies may help solve one of the central mysteries of modern physics - the nature of the so-called "dark matter". It is a substance that cannot actually be seen, but only tracked through its gravitational effects.

The B telescope will be able to discover distant galaxies, some of which from Earth appear to be standing in a row one after the other. The closer galaxy will bend the light of the more distant one relative to its mass. In effect, the telescope will act as a gravitational lens. In this way, it will provide data on the true mass of the nearby galaxy, which can be compared to the low value indicated by the amount of luminous material in it.

Such gravitational lenses have also been detected using existing telescopes, but rarely. Given the large number of galaxies that the B telescope will be able to see, it is expected to help astronomers better understand how dark matter is distributed in the universe.

The observation of infrared radiation necessarily encodes additional advantages. In this part of the spectrum, the planets absorb the energy of the stars around which they orbit and emit it back. Therefore the contrast between planets and larger stars is more apparent in infrared radiation.

According to Dr. Mader, for this reason the Bev telescope will be able to observe planets in the dimensions of Jupiter, which are close to the stars. How long it will take to launch a spaceship to those stars is a completely different question.

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