James Webb Space Telescope Hubble’s “direct descendants”

James Webb Space Telescope Hubble’s “direct descendants”

Back on May 11, 2009, space shuttle Atlantis took off from the Kennedy Space Flight Center. The mission of this flight is Hubble Space Telescope Maintenance This was the fifth Hubble maintenance mission. Because this is the last maintenance of this telescope. And it was also the last flight of Atlantis. that means The Hubble telescope, which has been in orbit since 1990, is nearing retirement.

So far, Hubble has been in heavy use for 31 years, although no exact release date has been set. But it is expected that it will continue to serve until the next decade is very much. After the Hubble era It will enter the era of the new space telescope. that NASA puts it to be “Hubble’s heir” This camera is called. James Webb Space Telescope

The James Webb Space Telescope has four main missions: 1. To search for light from the universe’s first stars and galaxies 2. To study the formation and evolution of galaxies 3. To understand the formation of stars and planetary systems. and 4. to study planetary systems and the origin of life

Because most of James Webb’s target objects are low-temperature objects. often obscured by a dense veil of gas dust. And it’s still so far away that the universe’s amplification stretches its spectrum further towards the red. Surveying these objects when studied in the near-infrared region is more effective than surveyed in the white or visible region of the human eye. As a result, the James Webb is a true infrared camera. It’s not a multi-band camera like the Hubble that can explore from infrared to ultraviolet. The James Webb camera has a much higher infrared sensitivity than Hubble. Range from 0.6 microns (near the red line and near infrared) to 28 microns.

Because the James Webb camera is an infrared ray camera and is very sensitive. Plus the presence of many infrared radiation sources nearby the camera. In particular, the heat from the camera device itself radiates infrared radiation. The sun, the earth and the moon also radiate infrared radiation. Therefore, the camera device must operate at very low temperatures. A huge shield was needed to block the light from the sun, the earth and the moon, creating a permanent shade for the camera and kit. plus helium cooling system Allows the camera to operate in cryogenic conditions as low as 40 Kelvin (-230 °C).

James Webb’s primary mirror is 6.5 meters in diameter, developed by Axis Technologies. It is made up of 18 hexagonal mirrors interlacing each other, acting like a single large mirror. Each mirror must be folded while inside the rocket. Ascended into space and then unfolded Computer-controlled sensors measure their position precisely to ensure that each mirror is properly positioned and angled.

Even James Webb’s primary mirror is two and a half times wider than Hubble’s. and the area of ​​u200bu200blighted six times more than Hubble, but surprisingly its total weight is lighter than Hubble’s glass.

James Edwin Webb

The Hubble camera has an active spectrum going to ultraviolet. Which has a wavelength as short as 0.1 microns, so the curvature of the glass must not exceed 0.1 microns in order for the glass to maintain the correct curvature shape. Therefore, it is necessary to make the glass thicker. but thicker glass It brings more weight as a shadow on the body As a result, Hubble’s glass, which is made of glass, weighs up to 1 ton.

James Webb’s glass is thinner. The curvature is also more accurate than Hubble’s glass. Made of lightweight beryllium with gold plating. Each door is secured with a distance adjuster attached to the frame. The total weight of both glass and frame is only 625 kg. Beryllium has many magical properties in mirroring. It is a very strong light metal. less dull even when exposed to air Beryllium alloys usually have very high heat resistance properties. corrosion resistant is a good heat insulator and molded well Therefore, it is commonly used to make parts in many supersonic aircraft.

Webb will have a better resolving power of 0.1 pips at a wavelength of 2 microns. at this wavelength The camera can see an object with an angular magnitude of 0.1 pips. An object with an angular magnitude of 1 pip is comparable to a soccer ball at a distance of 550 km in light sensitivity. James Webb is 10 to 100 times more sensitive than Hubble, in other words. James Webb can even see stars that are ten billion times fainter than the human eye.

James Webb’s orbit is very different from Hubble’s. The Hubble telescope orbits the Earth in a nearly circular orbit at an altitude of about 560 km, which is classified as a low orbit satellite. The James Webb telescope is always positioned opposite the sun. It is 1,500,000 kilometers away from the Earth, near a point called Lagrange L2 (Lagrange L2) Objects at this point orbit the Sun in a stable manner with the Earth. Normally, objects orbiting the Sun are outside the Earth’s orbit. will have an orbit longer than 1 year or move more slowly But if an object is located at point L2, it will be balanced due to the complementary attraction of both the Earth and the Sun. make that object move with the world Any ship that arrives at this point will be able to move with the world without increasing propulsion. but in reality The craft will also need some rockets to help stabilize it. But it’s just a low-powered rocket.

At L2, this might be a good location for someone who wants to see a total solar eclipse because the Earth is right in front of the Sun. but appears smaller than the sun Around 90 percent of the sun is blocked by the Earth, so only an annular solar eclipse is visible at this location. However, James Webb is not exactly at L2, but will orbit L2 with an orbital radius of 800,000 km, large enough to pass the shadow eclipse region. There will never be a solar eclipse, not even a partial solar eclipse. and will not have a chance to see the full moon Even when the moon is at its furthest from the sun, only a thin fraction of the moon is visible.

The position of the Earth, the Sun and the Moon is close to each other from the perspective of the camera. This makes it easy to design an umbrella to block infrared radiation from the three major sources. Because it is designed to cover only one side is enough.

Compare the size of the primary mirror between Hubble and James Webb. The Hubble mirror has a diameter. 2.4 m. James Webb has a diameter. 6.5 m. and has an area that receives more light than almost 6 equal

But having the camera to be as far as fifteen hundred thousand kilometers Four times as far as the moon, or four times the distance of the moon, means that scheduled maintenance missions like the Hubble telescope are impossible, so design and testing must be flawless. If there were any mistakes, there would be no chance of making excuses.

James Webb was originally scheduled to go into space in 2014, but the project faced so many hurricanes that it had to postpone it again and again. The latest release date, which is unlikely to be postponed, is December 22, 2021.

Astronomers around the world have great expectations for the James Webb telescope. Numerous discoveries and research papers over the years have left the camera James Webb to solve. When did the James Webb cameras go into service? The study of astronomy will need another leap forward. Just as Hubble has done for the past three decades.