The James Webb space telescope or JWST will replace the Hubble space telescope. It will help us to see the universe as it was shortly after the big bang. It was named after the second head of NAS James Webb. James Webb headed the office of space affairs from 1961 to 1968. This new telescope was first planned for launch into orbit in 2007 but has since been delayed more than once, now it’s been scheduled for 18 December 2012. After 2030 the Hubble will go on a well deserved rest since its launch in 1990 its provided more than a million images of thousands of stars, nebulae, planets and galaxies. The Hubble captured images of stars that are show about 380 million years after the big bang which supposedly happened 13.7 billion years ago. These objects may no longer exist, we still see their light. Now we expect James Webb to show us the universe as it was only 100 to 250 million years after its birth. It can transform our current understanding of the structure of the universe. The Spitzer space telescope and Hubble telescopes have collected data of gas shells of about a hundred planets. According to experts, the James Webb is capable of exploring the atmospheres of more than 300 different exoplanets.
The working of James Webb space telescope
The James Webb is an orbiting infrared observatory that will investigate the thermal radiation of space objects. When heated to a certain temperature, all solids and liquids emit energy in the infrared spectrum; here there is a relationship between wavelength and temperature. The higher the temperature, there will shorter the wavelength and higher the radiation intensity. James Webb sensitive equipment will be able to study the cold exoplanets with surface temperatures of up to 27° Celsius. An important quality of this new telescope is that it will revolve around the sun and not the earth unlike Hubble which is located at an altitude of about 570 kilometers in low earth orbit. With the James Webb orbiting the sun, it will be impossible for the earth to interfere with it, however he James Webb will move in sync with the earth to maintain strong communication yet the distance from the James Webb to the earth will be between about 374,000 to 1.5 million kilometers in the direction opposite of the sun. So its design must be extremely reliable.
The James Webb telescope weighs 6.2 tones. The main mirror of the telescope is with a diameter of 6.5 meters and a colleting area of 25 square meters, it resembles a giant honeycomb consisting of 18 sections. Due to its impressive size, the main has to be folded for start up; this giant mirror will capture light from the most distant galaxies. The mirror can create a clear picture and eliminate distortion. A special type of beryllium was used in the mirror which retains its shape at low cryogenics temperature. The front of the mirror is covered with a layer of 48.25 grams of gold, 100 nanometers thick; such a coating best reflects infrared radiation. A small secondary mirror opposite the main mirror, it receives light from the main mirror and directs it to instruments at the rear of the telescope. The sunshield is with a length of 20 meters and width of 7 meters. It composed of very thin layers of kapton polyimide film which protects the mirror and tools from sunlight and cools the telescope’s ultra sensitive matrices to 220° Celsius.
The NIRCam- Near Infrared Camera is the main set of eyes of the telescope, with the NIRCam we expect to be able to view the oldest stars in the universe and he planets around them. The nurse back near infrared spectrograph will collect information on both physical and chemical properties of an object. And the MIRI mid-infrared instrument will allow you to see stars being born many unknown objects of the Kepler belt. Then the near infrared imager and sliteless spectrograph or NIRIIS camera is aimed at finding exoplanets and the first light of distant objects. Finally the FGS- Fine Guidance Sensor helps accurately point the telescope for higher quality images updates its position in space sixteen times per second and controls the operation the steering and main mirrors. They are planning to launch the telescope with the help of the European launch vehicle Ariana 5 from the kourou Cosmodrome in French Guiana space center. The device is designed for between 5 to 10 years of operation but, it may serve longer. If everything goes well, $10 billion worth of construction and one year of preparation will have finally started in orbit.