James Webb Space Telescope – The Instrument
Uncover how “Discovery” contributes to scientific and spiritual growth through a brief video presentation by Dr. Tim Knudson, professor of physics and astronomy at Southern Virginia University (SVU). Additionally, watch a video featuring the testimony of Elder Maxwell, a member of the Quorum of the Twelve Apostles from 1981 to his passing in 2004, and read remarkable details about how photography from the James Webb Space Telescope compares to the Hubble Space Telescope.
The “discovery transcript” button below features a text transcript and a six-and-a-half-minute audio recording specifiically for the exhibit. In this narration, Bruce Lindsay highlights space discoveries uncovered with the James Webb Space Telescope.
Perspective Presentation
Enjoy a brief video presentation by Dr. Tim Knudson, professor of physics and astronomy at Southern Virginia University (SVU) as he helps us understand the size of our Milky Way galaxy and where James Webb Space Telescope images featured in the exhibit are in relation to it.
Elder Maxwell: Special Witness of Jesus Christ
Elder Maxwell, a member of the Quorum of the Twelve Apostles from 1981 to his passing in 2004, testifies of the love Heavenly Father has for all of His children while discussing the limitless creations of the universe.
This video was shown with permission during the Worlds Without Number: God’s Infinite Creation exhibit in the Washington DC Temple Visitors’ Center.
James Webb Space Telescope (JWST)
The James Webb Space Telescope (JWST) is the largest space telescope ever built. It was launched on Dec 25, 2021. The primary mirror consists of 18 hexagonal mirror segments that combine to form one large mirror 6.5 meters (~21 ft) in diameter. Each mirror segment is coated with gold to improve reflectivity in the infrared. The 5-layer sunshield is 22 meters by 12 meters, about the size of a tennis court. As the telescope orbits the Sun the sunshield remains between the Sun and the telescope to protect the sensitive instruments.
On the observing side, light bounces off the primary mirror onto the secondary mirror and then down the black tube where it enters one of four instruments. It is the different instruments or cameras that take the pictures you see in this display. Each instrument is equipped with a range of filters that only let light through at certain wavelengths allowing us to combine several pictures at different wavelengths to create the images you see displayed around you.
On the Sun-facing side an antenna relays the images back to the Earth and is used to communicate with the telescope. A small solar array provides a source of power. The star trackers are used to make small corrections that hold the telescope steady while observing. Finally the steering and control are used to control and rotate the telescope as it points to different areas of the sky.
Telescopes can be thought of as light gathering buckets. The larger the primary mirror the more light you can collect from a distant object. The diameter of the JWST primary mirror is 6.5 meters. The diameter of HST’s primary mirror is 2.4 meters. For comparison, the average woman is about 1.6 meters in height, or about 2/3 of the length of the primary mirror of HST and 1⁄4 of the length of the primary mirror for JWST. The amount of light that can be collected from a distant object in space is a function of the total area of the mirror. The effective area of JWST’s mirror is 25 m2, while the effective area of the HST mirror is only 4.5 m2. That means JWST can collect five times more light than HST can, allowing it to see objects that are five times fainter and farther away.
The two telescopes also differ in the wavelengths of light where they operate. The instruments on HST are sensitive to light in the near-ultraviolet, the visible spectrum and the near-infrared. In contrast, the instruments on JWST only operate at near- and mid-infrared wavelengths of light. The HST pictures are often more true to what your eye would see, while with JWST we have to assign different colors to different infrared wavelengths in order to create a color image. A general rule of thumb is to assign bluer colors to shorter wavelengths of infrared light and redder colors to longer wavelengths of infrared light. The different JWST images you see displayed around you are not true color but an enhancement of different infrared wavelengths, colored in such a way that you are able to see what these objects would look like if your eye was sensitive to infrared light.
Hubble Space Telescope (HST)
On April 24, 1990, the space shuttle Discovery launched into space carrying the Hubble Space Telescope (HST) securely in its bay. The telescope is a little larger than a school bus. It is 13.2 meters long and 4.3 meters at its widest point. The primary mirror is only 2.4 meters in size, which is small compared to most research telescopes here on Earth. But because HST is in space it doesn’t have to worry about the loss of light from distant objects due to Earth’s atmosphere. Thus, when it launched, Hubble produced some of the highest resolution images ever obtained of galaxies and nebulae.
Because HST is in orbit around the Earth NASA was able to use the space shuttle to send five servicing missions to upgrade the instruments and make much needed repairs to the telescope. This has allowed the telescope to operate continuously for almost 35 years. The Fine Guidance Sensors lock onto stars and help stabilize the telescope when observing so that it does not roll. There is an aperture door that can be closed to protect the telescope and sensitive instruments when the telescope needs to move within 20 degrees of the Sun. Otherwise the door is open, allowing light to travel down the tube where it hits the primary mirror and then bounces back up to the secondary mirror which directs the light through a hole in the primary mirror and down into the instruments which are housed behind the primary mirror. The telescope also has solar panels to provide power and antennas that allow it to communicate with scientists on the ground. Using the communication antennas scientists in Maryland are able to tell the telescope where to point and what images to take. They then download the data and make it available to scientists and the general public to work with.
Face-On Spiral Galaxy - Hubble vs. Webb Comparison
This picture of the spiral galaxy NGC 1566 is split diagonally, with the JWST image on the bottom right and the Hubble image on the upper left.
The Hubble image on the upper left is a composite of images taken in the ultraviolet and optical wavelengths of light, where your eye operates. You can clearly see the bright blue stars in the arms of the spiral galaxy and the dark dust lanes blocking the background starlight from the galaxy.
The JWST image on the bottom right is taken at near- and mid-infrared wavelengths where the colder dust is glowing. You see the spidery, filament structure of the dust lanes and only starlight from the coldest red supergiant stars. Normal stars emit only a small fraction of their light in the mid-infrared, so you don’t see the same glow of starlight in the JWST image that you see in the Hubble image.
This galaxy is 60 million light-years away, in the Dorado Group of galaxies.
Pillars of Creation - Hubble vs. Webb Comparison
The Pillars of Creation are three long columns of interstellar gas and dust in the Eagle nebula, each a few light-years in length. Young stars are currently forming in the tendrils of gas and dust seen in this picture and newly formed young stars have blown away the surrounding gas and dust to reveal the pillars.
On the left is the Hubble image taken at optical wavelengths of light and the dust marks the location of the pillars by blocking out the background starlight.
But in the JWST picture on the right, the infrared light passes through the lower density regions of the dust, showing just how tenuous this structure really is. In the infrared the apparently thick pillars are seen as wispy columns of dust and gas silhouetted against a background of thousands of stars that are suddenly visible because the infrared light they emit easily passes through the dust.
The Eagle Nebula is 5700 light-years away and is an area of active star formation in our galaxy.
Crab Nebula - Hubble vs. Webb Comparison
The Crab Nebula is about 11 light years in width and is the remains of a massive star that exploded in 1054 AD. The nebula was produced when the shock wave that ripped apart the star pushed the stellar material out in all directions. The explosion created the beautiful filament structure you see of gas and dust.
In the JWST picture on the right you can actually see white ribbons of circular radiation coming from the pulsar (neutron star) at the center of the nebula. The Hubble picture on the left was taken in optical wavelengths of light where your eye is sensitive. The orange filaments in the Hubble image are the tattered remains of hydrogen gas from the star. The blue-green glow comes from radiation emitted by electrons spinning around the pulsar’s magnetic field lines. The JWST image on the right is a composite of near- and mid-infrared wavelengths. In JWST, the gas filaments are also shown in red and orange. In the infrared you can see dust grains (yellow-white and green) and the synchrotron emission produced by the electrons spiraling the magnetic field lines correspond to the smoke-like material throughout the interior.
The crab nebula is in our galaxy, and is 6500 light-years away in the constellation of Taurus the bull.
Learn More About the Narrator
Bruce Lindsay
Bruce Lindsay was in the second grade when he wrote his first Christmas story for The Plymouth School News. His interest in writing led to a career in journalism as an Emmy Award-winning reporter and newscaster. Decades of presenting current events to large television audiences never brought him more satisfaction than reading Christmas stories aloud to his children and grandchildren. Bruce received an MBA from the University of Utah. His favorite places to write are on a ship or on a train or in the shade on his back porch.
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