How Big is the James Webb Telescope?

James Webb Telescope

How Big is the James Webb Telescope?

The James Webb Space Telescope is a phenomenal achievement of 21st-century space-related science and technology. This space telescope builds on and extends the work of the Hubble Space Telescope, traveling further and longer into space to capture astonishing images. Achieving its amazing capabilities is only possible because the James Webb Space Telescope is the world’s largest. In this article, we ask how big the James Webb Telescope is, as well as share interesting facts about the most recent of NASA’s space telescopes. 

Just How Big Is the James Webb Telescope?

So, just how big is the James Webb Space Telescope (JWST)? Overall, it is 69.5 x 45.5 feet (22 x 12 meters), which is the size of a small plane or blue whale! The aperture alone is over 21 feet (6.5 meters) wide. The sun shield that protects the telescope from overheating is also large. At 69.5 x 46.5 feet (21.197 x 14.162 meters), the JWST sun shield is as large as a tennis court all by itself. Of course this telescope is heavy too, at over 13,668 pounds (6,200 kg), it is around the same as a heavy goods vehicle (HGV).

James Webb Telescope
The James Webb Space Telescope is the largest telescope currently in orbit.

How Does the James Webb Compare in Size to Other Space Telescopes?

The JWST is the largest of the 90 space telescopes that NASA and the European Space Agency (ESA) have put into orbit since 1970. 

Its size clearly eclipses the 26 space telescopes that are currently active, including:

  • The Hubble Space Telescope (NASA) –  43.5 x 14 feet (13.2 x 4.2 meters)
  • The Gaia Space Observatory (ESA) – 15.1 x 7.5 feet (4.6 x 2.3 meters)
  • The Interstellar Boundary Explorer (NASA) – 23 x 27 inches (58 x 95 cm)

Why Is the James Webb Space Telescope So big?

The JWST has been built to venture further and see deeper into space than any of its predecessors. This orbiting observatory has the most advanced wavelength sensitivity, spanning the electromagnetic spectrum while picking up very very old light that has traveled near infinite distances.

In fact, the massive size is key to its heightened sensitivity. Its large compound mirror maximizes the amount of light that can be collected and reflected toward its receiver. As a result, this improved sensitivity has made the JWST capable of capturing distance space images like stars and galaxies with breathtaking resolution. 

The JWST also carries advanced optical-ultraviolet instrumentation developed by NASA to acquire data that can expand the existing knowledge of astronomy and cosmology. The giant sun shield is necessary to keep the JWST ultra cold so that it isn’t blinded by picking up the infrared (heat) energy it radiates. Because of this unique design, The JWST can image space objects that are too distant, faint, or old for its predecessor, the Hubble Space Telescope

Everything You Need to Know About the Largest Telescope in Space

The JWST is an infrared space observatory that is equipped with extremely advanced instruments for high sensitivity, high-resolution space imaging including an infrared camera (NIRCam), infrared Spectrograph (NIRSpec), mid-infrared instruments (MIRI), and an infrared imager and slitless spectrograph (FGS/NIRISS).

Owing to his important role in promoting NASA’s role in scientific research, the telescope is named after James E. Webb, NASA’s second administrator.

The development of the JWST was led by NASA at the NASA Goddard Space Flight Center (GSFC) in Maryland in partnership with:

  • The Canadian Space Agency (CSA)
  • The European Space Agency (ESA) 

There were also contributions from scientists and engineers from other countries, including The United Kingdom, Greece, Czech Republic, and Finland. 

The JWST was launched on an Ariane 5 ECA rocket from Kourou in French Guiana on the 25th of December 2021. It is currently orbiting at Lagrange L2 point, more than 1.5 million km from earth, the furthest distance of any space telescope. At this time, it is operated by the Space Telescope Science Institute at Johns Hopkins University. 

Landmark innovations of this giant space telescope include its lightweight optics, microshutters, and massive deployable sun shield that works with cryogenic actuators to keep the telescope cold. 

History of the James Webb Space Telescope

Before its launch in 2021, plans for a successor to the Hubble Space Telescope (HST) had been taking shape for more than 30 years. To this end, the HST and Beyond Committee was formed in 1994. This group was convened to investigate possible missions and programs for the 21st century. They focused on the potential for the development of an extremely large and cold infrared telescope with enhanced sensitivity. 

This idea was embraced by NASA, which began planning the construction of an actively cooled Next Generation Space Telescope once the HST mission was extended to 2005.  In 1999, NASA initiated the necessary cost and technical requirement studies for the telescope, selecting Lockheed Martin together with TRW to come up with design concepts.

Cost-cutting efforts at NASA in the late 1990s and early 2000s accordingly led to the decision to create the JWST’s compound mirror. This honeycomb design was subsequently implemented to reduce the mass density of the telescope’s mirror. Rather than using glass, the development team opted for beryllium as the reflective material. 

Then, the Next Generation Space Telescope was renamed the James Webb Space Telescope in 2002. A year later, TRW was awarded the prime contract for building the JWST, worth over $800 million.

James Webb Telescope
This illustration of the Webb telescope shows the layered sun shield and honeycomb design of the segmented mirror.

James Web Space Telescope Mission Goals

The JWST’s initial mission duration is projected to be 10 years, though the telescope may remain functional for as long as 20 years. The mission goals devised by NASA include:

  • Searching for the earliest galaxies and oldest luminous objects
  • Increase understanding of the formation of galaxies
  • Increase understanding of the formation of stars and planetary systems
  • Study of the physical and chemical composition of planetary systems

Specifications of the James Webb Telescope 

To illustrate the scale and abilities of space’s largest optical telescope, here are the specifications from NASA:

Total Weight13,668.66 pounds (6,200 kilograms)
Dimensions of the Primary 5-Layer Sun Shield69.5 x 46.5 feet (21.197 x 14.162 meters)
Optical ConfigurationThree-mirror anastigmat
Primary Mirror Diameter21.3 feet (6.1 meters)
Primary Mirror Aperture25 square meters
Primary Mirror MaterialGold-plated beryllium
Primary Mirror Weight1,554.26 pounds (705 kilograms)
Number of Primary Mirror Segments18
Focal Length431.1 feet (131.4 meters)
Wavelength Coverage0.6 to 28.5 micrometers (near ultraviolet to infrared light)
Resolution of Images0.1 arcseconds
Operating Temperature-370 °F (-223 °C )
Cruising Speed (Relative to Earth)1,390.47 kilometers per hour (864 MPH)
Power2 kW (onboard solar array)

First Images from the JWST

At last, the first transmitted images from the James Webb Space Telescope were released by NASA on the 12th of July 2022. The amazing color images and spectra displaying the full capabilities of this mega-telescope were broadcast live from the Goddard Space Flight Center in Maryland.

Breathtaking images chosen by representatives from NASA, the ESA, and CSA included Stephan’s Quintet, the Carina Nebula, and the Southern Ring Nebula. The unique resolution of these images demonstrated the power of this telescope, as well as its infrared technology.

If you would like to see these amazing James Webb Space Telescope images, then read our article: See 30 Gorgeous James Webb Telescope Images up Close.

James Webb Telescope
The gigantic image of Stephan’s Quintet was constructed from almost 1,000 separate image files and covers 1/5 the diameter of the moon.

Could There Be a Bigger Telescope Than the James Webb?

The JWST may soon have to make way for Chile’s Giant Magellan Telescope (GMT). The GMT is currently in development but is intended to be the largest and most powerful telescope ever. It isn’t a space telescope, but its dimensions are so large that it will be at least four times more powerful than the JWST and 200 times more powerful than all other telescopes in existence. 

Given these points, this terrestrial telescope will occupy a 12-story observatory located in the Atacama Desert of Chile. Its proposed dimensions include:

  • A height of 127 feet (39m)
  • Weight of 4,629,708 (2,100 tons) 
  • A 213-foot (65m) long hull
  • A compound mirror comprised of seven secondary mirrors with adaptive capabilities 

According to the Giant Magellan Telescope Organization (GMTO) developing the telescope, construction is expected to begin in the late 2020s.

NASA to Launch a Telescope Bigger Than the JWST Within the Decade

NASA and the ESA have teamed up again to develop another next-generation space telescope that may also be larger than the JWST. It is called the Nancy Grace Roman Space Telescope, accordingly named after the late American astronomer Nancy Roman. Roma was named the “mother of Hubble” due to her contributions to the development of the Hubble telescope. 

The Nancy Grace Roman Space telescope is expected to be larger than the JWST and capable of capturing massive panoramas. These images will aid the in-depth statistical study of the universe, not to mention satisfying many important questions in astrophysics. The telescope is still in development, but could be launched as early as 2027.

Rounding Up 

Above all, the size, scope, and capabilities of the James Webb Telescope is far beyond current astronomical technology. The images that this telescope has produced are not only remarkable, but also provide invaluable insight into the nature of our universe.

Frequently Asked Questions

What is an optical telescope?

Optical telescopes acquire and focus the visible portion of the electromagnetic spectrum (light) to generate images that can be viewed. The resolution of optical telescopes is determined by the size of their aperture and the lens that focuses light.

What is an infrared telescope?

Infrared telescopes acquire the infrared energy that is radiated from any celestial body that has a temperature above zero. Infrared energy is part of the electromagnetic spectrum along with visible light.

What is an arcsecond?

An arcsecond, arc second, or second of arc is a measure of angles that is equivalent to 1/3600 of a degree. 

What is the L2 point?

L2 is the second Lagrangian point, a deep-space location that is more than 1.5 million kilometers from Earth and has unique gravitational properties. It is named after Joseph Louis Lagrange, a mathematician.

What is beryllium?

Beryllium is an alkaline earth metal that has properties that include thermal stability, flexural rigidity, transparency, and low density (due to a low atomic number). It has wide-ranging aerospace and defense applications including the fabrication of large honeycomb mirrors.

What is a honeycomb mirror?

Honeycomb mirrors are extremely large mirrors that are used in astronomical applications. These compound mirrors are used as the primary mirror in reflecting telescopes. The honeycomb design is favored because it reduces the overall weight of the telescope, saves cost, and articulation in the mirrors can aid in focusing electromagnetic energy.

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