James Webb Space Telescope: Hubble’s Successor in Space Exploration

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Full Scale Model of James Webb Space Telescope on Display at Northrop Grumman – Photo Courtesy of NASA

A new space telescope is in development and construction by Northrop Grumman, called the James Webb Space Telescope (JWST). This new telescope is not a replacement for the Hubble, it is its successor. Unlike Hubble’s primary optical and ultraviolet light observations of space with some infrared ability, the JWST will use infrared as its primary method of observation. With this capability, this next generation telescope will have the capability to observe the first galaxies formed after the Big Bang.

Scientific Objective

The James Webb Space Telescope’s primary scientific objective is to examine every phase of the universe’s history, including the origin of our own solar system. This objective is spread within four main themes (National Aeronautics and Space Administration).

 

These themes are:

End of the Dark Ages: First Light and Reionization – discovery of  how the universe transformed from 400 million years of darkness after the Big Bang into a vast collection of stars and galaxies. To accomplish this task the JWST will use its ultra-deep near-infrared telescope to study the universe. Data collected from this investigation will help scientists determine when, how, and from what sources reionization of light was caused after the initial period of darkness.

Assembly of Galaxies – this theme will initially focus on how the first galaxies were formed, followed by an investigation of how galaxies evolved into the varied shapes and sizes they are today. Knowledge of the forces involved in the forming of galaxies is important because new galaxies are still evolving today. Some are colliding to form new galaxies;  for example the Andromeda galaxy is on a collision course with our Milky Way galaxy billions of years from now.

The Birth of Stars and Protoplanetary Systems – the JWST’s infrared telescope is designed to peer into dense stellar dust clouds, known as star nurseries, to observe how new stars are formed. This investigation will also focus on how planets are formed from these dust clouds to create a solar system around a young star.

Closeup View of a Model of JWST’s Primary Mirror – Photo Courtesy of NASA

Planetary Systems and the Origins of Life – scientists will use data collected from all these investigations to study how life formed on our earth. Their study will focus on the chemical and physical history of  young stars and the formation of their planets. The findings in this study may also answer questions scientists have regarding how planets reach their final orbit and how large planets affect the formation and orbit of smaller planets in a solar system.

Hubble and Webb Telescopes: A Comparison

A comparison is necessary to understand why the JWST is considered a successor and not just a replacement. The James Webb Space telescope is currently scheduled for a 2018 launch, while the expected end of service life for the Hubble Space Telescope is 2014. This will leave at least a four year gap in space telescope exploration of the universe. The following are selected comparison points of these two telescopes.

Size and Shape

  • HST – 43.5 ft (13.2 m) long by 14ft (4.2 m) diameter cylinder, about the size of an 18-wheeler. Its weight is 24,500 lbs (11,110 kg).
  • JWST – 69.5 ft (22 m) long by 46.5 ft (12 m) wide or about the length of a Boeing 737 airplane. To protect the Webb from the sun, it will hide behind a sun shield that is as big as tennis court. Its projected weight is 14,330 lbs (6,500 kg).

Orbit

  • HST – low earth orbit of 342 miles (570 km) and it circles the earth every 97 minutes.
  • JWST – geo-synchronized (Earth-Sun Lagrange 2) fixed point 937,500 miles (1.5 million km) from earth. Its planned location means it will orbit the sun once a year, just like earth.

One of the 18 Gold Covered Beryllium Segments of JWST’s Primary Mirror – Photo Courtesy of NASA

Primary Mirror Size

  • HST – 7.87 ft (2.4 m) in diameter.
  • JWST – 21.33 ft (6.5 m) in diameter consisting of 18 beryllium segments.

Service Life

  • HST– launched in 1990, initially had a designed service life of 15 years. It received five servicing mission updates using the space shuttle, the last in 2009.  These updates improved its capabilities and extended its life to 2014 (Space Telescope Science Institute).
  • JWST – designed service life is five years, although it will have a desired service life of ten years. To meet desired requirements, the telescope will carry enough maneuvering propellant for a ten year mission to exploit its full scientific potential (Northrop Grumman).

Serviceability

  • HST – accomplished by Space Shuttle crews, owing to its low earth orbit. The end of the shuttle program means there are no more plans to service the Hubble.
  • JWST – not designed for service, because of its L2 orbit location.

Who is James Webb?

The James Webb Space Telescope is named for National Aeronautics and Space Administration’s (NASA) second administrator. James Webb’s term (1961-1968) was a period of rapid growth for NASA that witnessed the successful completion of the Mercury and Gemini manned spaceflight programs, and the early years of Apollo. Many successful space science missions were also developed or flown during Webb’s tenure.

This next generation project is a joint collaboration of NASA, European Space Agency (ESA), and Canadian Space Agency. The ESA will use an Ariane 5 rocket to fly the JWST into space. Because of this partnership, many in the world’s scientific community will work jointly to examine the universe’s history.

Sources

Space Telescope Science Institute. The Telescope. Accessed July 22, 2011.

Grumman, N. James Web Space Telescope (JWST). Accessed July 22, 2011.

Gardner, J. The James Webb Space Telescope (2006). Space Science Reviews 123:485-606. Accessed July 22, 2011.

National Aeronautics and Space Administration. The James Webb Space Telescope. Accessed July 22, 2011.

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