The pinnacle of Hubble’s vision

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Looking through the dust

Hubble’s infrared capabilities (bottom), compared to a visible-light image (top) of the same object in the Carina Nebula. Infrared light makes dusty regions of space fade away, revealing the stars within and behind them. In this case, astronomers have found a newborn star emitting jets (see chapter 5). Hubble’s infrared capabilities are limited. Its best infrared camera, Wide Field Camera 3, produces only 1-megapixel images, similar to those of a (very) cheap cell phone camera. Moreover, the 2.4-meter mirror cannot deliver images that are as sharp as those that JWST’s 6.5-meter mirror will produce. Stars look bigger and less well defined in Hubble’s infrared pictures compared to those in pictures it takes in visible light. JWST will transform all this. Producing infrared images with clarity similar to that of Hubble’s visible light images, JWST will provide a new perspective on star-forming regions like this one.


NASA, ESA, and the Hubble SM4 ERO Team


Unlike Hubble, JWST will not be launched into low-Earth orbit. Its delicate scientific instruments need to be kept cold for them to work properly, which means shielding the telescope from the light and heat of the Sun, Earth, and Moon.

To this end, the telescope will have a huge heat shield fittedhuge fitted heat shield, but this only works in a position where the Sun, Moon, and Earth all lie in the same direction and the gravitational interplay between the three is stable. There is only one place that fits that bill, a location is known as Lagrangian Point 2 (L2), and it lies 1.5 million kilometers from the Earth. The European Space Agency’s Herschel Space Observatory, a previous infrared space telescope that operated from 2009 to 2013, was also located there.
Because L2 is so far from Earth, around four times the distance of the Moon and further than any human has ever travelled, it will not be possible for astronauts to service JWST and its predicted lifespan of 5–10 years is shorter than Hubble’s. This will be worth it, however, because of the quality of infrared observations obtainable there.



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