The Future of Space Astronomy
The Hubble Space Telescope has made amazing astronomical discoveries for twenty-three years. It still has a good number of years left, but without the Space Shuttle, servicing missions are no longer possible. The natural question is "what's next?". Astronomers have been planning for the next generation space telescope since a few years after Hubble's launch. We have mapped out the important questions that the current ground and space telescopes can't address. We have envisioned the new capabilities, technology, hardware, and software required find those answers. Those ambitious goals will be realized in the James Webb Space Telescope.
For those of us born in the Apollo era, it is striking to recognize that those graduating college were born after the launch of Hubble. They have never known a world without its extraordinary images and discoveries. Also, as the most well known telescope, some assume Hubble can do most anything astronomers require. Part of my point in doing this episode is to remind everyone that Hubble plays its role within a much larger astronomy research community. It may be NASA's flagship space telescope, but the mysteries of the universe are much grander than one mission can fully explore.
The visualization of flying through the Hubble Ultra Deep Field has one major caveat: the distances have been greatly compressed. If done scientifically accurately, the galaxies would be much, much farther apart. It would take much, much longer to fly-through or the camera would have to move at a speed such that the galaxies would whizz past. To allow for a more enjoyable and informative traverse, we compressed the distances by a factor of a few hundred.
The first slide where I show Hubble and Spitzer side-by-side is definitely not to scale. Hubble is about 40 feet long and its mirror is about 8 feet in diameter. Spitzer is considerably smaller, at about 15 feet long with a mirror diamter of less than 3 feet. A later slide, which compares these to JWST, provides the proper scale. And while I'm decrying scale issues, note that the L2 diagram is also definitely not to scale.
Although JWST's mirror is larger than Hubble's, its resolution will be similar. Generally, the larger the mirror, the better the resolution. However, that rule assumes observations at the same wavelength of light. For JWST's longer wavelength infrared observations, the larger mirror is needed just to achieve similar resolution to what Hubble gets for its shorter wavelength visible light observations. Resolution depends on both telescope size and the wavelength of light observed.