Twenty years ago today, the space shuttle Discovery carried a brand new telescope aloft into space, to be settled into orbit the following day. And this was a significant delay over plans – the Challenger accident had occurred only eight months before the tentative launch date of Hubble in October 1986, and set its schedule (as well as everything else) back several years.
The telescope was (and still is) named after Edwin Hubble, the astronomer who determined that the blob we knew as Andromeda was not within our own galaxy, but was a whole other galaxy in itself, and with that discovery he expanded the size of the universe (or what we believed it to be at that time, anyway) by many thousands of times.
Naming the telescope after him was a highly appropriate tribute, but only after a bad false start. A horrifying fact emerged immediately after the first images were transmitted back to Earth: the 2.4 meter diameter primary mirror had been ground incorrectly and was both slightly unfocused and astigmatic. Orbiting in space was a multi-billion-dollar screwup. Image processing programmers created algorithms to correct the images digitally, but this was a workaround and didn’t begin to approach the detail and resolution of the original design. Three and a half years later, the first servicing mission to Hubble replaced both a mirror and a camera and corrected that focusing issue in much the same manner that corrective lenses can assist human vision. It was a phenomenally creative fix for what could have been a disastrous mistake.
And in the years since, Hubble has been responsible for literally hundreds of the most captivating images from space (both images here link directly to much bigger versions from the source,) and has expanded our knowledge of the universe by an immeasurable, but vast, amount. Hubble produced the first measurements to indicate that the expansion of the universe was actually accelerating, something that hadn’t been considered before then, and eventually leading to the concept of dark energy (because something has to be causing the acceleration.) And to even make that observation, it first had to pin down the measuring stick more accurately: the spectral shift from distant stars. This alone made our distance measurements far more accurate for all telescopes.
But perhaps the most stunning, and humbling, of images is the Ultra Deep Field photos. Aimed at a (until then) perfectly empty section of space, Hubble took cumulative exposures totaling over ten days and revealed an unreal mass of incredibly distant galaxies, each with millions of stars. And since light takes its own sweet time to get here, what we see is what those galaxies looked like billions of years ago – most have changed or even vanished by now, and all are much, much farther away than when the light that created our images started its journey in this direction. Even that is pretty awe-inspiring: those little photons emitted by countless stars traveled uninterrupted for billions of years and quintillions of kilometers to pass through Hubble’s little aperture and end their journey dumping a minuscule amount of energy into electrons in the cameras’ sensors.
It almost seems rude to halt that trip in our little telescope, but not half as ignominious as the photons who petered out against some little asteroid or dust speck. Even worse, some of those photons might just have produced a smidgen of energy in a satellite’s solar array, boosting the cellphone signal of a photo of someone’s penis…
Like all satellites and spacecraft, Hubble will eventually cease operation, and this is expected sometime within the next few years, whereupon it will be allowed to deorbit and reenter our atmosphere in a safe trajectory – safe, that is, for human population, but rather hard on the telescope itself, which is expected to become little burning chunks. It’ll be a shame, but that emotion is evidence of how successful it was after its shaky start. And it has served its purpose, but we are now moving on to other observations. Hubble is limited to the spectrum of electromagnetic radiation we call “visible light” (and just a little beyond that,) but there’s a lot more to see in other wavelengths, and more scopes to probe them: Spitzer, Chandra, the upcoming Webb, and others yet to come. The pursuit of knowledge moves on and leaves most of its tools behind – that’s how it goes.