The Hubble Space Telescope's been sending back spectacular images since April 1990. It's coming to the end of its life - it'll be replaced by the James Webb Space Telescope in 2014 if the best-laid plans o' mice and men don't gang aft agley - but that doesn't mean NASA's given up on upgrades. The Atlantis crew's up in space as we speak, tweaking, replacing, and fixing up various bits to ensure HST continues to contribute astonishing images and amazing science for years to come.
Today's Sunday Sensational Science is a salud to HST, and a gallery of the glorious images its provided us with these last 19 years.
Spacewalking. You think repairs on old equipment on land are tough, just try replacing parts that were never meant to be replaced while floating around in hostile space without gravity.Cujo's got a good description of what it's like:
On Earth, when an electronics tech yanks a circuit board out of a computer, gravity is holding his feet to the floor, or his butt to the chair, and his muscles can counteract the force being applied to his hands in reaction to the force he's applying to the board. In Earth orbit, there's no gravity. To get an idea what that's like, imagine you're underwater in a pool that's too deep to stand in. Push against the side of the pool with one hand. You'll spin around, because the force is being applied to your hand, and your body in turn.The astronauts on this mission deserve the title of supermechanics. Somebody give them capes. Underwear worn outside the clothes optional.
We all know HST's awesome, but a good majority of us probably haven't the faintest idea how it works. That's why there's websites like HowStuffWorks.com:After you've gotten to know your Hubble anatomy, take a moment to appreciate the last sight of one of the instruments the crew of the Atlantis is replacing:Like any telescope, the HST has a long tube that is open at one end to let in light. It has mirrors to gather and bring the light to a focus where its "eyes" are located. The HST has several types of "eyes" in the form of various instruments. Just as insects can see ultraviolet light or we humans can see visible light, Hubble must also be able to see the various types of light raining down from the heavens.
Specifically, Hubble is a Cassegrain reflector telescope. That just means that light enters the device through the opening and bounces off the primary mirror to a secondary mirror. The secondary mirror in turn reflects the light through a hole in the center of the primary mirror to a focal point behind the primary mirror. If you drew the path of the incoming light, it would like the letter "W," except with three downward humps instead of two....
The Hubble community bids farewell to the soon-to-be decommissioned Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope. In tribute to Hubble's longest-running optical camera, a planetary nebula has been imaged as WFPC2's final "pretty picture."
This planetary nebula is known as Kohoutek 4-55 (or K 4-55). It is one of a series of planetary nebulae that were named after their discoverer, Czech astronomer Lubos Kohoutek. A planetary nebula contains the outer layers of a red giant star that were expelled into interstellar space when the star was in the late stages of its life. Ultraviolet radiation emitted from the remaining hot core of the star ionizes the ejected gas shells, causing them to glow.
In the specific case of K 4-55, a bright inner ring is surrounded by a bipolar structure. The entire system is then surrounded by a faint red halo, seen in the emission by nitrogen gas. This multi-shell structure is fairly uncommon in planetary nebulae.
This Hubble image was taken by WFPC2 on May 4, 2009. The colors represent the makeup of the various emission clouds in the nebula: red represents nitrogen, green represents hydrogen, and blue represents oxygen. K 4-55 is nearly 4,600 light-years away in the constellation Cygnus.
The WFPC2 instrument, which was installed in 1993 to replace the original Wide Field/Planetary Camera, will be removed to make room for Wide Field Camera 3 during the upcoming Hubble Servicing Mission.
During the camera's amazing, nearly 16-year run, WFPC2 provided outstanding science and spectacular images of the cosmos. Some of its best-remembered images are of the Eagle Nebula pillars, Comet P/Shoemaker-Levy 9's impacts on Jupiter's atmosphere, and the 1995 Hubble Deep Field — the longest and deepest Hubble optical image of its time.
Incredible.
And Hubble's mission won't be over when the telescope stops peering into the far ends of the universe. As a recent discovery shows us, the data it's gathered will provide new insights for long decades to come:
Well, if you place a coronagraph over a distant star, you can see a whole plethora of much fainter objects orbiting that star. Well, someone was going through some old photos from 1998, and look at what they found using a coronagraph on a dusty young star, HR 8799, where they discovered planets in 2008:
So not only could we have found this planet 10 years earlier than we actually did, but by going back to the old data, we can learn a whole lot about this planet's orbit, and hence the mass of the star that it orbits. Is it not just outstanding that the Hubble Space Telescope, in addition to all the other things it does, functions as perhaps the most accurate stellar scale we've ever built?
How neat is this? We've got over 200 stars that have been imaged with a coronagraph by the Hubble Space Telescope, and now we can start looking for planets around them just by looking at the data we already have!
Hubble doesn't just provide us science, but works of art. The following images are a great reminder that science, especially seen through the eyes of Hubble, is beautiful:
3 comments:
To correct a common miscoception- There is loads of gravity in orbit.
Gravity follows the squared rule of diminishing. So if G at x distance = 100, at 2x it is 25- the same G is spread amoung 4 times the area- ie 2^2 - G=25. At 3x it g=11.11 [100/(3^2)] and so on.
The distance to orbit is just a few hundred miles, a fraction of the 7000 miles from the earth's centre of gravity. Thus 1.03x for orbit of 250 miles. Given at an orbital distance of 7000 miles, G would still be 2.4ms^1, rather than the 9.81ms^2 you are currently experiencing (double the distance, 1/4 the effect), at 250 miles orbit is still 9.1ms^2.
What actually happens in orbit is that everything is falling at the same rate, thus you appear weightless. The reason every thing keeps falling is that as you descend the Earth curves away from you as fast as you fall.
There is gravity, it is just that every thing is in freefall.
That's true, lasthussar. But, for all practical purposes, gravity's not there. That's what creates an orbit. As I suspect most writers do on this subject, I chose to keep the terminology simple.
BTW, my later reference to using pools to train astronauts for tasks in weightlessness is an instructive one here - a body's buoyancy tends to counter the force of gravity.
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