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From an inspiration POV, I'm fairly sure that the main reason the HST had a recent refit instead of being junked was because it's been such an impressive source of pretty pictures. Some of the images have become iconic and instantly recognisable.

But ask the hypothetical average person to name one piece of astrophysics the HST has influenced, and you'll get a blank look.

The great thing about these amateur images is that they look Hubble-ish but someone took them from their back garden. It's not totally impossible that someone will see them, wonder how they were done, and start finding out about telescopes and CCDs. From there it's not a huge step to Real Science - if only because you need to know what the different colour filters actually filter so you can use them properly.

You can get good astrophotographic images for a lot less than 20k, and if you happen to grow up with a back garden telescope and are curious, it's not a trivial resource to get you started in a professional direction.

The problem with Malin's images is that they're not accessible in the same way. If you need to travel to Mauna Kea, Las Palmas or some other Giant Scope Home to take your shots, or (more likely) book time on same remotely, you've eliminated that experience of participation for most people.

What would be immensely cool - and almost certainly won't happen, because it would be too damn expensive - would be for Hubble to become a public access telescope after it's decommissioned. I'm not sure how much STSCI costs to run, but it's not completely unlikely that there are a few million amateurs worldwide who'd be willing to pay £100 a year for a chance to get some CCD time on Hubble.

by ThatBritGuy (thatbritguy (at) googlemail.com) on Sat Jan 23rd, 2010 at 08:05:31 PM EST
[ Parent ]
I'm fairly sure that the main reason the HST had a recent refit instead of being junked was because it's been such an impressive source of pretty pictures.

I'm no NASA insider to tell the real reasons, but it had something to do with a change at NASA's helm and the fact that HST's successor (the James Webb Telescope) is still years away.

This is not to dismiss the power of the HST pretty pictures, but I don't think anyone in this debate is challenging that. (As I wrote, STScI has its own department for making the PR pretty pictures, and they did a fine job to make people forget the error made in polishing of the main mirror, and the massive cost overruns needed for corrective optics.)

The great thing about these amateur images is that they look Hubble-ish but someone took them from their back garden.

More David Malin-ish than Hubble-ish :-)

What would be immensely cool - and almost certainly won't happen, because it would be too damn expensive - would be for Hubble to become a public access telescope after it's decommissioned.

If it could go on, it wouldn't be decommissioned :-) HST servicing isn't just about the replacement of instruments with improved ones, you have to replace solar cells and positioning gyroscopes. Once NASA stops funding for servicing missions, HST is poised to be dead in a few years, and there is a lot of professional work only it can do until then. (The JWT wll come in what, 2014 at the earliest?) And it's too damn big to be allowed to fall down on its own, so there has to be a controlled crash eventually.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Jan 24th, 2010 at 03:42:07 AM EST
[ Parent ]
James Webb Space Telescope - Wikipedia
The observatory is due to be launched no earlier than June 2014 and is currently scheduled to be launched by an Ariane 5 from Guiana Space Centre Kourou, French Guiana, into an L2 orbit with a launch mass of approximately 6.2 tons. After a commissioning period of approximately six months, the observatory will begin the science mission, which is expected to last a minimum of five years.

(I don't know why I left "Space" out of its name twice...)

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Jan 24th, 2010 at 03:43:52 AM EST
[ Parent ]
I have a lay person's question - the wiki states:

James Webb Space Telescope - Wikipedia, the free encyclopedia

The JWST will not be a complete successor, because it will not be sensitive to all of the light wavelengths that Hubble can see. The main scientific goal is to observe the most distant objects in the universe, those beyond the reach of either ground based instruments or the Hubble.

So, how is it possible that the JWST, which apparently is less sensitive to all light wavelengths than Hubble, should be able to observe objects that where beyond what Hubble could perceive?

by Fran on Sun Jan 24th, 2010 at 04:02:24 AM EST
[ Parent ]
Good layman question!

The JWST will be less sensitive to more bluish wavelengths than the HST, however, it will be much more sensitive to reddish and infrared wavelengths. Now, the light of the most distant objects is significantly redshifted. So, while all galaxies are the brightest in or near the band of visible light, the light of the furthest-away galaxies was released so long ago and redshifted so much until it gets into our telescopes that these galaxies can be best detected in the near infrared.

As for redshift: this is usually explained for laymen in terms of the Doppler effect (e.g. the lower pitch of the noise of receding trains), but for cosmological redshift, that is less helpful. That the Universe expands should be understood as space itself expanding -- thus, a wave of light travelling across it is stretched, too. That means that the wavelength of the wave of light is increased. Red light has longer wavelength than blue light, hence it's called redshift.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Jan 24th, 2010 at 06:15:01 AM EST
[ Parent ]
Thanks DoDo, makes sense to me. :-)
by Fran on Sun Jan 24th, 2010 at 11:55:02 AM EST
[ Parent ]
Illustrating what I said above, from Open University, here is the Sun's spectrum:

...and a typical spiral galaxy spectrum:

A redshift of z=9 (which is in the middle of where the JWST wants to look) means that wavelengths expand 10x, that is by an order of magnitude, or one tick mark to the right on the horizontal axis of the above diagram.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Jan 24th, 2010 at 06:24:39 AM EST
[ Parent ]
BTW, if anyone is curious what's the possible maximum in redshift: 1089, that's the redshift of the Cosmic Microwave Background, which was a yellowish light when released (the thermal radiation of non-transparent plasma turned transparent gas), but the Universe expanded 1090x since then. However, it took some time from there for the first stars to light up, so the most distant galaxies observable even in theory will have redshifts in the dozens at most.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jan 24th, 2010 at 06:32:43 AM EST
[ Parent ]

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