Jump to content

The James Webb Space Telescope and stuff


Streetwind
 Share

Recommended Posts

6 hours ago, NFUN said:

Challenge accepted

Hehe :-) The outcome would be interesting, given that image resolution is not really an obvious, trivial thing.

Hint: it is not the optical resolution of the telescope for a given wavelength/focal length/aperture aka diffraction limit. And it is certainly not 'better' than that.

Edit, but I think @sevenperforce's main argument was that JWST could take much better defined images with its instrumentation. The good thing is, also because of the exceptional delivery by the Ariane, the observatory has a much longer lifetime to do things(tm). I'm glad :-)

 

Edited by Pixophir
Link to comment
Share on other sites

Theoretically hypothetically and ignoring all counter indications, such an arrangement would allow for a ludicrous angular resolution. Other things of a class "super telescope" could be for instance a lake of a reflective fluid in a crater of the moon.

But with current tech it is imaginable, but impractical. An interferometer can fake the resolution of a huge aperture, but it doesn't have more light collecting capabilities than the surface of the participating telescopes. The amount of data can be huge. I remember one of the guys of the Event Horizon Telescope (EHT) saying something like "nothing beats the bandwidth of a jet full of hard disks", and papers that were written about how to synchronize (that means synchronize time differences in a sub-frequency resolution of the observed wavelengths) the data gathered by the different sites of the VLB.

Also, the semi-stable L-points tend to attract material, stuff that comes, stays a while, and goes. There is a high chance of collisions there.

An artificial satellite must do station keeping. So their lifetime is limited by fuel, which certainly has financial implications.

There's certainly much more to think about.

tl,dr: one day, maybe, speculatively, after a space maid has cleaned up ... oh wait, vacuum in a vacuum ? Hmm ... :-)

Edit: I mean, it took 30 years from earliest planning to launch to make one(1) JWST. Certainly the knowledge gained could partially be re-used and adapted. And what was gathered when doing the also multi-decadal and still developing EHT as a world spanning VLB could help judge the feasibility of such a project. But I would expect "Interferometry in the Lagrange Points" to be a multi-generation project, still.

Edited by Pixophir
Link to comment
Share on other sites

If send a cloud of autonomous telescopes to the 550 AU distance, every one of them can be photographing its dedicated spot in hi-res, and all and once they would be an ultra-large intereferometer array.

We could watch the alien sitcoms.

Finally, the astronomy would turn into something useful for everyone, not just a game for nerds.

Link to comment
Share on other sites

1 hour ago, kerbiloid said:

Finally, the astronomy would turn into something useful for everyone,

yes, but the subscription costs are absurd.

I mean, who has Tilaxian Simars lying around?  Much less 30/month?

Link to comment
Share on other sites

"Candidate 1" is a potential planet around Alpha Centuari A in its habitable zone, that's between the size of Neptune and Saturn. I didn't know they were looking to get time scheduled on Webb to try and confirm it until I saw this article (though I wondered if they were going to). It didn't help that they made no mention of Alpha Centuari in the information page, just "closest stellar neighbor"

https://www.inverse.com/science/alpha-centauri-planets-jwst

https://www.stsci.edu/jwst/science-execution/program-information.html?id=1618

In terms of exomoons, it should be possible for gas giants of this size, or any, to form Mars-Earth sized moons, right? Maybe in some sort of even analogous to the hypothetical Earth-Theia collision.

Link to comment
Share on other sites

2 hours ago, Spaceception said:

In terms of exomoons, it should be possible for gas giants of this size, or any, to form Mars-Earth sized moons, right? Maybe in some sort of even analogous to the hypothetical Earth-Theia collision.

The issue with an impact on a gas planet forming a moon is that the debris would mostly be, well, gas. So I wouldn't expect a solid rocky body to result from that particular event. But I do hope there are such moons out there.

Link to comment
Share on other sites

On 7/15/2022 at 11:44 AM, JoeSchmuckatelli said:

I know that three is a small number... But if we had scopes at L2, L4 and L5 - would that be enough to get useful data for a relatively low cost? 

 

L2 is shaded by the Moon.  I don't think the others make sense. 

I also heard  that NRO gave NASA (or at least made availablefor some time) a spare hubble-class mirror.  They haven't bothered to launch another Hubble, or even plan a second go after the first gets re-entered.  I think the biggest problem in building the thing are the delays.  You'd have to build from print, which likely includes parts that haven't been made for 20 years.  Don't expect to hire the people who made it originally, so you lost all that expertise.  My guess is that you'd start all over again, and the next would cost > $10 Billion (although making a few at a time might make sense).

Link to comment
Share on other sites

2 hours ago, cubinator said:

The issue with an impact on a gas planet forming a moon is that the debris would mostly be, well, gas. So I wouldn't expect a solid rocky body to result from that particular event. But I do hope there are such moons out there.

Oh, I was thinking more along the lines of - you have a collection of smaller moons forming, and then a protoplanet in a similar orbit smacks into those, adding more material to the planet-moon system.

Then you have questions like, how much was lost from colliding into the planet, or being flung out entirely? Was there a net increase? And what's the likelihood of a single large moon forming from that event (or in general with mostly the original material).

Edited by Spaceception
Link to comment
Share on other sites

https://en.wikipedia.org/wiki/Hill_sphere#Solar_System

Body Million km au Body radii Arcminutes[note 1] Furthest moon (au)
Mercury 0.1753 0.0012 71.9 10.7
Venus 1.0042 0.0067 165.9 31.8
Earth 1.4714 0.0098 230.7 33.7 0.00257
Mars 0.9827 0.0066 289.3 14.9 0.00016
Jupiter 50.5736 0.3381 707.4 223.2 0.1662
Saturn 61.6340 0.4120 1022.7 147.8 0.1785
Uranus 66.7831 0.4464 2613.1 80.0 0.1366
Neptune 115.0307 0.7689 4644.6 87.9 0.3360
Ceres 0.2048 0.0014 433.0 1.7
Pluto 5.9921 0.0401 5048.1 3.5 0.00043
Eris 8.1176 0.0543 6979.9 2.7 0.00025

 

{\displaystyle {\frac {r_{\mathrm {H} }}{r}}\approx {\sqrt[{3}]{\frac {m}{3M}}}.}

Jupiter in the habitation zone of the Sun:

Rhill = 50.5/ 5.2 ~10 mln km.

Not much room for an Earth-like planet.

In case of a dwarf star decrease this even more.

Unlikely a habitable moon can be inside a habitable zone.

Link to comment
Share on other sites

4 hours ago, wumpus said:

L2 is shaded by the Moon

ahem... occasionally, and then briefly.  (Unless you were thinking about the Moon's Lagrange Points with Earth?)

From this:

Lagrangian_points_equipotential.gif

It looks like the 'sides of the triangle' (diamond?) will be at least 1AU per, so we'd get a lot of angular distance limited only by the size of individual receptors.  Information could be combined in relative real time.  Unlike how we do 6-month orbital parallax observations now.

Link to comment
Share on other sites

8 minutes ago, JoeSchmuckatelli said:

ahem... occasionally, and then briefly.  (Unless you were thinking about the Moon's Lagrange Points with Earth?)

From this:

Lagrangian_points_equipotential.gif

It looks like the 'sides of the triangle' (diamond?) will be at least 1AU per, so we'd get a lot of angular distance limited only by the size of individual receptors.  Information could be combined in relative real time.  Unlike how we do 6-month orbital parallax observations now.

Usually Lagrange points have a name identifier before the number. Example: Earth-Sun L2 and Earth-Moon L2. I have only seen that drop when it is obvious, like an Artemis focused presentation or something.

Link to comment
Share on other sites

1 hour ago, JoeSchmuckatelli said:

ahem... occasionally, and then briefly.  (Unless you were thinking about the Moon's Lagrange Points with Earth?)

From this:It looks like the 'sides of the triangle' (diamond?) will be at least 1AU per, so we'd get a lot of angular distance limited only by the size of individual receptors.  Information could be combined in relative real time.  Unlike how we do 6-month orbital parallax observations now.

Obviously I was thinking about lunar L2, while Webb is in Sun/Earth L2 and thus shaded by Earth.  Any other Lagrange point wouldn't have that, and you would have far more heating/light pollution problems.  But the other points still don't make sense (any of the Earth/Moon points, or any other Sun/Earth points).

Link to comment
Share on other sites

48 minutes ago, wumpus said:

Too far away?

No, it's in a halo orbit around L2. Think about it, if it couldn't see the Sun, how would its solar panels provide power?

https://webb.nasa.gov/content/about/orbit.html

Quote

And Webb will orbit around L2, not sit stationary precisely at L2. [...] This orbit (which takes Webb about 6 months to complete once) keeps the telescope out of the shadows of both the Earth and Moon. Unlike Hubble, which goes in and out of Earth shadow every 90 minutes, Webb will have an unimpeded view that will allow science operations 24/7.

Link to comment
Share on other sites

11 hours ago, kerbiloid said:

Any L point is a gravitational junkyard. A proper place to place an overexpensive telescope.

I would say 'big sky, little bullet' but then Webb's already been hit... 

Edited by JoeSchmuckatelli
Link to comment
Share on other sites

11 hours ago, kerbiloid said:

Any L point is a gravitational junkyard. A proper place to place an overexpensive telescope.

Any junk loitering around a Lagrange point would be moving relatively slowly (by astronomical terms) compared to anything else parked there....

39 minutes ago, JoeSchmuckatelli said:

I would say 'big sky, little bullet' but then Webb's already been hit... 

... by something passing through.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...