Interesting project

[M Holmes]

Jonathan Jarrett writes:

> On Tue, 20 Apr 1999, M Holmes wrote:
>
> > > Apparently NASA have decided to
> > > send their next `interferometry mission' (a project aimed at finding
> > > Earth-sized planets revolving around nearby suns) to this Andromedae.
> >
> > So we'll get the results in a few thousand years? Maybe they're just
> > going to point some instruments in that direction?
>
>         Well, this puzzled me too, since the Andromeda galaxy is thousands
> of years away, but I don't actually know how far the stars that make up
> the _constellation_ are.

I believe the star in question is around 45 light years away.

>         Anyhow, I know very little about NASA's current work, but an
> astronomer friend her at Cambridge informs me that interferometer work is
> done by analysing light sources, and requires no satellites - I thought
> this was spectroscopy but she tells me this is related but different.

I suspect they're talking about wide baseline interferometry. This is
where you get two or more instruments and by coordinating their input
through computer it's kinda like having a telescope with that size of
lens but without the implied light collection that goes with it.
Obviously there's a limit (about 8,000 miles) as to how far you can get
surface instruments apart hence putting 'em in orbit.

It's not my area, but my suspicion is that the wider apart the
instruments, the better the available discrimination and that they plan
to try to discriminate any light (or other radiation perhaps) from the
star from light from the planets. That might give 'em a crack at
spotting rock planets.

> > One thing I did wonder is whether having two Jupiter sized planets in a
> > system would be good for rock type planets since there'd be considerably
> > more gravitational perturbations in such a system. I'm too lazy to do
> > the math though. We used to have professional astronomers on this list
> > (Hey McIntyre, you still out there?). Maybe they could comment.
>
>         No astronomer I, but although Jupiter is massive, Saturn, Uranus
> and Neptune are no tiddlers. I'm not sure the effects on the system would
> be any more severe - wouldn't there be an equivalent sort of calm zone
> such as we have inside the giants' orbits?

I have to confess that I just don't know. On the other hand I do take
"Spaceflight", the magazine of the British Interplanetary Society, so I
could keep an eye out for articles on this.

>                      Jon

FoFP