The Science Of Planet Detection

Black Dog writes: "It seems like we're hearing about the 'Extra-Solar Planet of the Week" lately. I thought it might be useful for everyone to bone up on planet detection techniques. Two of JPL's projects are at: The Terrestrial Planet Finder and techniques for planet detection."

Comments

Re:What are the pratical uses for this?

[Bill Currie]

The practical use of discovering planets we can't get to is to generate motivate to figure out how to get to them.

Just think about befor boats were invented:

"ooh, look there's an island over there"

"yeah, but it's too far to swim"

a log floats by...

I'm sure you get the idea.

Re:But can we get there?

[HeghmoH]

I'm reminded of the article on slashdot a while back about how delaying the start of an enormous computational task can actually make it so the task finishes sooner, because of the march of computational technology.

I suspecet that the same is true here. Drive systems will continue to get better, though not at the same rate or with the same regularity as computing technology. An ion drive system will help, as would fusion drives.

However, note this: 200 years to go 10 light years is 5% of the speed of light, or roughly 54 million kilometers per hour. Current spacecraft travel around one thousandth of this, or in the neighborhood of 50 thousand kilometers per hour. With current technology, the trip would take more like 250,000 years, which is quite a while even in the great scheme of things.

Check out the BOSS!!

[The Iconoclast]

There is a group at my university's physics department working on a design for a cool planet detecting satillite. It is called BOSS. Check it out, cool stuff.

A wealthy eccentric who marches to the beat of a different drum. But you may call me "Noodle Noggin."

Needle in a Forest

[WillAffleck]

Our basic problem is that we are getting fairly good at finding planets, but not terrestrial ones. Gas giants, no prob. But Earth-sized, we're not quite there yet.

Additionally, the ones we do find that might be earth-sized we find only because they are erratic in orbit or receive too much radiation (which is how we can find them).

We need to start sending out packages above or below the solar plane, with sufficient telemetry and telescope size (e.g. Hubble), and in greater number. And we need to start sending drone ships with basic measurement devices towards some of the more likely candidates, to extend the search range.

But we would rather spend the money on fueling up our SUVs and creating military forces to get fuel for those SUVs. For only $10 a year per capita, we could (the US or the EU) easily create enough detection equipment and the scientists to analyze it.

The joys of optical interferometry

[tjwhaynes]

My old astronomy lab have a group working on optical interferometry, and have a working optical interferometry complete with four (or possibly now five) telescopes linked together. If you are interested in the details, there is a good introduction and more detailed information here. Now the interesting thing here is that it is very important to keep the telescopes at exactly the same distance apart or compensate in some way (here there are trolleys running up and down a long (30m) optical bench and the telescopes are concreted into the ground. The problems inherent in doing optical interferometry in space present many of the same problems examined in this project, plus the limitation that you can't just stick an optical bench on a satellite and hope to get it off the ground. On the other hand, ten years ago people were highly sceptical of getting optical interferometry working on anything more than a rudimentary basis and felt that map making was many years away, so maybe those problems can be solved too.

Cheers,

Toby Haynes

A good proposal, possibly overly optimistic.

[Brand X]

I took a good look at the proposed detector, which is essentially a directional spectroscopic satellite. It looks feasible enough, given enough time and enough satellites, if the initial assumption (that terrestrial planets are common) is correct. It won't produce quick results, I expect.

This is actually a very interesting line of investigation, and one that is highly popular in SF. Instead of the current approach of scanning stars for the results of gravitational perturbations (which I was surprised to see finding sub-Jovian planets), the TPF scans for light in specific emission spectrums - water, maybe oxygen and ozone, perhaps ammonia and methane, nitrogen... I'd assume this would mean using a time-based saturation filter to screen out everything from the star and all the stars behind it, loose ice and dust and complex non spectral light sources and reflectors.

If they're smart, they'll find a way to factor the red/blue shift of the target bodies into the filter, as well as shifting the spectrums. Given enough time, they could build up the period of the target body, and therefore determine its orbital radius...

Of course, that would entail finding the signatures in the first place. Unfortunately, the fact that a dimmer star might have a terrestrial planet very, very close could result in a very high periodic shift (relatively), which might cause problems if a very narrow wavelength filter were being used to stamp out undesirable light sources.

Lots of things for them to think about when building this... and all relying on getting a tremendous amount of ultra-sensitive electronics into orbit. Shame we don't have orbital industry yet.

My personal planet detection technique

[unitron]

1. go outdoors
2. look down