Amateur Exoplanet Imaging

SpaceDreamer

Is it possible to detect exoplanets with amateur telescopes? If so what size would be needed. I have seen some amateur protoplanetary disks pictures and would one be able to tell if an exoplanet existed in it as I carved out the material for planet formation? Is it possible for us with current technology to conduct spectrography on an exoplanet?

Thanks.

Drakkith

It is pretty much impossible to directly image an exoplanet using amateur equipment. They are simply too close to their stars and the stars are too bright. However you can easily detect an exoplanet transit by measuring the light output of the host star. I have done that myself using an 8 inch scope.

sophiecentaur

That is very impressive! If you can do that (with the greatest respect) how come it is only recently that they've been finding expoplanets - bearing in mind the thousands of enthusiastic amateurs involved. But I guess you already knew where to look?

Drakkith

Yep. I already knew where to look. Plus, the idea was only developed in the last two decades. So even though its really easy, we just didn't know it was possible until lately. Also, amateurs only have had access to CCD detectors in the last decade, so amateur detection of these planets was pretty much impossible before then as there was no way to get accurate photometric measurements from film. (At least not the accuracy you need to detect exoplanet transits)

sophiecentaur

I guess the CCDs for all made all the difference. I remember a talk at School from 'Kevin' of 'Planet Kevin' (a young Australian, if I remember right) a little over ten years ago and he was describing a 'doppler shift' detection system, based on the wobble caused by large planets around stars. Then the brightness variation method reared its head. I guess the chances of transits is less than the chances of finding a wobble??? What's the state of things?

Drakkith

The radial velocity detection method is much more likely to be noticed, as the system doesn't have to line up almost perfectly edge on. However, the more edge on it is, the easier it is to detect the doppler shift, so it still matters some. BUT transits that do happen can be easier to detect than small doppler shifts, as even small telescopes can detect large transiting exoplanets, while it takes very large telescopes to gather enough light and have enough resolution to detect the doppler shift.

The other issues is that plenty of events happen that look like transits, so practically all discovered transiting exoplanets had to be double checked using the radial velocity method before being "confirmed" as exoplanets.

sophiecentaur

. . . . so you can only see the occasional rare transit and not an 'annual' one, presumably? I'm basing that on the infrequent occurrence of the transit of Venus, seen from Earth. It seems a very hit and miss affair. How do the numbers work? Does it require large planets?

Drakkith

It depends on the orbital characteristics really. Most transiting exoplanets we have discovered have regular transits. It probably helps that our own orbital motion matters very little, unlike the transit of Venus.

Larger planets block more light and are easier to detect, so we have a very large amount of those detected compared with terrestrial size planets. However we are discovering smaller planets and more of them all the time.

sophiecentaur

That's what makes all the difference, I suppose. I hadn't thought of that.
There must be so many more that we don't see - a factor of a hundred or more.
The details of other peoples' fields are always fascinating. Cheers for the insight.

Drakkith

Heh, I like how you say fields like I'm actually a real astronomer.

sophiecentaur

If you've got it, flaunt it Ducky!

Drakkith

Lol. Gimme a few years and I may have it.