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Hubble and the Stars?

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Good mornng guys and girls

I have just been looking at some of the pics that Hubble has taken, there are some amazing images of course and I noticed that there are fair few which clearly show stars which seem be pretty large in the images I was looking at. Does anyone know where they use Hubble to consentrate on one star to see whats orbiting it? I mean it can clearly see these stars so should be able to see whats orbiting it right?

Thanks in advance and I hope all that makes sense.



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Hubble has been used for some exoplanet hunting, though there are other telescopes designed for this type of thing, noteably Spitzer and SuperWASP (Wide Area Search for Planets)

If your asking 'why can't we directly see exoplanets in Hubble public images?' then the answer is no....

The light-curves coming direct from exoplantes are very shallow, as they are non-luminous bodies and the parent stars light virtually eclipses it, a bit like taking a picture of a lighthouse from a few miles away and trying to pick out the reflection off a marble 1cm from the main beam.

So instead you need to look at either Doppler or Transit methods.

Doppler looks at how a set of element lines in a stars light spectrum shifts through time. If the star has a planet(s) orbiting then it wil wobble due to the gravitational pull of the planet(s), meaning the element lines either move to the blue end of the spectrum if the star moves towards us (exoplanet pulling it this way) or they will shift to the red end of the specturm if the star moves away from us (exoplanet on other side)

By timing and measuring the wobble you can account for the number of associated planets and also their mass.

Transit looks at the amount of light lost from a parent star when a non-luminous body (an associated exoplanet) passes infront of the star and our line of sight, again timing and measuring the amount of depleted light gives you an idea of the num there mass.

However the transit method only works for stars which have planets along our plane-of-view, so we could potentially not be finding lots of exoplanets.

Edited by EA2007
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I think you may be getting confused about the 'size' of the star on the Hubble image and its true size. What you see in Hubble images are not 'big' stars (well they might be but not in the way you mention) and I would guess that because of the darkness of the main object that Hubble images, any foreground stars will be 'over exposed', in other words a lot of photons are hitting the sensor, and this is causing flaring of the image, i.e. it looks bigger than it really is. Stars from our distance will always be points of light and nor show a disc, therefore any planets circling them will still be minute and buried in the glare from the star itself.

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