I need to know if an exoplanet (mag 20 ) and its moon (mag 28) can be resolved by a 2m mirror. I can work out the resolving power of this mirror for targets of similar magnitude, but how do I work out its
resolution for targets of such widely differing brightness ?
2007-02-26 03:11:16 · 4 answers · asked by Chef Dane 2 in Science & Mathematics ➔ Astronomy & Space
You are correct that the magnitude difference and not the resolving power is the real problem with seeing planets around other stars. As seen from Alpha Centauri, Jupiter would be over 3 arc seconds from the Sun at greatest elongation. A 2m mirror can resolve 0.058 arc seconds, if the two objects are the same magnitude. But you didn't provide enough information. You didn't specify the separation in arc seconds. And it is the magnitude difference of the star and planet, not the planet and a possible moon that is important.
All that said, I am not completely sure how much lower the resolving ability is for very large differences in brightness. It has more to do with scattered light than diffraction limited resolving power.
2007-02-26 03:53:28 · answer #1 · answered by campbelp2002 7 · 2⤊ 1⤋
The chances of you being able to image a magnitude 28 anything are pretty slim. While the Hubble has imaged galaxies beyond magnitude 30, Earth-based observatories can't do much better than about 25. Anything dimmer than that is washed out by skyglow, even in the darkest skies.
You also haven't said what the separation is, but the orbit of an exoplanet's moon is probably in the ridiculous range for resolution, regardless of magnitude.
Even being able to resolve the planet is unlikely, given its proximity to a no doubt much brighter star. No one has manged to do this yet. Even here, unless the star is very close the separation is apt to be well below the resolving power of any telescope, even with adaptive optics.
On the general issue of determining visibility of double stars, there's a calculator for estimating the difficulty of a visual observation. The issues involved in imaging are somewhat different, but it should give you some idea of the issues.
2007-02-26 13:15:38 · answer #2 · answered by injanier 7 · 1⤊ 0⤋
I don't think anyone's ever actually seen an exoplanet through a telescope, but a 2 meter mirror is huge! What observatory are you using?
2007-02-26 11:49:30 · answer #3 · answered by Roman Soldier 5 · 0⤊ 0⤋
Do you mean a planet outside of our solar system? You cannot see them. Only their suns. It is hard enough to find a planet in our own solar system through a telescope.
2007-02-26 11:50:22 · answer #4 · answered by bldudas 4 · 0⤊ 0⤋