by neufer » Sun Apr 07, 2013 3:15 pm
cbergcberg wrote:
Is Saturn actually where it appears? Would the moon have enough mass to gravitational lens the image in any way?
Saturn is
slightly closer to the moon than it appears.
The Sun bends the light of stars by up to ~1.75 arcseconds.
However, the Moon bends the light
by only ~ 26 µas (microarcsecond).
Nevertheless, this will be within the power of Gaia to measure:
http://en.wikipedia.org/wiki/Gaia_probe wrote:
<<Gaia is a space observatory to be launched by the European Space Agency (ESA) in October 2013. The mission aims to compile a 3D space catalogue of approximately 1 billion stars, or roughly 1% of stars in the Milky Way. Successor to the Hipparcos mission, it is part of ESA's Horizon 2000 Plus long-term scientific program. Gaia will monitor each of its target stars about 70 times to a magnitude 20 over a period of 5 years. Its objectives comprise:
- determining the positions, distances, and annual proper motions of 1 billion stars with an accuracy of about 20 µas (microarcsecond) at 15 mag, and 200 µas at 20 mag
more accurate tests of Albert Einstein’s general relativity theory
detection of tens of thousands of extra-solar planetary systems
capacity to discover Apohele asteroids with orbits that lie between Earth and the Sun, a region that is difficult for Earth-based telescopes to monitor since this region is only in the sky during or near the daytime
detection of up to 500,000 distant quasars>>
[float=right][img]http://sunearthday.nasa.gov/2006/images/news_einstein2.jpg[/img][/float]
[quote="cbergcberg"]
Is Saturn actually where it appears? Would the moon have enough mass to gravitational lens the image in any way?[/quote]
Saturn is [u]slightly[/u] closer to the moon than it appears.
The Sun bends the light of stars by up to ~1.75 arcseconds.
However, the Moon bends the light
by only ~ 26 µas (microarcsecond).
Nevertheless, this will be within the power of Gaia to measure:
[quote=" http://en.wikipedia.org/wiki/Gaia_probe"]
<<Gaia is a space observatory to be launched by the European Space Agency (ESA) in October 2013. The mission aims to compile a 3D space catalogue of approximately 1 billion stars, or roughly 1% of stars in the Milky Way. Successor to the Hipparcos mission, it is part of ESA's Horizon 2000 Plus long-term scientific program. Gaia will monitor each of its target stars about 70 times to a magnitude 20 over a period of 5 years. Its objectives comprise:
[list][b][color=#0000FF]determining the positions, distances, and annual proper motions of 1 billion stars with an accuracy of about 20 µas (microarcsecond) at 15 mag, and 200 µas at 20 mag
more accurate tests of Albert Einstein’s general relativity theory[/color][/b]
detection of tens of thousands of extra-solar planetary systems
capacity to discover Apohele asteroids with orbits that lie between Earth and the Sun, a region that is difficult for Earth-based telescopes to monitor since this region is only in the sky during or near the daytime
detection of up to 500,000 distant quasars>>[/list][/quote]