SIM Planet Quest Web Page
Abstract
| We will apply SIM observations to 4 related microlensing experiments: (1) measure the mass function (MF) of the Galactic bulge down to 0.01 Msun from ~200 microlensing mass measurements with separate identification of brown dwarfs (BDs), white dwards (WDs), neutron stars (NSs), and black holes (BHs), (2) measure the mass and distance of 5 of the lenses currently being detected toward the LMC/SMC, and so determine whether they are halo objects (MACHOs) and hence a substantial component of the dark matter, or are ordinary stars related to the LMC/SMC, (3) measure masses of 15 nearby stars to 1% accuracy, including 4 low-metallicity stars, (4) measure the masses of ~15% of planets found in bulge microlensing events. Microlensing (the gravititional deflection of light) is a powerful tool for detecting astrophysical objects irrespective of whether they shine. More than 500 objects have been detected over the last decade in photometric microlensing experiments, where the lens betrays its presence by focusing (and so magnifying) the light from a more distance source. Unfortunately, the information photometric microlensing yields about the lens is usually highly ambiguous, with typically a factor ~100 uncertainty in lens mass. However, microlensing also gives rise to astrometric deflections which can be measured by SIM. By combining astrometric and photometric measurements, lens masses and distances can be determined to a few per cent, so that the nature of these dark objects (including planets, BDs, WDs, NSs, BHs) will be revealed for the first time. A variant on this technique will permit SIM to measure the masses of nearby stars very accurately (<1%). We expect that the detection of non-luminous objects, particularly black holes and planets will evoke wide public interest, which will facilitate educational initiatives made in conjunction with SIM.
Proposal (short version) Collaborators
teams, click the SIM image below) 
to be launched in 2010 by NASA |