Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detection of Extrasolar Planets by Gravitational Microlensing   Gravitational microlensing provides a unique window on the properties and
prevalence of extrasolar planetary systems because of its ability to find
low-mass planets at separations of a few AU. The early evidence from
microlensing indicates that the most common type of exoplanet yet detected are
the so-called "super-Earth" planets of ~10 Earth-masses at a separation of a
few AU from their host stars. The detection of two such planets indicates that
roughly one third of stars have such planets in the separation range 1.5-4 AU,
which is about an order of magnitude larger than the prevalence of gas-giant
planets at these separations. We review the basic physics of the microlensing
method, and show why this method allows the detection of Earth-mass planets at
separations of 2-3 AU with ground-based observations. We explore the conditions
that allow the detection of the planetary host stars and allow measurement of
planetary orbital parameters. Finally, we show that a low-cost, space-based
microlensing survey can provide a comprehensive statistical census of
extrasolar planetary systems with sensitivity down to 0.1 Earth-masses at
separations ranging from 0.5 AU to infinity.

25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con