2 — Introduction
A reading-first guide to gravitational microlensing, from first principles to fitting real light curves.
When a foreground object passes close to our line of sight to a more distant star, its gravity can bend and magnify the starlight. In the simplest model, an isolated point-mass lens and a steady, point-like source moving uniformly relative to one another produce a smooth, symmetric light curve. This is gravitational microlensing. More complex events need not follow this shape. [1]
Microlensing can reveal objects that emit little or no detectable light of their own, from planets to stellar remnants. An event’s timescale depends on the lens mass, the geometry and the relative motion. A simple photometric light curve alone does not determine a unique lens mass. [2]
This Introduction presents the basic picture qualitatively. The planned later chapters will develop the deflection of light by a point mass, magnification and its variation through time, before exploring how models can be fitted to observations.
How to read this guide
Home Page and Introduction are the available sections in this release. The sidebar shows the guide’s reading order; sections 3–7 remain marked in progress and cannot be opened. Both the parameter explorer and the data-fitting tools are planned and are not available yet.
What you will be able to do
After this Introduction, you should be able to describe the roles of the lens and source, and explain qualitatively why a passing lens can brighten a star. The planned later chapters will connect this picture to model parameters and their estimation from observations, including the limits of that inference.
For those chapters, u denotes the angular lens-source separation divided by the
Einstein angle, and u_0 its minimum. t_E is the time for relative motion
through one Einstein angle, and μ denotes the total magnification. [1]