Microlensing

Gravity as a magnifying glass

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A foreground star’s gravity can magnify a background star: microlensing.
• Magnification $A = \frac{u^2 + 2}{u\sqrt{u^2 + 4}}$, about $1/u_0$ at the peak for close passes.
• Planets around the lens add short blips; each event happens only once.

Steps

1. Bending starlight
2. A lensing light curve
3. At the Einstein radius
4. Planets in the blip
5. Never again
6. A close pass