Western Australia's Astronomy & Space Science Community

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Probing Lensing Anomalies NETwork (PLANET)

The Probing Lensing Anomalies NETwork (PLANET) has been looking for variations in microlensing events.

Microlensing is an optical effect which occurs when a large mass (usually a star) passes in front of a background star and gravity “bends” the light towards the observer. When the foreground object is directly between the observer and the background star the light from the background star is uniformly “bent” by gravity and redirected towards the observer in the form of a ring around the foreground object. As the foreground object moves away from the centre the ring separates into two images of the background star. Often the ring and dual images are not resolvable, but are recorded as an increase in the brightness of the star.

Previous microlensing surveys were conducted obtained well defined light curves (a record of the variances in the brightness) on a scale of 10s or 100s of days. However, these curves are generally poorly defined at the time scales needed to observe small-scale variances. These small-scale variances are what give astronomers clues to the structure of the foreground (or lensing) object. PLANET uses smaller time-scale surveys of potential microlensing events to get finer detail of any variances in the microlensing events.

Variances can be caused by a large range of reasons, all with different geometries and lensing properties. These include: double lenses, double background stars, background and foreground light mixing, or even planetary systems around lenses.

PLANET uses four telescopes; all located in the Southern Hemisphere, in three different countries (2 in Australia; Perth and Mt Canopus) to conduct its observing campaigns. PLANET has 32 members in 18 institutions across 10 countries.

To learn more about PLANET or microlensing, please visit their website.