Mercury

DEPARTAMENT
D'ASTRONOMIA I METEOROLOGIA

WHAT CAN WE SEE?

Do not expect to see a big circle moving across the Sun!!
Mercury is extraordinarily small when compared with the Sun. During the transit, the planet's disc will have an apparent diameter 160 times smaller than the Sun's disc.

Here's some advice on how to identify Mercury on the images:

The surface of the Sun often shows several dark spots, namely sunspots. These are cooler regions on the surface, with temperatures some 2000 degrees below that of the surrounding areas, which, due to the strong contrast, appear to be dark. Do not misidentify Mercury with one of those spots. Sunspots tend to show irregular shapes while Mercury is a nearly perfect circle. Also, Mercury will apear darker than any of the other spots.
Mercury will move slowly across the Sun's disc. Compare subsequent images to distinguish its change in position.
Compare the images with the predicted trajectory of Mercury. Pay attention to the position of Mercury at different moments of time.
This is a sample transit image. Note how small is Mercury when compared with the Sun.

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