The sun. This picture is from just before second contact when Venus becomes entirely on the surface of the sun. Venus is most of the way onto the sun at about the 11 o'clock position. The image of the sun is from a projection telescope. The telescope is focused so that the image appears on a projection screen about a foot behind the telescope. It is one of the best ways to view the sun. One reason is you do not risk burning your eyes because of improper filtering, and the other is that it lets many people look at the image at the same time. The large smudgy bits are clouds, and the little black dots are sunspots.
To give you an idea of scale, the small sunspots you can see are around the size of the earth. Venus appears much bigger, but in fact it is just slightly smaller than earth. The reason it appears so large is that it is much closer than the sun. It is just over 1/4 of the distance from here to the sun, or about 30 million kilometers. That doesn't really mean much to us, but to give a sense of the distance, it would take an airliner 4.8 years to cover that distance. It takes light about 2 minutes to do the same trip.
