October 19th, 2010
In the new study, astronomers report observations of upsilon Andromedae b taken across five days in February of 2009. This planet whips around its star every 4.6 days, as measured using the "wobble," or radial velocity technique, with telescopes on the ground. [...]
Spitzer measured the total combined light from the star and planet, as the planet orbited around. The telescope can't see the planet directly, but it can detect variations in the total infrared light from the system that arise as the hot side of the planet comes into Earth's field of view. The hottest part of the planet will give off the most infrared light.
One might think the system would appear brightest when the planet was directly behind the star, thus showing its full sun-facing side. Likewise, one might think the system would appear darkest when the planet swings around toward Earth, showing its backside. But the system was the brightest when the planet was to the side of the star, with its side facing Earth. This means that the hottest part of the planet is not under its star. It's sort of like going to the beach at sunset to feel the most heat. The researchers aren't sure how this could be.
This seems like a good moment to quote Isaac Asimov:1
The most exciting phrase to hear in science, the one that heralds new discoveries, is not Eureka! (I found it!) but rather, "hmm… that's funny…"
[Via James Nicoll]