How To See If An Exoplanet Has Moons

Saw a cool article from Wired. I realize it came out a little while ago now but it’s not like the science got old or anything. Basically, it’s showing how we might be able to detect the composition of a planet based on what shows with specific spectrums of light. It’s really neat!

To quote the article:

If astronomers were looking at the Earth-moon system from a distance in relatively long infrared wavelengths (10 micrometers [..]), they would see light coming from both bodies.

But at slightly shorter wavelengths (4.3 micrometers), where carbon dioxide strongly absorbs light, the Earth –- whose atmosphere is full of carbon dioxide -– would disappear, while the airless moon would keep glowing brightly.

Apparently this was a side project of a University of Washington student named Tyler Robinson who was imagining how we might be able to detect moons around the exoplanets we keep on discovering.

Why would we care?

[…] the moon has done a lot for our home planet: stabilizing its axial tilt, creating ocean tides, and slowing down its daily rotation, which has probably led to a less turbulent atmosphere. All of these have been beneficial to the development of life.

This is all not just because we have a moon, of course, but because we have a very large moon (1/81 the mass of Earth), not that we like to brag…

While most of the planet observations have been made by watching an exoplanet transit its star or observing the wobble of a star and calculating the mass necessary to cause it, in the future we might be able to see them, or the light that passes over and around them, directly. Being able to tell if there was a moon and its size relative to the planet might really be able to tell us whether there is a known habitable type world out there.

Just as a science-fiction thought experiment, it might be fun to find these planets and bombard them with strong radio signals. That way, if there was life and if they were in their Renaissance periods, say, by the time they got around to inventing radio several hundred years later, they’d also be introduced to the Pixies, Nirvana, and… hell, I’ll admit it, I’m a fan… Sarah McLaughlin.

Then, we’d have to wait several hundred more years for the reply, which will hopefully be like the old Saturday Night Live joke about the Voyager Golden Record, “Send more Chuck Berry.”

I mean, think about how cool it would be to wake up one day and start listening to messages sent from another world who considered ours a possible candidate for the existence of life?

Anyway, I volunteer to man the DJ booth at the Very Large Array.