Some Protoplanetary Disks have Water Vapor

So, not only have astronomers found methane in the atmosphere of a planet circling another star, but now CalTech astronomers have found water vapor in the spinning disks of gas and dust surrounding other stars. These disks, called protoplanetary disks, or “proplyds” for short, are where planets are born.

The Earth and other planets of the solar system formed in a proplyd beginning more than 4.5 billion years ago, and so we look to other systems to understand how planets are born, and how ours looked at that time. The image here is a protoplanetary disk in the Orion Nebula studied by Hubble Space Telescope.

The astronomers used NASA’s Spitzer Space Telescope and the Keck II telescope on Mauna Kea in Hawai’i to study the infrared wavelengths of light emitted by from these disks. The chemical fingerprints of water vapor showed up in disks around the stars DR Tau and AS 205A. The next step was to figure out where the vapor exists in the disk around each star. So, the science team (consisting of astronomers from CalTech, the Leiden Observatory in the Netherlands, SRON, and the University of Texas at Austin) made high-resolution measurements at shorter wavelengths of infrared light. The data showed the clumps of material where the water resides were moving at fast speeds, meaning that the clumps are closer to their stars, possibly in regions where Earth-like planets might be forming.

Now, you might think, “Okay, so they’ve found water vapor at a couple of stars. So what?” Astronomers expect to make more observations of dozens of similar-type stars, and the two instruments they’ve used should turn up more water vapor in more proplyds (if it exists). The bigger implications lie with figuring out how water concentrations evolve and survive in protoplanetary disks and eventually create oceans (or ice-covered planets). Who knows? What scientists find may help us understand how Earth got its oceans. Stay tuned!