Where’s the water, Lebowski?

credit: NASA

A survey of 10 hot, Jupiter-sized exoplanets conducted with NASA’s Hubble and Spitzer space telescopes has led a team to solve a long-standing mystery — why some of these worlds seem to have less water than expected. The findings offer new insights into the wide range of planetary atmospheres in our galaxy and how planets are assembled.

Of the nearly 2,000 planets confirmed to be orbiting other stars, a subset of them are gaseous planets with characteristics similar to those of Jupiter. However, they orbit very close to their stars, making them blistering hot.

Their close proximity to the star makes them difficult to observe in the glare of starlight. Due to this difficulty, Hubble has only explored a handful of hot Jupiters in the past. These initial studies have found several planets to hold less water than predicted by atmospheric models.

The international team of astronomers has tackled the problem by making the largest-ever spectroscopic catalogue of exoplanet atmospheres. All of the planets in the catalog follow orbits oriented so the planet passes in front of their parent star, as seen from Earth. During this so-called transit, some of the starlight travels through the planet’s outer atmosphere. “The atmosphere leaves its unique fingerprint on the starlight, which we can study when the light reaches us,” explains co-author Hannah Wakeford, now at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

By combining data from NASA’s Hubble and Spitzer Space Telescopes, the team was able to attain a broad spectrum of light covering wavelengths from optical to infrared. … (Spitzer)

credit: NASA

credit: NASA

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