Water Discovered in Atmosphere of ‘Warm Neptune’ Exoplanet

The planet HAT-P-26b, dubbed as "Warm Neptune" due to its similarity in size, features a primitive atmosphere that could reveal a lot about the birth and development of planets in far-flung galaxies.

According to a report from Science Daily, the Neptune-like exoplanet was found to have an atmosphere that is composed nearly entirely of hydrogen and helium. It also appears to be relatively cloudless.

The atmosphere of this so-called warm Neptune, an exoplanet located 430 light years from Earth and much closer to its sun compared to the "real" Neptune, suggests two things: that HAT-P-26b actually formed closer to its star and/or that it formed later in its solar system development.

"This exciting new discovery shows that there is a lot more diversity in the atmospheres of these exoplanets than we have previously thought," co-lead author Professor David Sing from the University of Exeter said. "This 'Warm Neptune' is a much smaller planet than those we have been able to characterize in depth, so this new discovery about its atmosphere feels like a big breakthrough in our pursuit to learn more about how solar systems are formed, and how it compares to our own."

Using NASA's Spitzer Space Telescope and Hubble Telescope, the researchers collected data during transits, an event when a planet passes in front of its host star. The analysis revealed a strong water signature, which the team used to determine the metallicity. Metallicity indicates the planet's volume in all elements heavier than hydrogen and helium.

The warm Neptune's metallicity is closer to the value of Jupiter and Saturn's metallicity than Neptune and Uranus'.

"To have so much information about a warm Neptune is still rare, so analyzing these data sets simultaneously is an achievement in and of itself," co-author Tiffany Kataria from the Jet Propulsion Laboratory in Pasadena, California said.

The team published their findings in the journal Science.