New technique to measure mass of exoplanets

MIT scientists have developed a new technique to measure the mass of exoplanets, which can help determine if any of these far-off worlds are habitable.
To date, scientists have confirmed the existence of more than 900 exoplanets circulating outside our solar system.
To determine if any of these far-off worlds are habitable requires knowing an exoplanet's mass - which can help tell scientists whether the planet is made of gas or rock and other life-supporting materials.
A planet's mass can provide a glimpse of it's surface and internal activity in addition to it's composition.
This data has traditionally been used to determine a planet's size and atmospheric properties, but the Massachusetts Institute of Technology (MIT)team has found a way to interpret it such that it also reveals the planet's mass.

"With this method, we realised the planetary mass - a key parameter that, if missing, could have prevented us from assessing the habitability of the first potentially habitable Earth-sized planet in the next decade - will actually be accessible, together with its atmospheric properties," said Julien de Wit, a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences.

"The mass affects everything on a planetary level, such as any plate tectonics, its internal cooling and convection, how it generates magnetic fields, and whether gas escapes from its atmosphere," de Wit said.
"If you don't get it, there is a large part of the planet's properties that remains undetermined," said de Wit.

Using large telescopes such as the NASA's Spitzer or Hubble space telescopes, scientists have been able to analyse the transmission spectra of newly discovered exoplanets.
To determine the mass of an exoplanet using transmission spectroscopy, de Wit relied on the effect that a planet's mass has on its atmosphere, as transmission spectra give information on a planet's atmospheric properties.
To do that, he worked from a standard equation describing the effect of a planet's temperature, gravitational force, and atmospheric density on its atmospheric pressure profile - the extent to which pressure changes throughout its atmosphere.
The study was published in the journal Science.