Category Archives: super-Earths

exoplanets, super-Earths

Icarus Planets Lose Their Atmospheres

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Planets: Don’t Fly Too Close to Your Star

super-Earth planets can lose their atmosphere to strong stellar radiation
A super-Earth gets too close to its star and loses its atmosphere to the star’s intense radiation. Illustration by Peter Devine

In the old legend of Icarus, the man-god flew too close to the Sun against his father’s warnings. The heat from our star melted his waxy wings and Icarus plummeted to his death. It’s a cautionary tale as old as humanity.

There’s a new variation on that myth, and it has to do with a subset of super-Earth exoplanets recently studied by astronomers. These are rocky worlds with atmospheres and they make tight orbits around their stars. Intense radiation from their parent stars simply blows away their atmospheres, leaving behind a barren wilderness of a planet.

This doesn’t happen to every massive planet and its star, but it may be something that happens as young stars and their newly formed planets evolve over time. The most likely candidates for this atmospheric stripping are worlds that received 650 times MORE radiation than Earth receives from the Sun. The planetary atmospheres don’t have a chance. They just get blown away — gone with the stellar wind.

Asteroseismology Tells the Tale

The astronomers who found these airless worlds used data from the Kepler mission to study  the stars where these worlds orbit.  The data helped researchers perform asterseismology to characterize the host stars, and to figure out the sizes of their super-Earth planets. The worlds without atmospheres turn out to be a new category of exoplanets, and occupy a niche in planetary formation and evolution that astronomers are still working to understand.

Asteroseismology is a technique that reveals the inner structure of a star. Astronomers use it to measure a star’s pulsations. Different rates of oscillations give clues to activity at several depths and the star’s surface. It’s not unlike studying seismic waves on Earth during earthquakes. In that case, geologists use the waves to understand the structure beneath of the surface of our planet.

A star’s oscillations are reflected in its brightness variations. Even the most subtle pulsations can tell something about the star, and finding planets barren of atmospheres orbiting distant stars gives a clue about past and current stellar activity. Asteroseismology helps complete that picture.

I’m constantly amazed at the things we learn about the cosmos using such tools as the Kepler telescope. What started out as a planet search is yielding amazing peeks into the interiors of stars, too.

astronomy, astronomy news, exoplanets, super-Earths

Super-Earth, Super Atmosphere

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55 Cancri e Shows Off Its Blanket of Air

This artist’s impression shows the super-Earth 55 Cancri e in front of its parent star. Using observations made with the NASA/ESA Hubble Space Telescope and new analytic software scientists were able to analyse the composition of its atmosphere. It was the first time this was possible for a super-Earth.
This artist’s impression shows the super-Earth 55 Cancri e in front of its parent star. Using observations made with the NASA/ESA Hubble Space Telescope and new analytic software scientists were able to analyse the composition of its atmosphere. It was the first time this was possible for a super-Earth.

Well, this is kind of cool. Or, actually, it’s rather dry and hot.  The 55 Cancri has a super-Earth planet orbiting around it with some unusual properties. Astronomers used the Hubble Space Telescope to study its atmosphere as this distant world transited across the face of its star. That way, they could study the star’s light as it traveled through the planet’s atmosphere and then deduce something about the conditions on 55 Cancri e.

So, what’s the weather like there?

Turns out it’s dry. Really dry. As the international team of scientists found out, there’s not a trace of water vapor in the blanket of gases smothering this planet. And, since the planet is orbiting very close to its star, conditions are likely too hot to support things like oceans and rivers and lakes on this world. The surface temperature is around 2000º C (that’s 5,432º F, which is only somewhat cooler than the visible surface of the Sun at 7,800º F).

Exploring this Super-Earth

Astronomers call such worlds “super-Earth” because they have a mass larger than our planet’s, but are still much smaller than the really massive, large planets such as the hot Jupiters, super-Neptunes, and so on.

This particular super-Earth is a bit different from some of the others that astronomers have studied. A year there lasts for only 18 hours. That’s because it orbits so close to its star.  Now, that’s a good thing if you want to study a star’s atmosphere because it gives you a LOT of chances to watch as it transits the star. And, using Hubble Space Telescope, and in particular, the Wide Field Camera 3, astronomers were able to analyze the atmosphere and detect the gases hydrogen and helium — the first time this has ever been done with a super-Earth.

There’s a lot more to learn about this world from the HST data gathered, and I’m pretty sure that astronomers are going to use this as a springboard to study even MORE of these massive Earth-size (but not necessarily Earth-like) worlds. Stay tuned!