The closest star system to our own Sun may have two Earth-sized exoplanets orbiting it, a new study has shown based on observations by the Hubble Space Telescope. If confirmed, the discovery would help to illustrate just how common exoplanets are; data from Kepler and other telescopes has also already shown that the vast majority of stars have exoplanets orbiting them, and the number of exoplanets in our galaxy alone is now thought to number in the billions.
So far, thousands of exoplanets and exoplanet candidates have been found orbiting other stars. As well, astronomers have seen some exoplanets still in the process of formation, providing clues as to how our own solar system came to be. One of these recent “planet-under-construction” findings however is challenging current theories on planetary formation – it’s a planet which “shouldn’t be there” according to conventional wisdom.
Among the many exoplanets now being discovered, Fomalhaut B was considered something special – the first exoplanet to be directly photographed in visible light, by the Hubble Space Telescope, back in 2008. That is, until more recent studies suggested that it might not be real, not even a planet after all.
The Hubble Space Telescope has made new observations of a “waterworld” exoplanet which has a thick, steamy atmosphere.
The planet, GJ1214b, orbits a red-dwarf star and is about 40 light-years from Earth. It is about 2.7 times larger than Earth, with an estimated temperature of 232 ºC (450 ºF). While it orbits too close to its star to be in the habitable zone, and thus unlikely to have liquid water on its surface, it still apparently does have water in its atmosphere, and a lot of it.
It was initially discovered in 2009 by the MEarth Project using ground-based telescopes. Follow-up observations were made by Hubble in 2010, providing a more detailed look at the composition of its atmosphere.
It wasn’t clear however whether GJ1214b had a thick atmosphere of water vapour or if there was just a planet-wide haze in its atmosphere.
The new studies indicated that it is most likely the former – a hot, steamy atmosphere surrounding the planet. The science team used Hubble’s Wide Field Camera 3 (WFC3) to examine the atmosphere during a transit, when the planet crossed in front of its star. When the star’s light is filtered through the planet’s atmosphere, it can be analyzed to determine its composition. The spectrum turned out to be featureless, consistent with a dense atmosphere composed primarily of water vapour.
According to Zachory Berta of the Harvard-Smithsonian Center for Astrophysics (CfA), “The Hubble measurements really tip the balance in favor of a steamy atmosphere.”
The results also suggest that GJ1214b has more water and less rock than Earth; internally it may be quite different from our planet.
“The high temperatures and high pressures would form exotic materials like ‘hot ice’ or ‘superfluid water,’ substances that are completely alien to our everyday experience,” Berta said.
It could be said that GJ1214b is something like a wetter version of Venus – with a very hot, thick atmosphere but an atmosphere that is humid and saturated with water, instead of one that is bone dry, acidic and composed mostly of carbon dioxide.
The discovery is also another step closer to finding an alien world that is similar to our own. Water, in its various forms, is already known to be abundant in the universe. It may just be a matter of time before we find another waterworld that is actually like Earth – not just a planet with subsurface oceans like on some icy moons in our solar system, but another Earth with oceans, lakes and rivers on its surface. It is also thought possible that there are planets which are covered completely with water, with no continents or islands anywhere.
In the meantime, GJ1214b has shown once again that, like snowflakes, no two planets are exactly the same, with an almost limitless variety out there waiting to be discovered.
The paper is available here.
This article was first published on Examiner.com.
First there was the recent story about evidence for a possible subsurface ocean on Pluto, of all places. Now there is a new report regarding evidence for complex molecules on its surface, from scientists at Southwest Research Institute and Nebraska Wesleyan University. Little enigmatic Pluto is starting to get even more interesting…
See Universe Today for the full article.
The number of exoplanets being found orbiting other stars continues to grow at an exponential rate; the current number of confirmed exoplanets now stands at 692. Plus the 1,235 additional candidates from Kepler (so far!) that are awaiting confirmation. Now six more have just been added to the confirmed list, a system of three planets found by Kepler and another system of three planets discovered (or re-discovered as outlined below) by the Hubble Space Telescope.
Kepler’s new planetary trio orbit the sun-like star Kepler-18, which is only 10 percent larger than our sun. One of these is a “super-Earth” about twice the diameter and 6.9 times the mass of Earth, called Kepler 18-b. It’s very close to its star, taking only 3.5 days to complete an orbit. The other two, Kepler 18-c and Kepler 18-d, are both Neptune-size worlds about 5.5 times and seven times the diameter of Earth. What’s unusual is that these two planets seem to interacting with each other in a kind of “orbital dance,” alternately tugging and pulling on each other. They take about 7.6 and 14.9 days to complete an orbit respectively, so all three planets are in orbits that are much smaller than Mercury’s in our own solar system.
Meanwhile, the Hubble Space Telescope has imaged three planets orbiting the star HR 8799 (a small but growing number of exoplanets have been directly photographed so far). The interesting part is that these planets were actually known to exist already, but they didn’t show up in the first images taken by Hubble back in 1998. But now, using more advanced techniques, astronomers have been able to tease them out of the data in those original photographs after all. There are actually four known planets orbiting HR 8799, but the fourth one hasn’t been imaged yet. (Note: the Space.com story linked to above mentions two planets photographed in the text, although the image itself shows three and this is the number quoted in other articles about this, such as DiscoveryNews).
This is an exciting time for exoplanet research, with each new discovery adding to our knowledge of the many planetary systems beyond our own; and it wasn’t that long ago when we didn’t know of any…
This article was first published on Examiner.com.