One of the primary goals in the search for exoplanets is to, hopefully, find an Earth analog or “Earth twin,” an alien world similar to our own. That search is still ongoing, but getting closer – yesterday NASA announced a new exoplanetary discovery that could be described as “Earth’s bigger and older cousin” – Kepler-452b.
Discovering new exoplanets has become rather routine in the last few years, but determining just what conditions exist on any of them is naturally more difficult, since they are so far away. But astronomers are making advances in this area as well, and now they have found the first evidence of changing temperatures – and possible volcanic activity – on a distant super-Earth exoplanet.
The search for, and discovery of, exoplanets orbiting other stars has become a full-fledged endeavour in recent years, with thousands found so far and more being discovered practically every week. Now, NASA wants to take it a big step further by establishing a coalition of research groups and disciplines tasked specifically with this purpose.
The search for exoplanets may one day get a lot more glittery. It sounds a bit like science fiction, but a new NASA proposal called Orbiting Rainbows would use glitter-like materials to help image some of those far-away worlds, which could enable high-resolution imaging at a fraction of the cost.
Researchers at Cornell University are taking a new approach to the search for alien life: looking for habitable planets older than Earth, “old Earth analogues,” which may be nearing the end of their habitable lifetimes. Astronomers would search for biosignatures from worlds much older than Earth, where lifeforms are dying off due to circumstances such as the planet’s star expanding in its old age, gradually heating the planet to a point where life is no longer possible.
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.
With exoplanets now being discovered by the thousands, and estimated to be in the billions in our galaxy alone, attention is naturally turning to how astronomers might be able to search for evidence of life on any of those far-away worlds. Now, a team of scientists is taking a novel approach to doing just that, by creating a colourful catalogue of reflection signatures of various life forms on Earth. The new database and research was just published in the March 16 Proceedings of the National Academy of Sciences.
While exoplanets are now being discovered by the thousands, it is still a painstaking process to determine any specific details about them, since they are so incredibly far away. However, astronomers have been devising new techniques to do just that, including one that makes it easier to analyze the property of clouds on some of these distant worlds.
Three more exoplanets have just been found, adding to a long and rapidly growing list, but their location makes them a bit more unique – they orbit three different stars in a star cluster rather than other isolated stars in the galaxy, and one of those stars is a “solar twin” which is almost exactly identical to our own Sun. The results were announced yesterday, January 15, 2014, by the European Southern Observatory (ESO).
The discovery was made using the HARPS planet-finding instrument on ESO’s 3.6-metre telescope at the La Silla Observatory in Chile. The planets are located in the star cluster Messier 67, which is about 2,500 light-years away in the constellation Cancer and contains about 500 known stars.
Although thousands of exoplanets have now been found so far, only a small number of those are orbiting stars in a star cluster. Astronomers had thought that perhaps planets would be less common around stars in more densely packed star clusters, but the new results suggest that planets are probably common around stars in clusters as well, but are more difficult to detect.
According to Luca Pasquini of ESO in Garching, Germany, “These new results show that planets in open star clusters are about as common as they are around isolated stars – but they are not easy to detect. The new results are in contrast to earlier work that failed to find cluster planets, but agrees with some other more recent observations. We are continuing to observe this cluster to find how stars with and without planets differ in mass and chemical makeup.”
Two of the stars, and the one in particular, are similar to our own Sun, while the third is a red giant star. All three of the planets are much larger than Earth, with two of them having a mass about one-third that of Jupiter and the third with a mass larger than Jupiter. The first two orbit their stars in seven and five days respectively, while the third orbits in 122 days. None of them are in the habitable zone of their stars, orbiting close to their stars and therefore much hotter than Earth.
The findings indicate that many more planets may be waiting to be discovered in star clusters as well. As Anna Brucalassi of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany adds, “In the Messier 67 star cluster the stars are all about the same age and composition as the Sun. This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars.”
Confirming this would be an exciting discovery, since most stars are born in similar clusters. The more they look, the more astronomers are finding planets around all different types of stars, and even free-floating planets with no star at all. To find out that they are probably also abundant in star clusters as well, may have been surprising a few years ago, but now, not so much it seems.
This article was first published on Examiner.com.
With the number of known exoplanets being discovered now numbering in the thousands (and estimated to be in the billions in our galaxy alone), astronomers have already found an amazingly diverse plethora of worlds. Some of the most common are the “super-Earths,” rocky planets which are larger than Earth but smaller than Neptune or Uranus. It has been thought by scientists that such worlds might often be true water worlds, with their surfaces completely covered by water with no land visible at all, causing less stable climates than on our home planet.
But now new studies suggest that these planets might tend to be more Earth-like after all. Two scientists, Nicolas B. Cowan from Northwestern University and Dorian Abbot from the University of Chicago have announced a new model for super-Earths which shows that ones which are tectonically active would probably store most of their water in their mantles, producing both oceans and continents and subsequently a more Earth-like climate. This would likely be true regardless of the mass of the planet(s).
As Cowan explains:
“Are the surfaces of super-Earths totally dry or covered in water? We tackled this question by applying known geophysics to astronomy.
Super-Earths are expected to have deep oceans that will overflow their basins and inundate the entire surface, but we show this logic to be flawed. Terrestrial planets have significant amounts of water in their interior. Super-Earths are likely to have shallow oceans to go along with their shallow ocean basins.”
Plate tectonics allow a water cycle to exist between the oceans above and the mantle below, which helps to stabilize the climate. Even for such rocky planets larger than Earth, this could still create both oceans and continents, due to increased gravity and seafloor pressure.
“We can put 80 times more water on a super-Earth and still have its surface look like Earth,” Cowan said. “These massive planets have enormous seafloor pressure, and this force pushes water into the mantle.”
On Earth, the carbon cycle, essential for life as we know it on our planet, is also regulated by surface temperatures, producing a stabilizing feedback, a sort of thermostat on geological timescales.
As Abbot notes, “Such a feedback probably can’t exist in a waterworld, which means they should have a much smaller habitable zone. By making super-Earths 80 times more likely to have exposed continents, we’ve dramatically improved their odds of having an Earth-like climate.”
The findings suggest that super-Earths are much more likely to have an Earth-like surface than previously thought. The new model depends on these planets have plate tectonics and a similar amount of water, or more, stored in their mantles, which are still two unknowns at this point. But the odds are probably good that at least some of them will, increasing the chances of life of some sort on these worlds.
The findings were presented on Jan. 7 at the 223rd meeting of the American Astronomical Society (AAS) annual meeting in Washington, D.C.
This article was first published on Examiner.com.