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.
The discoveries of distant exoplanets have become commonplace in the last few years, and now the first exomoon may have just been found.
Finding planets orbiting other stars was difficult enough at first because of the tiny size and dimness of the planets compared to their host stars. But the technology involved continues to improve, and we are now at the threshold of being able to find even smaller moons orbiting some of those planets.
As astronomer David Kipping of Harvard University noted, “This is the first serious candidate from any survey that I am aware of.”
The planet and possible moon are about 1,800 light years from Earth, and this potential first discovery is also an unusual one – the planet is apparently a rogue one, floating free of any star. Other such planets have also been found in recent years and may actually be fairly common. Also, the purported moon is orbiting a long ways out from the planet at an estimated distance of 20 million kilometres (12.4 million miles) with an estimated mass of about half that of Earth. The planet itself is about four times the mass of Jupiter. A planet-sized moon orbiting a gas giant planet, reminiscent of the moon Pandora from the movie Avatar.
The odd nature of this discovery also means that a couple different scenarios are possible: this is either indeed a planet and moon or possibly a brown dwarf star orbited by a Neptune-mass planet, if it is actually farther away than estimated.
The objects were detected using the gravitational microlensing technique; when a planet passes in front of a star, as seen from Earth, the planet’s gravity bends the star’s light. The light is then focused like with a lens which makes the star appear temporarily brighter when it is observed from a particular angle. Unfortunately, this also makes the objects difficult to observe again, so we may never know which answer is correct.
But given the thousands of planets being discovered now, it is reasonable to think that there are a lot of moons out there as well. And if the many moons in just our own solar system are any indication, they probably come in countless varieties, with some being potentially habitable, such as Europa, Enceladus or Titan in our solar system. There might even be one like Pandora…
The published paper is available here.
This article was first published on Examiner.com.
There was a lot of disappointment when it was announced that the crippled Kepler Space Telescope would not be able to continue its search for exoplanets after a malfunction left it unable to stabilize enough to focus properly. There was some comfort in the knowledge that there was still a lot of its original data to go through, and that a few thousand planetary candidates had already been found. But now, it seems that Kepler’s assumed death may have been a bit premature.
Some exciting exoplanet news this week: based on the newest data from the Kepler space telescope, astronomers now estimate that there are billions of potentially habitable planets in our galaxy which are about the same size as Earth and orbit in the habitable zone of their stars, it was announced yesterday.
For the first time, an exoplanet orbiting another star has been discovered which is similar to Earth in size, mass and composition, it was announced today. Astronomers confirmed the finding using data from the Kepler space telescope.
Patchy clouds in the west and clear skies in the east. That is the current weather forecast, not for anywhere on Earth, but for a much more distant world in another solar system. For the first time, astronomers have been able to map cloud patterns on such a far-away exoplanet, it was announced on September 30, 2013.