An artist's rendition of Gliese 1214 b traveling in front of its star, shown in blue light.
Image: Kepler-16b is the first exoplanet disc
Exquisite Exoplanetary Art
Sept. 19, 2011 --
They're alien worlds orbiting distant stars far out of reach of detailed imaging by even our most advanced telescopes. And yet, day after day, we see vivid imaginings of these extrasolar planets with the help of the most talented space artists. The definition of an extrasolar planet -- or "exoplanet" -- is simply a planetary body orbiting a star beyond our solar system, and nearly 700 of these extrasolar worlds have been discovered so far (plus hundreds more "candidate" worlds). With the help of NASA's Kepler space telescope, the ESO's High Accuracy Radial velocity Planet Searcher (HARPS), French COROT space telescope and various other advanced exoplanet-hunting observatories, we are getting very good at detecting these worlds, but to glean some of the detail, we depend on artist's interpretations of fuzzy astronomical images and spectral analyses. That's the way it will be until we build a vast telescope that can directly image an exoplanet's atmosphere or physically travel to an alien star system. So, with the flurry of recent exoplanet discoveries, Discovery News has collected a few of the dazzling pieces of art born from one of the most profound searches mankind has ever carried out: the search for alien worlds orbiting other stars; a journey that may ultimately turn up a true "Earth-like" world.
Image: An exoplanet passes in front of (or "t
As an exoplanet passes in front of its star as viewed from Earth, a very slight dip in starlight brightness is detected. Observatories such as NASA's Kepler space telescope use this "transit method" to great effect, constantly detecting new worlds.
Some exoplanets orbit close to their parent stars. Due to their close proximity and generally large size, worlds known as "hot Jupiters" are easier to spot than their smaller, more distant-orbiting cousins.
Image: An artist's impression of Gliese 581d,
The primary thrust of exoplanet hunting is to find small, rocky worlds that orbit within their stars' "habitable zones." The habitable zone, also known as the "Goldilocks zone," is the region surrounding a star that is neither too hot nor too cold. At this sweet spot, liquid water may exist on the exoplanet's surface. Where there's water, there's the potential for life.
Credit: David A. Aguilar (CfA)
Usually, exoplanet hunters look for the slight dimming of a star or a star's "wobble" to detect the presence of an exoplanet. However, in the case of Kepler-19c, its presence has been detected by analyzing its gravitational pull on another exoplanet, Kepler-19b. Kepler-19c is therefore the Phantom Menace of the exoplanet world.
Image: A cool world some distance from its st
The habitable zone seems to be the pinnacle of extraterrestrial living. If you're an alien with similar needs to life on Earth, then you'll need liquid water. If your planet exists outside your star's habitable zone, well, you're in trouble. Either your world will be frozen like a block of ice, or boiling like a kettle. But say if your world had the ability to extend your star's habitable zone? There may be some atmospheric factors that might keep water in a comfy liquid state. Even better, if you like deserts, a dry world could even be oddly beneficial.
Image: A "hot Jupiter" and its two hypothetic
Planets with a global magnetic field, like Earth, have some dazzling interactions with the winds emanating from their stars. The high-energy particles bombard the planet's atmosphere after being channeled by the magnetism. A wonderful auroral lightshow ensues. But say if there's an exoplanet, with a magnetosphere, orbiting really close to its star? Well, stand back! The entire world would become engulfed in a dancing show, 100-1000 times brighter than anything we see on Earth.
Credit: Adrian Mann, <a href="http://www.bisb
"Candidate" exoplanets are often mentioned, especially when talking about detections by the Kepler space telescope. But what does this mean? As a world passes in front of its star, slightly dimming the starlight, this isn't considered a "confirmed" exoplanet detection. To make sure that signal is real, more orbital passes of the exoplanet need to be logged before a bona fide discovery can be announced. Until then, these preliminary detections are called exoplanet candidates.
Image: An exoplanet being destroyed by X-rays
Angry Suns, Naked Planets
Exoplanets come in all sizes and all states of chaos. Some might have wonky orbits, others might be getting naked. Other times, they're simply being ripped apart by X-rays blasted from their parent star. Bummer.
Image: Artist's impression shows HD 85512b, a
Super-Earths get a lot of press. Mainly because "Earth" is mentioned. Sadly, most of these worlds are likely completely different to anything we'd call "Earth." And you can forget calling the vast majority of them "Earth-like." It's simply a size thing -- they're bigger than Earth, yet a lot smaller than Jupiter, hence their name, "super-Earth." Easy.
Credit: Adrian Mann, <a href="http://www.bisb
For now, we have to make do with artist's renditions of exoplanets for us to visualize how they may look in their alien star systems. However, plans are afoot to send an unmanned probe to an interstellar destination. Although these plans may be several decades off, seeing close-up photographs of these truly alien worlds will be well worth the wait.
A nearby alien planet six times the size of the Earth is covered with a water-rich atmosphere that includes a strange "plasma form" of water, scientists say.
Astronomers have determined that the atmosphere of super-Earth Gliese 1214 b is likely water-rich. However, this exoplanet is no Earth twin. The high temperature and density of the planet give it an atmosphere that differs dramatically from Earth.
"As the temperature and pressure are so high, water is not in a usual form (vapor, liquid, or solid), but in an ionic or plasma form at the bottom the atmosphere — namely the interior — of Gliese 1214 b," principle investigator Norio Narita of the National Astronomical Observatory of Japan told SPACE.com by email. (The Strangest Alien Planets (Gallery))
Using two instruments on the Subaru Telescope in Mauna Kea, Hawaii, scientists studied the scattering of light from the planet. Combining their results with previous observations led the astronomers to conclude that the atmosphere contained significant amounts of water.
A wellspring of exotic water
Located 40 light-years from the solar system in the constellation Ophiuchus, the planet orbits its cooler, low-mass M-type star once every 38 hours, 70 times closer than Earth is to the sun.
Its close proximity means that its temperatures reach up to 540 degrees Fahrenheit (280 degrees Celsius). Six times as massive as Earth, Gliese 1214 b is less than three times as wide, falling between the Earth and the solar system's ice giants Uranus and Neptune in size.
The high temperatures of the planet may affect the hydrogen and carbon chemistry, which could produce a haze in the atmosphere. But determining if the weather is clear or perpetually overcast on Gliese 1214 b would be difficult, as differences in the two atmospheres are small.
"At high pressure and high temperature, the behavior of water is quite different from that on the Earth," Narita said. "At the bottom of the water-rich atmosphere of Gliese 1214 b, water should be a super-critical fluid."
Artist's rendition of the relationship between the composition of the atmosphere and transmitted colors of light of an alien planet.NAOJ
Unlike terrestrial planets, the super-Earth doesn't have a solid surface, making the height of the atmosphere difficult to define. Instead, atmospheric scientists introduce a concept called the scale height, a height determined by changes in the increase or decrease of atmospheric pressure by a set amount. On Earth, the scale height is about 6 miles (10 kilometers), while on Gliese 1214 b it is three times deeper, according to Narita.
"We predict that ionic or plasma water can be seen deep inside the planet," Narita said. "However, we may not be able to find hot 'ice' — high pressure-ices — inside of Gliese 1214 b."
Originally discovered in by the MEarth Project, which tracks more than 2,000 low-mass stars in search of planets, Gliese 1214 b was confirmed by the European Space Agency's High Accuracy Radial velocity Planet Searcher in Chile.
As a planet travels across the face of its star, or transits, it blocks the star's light slightly, allowing scientists to determine characteristics about it based on how much the light dims.
Though water is often considered a necessary ingredient for life by scientists, Narita doesn't think that the super-Earth will be promising due to its close orbit, which lies within the star's habitable zone, the region where liquid water can exist.
"Although water vapor can exist in the atmosphere, liquid water — namely oceans — would not exist on the surface of this planet," he said. "So unfortunately, we do not think this planet would be habitable."
Narita's team intends to continue studying the planet with spectroscopic observations in the visible wavelength, and anticipates that other astronomers will follow.
This article originally appeared on SPACE.com. More from Space.com:
Super-Earth Planet: Potentially Habitable Alien World Explained (Infographic)
9 Exoplanets That Could Host Alien Life
Alien Planet Quiz: Are You an Exoplanet Expert?
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