Hothouse 'super-Earth' 55 Cancri e (seen in an artist's impression) is one of the planets that could be studied by Twinkle, if the telescope launches.
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.
Even with about 2,000 confirmed planets found outside the solar system, we know so little about them. What are they made of? Are their atmospheres habitable? What weather exists?
It will take a whole new generation of “big-eyed” telescopes to learn more, such as the James Webb Space Telescope that launches in 2018. But here’s a twist — one European team says it can do exoplanet science for a lot less.
With a budget of just 50 million pounds ($79 million), the Twinkle satellite team plans to launch into low-Earth orbit in three to four years if it can get the funding. There, it will study the infrared (heat) signatures of at least 100 nearby worlds a few hundred light-years away. This will be possible even with a tiny mirror of 50 centimeters (20 inches) compared to a larger telescope like Hubble (2.4 meters/8 feet), the lead scientist told Discovery News.
“We have identified a niche of science that could be done very well even with a relatively more modest instrument,” said Giovanna Tinetti, an astrophysicist at University College London. Because the planets will be hothouse worlds that are relatively close by Earth, their infrared signatures are so strong that astronomers can infer the presence of molecules, clouds, weather and climate even in a small telescope, she said.
While new planets are discovered all the time, one possible target could be 55 Cancri e, she said. It orbits a star much like our sun, but is so close by that its surface burns at a blistering 3,700 degrees Fahrenheit (2,300 Celsius). The planet is so small that it’s hard to know much about its structure, but at least one published paper suggests it is rich in carbon — an element associated with life, despite the hostile environment.
But money (as always) will be the challenge. Twinkle is much cheaper than a previous planet-studying mission called EChO that Tinetti and collaborators proposed to the European Space Agency in 2011, a half-billion Euro ($0.57 billion) mission that was not selected. Key differences include not sending Twinkle out to Lagrangian point L2 (1.5 million kilometers or 932,000 miles from Earth), a smaller telescope and a narrower wavelength range, using commercial off-the-shelf components, and suggesting “trades” to international scientific organizations such as providing money for telescope time. Funding is ongoing, but there is a commercial partner involved – Surrey Satellite Technology Ltd. – that has participated in numerous space missions.
While Twinkle is much smaller than other counterparts, its heavyweight contribution will be looking at a range of visible and infrared emissions (0.5 microns to 5 microns) from planets around very bright stars which are not the sweet spot of the James Webb Space Telescope and the Spitzer Space Telescope, Tinetti said. The project is also working to drum up support on the educational side by promoting to K-12 institutions in the United Kingdom.