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.
There aren’t many things that seem to capture imaginations of people around the world, but the prospect of finding life on alien planets is definitely one of them. It’s been a long search, one that a handful of people have devoted their lives to and, in many cases, risked their careers for. It’s a compelling slice of space science, and Lee Billings brings the human side of this search for extraterrestrial life to the fore in his new books Five Billion Years of Solitude.
As Billings points out, we’re currently experiencing an exoplanet boom. It’s only been a little over two decades since scientists first found evidence of a planet orbiting a star other than our own sun and we’re close to confirming the 1,000th exoplanet.
But the search for life on other worlds, or even just finding another planet that could possibly sustain any kind of life, is not a simple matter of calibrating instruments and pointing a telescope at a star. The search for Earth-like exoplanets demands scientists have an intimate knowledge of our own planet, a point Billings brilliantly drives home.
The book follows Billings’ own meetings with some of the leading scientists in the exoplanet hunt – Frank Drake, the first man to use radio telescopes to look for signs of intelligent life in the universe (and the namesake of the Drake Equation); ex-NASA scientist Jim Kastings whose penchant for seeing the big picture rather than details is helping shape the kinds of planets scientists target as habitable exoplanets; and Mike Arthur, whose research into the energy sources on Earth speak to the short span sentient races throughout the universe might be alive.
It’s the lessons Earth teaches us about looking for life on other worlds that anchors this book (though Billings does cover the history of exoplanet research and the current state of exoplanet missions too). Billings highlights how fragile and fleeting our humanity is, contrasting our own history with our planet’s tumultuous past, the rate at which we’re devouring natural resources, and the inevitable eventuality that our Sun will explode and engulf the Earth entirely. Ultimately, the Earth is our benchmark planet when it comes to looking for other worlds, so knowing as much as we can about the Earth increases our chances of recognizing another one, be it in a proto-Earth-like stage, a young Earth-like stage, or a post-apocalyptic-devoid-of-life Earth-like stage.
Running through the book is the question of what finding another Earth, teeming with life or simply capable of supporting life, might do to us. If we find life, it would be incredible, especially if it were sentient life with a grasp of some kind of advanced technology. It would mean we’re neither rare nor special, but also that we’re not alone. Similarly not finding life would be equally important. It would drive home our unique place and the fact that our preservation is up to us alone.
Nothing make you feel quite as small as thinking about distant exoplanets orbiting other stars unfathomable distances away. But Billings manages to bring this mind-boggling branch of astronomy down to an accessible level. Weaving science into compelling narratives, he leaves you with a better understanding of our own planet, a deeper appreciation of just how amazing it is that we’re here, and a sudden desire to see a massive telescope launched with the sole purpose of finding other terrestrial planets.
Image credit: Penguin Group (right), ESO