Kepler's Planet-Hunting Mission May Be Over
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.
NASA’s planet-hunting Kepler space telescope has shut down due to an apparent problem with its positioning system, suspending indefinitely its science mission, officials said Wednesday.
So far, attempts to coax the telescope back into operation have been fruitless. Two of the observatory’s four spinning reaction wheels, needed to properly point Kepler at its targets, are now no longer working.
As designed, the telescope needs at least three of its four wheels spinning to steady itself for the delicate task of finding planets circling distant stars.
“We need three wheels in service to give us the pointing precision that is necessary to find planets,” Kepler lead scientist William Borucki, with NASA’s Ames Research Center in California, told reporters on a conference call Wednesday.
Kepler, which was launched in 2009, lost its first positioning wheel last year.
“People are definitely saddened by the loss of another reaction wheel. It certainly is not good news for the mission, which has been performing so well and had so much promise for doing even better,” deputy project manager Charles Sobeck, with the Ames Research Center, told Discovery News.
Kepler works by detecting slight dips in the amount of starlight coming from about 100,000 target stars in the constellations Cygnus and Lyra. Follow-up observations and analysis then determine if the dips are caused by planets passing in front of their parent stars, relative to the telescope’s point of view, or other phenomena.
So far, Kepler scientists have found and confirmed 130 extrasolar planets, and are in the process of assessing another 2,700 potential candidates.
The goal of the mission is to find Earth-sized planets positioned at the right distance from their parent stars for liquid water to exist on their surfaces. Liquid water is believed to be necessary for life.
Though the telescope currently isn’t collecting any data, scientists have years of archived observations to analyze.
“Frankly, I’m absolutely delighted that we’ve got all this data, that we have been so successful, that we have found so many thousands of planetary candidates,” Borucki told Discovery News.
“The mission was designed for four years, it operated four years. It gave us excellent data for four years. So I’m very delighted,” he said.
“On the other hand I would have been even happier if it continued another four years because we’d have better data about more stars, about smaller planets and we’d have more planets that we’d probably find in the habitable zone, so that would have been in some sense frosting on the cake, but we have an excellent cake right now.”
In addition to trying to resurrect Kepler’s failed wheel, engineers and scientists will be assessing if the telescope, which still has fuel for maneuvering, can be put to use for other astronomical studies.