50 Billion Alien Planets May Inhabit Our Milky Way Galaxy

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c/p from
www.space.com

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Our galaxy could be home to a whopping 50 billion planets, say scientists working on NASA's Kepler planet-hunting telescope.

While Kepler hasn't found nearly that many planets — to date it's counted 1,235 candidate planets — that cosmic tally is researchers' best guess, extrapolated from preliminary data. The Kepler spacecraft, which launched in March 2009, is the world's most sophisticated observatory dedicated to studying alien planets.

Kepler scientists presented an update on the spacecraft's findings this month at the annual meeting of the American Association for the Advancement of Science in Washington, D.C.

"I am really delighted to find that we are seeing so many candidates," said William Borucki, Kepler's principal investigator. "It means there's a very rich ocean of planets out there to explore."

Goldilocks planets

Kepler observes a large swath of nearby stars to search for signs that they might harbor planets. Though it can identify candidate planets, these must be confirmed by follow-up observations before they are pronounced fact. [The Strangest Alien Planets]

Of the 1,235 possible planets Kepler has observed so far, 54 appear to be at a Goldilocks-like "just right" distance from their stars where temperatures would be right for liquid water. This region is called the habitable zone, because for a planet to be habitable to alien life, it would probably require water.

Extrapolating to the Milky Way as a whole, the researchers predict that at least 500 million of the galaxy's probable 50 billion planets reside in the habitable zone. That certainly offers a hopeful sign for the existence of life beyond Earth.

Kepler has also identified 68 Earth-size planet candidates in its data set. Scientists think rocky planets like Earth are also the best bets for hosting alien life.

Earth-like planets

Yet to find a truly Earth-like planet — that is, an Earth-sized planet in the habitable zone around its star — Kepler will have to search for much longer than it has so far.

Kepler detects a possible planet by observing the slight dimming of its star's light as the planet passes, or transits, in front. For alien planets with orbits roughly a year long, like Earth's, this transit would occur only once a year, so Kepler would have to watch that star for at least a few years to notice the effect.

Despite the challenge of finding Earth-like worlds, scientists think Kepler is up to the task.

"What we see right now makes me very optimistic that we will find some," Borucki said.

Cosmic census

Kepler's main goal is not just to discover individual planets, but to build up a picture of just how common planets are, the researchers explained.

"What Kepler has found, in fact, is approximately for every two stars we are seeing a planet, or candidate planet," Borucki said. "The number of candidates per star is about 44 percent."

This seeming abundance of planets was far from a foregone conclusion when the mission launched. The first extrasolar planet was discovered in the early 1990s, and the pace of such discoveries has picked up since then, but astronomers are just beginning to get a picture of how widespread alien planets truly are.

To date, astronomers have identified more than 500 alien planets, with Kepler sure to vastly increase that tally once its candidates are confirmed.

"Kepler has identified this bonanza of candidate planets," said Matthew Holman, a Kepler scientist at the Harvard-Smithsonian Center for Astrophysics. "Large numbers of multiple planet systems have been detected."

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This illustration shows all 1,235 of the potential alien planet candidates NASA's Kepler mission has found to date. The planets are pictured crossing front of their host stars, which are all represented to scale.


A photo may be worth 1,000 words, but a new depiction of NASA's Kepler mission is worth 1,235 potential alien planets. Created by a devoted mission scientist, the image takes stock of the Kepler observatory's prolific planet-hunting results so far.

The illustration shows all of Kepler's candidate planets — which await confirmation by follow-up observations — crossing the face of their host stars. This provides scale, and it's also a nod to Kepler's planet-hunting strategy: The spacecraft detects alien worlds by measuring the telltale dips in a star's brightness that occur during these planetary "transits." [See the alien planet graphic]

The graphic is the brainchild of scientist Jason Rowe, who created it in an attempt convey Kepler's exoplanet discoveries to the masses in a clear, concise manner.

The graphic itself has been great to show to people. There is lots of interesting astrophysics that one can present," Rowe, a member of the Kepler team at NASA's Ames Research Center and the SETI (Search for Extraterrestrial Intelligence) Institute, told SPACE.com. "My favorite one so far is that planets can be just as big as some of the smallest stars."

In Rowe's graphic, the parent stars of Kepler's potential alien worlds are arranged by size, with the largest at the top left of the diagram and the smallest at the bottom right. For reference, our own sun is shown sitting by itself, just beneath the top row. Both Jupiter and Earth are depicted transiting the sun in the illustration, researchers said.

To create the graphic, Rowe wrote a program with scientific plotting software, creating synthetic stellar images that were properly scaled to one another

NASA launched the $600 million Kepler observatory in March 2009 to seek out planets circling alien stars.

To do that, the spacecraft is staring continuously at a single patch of the sky, watching for tiny changes in the amount of light coming from every star it sees. Astronomers use other telescopes to follow up Kepler's findings in order to confirm whether or not the candidate stars do, in fact, host exoplanets.

To date, Kepler has discovered 1,235 possible planets, with 54 of those candidates located within the so-called "Goldilocks zone" — that just-right range of distances around a star in which liquid water could exist on a planet's surface.

Based on the amazing wealth of planet candidates from Kepler, astronomers have estimated that our Milky Way galaxy could hold as many as 50 billion alien planets, with 2 billion of those perhaps being about the size of Earth.

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I'm going to post some great pics of a few of these planets. Obviously they are CGI/artist renditions based on current findings, but still are based on facts we didn't have before.

Enjoy!!

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The Smallest

Credit: NASA

This artist's concept of Kepler-10b shows the smallest known exoplanet, announced in January 2011.

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The Former Champ

Credit: ESO/L. Calcada

Gliese 581 e used to hold the title of smallest alien planet. However, it was dethroned in January 2011, with the announcement of Kepler-10b.

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The Biggest

Credit: Jeffrey Hall, Lowell Observatory

The largest exoplanet ever discovered is also one of the strangest and theoretically should not even exist, scientists say. Dubbed TrES-4, the planet is about 1.7 times the size of Jupiter and belongs to a small subclass of so-called puffy planets that have extremely low densities. The planet is located about 1,400 light years away from Earth and zips around its parent star in only three and a half days.

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Closest Alien World to Us

Credit: NASA, ESA, G.F. Benedict (University of Texas, Austin)

Epsilon Eridani b orbits an orange Sun-like star only 10.5 light years away from Earth. It is so close to us telescopes might soon be able to photograph it. It orbits too far away from its star to support liquid water or life as we know it, but scientists predict there are other stars in the system that might be good candidates for alien life.

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Volcanic Nightmare

Credit: ESO/L. Calcada

This planet, CoRoT-7b, was the first confirmed rocky world outside our solar system, but it doesn't look like a particularly pleasant place to live. It is tidally locked to its parent star, sees hellish 4,000 degrees Fahrenheit (2,200 degrees Celsius). It may also rain rocks and be the core of a vaporized gas giant.

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Multiple Sunsets Like Tatooine

Credit: NASA/JPL's Planetquest/Caltech

Luke Skywalker’s home planet of Tatooine in Star Wars had two suns, but that’s paltry compared to a Jupiter-like planet 149 light-years from Earth. This planet has three suns, with the main star similar in mass to our own sun. The triple-star system is known as HD 188753. Like Tatooine, the planet there is likely pretty hot – it orbits very close to the main star, completing one orbit every 3.5 days.

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Coldest and Farthest From Us

Credit: ESO

With a surface temperature of -364 degrees Fahrenheit (-220 degrees Celsius), the extrasolar planet known as OGLE-2005-BLG-390L b is likely the coldest alien world. It is about 5.5 times as massive as Earth and thought to be rocky. It orbits a red dwarf star about 28,000 light-years away, making it the most distant exoplanet currently known.

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Hottest World

Credit: ESA/NASA/Frederic Pont, Geneva University Observatory

A planet called WASP-12b is the hottest planet ever discovered (about 4,000 degrees Fahrenheit, or 2,200 degrees Celsius), and orbits its star closer than any other known world. It orbits its star one every Earth day at a distance of about 2 million miles (3.4 million km). WASP-12b is a gaseous planet, about 1.5 times the mass of Jupiter, and almost twice the size. It is 870 light-years from Earth

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Super-Earth

Credit: ESO

Astronomers are finding many worlds now in a category of worlds called Super-Earths, which are between 2 and 10 times the mass of our own Earth. Some scientists think such worlds could be more susceptible to forming the conditions for life because their cores are hot and would be conducive to geological upheaval through volcanism and plate tectonics.

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Oldest Alien Planet

Credit: NASA and H. Richer (U. British Columbia)

The oldest known planet is a primeval world 12.7 billion years old that formed more than 8 billion years before Earth and only 2 billion years after the Big Bang. The discovery suggested planets are very common in the universe and raised the prospect that life began far sooner than most scientists ever imagined.

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The Youngest Known Exoplanet

Credit: NASA

The youngest exoplanet yet discovered is less than 1 million years old and orbits Coku Tau 4, a star 420 light-years away. Astronomers inferred the planet’s presence from an enormous hole in the dusty disk that girdles the star. The hole is 10 times the size of Earth’s orbit around the Sun and probably caused by the planet clearing a space in the dust as it orbits the star.

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The Puffiest

Credit: David A. Aguilar/Harvard-Smithsonian Center for Astrophysics

A planet lighter than a ball of cork is one of the puffiest alien planets known to date. Called HAT-P-1, the planet is about half as massive as Jupiter but about 1.76 times wider-or 24 percent larger than predicted by theory. It could float in water, if there was a tub large enough to hold it.

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Super Neptune

Credit: David A. Aguilar, CFA

While Neptune has a diameter 3.8 times that of Earth and a mass 17 times Earth's, the new world (named HAT-P-11b) is 4.7 times the size of Earth and has 25 Earth masses. The newfound world orbits very close to its star, revolving once every 4.88 days. As a result, it is baked to a temperature of around 1100 degrees F. The star itself is about three-fourths the size of our Sun and somewhat cooler.

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Tilted World

Credit: NASA. ESA, amd G. Bacon (STScI)

Most planets orbit in a plane that corresponds to their parent star's equator. But XO-3b orbits with a crazy tilt of 37 degrees from its star's equator. The only other known example of such an oddly angled orbit was Pluto, until its demotion to dwarf planet status. There is, however, a planet known to orbit backwards around its parent star.

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Fastest Planet

Credit: NASA, ESA, A. Schaller (for STScI)

SWEEPS-10 orbits its parent star from a distance of only 740,000 miles, so close that one year on the planet happens every 10 hours. The exoplanet belongs to a new class of zippy exoplanets called ultra-short-period planets (USPPs), which have orbits of less than a day.

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Waterworld

Credit: David A. Aguilar, CFA

The extrasolar planet GJ 1214b is a rocky planet rich in water that sits about 40 light-years away. It orbits a red dwarf star. It is the only known "Super-Earth" exoplanet — worlds that have masses between Earth and Neptune — with a confirmed atmosphere. The planet is about three times the size of Earth and about 6.5 times as massive. Researchers think it is likely a water world with a solid center.

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Atmosphere Detected

Credit: ESA, NASA and G. Tinetti

Astronomers have been able to detect the atmospheres around several exoplanets, including HD 189733b – one of the first alien words to have its atmosphere sniffed to determine its composition. Glowing methane, which can be produced naturally or be a biological byproduct, has been detected on the planet.

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Endangered World

Credit: CARREAU/ESA/Nature

When astronomers observed WASP-18b, they may have seen it in the cosmic moment before its death. This planet, possibly an ill-fated world, whips around its star in less than one Earth day. Scientists think that this speed coupled with the planet's heft yields strong gravitational tugs that can alter the planets orbit. If the planet orbits faster than its star spins, it should gradually be moving inward towards its sun, and its doom.

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Most Habitable

Credit: ESO

One of the several planets within the Gliese 581 star system, called Gliese 581 d, may be one of the most potentially habitable alien worlds known. It is about 8 times the mass of Earth, and located in an orbit just right for liquid water to exist on the surface. Water is a key ingredient for life as we know it. Gliese 581 is a red dwarf star 20.5 light-years from Earth

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Densest Planet

Credit: ESO/OAMP

One of the densest exoplanet to date is a world known as COROT-exo-3b. It is about the size of Jupiter, but 20 times that planet’s mass, making it about twice as dense as lead. Scientists have not ruled out that the COROT-exo-3b may be a brown dwarf, or failed star.

[pantyhoselover]

love the pictures keep up the great work