NASA Discovers Hundreds of New Earth-like Planets‎
Kepler Space Telescope has Discovered Earth-like Worlds



 
NASA Discovers Hundreds of New Earth-like Planets
Kepler Space Telescope has Discovered Earth-like Worlds

Scientists from the American space agency NASA say they have discovered over a hundred new planets in distant solar systems.

The majority of planets found outside our solar system have been gas giants since they produce more pronounced wobbles in the host stars and are thus more easily detectable.

However, a number of extrasolar planets are suspected to be terrestrial.

In the early 1990s, the first extrasolar planets were discovered orbiting the pulsar PSR B1257+12  with masses of 0.02, 4.3, and 3.9 times that of Earth's.

They were discovered by accident: their transit caused interruptions in the pulsar's radio emissions (had they not been orbiting around a pulsar, they would not have been found).

Craft Detects Hundreds of Planets with Alien Potential

The scientific objective of the Kepler Mission is to explore the structure and diversity of planetary systems.

This is achieved by surveying a large sample of stars to:
  1. Determine the percentage of terrestrial and larger planets there are in or near the habitable zone of a wide variety of stars;
  2. Determine the distribution of sizes and shapes of the orbits of these planets;
  3. Estimate how many planets there are in multiple-star systems;
  4. Determine the variety of orbit sizes and planet reflectivities, sizes, masses and densities of short-period giant planets;
  5. Identify additional members of each discovered planetary system using other techniques; and
  6. Determine the properties of those stars that harbor planetary systems.
 
The majority of planets found outside our solar system have been gas giants since they produce more pronounced wobbles in the host stars and are thus more easily detectable.

However, a number of extrasolar planets are suspected to be terrestrial.


 

The Kepler Mission endeavours to discover Earth-like planets orbiting around other stars by observing their transits across the star.

The Kepler spacecraft was launched on March 6th, 2009.

The duration of the mission will need to be about three and a half years long to detect and confirm an Earth-like planet orbiting at an Earth-like distance from the host star.

Kepler will look at just one large area of the sky in the constellations Cygnus and Lyra. Over the course of the mission, the spacecraft will simultaneously measure the variations in the brightness of more than 100,000 stars every 30 minutes, searching for the tiny "winks" in light output that happen when a planet passes in front of its star.

The effect lasts from about an hour to about half a day, depending on the planet’s orbit and the type of star. The mission is designed to detect these changes in the brightness of a star when a planet crosses in front of t, or “transits the star.”

This is called the “transit method” of finding planets. Transits are only seen when a star’s planetary system is nearly perfectly aligned with our line of sight. For a planet in an Earth-size orbit, the chance of it being aligned to produce a transit is less than 1%.


Kepler co-investigator Dimitar Sasselov has just announced that the exoplanet-hunting Kepler Space Telescope has discovered about 140 candidate worlds orbiting other stars that are "like Earth."

This is great news for the NASA team and because they have been so successful in finding Earth-like planets so quickly there are good chances that these types of planets are more abundant then first thought.


A number of other telescopes capable of directly imaging extrasolar terrestrial planets are also on the drawing board. These include the Terrestrial Planet Finder, Space Interferometry Mission, Darwin, New Worlds Mission, and Overwhelmingly Large Telescope.


The Search For Earth-Like Planets

The search for Earth-like planets is reaching a fever-pitch.

Does the evidence so far help shed light on the ancient question: Is the galaxy filled with life, or is Earth just a beautiful, lonely aberration?

At present, Earth provides the only example of an environment that has given rise to the evolution of life.

Highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago and half a billion years later the last common ancestor of all life existed.

The development of photosynthesis allowed the Sun's energy to be harvested directly by life forms; the resultant oxygen accumulated in the atmosphere and formed a layer of ozone in the upper atmosphere.

The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes. True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized the surface of Earth.

But what if things don't work out on this planet or if our itch to explore becomes unbearable at some point in the future
Astronomers have recently found out what kind of galactic real estate might be available to us.

We will have to develop advanced transport to land there, 20 light years away. The question right now: is it worth the trip?



If things don't work out on this planet...

Or if our itch to explore becomes unbearable at some point in the future...

Astronomers have recently found out what kind of galactic real estate might be available to us.

We will have to develop advanced transport to land there, 20 light years away.... But that's for later.

The question right now: is it worth the trip? The destination is a star that you can't see with your naked eye, in the southern constellation Libra, called Gliese 581.


Identified over 40 years ago by the German astronomer Wilhelm Gliese, it's a red dwarf with 31% of the Sun's mass... and only 1.3% of its luminosity. Until recently, the so-called M Stars like Gliese 581 flew below the radar of planet hunters.

They give off so little energy that a planet would have to orbit dangerously close just to get enough heat. Now, these unlikely realms are beginning to show some promise... as their dim light yields to precision technologies...

...as well as supercomputers... honed in the battle to understand global changes on this planet... Earth.

Will we now begin to detect signs of alien life?

Or will these worlds, and the galaxy itself, turn out to be lifeless... and Earth, just a beautiful, lonely aberration? To some, like astronomer and author Carl Sagan, the sheer number and diversity of stars makes it, as he said, "far more likely that the universe is brimming over with life."

Earthlike Planet Gliese 581


This so-called "many worlds" view can be traced back to ancient observers... in China, India, Greece and Egypt. The Qur'an, the Talmud, and many Hindu texts all imagined a universe full of living beings.

In the 16th Century, this view got a boost from astronomer and mathematician Nikolas Copernicus... who came to believe that Earth is not the center of the universe, but revolves around the Sun.

Seven decades after Copernicus, Galileo Galilei used his newly developed telescope to show that our Sun was just one among countless other stars in the universe.

By the modern era, the "many worlds" view held sway in scientific circles. A variety of thinkers considered what and who inhabited worlds beyond our own. From Martians desperate to get off their planet... to alien invaders intent on launching pre-emptive strikes against ours... or simple life forms on an evolutionary track to complexity.

But other thinkers have been struck by a different view. The Greek philosophers Aristotle and Ptolemy believed that humans and Earth are unique. With the spread of Christianity, this Ptolemaic system became widely accepted.

The latest variation on this theme is what's called the "Rare Earth" hypothesis. It holds that Earth and sophisticated life were the result of fortuitous circumstances that may not be easy to find again in our galaxy.

Does the current search for planets shed light on this debate... sending it in one direction or the other?


So far, our only good reference for recognizing an Earth-like planet is... Earth. It does have some fortuitous characteristics... it's dense, it's rocky -- with a complex make-up of minerals and organic compounds -- and it has lots and lots of water.

It's also got a nearly circular orbit around the Sun, at a distance that allows liquid water to flow... not too close and not too far away, in the so-called "Habitable Zone." That's defined as the range of distance from a parent star that a planet would need to maintain surface temperatures between the freezing and boiling points of water.

Of course, that depends on the size of the planet, the make-up of its atmosphere, and a host of other factors.

And whether the parent star is large; medium like the Sun; or small.

Some scientists also believe we live in a "Galactic Habitable Zone." We're close enough to the galactic center to be infused with heavy elements generated by countless stellar explosions over the eons... But far enough away from deadly gamma radiation that roars out of the center.

If there is a galactic habitable zone... it's thought to lie 26,000 light years from the center... about where we are... give or take about 6,000 light years.