An artist's illustration of an Earth-like planet. The search for planets that are similar to Earth is one of NASA's main goals. Many planets have already been discovered orbiting other stars, but so far only larger planets (the size of Jupiter or larger) have been found. New missions are being planned by NASA which will be able to detect smaller Earth-sized planets. Some of these missions will also try to detect signs of life on these planets by studying emissions in their atmospheres.


Astronomers See Second Earth in the Making

03 October 2007

Astronomers have spotted evidence of a second Earth being built around a distant star 424 light-years away.

Using NASA's Spitzer Space Telescope, astronomers have spotted a huge belt of warm dust swirling around a young star called HD 113766 that is just slightly larger than our sun. The dust belt, which scientists suspect is clumping together to form planets, is located in the middle of the star system's terrestrial habitable zone where temperatures are moderate enough to sustain liquid water. Scientists estimate there is enough material in the belt to form a Mars-sized world or larger.

At approximately 10 million years old, the star is just the right age for forming rocky planets, the researchers say. Their finding will be detailed in an upcoming issue of Astrophysical Journal.

"The timing for this system to be building an Earth is very good," said study team member Carey Lisse of the Johns Hopkins University Applied Physics Laboratory in Baltimore, Md.

If the star system were too young, the planet-forming disk would be full of gas, and it would be making gas-giant planets like Jupiter instead. If it were too old, Spitzer would have spotted rocky planets that had long ago formed.

The star system also has the right mix of dusty materials in its disk to form an Earth-like planet, Lisse said.

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Giant telescope to scan sky for planets like ours


 SANTA CRUZ DE TENERIFE, Canary Islands — One of the world's most powerful telescopes will begin spying on the universe on Friday, using its 34-foot wide mirror to search for planets similar to our own from a mountaintop on one of Spain's Canary Islands.

Perched atop a 7,800 foot peak on the Atlantic island of La Palma, the Great Canary Telescope will receive its so-called "first light" — when the telescope is pointed toward the sky and focusses on the North Star — Friday night.

"The GTC will be able to reach the weakest and most distant celestial objects of the universe," the Canary Islands Astrophysics Institute said in a statement.

"One of its aims is to find planets similar to ours in other solar systems," the institute added.

The telescope will have 36 hexagonal mirrors, of which 12 are already in place.

Once the telescope has had its first light, the remaining 24 mirrors will be placed and adjusted, and the scope will be fully functional within a year, according to the institute.

"With this (telescope) it will possible to capture the birth of new stars, to study more profoundly the characteristics of the black holes or to decipher the chemical components generated by the Big Bang," the institute said in a statement.
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For more information:

Fact mirrors fiction in search for space life
Hunting new Earths and the edge of the universe
Supertelescope to cast an eye on distant worlds and seek origins of the universe


How many stars are there in the Universe?


What is a galaxy? How many stars in a galaxy? How many stars/galaxies in the Universe?

What is a galaxy?
Galaxies are large systems of stars, dust and gas bound together by gravitational force. They are elliptical, spiral or irregular in shape. Our Sun is part of a spiral galaxy called the Milky Way, and lies about two-thirds of the way out from the centre to the edge.

How many stars in a galaxy?
The best estimates suggest that the Milky Way contains about 500 thousand million stars and a total mass equivalent to 1.9 million million Suns.
Galaxies vary in size considerably. For example, giant elliptical galaxies may have up to 100 times the mass of the Milky Way (or the equivalent of 1900 million million Suns) whereas the recently discovered Ultra-Compact Dwarf galaxies may have just a few tens of millions of stars.

How many stars and galaxies in the universe?
The best estimates suggest that there are at least 70 thousand million million million (70 sextillion or 7 × 1022) stars in the Universe. The Universe probably contains more than 100 thousand million (100 billion or 1011) galaxies.

Find out more:
Stars (index of fact files about stars)
Galaxies (fact file)

For more information:

  1. There may be 3 times as many stars in the universe as we thought NEW!
  2. Imperfect Estimate Claims Universe Has 70 Sextillion Stars
  3. How many stars are there? More than you thought NEW!
  4. How many stars are there in the Universe?
  5. Trillions of Planets Could Have Life 
  6. Star survey reaches 70 sextillion
  7. Study predicts trillions of planets
Sunlike Stars
  1. First Super-Earths Discovered Orbiting Sun-Like Stars
  2. First Picture of Likely Planet Around a Sun-Like Star
  3. Possible First Photo of Planet Around Sun-Like Star
  4. Young Planet Orbits Sun-Like Star
  5. Astronomers Discover Sun's Twin at McDonald Observatory
  6. Many planets may have double suns
  7. Sun's Baby Twin Spotted
  8. Habitable Planet Possible Around Nearby Star System
  9. Scientists find planet with 3 suns
  10. Nasa finds sun-like star
  11. 2,000 Sun-like stars out to 150 light-years
  12. Planets Around Sun-Like Stars
  13. Planets with Two Suns Likely Common
  14. Newfound Star Smaller than Some Planets
  15. Space telescopes discover more of sun's sisters NEW!
  16. Astronomers Find Sun's Twin NEW!
  17. Sun-like star's 'oddball' planet NEW!
Where in the Universe do we live?
Our place in the universe. This figure illustrates our cosmic address. The Earth is one of the nine planets in our solar systems, our solar system is one among more than 400 billion star systems in the Milky Way Galaxy; the Milky Way is one of the two largest of about 30 galaxies in the Local Group; the Local Group lies near the outskirts of the Local Supercluster; and the local Supercluster fades into the background of structure throughout the universe.



Newfound Planet Has Earth-Like Orbit

August 2 2007

A planet outside our solar system with a year roughly equal to Earth's has been discovered around a dying, red giant star.

Only about 10 red giant stars are known to harbor planets; the new solar system is among the most distant of these.

Our sun will become a red giant in a few billion years, likely vaporizing Earth.

The finding, to be detailed in the November issue of Astrophysical Journal, was made by a team led by Penn State astronomer Alex Wolszczan, who in 1992 discovered the first planets outside our solar system around a deadly, radiation-spewing star.

A bloated parent

The new planet, spotted using the Hobby-Eberly Telescope at the McDonald Observatory in West Texas, circles its bloated parent star every 360 days and is located about 300 light-years away, in the constellation Perseus.

The red giant star is twice as massive and about 10 times larger than the sun. Its planet is about the size of Jupiter or larger and was discovered using the so-called wobble technique, in which astronomers look for slight wiggles in a star's motion created by the gravitational tug of orbiting planets.

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Astronomers Find First Habitable Earth-Like Planet

SOURCE: Space Daily
April 26, 2007

Astronomers have discovered the most Earth-like planet outside our Solar System to date, an exoplanet with a radius only 50 percent larger than the Earth and capable of having liquid water.

Using the ESO 3.6-m telescope, a team of Swiss, French and Portuguese scientists discovered a super-Earth about 5 times the mass of the Earth that orbits a red dwarf, already known to harbour a Neptune-mass planet. The astronomers have also strong evidence for the presence of a third planet with a mass about 8 Earth masses.

This exoplanet - as astronomers call planets around a star other than the Sun - is the smallest ever found up to now [1] and it completes a full orbit in 13 days. It is 14 times closer to its star than the Earth is from the Sun.

However, given that its host star, the red dwarf Gliese 581 [2], is smaller and colder than the Sun - and thus less luminous - the planet nevertheless lies in the habitable zone, the region around a star where water could be liquid!

"We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius, and water would thus be liquid," explains Stephane Udry, from the Geneva Observatory (Switzerland) and lead-author of the paper reporting the result.

"Moreover, its radius should be only 1.5 times the Earth's radius, and models predict that the planet should be either rocky - like our Earth - or covered with oceans," he adds.

"Liquid water is critical to life as we know it," avows Xavier Delfosse, a member of the team from Grenoble University (France). "Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extra-terrestrial life. On the treasure map of the Universe, one would be tempted to mark this planet with an X."

Read More:

For more information:

  1. New 'super-Earth' found in space
  2. Swiss Scientist: Search for Life Next
  3. Found 20 light years away: the New Earth
  4. Earth-like planet found that may support life
  5. Planet of Promise: Small, Rocky World Could Harbor Life
  6. New Earthlike planet discovered Gliese 581c See Video!
  7. Astronomers Find First Earth-like Planet in Habitable Zone See Video!
Gliese 581
In April 2007 around this red dwarf the first Earth-like exoplanet has been discovered, Gliese 581 c. This has 1.5 times the diameter and 5 times the mass of Earth and orbits its star every 13 days in a distance of 0.07 AU. Probably the planet has a surface temperature which allows liquid water. This discovery is a real sensation and an important step to the finding of alien life.

Another planet d with 8 times Earth's mass, an orbit period of 84 days and a distance of 0.25 AU, probably has life-friendly temperatures as well.

In April 2009 Gliese 581 e was discovered, the so far lightest exoplanet with only 1.9 times the mass of Earth. With an obit period of 3.14 days it is too close to its star for life.
Already longer known is a planet b with 16.6 times the mass of Earth, which orbits the star every 5.4 days.

Constellation: Libra
Age: 4.3 billion years
Distance: 20.4 light-years
Spectral class: M3.5
Visual magnitude: 10.56
Luminosity: 0.002 * Sun
Mass: 0.33 * Sun
Radial velocity: -9.4 km/sec

The extrasolar planet Gliese 581c is slightly larger than earth and orbits in the habitable zone of its star. The "Twilight Zone" near the boundary between day and night might afford a temperate climate. The sun would be fixed in place near the horizon, however, and plants might tend to grow in waves, struggling for sunlight, with fallow regions in the shadowlands between crests of forest vegetation. See Video!
Digital artwork Don Dixon


The Shocking Colors of Alien Plants

SOURCE: Scientific American Magazine
Article By Nancy Y. Kiang
April 2008

The prospect of finding extraterrestrial life is no longer the domain of science fiction or UFO hunters. Rather than waiting for aliens to come to us, we are looking for them. We may not find technologically advanced civilizations, but we can look for the physical and chemical signs of fundamental life processes: “biosignatures.”

Beyond the solar system, astronomers have discovered more than 200 worlds orbiting other stars, socalled extrasolar planets. Although we have not been able to tell whether these planets harbor life, it is only a matter of time now.

Last July astronomers confirmed the presence of water vapor on an extrasolar planet by observing the passage of starlight through the planet’s atmosphere. The world’s space agencies are now developing telescopes that will search for signs of life on Earth-size planets by observing the planets’ light spectra.

Photosynthesis, in particular, could produce very conspicuous biosignatures. How plausible is it for photosynthesis to arise on another planet? Very. On Earth, the process is so successful that it is the foundation for nearly all life. Although some organisms live off the heat and methane of oceanic hydrothermal vents, the rich ecosystems on the planet’s surface all depend on sunlight.

Photosynthetic biosignatures could be of two kinds: biologically generated atmospheric gases such as oxygen and its product, ozone; and surface colors that indicate the presence of specialized pigments such as green chlorophyll. The idea of looking for such pigments has a long history. A century ago astronomers sought to attribute the seasonal darkening of Mars to the growth of vegetation. They studied the spectrum of light reflected off the surface for signs of green plants.

One difficulty with this strategy was evident to writer H. G. Wells, who imagined a different scenario in The War of the Worlds: “The vegetable kingdom in Mars, instead of having green for a dominant colour, is of a vivid blood-red tint.” Although we now know that Mars has no surface vegetation (the darkening is caused by dust storms), Wells was prescient in speculating that photosynthetic organisms on another planet might not be green.

Even Earth has a diversity of photosynthetic organisms besides green plants. Some land plants have red leaves, and underwater algae and photosynthetic bacteria come in a rainbow of colors. Purple bacteria soak up solar infrared radiation as well as visible light. So what will dominate on another planet? And how will we know when we see it?

The answers depend on the details of how alien photosynthesis adapts to light from a parent star of a different type than our sun, filtered through an atmosphere that may not have the same composition as Earth’s.

Harvesting Light

In trying to figure out how photosynthesis might operate on other planets, the first step is to explain it on Earth. The energy spectrum of sunlight at Earth’s surface peaks in the blue-green, so scientists have long scratched their heads about why plants reflect green, thereby wasting what appears to be the best available light. The answer is that photosynthesis does not depend on the total amount of light energy but on the energy per photon and the number of photons that make up the light.

Whereas blue photons carry more energy than red ones, the sun emits more of the red kind. Plants use blue photons for their quality and red photons for their quantity. The green photons that lie in between have neither the energy nor the numbers, so plants have adapted to absorb fewer of them.

The basic photosynthetic process, which fixes one carbon atom (obtained from carbon dioxide, CO2) into a simple sugar molecule, requires a minimum of eight photons. It takes one photon to split an oxygen-hydrogen bond in water (H2O) and thereby to obtain an electron for biochemical reactions. A total of four such bonds must be broken to create an oxygen molecule (O2). Each of those photons is matched by at least one additional photon for a second type of reaction to form the sugar. Each photon must have a minimum amount of energy to drive the reactions.

The way plants harvest sunlight is a marvel of nature. Photosynthetic pigments such as chlorophyll are not isolated molecules. They operate in a network like an array of antennas, each tuned to pick out photons of particular wavelengths. Chlorophyll preferentially absorbs red and blue light, and carotenoid pigments (which produce the vibrant reds and yellows of fall foliage) pick up a slightly different shade of blue.

All this energy gets funneled to a special chlorophyll molecule at a chemical reaction center, which splits water and releases oxygen.

The funneling process is the key to which colors the pigments select. The complex of molecules at the reaction center can perform chemical reactions only if it receives a red photon or the equivalent amount of energy in some other form. To take advantage of blue photons, the antenna pigments work in concert to convert the high energy (from blue photons) to a lower energy (redder), like a series of step-down transformers that reduces the 100,000 volts of electric power lines to the 120 or 240 volts of a wall outlet.

The process begins when a blue photon hits a blue-absorbing pigment and energizes one of the electrons in the molecule. When that electron drops back down to its original state, it releases this energy—but because of energy losses to heat and vibrations, it releases less energy than it absorbed.

The pigment molecule releases its energy not in the form of another photon but in the form of an electrical interaction with another pigment molecule that is able to absorb energy at that lower level. This pigment, in turn, releases an even lower amount of energy, and so the process continues until the original blue photon energy has been downgraded to red.

For the full article and more astounding imagery, you can purchase the April 2008 issue of Scientific American online. Click here for details.

Full article:

To learn more:
  1. Colorful Worlds: Plants on Other Planets Might Not Be Green
  2. NASA Predicts Non-green Plants on Other Planets
  3. Purple Palm Trees on Alien Worlds?
  4. Colors of Alien Plants
  5. See Images