Exoplanets are on the cutting edge of astronomy. These are planets circling stars other than our sun. 853 have been confirmed as of December 1, 2012. There are no doubt billions in the Milky Way galaxy.

51 Pegasi was the first main-sequence star around which an exoplanet was discovered. That was in 1995.

Geoff Marcy and his team at the University of California Berkeley are at the forefront of exoplanet research.

I wonder why everything is a "team" now. What happened to giants like Copernicus and Hubble?

So far, it has been mostly Super-Earths and large gas planets called Hot Jupiters. But Kepler has found Earth-size planets, and some may be in their star's habitable zone, where it is not too hot and not too cold and liquid water may exist.

Most exoplanets have elongated, eccentric orbits. Many orbit very close to their stars.

Scientists are looking for an Earth twin, a rocky planet taking about one Earth year to complete its orbit.

Scientists at the European Southern Observatory in Chile claim to have found Earth-like planets in Gliese 581 c and d. They lie in or near their star's habitable zone. Gliese 581 in Libra is 20 light years away.

NASA's Kepler Space Telescope uses the transit method. It measures a star's dimming as planets cross in front of it.

Kepler 22-b may be an Earth-like planet in terms of size and temperature. It is in the Goldilocks zone at 600 light years.

Alpha Centauri is the closest star to us at 4.4 light years. It is a triple star, and an exoplanet is orbiting a Centauri B. It is similar to Earth in mass but too near its parent star for life. The planet was spotted at the ESO using the radial velocity method. The star's wobble caused by the planet's gravitational tug was detected. It is analogous to a large man dancing with a small woman. He may whirl her around, but she will also have an effect on him. It makes sense that stars near our sun would be the best candidates for having Earth-like planets.

It is clear that our solar system is not unique, and the search is already on for extragalactic planets. These would be planets in galaxies such as M31.

Extraterrestrial life -
Astronomers and other scientists are in a desperate search for life beyond our own planet. The question "Are we alone?" is more relevant now than at any time in history. Curiosity is looking for signs of life on Mars. The field of astrobiology is opening even though nothing has been found.

If organic molecules were in the protoplanetary disk surrounding the sun, then life may exist somewhere in the solar system. Jupiter's moon Europa may be suitable for life as well as Saturn's moons Titan and Enceladus. There may be oceans under ice.

It is thought that liquid water one flowed on Mars and may still exist beneath its surface. Mars may have been warmer in the past. No life has been confirmed.

NASA scientists want to find extraterrestrial life so bad that they tend to jump to conclusions. I would guess in some cases they even lie.

SETI (Search for Extraterrestrial Intelligence) uses radio telescopes like Arecibo in Puerto Rico. SETI has failed to detect intelligent radio signals in more than five decades of trying.

Even if there are advanced ET civilizations, they may not be transmitting in our direction. And if they are, we may not be able to interpret their signals. Also, because of the distances involved, any radio activity would come from the remote past.

Six elements are basic to life on earth: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. It is assumed that these elements would be at the basis of alien life. Scientists also assume that alien life would be DNA based. Water provides a solvent in which biochemistry takes place.

Maybe life elsewhere in the Milky Way or in other galaxies would not be based on carbon and DNA. DNA is the hereditary material in cells known for its double helix.

Microbes were found below ice in Antarctica’s Lake Vida. The discovery of life in this extremely cold habitat makes us ponder the potential for extraterrestrial life on moons like Europa.

Science fiction depicts aliens with humanoid or reptilian features. Aliens are described as green or grey and having large heads.

The term UFO was coined in 1947 after the Roswell incident and the alleged sighting of flying saucers by Kenneth Arnold. Conspiracy theories abound. Ufologists claim that the government is involved in a cover-up. They want "disclosure" while citing the secrecy of Nevada's Area 51.

The White House Office of Science and Technology Policy posted this on the White House website:

“The U.S. government has no evidence that life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race. In addition, there is no credible information to suggest that any evidence is being hidden from the public eye.”

The ancient aliens of Giorgio Tsoukalos and Erich von Daniken are a mix of space age mythology, folklore and science fiction.