Exoplanets circle stars other than our sun. 4000 were confirmed as of 2019. There are no doubt billions in the Milky Way galaxy. 51 Pegasi was the first star known to have an exoplanet. Geoff Marcy leads the search.
Most exoplanets are large gas balls like Jupiter. But the Kepler Space Telescope also found Earth-size planets, some in their star's habitable zone, where it is neither too hot nor too cold, making liquid water possible. Kepler used the transit method, measuring a star's dimming as a planet crossed in front of it.
Most exoplanets have eccentric orbits, and many orbit close to their stars. Astronomers are looking for an Earth twin, a rocky planet taking about one Earth year to complete its orbit. Kepler 22-b is an Earth-like planet in terms of size and temperature.
Alpha Centauri is the closest star system at 4 light-years. It is a triple star, and Alpha Centauri B has a planet similar to Earth in mass, but too close to the star for life. The planet was detected at the European Southern Observatory in Chile using the radial velocity method. The star's wobble was measured. It is analogous to a big man dancing with a little woman. He twirls her around, but she also moves him. It seems logical that stars closest to our sun would be the best candidates for having Earth-like planets.
Wilhelm Gliese was a German astronomer known for his Catalogue of Nearby Stars, and ESO has located Earth-like planets Gliese 581 C and D orbiting in the habitable zone.
The James Webb Space Telescope will search for biosignature gases in the atmospheres of exoplanets.
Extraterrestrial life -
Astronomers and other scientists are in a desperate search for life beyond Earth. The question "Are we alone?" is more relevant than ever. The field of astrobiology has opened up even though nothing has been found.
If there were organic molecules in the protoplanetary disk around the sun, astrobiologists think there could be life elsewhere in the solar system. They think Jupiter's moon Europa and Saturn's moon Titan may harbor life if there are oceans beneath the ice.
Microbes were found under the ice in Antarctica, causing astrobiologists to ponder the possibility of extraterrestrial life. They think water flowed on Mars and may still exist below the surface. Mars may have been warmer in the past. NASA scientists want to find extraterrestrial life so bad that they jump to conclusions. In some cases, I think they even lie.
SETI (Search for Extraterrestrial Intelligence) uses radio telescopes like the Allen Telescope Array. SETI has failed to detect signals after 6 decades.
Even if there are advanced ET civilizations, they may not transmit in our direction. And even if they do, we may not be able to interpret their signals. Any radio signals would come from the remote past because of the distance involved.
6 elements are basic to life: carbon, oxygen, hydrogen, nitrogen, phosphorus & sulfur. Scientists assume these elements would be basic to alien life and that it would be DNA based. DNA is the hereditary material with a double helix. Some think life elsewhere in the Milky Way or in other galaxies could be based on something other than DNA. Water is a perfect solvent for biochemistry.
Science fiction depicts aliens as having humanoid or reptilian traits. They are described as grey or green with large heads.
The term UFO was coined in 1947, following the Roswell incident and the alleged sighting of flying saucers by Kenneth Arnold. Ufologists claim the U.S. government is involved in a cover-up. They want disclosure while citing the secrecy of Nevada's Area 51. Conspiracy theories abound!
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.”
When asked if he believed in UFOs, President Trump replied, "Not particularly."
The ancient aliens of Erich von Daniken and Giorgio Tsoukalos are a blend of space age mythology, folklore & science fiction!
Searching for ET -
Astrobiolgy is a scam! There is no such thing. Why are we searching for extraterrestrial life? If microbes were found on Mars, would we be better off? Would we be any less alone? There is also the idea that alien life might prove hostile. Science-fiction movies have proliferated since The Thing and The Day The Earth Stood Still, and movie-goers tend to be gullible. Twenty-first century Americans are willing to go into space even while the Third World colonizes the U.S.
Jupiter's moon Europa is said to have an ocean below its ice. The brown streaks are believed to be oceanic salts that reached the surface. NASA dreamers envision aquatic life on Europa and are developing a probe. Naturally, the dreamers want money! The Europa Clipper will cost an estimated $4 billion and spend 6 years in flight. I have become suspicious of NASA and now think life exists only on this planet.
NASA sees Saturn's moon Enceladus as a possible abode for life. They think there is an ocean heated by Saturn's gravity twisting the moon. In their minds, the presence of water, organic compounds & an energy source equals life. I think of Fred Hoyle, who compared such genesis to a tornado passing through a junkyard and assembling a jumbo jet. NASA wants our money and wants to keep its jobs.
Proxima b is a rocky Earth-size planet orbiting the red dwarf Proxima Centauri. It is 4 light-years away and believed to orbit in the habitable zone. It would take thousands of years to reach Proxima b. Still, NASA dreams of warp drive. Too much Star Trek!
There is Kepler 452b, an exoplanet 1400 light-years away. It orbits a sun-like star and is similar to Earth in temperature and size. SETI has looked for radio signals. SETI boss Seth Shostak is a voice of reason in this mad search. As for myself, I think we have wasted a lot of money, not just in space but on foreign wars that are not in our national interest. Throw in 60 million abortions since 1973, and America is letting itself be torn apart. It has become a nation of homosexuals, alcoholics & tattooed drug addicts, a nation of dog worshipers where veterans stand on street corners and beg, a nation whose chief concern is whether or not someone is a "racist," a nation hypnotized by horror movies, rap music & endless ball games that have made millionaires of the descendants of slaves.
Finally, there is Trappist-1, a red dwarf star with 7 planets found by the people in Chile. Problem is, life is so rare that trillions of trillions of virtually impossible coincidences must follow in sequence. It happened once!