Where are they? That question asked the famous physicist and genius Enrico Fermi during a discussion with his colleagues when having a lunch break from their daily work with developing the nuclear bomb at Los Alamos National Laboratory in 1950.
There are billions of stars in the milky way that are similar to our sun and many of them are billions of years older than our sun.
Some of these stars should with high probability have Earth-like planets and some may have civilizations with more advanced technology than us. Should not this life has been able to spread all over the galaxy at this time? So why can we not see any trace of aliens here? This paradox is called Fermi's paradox. Some popular explanations to the paradox are:
Image Credit: The digital artist
Search for extraterrestrial intelligence SETI is a term for scientific searches for intelligent extraterrestrial life. And several SETI program and initiatives have in decades been monitoring space in search for signals from other civilizations on exoplanets.
In the previous article, I wrote about Breakthrough Starshot that is founded by Russian billionaire Yuri Milner. He also found the project called Breakthrough Listen that are using large radio telescopes for listening for signals. One of the founders of SETI is the American astronomer and astrophysicist Frank Drake.
Frank Drake is well known for the equation from 1961 that bears his name. Drake’s Equation is a probabilistic equation that could be used to estimate the number of active communicative extraterrestrial civilizations in our galaxy.
The Drake equation is: N=R* fp ne fl fi fc L
N = number of advanced technological civilizations that could communicate
R* = The yearly rate of formation of stars suitable for developing life in our galaxy
fp = The fraction that has exoplanets
ne = The average number of habitable planets per planet system
fl =The fraction that will develop life
fi = The fraction that will develop intelligent life
fc = The fraction that will develop advanced technological civilizations
L = The average life length of advanced technological civilization
We cannot use Drake's equation to make estimates. Because we don’t have enough data/knowledge yet to give any values or really good guesses for these terms.
The rate of star formation is not a constant over time. When the universe was younger stars where being format at a higher rate. Today we could estimate R* to between 5-20 new stars per year in the Milky Way. We have when this article is written discovered 3875 exoplanets and that 55 could be habitable.
Even our closest star has exoplanets. Which give a higher estimate for fp and n e We don’t know anything about fl the only thing we know that is that life has developed on earth. If we find organisms on other celestial bodies in our solar- system like Mars or Jupiter/Saturn's moons it would indicate that life could be common on other solar systems.
Check out our interactive star map that shows the discovered exoplanets that have an earth-similarity index bigger than 0.7 and could possibly support life.
Our closest star is Alpha Centauri is just 4.37 light-years away. Alpha Centauri is not just a star it is a solar system that contains three stars Rigil Kentaurus, Toliman and Proxima Centauri. Rigil Kentaurus is just like our sun a spectral class type G star. Toliman is a class K star orange to red color. Together they form a binary star system, Proxima Centauri is a small and faint red dwarf and is closest to our sun. Proxima Centauri has an Earth-like exoplanet in the habitable zone Proxima Centauri b. The planet was discovered in August 2016 by ESO Very large telescopes. It was discovered by the wobble method. Just like other planets orbiting red dwarfs Proxima b is tidily looked. It is the eternal day on one side of the planet and night on the other side. The planet does not transit its star and that makes it difficult to get any reliable information about the planet atmosphere and composition. But there is a chance that the planet has an ocean and an atmosphere. Red dwarfs are known to have deadly radiation that could have a negative effect on life.
As the star is just around the corner 4.2 light-years away could we travel to the planet and look for aliens? The New Horizons probe, which lifted off in 2006 on a mission to Pluto and the Kuiper Belt moves at a speed of 84000 km / h it will only take us 54 thousand years to reach Proxima b at that speed.
A research and engineering project using solar sail will be capable of making that journey in just twenty-five years. So how does solar sail works? The sails are being pushed by the massless particles in light called photons. Due to the wave-particle duality of quantum particles, light could be described both as particles and waves and particles have momentum. Even though a photon has zero rest mass, it has energy. This could be derived from the relativistic equation E2 = (mc2)2 +(pc)2 if the mass is zero then E = pc. Most people would recognize the equation where the momentum is zero as Einsteins most famous equation E = mc2
The photoelectric effect that Einstein got his Nobel prize for in 1921 is also based on this phenomena. Where light shining on some material it will cause emission electrons. This effect is proportional to the frequency of the light f=c/λ.
Where the energy is E=hc/λ and the momentum p =h/λ, where λ is the wavelength of the light and h is a universal constant called Planck's constant 6.62607004 × 10-34 m2 kg / s and c the speed of light in a vacuum.
By using very tiny nano craft that just weights a gram and the sails would be four meters wide but just a couple 100 atoms thick. By then using high energy lasers blasting a 100-gigawatt beam on one solar sail from earth could accelerate the craft up to 20% of light speed within an hour. In space, there is no friction so the craft will keep its speed for the rest of the journey to Proxima b
Breakthrough Starshot initiative is planning to send hundreds or even thousands of nano crafts. The technology is not developed yet and it is very difficult to make the sails hold. Russian billionaire Yuri Milner and other investors have paid $100 million to cover the first 10 years of development. So it is not just science fiction it could be possible in a near future.
All data in this application comes from PHL's Exoplanets Catalog
Just now the in the Atacama desert, on the top of the mountain Cerro Armazones, north Chile. A new generation of land-based optical telescopes is being built.
It is built by the European Southern Observatory ESO that is a European astronomic organization with several telescopes already located on the southern hemisphere.
In north Chile they already have this generation optical telescopes in operation called Very Large Telescopes VLT. The new generation telescopes will be operational in 2024 and it is called Extremely Large Telescopes ELT. Astronomers imagination is not the best when it comes to the naming of their gadgets, but rest assured that these gadgets will live up to their name.
So how much better will ELT be than VLT?
Will we be able to make new discoveries about the universe?
Will we be able to find new Earth-like exoplanets with these telescopes?
VLT consist of four large telescopes width a diameter of 8.2 meters. The telescopes are located in a formation. They can work both independently and together. The total mirror surface has a diameter of a 16-meter telescope when they are coordinated. VLT is the largest Telescopes on earth.
Some important discoveries made by VLT telescopes so far has been:
ELT image credit:
ELT is an optical reflector telescope. The primary mirror will be 39.3 m in diameter composed of 798 hexagonal segments. The mirror will have a light absorption area of 978 m². Above this huge reflector, there is also a 4.2-meter diameter secondary mirror.
ELT will be much larger than VLT, it will gather 13 times more light. ELT will be able to correct for atmospheric distortions. The telescope will be able to take from earth 16 times sharper images than the Hubble Telescope that is in space.
Consider the impressive resume of VLT and Hubble we will have many existing reports about discoveries when ELT gets fully operational.
The main task of ELT will be to look for an exoplanet. By measurements of the wobbling movements, stars show because planets orbit around them, but also take direct images of large Jovians. Perhaps it will be possible for the telescope to characterize the atmospheres of the planets, and to take direct images of planets of Earth's size.
Read more at ESO
Peter van de Kamp was a professor of astronomy at Swarthmore College from 1937 until 1972.
Already in the forties, he was looking for exoplanets. He gave lectures on the topic do stars have planets for astronomers groups in the fifties. In 1963 he made a big announcement, that he finally found an exoplanet. A large jovian was orbiting Barnard star with an orbit on 25 years. Barnard star is the closest single star system from earth only six light years away. Only Alpha Centauri a system that consists of three stars and a habitable exoplanet is closer. Barnard star is a very small red dwarf, with only 0.14 the mass of the sun and 15% of the sun's radius. Barnard's star is also a very fast moving star, the fastest on the sky, and in 10000 years it will be the star that is closed to our sun.
The claimed discovery was made with the wobble method, de Kamp detected with his instruments that it was a periodic distortion in the star motion. Over decades he took thousands of images of the star. Making these measurements this was very hard precision work as the shift in the blurry light of star was tiny as a sand corn, This discovery was, of course, a big sensation at the time de Kamp appeared in many big newspapers and in television shows. Later he also discovered another Jupiter sized planet orbiting the star with an orbit of 12 years.
Later some skeptical voices about these discoveries were raised from the science community. Astronomer George Gatewood analyzed de Kamps photos and could not make the same conclusions. Other planet discovered around other stars by de Kamp had an identical change of motion, and the anomaly often occurred after the lens was removed or cleaned. Decades later much better instruments could not make the same discoveries as de Kamp did. The discoveries were not real it was errors made with the instruments and in the analysis of data. Van de Kamp did not accept that his life work was wrong and kept defending his research and started to repeat his measurements. Van de Kamp died in 1995 at aged 93 he never found an exoplanet. The first confirmed detection of Exoplanets was a couple years earlier in 1992.
Peter van de Kamp was not really completely wrong about Barnard's star it probably does has a planet.
Last week on 14 November 2018 Ignasi Ribas team at the Institute of Space Studies of Catalonia and the Institute of Space Sciences, CSIC in Spain. Announced that after careful studies that with 99 percent certainty there is an exoplanet orbiting Barnard star. The planet that was discovered with the wobble method lies around 0.4 astronomical units from the star. The planet is a cold icy super earth with a size 3.2 times earth. The planet is called Barnard’s star b, and with mean temperatures at -170 C, the planet is likely not habitable. The planet is still not classified as confirmed exoplanet more analysis needs to be made to 100 percent rule out any natural stellar variations. There are also indications that there are other planets further away from the star.