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Extraterrestrial life,alien life,or colloquially simply aliens is life which does not originate from Earth. No extraterrestrial life has yet been conclusively detected. Such life might range from simple forms such as prokaryotes to intelligent beings,possibly bringing forth civilizations that might be far more advanced than humanity. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology.
Sir Fred Hoyle (24 June 1915 –20 August 2001) was an English astronomer who formulated the theory of stellar nucleosynthesis and was one of the authors of the influential B2FH paper. He also held controversial stances on other scientific matters—in particular his rejection of the "Big Bang" theory (a term coined by him on BBC Radio) in favor of the "steady-state model",and his promotion of panspermia as the origin of life on Earth. He spent most of his working life at the Institute of Astronomy at Cambridge and served as its director for six years.
Venus is the second planet from the Sun. It is a rocky planet with the densest atmosphere of all the rocky bodies in the Solar System,and the closest in mass and size to its orbital neighbour Earth. Orbiting inferiorly,it always appears close to the Sun in Earth's sky,as either a "morning star" or an "evening star". While this is also true for Mercury,Venus appears more prominent,since it is the third brightest object in Earth's sky after the Moon and the Sun. Venus has historically been a common and important object for humans,in both their cultures and astronomy.
A terrestrial planet,telluric planet,or rocky planet,is a planet that is composed primarily of silicate rocks or metals. Within the Solar System,the terrestrial planets accepted by the IAU are the inner planets closest to the Sun:Mercury,Venus,Earth and Mars. Among astronomers who use the geophysical definition of a planet,two or three planetary-mass satellites –Earth's Moon,Io,and sometimes Europa –may also be considered terrestrial planets. The large rocky asteroids Pallas and Vesta are sometimes included as well,albeit rarely. The terms "terrestrial planet" and "telluric planet" are derived from Latin words for Earth,as these planets are,in terms of structure,Earth-like. Terrestrial planets are generally studied by geologists,astronomers,and geophysicists.
Phosphine (IUPAC name:phosphane) is a colorless,flammable,highly toxic compound with the chemical formula PH3,classed as a pnictogen hydride. Pure phosphine is odorless,but technical grade samples have a highly unpleasant odor like rotting fish,due to the presence of substituted phosphine and diphosphane (P2H4). With traces of P2H4 present,PH3 is spontaneously flammable in air (pyrophoric),burning with a luminous flame. Phosphine is a highly toxic respiratory poison,and is immediately dangerous to life or health at 50 ppm. Phosphine has a trigonal pyramidal structure.
The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile,which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The array has been constructed on the 5,000 m (16,000 ft) elevation Chajnantor plateau –near the Llano de Chajnantor Observatory and the Atacama Pathfinder Experiment. This location was chosen for its high elevation and low humidity,factors which are crucial to reduce noise and decrease signal attenuation due to Earth's atmosphere. ALMA provides insight on star birth during the early Stelliferous era and detailed imaging of local star and planet formation.
The James Clerk Maxwell Telescope (JCMT) is a submillimetre-wavelength radio telescope at Mauna Kea Observatory in Hawaii,US. The telescope is near the summit of Mauna Kea at 13,425 feet (4,092 m). Its primary mirror is 15 metres across:it is the largest single-dish telescope that operates in submillimetre wavelengths of the electromagnetic spectrum. Scientists use it to study the Solar System,interstellar dust and gas,and distant galaxies.
The Black Cloud is a 1957 science fiction novel by British astrophysicist Fred Hoyle. It details the arrival of an enormous cloud of gas that enters the Solar System and appears about to destroy most of the life on Earth by blocking the Sun's radiation.
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The atmosphere of Venus is primarily of supercritical carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K,and the pressure is 93 bar (1,350 psi),roughly the pressure found 900 m (3,000 ft) under water on Earth. The Venusian atmosphere supports opaque clouds of sulfuric acid,making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging. Aside from carbon dioxide,the other main component is nitrogen. Other chemical compounds are present only in trace amounts.
Sara Seager is a Canadian–American astronomer and planetary scientist. She is a professor at the Massachusetts Institute of Technology and is known for her work on extrasolar planets and their atmospheres. She is the author of two textbooks on these topics,and has been recognized for her research by Popular Science,Discover Magazine,Nature,and TIME Magazine. Seager was awarded a MacArthur Fellowship in 2013 citing her theoretical work on detecting chemical signatures on exoplanet atmospheres and developing low-cost space observatories to observe planetary transits.
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The history of scientific thought about the formation and evolution of the Solar System began with the Copernican Revolution. The first recorded use of the term "Solar System" dates from 1704. Since the seventeenth century,philosophers and scientists have been forming hypotheses concerning the origins of our Solar System and the Moon and attempting to predict how the Solar System would change in the future. RenéDescartes was the first to hypothesize on the beginning of the Solar System;however,more scientists joined the discussion in the eighteenth century,forming the groundwork for later hypotheses on the topic. Later,particularly in the twentieth century,a variety of hypotheses began to build up,including the now-commonly accepted nebular hypothesis.
The possibility of life on Venus is a subject of interest in astrobiology due to Venus's proximity and similarities to Earth. To date,no definitive evidence has been found of past or present life there. In the early 1960s,studies conducted via spacecraft demonstrated that the current Venusian environment is extreme compared to Earth's. Studies continue to question whether life could have existed on the planet's surface before a runaway greenhouse effect took hold,and whether a relict biosphere could persist high in the modern Venusian atmosphere.
Water activity (aw) is the partial vapor pressure of water in a solution divided by the standard state partial vapor pressure of water. In the field of food science,the standard state is most often defined as pure water at the same temperature. Using this particular definition,pure distilled water has a water activity of exactly one. Water activity is the thermodynamic activity of water as solvent and the relative humidity of the surrounding air after equilibration. As temperature increases,aw typically increases,except in some products with crystalline salt or sugar.
An Earth analog, also called an Earth analogue,Earth twin,or second Earth, is a planet or moon with environmental conditions similar to those found on Earth. The term Earth-like planet is also used,but this term may refer to any terrestrial planet.
Victoria Suzanne Meadows is a Professor with the Astronomy Department and Director of the Astrobiology Program at the University of Washington. She is also the Principal Investigator for the NASA Astrobiology Institute's Virtual Planetary Laboratory Lead Team and the chair of the NAI Focus Group on Habitability and Astronomical Biosignatures (HAB). The research direction of the team is to create computer models that can be used to understand planet formation,stability and orbital evolution,and to simulate the environment and spectra of planets that can potentially be habitable.
The Fred Hoyle Medal and Prize was established in 2008 by the Institute of Physics of London for distinguished contributions to astrophysics,gravitational physics or cosmology. The medal is named after astronomer Fred Hoyle who formulated the theory of stellar nucleosynthesis. The medal is made of silver and accompanied by a prize and a certificate. The medal was awarded biennially from 2008 to 2016. It has been awarded annually since 2017.
Clara Sousa-Silva is a research scientist at Center for Astrophysics | Harvard &Smithsonian. Sousa-Silva is an expert on phosphine. She has contributed to investigations of the possibility of life on Venus,working with Jane Greaves and others. Sousa-Silva also directs the Harvard-MIT Student Research Mentoring Program,which pairs high school students with astronomers to conduct research.
References
- ↑ Rincon, Paul (2 April 2008). "Astronomers see 'youngest planet'". BBC News . Retrieved 3 July 2017.
- Highfield, Roger (2 April 2008). "Baby planet found around star HL Tau". Daily Telegraph . Retrieved 3 July 2017. - ↑ "Fred Hoyle Medal and Prize recipients". Awards. Institute of Physics . Retrieved 15 September 2020.
- ↑ "Paucity of phosphorus hints at precarious path for extraterrestrial life". Phys.org . 4 April 2018. Retrieved 5 April 2018.
- "Alien life may be more unlikely than previously thought, according to new study". The Daily Telegraph . 5 April 2018. Retrieved 5 April 2018. - ↑ Perkins, Sid (14 September 2020). "'Curious and unexplained.' Gas spotted in Venus's atmosphere is also spewed by microbes on Earth". Science . Retrieved 14 September 2020.
- ↑ Chang, Kenneth; Stirone, Shannon (22 June 2021). "Life on Venus? The Picture Gets Cloudier". New York Times. Retrieved 6 March 2022.
