Astronomical controversies

life that does not originate from Earth

probabilistic argument to estimate the number of alien civilizations in our galaxy

life on the planet Mars

disproven exoplanet

phrase attributed to Galileo Galilei on being forced to recant his scientific view

any Solar System planet that might orbit the Sun beyond Neptune

Öpik–Oort Comet Cloud hypothetical planet

history and evolution of the term planet

hypothesis that alien life has not been discovered because alien civilizations are silent and very cautious

human discovery of the planet Neptune

17th century conflict between Galileo Galilei and the Roman Catholic Church

criterion for a celestial body to be considered a planet

reading of the Book of Genesis by Apollo 8 crewmembers

idea that any intelligent life is destroyed by aliens

Malligyong-1 () is a type of North Korean reconnaissance satellite. Designed for imaging surveillance capability of several countries, Malligyong-1 has been launched three times onboard Chollima-1 launch vehicle, the last of which, occurred on 21 November 2023, was successful. ==Description== Malligyong-1 is North Korea's first spy satellite. It is in a sun-synchronous orbit at about altitude, and will provide a global optical imaging surveillance capability of several countries. Malligyong-1 is estimated to be long and have a mass of about .

any physical cosmological model of the universe that was, or still is, proposed as an alternative to the then-current standard model of cosmology

Controversy over discovery of a dwarf planet

thumb|right|200px|Gamma-ray bursts might have regulated the advent of intelligent life Neocatastrophism is the hypothesis that life-exterminating events such as gamma-ray bursts have acted as a galactic regulation mechanism in the Milky Way upon the emergence of complex life in its habitable zone. It is one of several proposed solutions to the Fermi paradox since it provides a mechanism which would have delayed the advent of intelligent beings in local galaxies near Earth.

the idea that an absence of detectable Von Neumann probes is contrapositive evidence that no intelligent life exists outside of the Solar System