galactic background emission
51Search for extraterrestrial intelligence — The search for extraterrestrial intelligence is sometimes abbreviated as SETI. For other uses, see SETI (disambiguation). Screen shot of the screensaver for SETI@home, a distributed computing project in which volunteers donate idle computer power …
52Future of an expanding universe — Big Freeze redirects here. For other uses, see Big Freeze (disambiguation). Physical cosmology Univ …
53Observational cosmology — Physical cosmology Universe · Big Bang …
54Gamma ray — Gamma rays (denoted as gamma;) are a form of electromagnetic radiation or light emission of frequencies produced by sub atomic particle interactions, such as electron positron annihilation or radioactive decay. Gamma rays are generally… …
55Antimatter — For other uses, see Antimatter (disambiguation). Antimatter …
56Fermi paradox — The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations.The extreme age of the universe and its …
57Planetary nebula — A planetary nebula is an emission nebula consisting of a glowing shell of gas and plasma formed by certain types of stars when they die. The name originated in the 18th century because of their similarity in appearance to giant planets when… …
58Astronomical object — Celestial object and Celestial body redirect here. For other uses, see Celestial (disambiguation). This article is about naturally occurring objects. For artificial objects, see Satellite. Astronomical objects or celestial objects are naturally… …
59Pulsar — Pulsars are highly magnetized rotating neutron stars that emit a beam of electromagnetic radiation in the form of radio waves. Their observed periods range from 1.4 ms to 8.5 s. [ M.D. Young, R.N. Manchester and S. Johnston. A radio pulsar with… …
60Large Magellanic Cloud — The Large Magellanic Cloud Observation data (J2000 epoch) Constellation Dorado/Mensa …
