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• The flux due to a light emitting object measured at the observer (in most cases, at the earth or a satellite). Observed brightness is proportional to 1 divided by the distance to the object squared. The full moon has a greater observed brightness than the star, Vega, even though Vega has a greater luminosity.

  Lawrence Berkeley National Laboratory's Physics Division - Cite This Source - This Definition
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  Cite Definition for Observed Brightness

  American Psychological Association (APA)

  Observed Brightness. (n.d.). The Universe Adventure Glossary. Retrieved June 10, 2023, from website: http://www.expertglossary.com/definition/observed-brightness.

  Chicago Manual of Style (CMS)

  Observed Brightness. pdgusers.lbl.gov. The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. http://www.expertglossary.com/definition/observed-brightness (accessed: June 10, 2023).

  Modern Language Association (MLA)

  "Observed Brightness." The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. 10 June. 2023 http://www.expertglossary.com/definition/observed-brightness.

• Browse Related Terms: Angular Size, Apparent luminosities, Constant of Proportionality, Dark Matter, Flux, Heavenly Bodies, Intrinsic Luminosity, Inverse Square, Luminosity, Main Sequence Star, Observed Brightness, Parallax, Parsec, Relative Brightness, Standard Candle, Type Ia Supernova, Variable Stars

All > Science > Astronomy > Astrophysics

• The ratio of the average total density of matter to the critical density required to make the universe flat and eventually stop its expansion.

  Lawrence Berkeley National Laboratory's Physics Division - Cite This Source - This Definition
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  Cite Definition for Omega, Ω

  American Psychological Association (APA)

  Omega, Ω. (n.d.). The Universe Adventure Glossary. Retrieved June 10, 2023, from website: http://www.expertglossary.com/definition/omega-Ω.

  Chicago Manual of Style (CMS)

  Omega, Ω. pdgusers.lbl.gov. The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. http://www.expertglossary.com/definition/omega-Ω (accessed: June 10, 2023).

  Modern Language Association (MLA)

  "Omega, Ω." The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. 10 June. 2023 http://www.expertglossary.com/definition/omega-Ω.

• Browse Related Terms: Background Radiation, Closed Universe, COSMIC, Cosmic Microwave Backgroun (CMB), Cosmology, Flat Universe, Flatness Problem, Geocentric, Geometries, Heliocentric, Metastable Energy Density, Omega, Ω, Opaque to Radiation, Open Universe , Ω, Planck Time, Universe, Vacuum Energy

All > Science > Astronomy > Astrophysics

• A condition when radiation is absorbed or scattered many times. For the first 400,000 years the universe was so hot that the matter was ionized and interacted abundantly with radiation, making the universe opaque.

  Lawrence Berkeley National Laboratory's Physics Division - Cite This Source - This Definition
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  Cite Definition for Opaque to Radiation

  American Psychological Association (APA)

  Opaque to Radiation. (n.d.). The Universe Adventure Glossary. Retrieved June 10, 2023, from website: http://www.expertglossary.com/definition/opaque-to-radiation.

  Chicago Manual of Style (CMS)

  Opaque to Radiation. pdgusers.lbl.gov. The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. http://www.expertglossary.com/definition/opaque-to-radiation (accessed: June 10, 2023).

  Modern Language Association (MLA)

  "Opaque to Radiation." The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. 10 June. 2023 http://www.expertglossary.com/definition/opaque-to-radiation.

• Browse Related Terms: Background Radiation, Closed Universe, COSMIC, Cosmic Microwave Backgroun (CMB), Cosmology, Flat Universe, Flatness Problem, Geocentric, Geometries, Heliocentric, Metastable Energy Density, Omega, Ω, Opaque to Radiation, Open Universe , Ω, Planck Time, Universe, Vacuum Energy

All > Science > Astronomy > Astrophysics

• A universe where the geometry of space is curved like an infinite saddle-shaped surface. For universes with only matter, an open universe has less than critical density, < 1, and expands forever.
  Lawrence Berkeley National Laboratory's Physics Division - Cite This Source - This Definition
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  Cite Definition for Open Universe , Ω

  American Psychological Association (APA)

  Open Universe , Ω. (n.d.). The Universe Adventure Glossary. Retrieved June 10, 2023, from website: http://www.expertglossary.com/definition/open-universe-Ω.

  Chicago Manual of Style (CMS)

  Open Universe , Ω. pdgusers.lbl.gov. The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. http://www.expertglossary.com/definition/open-universe-Ω (accessed: June 10, 2023).

  Modern Language Association (MLA)

  "Open Universe , Ω." The Universe Adventure Glossary. Lawrence Berkeley National Laboratory's Physics Division. 10 June. 2023 http://www.expertglossary.com/definition/open-universe-Ω.

• Browse Related Terms: Background Radiation, Closed Universe, COSMIC, Cosmic Microwave Backgroun (CMB), Cosmology, Flat Universe, Flatness Problem, Geocentric, Geometries, Heliocentric, Metastable Energy Density, Omega, Ω, Opaque to Radiation, Open Universe , Ω, Planck Time, Universe, Vacuum Energy