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Related Concept Videos

Circular Orbits and Critical Velocity for Satellites01:16

Circular Orbits and Critical Velocity for Satellites

The Moon orbits around the Earth. In turn, the Earth (and other planets) orbit the Sun. The space directly above our atmosphere is filled with artificial satellites in orbit. One can examine the circular orbit, the simplest kind of orbit, to understand the relationship between the speed and the period of planets and satellites with respect to their positions and the bodies that they orbit.
Nicolaus Copernicus (1473-1543) first suggested that the Earth and all other planets orbit the Sun in...
Kepler's First Law of Planetary Motion01:10

Kepler's First Law of Planetary Motion

In the early 17th century, German astronomer and mathematician Johannes Kepler postulated three laws for the motion of planets in the solar system. He formulated his first two laws based on the observations of his forebears, Nikolaus Copernicus and Tycho Brahe.
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Kepler's Second Law of Planetary Motion01:29

Kepler's Second Law of Planetary Motion

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Kepler's Third Law of Planetary Motion01:18

Kepler's Third Law of Planetary Motion

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Related Experiment Video

Updated: Jul 5, 2026

Scattering And Absorption of Light in Planetary Regoliths
11:34

Scattering And Absorption of Light in Planetary Regoliths

Published on: July 1, 2019

Quasars at 25.

V Trimble, L Woltjer

    Science (New York, N.Y.)
    |October 10, 1986
    PubMed
    Summary
    This summary is machine-generated.

    Astronomers agree that accreting massive black holes power quasars. Despite ongoing debate on the exact physics, these quasars remain crucial for probing the distant universe.

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    Area of Science:

    • Astronomy and astrophysics
    • Cosmology

    Background:

    • The first optical identification of a radio star (3C 48) occurred a quarter century ago.
    • There is broad consensus that quasars are powered by accretion onto massive black holes.

    Purpose of the Study:

    • To explore the energy conversion processes in quasars.
    • To highlight the utility of quasars as cosmological probes.

    Main Methods:

    • Observational astronomy
    • Theoretical astrophysics

    Main Results:

    • General agreement exists on the fundamental energy source of quasars.
    • Detailed physical mechanisms of energy conversion are still under investigation.

    Conclusions:

    • Massive black hole accretion is the accepted quasar energy source.
    • Quasars are valuable tools for studying the early universe and distant phenomena.