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  2. Elongation (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Elongation_(astronomy)

    The greatest elongation of a given inferior planet occurs when this planet's position, in its orbital path around the Sun, is at tangent to the observer on Earth. Since an inferior planet is well within the area of Earth's orbit around the Sun, observation of its elongation should not pose that much a challenge (compared to deep-sky objects, for example).

  3. Cosmic distance ladder - Wikipedia

    en.wikipedia.org/wiki/Cosmic_distance_ladder

    It is made from parts of the Yale–Columbia Refractor telescope (1924) damaged when the 2003 Canberra bushfires burned out the Mount Stromlo Observatory; at Questacon, Canberra. [ 1 ] At the base of the ladder are fundamental distance measurements, in which distances are determined directly, with no physical assumptions about the nature of the ...

  4. Parallactic angle - Wikipedia

    en.wikipedia.org/wiki/Parallactic_angle

    In spherical astronomy, the parallactic angle is the angle between the great circle through a celestial object and the zenith, and the hour circle of the object. [1] It is usually denoted q. In the triangle zenith—object—celestial pole, the parallactic angle will be the position angle of the zenith at the celestial object.

  5. Redshift-space distortions - Wikipedia

    en.wikipedia.org/wiki/Redshift-space_distortions

    Redshift-space distortions (RSDs) manifest in two particular ways. The Fingers of God effect is where the galaxy distribution is elongated in redshift space, with an axis of elongation pointed toward the observer. [1] It is caused by a Doppler shift associated with the random peculiar velocities of galaxies bound in structures such as clusters.

  6. Ecliptic - Wikipedia

    en.wikipedia.org/wiki/Ecliptic

    [1] [2] [a] It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of ...

  7. Glossary of astronomy - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_astronomy

    This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a ...

  8. List of largest cosmic structures - Wikipedia

    en.wikipedia.org/wiki/List_of_largest_cosmic...

    Made up of galaxy clusters. Quipu 1,300,000,000 Contains 68 galaxy clusters. [20] (Theoretical limit) 1,200,000,000 Structures larger than this size are incompatible with the cosmological principle according to all estimates. However, whether the existence of these structures itself constitutes a refutation of the cosmological principle is ...

  9. Ancient Greek astronomy - Wikipedia

    en.wikipedia.org/wiki/Ancient_Greek_astronomy

    This assures of bounded elongation. [40] Bounded elongation is the angular distance of celestial bodies from the center of the universe. Ptolemy's model of the cosmos and his studies landed him an important place in history in the development of modern-day science.