• And - Andromeda the Princess of Ethiopia

    IAU Constellation
    And - Andromeda the Princess of Ethiopia

    Size

    19 of 88
    Astronomical Regions
    Northern

    Intro and Visual description

    Andromeda contains one corner of the Great Square of Pegasus (the star Alpheratz). Andromeda’s dress flows outward from the corner along three pairs of stars, with each pair slightly farther apart than the previous pair. Perhaps she is petting Pegasus, who bore the hero Perseus across the ocean on his mighty wings to save her from the sea monster Cetus.

  • M31 - Andromeda Galaxy

    Object image

    M31, Galaxy Evolution Explorer, JPL, NASA

    Object image source

    Galaxy Evolution Explorer, JPL, NASA, Wikipedia
    Permission
    Public domain

    On one side of Andromeda’s dress is a patch of light called M31 or the Andromeda galaxy. The great galaxy in Andromeda shines at mag. 3.5. This beautiful spiral galaxy is the most distant object visible to the naked eye, yet the closest major galaxy to the Milky Way, about 2,200,000 light years away.

    Nearby are two small satellight galaxies, M32 (Elliptical galaxy), mag. 8.2. The other is NGC 205 (Elliptical galaxy), mag. 9.4.

    All the stars that are visible to the naked eye lie within our own Milky Way galaxy. This means that the stars that make up all the constellations, including Virgo and Leo and Coma Berenices, are stars of our own galaxy. The galaxies we see in these constellations are not actually located in the constellations, they are only viewed along the same line of sight. Were we to actually go to another galaxy, even the Andromeda galaxy (which is the closest major galaxy to the Milky Way, only 2.2 million light years away), then the stars of the Milky Way would not be distinguishable. It makes no sense to talk of the constellations of Andromeda or Virgo as seen from another galaxy, since from another galaxy any observer would see all of the Milky Way stars together, just as we see a small patch of fuzzy light when we look at the Andromeda galaxy. It is not that Andromedans would see our constellation Andromeda differently; they would not distinguish it from the Milky Way at all.

    The Andromeda galaxy has been known from early times. Al-Sufi described it as a "little cloud" in 964 AD. Simon Marius observed it in 1612 through a telescope, and described it as like a flame of a candle. It was not easy for astronomers to understand what a galaxy looks like. Early viewers of the Andromeda galaxy did not imagine that it was a star system like our own. Christian Huygens (HOY-gens) thought it was a hole in the heavens through which we might peer into the luminous regions beyond. Edmond Halley agreed, suggesting that the light came from a region of perpetual day, a shining ether filled with the light that originated on the first day of creation, before the formation of the Sun, Moon and stars. In 1845 Lord Rosse, using his great reflecting telescope, first resolved it into stars. In the 1920s Edwin Hubble--using the 100-inch telescope at Mount Wilson--used Cepheid variable stars to show that the Andromeda galaxy lay beyond the Milky Way. Thus Hubble established that the "nebulae" or cloudy spots which could be resolved into stars are actually external galaxies.

  • Gloria Frederici

    Asterism Visual Appearance

    Frederick’s Glory; also Federici Honores.

    Located between: Andromeda, Cassiopeia, Lacerta, Pegasus.

    Asterism Origin and History

    Now part of Andromeda. Named by Johann Bode for the King of Prussia, Frederick II, in 1798. Also known as Honores Frederici.

  • Great Square of Pegasus

    Asterism Visual Appearance

    Andromeda contains one corner of the Great Square of Pegasus (the star Alpheratz).

  • Hyginus (1485) figure: Andromeda

    Hyginus-1485-Andromeda

    Andromeda is portrayed as androgynous. This is not in the accompanying text. Her arms are outstretched, representing when she was exposed to the sea-monster. 

  • Bode (1801), Plate 1: Aries Planisphere

    Bode-1801-01-planisphere

    Uranographia Tab I. Stellatum Hemisphaeri um Arietis. 

    Bode included two planisphere plates. They are not southern and northern hemispheres; each one has Polaris at the top and the south pole at the bottom. Each one is centered upon an equinox point (where the ecliptic or path of the Sun and the celestial equator intersect). The March equinox point was in Aries in antiquity; by Bode’s time, due to the precession of the equinoxes, it had shifted to Pisces. The September equinox point was in Libra in antiquity; by Bode’s time it had shifted to Virgo.  Bode titled the plates as the Aries and Libra planispheres.

    The Aries planisphere, centered on the March equinox in Pisces, includes these constellations, among others, which appear high overhead in the night skies of autumn:

    Equatorial:  Orion, Taurus, Harpa Georgii, Cetus, Aries, Pisces, Pegasus, Aquarius, Aquila, Scutum.

    Northern:  Auriga, Perseus, Andromeda, Cassiopeia, Draco, Honores Frederici, Cepheus, Cygnus, Lyra.

    Southern:  Eridanus, Apparatus Chemicus, Machina Electrica, Apparatus Sculptoris, Horologium, Toucan, Phoenix, Grus, Indus, Pavo, Tubus Astronomicus, Octans Nautica, Microscopium, Sagittarius, Globus Aerostatic.

    In March, the Aries-Pisces equinox (the center of the Aries planisphere) is traveling with the Sun, rising in the east in the mornings and setting in the west in the evenings. Imagine the center of the planisphere has the Sun pinned to it for that day, and that’s how it would move across the sky. Therefore the constellations near the center of this planisphere are invisible in the daytime sky at that time unless there is a solar eclipse. They would be visible directly opposite the Sun at the September equinox.