• Astronomy

  • Astronomy for Astrologers

  • Hi Everyone,

    As Astrologers we really need to understand enough Astronomy to underpin our knowledge of Astrology, so this is a brief introduction to the physical nature and the movements of the Sun and Moon and the planets of our Solar System that I hope will help you in this endeavour.

    The above image gives you an idea of the relative size of the planets.

    The relative distances can be considered by scaling the Sun-Neptune distance to 100 metres. The Sun would then be about 3cm in diameter and the giant planets would be all smaller than 3mm. The Earth's diameter along with that of the other terrestrial planets would be smaller than a flea (0.3mm) at this scale

    We’ll go through the details of each one now.

  • Sun

    The Sun is a nearly perfect sphere of hot plasma with a diameter of 1.39 million kilometres (109 times that of Earth), and has a mass 330,000 times that of Earth. This accounts for 99.86% of the total mass of the Solar System.

    The Sun is a G-type main sequence star (based on its spectral class) and is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the centre, while the rest flattened into an orbiting disk that became the planets, moons, comets and asteroids of our Solar System.

    The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years, and will remain fairly stable for more than another five billion years. At this point the core will experience an increase in density and temperature, the outer layers will expand and the Sun will grow to be a red giant engulfing Mercury and Venus and scorching the Earth.

  • Moon

    The Moon is the fifth-largest in the Solar System and the largest in relation to the size of the planet that it orbits.

    The Moon is thought to have formed about 4.51 billion years ago (not long after Earth) and the most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

    Interestingly, when it first formed the Moon would have been 15 times closer to the Earth than it is now. Just imagine how it would have looked in the sky if there had been any one there to see it, and imagine the absolutely huge tides (maybe 300m high) racing around the planet!

    The Moon is in synchronous rotation with Earth which means it always shows the same face, with its near side marked by dark volcanic maria that fill the spaces between the bright ancient crustal highlands and the prominent impact craters. Its surface is actually quite dark with a reflectance only just slightly greater than that of worn asphalt, It’s the comparison to the dark night sky that makes it appears very bright.

    The Moon's average orbital distance at the present time is 384,402 km (238,856 miles) which is about thirty times the diameter of Earth. It’s apparent size in the sky is almost the same as that of the Sun resulting in the Moon virtually exactly covering the Sun during a total Solar eclipse.

    This is an amazingly precise co-incidence and you might think the Solar eclipse would be quite a magnet for passing Alien “tourists” out on a journey to see the wonders of the Universe!

    However this matching of apparent visual size will not continue in the far future because the Moon's distance from Earth is slowly increasing.

  • Mercury

  • Venus

  • Earth

  • Mars

  • Asteroids

  • Jupiter

  • Saturn

  • Uranus

  • Neptune

  • Pluto

  • Chiron

  • Pholus

  • Other Centaurs