June 10 – The Moon and Planets

June 10 – The Moon and Planets

Evening Highlights:
  • Jupiter is the brightest object in the night sky at magnitude -2.0 (smaller number means brighter), find it in the south-western sky.
  • Mars is the second brightest object in the southern sky at magnitude -1.86, and is almost directly south.
  • Ringed Saturn is the dimmest of the planets at magnitude 0.03, and can be seen just left and above Antares (the heart of Scorpius the scorpion) in the south-east.
  • Finally, the setting moon to the west, is a waxing crescent (meaning  expanding in illumination) and will be 32% illuminated.  See the moon first because it sets early!

Mars is one of the four terrestrial planets, which also includes Mercury, Venus, and Earth, and are so-called because they have similar characteristics such as being small, rocky and slowly rotating.  In contrast, Jupiter and Saturn are called gas giants, meaning they’re mostly comprised of hydrogen and helium.  However, don’t be tricked into thinking you could fly through them like the air we breathe!  Gravity is at work, and as you descend below the beautiful clouds of Jupiter and Saturn, gravity compresses the gases to the point where they turn into liquids, further towards the center they become metals, and at the core – well, we really don’t know what exists at the core because we don’t understand the properties of materials at such high temperature and pressure.

The moon is estimated to be 4.5 billion years old, and is  ‘tidally locked’  with the Earth, meaning the same side of the moon always faces Earth; the Earth rotates 15 degrees per hour, whereas the moon rotates 12.8 degrees per day.  However, due to what’s called libration – essentially wobbling of the moon – nearly 60% of the moon surface can be seen over time.  The far side of the moon, often incorrectly referred to as the dark side, actually sees as much light as the side facing Earth.  This is because the moon is rotating around the Earth, and when you see the full moon – which is when the near side is facing the sun – this means the far side is facing away from the sun, and conversely during a new moon (the near side is facing away from the sun) the far side is facing the sun.

Presentation Links

Stellarium: http://www.stellarium.org
Sky Safari: http://skysafariastronomy.com
Kepler Star Wheel (Planisphere): http://kepler.nasa.gov/education/starwheel/

Tonight’s Images

No images were taken this evening.

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