Babe Among The Stars: Occultations

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Galaxy Babe's column banner, showing a full moon and some little folk looking up at the sky

Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth - Ptolemy


An occultation is when one heavenly body passes in front of another, blocking it from view. The covered body is hidden for a short time, because the one in front is moving faster (from our perspective). Our Moon appears much bigger than faraway stars and even the giant planets of our own Solar System, because it's much closer to us. It also appears to move much more quickly and often occults background celestial bodies. These are all notable occasions to astronomers who like to watch these encounters actually happen. If you have a big enough telescope, you can watch other occultations such as distant planets covering stars. Scientific discoveries can be made during these special times. Take for example the star catalogued HD 128598, which was due to be occulted by the planet Uranus on 10 March, 1977. Astronomers set up their equipment, watched and waited. They were hoping to use the background star's light to study Uranus' atmosphere, but what they got was much more rewarding: Uranus had a ring system which had been impossible to detect from Earth until this particular occultation. This month, we have an unusual occultation to look forward to, though it will only be visible to viewers from north east USA and Canada. The asteroid 163 Erigone will blot out the 1st-magnitude luminary of Leo, 'royal star' Regulus, on 20 March for around 14 seconds. Good luck if you're planning to watch this!

March 2014 Diary Dates

1-8 March is National Astronomy Week in the UK. Check that link or your local press to find out what's going on in your particular area. My own local club, Cleethorpes Astronomy Society, will be hosting open evenings as well as its usual monthly meeting. March's guest speaker is local astronomer Paul Money, whom I've met several times. He was the astronomer on board the plane when I took an aurora flight, the first one from Humberside Airport.

  • 01: New Moon
  • 03: The Moon is 2° north of Uranus
  • 10: The Moon is 5° south of Jupiter
  • 11: The Moon is at apogee (furthest from Earth)
  • 11: Jupiter is at its highest point in the night sky. The next time it will be this high again will be in 2025.
  • 15: World Contact Day
  • 16: Full Moon - the Worm Moon
  • 18: The Moon is 3° south of Mars
  • 20 (pre-dawn): Asteroid 163 Erigone occults Regulus
  • 20: Vernal Equinox - first day of Spring (Northern Hemisphere), first day of Autumn (Southern Hemisphere)
  • 20: The Moon passes 0.2° south of Saturn
  • 22: Mercury is 1.2° south of Neptune
  • 27: The Moon is 4° north of Venus
  • 27: The Moon is at perigee (closest to Earth)
  • 28: The Moon is 5° north of Neptune
  • 29: The Moon is 6° north of Mercury
  • 30: New Moon
  • 30: British Summer Time begins: don't forget to push your clocks forward an hour!
  • 31: Mars is 5° north of Spica (alpha Virginis)

  • Chat about your celestial observances at the H2G2 Astronomy Society. Comment on anything in this edition of Babe Among the Stars by starting a new conversation below.

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