What’s up? Case Rijsdijk’s
The month starts with a waxing gibbous Moon that becomes full on the 5th. New Moon follows on the 20th, with the first crescent appearing after sunset on the 21st.
The new Moon also coincides with its perigee (closest approach to Earth) at only 358 256km!
The Moon's orbit is an ellipse, or slightly egg shaped, so in the course of the month its distance from Earth varies from 356 375 to 406 720km.
The Moon was furthest from Earth (at apogee) on the 4th, when it was 406 154km away.
Of course when the Moon is closer to us, it would appear slightly larger, while appearing smaller when it's further away, but the comparison is minimal. However this is not to be confused with the illusion that the rising full Moon appears larger than the full Moon higher up in the sky, later the same evening. This can be tested with a simple test: take a pencil and hold it at arm's length with just a little of the blunt end showing - this will just cover the rising full Moon. Repeat this a few hours later, and the pencil end still just covers the full Moon.
The evening sky this month is dominated by Orion. It reaches its highest point in the sky and is a truly magnificent sight. Many star names are of Arabic origin and Orion is no different. The belt stars from lower left to upper right are Mintaka, Alnilam and Alnitak.
The red super-giant star Betelgeuse (to
the lower right) is in the late stages of its life. Rigel (upper left) on the other hand is a young, blue and very hot giant star.
The Great Nebula in Orion, the middle star of the "dagger", pointing upwards in the southern hemisphere, is in fact a stellar nursery about 1 600 light years away and the gas and dust clouds are shining due to the reflected light of the young hot stars.
In a line through the belt stars going left (west) is the open cluster of the Hyades, with the red giant star Aldebaran to the lower right. Further west is the small dense cluster isiLimela/Pleiades/digging stars; their sighting indicate that it is time to start preparing the soil for planting.
The planets Venus, Jupiter and Mars are visible for the entire month and it is interesting to follow Venus and Jupiter, as they move progressively closer to each other until on the 28th they are very close together.
From the 26th to the 28th, Mars, Aldebaran and isiLimela form an equilateral triangle with a crescent Moon close to isiLimela on the 26th that passes by Mars on the 27th and 28th. Of course the Great Southern Triangle formed by Betelgeuse, Sirius (the Dog Star) and Procyon, (the Little Dog Star) is now very clear.
To the south, the Southern Cross and the Pointers are now a little higher in the southeast and away from city lights the Large and Small Magellanic clouds are well positioned high to upper right of the Southern Cross. The Large cloud in fact forms the table cloth for the Table Mountain constellation (also called Mensa, or Mons Mensae as it was originally named by De Lacaille) and is the only constellation named after a feature on Earth! It is a small and insignificant grouping with no bright stars.