Skynotes October 2011

Month Highlights

It’s a good time to catch Mercury and Venus together in the sky this month. They are known as the inferior planets, but only because their orbits lie within Earth’s orbit around the Sun. It does mean that they never drift too far from the Sun and we only ever see them in the west at sunset, like this month, or the east at sunrise.

Another ‘inferior’ event this month is the smallest Full Moon of the year. On the 12th the Full Moon coincides with its apogee, that part of its orbit which takes the Moon furthest from Earth. But don’t be surprised if it still looks as impressive as always, after all it’s only 15% smaller.

Sunrise & Sunset Times

Moon Phases

The Moon will be at perigee (closest to Earth) on Wednesday 26th at a distance of 357,050 km.
The Moon will be at apogee (furthest from Earth) on Wednesday 12th at a distance of 406,434 km.

Let The Moon Be Your Guide

The Moon can be used as a pointer to find other objects in the sky.

• On the night of the 2nd the waning crescent Moon sets in the west near Antares the red supergiant star of Scorpius.
• During the night of the 13th the waning gibbous Moon travels across the sky with Jupiter.
• In the early hours of the 16th the Moon joins the star cluster Pleiades.
• The Last Quarter Moon sits above Castor and Pollux (Gemini) in the north-east before sunrise on the 20th.
• On the morning of the 22nd the waning crescent Moon is above Mars.
• Then on the 23rd, the Moon is above Regulus (Leo, the lion).
• On the 28th, the Moon has returned to the evening sky and sits above Mercury and Venus.
• On the 29th the waxing crescent Moon is back with Antares in Scorpius, during the early evening.

Planets

Mercury is chasing Venus in the evening sky. It’s always good when these two planets are together, as bright Venus is a useful pointer for finding faint Mercury. From the middle of the month Mercury can be found below and slightly to the left of Venus. On the 28th, the crescent Moon joins the pair and by the 31st, Mercury has caught up with Venus and the two planets sit side-by-side.

Venus is returning as the ‘evening star’, climbing up above the western horizon. Low to the west on the 5th, it sits to the right of the bright star Spica. After sunset on the 28th, the thin crescent Moon sits just above Venus, with Mercury to the left.

Mars is in the north-east before sunrise. It sits to the right of the twin stars Castor and Pollux (Gemini). On the 23rd the Moon sits above Mars and below them is Leo, the lion. Look for an upside-down question mark, with the tip being the bright star Regulus that lies to the right of Mars.

Jupiter reaches opposition on the 29th, which means it lies in the opposite part of the sky to the Sun. We get to see Jupiter all night long, rising in the east around 10pm and setting in the west around 7am. On the night of the 13th, Jupiter travels across the sky with the Moon, just a day after the Moon’s own opposition, what we call the Full Moon.

Saturn leaves the evening sky, dropping below the western horizon, during the first few days of the month. It will appear in the early morning sky next month.

Meteors

The Orionids are visible from the 15th to 29th, with the peak of the shower occurring on the 21st. Generally, this is a good shower for beginners with estimates of around 30 meteors per hour. As with all showers, the best time for viewing will be from around 3am until an hour before sunrise. The shower is centred on Orion’s club near the red supergiant star Betelgeuse and the meteors are typically fast, sometimes bright and generally more than half leave persistent trains. This shower was first recorded by the Chinese in 288 AD and is associated with Comet Halley.

The Taurids are a long-duration shower visible throughout spring and peaking during the first week of November. There are two branches to the shower: one appearing near the star cluster Pleiades and the other near the red star Aldebaran. Each branch has a maximum rate of roughly ten meteors per hour. They have been described as being bright, slow-moving and with the occasional colourful fireball.

Stars & Constellations

Scorpius is prominent in the western sky at sunset. Its claws are heading towards the western horizon, while the curved shape of its tail stretches high above.

Around to the north-west there are three bright stars: Vega (Lyra) and Deneb (Cygnus) are low to the horizon, while Altair (Aquila) sits up above. They make a lovely triangle, which in the northern hemisphere is known as the ‘summer triangle’, as these stars are high overhead during their summer.

Heading across to the north-east horizon is another famous northern asterism. Four stars stand out as the ‘Great Square of Pegasus’, including Alpheratz which is actually part of Andromeda.

Looking towards the south-east the star Achernar shines brightly at the head of the river Eridanus. A little further south but much lower in the sky shines Canopus, the second brightest star in the night sky. The Southern Cross is now seen in the south-west with the Two Pointers almost vertical above it.

International Space Station

From Earth, the ISS appears as a bright star that steadily moves across the sky. It can often be seen from Melbourne, for example at:

8:52pm - 8:58pm, Tuesday 4th October.

The Station will appear in the south-west and travel past Alpha Centauri and the First Quarter Moon before disappearing towards the north-east.

Predictions of when to see the ISS can be obtained from the Heaven's Above website.

On This Day

1st 1958, NASA (National Aeronautics and Space Administration) was inaugurated.

3rd 1815, the first meteorite identified as coming from Mars fell in Chassigny, France.

3rd 1942, German A-4 (V-2) rocket became the first rocket in outer space.

4th 1957, Sputnik (USSR) was launched to become the first artificial satellite.

5th 1923, Edwin Hubble (USA) established that M31, the Andromeda Galaxy, is separate to and distant from our own Milky Way Galaxy.

6th 1990, Ulysses (Europe) was launched to the poles of the Sun from the space shuttle Discovery.

7th 1959, Luna (USSR) took the first images of the far side of the Moon.

10th 1846, William Lassell (UK) discovered the first moon of Neptune,Triton.

10th 1980, the Very Large Array (VLA) telescope network is commissioned.

10th 1986, Cruithne, the satellite of the Earth with a horseshoe orbit, was discovered.

11th 1968, Apollo 7 (USA), the first manned Apollo mission was launched.

14th 1947, Charles E. ‘Chuck’ Yeager made the first supersonic flight (Bell X-1).

15th 1582, the Gregorian Calendar was established.

15th 1997, the spacecraft Cassini was launched.

18th 1989, the spacecraft Galileo was launched to Jupiter from the space shuttle Discovery.

21st 1923, the world's first projection planetarium, the Deutchse Museum, Munich, was officially opened.

22nd 2136BC, the first recorded solar eclipse was observed in China.

23rd 1975, Venera 9 (USSR) returned the first images of the surface of Venus.

31st 1992, the Catholic Church admitted it erred in condemning Galileo's beliefs.