Skynotes September 2013

Month Highlights

There is a lovely dance of the planets going on in the evening sky this month. Looking towards the west after sunset you can see Saturn, the bright star Spica, Venus, and a little later in the month Mercury.  By month’s end they have all switched positions and the line up becomes Venus, Saturn, Mercury and Spica.

September School Holidays

Scienceworks will be opened daily from 10am–4:30pm during school holidays (21st September – 6th October). Planetarium session times are:

12pm: Tycho to the Moonmeet Tycho, a dog who doesn’t just howl at the Moon but wants to go there!

1pm: Solar System Odyssey– stowaway on a mission to explore the Solar System.

2pm: Ticket to the Universe enjoy an amazing guided tour of our vast and incredible Universe.

3pm: Black Holes: Journey into the Unknown where the unimaginable becomes reality.

See the Melbourne Planetarium's What's On listing for more details.

Sunrise & Sunset Times

    Rise Set
Sunday 1st 6:42 5:59
Wednesday 11th 6:27 6:07
Saturday 21st 6:11 6:15
Monday 30th 5:57 6:23


Moon Phases

New Moon Thursday 5th
First Quarter Friday 13th
Full Moon Thursday 19th
Last Quarter Friday 27th

The Moon will be at apogee (furthest from Earth) on Saturday 28th at a distance of 404,308km.

The Moon will be at perigee (closest to Earth) on Monday 16th at a distance of 367,387km.

Let the Moon Be Your Guide

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

  • Before sunrise on the 1st the waning crescent Moon is just to the right of Jupiter.
  • After sunset on the 8th the waxing crescent Moon sits below Venus and Spica.
  • Then on the 9th the Moon is between Saturn and Venus.
  • On the 12th the First Quarter Moon is just near the red supergiant Antares (Scorpius).
  • During the early hours of the 25th the waning gibbous Moon sits between the star cluster Pleiades and the red giant star Aldebaran (Taurus).
  • On the 29th, the waning crescent Moon is back with Jupiter.

Planets

Mercury reappears above the western horizon during the first week of the month. By the 25th, it is directly to the right of Spica (Virgo) and on the 30th it is quite high - sitting between Spica and Saturn, while Venus looks on from above.

Venus continues to delight in the evening sky at sunset. On the 6th, it sits to the right of the bright star Spica (Virgo). Then on the 9th there is a great line up of Saturn, the crescent Moon, Venus and Spica. By the 17th, Venus can be found directly to the left of Saturn.

Earth days are warming up again as we pass the Spring Equinox on Monday 23rd. At 6:44am the Sun crosses the celestial equator heading south. While it is often said that day and night are equal on the equinox, this is not quite so. It is only the centre of the Sun that is above the horizon for 12 hours; our day is slightly longer at 12 hours and 8 minutes. That’s partly because the day starts with the first appearance of the Sun, but there’s another strange effect going on as well. The Earth’s atmosphere bends light from the Sun so that at sunrise we happen to see the Sun before it physically crosses the horizon. The reverse occurs at sunset, we continue to see the edge of the Sun for several minutes even though it has already sunk below the western horizon. So on that basis, when is day and night equal? On Thursday 19th, a few days before the equinox.

Mars appears in the morning sky above the north-east horizon a few days into the month. It sits below and to the far right of Jupiter.

Jupiter is right next to the crescent Moon on the morning of the 1st. It spends the month in the north-east before sunrise, with the twin stars of Gemini, Castor and Pollux just below. The Moon rejoins the planet on the 29th.

Saturn begins to make its way towards the western horizon this month. At the start of the month it sits above Spica (Virgo) and Venus. Then on the 9th, the crescent Moon can be found between the two planets. On the 18th, Saturn sits directly to the right of Venus, then the two planets switch positions, with Venus being the higher of the two. By the end of the month Mercury can be seen rising towards Saturn.

Meteors

September is a poor month for meteors. The Southern Piscids is the most active shower and while it has an extended peak which runs from the 11th to the 20th, it only produces a few meteors per hour. The meteors appear near the constellation of Pisces (the fish) which can be found in the north-west from midnight until dawn.

Stars & Constellations

In the early evening, the Southern Cross can be seen in the south-west, tipped over on its side, with the Two Pointers almost vertical above it. Above the western horizon sits the star Spica in the constellation of Virgo and in the north-west is the orange giant star Arcturus that belongs to Bootes, the herdsman.

Turning towards the south-east we see the bright star Achernar, which marks the end of the river, Eridanus, and also Fomalhaut, the brightest star in Piscis Austrinus. High in the north are the three main stars of Aquila, the Eagle, including the bright star Altair, while low to the horizon is Vega, the fifth brightest star in the night sky.

Directly overhead at sunset, the curl of the Scorpion’s tail can be seen near the teapot shape of Sagittarius. The Milky Way spans the sky overhead, looking splendid as it stretches almost north-south.

International Space Station

The ISS orbits the Earth every 90 minutes at an average distance of 400 km. From Earth, it appears as a bright star that steadily moves across the sky. It can often be seen from Melbourne, for example at:

7:35pm - 7:38pm, Saturday 7th September.

The space station will appear in the north-west and will disappear as it travels overhead.

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

On this Day

1st 1939, Oppenheimer and Snyder publish the first paper that describes black holes.

1st 1979, Pioneer 11 (USA) made the first flyby of Saturn and returned the first close-up images of the planet.

5th 1977, Voyager 1 (USA) was launched to explore the outer Solar System.

8th 1966, the first episode of Star Trek was shown.

9th 1839, John Herschel made the first ever glass plate photograph.

11th 1985, ICE (USA) became the first craft to encounter a comet (Comet Halley).

14th 1959, Luna 3 (USSR) became the first craft to fly to and impact another celestial body, the Moon.

15th 1997, the Mars Global Surveyor (USA) discovered a weak magnetic field around Mars.

18th 1977, Voyager 1 (USA) returned the first image of the Earth and the Moon together.

23rd 1846, Neptune was discovered by Johann G. Galle (Germany).

27th 1905, Albert Einstein submits the paper containing the famous equation E=mc2.

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