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Melbourne Sun times

Date	Rise	Set	Day length	Solar noon*
Wed 1	5.51	8.26	14.34hrs	1.09
Sat 11	5.51	8.34	14.33hrs	1.13
Tue 21	5.54	8.41	14.47hrs	1.18
Fri 31	6.00	8.45	14.44hrs	1.23

*When the Sun is at its highest, crossing the meridian or local longitude.
 

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Partial solar eclipse

Last month we had a partial Lunar Eclipse and this month, on Saturday December 4th, there will be a Solar Eclipse with the Moon obscuring part of the Sun. In Chile and Argentina it will be a total eclipse with the entire solar disc covered for a little over 2 minutes. In Melbourne, however, it will be a partial solar eclipse with only about 1% of the Sun’s disc obscured. Unfortunately, it will not be grandly impressive and the Sun will be very low in the sky.

The moon will briefly ‘graze’ the edge of the Sun. The eclipse will occur in the evening just prior to the setting of the Sun and end just after sunset. A clear view to the south-western horizon will be needed.

The Earth-Moon-Sun line up for a solar eclipse means the moon will not be visible because the side facing Earth will not be lit by sunlight. If viewed safely it will appear as it if a small corner of the Sun is being ‘eaten’ for a short time.

Melbourne times (AEDT)

Eclipse begins	7.53pm
Maximum (1% eclipsed)	8.12pm
Sunset	8.29pm
Eclipse ends (below horizon)	8.30pm
Total duration	36 minutes

Never view a solar eclipse directly!

Do not use sunglasses, x-ray or camera film, smoked glass, or most dangerous of all binoculars or telescopes (unless fitted with a special solar filter). Blindness or permanent eye damage can result. The safest way is indirectly by projecting the sun’s image onto a surface. A pinhole in a card will allow the Sun’s image to appear on a second card or a smooth surface. See safe methods & tips or How to Safely View A Solar Eclipse.

For more details, the geometry of the event, and simulations try these excellent sites:

Over the next 20 years there will be 15 total solar eclipses around the world. The next for Australia will occur on 22 July, 2028 when the moon’s darkest shadow or umbra will race across the continent from north of Broome, past Dubbo and then directly over Sydney. It will continue across the Tasman to the South Island of New Zealand close to Queenstown and over Dunedin.
 

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Moon phases

Phase	Date
New Moon	Sat 4th
First Quarter	Sat 11th
Full Moon & Lunar Eclipse	Sun 19th
Third Quarter	Mon 27th

The Moon will be at perigee (closest to Earth) on Sat 4th at 356,794 km and apogee (furthest from Earth) on Sat 18th at 406,320 km.

Our near and far Moon

The Moon’s perigees and apogees result from the shape of its orbit which is not circular but elliptical. But the moon’s path is certainly not static or fixed. It changes over time. The average Earth-Moon distance is 384,400 km and yet the difference between its extremes is about 42,000 km. And no orbit is exactly the same. The Moon and lunar distances are affected by a number of factors, including the gravity of Earth and Sun, the tidal effect from our oceans, local mass concentrations in the crusts of Earth and Moon, and both bodies even ‘wobble’ slightly on their rotational axis over a long-time scale. Add the fact that its orbital speed changes - faster when closer to Earth and slower when further away – and you realise Old Luna is a forever changing partner as it dances with the Earth around the Sun.

The Moon’s perigee this month will be the closest our neighbour has been all year. During 2021 it has varied from 229,980 km in February to this month’s closest-of-the-year. Perigees this year have ranged by 8,278 km.

Equally, the Moon’s monthly apogee has changed too. It was furthest in May and over the year that monthly distance has varied by 2,412 km.

Explore more

Our Moon is moving out

While not directly relevant to perigees and apogees, it is interesting to note that our neighbour is also slowly drawing away from us by almost four centimetres a year. Find out why the moon is moving away here at NRAO.

But how can we know the actual distance between Earth and Moon? Ingeniously, in fact, by using retro-reflective mirrors left behind on the Moon by Apollo astronauts in a laser ranging experiment. Earth-based observatories fire laser beams to the small mirror arrays on the surface of the Moon and special angled mirrors reflect the beam directly back. Knowing the speed of light and clocking the exact period of the laser pulse’s round trip return a precise calculation is made giving a highly accurate answer to how far away the Moon is at that moment. By carrying out the experiment over days, months, years, and by now decades, measurements of apogees and perigees are made and compared against theoretical predictions, and the rate the Moon is receding established over the long term.

New reflectors in space

A new generation of compact lightweight laser reflector arrays (LRA) are now in use. They are small and robust with quartz cube mirrors. They are in use on Earth in geodesy applications, and are designed to allow for precise location of satellites in orbit, probes in space, or landers and rovers on a moon or planetary surface.

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Summer solstice

It will be Summer Solstice in the Southern Hemisphere on Wednesday, 22nd December. For Melbourne that will be at 2:59pm. On that special day of the year the Sun will rise at its most southerly point on the eastern horizon, reach its highest elevation of the year, and set at its most southerly point in the west.

With Earth’s titled axis of 23.5 degrees (with respect to the plane of its orbit) the southern hemisphere will be leaning towards the sun, sunlight will be almost perpendicular reaching the ground, the sun’s path across the sky will be longest, and daylight hours will therefore be greatest. All these factors lead to our summer warmth.

This is in direct contrast to winter when opposite conditions apply – the south leans away from the sun, rays are at a shallow angle, the sun’s path is low and short, and daylight hours are least.

For the difference between astronomical and meteorological seasons visit timeanddate.com.
 

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Planets

Mercury is not visible this month being too close to the sun.

Venus has been the ‘evening star’ in the west during the last few months and will continue to be visible into December from 9pm setting before midnight. However, each evening it will become visible progressively lower in the west until by the end of the month it will become lost in the dusk of evening. It will then take a pass behind the Sun to reappear in late January as the ‘morning star’ in the east before sunrise.

Mars has now completed its pass behind the Sun but is too close to be visible this month.

Jupiter, the third brightest object in the night sky after the moon and Venus, will be visible in the north-west from just before 9pm in the fading twilight before setting around 1am early in the month. By mid-month it will set around midnight, and by month’s end by 11.30pm.

Saturn remains easy to spot between Venus low in the west and Jupiter higher up in the north-west. In early December it will appear in the twilight shortly after Jupiter and lead Jupiter towards the horizon by midnight. The yellow-tinged second largest planet will set earlier each night until by the end of the month it will be gone by 10.45pm.

Triple line-up: Venus-Saturn-Jupiter

As was the case in November, three of the five visible planets will continue to appear in an impressive line in the western evening sky. They will be in Sagittarius, Capricornus and Aquarius with Venus low in the west, Saturn mid-way and Jupiter higher in the north-west.

A bonus addition to line-up this month will be the Moon. From 10th it will be to the right of Jupiter in the west as a crescent moon reaching First Quarter the 11th. Each night after that it will be further to the north as it transitions to a Full Moon in the east on the 19th. Over a week or so you can both enjoy the planetary line-up and observe our lunar neighbour change phases.
 

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Meteors

This month is time for the Geminids which peak on the night of 13th/14th They are a consistent source of meteors and appear in Gemini in the north-east with the bright star Castor. Most meteor showers result from Earth passing through the debris trail of past comets, but the Geminids are associated with asteroid Phaethon which orbits the sun every 1.4 years. In an hour in good viewing conditions you could expect 40-120 meteors.

A handy visual guide for meteor showers has been produced by Praveen Suryavanshi. Although created for this year, all details will remain the same for 2022 except for moon phases. The chart helpfully gives a visibility index (big eyeballs for good viewing), plus names, dates and times, constellations and radiant points, expected hourly rates in good conditions, and the source for each meteor shower.

Find out more about this month’s meteor shower and these celestial visitors in general at NASA’s Solar System Exploration The Geminids and Meteors & Meteorites.
 

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Stars and constellations

In the East

Across the entire eastern sky this month, ranging from the north-east to the south-east, we have a rich night sky to enjoy. Although from a southern hemisphere perspective some constellations will be inverted. It’s a fact of life living on a globe that when you move far enough north or south of the equator a star pattern ends up appearing upside down. It is for the same reason the face of the Moon is upside down viewed from one hemisphere compared to the other.

Directly east is Sirius, the brightest star in the night sky and principal star in the constellation Canis Major (Greater Dog), one of two companions to the hunter Orion who is in the north-east. Look for three bright stars in a row and you’ve located his belt. In our southern view they are Alnitak (lower left), Alniham (centre) and Mintaka (upper right).

Hanging off his belt is his scabbard or sword which runs to the upper right and which contains a ‘fuzzy star’ which in reality is the beautiful Orion Nebula - a stellar nursery of gas and star formation 1500 light years away lit by young hot stars deep in its interior.

See below for a Stellarium view of Orion and nearby Taurus.

Lower right in Orion is the red giant star Betelguese which is one of his shoulders. While human eyesight is not good at detecting colour at low light levels, such as at night, this star is one of several that emit enough red light that we can easily notice. To the left and a little higher is Bellatrix his other shoulder or armpit. By contrast, at upper left is the bright blue giant star Rigel which marks one of Orion’s feet, the other being Saiph a less bright star a little lower to the right.

In the North

North of Orion is Taurus the bull, with another bright red star Aldebaran marking the Bull’s red eye. A little to the right is the beautiful Pleiades star cluster or Seven Sisters. See below for a photo of this iconic world-famous feature of the night sky. It seems all cultures have given it a significant place in stories and lore.

In fact, many cultures in widely different regions or even different continents regard the Pleideas as a group of women and the stars of Orion as forming a man. Is it because of a common or universal sense perception? That is, regardless of culture, do humans see similar patterns in nature’s randomness, such as stars at night. Or, alternatively, could it be that from one culture some interpretations of the stars have spread across the globe as groups left ancestral lands to migrate to new regions, crossing oceans and settling new continents taking their star stories with them?

In the West

Apart from bright Jupiter in the north-west in Aquaruius, fainter Saturn lower down in the west in Capricornus, and Venus still visible in the early evening low in the west in Sagittarius, the sky features the star Formalhaut (Alpha Piscis Austrini) high in the west as the brightest star in the constellation of Piscis Austrinus (Southern Fish). See September’s Skynotes for more on Formalhaut and the circumstellar dust ring surrounding it within which a planet was discovered in 2013.

In the South

Low in the south and upside down is Crux (Southern Cross) with the Two Pointers (Alpha and Beta Centauri) easily seen to its right as clear markers to the Cross. High in the south are the Large and Small Magellanic Clouds, our galaxy’s two small companion satellites that appear as fuzzy patches sitting on their own.

In locations away from city lights you will also recognise the broad expanse of the Milky Way stretching from the south-east along the horizon to the west. As the night wears on and the Earth rotates to the east the effect will be to see it ‘wheel’ across the night sky as a majestic arc of billions of distant stars and many dark interstellar dust clouds (such as the Coal Sack that sits beside the Southern Cross).

Galactic Challenge - last chance for 2021

Can you find the most distant object visible with the unaided eye? We repeat from last month our Andromeda Galaxy M31 invitation. From Melbourne, but even better away from the city’s light pollution, and with a clear view to the horizon, you might still be able to locate our galaxy’s large neighbour very low in the north. It will appear about the size of the moon although far fainter.

If unsure of its location, start at the beautiful star cluster the Pleiades (or Seven Sisters) in Taurus in the north-north-east.

Our scene from Stellarium should help. It’s for Melbourne at 10pm on December 5 (but try other nights too). The view spans west to north-east with the horizon in green and compass points in red. At right are the constellations of Orion and Taurus (with the Plaeides) and Andromeda low in the centre. To the left are Jupiter and Saturn. Details in the top left corner include M31’s setting time (11.19pm for that night), its angular diameter in the sky (~3 degrees), and its distance (2.538 million light years). Your mission target lies within the squared marker.

To inspire you, here again is that beautiful example of what it looks like on a dark night. On the next clear night this month see if you can spot our big neighbour!

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International Space Station

ISS orbits every 90 minutes at an average distance of 400 km appearing like a bright star moving slowly across the night sky. Here are some of the brightest passes expected this month over Melbourne and Central Victoria:

Morning

• Wed 15th 4.55am-5.01am West-South-West to North-North-East
• Thu 16th 4.07am-4.14am South-West to North-East

Evening

• Sun 12th 10.21pm-10.28pm North-West to South-East
• Thu 30th 10.46pm-10.49pm West-South-West to North-North-East
• Fri 31st 9.58-10.04pm South-West to North-East

Heavens Above gives predictions for visible passes of space stations and major satellites, live sky views and 3D visualisations. Be sure to first enter your location under ‘Configuration’.
 

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On this day

1st 1922, solutions to Einstein’s equations for space-time and mass-energy are developed by Alexander Friedman.

2nd 1915, Einstein’s General Relativity is published on gravity-acceleration equivalence and space-time curvature. 

2nd 1971, Mars 3 (USSR) - first soft landing and return of data from Mars.

3rd 2014, JAXA explorer Hyabusa 2 (Japan) is launched to asteroid Ryugu with a planned sample return to Earth.

3rd 1973, Pioneer 10 (USA) makes the first fly-by of Jupiter and returns the first close-up images of the planet.

7th 1676, Danish astronomer Ole Remer calculates first accurate speed of light by observing eclipses of moon Io by Jupiter.

7th-19th 1972, Apollo 17 (USA): last moon mission and longest on lunar surface at 74 hours, 59 mins by astronauts Eugene Cernan and Harrison Schmitt.

7th 1995, Galileo probe (USA) makes first orbit of Jupiter after six years in transit.

8th 1977, HEAO 1 (USA), High Energy Astro Observatory, is launched into orbit.

8th 2010, SpaceX is first private company to launch, orbit and recover a spacecraft, its SpaceX Dragon.

10th 1993, the faulty optics of the Hubble Space Telescope (USA) are repaired.

11th 1863, birth of astronomer Annie Jump Canon compiler of Draper Star Catalog.

12th 1970, Explorer 42 (USA) satellite is launched to study x-rays.

14th 1546, Danish astronomer Tycho Brahe, whose data aided Kepler in his laws of planetary motion, is born. 

14th 1962, Mariner 2 (USA) is first probe to fly past Venus.

15th 1970, Venera 7 (USSR) is first probe to land safely on another planet, and first to return data, when it arrived at Venus.

21st 1988, Cosmonauts Vladimir Titov and Musa Manarov make longest space flight (365 days, 22 hours, 39 min) on Soviet space station Mir.

21st-27th 1968, Apollo 8 (USA) first manned craft to orbit the Moon - 10 orbits at 110km from the surface, imaging landing sites and the iconic ‘Earthrise’ photo.

24th 1979, ESA’s first launch vehicle Ariene 1 (France) orbits its first test satellite CAT1.

27th 1571, discoverer of laws of planetary motion, Johannes Kepler, is born.

28th 1612, Neptune is observed for the first time but mistaken as a star by Galileo.

30th 1924, astronomer Edwin Hubble (USA) announces faint ‘nebulae’ are actually galaxies beyond our own.