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It has been a busy time lately in space exploration and astronomy.
Enjoy a special selection of the latest headlines covering a diverse range of fascinating topics with links to explore further.
| Date | Rise / Set / Day Length / Solar Noon* |
|---|---|
| Tue 1 | 5.51am / 8.26pm / 14.34 hrs / 1.09pm |
| Fri 11 | 5.51am / 8.35pm / 14.44 hrs / 1.13pm |
| Mon 21 | 5.54am / 8.41pm / 14.47 hrs / 1.18pm |
| Thu 31 | 6.00am / 8.45pm / 14.44 hrs / 1.23pm |
* The sun is at its highest crossing the meridian or local longitude.
| Phase | Date |
|---|---|
| Third Quarter | Tuesday 8 |
| New Moon | Tuesday 15 |
| First Quarter | Tuesday 22 |
| Full Moon | Wednesday 30 |
Moon perigee (closest to Earth) will be 361,773km on Sunday 13 December.
Moon apogee (furthest from Earth) will be 405,012km on Friday 25 December.
It will be Summer Solstice in the Southern Hemisphere on Monday, 21 December. For Melbourne that will be 9.02pm. On that special day of the year the Sun will rise at its most southerly point on the eastern horizon, reach its highest elevation during the day, and set at its most southerly point in the west.
Due to the Earth’s titled axis (23.5 degrees with respect to the plane of its orbit) the southern hemisphere will be leaning towards the sun, sunlight will reach the ground almost perpendicular, the sun’s path across the sky will be longest, and daylight hours will therefore be greatest. All these factors add to greater summer warmth.
This is in direct contrast to winter when the south leans away from the sun, rays arrive obliquely at a shallow angle, the sun’s path is low and short, and daylight hours are least. All of which lead to colder conditions.
Mercury is too close to the sun this month and not visible.
Venus, ‘the morning star’, rises around 4.30am and can be seen for an hour and half before being drowned out by sunrise.
Mars has passed opposition (when it was on the side of Earth directly opposite the sun and closest to us). The proximity we’ve been enjoying to the Red Planet is now decreasing as we draw away in our faster inner orbit around the sun. Mars will, however, continue to be clearly visible as an orange object in the north-east from around 9pm until it sets about 2am in the west.
Jupiter & Saturn – we update Skynotes to cover The Great Conjunction:
Jupiter, the third brightest object in the night sky after the moon and Venus, and Saturn with its faint yellow tinge, continue to be an easy pair to spot together in the south-west after 9pm. Over the last few weeks they have been drawing closer as seen from Earth. Their ever-closing proximity in the night sky will culminate on December 22 with The Great Conjunction. Larger and brighter Jupiter and fainter smaller Saturn will appear to the naked eye as one object. Our viewing angle looking out across the solar system gives us this special sight.
The planets lie in different positions in their orbits at any given time, but they also move at different speeds, those further from the sun slower than those closer in. From our vantage point, however, planets will sometimes conjoin – they will appear as one object. This apparent merging in the night sky is a conjunction and a ‘great conjunction’ is reserved for the two biggest planets. The gas giants will continue moving ever closer until December 22 (which happens to be the day after summer solstice). On that night looking out from Earth their angular separation in the sky will be a tiny 0.1 degree, about one fifth the diameter of a full moon. Afterwards the two will then diverge into distinct objects again, and night by night their separation as seen from Earth will increase as they continue their slow paths around the Sun.
It has been a long time, 900 years in fact, since such a close great conjunction was visible from Earth. This kind of celestial event, along with other planetary conjunctions, have been observed and recorded by ancient and medieval astrologers and astronomers. We know today that the physical distance between the two planets for this great conjunction will be 640 million km, or, in other words, Saturn will be 640 million km beyond Jupiter, but our line of sight will briefly make them appear as one.
Jupiter orbits the Sun in about 12 years while Saturn being much further out takes some 30 years. That means that roughly every 20 years Jupiter (in its inner track) overtakes Saturn. On those occasions they can sometimes appear reasonably close together at night but not qualify for a truly special conjunction. Sometimes they will be on the other side of the solar system with the Sun obscuring our view. But when Earth, Jupiter and Saturn are suitably aligned, as they will be on December 22, we can witness this rare event by virtue of our planetary perspective. The next Great Conjunction visible from Earth will not be until March 2080. Enjoy this one!
The most consistent meteor shower of the year, the Geminids, peaks on the night of 13–14 December in the north-east in the constellation of Gemini centred on the star Castor. Their parent body is the asteroid Phaethon, which orbits the sun every 1.4 years, unlike other meteor showers that derive from cometary debris the Earth passes though. Estimates of meteors vary from 40 to 120 per hour.
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:
Evening
Morning
For predictions go to www.heavens-above.com.
The Southern Cross is now upside-down in the southern sky and the Two Pointers (Alpha and Beta Centauri) sweep just above the southern horizon. High in the south are the Large and Small Magellanic Clouds, two small satellite galaxies of our own Milky Way Galaxy. These can be seen as fuzzy patches from dark sites. They lie close to 200,000 light years away and are slowly being drawn in towards our galaxy.
Low in the north-west, the great square of Pegasus (the winged horse) can be seen. In dark skies and with a clear view to the northern horizon, the small faint fuzzy patch below Pegasus is the Andromeda Galaxy (M31), the most distant object visible to the unaided eye at 2 million light years.
Orion, the hunter now returns in the north-east from sunset. He appears inverted in the southern hemisphere with the red star Betelguese as one of his shoulders. Orion’s central stars are often referred as the Saucepan which is right way up.
North of Orion is Taurus the bull, with the bright red star Aldebaran marking the Bull’s red eye. A little to the right is the beautiful Pleiades star cluster or Seven Sisters.
The two brightest stars in the night sky, Sirius (Canis Major) and Canopus (Carina), are towards the south-east with further south shines Achernar in Eridanus, the river.
Our First Peoples astronomy includes many local stories and night sky figures. From the Boorong tradition of north-west Victoria the central stars of Orion mark Kulkunbulla, two young men dancing, while the head of Taurus nearby is Gelarlec the songman, and the Pleiades star cluster is Larnankurk who beats out the rhythm with her drum.
The Southern Cross is Bunya the possum sitting high in a tree safe from the dangerous emu Tchingal whose head, neck and body are the dark clouds spread along the Milky Way.
The Magellanic Clouds are the bodies of Kourtchin, two proud brolgas flying in the sky with nearby stars marking out their long necks, long legs and wide wings.
An interesting question is why many cultures around the world in different continents and separated by vast distances appear to view the Pleideas as a group of women and the stars of Orion as forming a man (albeit upside down in the southern hemisphere). Was common human perception responsible, or perhaps ideas from one region or culture travelled as humanity spread across the globe?
Australia is home to a rich and varied history of tens of thousands of years from the oldest continuing tradition of night sky observing. For more go to aboriginalastronomy.com.au.
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.
Museums Victoria acknowledges the Wurundjeri Woi Wurrung and Boon Wurrung Bunurong peoples of the eastern Kulin Nations where we work, and First Peoples across Victoria and Australia.
First Peoples are advised that this site may contain voices, images, and names of people now passed and content of cultural significance.