Skynotes: November 2020
Image: NASA Scientific Visualization Studio
More water on the moon
The moon has water ice in dark polar regions, that much we knew from the 2009 LCROSS impact mission, but now NASA has found evidence for water at a location during full sunlight. Its airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) has detected the valuable resource in the ancient Clavius Crater in the heavily cratered southern highlands.
It has been able to distinguish between the two molecular forms of water - H2O and OH (hydroxyl). Have micrometeorites delivered it over millions of years? Has solar radiation interacted with hydroxyl to form water that has then bound with the lunar soil or regolith? And the big question - just how much is there? Our nearest neighbour continues to surprise us.
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Penumbral lunar eclipse
This month we have two full moons with one coinciding with a lunar eclipse. On November 30 the full moon will pass through the outer part of Earth’s shadow, the penumbra. Less impressive than a total lunar eclipse when the moon dives completely into the Earth’s inner shadow or umbra, this partial lunar eclipse will still be an interesting sight to enjoy.
Melbourne and central Victoria will miss the 6:32pm start of the eclipse with the moon below the eastern horizon but it will rise at 8:17pm, reach its maximum at 8:42pm and end at 10:53pm, after which the night’s full moon resumes.
Eclipses can only ever happen at full moon when the moon is on the side of Earth opposite the Sun and its Earth-facing hemisphere is fully illuminated. Occasionally, however, a full moon’s path will briefly bring it into our planet’s shadow and we can marvel at one of several kinds of eclipses.
Illustration by courtesy timeanddate.com
No two eclipses are ever quite the same. The moon’s distance from Earth varies by about 50,000km as its orbit in not circular but elliptical, and its path is tilted by a little over 5 degrees with respect to Earth’s orbit around the sun. Depending on the moon’s exact distance and specific orbital orientation at that time, it can enter the long narrow cone of Earth's shadow to a greater or lesser degree. For most full moons it misses it, but at other times it can graze it or move deeply into it. This complex ‘shadow dance’ makes for a variety of possible eclipses.
With a passage through part of Earth’s outer shadow, or penumbra, most of the lunar surface remains in full sunlight and there is little change to the moon. If it moves completely into the penumbra, with reduced illumination we see a slight dimming of the moon. However, the most dramatic lunar eclipse is when the moon passes partially or totally through the full shadow, or darker umbra. For the few hours of a total lunar eclipse the sun cannot fully illuminate the moon directly, the Earth being in the way. But some sunlight does pass through the thin band of our planet's atmosphere, which scatters the blue part of the spectrum, leaving the red wavelengths to reach the moon, giving it a rusty or coppery colour. One of the many intriguing wonders of the Earth-Moon system.
This month’s lunar eclipse will last 2hrs 35min with 82% of the moon in shadow at its maximum.
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A thought experiment
Imagine you are on the moon on the side facing Earth. A lunar eclipse is about to begin. Earth is dark as the sun is directly behind it. It is night for that side of the planet. The moon then takes you into and out of Earth’s shadow. Would you see any change to the Earth? What about the moon around you? Would your experience be the same or different for each type of lunar eclipse? The Melbourne Planetarium show Moonbase ONE looks at all these scenarios.
Melbourne sun times
| Date | Rise / Set / Day Length / Solar Noon* |
|---|---|
| Sat 1 | 6.13am / 7.54pm / 13.41 hrs / 1.03pm |
| Wed 11 | 6.03am / 8.05pm / 14.02 hrs / 1.04pm |
| Sat 21 | 5.55am / 8.16pm / 14.20 hrs / 1.06pm |
| Mon 30 | 5.52am / 8.25pm / 14.33 hrs / 1.08pm |
* The sun is at its highest crossing the meridian or local longitude.
Moon phases
| Phase | Date |
|---|---|
| Full Moon | Sunday 1 |
| Third Quarter | Monday 9 |
| New Moon | Sunday 15 |
| First Quarter | Sunday 22nd |
| Full Moon | Monday 30 |
The Moon will be at perigee (closest to Earth) on Saturday 14 at 357,837 km and at apogee (furthest from Earth) on Friday 27 at 405,894 km.
Planets
Mercury is not visible from Melbourne this month and will be moving closer to the sun.
Venus is rising about 4.40am and will be visible for hour and a half before dawn.
Mars can be seen from 8.30pm as it rises in the North East and traverses the northern sky until setting in the west by 4am.
Jupiter can be seen in the early evening in the western sky before setting around midnight. Both gas giants will be located above Sagittarius.
Saturn follows Jupiter in the west and will set by 1am. By the end of November the two large planets will be drawing closer together, with Jupiter brighter and Saturn with a yellow hue.
Meteors
The Taurids is an old meteor stream peaking in the first week of November. They can be bright, slow moving, with occasional colourful fireballs. One branch appears near the star cluster Pleiades and the other near the red star Aldebaran in Taurus which rises in the north-east around 10pm. Around 10 per hour can be seen, but every few years activity increases with brighter meteors and more fireballs.
The Leonids occur from 13–20 November peaking on the morning of 18 November. They result from Comet Tempel-Tuttle that orbits every 33 years. It reached perihelion (closest to Sun) in 1998 after which thousands were seen globally per hour. Since then the rate has been about 15 per hour. They appear in the direction of Leo, the lion, which rises in the north-east around 4am, are fast and leave lots of trains that can last several minutes.
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:
Evening
- Monday 2nd: 9.30pm-9.34pm South-West to East-North-East
- Thursday 5th: 8.44pm-8.50pm West-South-West to North-North-East
Morning
- Friday 27th: 4.46am-4.52am North-West to South-East
- Monday 30th: 4.01am-4.05am West-North-West to South-East
For predictions go to www.heavens-above.com.
Stars and constellations
Scorpius and Sagittarius, the centaur-archer are in the south-west after sunset. The red giant star, Antares, can be imagined as the heart of the Scorpion. In Sagittarius it’s easy to identify the asterism or informal pattern known as the Tea Pot (which is the archer’s bow and arrow).
Later in the night the Pleiades star cluster followed by Taurus, the bull and Orion, the hunter will rise one after the other in the east (giving you an early look at a sequence for summer when these will be visible in the evening).
The Southern Cross is now upside down during the early evening with The Two Pointers to the right and the bright star Canopus to the left.
In the Boorong tradition on north-west Victoria, the Cross is Bunya, the possum, who was once a warrior but who fled high into a tree after failing to deter the dangerous emu Tchingal from attacking the people. The Milky Way’s dark dust clouds are the emu’s body and Coal Sack next to the Southern Cross is its head. Go to Australian Indigenous Astronomy to learn more.
This month you may be able to find the most distant object visible to the naked eye, the Andromeda Galaxy (M31 in Charles Messier’s catalogue). It appears as a faint smudge just above the northern horizon, sitting below and to the right of the square of Pegasus, the winged horse.
On this day
1st 1963, then largest radio telescope, the Puerto Rico Arecibo Observatory, opens utilising a natural valley and transceiver suspended from pylons on nearby peaks.
3rd 1957, Laika, a 3-year husky-Samoyed dog, became the first animal into orbit in Sputnik 2 (USSR). While never intended to return to Earth, she expired from heat stress after only a few hours.
3rd 1973, Mariner 10 (USA) launches to Mercury, the first probe to use a gravitational ‘slingshot’ around a planet to reach an objective (in this case, Venus).
4th 2003, largest solar flare recorded causes radio blackouts and saturates satellites, and was associated with a Coronal Mass Ejection (CME) many times larger than Earth leaving the Sun at 2,300 kph.
8th 1656, birth of second Astronomer Royal Edmund Halley who calculated several historical comets to be the same. He successfully predicted its regular 76-year return. It posthumously carries his name.
9th 1934, birth of American astrophysicist and science communicator Carl Sagan.
12th 2014, First landing on a comet and direct surface images of Comet Churyumov-Gerasimenko by Philae lander from ESA’s Rosetta probe.
12th 1980, Voyager 1 (USA) has historic close encounter with Saturn at 124,000km. It then flew by moon Titan which precluded going on to Uranus or Neptune, both however visited by its twin Voyager 2.
13th 1971, Mariner 9 (USA) is the first spacecraft to orbit another planet, Mars. Months of a planet-wide dust storm finally cleared to allow pictures of the surface.
15th 1738, discoverer of Uranus and infrared radiation, William Herschel, is born.
14th 2003, Sedna, a TNO (Trans Neptunian Object) is discovered in a 11,400 year elongated orbit, one of the most distant objects known in the Solar System.
16th 1965, Venera 3 (USSR) is launched to Venus becoming the first probe to reach the surface of another world.
16th 1974, first radio message sent into space (USA/Puerto Rico). ‘Arecibo Message’ to star cluster M13 25,000 light years away took 3 min. Its 1,679 binary 1’s and 0’s if arranged in 23 columns and 73 rows will reveal visual information (prime numbers 23 x 73 = 1,679).
17th 1970, Lunokhod 1 (‘Moon Walker’, USSR) first remote-controlled moon rover. Delivered by lander Luna 17, it drove 10km and lasted 321 Earth days, far longer than the expected 3 months.
20th 1998, First module for the ISS, Russia’s 12 metre Zaryu (‘Sunrise’) or Functional Cargo Block, is launched beginning a multi-module multi-year assembly of the space station in low Earth orbit.
26th 2012, Curiosity rover (USA) arrives in Mars’ Gale Crater after a high-speed entry and first use of an innovative final landing technique – the ‘sky crane’.
27th 1971, first probe to reach the Martian surface is Mars 2 (USSR) although it crashes in the process.
27th 2001, first detection of composition of exoplanet’s atmosphere – by Hubble Telescope for planet Osiris orbiting a sun-like star 150 light years away.
28th 1967, Cambridge postgraduate student Susan Jocelyn Bell discovers the first pulsar, initially named LGM1 for “little green men”. Its regular 1.3 sec radio pulse revealed these pulsating stars to be rapidly spinning neutron stars.
29th 1967, Australia becomes the third nation after USSR, USA and France to launch a satellite from its own territory. The 45kg WRESAT-1 (Weapons Research Establishment Satellite) made 642 polar orbits until re-entry 11 days later.
30th 1609, Galileo studies the Moon with his improved telescope, and while not the first to do so he was the first to explain mountains and craters, and chart lunar features and their heights.
30th 1954, Ann Elizabeth Hodges of Alabama, USA, becomes the first person injured by a meteorite. She was badly bruised by a 5kg rock that crashed through her roof, deflected off a radio cabinet, and hit her while she was asleep on the couch.