Skynotes: March 2020
Red giant star Betelgeuse does it again
In the north-west this month is Betelgeuse, one of the best red giant stars to observe with the naked eye. In the constellation of Orion, it has kept astronomers and sky watchers interested over the years with its pattern of dimming and brightening. While ultimately destined to explode as a supernova, the star has always been fluctuating but has seemed to be more active lately.
When the nuclear fusion process in its core reached a critical stage in the past, Betelgeuse gradually expanded to equal the distance in our solar system to the orbits of Mars or possibly Jupiter. Its diameter is now 700 times the size of our sun but has a much lower surface temperature hence its red colour. However, with its luminosity not uniform and stellar output varying it provides a fascinating study for modelling the final stages of such huge stars. Enormous churning cells of hot gas constantly rise to the surface, cool by radiating their energy into space before descending back into the interior. For Betelgeuse this would be on a much grander scale than the much smaller convection pattern observed at the surface on our sun.
Learn more at National Geographic and Nature and enjoy Bernd Freytag's Simulations.
Month highlights
Autumn Equinox is this month with equal length of day and night, and there are good chances to see the International Space Station pass overhead early morning and evening.
Planetarium Nights
On Friday nights the Melbourne Planetarium reawakens after hours for adults only with a stellar line-up of fulldome film screenings.
Friday 6, 13, 20, 27 March
7.30pm – Ticket to the Universe + What's In the Sky Tonight?
9.00pm – Distant Worlds – Alien Life?
Melbourne sun times
| Date | Rise / Solar noon* / Set (day length) |
|---|---|
| Sun 1st | 7.04am / 1.32pm / 7.59pm (12.55 hrs) |
| Wed 11th | 7.14am / 1.30pm / 7.45pm (12.30 hrs) |
| Sat 21st | 7.24am / 1.27pm / 7.29pm (12.05 hrs) |
| Tue 31st | 7.33am / 1.24pm / 7.14pm (11.41 hrs) |
*When the Sun is at its highest crossing the meridian or local longitude.
Moon phases
| Phase | Date |
|---|---|
| First Quarter | Tuesday 3rd |
| Full Moon | Tuesday 10th |
| Third Quarter | Monday 16th |
| New Moon | Tuesday 24th |
This month’s Moon perigee (closest to Earth) is on Tue 10th 357,122 km and apogee (furthest from Earth) is on Wed 25th at 406,278 km.
Planets
Mercury rises after 5am but will be difficult to see.
Venus good viewing in the west until around 9pm.
Earth’s southern hemisphere experiences the Autumn Equinox on Friday 20th with the Sun rising due east and setting due west. The word is from the ancient Latin ‘aequinoctium’ (equal night) through medieval Latin ‘equinoxium’ to our modern ‘equinox’. At this time (and for the southern hemisphere’s Spring Equinox six months later) the Earth’s axis, at a fixed tilt of 23.5 degrees, does not lean toward or away from the sun as it does in winter and summer. On the 20th at 2:49pm from our view on Earth, the Sun crosses the celestial equator (the imaginary extension into space of the Earth’s equator). For Melbourne’s latitude day and night are equal in length a few days later on Tuesday 24th. This delay is because our atmosphere bends light from the sun; atmospheric refraction allows it to be seen a little before it physically rises, and for a short time after it has actually set. After the equinox its daily path across the sky shifts northward until mid-year’s Winter Solstice when the south pole and southern hemisphere leans fully away from the Sun, its path will be lowest in the sky, the angle of its rays will be shallowest giving least energy per square metre, the day will be shortest, and we have winter.
Mars is fair to good viewing rising about 2am.
Jupiter rises from 1.30am with good viewing.
Saturn follows around 2am with fair viewing.
Meteors
There are two small showers this month that occur near the South Celestial Pole. The gamma Normids is due to peak around the 14th centred on the yellow giant star Gamma Normae in the constellation of Norma, the level. The other is the delta Pavonids from the 21st peaking in early April in Pavo, the peacock. Meteor showers are best seen from midnight to dawn.
Stars & Constellations
The constellations of Orion and Taurus can be found in the north-west after sunset. Taurus contains the beautiful Pleiades or Seven Sisters, a small cluster containing many young blue giant stars.
The brightest star in our night sky, Sirius (Canis Major), is nearly overhead at sunset. Its partner, Procyon in Canis Minor, is high in the north. The twin stars of Gemini, Castor and Pollux, lie low in the north-west while Regulus, in Leo, is low to the north-east.
The constellation of Virgo rises in the east after sunset. Sitting above Virgo is the kite-shaped group of stars that form Corvus (the crow).
In the Boorong tradition of north-west Victoria there is the woman drummer Larnankurrk (Pleiades) beating out the rhythm for the songman Gellarlac (head of Taurus) with two young men learning to dance Kulkunbulla (centre of Orion or the Saucepan). Nearby is the lawgiver the wedge-tailed eagle Warepil with wings stretched either side of his head (Sirius and Canis Major).
International Space Station
ISS orbits every 90 minutes at an average distance of 400km appearing like a bright star moving slowly across the night sky. Here are the brightest passes expected this month over Melbourne and South Central Victoria, two in the evening and two in the early morning:
- Wed 4 Mar 9.36pm–9.39pm South-West to South
- Sat 7 Mar 8.49pm–8.55pm West-South-West to North-North-East
- Wed 25 Mar 6.26am–6.32am North-West to South-East
- Sat 28 Mar 5.42am–5.45am South-South-East to South-East
For predictions go to heavens-above.com.
On this day
1st 1966, Venera 3 (USSR) crash lands on Venus as first probe to land on a planet.
2nd 1972, Pioneer 10 (USA) probe launched to outer solar system.
3rd 1969, Apollo 9 (USA) tests lunar module in Earth orbit for later moon landings.
4th 1979, Voyager 1 (USA) discovered the rings of Jupiter.
4th 1986, Vega 1 (USSR) transmits first view of Halley’s Comet nucleus.
5th 1590, Tycho Brahe discovered a comet and showed that comets are further away than the Moon.
5th 1979, two probes and a satellite are affected by ‘gamma ray bursts’ leading to study of these high energy phenomena.
5th 1979, closest approach to Jupiter by Voyager 1 (USA).
6th 1986, Vega 1 (USSR) made the first flyby of Comet Halley and returned the first close-up images of a comet.
9th 1934, birth of first human into space, Soviet cosmonaut Yuri Gagarin.
10th 2006, Mars Reconnaissance Orbiter (USA) goes into Martian orbit.
11th 1977, the rings of Uranus discovered as the planet eclipsed a distant star (USA).
13th 1781, Uranus was discovered by Sir William Herschel (UK).
13th 1930, discovery of Pluto is notified to Harvard College Observatory.
14th 1879, birth of Albert Einstein famous for photo-electric effect, relativity, and letter to US President Roosevelt on the power and destructive potential of the atom.
18th 1965, Aleksei Leonov (USSR) carried out the first spacewalk.
17th 1958, first solar powered satellite, Vanguard 1 (USA), is launched.
20th 1916, Einstein publishes his theory of gravity, the General Theory of Relativity.
23rd 2001, Russian space station Mir (‘Peace’) is destroyed in its planned re-entry to Earth’s atmosphere.
23rd 1912, birth of Werner von Braun famous for leading German rocketry in World War 2, and then key figure in US space program until the 1970s.
24th 1965, Ranger 9 (USA), first television of the moon before its crash landing.
24th 1993, Comet Shoemaker-Levy 9 is discovered 12 months before it breaks up and crashes into Jupiter.
25th 1655, Christiaan Huygens discovers Titan, the largest moon of Saturn.
27th 1969, Mariner 7 (USA) launched to Mars.
29th 1974, Mariner 10 (USA) is first probe to fly past Mercury.
30th 240BC, first recorded closest approach to the sun (perihelion) of Comet Halley.
31st 1966, first probe to orbit the moon, Luna 10 (USSR).