First month of autumn in the Southern Hemisphere
As autumn starts in the southern hemisphere, at nightfall, half of our galaxy, the Milky Way, arches across the night sky from NNE to SSW like a river flowing through the heights of the heavens. It’s edge is towards the western horizon and its center rises in the east. At the fringe of our milky city of stars, on the north-western horizon, the Pleiades, the Shining Ones (Te Tawhiti) are preparing for the journey to the underworld. They are to disappear shortly behind the Sun and will stay there for a while.
And the explanation goes that since people of old did not really have an explanation about space, in trying to figure out where exactly the Pleiades went, they invented a underworld. This is probably one of the reasons why this group of stars is so linked to stories of death, rebirth, and ancestors, and used to mark the beginning of the year in some cultures. The Pleiades are a very special group of stars. They are located in the zodiacal constellation of Taurus, one degree from the ecliptic, which is the width of your pinky if you hold it at arm’s length. That is if you can find the ecliptic, of course!
The ecliptic is an imaginary line. It marks the path of the Sun in the sky. Therefore you can see the Pleiades practically from any place on Earth, any place where you can see the Sun. They are very famous. People of old measured the quality of their eyesight by counting how many stars they could see there. Probably still six, even if they are called the seven stars, as the seventh married a mortal about two thousand years ago and was demoted from the heavens (according to an ancient Greek legend). Being so bright, packed, and visible most of the time, makes them unique among the objects that we can see in the night sky.
What do we see when we look at the sky?
Children looking at the sky always fascinated me. First they see the Moon, then as they get used to that, they start to see the planets as the brighter dots of light. The Pleiades are among the first stars in children’s stories and they are indeed cyphered in many cultures of the world, almost all of them referencing the cluster.
However, one culture above all has given it different names at different times of the year. This is the Maori culture. The following saying can be found in Taumata O Te Ra Marae:
“Ko Ranginui te atua matua, ka tuku taku ihi he atua, ka tuku taku ihi he tangata.” — The many stars adorn me. Puanga, Rehua, Takurua. They are here. — But Matariki only comes once a year and at the same time each year. It is the sign of the Maori New Year.
We shall await the return of Matariki – Pleiades and watch them rising before the Sun, after the longest night of the year, here in Aotearoa.
Until then, we should bid farewell to Te Tawhiti – Pleiades as they slowly drop from the western horizon into the world of light.
Above the Pleiades, orange Aldebaran, is also descending from the heavens. Climbing up on the Milky Way, Betelgeuse and the big Egyptian dog Sirius lie on one side of the celestial river whilst Procyon, the small Egyptian dog, lies on the other side. The three make a beautiful triangle. Its tip, marked by Sirius, the brightest star in the sky, points at Canopus – Atutahi, the cat star, as I call it, the second brightest in the sky, which, like a good cat, is watching over the Earth from above. High in the sky, Canopus marks the midpoint between the center of our galaxy and its edge. The Milky Way then flows down from the sky through the False Cross, the Diamond Cross and the Southern Cross. The pointer stars hang from it: Beta Centauri, and the third brightest star in the sky and our closest neighbour, Alpha Centauri. Low on the eastern horizon the Milky Way ends in Sargas the first brightest star to rise from Scorpius. Theta Scorpii (θ Sco, θ Scorpii) has the traditional name Sargas, which it is believed to be of Sumerian origin. Sargas appears on the flag of Brazil, symbolising the state of Alagoas.
The Milky Way splits the sky of March in two:
The zodiacal sky
through the northeastern horizon runs the ecliptic, a lower arch, the plane of our solar system bearing the zodiacal constellations. They intersect the Milky Way right on the horizon.
Zodiacal constellations visible on the evening sky of March
In the evening sky you can see Taurus (just setting), Gemini, Cancer, Leo, Virgo, Libra and the first stars of Scorpius rising. The ecliptic is, as I said before, the apparent path of the Sun on the celestial sphere. It also refers to the plane of this path, which is coplanar with the orbit of Earth around the Sun (and hence the apparent orbit of the Sun around Earth). The orbits of the planets are also coplanar because during the Solar System’s formation, the planets formed out of a disk of dust which surrounded the Sun. Because that disk of dust was a disk, all in a plane, all of the planets formed in a plane as well. Rings and disks are common in astronomy. And since our eight planets orbit roughly in the same plane, if you ever wonder where to see them in our sky, turn your gaze towards the ecliptic. Chances are that bright stars that shine on roughly the same path where you would normally see the Sun in the daytime, are in fact planets. Planets are wanderers through the ecliptic, which is exactly what the name planithos meant in Greek: wanderer. They are following their own avenues in the celestial silence, and their positions are given by coordinates called ephemerides. And since we put astro into biology, or the other way around, you might also wish to know that ephemerides are also some insects in the Amazon jungle, that only live one day.
The Grand Clock of the South (the south celestial circle)
On the left we just looked at the part that holds the ecliptic, which in the Southern hemisphere, here in Wellington New Zealand, is located on the North part of the sky. Let’s do some star hopping to get to the other side, in the South. One of my favourite sports, star hopping is jumping from bright star to bright star, to reach fainter stars. Ready, set, go! We’ll start just above Virgo’s brightest star, Spica and try to locate Corvus, the raven, one of my favourite constellations. Corvus is now flying on the eastern horizon at 20 degrees of south declination but 2000 years ago it lay equally on each side of the celestial equator. Spica and the two stars of Corvus, Algorab and Gienah are in a line. The other side of the quadrilateral that is Corvus, Algorab and Kratz (Beta corvii) make another line that extends all the way to the grand Omega Centauri globular cluster, which is still on the Northern side of the Milky Way. Further down, following the same line, you find Alpha Centauri, the third brightest star in the sky and our closest neighbour. Alpha Centauri and its pointer companion, Beta Centauri, point at the Southern Cross. Don’t be fooled… there are many crosses in the Milky Way, only one is the Southern Cross. Higher up than the Southern Cross, the Diamond Cross carries a mirror image of the Pleiades. As they prepare for their journey to the underworld at the fringe of our milky city of stars, on the north-western horizon, the Pleiades, the Shining Ones (Te Tawhiti) leave behind, here in the southern hemisphere a doppelgänger, the look alike, fake twin that never leaves the sky. Circumpolar to Wellington, the Diamond Cross can also be found by climbing up the milky river, two thirds from the side and one third from the center this is where you will find the optical asterism (pattern of stars) of the diamond cross. At the eastern end of it, a pair of binoculars will reveal ‘the Southern Pleiades’, which is a group of stars that at first sight look like the letter M to me. Theta Carinae cluster, also called the “Southern Pleiades” has an astronomical resemblance to the famed northern star cluster M45 in Taurus. Even though the cluster is NOT dipper-shaped like the Pleiades, is also easily visible with the naked eye, (but best in binoculars), quite young… about 30 million years old and at almost the same distance from Earth (500 light years away). And just like M45, the Southern Pleiades is 15 light years across. And finally, on the other side of the Milky Way, in the south western sky, the Magellanic clouds are our neighbouring galaxies, circumpolar here in Wellington and always a little elusive to direct sight. The Magellanic clouds are the best training objects for averted vision, always look for them a little off to the side, while continuing to concentrate on them.
What you can’t see:
- Aquarius (Sun in Aquarius from 17th of February to 11th of March) and
- Pisces (Sun in Pisces from 12th March to 8th April)
This is the Zodiacal band, an awesome drawing by Eugene Georgiades. Since one thousand years ago, when people stopped taking precession into account, the zodiacal constellations have shifted. Yes, we are once again not what we think we are. Here is an excellent site with more details about your real star sign.
Featured sky: the star Sargas
Lower on the eastern horizon and close to the ecliptic, the third brightest star in the constellation of Scorpius is just barely visible. “It was the Euphratean Sargas, lying in the Milky Way just south of lambda (λ Shaula) and upsilon (υ Lesath), with which it formed one of the seven pairs of Twin Stars; as such it was Ma-a-su. And it may have been, with iota (ι), kappa (κ), lambda (λ Shaula) and upsilon (υ Lesath), the Girtab of the lunar zodiac of that valley, the Vanant of Persia and Vanand of Sogdiana (an Iranian people), all meaning the “Seizer,” “Smiter,” or “Stinger”; but the Persian and Sogdian words generally are used for our Regulus. In Khorasmia these stars were Khachman, the Curved.”
Sargas is the most southerly bright star in the Scorpion, closely anchoring the southern curve of the scorpion’s tail, and is invisible north of latitude of 50° N. The star’s southerly position has allowed northern observers to use its visibility as a test of the night-sky brightness near the horizon.
On the first of March, Autumn officially started in the Southern Hemisphere. it’s a time of plenty, of harvest and the beginning of the spectacular season of stars.
Clear and dark skies from the southern hemisphere!
Special Thanks go to the amazing Rhian Sheehan, Peter Detterline, Chief Astronomer of the Mars Society, Alan Gilmore from University of Canterbury and to Toa Nutone Wii Te Arei Waaka from the Society for Maori Astronomy and Traditions.
Listen to the March 2016 starrytelling podcast here