Instructions to read before looking up – September night sky
- Learn what is September and what we do with it,
- Find out what’s the Sun up to,
- Find out what’s in the Milky Way,
- Find out what Orion and Scorpius are up to
- Find out what are the brightest stars visible at night after sunset and finally find out about our favourite binocular and telescope objects.
A bit about September
September comes from Latin word “septem”, which means “seven.” This is because in the old Roman calendar it was the 7th month, rather than 9th as it is today. Old Roman calendar used to only have 10 months until Julius Caesar introduced a new Julian calendar with 12 months. September has 30 days and marks the Autumn season in the northern hemisphere, and Spring in the Southern Hemisphere. This is the time of harvest and when many schools start their new school year in the northern hemisphere.
Here, in New Zealand it is the month when we celebrate the September equinox, when the day is equal to the night.
What’s the Sun up to?
The Sun rises at 6:47 am on the first day of September and earlier and earlier every day so that on the 28th of September it will rise at 6:01 AM. However, the clock will shift by one hour on the night of the 29 September so on the 30th of September it will rise at 6:57 am. The sun sets at 5:55 PM on the 1st of September and later and later 7:24 PM on the 31st of August. The days are getting longer. September 23rd marks the September Equinox, or the “vernal equinox”, the word vernal means spring in Latin. At the equinox, the day and night are roughly the same length. The word “equinox” comes from Latin words “equal” and “night”. As the month goes, the days will be longer than nights until we reach Summer Solstice. The equinoxes only occur twice per year so this is a very special astronomical event of the year and you experience it every September!
Spring begins on the 1st of September
Since 1870s New Zealand used the meteorological dates to mark the beginning of spring, thus spring here begins on the 1st of September!
- People who come here from the Northern Hemisphere usually miss this, and they think of the beginning of spring with the autumnal equinox. But just for the sake of the argument, according to WeatherWatch Managing Director Philip Duncan, there are actually four ways to start a season:
(1) looking at astronomical dates, which would place the date on September 22 or 23, based on the equinox,
(2) by meteorological dates – which is a three-month division of the year into seasons, thus Spring starts on September 1,
(3) observing the solar winter, which is the three “darkest” months with the June 21-22 winter solstice in the middle, which shifts the beginning of spring to August 8 and
(4) looking at what nature does, which in New Zealand is hard to pin down.
- 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.
In September, the Sun transits first the zodiacal constellations of Leo, and then moves into Virgo on the 17th of September where it stays until October 31st. The zodiacal constellations are those stars visible behind the plane of our solar system, about 8 degrees each side of the ecliptic. This is why we say they form a band in the sky, called the Zodiacal Band. Since the Sun is transiting both the space we call Leo and Virgo it means we cannot see the stars in these constellations, they are behind the Sun.
It’s dangerous to look into the Sun!!
Of course, if you have solar telescope, that is well maintained and is designed for looking at the Sun, then you can look at the Sun.
The Sun in Virgo means only one thing: opposite the Sun (that 180 degrees on the other side of the zodiacal band) is Pisces. Pisces will rise just after sunset and be visible all night long.
The Milky Way and Zodiacal Light
Here in Aotearoa, in September, the constellation of scorpius is the Fishhook of Maui that drags the Milky Way down from the sky. We still get to admire the amazing galactic centre and the Milky-Way.kiwi inside it.
Many cultures and languages have various names for the Milky Way. In Kazakh, the Milky Way is called “құс жолы,” meaning the “bird’s road” (Alina Sabyr).
In addition to the Milky Way, if you are stargazing from somewhere with very dark skies, you can spot what is called the “Zodiacal Light” It’s a cone-shaped light that stretches from low on horizon along the ecliptic. The ecliptic marks the plane of our solar system bearing the zodiacal constellations. The ecliptic is “a great circle on the celestial sphere representing the Sun’s apparent path during the year, so called because lunar and solar eclipses can only occur when the moon crosses it. The zodiacal light is the light we see reflected from dust and ice particles in the plane of our own solar system! How cool is that? So in the sky we can see both the galaxy that we inhabit and the solar system. Two completely different scales!
Scorpius, Centaurus and Southern Cross
At this time of the year, in Aotearoa, the Māori names for Scorpius is Te Matau A Maui – the fishhook of Maui that drags the Milky Way from the sky all night long. This is alluding to the fact that after sunset you can see the fish hook at Zenith and then falling down towards the western part of the sky.
The constellation Scorpius has a magnificent red supergiant star Antares. It is impossible to miss on a clear night. It looks quite reddish, just like planet Mars! In fact, its name is derived from Greek, meaning “rival to Ares,” Ares being Greek reference to planet Mars.
South of Scorpius you can find the constellation of Centaurus, a creature that is half-human and half-horse in Greek mythology. Although the constellation itself is more difficult to discern, it contains two very well known star systems in the southern hemisphere: Alpha and Beta Centauri. Alpha Centauri is the closest star system to Earth! It’s about 4.37 light years away so it takes light about 4.37 years to reach it. As a reference, it takes about 8 minutes for light to reach us from the Sun! It is a triple star system and there was an exoplanet discovered orbiting Proxima Centauri, one of the three stars in this system.
Alpha and Beta Centauri can be used as pointers to what is arguably the most well-known constellation in the southern hemisphere, the Southern Cross or Crux. It is on the New Zealand flag! It is seen year-round in New Zealand, and is a circumpolar object in New Zealand.
Circumpolar objects to New Zealand
What does circumpolar mean?
Circumpolar are objects that rotate around the celestial pole. These objects are above the horizon at all times in a given latitude. For instance Casiopeea is circumpolar from Europe but here in Wellington we cannot even see it, it’s hidden by the Earth. We could if Earth would have been transparent. Here on the other hand we have the Southern Cross with the pointers that are circumpolar.
The Diamond Cross and the False Cross are circumpolar too. Canopus and Achernar are also circumpolar. The same for the Magellanic Clouds, Omega Centauri, 47 Tucanae, the Jewel Box, the Southern Pleiades, the Gem Cluster and Omicron Velorum. Being circumpolar it means they turn around once every 23 hours and 56 minutes. That’s why they are always somewhere else in the sky.
In September, in the evenings, you will find the Southern Cross in the south western part of the sky. So just after sunset is at the 3 o’clock position heading down followed by the pointers. Canopus would be at the same time grazing the southern horizon so hard to see from hilly Wellington. Achernar and the two Magellanic Clouds would be in the south eastern part of the sky.
As it is opposite Scorpius, Orion will appear in the Eastern horizon as Scorpius sets in the western horizon, and at this time of the year is in the early morning sky.
On the Ecliptic
In addition to stars that we have already mentioned, we have a few more to mention.
As seen from Wellington the ecliptic runs through the northern part of the sky. That’s why everyone here looks for houses that face north. Very close to the ecliptic are Spica in Virgo early in the month. Spica means “head of grain” from Latin, it’s the grain that Virgo is holding. We can also see stars Zubenelgenubi and Zubeneschamali in Libra, and Nunki in Sagittarius. The ecliptic intersects the Milky Way in Scorpius.
Stars in the Milky Way
Starting from the centre of the Galaxy, going North are Shaula, the stinger of Scorpius and Atria in Triangulum Australe.
Other Bright stars:
In the north, we can see the bright star Altair in Aquila, the constellation of the eagle, a triangle-shaped constellation in north-eastern skies. Canopus, the brightest star in the southern hemispheres continues to shine bright and can be seen near horizon in southern skies.
Other than the Milky Way Kiwi that can be photographed at length this time of the year, the other famous dark patch is the Coalsack, near the Southern Cross. The coalsack is also known as the flounder, which is the Māori name for it. In deed, if you find a truly dark sky, you will see the resemblance.
However, talking about naming objects in the sky, the name of Coalsack is also very appropriate as the dark patch, made of interstellar dust matter holds inside it the Jewel Box, or the Kappa Crucis Cluster, NGC 4755.
Other deep sky objects in September
Some of the deep sky objects that you can point to with a telescope are the Butterfly Cluster (M6), an open cluster in the constellation Scorpius, Wishing Well open cluster (NGC 3532) in Carina and Southern Pinwheel Galaxy in Hydra.
Planets in September 2019
Listen to our September 2019 podcast on Galactic conversations
Thanks to Alina Sabyr for her contribution to this post.