SEPTEMBER - 2023

Moon phases

PHASE DATE
Third Quarter Thursday 7th
New Moon Friday 15th
First Quarter Saturday 23rd
Full Moon Friday 29th

Moon distances

Lunar perigee (closest to Earth) is on Thursday 28th at 359,911 km. Lunar apogee (furthest from Earth) is on Wednesday 13th at 406,634 km.

Planets

Mercury is not visible this month after having passed in front of the sun. It is too close to our local star to be seen.

Venus can be seen in September in the dawn sky about two hours before sunrise, from 4.30am early in the month and a little earlier each morning.

Mars cannot be seen this month as it passes behind the sun from our point of view on Earth. After four months it will reappear in mid-February in the east as an early morning planet.

Jupiter is visible this month from 11.30pm in the north-east early in month and then a little earlier each night. It will move across the north before being lost in the early morning light by 6am.

Saturn is a beautiful planet to observe this month rising in the east from 6.30pm early in the month and then a little earlier each evening. Its subtle yellow tinge should make it obvious all night as it moves across the north and then to the west before fading by 5am.

Meteors

While not a good time for meteors this month the Southern Piscids will peak from 11th to the 20th. They usually number only a few per hour and appear in the constellation of Pisces, the fish, which rises in the north-west from midnight.

Find out more about these space visitors at NASA Asteroids, Comets and Meteors.

Stars and constellations

In the north

High in the north are Sagittarius (the archer centaur). Its bow and arrow forms the famous asterism The Teapot, the spout of which leads across the zenith to the curving tail of nearby Scorpius.

Lower in the north sits Aquila (the eagle) with Altair or Alpha Aquilae, the 12th brightest star at night. And quite low in the north is Lyre (the lyre) and its principal star Vega or Alpha Lyrae which is the 5th brightest star at night.

In the east

Directly east this month is a trio of adjacent constellations. In the centre is Aquarius, the water bearer while above is Capricornus (the goat), to its left sits Pisces Austrinus (Southern Fish) containing its main star and the 18th brightest star at night, Formalhaut (Alpha Piscis Austrinus).

In the south

Low in the south-west can easily be seen two of the brightest stars in the night sky, Alpha and Beta Centauri. These are the two brightest stars in the constellation of Centaurus (the centaur) with Alpha Centauri also known as Rigel Kentaurus (foot of the centaur). Together these two stars are referred to as The Pointers as they lead directly to the unmistakable diamond shape of Crux or Southern Cross. Crux is the smallest of the traditional 88 constellations astronomer use and is an easy feature of the night sky to observe, even in city surroundings.

In the south-east is the 10th brightest star, Achernar in the long constellation Eridanis (the river) that winds its way down to the horizon.

In the west

High in the west sits the curving tail, body and pincers of the scorpion, Scorpius. Within its body you should see red giant star Antares which will appear more orange than red in light polluted skies. In front of the Scorpion's wide head and closer to the horizon sits Libra (the scales).

On this day

1st 1939, Americans J Robert Oppenheimer and Hartland Snyder publish the first paper that describes the gravitational contraction of a star which later led to the modern concept of black holes.

1st 1859, Carrington Event, most powerful geomagnetic storm ever recorded. Now understood as a Coronal Mass Ejection (CME) from the Sun that hit Earth's magnetosphere inducing strong northern auroras almost to the equator, and telegraph interference in Europe and North America with operators receiving electric shocks, poles sparking, and signals sent despite power cut off.

1st 1979, Pioneer 11 (USA) made the first flyby of Saturn returning the first close-up images of the planet. It was the second probe to pass the asteroid belt and Jupiter and to reach solar escape velocity. Last routine contact was on 30 September 1995 and final data received was on November 1995.

5th 1977, Voyager 1 (USA) is launched to explore the outer Solar System. After 42 years it continues sending data and is the most distant probe at 21.8 billion km (146 AU). It entered interstellar space in 2012 and its power supply may last until 2025.

8th 2004, Genesis (USA) probe crashes in Utah while returning samples of solar wind particles. Some collecting panels survived impact and were recovered giving successful scientific results.

11th 1985, the International Cometary Explorer or ICE (USA) became the first spacecraft to encounter a comet by flying through the dust tail of Comet Giacobini-Zinner.

14th 1959, Luna 2 (USSR) was the first craft to fly to and impact another body, in this case the Moon. It released sodium gas to allow visible tracking, used radio for telemetry transmission, and crashed into Mare Imbrium (the Sea of Rains).

17th 1976, NASA unveils its concept for a Space Transportation System, a rocket launched and glider return orbiter known as the Space Shuttle.

17th 1857, birth of Konstantin Tsiolkovsky, a pioneering Russian then Soviet teacher whose theoretical work on aerodynamics and rocketry influenced all who followed. He advocated spaceflight and believed humans would colonise the galaxy.

18th 1977, Voyager 1 (USA) sends the first image of Earth and Moon together taken, from a distance of 11.6 million km while on its way to Jupiter.

21st 1633, the Roman Catholic Inquisition begins its trial of Galileo for heresy in publishing and advocating a heliocentric or Sun-centred solar system contrary to church doctrine, dogma and scripture.

23rd 1846, Neptune, first predicted by Urbain Le Verrier (France), is discovered by Johanne Gottfried Galle (Germany) with John Couch Adams (UK) recognised for an independent discovery.

27th 1905, Albert Einstein published his paper containing the famous equation E=mc2 (energy equals mass multiplied by the speed of light squared), meaning a small amount of matter is equivalent to, or can be converted into, a great deal of energy.