What’s up in the Sky this September

Article written by: Yanina Metodiva

This September is a relatively uneventful month (astronomy-wise). Few visible planets, quiet Sun and overall a very poor month for meteor showers.

The Sun is at the centre of the Solar System. Its gravity dictates the orbits of the planets. The Sun is 6000 degrees Celsius on its surface and 14,000,000,000 degrees Celsius at its core. Credit NASA/SDO

The Sun.
This month the Sun is moving away from the constellation Leo to Virgo. On the 23rd September at 2:54am BST, the Sun will reach the point of Autumnal Equinox, marking the beginning of autumn. On the equinoxes, both spring and autumnal, all over the world the night and the day have the same duration.

At the moment our Sun is very quiet, with a low number of spots appearing on its surface. Solar winds blow material from the Sun in the outer parts of the Solar system, and if they reach the Earth, they produce spectacular aurorae (northern lights). During the summer months, the nights are too bright for any aurorae to be spotted. But towards the autumn months, it is easier to spot them in the night sky. The aurora season started in the end of August, and another chunk of solar wind is about to reach the Earth in the next day or two.

More information on aurora predictions you can find on the following websites:
http://www.spaceweather.com/, https://www.swpc.noaa.gov/products/aurora-30-minute-forecast and http://www.aurora-service.eu/aurora-forecast/. If you wish to observe the northern lights (when possible), look north close to the horizon and you might spot the dancing green or red glow.

 

The planets.

Mercury. This September the closest planet to our Sun – Mercury, is very shy, hiding in the Sun’s shine. This means that Mercury will be impossible to observe this month.

Venus. In the beginning of September Venus sets around 9pm, towards the middle of the month – just after 8, and in the end of September – around 7pm. So basically, for the whole of September, Venus goes closer and closer to the Sun, trying to hide behind it.

Credit: NASA

Mars. In the end of July Mars was closest to us since 2003, making the red planet appear much bigger and redder than normal. Although Mars is moving away from us, it is still relatively close and perfect for observations. It is visible almost all night, setting just minutes before sunrise, making the red planet perfect for observations this month. It reaches maximum altitude above the horizon of 10 degrees in the beginning of September, and increases to 13-14 degrees towards the end of the month. The brightnes of Mars is about -2 magnitude, still one of the brightest dots on the night sky.

Jupiter. For the month of September, Jupiter will be trailing behind the Sun. The biggest planet will be setting 2 hours after the Sun, and will be visible in the sunset light. Roughly the same brightess as Mars. Visible directly after sunset in the south-west skies.

Saturn. The ring planet will be visible for the first half of the September nights. After the Sun sets you can find Saturn if you look directly south, at about 13 degrees above the horizon.

 

Credits: NASA/JPL

Meteor showers.

Following August with the Perseid meteor shower, September is a quiet month when it comes to meteors. There are five active showers with a very low number of meteors, on average about 5 per hour. If you wish to see some shooting stars, you might have to wait quite a long time in the nights of September, or wait until October’s Draconid and Orionid showers.

Of course you can still see shooting stars in September, but they will most likely not belong to any specific shower.

 

Comets.

Thoughout this year three comets will be bright enough to be spotted with binoculars or small telescopes. These are the comets 21P/Giacobini-Zinner, 38P/Stephan-Oterma and 46P/Wirtanen.

Comet 21P/Giacobini-Zinner. Credit: NASA

21P/Giacobini-Zinner was discovered in 1900, and has a period of 6.5 years.

This month the comet will be rising late in the evenings. Currently 21P is in the constellation Camelopardalis (The Giraffe), heading towards Auriga (The charioteer) and Monoceros (The Unicorn). The comet is now around 7th magnitude and forming a tail, making it easy to spot with binoculars. On the night of the 10/11th September, 21P will reach its closest point to the Sun, called a perihelion. 21P/Giacobini-Zinner is the parent body of the meteor shower Draconids, with a peak in early October. During the last perihelion of the comet, the maximum of the Draconids reached around 600 meteors per hour, making it a very attractive shower for observations and photography. During its travels through the sky, 21P will pass several deep-sky objects, making it attractive for astrophotography. On the night of 15th September, the comet will pass in front of the open star cluster M35. For more information on this comet, its current position and brightness,

visit http://www.cometwatch.co.uk/comet-21p/.

 

38P/Stephan-Oterma, discovered in 1867, has a long orbital period, returning close to the Sun once every 38 years. The perihelion occurred on the 26th August 2018, and the closest approach to the Earth will be in January 2019. For the period between these days, the comet 38P will be visible in the evenings, bright enough for small telescopes. For more information on this comet, its current position and brightness, visit http://www.cometwatch.co.uk/comet-38p/.

 

The comet 46P/Wirtanen was discovered in 1948, and it has an orbital period of 5.4 years.

It’s next perihelion is on 12th December 2018, when the comet is expected to reach magnitude 3, making it visible with the naked eye. If 46P reaches this brightness, it will be the brightest comet in the sky for the last 5 years. Six days after its perihelion, 46P will be closest to the Earth, at a distance only 0.078 astronomical units, or 11.6 million kilometers, and due to its proximity to us, it will appear bigger and easier for resolving in photographs.

For more information on this comet, its current position and brightness, visit http://www.cometwatch.co.uk/comet-46p/.

 

The ISS orbits the earth every 90mins. Credit: NASA

Spotting the International space station. 

The ISS is returning in September, after a month with no visible passes. For the first half of September, the ISS will have bright passes above the island of Ireland in the very early hours of the day, around 3-4am, and will be outshining all the stars and planets visible in the sky at that time. in the second half of September the ISS will be passing above us in the early evening hours, always going West-to-East, rising above the sunset and moving in the opposite direction of all stars and planets.

On rare occasions it happens that the ISS goes directly in front of our Moon or the Sun, making a very attractive pass. You can photograph these by using a camera with fast shutter speed, mounted on a tripod a splinted at the Moon at the time of the transit. Use short exposures one after the other as quick as your camera allows, or take a video with the highest possible resolution in order to see the silhouette of the space station going in front of the Moon. If you wish to observe or photograph a pass in front of the Sun, use protective filters for your binoculars, telescope or camera to avoid damaging your eyes or equipment! You can see the panels of the ISS if you observe it with binoculars!