The best of astronomy this month: Watch the Moon pass Venus, Jupiter and Antares over the evenings of the 12th-15th September.
By Dhara Patel, Astronomy Education Officer
(Details given are for London and may vary for other parts of the UK).
Top 3 things to see this month:
- Throughout the month - Look south for the Summer Traingle star pattern in the early evening with Mars and Saturn below.
- 12-15th Sep - Catch the Moon move past Venus, Jupiter and the star Antares over several evenings looking towards the south-west after sunset.
- 30th Sep - Spot the waning gibbous moon beside the star Aldebaran in the east after midnight.
Look Up! Podcast
As well as taking you through what to see in the night sky each month, Royal Observatory Greenwich astronomers pick their favourite astro news story. For September, they're chatting about the recent launch of the Parker Solar Probe and what it aims to uncover about our Sun and the perhaps surprising achievements of the Spitzer Space Telescope with it just having celebrated it's 15th birthday! Have a listen below then vote for your favourite news story on our Twitter poll during the first week of the month.
Our podcast is available on iTunes too - search Look Up! and rate us if you enjoyed listening.
The Summer Triangle star pattern or asterism sits high in the south / south-western sky throughout the month in the early evening. The bright trio of stars – Vega, Deneb and Altair mark out a triangle which lies right over a portion of the Great Rift – a complex of dark dust clouds that appear to divide the cloudy band of light that is the Milky Way. The galactic disk of our galaxy can be seen on a dark night with just your eyes arching across the sky.
Further to the south-east, the constellation of Pegasus sits proudly in the sky. It’s easily identifiable by searching for the 4 bright stars making up a square shape known as the Great Square of Pegasus. About half way between Altair and Markab (the star at the bottom right corner of the Great Square) lays M15 – the Pegasus globular cluster. This cluster is home to over 100,000 stars and is estimated to be one of the oldest known globular clusters with an age of 12 billion years. It’s bright enough that it approaches the naked eye limit with very good viewing conditions, but is far more easily observed with a pair of binoculars or small telescope as a ‘fuzzy’ looking star.
On this evening, the young crescent moon will sit above Venus in the south-western sky just after sunset. Return to your viewing spot at the same time over the following evenings to see the Moon move across the sky as a result of it orbiting around our planet. By the 13th, the Moon will be closer to Jupiter (nearer the south) and on the 14th will have passed the gas giant. Then on the evening of the 15th, look below the Moon and closer to the horizon, you could spot Antares - the bright red star of the constellation of Scorpio.
Antares is a star that lies close to the ecliptic (the sun’s apparent path across the sky throughout the year). Since our solar system is like a flat disk shape, the Moon and planets’ celestial paths lie close to the ecliptic too. This means that we often find the Moon and planets close beside stars like Antares and other which lie close to the ecliptic like Aldebaran in the Constellation of Taurus, Spica in the constellation of Virgo and Regulus in the constellation of Leo.
The Moon reaches first quarter on the 16th – a great time to look for craters on the Moon using binoculars or a telescope and pointing them towards the terminator – the boundary between the light and dark sides on the Moon. By the 17th, the Moon will have nestled close beside Saturn in the constellation of Sagittarius. Look to the south in the early evening. Not too far from the pair (further to the east) you’ll find Mars in the constellation of Capricornus – another of the naked eye planets. You’ll be able to spot Saturn and Mars throughout the month in the south.
After a very hot and bright summer, we’re heading into autumn. The start of the season is marked by astronomers as the autumnal equinox which falls on the 23rd September. The autumnal equinox in the northern hemisphere (in the UK) marks when the Sun moves from being overhead in the northern hemisphere and crosses below the celestial equator where the Sun will lie directly above the southern hemisphere. On the day of the equinox we will have approximately the same number of hours in daylight and in darkness and from then on our days will begin to grow shorter and our nights longer until we reach the winter solstice in December.
By the end of the month, the waning gibbous moon will be beside the red giant star Aldebaran in the constellation of Taurus. Look towards the east after midnight. Just below the constellation of Taurus, Orion the hunter is starting to creep above the horizon and over the next few months it will become a more dominant constellation in our winter sky to look out for.
The Moon's phases this month
- 3 Sep - last quarter moon (2:37am)
- 9 Sep - new moon (6:01pm)
- 16 Sep - first quarter moon (11:15pm)
- 25 Sep - full moon (2:15am)
The winners of this year's competition will be announced on 23 October 2018.
- When looking at faint objects such as stars, nebulae, the Milky Way and other galaxies it is important to allow your eyes to adapt to the dark – so that you can achieve better night vision.
- Allow 15 minutes for your eyes to become sensitive in the dark and remember not to look at your mobile phone or any other bright device when stargazing.
- If you’re using a star app on your phone then switch on the red night vision mode.
- Need a stargzing telescope or decent binoculars? Check out our range of high quality observing equipment recommended by Royal Observatory astronomers:
Shar your astronomy pictures
Congratulations to Peter Jenkins for his beatiful image of the night sky. He shared his image on our astrophotography Facebook page and we chose it for September's banner image.
If you want to be in with a chance to showcase your astrophotography skills on the banner of next month's night sky blog, share your photos via our Royal Observatory Astrophotography Facebook group
You can also connect with us on Twitter: @ROGAstronomers
Hubble Vision - gallery exhibition
Come and see some of the most spectacular images taken by the Hubble Space Telescope in our new free exhibition at the Royal Observatory Greenwich.
The exhibition is open daily until 12th May 2019.
See more of the night sky
Come on an amazing tour of this month's night sky in our Sky Tonight planetarium show delivered live by a Royal Observatory Greenwich astronomer.
Central image:© Peter Jenkins
Resources for teachers and students
The Royal Observatory learning team have also created:
- Free animated videos that answer the biggest questions in astronomy and free resources to go alongsie them
- A whole host of podcasts featuring interviews with real space scientists, astronauts and active researchers working in UK Universities.