Find out what to go out and look at this month
Mercury and Venus will be very low in the Western sky this month. Mercury will appear in the constellation of Taurus (The Bull) in the middle of the second week of May. It will reach its greatest elongation in the West on the 17th of May and it’ll begin to make its way back towards the Sun before disappearing again in the Sun’s glare at the end of the month. Venus will move from the constellation of Aries (The Ram) into the constellation of Taurus in the middle of the first week of May. Mars will be located at the start of the month in the constellation of Gemini (The Twins) in the North-Western evening sky. At the start of the month, Mars will set at 08:54 pm (AWST), but by the end of the month, it’ll set at 08:21 pm (AWST).
Jupiter and Saturn can be found in the Eastern sky in the early morning sky. Jupiter can be found in the constellation of Aquarius while Saturn can be found in the constellation of Capricornus (The Sea-Goat) during May. At the beginning of the month, Jupiter will rise at 01:07 am (AWST) and Saturn will rise at 11:51 pm (AWST). By the end of the month, Jupiter will rise at 11:21 pm (AWST) and Saturn will rise at 09:54 pm (AWST). Neptune will be viewable as well in the early morning between the constellation of Aquarius and the constellation of Pisces. At the start of May, Neptune will rise at 03:00 am and by the end of the month, it’ll rise at 01:06 am (AWST).
Conjunctions And Occultations:
Conjunctions involve object(s) in the Solar System and/or more distant objects, such as a star. It’s an apparent phenomenon in which multiple objects which aren’t close together appear close in the sky and it’s caused by the observer’s perspective. An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer.
- 03/05/21 – Alignment of The Moon, Jupiter and Saturn (Where to look)
- 04/05/21 – Conjunction of The Moon and Saturn (Where to look)
- 05/05/21 – Conjunction of The Moon and Jupiter (Where to look)
- 14/05/21 – Alignment of The Moon, Mercury and Venus (Where to look)
- 16/05/21 – Conjunction of The Moon and Mars (Where to look)
- 17/05/21 – Conjunction of The Moon, Castor and Pollux (Where to look)
- 23/05/21 – Conjunction of The Moon and Spica (Where to look)
- 26/05/21 – Conjunction of The Moon and Antares (Where to look)
- 29/05/21 – Conjunction of Mercury and Venus (Where to look)
- 31/05/21 – Conjunction of The Moon and Saturn (Where to look)
Astronomical Events This Month:
The Eta Aquarids Meteor Shower:
Starting early in the morning of the 6th of May the Eta Aquarids meteor shower be at its peak. The shower is active from the 19th of April through to the 28th of May, and its normal meteor per hour rate can vary between 10 – 20 meteors per hour for Perth. Unfortunately, the last quarter Moon will be in the Aquarius constellation, so you’ll see a reduced number of meteors this year.
The cause of the Eta Aquarids is the famous Comet Halley, named after Astronomer Edmund Halley, who first determined in 1705 that the comet was periodic. The Eta Aquarids are one of two meteor showers caused by Comet Halley, with the other shower being October’s Orionids. Halley’s orbit around the Sun takes 75 years with the next entering the inner system again in 2061.
The meteors will seem to appear from the Aquarius constellation which gives the meteor shower its name. Aquarius will appear in the sky over the Perth hills around 11:30 pm so you should go out around 4:00 am and give your eyes 15 minutes to fully adjust to the lighting conditions and look between North and North East. While it’s always best to find a nice park or a large open space for the best viewing of a meteor shower, you can go out to our front or back yard and still get a good view.
Total Lunar Eclipse:
On Wednesday the 26th of May, the Moon passes within Earth’s inner shadow called the Umbra (Latin for shadow) in what’s called a Total Lunar Eclipse. At the start of the eclipse, the Earth’s shadow first darkens the Moon slightly as it moves through the Earth’s outer shadow called the Penumbra (from the Latin paene “almost, nearly”). Then the Umbra begins to slowly cover the Moon before turning it an orange colour. The orange appearance of the Moon is due to Rayleigh scattering where the blue part of the light hitting the Earth’s atmosphere is scattered by the nitrogen molecules and the red and yellow part of the light continues through the atmosphere and goes on to hit the Moon.
This is the only Total Lunar Eclipse for 2021 and it will begin at 4:47 pm (AWST) while the Moon is below the horizon for Perth. Don’t worry we’re not missing out the first penumbral phase of the eclipse will be happening at that time so it’s hard to notice. The Moon rises above the horizon at 5:16 pm (AWST) about half an hour before the first partial phase begins where you’ll notice the Moon starts to be eaten away by the Earth’s shadow. Totality, where the Moon will be orange begins at 7:11 pm (AWST) and finishes at 7:25 pm (AWST) so it will only be 14 minutes this year. The second partial phase ends at 8:52 pm (AWST) and then the second penumbral phase and the eclipse itself ends at 9:49 pm (AWST). The total duration of this eclipse will be 5 hours, 2 minutes
Perth Observatory will be having an event on the night so you can bring your camera and outdoor chair or even a bean bag and enjoy watching the Moon become blood orange. Hot drinks will be provided on the night and Perth Observatory volunteers will be on hand to chat about why the Eclipse is happening and answer any questions you have. We’ll also have some telescopes set up so you can view the Moon up close as well. To book go to our Total Lunar Eclipse page.
Things To Look At This Month:
The Eight-Burst Planetary Nebula (NGC 3132) also known as the Southern Ring Nebula is a bright planetary nebula in the constellation Vela. It’s 2,000 light-years away from us and is 0.4 light-years across. The name “planetary nebula” refers to the round shape and in reality, it has nothing to do with planets but due to it appearing like a planet. The round shape is huge shells of gas ejected a star as it nears the end of its life and is expanding away from the central star at a speed of 15 km per second.
Images of the nebula show two stars close together within the nebulosity with the white dwarf that created the nebula being the fainter of these two stars. The white dwarf is at a temperature of 100,000 K and has now blown off its layers. The intense ultraviolet radiation that comes off the white dwarf is making the nebula fluoresce brightly.
Centaurus A Galaxy:
Centaurus A or NGC 5128 is an elliptical galaxy that we see edge-on. The galaxy is the fifth brightest galaxy in the sky and one of the closest radio galaxies to earth. It’s between 10 to 16 million light-years away from us and It can be found in the Centaurus constellation. The galaxy itself has a diameter of 60,000 light-years making it 40% smaller than our galaxy and at its centre, it has a supermassive black hole with a mass of ~55 million suns. It was discovered in 1826 by Scottish astronomer James Dunlop from Parramatta, in New South Wales.
It’s a starburst galaxy meaning that it is undergoing a period of intense star formation compared to an average galaxy. Studies have confirmed that this high rate of star birth is caused by a collision between itself and a smaller spiral galaxy. The bright central bulge and the dark dust lane can be easily viewed using an amateur telescope however a larger telescope is required to view greater detail and contrast. Centaurus A is an extremely bright radio object, X-Rays in particular. The central supermassive black hole is the source of this with two long radio jets extending well beyond the visual bounds of the galaxy.
The Jewel Box:
An open cluster the Jewel Box can be found very close in the Crux (Southern Cross) Constellation, the Jewel Box is located some 6,440 light-years away from Earth and is 14 light-years across. The cluster contains just over 100 stars, and with an estimated age of its stars being just 14 million years, this star cluster is one of the youngest clusters that we’ve found. The Jewel Box cluster also has some of the brightest stars in the Milky Way galaxy. These stars are supergiants and the red, white and blue stars in the centre of the cluster look very much like the lights of a traffic light.
Eta Carinae And The Carina Nebula:
Variable brightness and Colour, Eta Carinae is one of the most remarkable stars in the heavens. When we say “Eta Carinae” we refer to the star itself which for Perth is a circumpolar star (We see the star all year round) and not the nebula.
Eta Carinae is 100 times the Sun’s mass and 4 million times brighter, this brightness has been unstable with the star being recorded over the past 300 years between magnitude -0.8 which is as bright as Canopus and +7.9. It’s a star that’s sometimes in the news as it’s expected to become a supernova within the next 1 million years and will be a spectacular sight when it occurs, being visible by day and possibly bright enough to read by at night.
Eta Carinae is very likely a binary star with the smaller partner orbiting in a highly elliptical orbit of 5.5 years. The Carinae Nebula (NGC 3372), which surrounds Eta Carinae, is a large, bright star-formation region that has produced several very massive stars including Eta Carinae. At around 260 light-years the Carina Nebula is around 7 times the size of the Great Orion Nebula, but due to its greater distance, it only spans twice the width. There are many O-type stars, young (~2 million years), hot and bright that energise the entire Eta Carinae nebula.
Omega Centauri or NGC 5139 is the largest and brightest globular cluster of 180 in the Milky Way and is the second-largest known, with only Mayall II in the Andromeda Galaxy being larger coming ins about twice its mass. The Globular cluster is located in Centaurus Constellation and it’s a naked eye ‘star’ and visible in binoculars as a ‘fuzzy blob’. Omega Centauri contains at least 3 million stars and the cluster has a diameter of roughly 150 light-years and the stars are roughly 12 billion years old. The average distance between the stars at the centre is around 10% of a light-year or more than 100 times the diameter of our solar system. It may be a dwarf galaxy that has been captured and disrupted by the Milky Way galaxy and measurements of its star movement by Hubble has indicated that a black hole may be located at the core of the cluster.