If you are planning to stay up late or head out of town this weekend, you may see a couple of shooting stars streak across the sky.
The annual Orionid meteor shower is at its peak between the very early hours of Friday, October 21 to Sunday, October 23, with the best rates expected early on Sunday morning.
"If you've got a clear sky you should see a few meteors," amateur astronomer Ian Musgrave says.
The Orionids is created by Earth moving through a trail of debris left behind by Halley's Comet, which also produces a meteor shower earlier in the year known as the Eta Aquariids.
As the name suggests, the point in the sky that the Orionid meteors come from — known as the radiant — is in the constellation of Orion.
"I always love the Orionids because it signals the beginning of summer, bringing Orion back into the sky again," says astronomer Tanya Hill of the Melbourne Planetarium.
Orion is locked in a cosmic — and mythological — battle with Scorpius, which dominates the night sky during the winter months and disappears when Orion rises.
This year the celestial elements are aligned for a better-than-average show.
If you look up between 2am and 3am, the waning crescent Moon is still below the horizon so skies will be darker, especially on Sunday night.
The meteors should be easy to spot shooting out from between Mars and the giant red star Betelgeuse (Orion's shoulder) high above the north-eastern horizon.
Mars and Betelgeuse also form a triangle with Aldebaran, the giant red star that forms the eye of Taurus, the bull.
"Having the three red objects in a triangle is always quite fun," Dr Hill says.
So how many meteors will you get to see?
While the northern hemisphere is talking up the Orionids as the best meteor shower of the year with between 10 and 40 meteors per hour, the rates are much less prolific in the southern hemisphere.
Dr Musgrave predicts we can expect to see, on average, a meteor every four minutes.
"You're not going to see lots and lots because the radiant never rises very high in Australia, but they are quite nice," he says.
If we are lucky, though, there is an outside chance the meteors could put on a special display, Dr Hill says.
There is evidence that the meteor stream is pushed around by the gravity of Jupiter, causing them to become more active every 12 years.
"The last time that happened was 2006/2007 when the number of meteors doubled," she says.
The further north you are, the better.
Here's a table showing the expected average rates for dark sky locations at latitudes equivalent to some of Australia's major cities and towns (rates in urban areas affected by light pollution will be lower).
Location |
Fri Oct 21 |
Sat Oct 22 |
Sun Oct 22 |
|---|---|---|---|
Adelaide |
10/hr |
13/hr |
14/hr |
Brisbane |
11/hr |
15/hr |
16/hr |
Cairns |
12/hr |
17/hr |
19/hr |
Canberra |
9/hr |
13/hr |
14/hr |
Darwin |
13/hr |
18/hr |
19/hr |
Hobart |
8/hr |
11/hr |
11/hr |
Melbourne |
9/hr |
12/hr |
13/hr |
Perth |
10/hr |
14/hr |
15/hr |
Sydney |
10/hr |
13/hr |
14/hr |
If you miss this year's Orionids altogether, don't despair. The best meteor shower in Australia — the Geminids — is just two months away.
Do you need anything to see them?
Orionid meteors tend to be very bright and fast.
"They can often leave gorgeous trains behind where the meteor shoots past but it kind of persists for a second or two," Dr Hill says.
You might even spot a couple of slower meteors in the same area coming from different meteor showers known as the Southern and Northern Taurids.
You don't need anything other than your eyes, a nice dark site, and a lot of patience (even though we said one every four minutes, we didn't literally mean every four minutes.)
To catch meteors, you need to scan the sky, rather than stare at one spot.
"Let your eyes move around, because even though the radiant is at the point where the meteors appear to originate from, most of them start burning or glowing away from that point," Dr Musgrave says.
But wait! That's not all
If you do have some binoculars or a telescope, check out Mars while you are waiting (just be careful you don't miss the meteors).
"Mars will be at opposition next month, so it is continually getting brighter," Dr Musgrave says.
If you turn away from the meteor shower to the west you will also see Jupiter, which recently reached opposition and made its closest approach to Earth in nearly 70 years.
"Jupiter is looking so lovely and bright at the moment," Dr Hill says.
And don't forget to take a closer peek at the bright stars in Orion and Taurus, which also contains the beautiful Pleiades cluster, known as the seven sisters in Indigenous astronomy, as well as Sirius, the brightest star in the sky in the constellation of Canis Majoris.
"It is such a rich area of the sky," Dr Hill says.
