The best way to see this year’s best meteor shower

Stargazers rejoice, the Geminid meteor shower reaches its peak later this week, and this year’s sky show is particularly spectacular.

Have you ever seen a shooting star?

If not, the next couple of nights will be the perfect introduction, with the peak of the year’s best meteor shower — the Geminids — forecast to occur on the evening of 14 December into the morning of 15 December.

While the Geminids are a reliable annual spectacle, this year is the ideal opportunity to head out and observe them.

For one, when the Geminids reach their peak, the Moon will be new, meaning it will be below the horizon all night and the sky will be properly dark — perfect conditions for meteor watching.

Even better, the peak of the shower this year occurs just at the time the Geminids are highest in the sky from Earth’s eastern longitudes, meaning that viewers have a perfect ringside seat for the best display of natural fireworks this year.

To get the best view, aim to head out in the very early hours of Friday 15 December, and spend some time relaxing, gazing up at the sky, ideally somewhere with dark skies, away from bright city lights.

See what the view will be like near where you live, and the best time to go observing, in the interactive below.

Meteors can be seen in any part of the night sky, but if you trace the direction of their motion, they will always point back to that single point in the night sky — known as the meteor shower’s ‘radiant’.

Meteor showers are named for the constellation in which that radiant is found, so the Geminids radiate from a point in the constellation Gemini.

The good news is that the farther north you are, the higher in the sky the Geminid radiant will get over the course of the night and so the better view you will have.

From a latitude perspective, about 30 degrees north of the equator — so near cities like Delhi, Osaka and Tokyo — will give you the perfect view, as in the morning hours the Geminids will appear to be radiating from a point in the sky directly above you.

Astronomers quantify the strength of a meteor shower by calculating its ‘zenithal hourly rate’.

This is the theoretical number of meteors you would see in one hour if the radiant of the meteor shower is perfectly overhead, you are at a perfectly dark site with no light pollution or cloud cover and you have perfect eyesight.

The actual number of meteors you will see will always be lower.

The lower the position of the radiant in the sky, the fewer meteors you will see. If there is a lot of light pollution, the fainter meteors will be hidden from your view, and so the rate you see will also go down.

At their peak, the Geminids have a zenithal hourly rate of around 150. So under perfect conditions, with the radiant directly overhead, you might expect to see two or three meteors per minute.

It’s important to note, though, that meteors are like buses — you can wait five minutes and see nothing, and then three will come along at once.

In the interactive above, there’s a more realistic hourly rate of how many meteors you could expect to see at your location as the Geminids move through the night sky.

But if you’re watching from somewhere with light-polluted skies, or if the sky is partially covered by clouds, expect this rate to be lower.

What makes the Geminid meteor shower so special?

The Geminids are the most active of all the meteor showers the Earth encounters through the course of a year.

Every December, our planet ploughs through the debris left behind by an asteroid called 3200 Phaethon — a potato-shaped lump of rock and metal around 5km in diameter, often described as a ‘rock comet’.

Phaethon moves around the Sun on an extremely elongated orbit.

At its farthest from our star, it is well beyond the orbit of Mars, where Phaethon’s surface temperature likely falls below -100 degrees Celsius.

At its nearest to the Sun, Phaethon is much closer than the orbit of Mercury, superheating its surface to temperatures in excess of 700 degrees Celsius.

These temperature extremes are enough to crack and shatter its surface rocks, as they expand and contract repeatedly.

As a result, Phaethon is continuously shedding dust — particularly when it is closest to the Sun.

Over hundreds of years, that dust has accumulated, spreading around Phaethon’s orbit to create a vast, dusty tube in space.

Every December, Earth runs right through this tube — and we get to enjoy the Geminid meteor shower.

The grains of dust from Phaethon hit our planet at tremendous speed — around 34 km per second.

Those dust grains carry an incredible amount of energy. As they push deeper into Earth’s atmosphere, they superheat the air around them — creating a spectacular flash of light in the sky, or shooting star — with the resulting radiation totally vaporising the dust grain, a process known as ‘ablation’.

A typical meteor, as bright as the brightest stars, might be no more than a millimetre or two in diameter.

Earth first enters the debris left behind by Phaethon around 19 November and doesn’t leave again until 24 December.

But for most of that time, Earth is passing through the outskirts of Phaethon’s debris, and there are very few Geminid meteors streaking across our skies.

It’s when Earth reaches the centre of Phaethon’s debris stream on 14 and 15 December — where the dust is densest — that the number of visible meteors rises to a strong peak.

So the best time to view the shower will be the evening of 14 December into the morning of 15 December, with the nights before and after also offering a good display of celestial fireworks.

Tips for observing a meteor shower

When observing meteor showers, comfort is probably more important than anything else.

Plan to head out somewhere dark — the darker the better. The farther you travel from bright city lights, the darker the sky you will have, and the better the display you will see.

Aim to get to your viewing location in daylight or check it out on a previous day, to plan the best place to get comfortable — and remember to check beforehand for any hazards.

Once you’re at your chosen location, your best bet for a good view is to lie down — get comfortable, as you’ll want to spend at least half an hour, and preferably longer, gazing up at the sky.

Take a blanket and pillows, and make sure to bring something warm to wrap up in, even if the night doesn’t feel cold. It’s amazing how chilly it can get when you’re lying still outside in the dark.

Figure out where in the sky the radiant of the meteor shower will be. For the Geminids, you’re looking for the constellation Gemini — which is above and to the left of Orion (for those in the northern hemisphere), or below and to the right of Orion (if you’re in the southern hemisphere).

Once you’ve located the radiant, have a look around the sky in that general direction. Do you have darker skies to the radiant’s left, or to its right? Pick the darker side and point yourself that way.

From long years of experience, I have found the best view of a meteor shower is from looking about 45 degrees to the left or right of the radiant, and with your head tilted up so that you’re looking about 45 degrees above the horizon.

While you can see meteors from a meteor shower in any part of the sky so long as the radiant is above the horizon, this approach seems to give the best chance of seeing a really good display.

It will take between 30 and 45 minutes for your eyes to become fully adjusted to the darkness, allowing you to see the faintest possible stars. Any source of light seen in that time will reset the clock, so make sure to put your phone away.

Now relax, look to the skies and enjoy the view.

Professor Jonti Horner is an astronomer and astrobiologist based at the University of Southern Queensland, in Toowoomba. He has a particular interest in the Solar System, and especially the comets, asteroids and meteors therein. In recent years, his research focus has expanded to include the search for, and study of, exoplanets.

Originally published under Creative Commons by 360info™.