Meteors raining down in New Zealand are bright green. Here's why.
- Recent meteors spotted in New Zealand have shown a distinct green glow
- Perseid meteor showers also show a green trail
- There may be similarities between the two
The meteors streaking across New Zealand skies recently aren't ordinary falling stars — they're green. Jack Baggaley, professor emeritus of Physics and Astronomy at the University of Canterbury explained why in an article published in The Conversation.
Meteors are exciting and scary at the same time. The summer months in the northern hemisphere are a great time to witness these fireworks in the sky. In rare cases, a large meteor can light up the night sky and send an aftershock that shatters windows and sends the mind wondering what an even larger meteor would portend.
This thought must have surely run through many minds in New Zealand on July 7, when a sonic boom was heard across the two islands of the nation as a huge meteor exploded over the sea near the capital city of Wellington. For those who witnessed it or saw videos of the event, the bright green color stood out.
The Green of the Auroras
The easiest comparison of the green was that of the auroras, which are also visible in the southern hemisphere.
Une aurore australe sous la lumière de la lune ?https://t.co/r9y1t2MgPp— Thomas Pesquet (@Thom_astro) ) September 14, 2021
As Baggaley explains, the distinct green color of the aurora is due to the oxygen ions in the upper atmosphere created by the collision of oxygen molecules with charged particles coming from the Sun.
The ions soon return to their atomic state by recombining with the electrons, but in the brief period of several seconds where they are in an excited state, these ions radiate light at the wavelength of 557 nm. As it happens, the human eye sees that wavelength as green.
Can a meteor also shine green?
Yes, meteors can exhibit a green glow like the auroras. The trick is speed. A meteor can glow green if it's moving at tremendously fast speeds while passing through the thin outer atmosphere, roughly 62 miles (100 km) above the altitude at which the auroras form, Baggaley explains in the post.
As a matter of fact, the Perseid meteor shower — which has already begun and will peak on August 13 — is a prime example of a green meter. Bits of the comet Swift-Tuttle that remain in space from its journey almost a century ago, enter the Earth's atmosphere at speed of 37 miles (62 km) an hour and leave a similar green trail.
However, Baggaley goes on to state that this green is different from the aurora green. When asteroids containing nickel and iron hit the Earth's atmosphere, the rapidly released enormous amounts of heat end up vaporizing these metals which then radiate green light.
The meteor that hit Canterbury on July 22 actually turned a pale yellow over the night sky after winds from the upper atmosphere twisted its glowing tail. This was the effect of sodium atoms being excited in the presence of ozone.
If you would like to see some more green meteors don't forget to catch the Perseid shower this month. Since the peak night happens to be a full moon night, you may be better off spotting them this weekend itself.
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