Will we get another chance to see aurora?
The weekend’s glorious heavenly show was the best in a century, according to some observers, but the sun has turned its dazzling burst of particles in a new direction.
The aurora in the night sky could be seen across many parts of New Zealand on Saturday, but for many Wellingtonians, the glow was less than spectacular to the naked eye, due to light pollution.
Stargazers Sam Leske and Hari Mogosanu had the perfect spot at their observatory on the top of a South Wairarapa hill, and they were surprised by the depth of colour on display.
The astronomical educators ran night sky viewing evenings from their Star Safari observatory, just north of Martinborough.
Leske, who is an astrophysicist, said we were unlikely to see anything like Saturday’s aurora over the next few days because the active region of the sun, which expelled the charged particles, was rotating away from facing this part of the solar system.
“To crank up again, there would have to be another good flare-up on the sun. You never know, we might be lucky.”
Leske said a pair of sun spots could create a large magnetic field loop arcing out from the surface of the sun and this could get twisted and break, releasing charged particles called coronal mass ejection, which took a couple of days to reach Earth.
When these hit our planet’s magnetic field, they could interact with the molecules in the atmosphere, emitting a coloured glow like they did on Saturday night. The red hue which many saw was the result of photons and electrons exciting oxygen molecules, and greens were caused by nitrogen.
“When you get a really big one, which is what happened recently ... more stuff hits the magnetic field, so rather than gently making its way towards the poles, it takes a more direct route. That can bring it down at these mid latitudes.”
He said it had been around a century since an aurora had produced such an effect here. “We think it was about 1921.”
Star Safari was due to host a group on Saturday night, but Leske and Mogosanu went up to their observatory early to get some photos of a comet and a supernova.
They were lucky to see the aurora before the sky clouded over. “We were not expecting to have such an amazing show.”
Mogosanu, an astrobiologist, said some places in Wellington were affected by light pollution, making it difficult to see the aurora with the naked eye unless a person was at the south coast or other dark spots.