"Glowing ball" seen in NZ skies 02/04/12

A rocket ?
Didn't I read some where in the last couple of days that North Korea had had
missals pointed at Australia.
Maybe they fired some and they went hey-wire. Ya never know what N.K. might do.

reply to post by grindhouzer

Originally posted by grindhouzer
reply to post by usmc0311

 

Definatly no rockets down here in New Zealand, weve got rocket rentals tho

We may not have many rockets, but we do have some
I personally know a guy who's going to go for the world record for the rocket class he's launching this weekend. Then there are also these guys.


reply to post by FireballStorm

After seeing that footage, I think it is highly likely that it was in fact a meteor that was seen. I definitely don't think it was a contrail, due to the velocity that the object was travelling at. Of course, this was hard to determine before there was video footage of the object.

I've seen quite a few meteors, but never seen them leave a trail. But I think the reason for this is that I've only ever seen them at night when they would not be illuminated by the sun. Also, a trail left during the day would probably not be clearly visible against a bright blue sky. But as this event occurred around dusk, it's trail was illuminated by the setting sun, in a relatively dark sky making it clearly visible.

It is possible that it was something else, but I think a meteor is the most likely explanation.

Originally posted by Curious and Concerned
I've seen quite a few meteors, but never seen them leave a trail.

Keep observing and you will see them. Fast and/or bright meteors usually leave trails/trains.

I've observed many thousands of meteors, and seen 100's of trains/trails, though none quite like the trail the NZ fireball left.

Originally posted by Curious and Concerned
But I think the reason for this is that I've only ever seen them at night when they would not be illuminated by the sun.

It's true, you are unlikely to see a trail like the one the NZ fireball left, because you would have to be lucky enough to catch a bright fireball during or just a bit after sunset. You are right that the trail is illuminated by the sun, in this case.

Having said that, you can see trains that are just as impressive (more so in some respects IMO) deep in the night, since some types of train are self-luminous.

Here's a short animation of a Quadrantid meteor and it's persistent train, taken by Mike Hankey last year.



There are actually a few different types of meteor train/trail/wake - check this link for the definitions.

Originally posted by Curious and Concerned
Also, a trail left during the day would probably not be clearly visible against a bright blue sky. But as this event occurred around dusk, it's trail was illuminated by the setting sun, in a relatively dark sky making it clearly visible.

Absolutely spot on observation there. I could not agree more.

I would imagine anything burning and flying would leave some sort of trail? I dunno seems sort of self evident no?

I have only seen this type of thing at night. I can say that it is very hard to tell distance, speed and size in the heat of the moment.

I'm not at all surprised that there is so much confusion and varied reports.

Originally posted by pseudotro
I would imagine anything burning and flying would leave some sort of trail? I dunno seems sort of self evident no?

Yes, that is true, but it's a rather simplistic view, and there are other factors to consider.

For starters, the vast majority of atmosphere has too little oxygen to support combustion. Even at relatively low altitude (compared to that at which meteors are visible) it's impossible to get things to burn, unless they already have an oxidizing agent included as a source of oxygen - At the height of Everest (5 km above sea level approx), the oxygen is already too thin.

Instead of burning, there is a rather different process at work, that is known as "ablation". Ablation is due to the velocity of the meteoroid, which slams into atmospheric gas molecules, heating the meteoroid, and stripping away parts of it.

The result is a self luminous plasma, which is responsible for the majority of light produced by a meteor, and also for the train or wake. Note that this is a different kind of train to the dust-trail which has to be sun-lit to be visible (refer back to the link in my previous post regarding types of train/trail/wake).

Here is a paper with some info on current theories
Mass Loss Due to Sputtering and Thermal
Processes in Meteoroid Ablation

The point is that, depending on. the objects speed (ablation ceases once an object slows down to around 3-4 km/s), and also the conditions under which the meteor is seen (eg at dusk/dawn, when the upper layers of our atmosphere are still lit by sunlight), different kinds of trail may or may not be visible.

Let's not forget that the material that the object is made of will also be a factor. For example, the heat--resistant tiles on the space shuttle, are able to resist ablation, but there will always be a wake or trail of ionized atmospheric gas produced at speeds above the "retardation point" (3-4 km/s), although weather or not this is visible depends on the conditions.

In the case of the NZ fireball, we are only seeing the "dust train" because it is lit by the sun. Had the event occurred a long time after sunset, when the sun was well below the horizon, the train seen in the footage would probably not be visible, although the plasma train would be more visible thanks to a darker sky, but they usually don't last as long as dust trains.

Originally posted by pseudotro
I have only seen this type of thing at night. I can say that it is very hard to tell distance, speed and size in the heat of the moment.

Absolutely. If you look at reports of previous fireballs, it's common for people to seriously under or over estimate all of the aspects you mentioned, and more. I looked at just one example in this thread, but many other examples can be found if you have the time to search through fireball reports.

That said, we do know quite a bit about these vital statistics thanks to both photographs and video footage taken over the previous 150 years (approx). It should be possible to glean a surprising amount of information from photographs and footage of the event, especially if photographed from geographic locations separated by at least a few tens of km, rough orbits and ground paths/entry angle can usually be worked out.

Originally posted by pseudotro
I'm not at all surprised that there is so much confusion and varied reports.

I guess it goes with the territory. The vast majority of people have never seen a fireball, let alone a bright fireball like the NZ fireball. Most people have seen a "shooting star" (or "meteor") or two before, but comparing meteors to bright fireballs is like comparing apples to oranges. It does not help that there are many public misconceptions and little or no education on the subject.

Add to that, these things are literally a "bolt out of the blue", and you are bound to have a bunch of shocked/and or confused people.