Gamma-ray Blast from Billions of Lt-Yrs Away: Timing q.?

Factual Questions
1

Okay, I’m sorry for being ignorant, science-wise. But I just read this article about a massive gamma-ray blast in a constellation 12 billion light-years away, and I’m confused. I’ve bolded the stuff I find odd:

First of all: this is very very cool. That out of the way, I don’t get it: if the burst occured in September in a location that’s 12.2 billion light years away, how the heck could we have observed it already? Unless this explosion goes faster-than-light, this seems impossible. Or are they trying to say that they observed it in September, and this blast actually occured 12.2 billion years ago?

Is this just a poorly worded article, or is my understanding flawed? (Rest assured, I know the latter is the likelier of the two possibilities!)

2

Sounds like they mean they observed the event in September. It can hardly mean anything else; gamma rays do not travel at supralight speeds.

Unless, of course, the gamma rays were from the explosion of Praxis half a galaxy away, and then you just say “put it on screen!” and your Star Trek staff obliges.

3

Yes. The explosion was observed to occur last September, but actually happened about 12.2 billion years ago. It’s a common error in astronomy writeups. Journalists don’t seem to like what adding that particular bit of accuracy does to the impact of their sentences.

4

That would explain the recent increase in incidents of “hulkism” reported since September.

5

Heh. Well played, msmith537.

Thanks, guys. I’m a little relieved to know I’m at least able to comprehend a mistake like this when I see it. Thank you, Carl Sagan!

It seems odd that they wouldn’t add “observed,” since I think it makes this even more awesome – the fact that we’re just seeing something now that occured 12.2 billion years ago ! I mean, astronomy’s almost a sort of time machine, isn’t it? (Or a VCR, anyway.)

6

Except that everything we see occurred in the past. The light we see from the sun was emitted eight minutes in our past. The light you see in the photons on your screen reading this left the screen nanoseconds in the past. Nothing is ever happening in the actual now.

Astronomy just amps these numbers up so that they seem more impressive, but its same phenomena we encounter every single second of our lives.

7

I find those reports incredible.

8

Way to harsh my buzz, dude. :slight_smile: Seriously, I know that, but eight minutes, even eight years, don’t hit the point home as much as 12.2 billion years do. At least not for me.

9

A gem! New to me, that phrase goes straight into my riposte repository. :slight_smile:

10

I’m with you. I find it a lot more impressive to be able to watch something that happened long before there even was a planet Earth than to see something that occured just before the last commercial break on TV.

11

New? That phrase (or the similar “harsh my mellow”) is about 12.2 billion years old. :smiley: