Friday Morning Quiz

OK … somewhere in the observable Universe, what happens

(a) five times a second

(b) three times a day

.. and why is this comparison interesting ?

20 Responses to Friday Morning Quiz

1. Stuart says:

Andy, by ‘day’ are you referring to an Earth day or the rotation of some body about its own axis?

2. Davin says:

To clarify, does it happen five times a second for some time, with that event occurring three times a day?

3. andyxl says:

Query-1 : “Day’ means an Earth day. Query-2 : a new event starts five times a second on average. Each event lasts much longer. Perhaps I should also clarify that I am talking about two types of event, not one type of event that somehow happens both five times a second and three times a day… So there are two answers .. but somehow connected…

4. MikeW says:

my guess: gamma-ray bursts – (a) total cosmic rate; (b) detected at earth by current instrumentation

5. andyxl says:

(b) is correct and (a) is wrong …

6. MikeW says:

actually my friends tell me this is entirely wrong but I don’t know how to retract previous comment!

7. MikeW says:

I think (b) is right if I had said detectable (rather than detected)

Maybe (a) is connected with last week’s obsession with neutrinos?

8. MikeW says:

sorry to hog the blog, how about SNe for (a)?

9. Tony says:

Knowing sweet f.a about astronomy I won’t attempt an answer but I would guess from what Andy says that if something happens, in the _observable_ universe ‘five times a second’ but is only detected on Earth ‘three times a day’ then it is probably something that is either directional, so all the other events are not pointing in our direction, or which is almost always obscured by something else.

10. Tony says:

Directional idea might indicate pulsars but I don’t suppose three new ones are detected every day. Nah, I’ll leave it to the astros and get back to programming đź™‚

11. andyxl says:

OK : Mike W you are correct, and you win this week’s big no-prize. But Tony also gets a big no-prize, as directionality and obscuration are both reasons for the difference. So first, the number of SNe I took from the Woosley and Bloom Annual Reviews paper about the GRB-supernova connection. Everybody assumes that GRBs are supernovae now. The GRB is made in a relativistic jet, which is way brighter when pointed at us. But even when you correct for this (about a factor 300) that means only 0.2% of supernovae make a GRB. Somewhere deep inside, every supernova must make lots of gamma rays, but normally they don’t get out. So some special ones make a jet. What makes them special ? Nothing original here folks, just repeating what I learned in my recent reading (i.e. the Woosley and Bloom paper) which I found ticklingly interesting.

And it is slightly connected to last week’s obsession, as in fact most of the power of supernovae must emerge in neutrinos. And gravitational waves, but lets not encourage STFC to spend ALL their money on gravtitational waves….

12. Tony says:

So, one in 500 SNes produce a relativistic jet, one in 300 of those in our direction and (I think I read) there should be a SNe in our galaxy every 30 years. Does this mean that roughly every 5 million years the Earth will get hit by one of these relativistic jets from within our own galaxy?

13. Tony says:

No, needs to be further corrected by our being out at the edge of the galaxy.

14. martinselvis says:

i’ve managed to not post anything here for a whole day! [did some actual work instead. odd, I know.] But now I’m having a nice cup of tea, which stimulated enough thought to ask Andy: so what’s the diffuse neutrino background from all this SNae then? c.f. something. (Sun?)

15. andyxl says:

Jeez I don’t Martin. That would require some actual work. I am sure somebody knows already.

16. KOMbat17 says:

Martin’s post reminds me that I nearly answered: a) Merrifield, Elvis, Carter read blog; b) I read blog.

17. Keith A. says:

Apparently the neutrino background is a potential diagnostic of early star formation…