View Full Version : What's Up this Week: July 2 - July 8, 2007

2007-Jul-04, 05:04 AM
Monday, July 2 - Orbiting in space 40 years ago, the Vela 3 and 4 satellites were quietly keeping watch on Earth's nuclear test ban treaty. The Vela satellites were greatly successful and far exceeded their life expectancy. ...

Read the full blog entry (http://www.universetoday.com/2007/07/04/whats-up-this-week-july-2-july-8-2007/)

Don Alexander
2007-Jul-04, 12:04 PM
First of all, thanks for reminding everyone of GRB 670702, and happy 40th anniversary to you, GRB science!!!

But I must make some corrections to the text...

It's not correct to claim "very little is known about these mysteriuos events." At least the "very" can be struck, we've gotten to know quite a lot in the last ten years since the first afterglows were discovered.

While probably most GRBs do emit 100 MeV (million electron volts) photons, the typical energy scale is 100 keV, one thousandth of that mentioned.

While GRBs have assuredly occured in our Milky way, the last one might have been a long while ago. Although certain supernova remnants hint at very asymmetric explosions which might have involved GRBs.

The BATSE detector on the Compton Gamma Ray Observatory alone detected and localized (to a few degrees each) over 2700 GRBs. Swift is localizing roughly one per week to arcseconds today. So the number is much higher than 800.

While Wolf-Rayet Stars have been connected to GRBs, it's the supernova explosions of these stars that produce the GRBs, not the pre-explosion mass loss event (which is crucial for GRBs, though).

IC 4406, as actually stated in the text, is a planetary nebula and thus the remnant of a dying star of roughly solar mass. Thus, it has nothing to do with Wolf-Rayet stars or GRBs at all and is NOT a Wolf-Rayet nebula. Instead, observers should check out NGC 6888, the Crescent Nebula (RA = 20 12 07 Dec. = +38 21.3), which is a true Wolf-Rayet Nebula created by the massive stellar wind of this hot star.

And I really have no idea why "green sparkles" should have anything to do with gamma rays... It's probably oxygen emission, the forbidden [OIII] doublet.

Alex (the GRB Guy on Universe Today :D )

2007-Jul-04, 06:36 PM
A little typo :

Distance from Sun: It is 104.4 kly and not 104,4 LY (A thousand time more ! )