1) The slashdot title, and a line in the New Scientist article are misleading. This does not cast doubt on SNe Ia as standard candles. It is an odd supernova, but we think we can screen these out -- we just have to be careful.
2) That email refers to observations in the B filter, which are used for cosmology. Indeed there is not enough data from that g filter (which transforms to B) near peak to constrain this supernova, so it was thrown out from the cosmology partially because the B peak magnitude is a complete extrapolation. For the Nature paper we used observations in the V filter, (transformed from the r filter) which is actually measured near peak. All of this is covered in the Nature paper. Also, when that email was written, not all of the data had been reduced. Be careful in taking emails out of context -- it is easy to get the wrong idea.
To answer a few people's questions (I'm an astronomer and I've done some research on Gamma Ray Bursts)
The system works because the satellites can time the arrival of bursts of gamma rays very accurately (minute fractions of a second, though it depends on the satellite). Since the gamma rays travel at the speed of light, they arrive at each satellite at a different times, and you can use this information to find the position of the burst in the sky. The timing info is stored and sent back to Earth, so it doesn't matter if there is a lag in sending the info back to Earth.
Since you can't see gamma rays, and each detector doesn't have spatial information, you can't create a picture, but you can create graphs of the gamma rays versus time. Plus, some of the bursts are also seen in visible light, as seen in the picture on the page.
It is true that this system has been around for a while, as it says in the article. But the IPN has become much more important recently with the loss of the Compton Gamma Ray Observatory, which reached the end of its mission and had to be crashed into the atmosphere. See: http://www.starstuff.org/default.asp?cover=/articl es/709.asp
CGRO used to produce nearly daily events, but now that it is gone, this interplanetary network will have to step up. Plus, with NEAR, there is a third satellite, making determination of a unique position possible.
You can see the IPN notices sent out to astronomers here: http://gcn.gsfc.nasa.gov/gcn/ipn/gcn_ipn.html
I'm an astronomer, and one area I do research in is the asymmetries of SNe. Actually, some supernovae appear to have asymmetries on the order of 30%. This is inferred from polarization measurements that we've done. One of these days I'll write up a story about it for starstuff.org (I am actually the co-creator of the site, though I didn't write this neutron star article), but for now you can see the gory details at: http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi bcode=1999astro.ph.12033W&db_key=PRE&hig h=3845e365b719527 You can also see signs of SN asymmetries in the fact that man SN remnants aren't round. We've even been able to watch the evolution of the layers blown off of the closest supernova in a long time, SN 1987A. Check out: http://oposite.stsci.edu/pubinfo/PR/97/03.html Hope this clears up that comment.
Slashdot Mirror
1) The slashdot title, and a line in the New Scientist article are misleading. This does not cast doubt on SNe Ia as standard candles. It is an odd supernova, but we think we can screen these out -- we just have to be careful.
2) That email refers to observations in the B filter, which are used for cosmology. Indeed there is not enough data from that g filter (which transforms to B) near peak to constrain this supernova, so it was thrown out from the cosmology partially because the B peak magnitude is a complete extrapolation. For the Nature paper we used observations in the V filter, (transformed from the r filter) which is actually measured near peak. All of this is covered in the Nature paper. Also, when that email was written, not all of the data had been reduced. Be careful in taking emails out of context -- it is easy to get the wrong idea.
To answer a few people's questions (I'm an astronomer and I've done some research on Gamma Ray Bursts)
l es/709.asp
The system works because the satellites can time the arrival of bursts of gamma rays very accurately (minute fractions of a second, though
it depends on the satellite). Since the gamma rays travel at the speed of light, they arrive at each satellite at a different times, and you can use this information to find the position of the burst in the sky. The timing info is stored and sent back to Earth, so it doesn't matter if there is a lag in sending the info back to Earth.
Since you can't see gamma rays, and each detector doesn't have spatial information, you can't create a picture, but you can create graphs of the gamma rays versus time. Plus, some of the bursts are also seen in visible light, as seen in the picture on the page.
It is true that this system has been around for a while, as it says in the article. But the IPN has become much more important recently with the loss of the Compton Gamma Ray Observatory, which reached the end of its mission and had to be crashed into the atmosphere. See: http://www.starstuff.org/default.asp?cover=/artic
CGRO used to produce nearly daily events, but
now that it is gone, this interplanetary network
will have to step up. Plus, with NEAR, there
is a third satellite, making determination of a unique position possible.
You can see the IPN notices sent out to astronomers here:
http://gcn.gsfc.nasa.gov/gcn/ipn/gcn_ipn.html
I'm an astronomer, and one area I do research in is the asymmetries of SNe. Actually, some supernovae appear to have asymmetries on the order of 30%. This is inferred from polarization measurements that we've done. One of these days I'll write up a story about it for starstuff.org (I am actually the co-creator of the site, though I didn't write this neutron star article), but for now you can see the gory details at: http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi bcode=1999astro.ph.12033W&db_key=PRE&hig h=3845e365b719527 You can also see signs of SN asymmetries in the fact that man SN remnants aren't round. We've even been able to watch the evolution of the layers blown off of the closest supernova in a long time, SN 1987A. Check out: http://oposite.stsci.edu/pubinfo/PR/97/03.html Hope this clears up that comment.