Saturday, December 06, 2008
Echos of Anchient Light - Tycho Brahe's Supernova revelaed
This supernova was classified as a type Ia. However, there has been some doubt about this classification, as naturally enough astronomers were not able to directly measure the Supernovas spectrum. Now, over 400 years later, astronomers have been able to measure this spectrum from light echoes reflected from dust clouds and confirm it was a type Ia supernova.
Once the light of the supernova swept past earth back in 1572, it kept going. When it hit dust or gas, some of this light was reflected back to us. These (very) dim reflections are a sort of time machine that allow us to "watch" the supernova as it happened all those centuries ago and measure its spectrum.
Light echoes have been used before to identify supernova (see here and here for more detailed explanations and videos. But this is the first time such a historic supernova has been seen.
This research is reported in the current issue of Nature 2008,Volume 456 Number 7222 pp545-674, Tycho Brahe's 1572 supernova as a standard type?Ia as revealed by its light-echo spectrum p617
This study reports an optical spectrum of Tycho Brahe's supernova near maximum brightness, obtained from a scattered-light echo more than four centuries after the direct light of the explosion swept past Earth. It is found that SN 1572 belongs to the majority class of normal type Ia supernovae.
Oliver Krause et al. doi:10.1038/nature07608 (you will need a subscription to read this)