physics

# ggjc – gravitation group journal club

We had our inaugeral gravitation group journal club meeting this afternoon.  The article wasn’t too gravity centric, but after reading it we all had wondered approximately the same thing.  The article is “A blast wave from the 1843 eruption of $\eta$ Carinae”, by Nathan Smith.  It appears in the 11 September issue of Nature, and can be found under this link.

We wondered if this event had happened today, would LIGO have detected it?  We chose to attack the problem by finding the necessary energy put into gravitational waves.  We used a formula from “300 Years of Gravitation”, page 371:

$h_{c}\simeq2.7\times10^{-20}\left(\frac{\Delta E_{GW}}{M_{sun}c^{2}}\right)^{\frac{1}{2}}\left(\frac{1\,\mathrm{kHz}}{f_{c}}\right)^{\frac{1}{2}}\left(\frac{10\,\mathrm{MPc}}{r_{o}}\right)$

After making our assumptions and plugging and chugging (thanks Peter!), we came up with $\Delta E_{GW} \simeq 2\times10^{47}$, which is about 1% of the energy we can see in the motion of the Homunculus nebula (the object that resulted from the Great Outburst of 1843).  That didn’t sound too implausible, so we thought it bore further investigation.

A second question, which we had no way to answer, was “what effect does this event have othe population of supernovae”, since some events we would have classified as SN may be just energetic outbursts.  I thought we might see multiple SN happening on the same point in the sky, but the rate should be so low we wouldn’t see them yet.  I don’t know if this type of event is already incorporated in the SN observation models.