Review: supernovae, white dwarves & the accelerating Universe

Astronomy Twitter Journal Club tackled supernova progenitors for its 10th meeting, inspired by this year’s Nobel Physics Prize, which was awarded to Saul Perlmutter, Brian Schmidt and Adam Riess. Congratulations!

There’s some background to the topic in our preview post and you can also read the full tweet transcript of the meeting.

The discussion was chaired by Matt Burleigh and he set the tone of the meeting straightaway:

Convince me there’s nowt wrong with SN Ia as standard candles…

The issue

@Matt_Burleigh so, what don’t you like about using 1a’s to measure the expansion of the universe? – @kashfarooq

@kashfarooq If we don’t know the progenitor, then can we be certain they are standard candles? What corroborating evidence is there? So I would ask cosmologists, is acceleration of universe firmly established, is Nobel prize premature or deserved? – @Matt_Burleigh

Can we find one locally?

There’s still a SN 1a in the nearby galaxy M101. Have they searched for progenitors there? – @AdrianusV

yes, I believe so, and see nothing. Which fits with some kind of WD binary (not supermassive star) – @Matt_Burleigh

Are they good standard candles?

what if SNIa evolve with redshift, mimicking acceleration signal? They are standard candles, assumed to have same luminosity. What if brighter in past? – @Matt_Burleigh

Observations show that SNe Ia have the same absolute magnitude after applying some corrections to the data

presumably achieved by measuring the distance to those galaxies by another method… circular argument? – @Matt_Burleigh

The hunt for a progenitor

Chandra data seems to suggest that WD (white dwarf) accretion SN not as common as expected. – @kashfarooq

yep. And searches for double WDs find none with right masses and periods to merge in a Hubble time. Its worrying. If you take the frequency of SNIa in other galaxies, then we should have found a progenitor by now…. – @Matt_Burleigh

This article describes progenitor of SN 2007IF, a WD heavier than 1,4 solar mass:

@AdrianusV yerrrrrsssssss…. #speculative – @Matt_Burleigh

Other evidence for acceleration

has the accelerating expansion of the Universe got any other evidence? or is it just type 1a? @kashfarooq

GRBs and some evidence for MWB (microwave background). But I assume neither as good as SNIa since new dark energy experiments will use SNIa – @Matt_Burleigh

In conclusion

@Matt_Burleigh so you are not convinced, then? – @kashfarooq

@kashfarooq convinced of what? SNI as standard candles? Not yet but I don’t dispute other evidence also points to accelerating univ – @Matt_Burleigh

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