A rather brilliant paper from my student Mitchell Dixon focussed on exploding stars, known as supernovae, and finding ways to make them more accurate distance measurement tools to map the expansion of the universe itself. In the end he found that nearby ‘calibrator’ supernovae had a systematic shift with the specific star formation rate (i.e. how rapidly the galaxy is doubling its mass in stars) and taking that into account he improved the accuracy of the expansion rate of the universe known as the Hubble Rate (or H0 of the title).
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How do you measure distances in space? There’s no tape measure to stretch between the stars of course, but instead there are a series of techniques that work over ever increasing distances with one technique handing over to the next - the first rung on that distance ladder is Parallax (I once tried to explain this live on national Breakfast TV!) and my student Mitchell Dixon has just published a definitive study on that technique as it maps to the next rung of a special class of stars known as Tip of the Red Giant Branch (TRGB) stars which have a known (or at least calibrated!) brightness that depends on how rapidly the brighten and fade.
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Our Universe is expanding, and indeed accelerating in that expansion, and primary means to that discovery last century was measuring the apparent brightness of exploding stars known as supernovae. A special kind of supernova explodes at (almost!) the same brightness, known as Type 1a, and hence if you measure that brightness you can figure out how far away they are relative to each other. My student Mitchell Dixon published an exhaustive analysis of how to better calibrate that brightness of the Type 1a supernovae, in particular showing that they depended on the dust in the galaxy (slightly dimming them, or else perhaps causing a slightly different explosion brightness).
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This work led by the ANU’s Dr Roland Crocker and an absolutely gigantic list of the best and brightest in astronomy - with my student Thomas Venville proudly holding his head high amongst such giants - explored all the evidence we had from Fermi and found that sadly the signal from these pulsars can reasonably explain this… there is a hint of more but at this stage, we must be conservative and presume that this is the case for other such signals in more distant galaxies too. The search for the dark matter signal continues!
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An amazing opportunity to see Prof Brian Cox speak in a sell-out MCEC plenary event during his Journey into Deep Space tour of Australia. He basically explained the beginning and ultimate end of the universe (Eternal Inflationary Cosmology explains both if you were curious) from first principles which is no mean feat.
Event better was getting backstage to hang out with him and Robin Ince (thoroughly lovely human being) and chat science. Definitely one of the coolest things I've done recently and it's given me some great ideas (i.e. that I'll steal) to use in my own talks!
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