Looking ahead, the year of totality
Did you observe the palindromic date this weekend, 01- 02- 20 10 ?
If you have been observing the steady decline of the light of epsilon Aurigae this autumn, you might wonder if it too will be palindromic - that is, the brightness symmetricaly rising during egress early in 2011, as steadily as it declined during ingress autumn 2009. Short answer, probably not. Among the many wonderful conundrums surrounding epsilon Aurigae is that the eclipse is asymmetrical - egress tending to be fast than ingress.
This difference is thought to be due to asymmetries in the disk - somewhat less well defined on the trailing edge that we'll see later in 2010 and during early 2011 as eclipse ends, relative to the leading edge this past few months.
In the meantime, totality is close at hand, and should persist ALL YEAR. Visual and photometric indices today are closing in on the typical V ~ 3.75 base level that defines totality. Lately, green epsilon even looks fainter than red zeta, although their color difference can confuse an observer. However, this "flat bottomed eclipse" rarely is simply flat. Rather, variations of 0.1 mag or so on timescales like the out of eclipse variations are seen.
To the extent that interferometric imaging is possible during winter, we hope to gain some direct evidence about that, and the possibility of a central clearing. Other examples of astrophysical disk systems generally have a central hole, where starlight sweeps away the gas and dust. In young stars, this inner region can be a tangle of ionization and magnetic fields, perhaps inducing lighting discharges on a massive scale. Certain meteoritic rocks found on Earth show Calcium-Aluminum Inclusions (CAIs) suggestive of such flash heating during our own early solar system. Very rarely, photometry has shown flare-like changes in epsilon Aurigae... could it be giant lightning? We may have to wait for starships to get there someday in order to be certain, but it makes for an interesting connection with other disk systems.
It may be cold comfort as you stare up at epsilon Aurigae on these wintry nights to realize that the disk there is nearly twice as warm as your surroundings. The disk presents an exterior temperature of 550K, while Earth at freezing is only 273K.
As a postscript to the last blog, I want to thank Robin Leadbeater for pointing out that while Audubon and AAVSO have century-long traditions in citizen science, the British Amateur Astronomers (BAA) and their variable star records extend equally long and more. Here's to at least 3 of the longest running citizen science opportunities on Earth, and best wishes to you in 2010.