Eps Aurigae’s dark secret (interferometry rules!)

ResearchBlogging.orgSince a few weeks some PhD students and postdocs have been organising astro-ph coffee meetings three times a week, where the youngsters in the department can sit together and chat about recent papers. The advantage of having these meetings for only students and postdocs is that we can admit to our utter ignorance about stuff we should really know about – like gamma ray burst light curves or cosmic strings – without fearing the judgment of our supervisors. An additional benefit for me is that I now have a small army of minions scoping out interesting new research for me to blog about here. Ha!

Anyway, this morning we talked about a letter in Nature by Kloppenborg et al, published today, showing some fabulous new observations of the space oddity that is ε Aurigae. This star forms part of a binary system and is unusually  eclipsed by its invisible companion every 27 years for a lengthy 18-month period. Astronomers have known about this for almost 200 years, and had hoped that the current eclipse, which began last August, would finally provide some definitive answers. The AAVSO has even enlisted citizen scientists worldwide to gather data for the star’s light curve with its Citizen Sky project, and I spotted today that ε Aurigae also has a twitter feed.

The essence of the paper is shown in the above video. These images look like a clever simulation – but these are actually real images (well, apart from the white lines, obviously). They are resolved images of the stellar disk of  ε Aurigae! They were taken last November and December, in the early phases of the eclipse, and they clearly show that something dark is moving in front of the star. I’m an instrumentalist, I’m supposed to know this stuff, what we can and can’t observe, but I really didn’t.

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Stellar Citizen Science

Historical eclipse measurements of epsilon Aurigae

Historical eclipse measurements of epsilon Aurigae

Over at Professor Astronomy, Kurtis recently talked about an excellent citizen science project to light on the nature of mysterious variable star epsilon Aurigae. For almost 200 years, this run-of-the-mill star has been seen to dim periodically. This is not particularly remarkable in se – many stars dim at regular intervals, typically every few days, due to a companion star or planet passing in front of it. But in the case of epsilon Aurigae, the dip in its lightcurve occurs every 27 years and lasts several hundred days – around 2 years! The eclipse lightcurve (above) also shows that the dip contains quite a few bumps. So whatever movement is causing the eclipse is very very slow, and some interaction between the two bodies appears to be going on.  [Read more...]