The 60th Carnival of Space is now up at Slacker Astronomy, and if you want to see some fine science writing, I’ll point you this week to the host, whose essay on Regulus shows what can be done when a scientist with serious writing skills takes apart an interesting scientific paper. Doug Welch knows what he’s talking about — he’s a professor of physics and astronomy at McMaster University (Hamilton, ONT), deeply involved in dark matter studies, supernovae and variable stars. So it’s no surprise that the interesting story of Regulus and its apparent companion comes alive in Slacker Astronomy‘s pages.
What about Regulus? A team led by Doug Gies (Georgia State) has studied this bright, ecliptic-hugging star for evidence of a hitherto unknown companion. The result:
They found that Regulus was indeed a spectroscopic binary. Once every 40.11 days, the system completes one orbit. Regulus itself has a mass of about 3.4 times that of the Sun. The companion of Regulus is much less massive – only about 0.30 solar masses. Such a small mass object is either a low-mass star or a white dwarf. The latter possibility provides an explanation for Regulus’ rapid rotation! The idea is that the companion was once the more massive member of the pair and when it finished hydrogen burning in its core, it expanded dramatically and started losing mass to Regulus in a manner which “spun it up”. A mass of 0.30 solar masses is very low for a white dwarf – such objects are found only in systems where it is clear that much mass has been transferred.
Intriguingly, spectra taken by the International Ultraviolet Explorer satellite showed results consistent with a white dwarf but not a cool, low-mass star. The case for a white dwarf seems confirmed, a reminder that objects we thought we knew well often yield up their secrets only slowly, and with the necessary improvements in our instrumentation. And if you have a fascination, as I do, with how these studies work, be sure to read Welch’s comments on the instruments involved, including the Kitt Peak National Observatory Coude Feed Telescope, about which this:
A Coude room is very high-resolution spectrograph capable of tearing the light from a telescope into very fine shreds of color. It was designed to be fed by the 2.1m telescope at Kitt Peak. However, observatories tend to do deep imaging around the time of New Moon (i.e. when the sky is dark) and the 2.1m served a variety of such needs. It was realized that the a smaller telescope could “feed” the spectrograph during these periods and that brighter stars could be observed with that smaller telescope plus Coude spectrograph while the big telescope was busy imaging!
This is solid science writing. Taking state of the art instrumentation and breaking it down into not just comprehensible but readable terms is hard work, and Welch does the same with GSU’s Multi-Telescope Telescope. Slacker Astronomy quickly goes into my essential RSS list. I also want to point you to a site already firmly ensconced in that list, Brian Wang’s NextBigFuture, which (among many other things) this week discussed the Space Elevator power beaming competition. Finding the cheapest route to low-Earth orbit is an essential for making a true space-based infrastructure a reality, and few concepts are as visionary as the Space Elevator. Add commercial competition to the mix and watch the ideas fly.