[LINK] On the hoped-for discovery of planets at Alpha Centauri

[rfmcdonald]

I want Tirane. Astronomers, Centauri Dreams reports, might be able to give me that, or at least details about the Alpha Centauri system, soon thanks to a new search effort.

John Hearnshaw (University of Canterbury, Christchurch) reports in a recent post on Cosmic Diary that the university’s Mt. John Observatory has begun a program to search for Earth-mass planets around Centauri A and B. Although the observatory is heavily invested in microlensing technologies (working with the Microlensing Observations in Astrophysics collaboration), the new efforts will put radial velocity methods to work using the Hercules spectrograph.

The program is a joint effort with Stuart Barnes at the Anglo-Australian Observatory and Mike Endl at the University of Texas (Austin). And as Hearnshaw notes, the problem is a formidable one, given that an Earth-mass planet in the habitable zone around Centauri A creates a ‘wobble’ of only 10 cm/s (slightly larger for the less massive Centauri B). Yet the observatory is banking on Hearnshaw’s statement that 30,000 spectra of Centauri A or B over three years can detect a habitable zone ‘Earth.’

The habitable zone around Centauri A should be found at about 1.2 AU, while 0.75 AU is calculated for Centauri B. What else do we know about the primary Centauri stars? Earlier work has demonstrated that no gas giants as massive as Jupiter can exist there — Doppler studies would have found them by now. But the case for Earth-mass planets remains open.

In a follow-up post, astronomer Debra Fischer states that they're particualrly hopeful about finding planets around star B, an orange dwarf dimmer than the more Sun-like A.

We know that Alpha Centauri “A” has a dominant pulsation period that’s about 5 minutes, just like the sun. I’m not really worried about periodic variations of minutes. We’ll be able to average right over that kind of noise. But no one knows whether or not there are long period variations in “A” or “B”. We do know that “A” is probably not as stable as “B”. People have measured pulsation periods in “A”, and in general we find that more massive stars have more active atmospheres. So yeah, I agree that “B” is a better bet. And if you told me that I could only observe one star, I’d choose B. But we’re studying both stars. And it turns out that this strategy of looking at both stars is pretty critical in ensuring a solid set of data.