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Solar minimum

Part of the point of the Lowell blog is to make some research topics and results available and accessible to all our readers, so here goes. I and my colleagues study the activity of the Sun and Sun-like stars, to better understand how our star varies relative to its closest cousins and to contribute, from an astronomical perspective, to our understanding of the effects of solar variability on terrestrial climate. I will try to keep the blog up to date with the latest in various parts of the field, as well as provide some general information posts.

To start with the basics, we are presently pretty near dead minimum of the solar activity cycle, the periodic rise and fall in the level of sunspots, flares, prominences, and other manifestations of the Sun’s varying magnetic field.

Here’s a full-disk image of the Sun taken today by the Solar and Heliospheric Observatory (SOHO), a satellite orbiting about a million miles from Earth, dedicated entirely to observations of the Sun. This image isn’t exactly thrilling; the Sun looks like a cue ball. This is because we’re right at the end of solar cycle 23, and few or no sunspots are visible on any given day. (Solar cycles are numbered consecutively; #1 was a fairly miscellaneous cycle in the 1750s.) We are expecting Cycle 24 to begin in early 2008. There are divergent predictions of the strength of the cycle, we but expect it will peak around early 2012.

We are interested in solar activity because as the cycle waxes and wanes, the overall brightness of the Sun rises and falls slightly, and it is then natural to wonder if the varying solar brightness impacts Earth’s climate. Well, to cut to the chase: it does. Key questions are by how much and how has the Sun varied historically, before instruments existed to take precision measurements of it?

This is the thrust of our ground-based observations from Lowell — to compare the Sun to the most Sun-like stars we can find, and see if solar variations are typical of stars in general. Pretty interesting stuff, and I’ll write some posts with some of the recent results soon.

If you’d like to keep track of “the Sun today,” you can find regularly updated images like the one above at SOHO’s Web site. From that page, click “The Sun Now” and you’ll see the latest image of the solar disk. Over the next few years, the view should get progressively more interesting.