Magnetic Activity of Alpha Centauri
Published on Jan 18, 2007 at 1:45 pm.
4 Comments.
Filed under conference blogging, stars.
Over at Villanova University, Laurence DeWarf and Edward Guinan have been working on a program of studying stars like the Sun. They call this the “Sun in Time” project. The idea is to try to understand how stars like the Sun change as they age. Now, that is very important, because even the slightest change in the Sun can have a major effect here on Earth. During a period of time from the mid Seventeeth Century until early in the Eighteeth Century, the Sun went into a quiet period that we call the Maunder minimum in which sunspot activity dwindled away to almost zero. During this quiet period, the Sun apparently dropped in luminosity by 0.2%. That doesn’t sound like much, but it had the effect of changing the Earth’s climate. This period of time was called the Little Ice Age, and during this time there were crop failures, excessively harsh winters, and even occasional freezes recorded during the summertime in Europe. We also know that the Sun gradually got a bit more luminous during the course of the Twentieth Century, coinciding with temperature increases and some climate change. Nobody knows why this happens, or even how it happens. But, it clearly would seem to be of interest in understanding climate change on Earth. Furthermore, we know that the Sun will change enough that Earth will become uninhabitable far sooner than the Sun runs out of nuclear fuel and dies. Exactly when the critical time comes isn’t really known, either. So, this sets the stage for stellar astronomers to study stars like the Sun.
The nearest solar type star is also our nearest neighbor in space: Rigel Kentaurus, or as it is often called, Alpha Centauri (its Bayer designation). At only 4.3 lightyears distant, Alpha Centauri is only slightly larger and older than our own Sun. But, it is one the nearest matches to our own Sun that we see, and conveniently it is close enough to study better than many other stars. One curious thing that they have found is that a survey of solar type stars shows that the older they are, the slower they rotate, as you see in the accompanying graph from DeWarf’s web page at Villanova.
Well, last week at the AAS Meeting, one of their students, Jennifer Carton, had a poster presentation about a particularly deep dropoff in magnetic activity with Alpha Centauri. This is interesting, because the sunspot cycle is known to be driven by magnetic activity. Magnetic activity, by the way, is believed to be associated with the star’s rotation, so changes in rotation as suggested by the Sun in Time may also result in changes in magnetic activity. Space based observations of Alpha Centauri show a factor of 25 drop in X-ray emissions over the course of only a couple years. Changes in X-ray emissions from the Sun are associated with changes in magnetic activity. When the magnetic activity is high, you get more sunspots, and magnetic recombination results in massive releases of energy that produce solar flares. So, less X-rays could mean fewer flares, and that from less magnetic activity. They have also found a substantial drop in far ultraviolet emissions from Alpha Centauri over this same time period. All this indicates a period of magnetic inactivity. But what does that mean?
The very last sentence on the poster raises the possibility that Alpha Cenauri may be going into a period similar to the Sun’s Maunder Minimum. If so, then studies of this star may help us understand what to look for when the Sun does this again (and it will do it again). However, I think that it may be a bit premature to say that this star is entering an extended period of inactivity. The title of the poster suggested that this magnetic quiescent period was unprecedented. But, how do we know? We’ve only had the ability to measure such activity from space for a decade or two. The Sun’s magnetic cycle lasts an average of 22 years (two sunspot cycles). So, how do we really know what is normal for this star? Could it be that being slightly older, the sunspot cycles are in fact more extreme? At any rate, it is a very interesting finding, and it definitely bears a lot of followup work. Understanding the Sun is important to us here on Earth, because small changes on the Sun can have major impacts here. And understanding the Sun means understanding solar type stars. Overall, this was an interesting poster, and quite thought provoking. I can’t wait to read the actual paper, which would have far more detail than the poster.
Oh, and I might also mention that this student was an undergraduate student working on this project. I am getting pretty self conscious at these meetings seeing how much work undergraduates are doing now-a-days. Granted, I did a little research as an undergraduate, but the ones today seem to be doing a lot more than I did. It is pretty impressive.
-Astroprof
Malte on February 3, 2007 at 3:36 pm: 1
Manual trackback from popast.nu.
yummy on August 26, 2008 at 6:16 pm: 2
Yesterday i had a dream where we , the Earth, was invaded from ufos and other type of lives. And I remember that it happened when it was reported to happen a rain of meteorites or some unusual activity in Alpha Centauri (news reported meteorites but they were ufos coming to the Earth). It is just a dream but you have to know that I don’t read about this subjects or read science fiction or whatever.
I do believe that intelligent life exist, my grandfather saw one and many friends too, and a teacher saw it along with a group of students… so this is real but the question is… how sure we are that they are not going to hurt us when coming here ? In my dreams they tried and we know that if us, people of the Earth, would discover other beings we would take advantage of them.. so I wouldnt like them to come here or I wouldnt send other meins saying “we are here”… the NASA should be more careful
They must be more intelligent as they already found the way to come here , so we should have a low profile I guess
How long would it take to a ufo to come to the Earth using their technology ? I mean if their sun is not longer “living” if there is life they may like to come here I guess.
yummy on August 26, 2008 at 6:21 pm: 3
A kind of masive movement from Alpha centauri to the Eartn what kind of signal would produce so we would notice it ?
Jack on January 13, 2009 at 11:33 pm: 4
Decrease in magnetic activity… If one were to calculate the distance of this star compared to the speed of light and come up with a time of travel, would 12-21-2012 be a good arrival date here? Is Centaurus closer to the center of the galaxy? IF Sag A or B entered the SMB in galactic center, 26,000 years ago the explosion shock wave (aka gravity waves?) would reach Earth in 26,000 years. IF… compared to a Coronal Mass Ejection, would an initial blast have effected Earth 26,000 years ago?
Thoughts?