Star Flips its Magnetic Field

At some point in the last year or so, the Sun-like star tau Bootis completely flipped its magnetic field. The star’s north pole became its south pole, and vice versa. It this going to happen to our own Sun? Yes! Don’t panic though; in fact, it happens every 11 years or so.

Even thought the Sun’s magnetic field flip has been well observed, astronomers have never seen this happen on another star. With the Sun, the field reversals are closely linked to varying number of sunspots on its surface. The magnetic field flip happened last time in 2007, when the Sun was at the “solar minimum”.

The Earth has been recorded to change its magnetic field too, but this event has happened very erratically in the past, and theres no way to predict when it’s going to happen again in the future.

And international team of astronomers were watching the star tau Bootis with the Canada-France-Hawaii Telescope Mauna Kea as part of a survey measuring the magnetic field of stars. On one sweep the star had one configuration, and later on, the magnetic field was reversed.

Since this event happened within just two years of observations, it’s likely that tau Bootis flips its field even more quickly than the Sun’s own 11-year cycle. Even more interesting is the recent discovery that the star is orbited by a massive planet. It’s a hot Jupiter planet, six times the size of Jupiter, but only 1/20th the distance from the Earth to the Sun.

The planet is so close, it has become tidally locked with the star, similar to the way the Moon only shows one face to the Earth. It’s possible that the tidal interactions between the star and the planet somehow speed up the surface of tau Bootis, and encourage these magnetic flips.

The astronomers are planning to keep their telescopes firmly targeted at tau Bootis, checking the magnetic field of the star regularly. If it flips again, they’ll be ready.

The research was published this week in the British journal Monthly Notices of the Royal Astronomical Society.

Original Source: Institute for Astronomy News Release

19 Replies to “Star Flips its Magnetic Field”

  1. What are the practical consequenses of this on earth when our sun flips fields or when earth flips it’s field?

  2. Fraser, I’m pretty sure the suns magnetic field doesn’t flip every 11 years. Thats just the sunspot cycle. The magnetic field has flipped many times in the past but definitely not every 11 years.

  3. Timber Says:
    February 12th, 2008 at 6:23 pm

    What are the practical consequences of this on earth when our sun flips fields or when earth flips it’s field?

    Timber – The consequences of the Sun’s actual magnetic field flipping are essentially non-existent for us – the Sun’s magnetic field, as the article states, flips every 11 years in a very predictable fashion. Hence, you have likely been alive through a number of these events without any problems. The solar cycle with which the flipping is associated does have some consequences for Earth though.

    The ‘solar cycle’ refers to the gradual winding up of the magnetic field on the Sun, due to what scientists call ‘differential rotation’ of the Sun. Essentially this means that the equator of the sun rotates faster than the regions near the poles, and the magnetic field essentially gets dragged along with it and ‘wound up’. When it reaches a certain point, the magnetic field starts to ‘break’ and reconnect into a simpler and ‘less stretched’ arrangement. This process leads to solar flares and Coronal Mass Ejections which can, among other things, knock out satellites and power grids on Earth. We are not directly in any danger though, precisely because Earth’s magnetic field protects us from charged particle radiation that the Sun emits.

    Which brings us to your second question. The evidence strongly suggests that Earth’s magnetic field has flipped a large number of times in the past, likely due to some sort of precession effect in the dynamo action of the liquid iron core of the planet. If (indeed, when) the Earth’s field flips again, we could be in trouble. This is due to the fact that, it is thought, for a while when the Earth’s field flips it tends to weaken into almost non-existence first. Accordingly, our protective radiation shield will be gone for a period, the consequences of which are no entirely predictable. Certainly, life has survived through many such events before (they tend to happen on the order of every half-million years or so), but what the consequences would be for a technologically advanced society are uncertain. Since we haven’t had one for about 800,000 years, and they tend to occur on average about every 250,000 years, you could say we are well overdue for one. However, the evidence tends to suggest that the reversal periods are irregular, so nobody really knows what is going to happen next.

  4. Thank You Astrofiend, I appreciate the response.

    I’m assuming (recognizing that assumptions are always risky) these changes in earths magnetic field are somewhat progressive, rather than instantaneous, so we won’t be too surprised when we are faced with whatever the problems will be.

    Clear skies

  5. Please don’t show this article (especially the flipping of Earth’s magnetic field) to the Dec. 21st 2012 Mayan “Doomsday” crowd. It would just give them more grist for their non-existant mill.

  6. About 200 million years ago, we stood up. It wasn’t until about 700,000 years ago we had the brains to ‘harness’ fire.

    The last Earth-flip is guessed at about 800,000 years ago. On a flip, our radiation protection goes down, radiation sponsors mutation, mutation sponsors evolution.

    “Certainly, life has survived through many such events before…” -Astrofiend Indeed, LIFE has.

    I’m all for the human creature’s egocentric view on things. *insert oblivious ego here as a joke* => Mostly because I’m wonderful. But, honestly, when the EARTH flips its field, I don’t think things like spotty cell phone coverage are going to be a concern next to the pummeling our DNA could take.

    We could well be unrecognizable 100,000 years later having fun re-discovering fire (which I enjoyed as a teenager – so why not again).

    “What are the practical consequences of … when earth flips it’s field?” -Timber

    Reading above, we all understand that the SUN’s activity is related to magnetic activity. A TV show taught me that the Earth’s molten MAGMA beneath the surface responds to magnetic fields as well. If Earth flips in our lifetimes, one practical consequence will be you and me running very quickly to avoid ash clouds and lots of acid rain.

    When I think about this stuff, I try to remove the egocentricm – that’s probably not a good idea. I just see us as terribly fragile – so I try to be a nice guy to everyone I meet. The things going on around us are inconceivably massive and brutal, even to each other. Try not to think about the Earth part too much, Timber. The Sun puts on a ‘brilliant’ show when its lines are wound up. Have a look through the STEREO satellites (I think it is).

  7. You contradicted yourself in the article. If the suns field flips every eleven years, then why is “there no way to predict when it’s going to happen again in the future?”

    I agree with what others are saying: the magnetic field does not flip every eleven years. The eleven years is the period between solar sunspot minimum and maximum. It is not known how often the suns field flips, like you said. But it is a considerable amount of time, on the verge of 250,000 years.

    The significance about this star flipping it’s field is that it happened within a years time. No one has ever seen this happen so the time frame it takes to flip has been under question for quite some time. If it takes a very long time to flip, then earth will suffer a prolonged amount of exposure to the suns radiation. If it happens quickly damage will be minimal. What your article proves is that the flip happens in under a year’s worth of time. If the sun works like this star, then it is possible such a flip may not have very serious consequences for life on Earth.

  8. I think you were a tad confused, Josh. Just read the article – it states the Sun’s magnetic field does flip every 11 years or so, but the ‘erratic flipping’ of the Poles refers to the EARTH’s magnetic field.
    you probably guessed, but I thought I’d point it out. (My apologies, anyway)

  9. “On one sweep the star had one configuration, and later on, the magnetic field was reversed.

    Since this event happened within just two years of observations, it’s likely that tau Bootis flips its field even more quickly than the Sun’s own 11-year cycle.”

    Unless I am missing something, the second statement is not logically correct. Lets look at the same argument but use our sun and look at it from an alien point of view.

    Some alien looks at our sun in 2005, sees one configuration, and then in late 2007, early 2008 and sees a pole flip and then concludes that the pole reversal is every 2 years or so. Well, we know that this is incorrect.

    So why does the fact that the scientists saw a flip in a two year time mean that the star flips every two years? Why couldn’t they have just taken the first measurement towards the end of the cycle, and then the second measurement be after the flip?

  10. …”tau Bootis ‘completely flipped’ its magnetic field”…
    why? was it angry???

  11. We are presently near the beginning of a new solar cycle; evidenced by the reversal of the magnetic polarity of newly forming sunspots. this polarity reversal is coincident with solar field polarity reversal hence, the suns magnetic field does ‘flip’ about every eleven years.

    In addition, the earths magnetic field has been weakening for many decades and we may well be at the start of a new reversal; occurring, on average, about every 60,000 tears as evidenced in the remnant magnetic field record; especially in oceanic basalts. Geologically, there is some evidence that the earths field goes through a phase where the bipolar magnetic field changes to a multi polar configuration, perhaps during reversal, The behavior of the earths field seems to have little direct effect of the biosphere although it may result in a brief (geologically) period of enhanced cosmic ray bombardment.

  12. Mike, I think you did miss something.

    what I got from the article was that Tau Bootis takes less time to complete the polar reversal than our Sun’s 11 years. That star could have a long(ish) period of time between reversals, just a short “flip time”, for lack of a better term.

    Of course, it’s quite possible that I’m off base with my understanding

  13. My question is: For how long does the Solar Minimum go on. According to, Sol has been blank (or nearly so) for many weeks. Has anyone else who reads these comments ever heard of the Maunder Minimum, when Sol was blank for decades and global average temperatures dropped.
    Come On Sunspots!!

  14. Crissysdad makes a good point. At least regionally we are experiencing the most severe winter in 20 years. A lack of sunspots could be one explanation for that, since during the ‘Little Ice Age’ the same thing happened. I think during the 17th-18th centuries no sunspots were recorded for a period of 70 years.

    That would make it tough for anyone trying to get their Sunspotters Observing award from the Astronomical League.

  15. Tim, a man after my own heart. These sciences mesh in, around and with astronomy (as I like to say) like all the roots, bark, branches, twigs and leaves on a tree. I have seen comments to this geologic/magnetic history in more places than one and they make fine sense to my addled old brain.
    I also recall more than one reference to the “Little Ice Age” mentioned by Crissydad and Marcellus.
    Fascinating place, this universe!!

  16. The suns magnetic field does flip every 11 years. This is normal and coincides with the solar max.

Comments are closed.