Lizard Lemmon Comet loses tail, grows a new one

Comet C/2012 F6 Lemmon photographed on May 15 showing its bluish, ion tail (bottom) beginning to peel away from the comet. The dust tail sticks out to the left. A wispy, new gas tail is already growing above the departing one. Credit: Damian Peach

Solar winds snapped off Comet Lemmon’s ponytail this week and sent it reeling into space. Not to worry. Comets possess the remarkable ability, shared by many species of lizards, to grow new ones. A lizard loses its tail to distract and escape a predator; a comet because its charged atoms – called ions – interact with the breezy blasts of charged particles from the sun called the solar wind.

Magnetic fields in the solar wind tore off Comet Lulin’s tail on Feb. 4, 2007. You can clearly see it falling away in the bottom frame. Credit: Joseph Brimacombe

One day Comet Lemmon was minding its own business and then on Wednesday morning, one of its two tails underwent a “disconnection event”. Comets frequently grow two tails when they orbit near the sun – a pale yellow one of fine dust and a blue one of ionized (electrically charged) gas. The blue color comes from ionized carbon monoxide which fluoresces blue when excited by ultraviolet light from the sun. The larger particles in a comet’s dust tail have no electric charge and aren’t affected by the solar wind; they get pushed away from the comet’s head by the pressure of sunlight.

Charged particles from the sun – electrons and protons – plow through the solar system and continuously interact with comets creating picturesque kinks and ripples in their ion tails. Wrapped up into this electrical mix are solar magnetic fields with north and south-directly poles similar to those on a horseshoe magnet.


Invisible magnetic field lines are made visible around a bar magnet when you sprinkle iron filings around it. The sun’s wind likewise has lines of magnetic force embedded within it created by moving charged (electric) particles.

Electricity and magnetism go hand in hand. A spinning magnet creates an electrical field and an electric current creates a magnetic field. Every time you turn on a lamp, the wires inside the cord are looped by invisible but very real magnetic fields.

Solar flare eruptions like the powerful X-class flares earlier this week can direct huge clouds of magnetized (and electrified) clouds of gas called coronal mass ejections or CMEs into space. When one smacks into a comet, it can rip its tail right off.

Magnetic field lines bound up in the sun’s wind pile up and drape around a comet’s nucleus to shape the blue ion tail. Notice the oppositely-directed fields on the comet’s backside. The top set points away from the comet; the bottom set toward. In strong wind gusts, the two can be squeezed together and reconnect, releasing energy that snaps off a comet’s tail. Credit: Tufts University

Comets present obstacles to the solar wind. The magnetic field carried by the sun’s constant wind gets pushed back by the comet’s electrified gases causing it to drape and flow around the comet’s head. That’s what forms the streamlined blue ion tail in the first place. But when an especially powerful blast of wind blows by, it can elbow its way around the backside of the comet and reconnect with itself, releasing a burst of energy that snaps off the tail.

Diagram showing how a CME slams into a comet (B) to create a tail disconnection event, known in the biz as a DE. Soon enough the comet grows a new one (D). Credit: NASA

In a very real sense, Comet Lemmon experienced a space weather event much like what happens when a powerful solar wind reconnects streams around Earth’s magnetic field and reconnects on the back or nightside of the planet. The energy released sends zillions of electrons and protons screaming down into our upper atmosphere where they stimulate the air molecules to produce auroras. One wonders whether comets might even have their own brief displays of northern lights.

As the solar wind flows away from the Sun, it creates a spiral-shaped interplanetary magnetic field (IMF). Two to four sectors – where the field is pointed toward or away from the sun – spin out every solar rotation (27 days). Each sector Credit: NASA

It’s unclear what pinched Lemmon’s tail since all four large flares from sunspot group 1748 and their associated CMEs weren’t directed at Comet Lemmon.

Maybe the comet crossed a sector boundary where the magnetic field carried across the solar system by sun’s steady breeze changed direction from south to north or north to south. When it sped across the older field wrapped around Lemmon, the two once may have linked up in a burst of energy.

When a lizard loses its tail, it may gain its life, but still suffer for the trouble. For a time, its sense of balance is compromised and important fat reserves stored in the tail aren’t available. Comet Lemmon will be no worse for the wear. As soon as the old tail drifts away, a new one sprouts in its place, cooked up by the ever-steady sun.

Read more about tail disconnections HERE; check out a map for finding Comet Lemmon HERE.

9 Responses

  1. Lynn

    Hi Bob,
    This is probably a silly question, but someone wrote on @asteroidwatch asking about information of a comet that is on @nasa, @asteroidwatch, and then goes onto saying that “we brazillions know that there is a comet with tons of space dust, could hit the earth, or the comet has even come to earth, but this guy wrote this within a tweet that @asteroidwatch had up saying about asteroid 1998 QE2, so I don’t know if he is meaning the asteroid, but seemed strange to mix up an asteroid and a comet, and he also wrote that he was in a statement with the State Department, just wondering if you heard anything or is the ‘comet’ just the start of rumours to do with ISON, just curious if you knew there was anything, as you always know a lot of what’s happening with comet’s. Thanks Bob

    1. Profile photo of astrobob

      1998 QE2 is an asteroid that will miss Earth by 3.6 million miles when it flies by on May 31. No comet is expected or predicted to hit Earth anytime soon.

  2. Giorgio Rizzarelli

    Excellent article Bob and very interesting topic. Together with the sunspots and the X flares, another sign that solar activity is high.

  3. Lynn

    Hi Bob,
    Thanks, I thought it was a silly comment that someone left on @asteroidwatch, but just wanted to check with you, I feel silly for asking it now, but I knew that the asteroid was safe, I just didn’t understand his comment, thanks again:)

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