Magnetic storm on Comet Lovejoy

Plasma blobs observed travelling down Lovejoy's tail

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Bright tail of Comet Lovejoy, imaged from Santa Fe, New Mexico, on 11 January – Credit: Jan Curtis

By Matt Atherton

Comet Lovejoy (C/2014 Q2) is currently providing amateur astronomers with a good view, being visible this month as binocular object in dark skies. Now professional astronomers have identified colourful ‘plasma blobs’ on the body, which could be indicate that a magnetic storm is underway.

The blue/green light of the plasma blob is travelling down the tail of the comet, and shows the same colourful glow as the aurora borealis on Earth.

Dr Karel Schrijver, from the Lockheed Martin Advanced Technology Center in California explains this phenomenon: “The tail is not following the comet's head perfectly as we would expect it to follow... its tail gets locked onto the Sun's magnetic field, and gets flicked back and forth.”

When a comet encounters a Coronal Mass Ejection (CME) - a huge eruption of charged particles are ejected from the Sun – Its magnetic field meets the field of a CME  travelling in the other direction. The result is a burst of magnetic energy, which can make waves, or ‘blobs’ in the comet’s tail. These blobs could signal that a magnetic storm is in progress.

The comet itself was discovered by Terry Lovejoy in Queensland, Australia on 17 August 2014, and was only visible at the time by giant telescopes. Since then, the comet has steadily been increasing in visibility.

As recently as last Wednesday, 7 January, Comet Lovejoy was 70 million km away from Earth – that's over nine times the distance from the Earth to the Moon and back again.

Plasma blobs in previous comets have led to a‘ tail disconnection event’. This means that the magnetic field lines are so tightly squeezed together that the entire tail of the comet is ripped off and separates. Most noticeably, this occurred in 2007 to Encke’s Comet, as it passed through a coronal mass ejection.

After the current appearance, comet Lovejoy won’t be visible again for the next 8,000 years, so spot it while you can as it will be difficult to find past 23 January. To find it, look to the right of Orion and below the Pleiades star cluster.

For more information on when and where to spot the comet, get the January 2015 edition of Sky at Night Magazine; on sale now for iOS and Android.

Seven-hour sequence of plasma blob travelling down Comet Lovejoy’s tail on 8 January – Credit: Tony Angel
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