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Hubble Reveals Curious Auroras on Uranus

Bright spots of Uranus' short-lived auroras have been imaged with the Hubble Space Telescope.

Astronomers have finally succeeded in capturing the first Earth-based images of the curious and fleeting auroras of Uranus using the Hubble Space Telescope, careful planning… and no small amount of luck.

Unlike Earthly auroras, whose long-lived curtains of glowing green, red and purple have been the subject of countless stunning photos over the past months, Uranus’ auroras are relatively dim and short-lived, lasting only several minutes at most. They were first witnessed on Uranus by Voyager 2 in 1986, but never by any Earth-based telescopes until November of 2011. Using Hubble, an international team of astronomers led by Laurent Lamy from the Observatoire de Paris in Meudon, France spotted two instances of auroras on the distant planet… once on November 16 and again on the 29th.

Two instances of Uranian aurora imaged in Nov. 2011. (L. Lamy)

Auroras are known to be created by a planet’s magnetosphere, which on Earth is aligned closely with the rotational axis — which is why auroras are seen nearest the polar latitudes. But Uranus’ magnetic field is quite offset from its rotational axis, which in turn is tipped nearly 98 degrees relative to its orbital path. In other words, Uranus travels around the Sun rolling on its side! And with a 60-degree difference between its magnetic and rotational axis, nothing on Uranus seems to point quite where it should. This — along with its 2.5-billion-mile (4 billion km) distance — makes for a “very poorly known” magnetic field.

“This planet was only investigated in detail once, during the Voyager flyby, dating from 1986. Since then, we’ve had no opportunities to get new observations of this very unusual magnetosphere,” said Laurent Lamy, lead author of the team’s paper Earth-based detection of Uranus’ aurorae.

Rather than rings of bright emissions, as witnessed on Earth as well as Saturn and Jupiter, the Uranian auroras appeared as bright spots of activity on the planet’s daytime side — most likely a result of Uranus’ peculiar orientation, as well as its seasonal alignment.

It’s not yet known what may be happening on Uranus’ night side, which is out of view of Hubble.

When Voyager 2 passed by Uranus in 1986 the planet was tipped such that its rotational axis was aimed toward the Sun. This meant that its magnetic axis —  offset by 60 degrees — was angled enough to encounter the solar wind in much the same way that Earth’s does. This created nightside auroras similar to Earth’s that Voyager saw.

By 2011, however, Uranus — which has an 84-year-long orbit — was near equinox and as a result its magnetic axis was nearly perpendicular with its orbital plane, aiming each end directly into the solar wind once a day. This makes for very different kinds of auroras than what was seen by Voyager; in fact, there’s really nothing else like it that astronomers know of.

“This configuration is unique in the solar system,” said Lamy.

Further investigations of Uranus’ auroras and magnetic field can offer insight into the dynamics of Earth’s own magnetosphere and how it interacts with the solar wind, which in turn affects our increasingly technological society.

The team’s paper will be published Saturday in Geophysical Research Letters, a journal of the American Geophysical Union.

Read the release from the AGU here.

About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

Comments on this entry are closed.

  • Kenn Hammer April 13, 2012, 9:12 PM

    ur anus

    • Tony Power April 13, 2012, 11:20 PM

      What are you? 12? Grow up you imbecile.

      • Kenn Hammer April 14, 2012, 2:43 PM

        wheres the humor guys..

        • kjellmakrell April 14, 2012, 8:14 PM

          you are unfunny

    • SJStar April 14, 2012, 8:13 AM

      ur idiot

  • G Money April 13, 2012, 11:44 PM

    no wonder my hemorroids have been bothering me

    • SJStar April 14, 2012, 8:18 AM

      Sorry. I’m good at science, but am not an expert in urology. I’d suggest you go to one of those many medical sites on-line, instead.

  • .. .__. April 14, 2012, 1:57 AM

    See my aesthetician – a little bleaching will take away that discoloration.

    While you’re there, you can get that bikini wax in advance of the beach season.

  • bookmanjohn April 14, 2012, 3:28 AM

    Are the ring images real? If so, why invisible close in?

    • gopher652003 April 15, 2012, 2:15 AM

      The rings are real, they’re just very faint.

      • bookmanjohn April 16, 2012, 11:07 PM

        On Sun, 15 Apr 2012 02:15:04 -0000, Disqus wrote

      • bookmanjohn April 16, 2012, 11:07 PM

        On Sun, 15 Apr 2012 02:15:04 -0000, Disqus wrote

  • SJStar April 14, 2012, 6:15 AM

    Thanks for the article. Uranus has been my favourite planet for a while, which seems to have new surprises. It is not as just the sterile world as the Voyage 2 apparently revealed.

    There is also another tiny white emission around the limb of the larger image, which aligns with the inner ring I.e. Intersect with the planet. Also seen are small variations light intensity along the limb.

    As for the usual childish humour nearly all of the other comments here, it no doubt explains why the Father of the gods finally ate most of his children. Most of these guys are obviously at the shallow end of the gene pool, who never exceed an education much beyond elementary kindergarden. Pity.

  • Kevin Frushour April 14, 2012, 6:07 PM

    I THOUGHT I was above juvenile Uranus jokes. Evidently I’m not. I snickered.

  • Matthäus Schulik April 14, 2012, 9:46 PM

    You could have of course mentioned in your article the amazingly cool method they used to track down the auroras. They followed a CME (Coronal Mass Ejection) from the sun throughout the solar system and extrapolated its time of arrival at Uranus from its encounter times with Earth and Jupiter, to be able to point Hubble there at the right moment (Observation time is short and expensive…).
    As your article points out auroras at Uranus are very elusive, so the increased particle densities coming with the CME were used to increase the probability of spotting one at this right time.
    I guess thats what you meant by “careful planning”.
    AND I suggest you check your sources, I’m pretty sure not having seen an image like the one above presumably from 1986 amongst the papers of that time.

    • Jason Major April 15, 2012, 5:30 PM

      True, it appears that was an HST image, not Voyager… and showed clouds, not auroras. Removed.

  • Prism2Spectrum April 15, 2012, 9:52 AM

    – “But Uranus’ magnetic field is quite offset from its rotational axis, which in turn is tipped nearly 98 degrees relative to its orbital path. In other words, Uranus travels around the Sun rolling on its side! And with a 60-degree difference between its magnetic and rotational axis, nothing on Uranus seems to point quite where it should.” ______________________

    Dramatic confirmation of what had been discovered, these glowing aurora of concentrated color(?)?

    A world tipped-over surely has input to explain the “offset” axis anomaly (either by virtue of being on its side, in relation to its Star – which could mean there is more to Magnetospheres and planetary Cores, than is known, or realized. Or from whatever powerful force pushed-over, or terrific impact brutally changed, an Ice Giant’s Solar orientation (so traumatically, it dislocated, shifted its “magnetic field” of directional placement?). Even the “bright spot” aurora may illuminate the order-disrupting wound, like some impossible short-circuit.

    It’s as if whatever battered, or roughly seized Uranus , snapped an aligning world synchrony of normal planet. (Volcanically buried Venus, smothered in shroud of heat, likewise, seems to have suffered some trauma, to understate it; and Mercury too, stripped-naked, and held fast, to a burning Sun enslaved.)

    Above its silent storms, forensic clues to a violent past, traced in dark rubble Rings, and on cold Moons frozen fast, mystery may conceal, as they orbit, like turns of a celestial Ferris Wheel. Interesting surface views might afford, from riding “pods” of frigid moons, orbiting their dark-ringed world, in System’s distant gloom, by a gentler Sun softly lit, as in their skies, Uranus would hugely loom, wrapped suspended in cloud, and exotic forms of ice.

    – “Further investigations of Uranus’ auroras and magnetic field can offer insight into the dynamics of Earth’s own magnetosphere and how it interacts with the solar wind.” ____________________________________________

    And, if not implied, how very important an intact, aligned, synchronized, Core–World–Star orientation is to a stable, Life supporting – Biosphere sustaining – world habitat: our Life-Oasis in Space.

    • SJStar April 15, 2012, 11:15 AM

      What absolute poppycock of unrelated nonsense thickly plied with excessive verbiage !

      All of this nearly totally cloaked personal theory mixed with the ramblings of crazed madman.

      Where to start? Why would anyone bother?

      • Prism2Spectrum April 15, 2012, 1:10 PM

        Your “Repl[ies]“, SJ, have ripping tones of personal address, and expose attitude of offense, that is becoming wearisome to me.

        Once again, you launch into an unrestrained, personal assault against me (“crazed madman”), not just my thoughts. Shred my comments through your narrow blades of cutting words, if you wish – you are presumably given that freedom. But slapping insulting labels, and flinging oblique innuendos, are something else! Your hostility is palpable (probably not only to me).

        “Why would anyone bother?” Yes, SJ, why would anyone bother? Another freedom you have here, is – to skip my comments. Yet you read them (or should that be, read into them).

        If your boat is so easily rocked, maybe you should trade it in for a larger one, of broader mind.

        Signed Mr. “excessive verbiage”.

      • Prism2Spectrum April 15, 2012, 1:10 PM

        Your “Repl[ies]“, SJ, expose a ripping tone of address, that are becoming wearisome to me – and offensive.

        Once again, you launch into an unrestrained, personal assault against me (“crazed madman”), not just my thoughts. Shred my comments through your narrow blades of cutting words, if you wish – you are presumably given that freedom. But slapping-on insulting labels, and flinging-out oblique innuendos, are something else! Your hostility is palpable (probably not only to me).

        “Why would anyone bother?” Yes, SJ, why would anyone bother? Another freedom you have here, is – to skip my comments. Yet you read them (or should that be, read into them).

        If your boat is so easily rocked, maybe you should trade it in for a larger one, of broader mind.

        Signed Mr. “excessive verbiage”.

        • SJStar April 15, 2012, 2:52 PM

          Even more mindlessness. Now your even imagining you are the victim here!

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