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  • [♪ INTRO]

  • Ever since 2007, scientists have been seeing huge,

  • fast bursts of radio energy from mysterious sources around the universe.

  • We still don't know why they happen or exactly where they come from.

  • But astronomers keep trying to find more of these fast radio bursts, or FRBs,

  • in the hopes of finally understanding them.

  • Well, last month, scientists using the Canadian telescope CHIME

  • announced nine new confirmed detections,

  • and they've already helped us learn more about these mysterious signals.

  • What's really exciting is that these new detections are all repeaters.

  • Usually, FRBs look like a burst from some part of the sky that never bursts again,

  • but sometimes, in the case of repeaters, the same source will burst multiple times.

  • And no one quite knows what to make of that.

  • Are repeaters totally different from FRBs that just burst once?

  • Are they the same type of object, just in very different environments? Are they aliens?

  • They're probably not aliens.

  • But one of the main questions astronomers are trying to answer is

  • how these two types of FRBs are related, or not related.

  • So in a study published in the Astrophysical Journal Letters last month,

  • scientists took advantage of all this new data

  • to do a statistical comparison of repeaters versus non-repeaters,

  • to see if they could find anything to explain why only some sources repeat.

  • One thing they looked at was the duration of the radio pulses,

  • because if two events have totally different mechanisms,

  • you would expect them to last different amounts of time.

  • They also looked at how the radio waves dispersed, or spread out, before reaching Earth,

  • because that could tell astronomers something about the environment around the FRBs.

  • In the end, they found that repeaters tend to have a longer duration than non-repeaters,

  • but that the signals tend to be dispersed about the same amount.

  • So that suggests that the sources might live in similar environments,

  • but have different mechanisms driving the bursts.

  • This confirms the results of a previous paper based on CHIME data,

  • but the conclusions of both papers rely on a small data set.

  • Fortunately, CHIME has made hundreds of other FRB detections;

  • they just need to be processed and confirmed.

  • So when the CHIME team finishes sifting through all that data someday,

  • scientists will be able to repeat this study with a much bigger sample size,

  • and we'll be even closer to solving the mysteries surrounding FRBs.

  • Next, telescopes like CHIME aren't the only ones taking us into new territory recently.

  • Last week, scientists announced that they'd made a major discovery about Uranus,

  • which they made using 34-year-old data from Voyager 2.

  • Voyager 2 passed Uranus back in 1986.

  • And it found all kinds of stuff right away, like two new rings and eleven moons.

  • But it also picked up on something that no one had noticed before:

  • a plasmoid, charged gas from the planet's atmosphere

  • that gets siphoned into space by the planet's magnetic field.

  • Magnetic fields generally help protect planetary atmospheres,

  • because they deflect the solar wind,

  • which is full of charged particles that can strip an atmosphere away.

  • But a magnetic field can also do the exact opposite

  • and funnel particles from the atmosphere right out into space.

  • Over time, that can change the atmosphere's composition

  • and eventually strip a planet of its atmosphere altogether.

  • So astronomers generally want to know how magnetic fields and atmospheres interact,

  • because it can say a lot about a planet's eventual fate.

  • On Uranus, though, that's complicated.

  • The planet spins sideways, and the magnetic axis makes a 60-degree angle with the axis of rotation.

  • That means that, as Uranus rotates, its magnetic field is wobbling all over the place.

  • It's really complicated to model, and scientists still don't understand it.

  • So, when NASA started thinking about how feasible it would be to revisit Uranus one day,

  • scientists at the Goddard Space Flight Center decided that,

  • first, they needed to take another look at that planet's magnetic field.

  • And since the Voyager mission was the last time we gathered any

  • magnetic data from Uranus, they started by going over all that old data.

  • The measurements Voyager took back in the '80s actually had a really high resolution,

  • but the software and processes that existed back then

  • to analyze that data smoothed over some of the detail.

  • Fortunately, those processes have changed a lot since the 1980s,

  • and in the new study, published last week in the journal Geophysical Research Letters,

  • scientists at NASA were able to use modern techniques

  • to look at the data in much finer detail.

  • That's when we saw something unusual: a spike in the strength of the magnetic field.

  • It almost looked like a heartbeat: a spike up, followed by a spike down.

  • And the scientists who spotted it recognized it as the signature of a plasmoid,

  • one of those magnetic bubbles full of escaped particles from the atmosphere.

  • When they analyzed it further, they found that the plasmoid was

  • a cylinder of atmospheric gas trapped out in the tail of Uranus' magnetic field.

  • Plasmoids with this shape tend to form as bubbles of gas

  • that pinch off from the atmosphere and fly off the spinning planet into space,

  • and the scientists think similar plasmoids could be responsible for

  • anywhere between 15 and 55 percent of the leakage from Uranus' atmosphere.

  • That's a wide range because this is just one data point,

  • so we can't make any sweeping conclusions about the whole planet,

  • but it can help scientists decide what to keep an eye out for future missions.

  • Which is not too shabby for 34-year-old Voyager probe data.

  • Thanks for watching this episode of SciShow Space News!

  • And if you want to learn more about this odd planet,

  • you can check out our episode on the mysteries of Uranus.

  • [♪ OUTRO]

[♪ INTRO]

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ボイジャーの古いデータに天王星の新たな秘密が発見された|SciShow News (Old Voyager Data Has New Secrets About Uranus | SciShow News)

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    林宜悉 に公開 2021 年 01 月 14 日
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