Dramatic polar light show on Saturn

WASHINGTON — Astronomers using the Hubble Space telescope have taken a series of images featuring the fluttering auroras at the north pole of Saturn. The observations were taken in ultraviolet light and the resulting images provide astronomers with the most comprehensive picture so far of Saturn’s northern aurora.

In 2017, over a period of seven months, the NASA/ESA Hubble Space Telescope took images of auroras above Saturn’s north pole region using the Space Telescope Imaging Spectrograph. The observations were taken before and after the Saturnian northern summer solstice. These conditions provided the best achievable viewing of the northern auroral region for Hubble.

The new observations are detailed in a new study in Geophysical Research Letters, a journal of the American Geophysical Union.

This image is a composite of observations made of Saturn in early 2018 in the optical and of the auroras on Saturn’s north pole region, made in 2017. In contrast to the auroras on Earth the auroras on Saturn are only visible in the ultraviolet — a part of the electromagnetic spectrum blocked by Earth’s atmosphere — and therefore astronomers have to rely on space telescopes to study them. Credit: ESA/Hubble, NASA, A. Simon (GSFC) and the OPAL Team, J. DePasquale (STScI), L. Lamy (Observatoire de Paris)

On Earth, auroras are mainly created by particles originally emitted by the Sun in the form of solar wind. When this stream of electrically charged particles gets close to our planet, it interacts with the magnetic field, which acts as a gigantic shield. While it protects Earth’s environment from solar wind particles, it can also trap a small fraction of them. Particles trapped within the magnetosphere — the region of space surrounding Earth in which charged particles are affected by its magnetic field — can be energized and then follow the magnetic field lines down to the magnetic poles. There, they interact with oxygen and nitrogen atoms in the upper layers of the atmosphere, creating the flickering, colorful lights visible in the polar regions here on Earth.

However, these auroras are not unique to Earth. Other planets in our Solar System have been found to have similar auroras. Among them are the four gas giants Jupiter, Saturn, Uranus and Neptune. Because the atmosphere of each of the four outer planets in the Solar System is – unlike the Earth – dominated by hydrogen, Saturn’s auroras can only be seen in ultraviolet wavelengths — a part of the electromagnetic spectrum which can only be studied from space.

The image, observed with the Space Telescope Imaging Spectrograph in the ultraviolet, shows the auroras surrounding Saturn’s north pole region. In comparing the different observations it became clear that Saturn’s auroras show a rich variety of emissions with highly variable localised features. The variability of the auroras is influenced by both the solar wind and the rapid rotation of Saturn. Credit: ESA/Hubble, NASA & L. Lamy (Observatoire de Paris)

Hubble allowed researchers to monitor the behavior of the auroras at Saturn’s north pole over an extended period of time. The Hubble observations were coordinated with the “Grand Finale” of the Cassini spacecraft, when the spacecraft simultaneously probed the auroral regions of Saturn. The Hubble data allowed astronomers to learn more about Saturn’s magnetosphere, which is the largest of any planet in the Solar System other than Jupiter.

The images show a rich variety of emissions with highly variable localized features. The variability of the auroras is influenced by both the solar wind and the rapid rotation of Saturn, which lasts only about 11 hours. On top of this, the northern aurora displays two distinct peaks in brightness — at dawn and just before midnight. The latter peak, unreported before, seems specific to the interaction of the solar wind with the magnetosphere at Saturn’s solstice.

Hubble has studied Saturn’s auroras in the past. In 2004, it studied the southern auroras shortly after the southern solstice and in 2009 it took advantage of a rare opportunity to record Saturn when its rings were edge-on. This allowed Hubble to observe both poles and their auroras simultaneously.

This video uses different observations of Saturn: While the observations in the optical, showing the planet itself, were made in 2018, the observations of the auroras were collected in 2017. The video shows how the auroras in Saturn’s northern regions vary over time. The variability of the auroras is influenced by both the solar wind and the rapid rotation of Saturn. Credit: ESA/Hubble, NASA & L. Lamy (Observatoire de Paris)

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Tom Halla
August 30, 2018 2:23 pm

Striking pictures.

Pop Piasa
August 30, 2018 2:32 pm

All that hydrogen. A virtually inexhaustible supply of energy if Humanity could only exploit it.

Anthony, Kudos for beating Tony Phillips to press on this story.

August 30, 2018 3:27 pm

Process of aurora generation is somewhat more complex than described in the article. It is a product of ‘magnetic reconnection’ (sort of a magnetic ‘short circuit’) when a vast amount of energy is released and directed at the magnetic poles.
“This science visualization shows a magnetospheric substorm, during which, magnetic reconnection causes energy to be rapidly released along the field lines in the magnetotail, that part of the magnetosphere that stretches out behind Earth. This released energy is focused down at the poles and the resulting flood of solar particles into the atmosphere, causes the auroras at the North and South Poles.” NASA Video Published on 19 May 2013

Reply to  vukcevic
August 30, 2018 5:03 pm

The circular ‘halo’ effect is due to the torroidal shape of the magnetic field lines. Similar images of earth have been taken.

We might eventually be able to calculate the strength of the magnetosphere by measuring the diameter of the halo. That’s not my filed of expertise.

J Mac
August 30, 2018 3:59 pm

Damn – it’s a good time to be alive!
This is hard core planetary ‘climate science’ at it’s best…. and “Way, Waaaaay Cool” to boot!

Related: Saturn’s moon Titan is ‘resource rich’, for human exploration of the solar system.

Tom Abbott
Reply to  J Mac
August 30, 2018 5:00 pm

“Damn – it’s a good time to be alive!”

Yes, if you love science it is definitely a good time to be alive. Discoveries are coming fast and furious! 🙂

Reply to  J Mac
August 30, 2018 5:17 pm

Jupiter’s moons are closer, and Mars is even closer. But, before we set sail for the new world, lets try colonizing the island just off shore first. Lots of mineral wealth there as well, and easily exported back to Earth. A really big push is all that is needed to drop it into the gravity well in which we sit. But, with abundant sunshine and no cloudy days, most of the processing will be done there. And, then the construction of deep space ships will be done at an L1 space port.

Reply to  rocketscientist
August 31, 2018 3:33 am

Confirmed : Water ice too : https://phys.org/news/2018-08-ice-moon-poles.html
Why are the “Gateway” crowd skittish about actually setting up shop on the regolith? Too cold?

Reply to  bonbon
August 31, 2018 9:19 am

Not sexy enough. They’ve been spoon fed Hollywood fiction for so long they forget all the intermediate steps that must first be taken before we make encounters on alien planets. They are all off on flights of fancy touring the galaxy in warp driven cruisers without realizing first you need to create the model “T” version of those cruisers.
…and we don’t have them…yet.

J Mac
Reply to  rocketscientist
September 1, 2018 7:00 pm

Agree with all you said. I was simply trying to stimulate thought and conversation on ‘man in space’ exploration related to the lede topic.

I’m not a ‘rocket scientist’. I am a metallurgical engineer with +30 years R&D and manufacturing experience in aerospace projects, including launch to orbit systems, fusion reactor structural and heat exchanger materials, fighter jet airframe materials development and production manufacturing/assembly, etc.

Personally, I’d give my eye teeth to witness the first metals-rich asteroid brought into earth orbit before I leave this earthly existence!

August 30, 2018 4:27 pm

The radiation from Saturn that puzzles me is low frequency RF.

Saturn is the source of rather strong low frequency radio emissions called Saturn kilometric radiation (SKR). The frequency of SKR lies in the range 10–1300 kHz (wavelength of a few kilometers) with the maximum around 400 kHz. link

That range includes most of the AM broadcast band. Most of the SKR has wavelengths of less than 1 km. A frequency of 300 kHz corresponds to a wavelength of 1 km. Any frequency below that has a wavelength greater than a kilometer.

We can speculate about what causes the SKR but nobody can say for sure.

J Mac
Reply to  commieBob
August 30, 2018 4:31 pm

Saturnian AM ‘Talk Radio’…..

Reply to  commieBob
August 30, 2018 5:08 pm

A beacon for a galactic hydrogen refueling depot? 😉

Bryan A
Reply to  rocketscientist
August 30, 2018 6:56 pm

comment image

Steven Fraser
Reply to  Bryan A
August 30, 2018 8:18 pm

Or, a ‘Stargate Universe’ refuel run…

August 30, 2018 5:05 pm

Anyone who could recommend a good filter that would allow me to see these auroras through my 8″ sct?

Richard Keen
Reply to  JimG1
August 30, 2018 10:05 pm

From the picture caption…
“the auroras on Saturn are only visible in the ultraviolet — a part of the electromagnetic spectrum blocked by Earth’s atmosphere — and therefore astronomers have to rely on space telescopes to study them”
Besides, your retinas aren’t sensitive to those UV wavelengths, except when there’s enough UV to fry your eye.
So we’re stuck looking at the pictures.

Reply to  Richard Keen
August 31, 2018 6:47 am

Thanks Richard. I saw that but there are uv filters for sale so somebody is full of doodoo. So then I thought if uv is blocked by our atmosphere why would I need to filter them out. Then I thought, maybe these uv filters let you see uv through your scope. Too much thinking. My head hurts. And I have quite a collection of solar, planetary and deep sky photos, including the big eclipse last year but am still confused.

Richard Keen
Reply to  JimG1
August 31, 2018 2:44 pm

Jim, those UV filters block out the “near” UV, or sort of a “dark blue”, that gets through the atmosphere. It’s the stuff that, in large quantities, gives sunburn; in lesser quantities it is strongly scattered by the atmosphere (short wavelengths scatter more) and impart a bluish haze over distant objects (like mountains). So photogs use UV filters to clear out that haze, while astronomers use them to clear out atmospheric haze surrounding, say, Mars. Some UV filters are called haze filters.
Also, those near UV wavelengths don’t focus well with lenses made for the visual wavelengths, so a UV filter makes sharper images without a blue fringe. Ever notice that fuzzy deep violet ring round mercury vapor lights? That’s a 405 nm, near UV/violet, glow that eyes don’t focus well.

August 31, 2018 5:53 am

How do gas giants produce a magnetic field ?

Reply to  Robertvd
August 31, 2018 6:48 am

They ain’t all gas all the way down.

Steven Fraser
August 31, 2018 7:28 am

These pics show that the Earth was almost directly between the Sun and Saturn, based on the shadow of the planetary body on the distant side of the ring. In the first photo, the crescent of the shadow is visible on the left side, and in the animation, on the right side.

August 31, 2018 8:43 am

Hubble is amazing to get that kind of detail from Earth orbit. The telescope equipment hasn’t changed in a long time, but processing has improved & its images continue to get better.

Tom Abbott
Reply to  beng135
August 31, 2018 6:46 pm

Hubble has been worth every cent spent on it.

Steven Fraser
September 1, 2018 7:02 am

I am hoping that at some point, a pair of nice big reflector telescopes can be stationed on the lunar poles.

johann wundersamer
September 3, 2018 2:37 am


Why gives the top view of the auroras of Saturn hexagons. Is it because squares are “too angular”, “too edgy” in the “natural environment” of Saturn and octagons are “too round”.

This “little” Cassini and that longvited Hubble telescope are really doing great jobs.

johann wundersamer
September 3, 2018 3:30 am


Why gives the top view of the auroras of Saturn hexagons. Is it because squares are “too angular”, “too edgy” in the “natural environment” of Saturn and octagons are “too round”.

This “little” Cassini and that long-lived Hubble telescope are really doing great jobs.

I should answer my own question:

The reason is that the magnetic field paths of the magnetic field are distributed over a spherical cross-section of 360 ° in integer sections.

and this counting is hexagonal.

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