Neptune

Reprocessed Old NASA Images Finally Reveal The True Colors of Neptune and Uranus

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Four planetary images showing early and reprocessed Voyager 2 photos of Uranus and Neptune, with a U...

Historic color photos of Uranus and Neptune are actually the wrong colors, and a recent study used new data and a lot of math to set the record straight.

In Voyager 2’s full-color photos of the ice giants, Uranus looks pale blue, while Neptune has a deeper, more vivid shade. That’s because Voyager 2’s cameras actually photographed each planet several times, each in a single color, and NASA teams here on Earth combined those single-color shots into the multi-hued composite images we see today. In the process, they enhanced the images to make certain features, like Neptune’s bands of clouds, stand out more. As useful as that was for planetary scientists, it also skewed our perception of what these two long-neglected worlds actually look like.

“Even though the artificially saturated color was known at the time among planetary scientists – and the images were released with captions explaining it — that distinction had come lost over time,” says Irwin in a recent statement to the press.

Irwin and his colleagues used data from Hubble and the VLT to correct the images — a little like space-age art restoration — and solve a decades-old mystery about why Uranus changes colors (stop laughing). They published their work in the Monthly Notices of the Royal Astronomical Society.

four planets on a black backround. The top 2 are Voyager 2 images of Uranus on the left and Neptune ...
This figure shows the original Voyager 2 images, with Neptune in deep, high-contrast blue, and the actual appearance of the two ice giants.

Ice Giants Show Their True Colors At Last

Irwin and his colleagues used data from a spectrograph (an instrument that splits light into the individual wavelengths that make it up) on the Hubble Space Telescope and one on the evocatively-named Very Large Telescope, perched on a mountaintop in Chile. The spectrograph data basically provided a list of which specific wavelengths, or colors, were present in every pixel of their images of Uranus and Neptune. By comparing that data to the [date] Voyager 2 images of the ice giants, the team managed to rebalance the historic images, creating versions that show the planets in more realistic colors.

The two worlds turn out to be close to the same color: a light greenish blue. Neptune has a slightly bluer tint thanks to a thinner layer of haze in its upper atmosphere, but not nearly as blue as it looks in the composite images from Voyager 2.

“Although the familiar Voyager 2 images of Uranus were published in a form closer to ‘true’ color, those of Neptune were, in fact, stretched and enhanced, and therefore made artificially too blue,” says Irwin.

When NASA crews processed the Voyager 2 data, they turned the contrast on Neptune’s image all the way up to make bands of clouds and storms easier to see. That’s a bit like turning up the contrast in a video game so you can see better in weird lighting; you spot details you might otherwise have missed, but you’re not seeing anything in its “true” color. In Neptune’s case, turning up the contrast also turned our image of the planet a deep, vivid blue. It’s a very pretty blue, but it’s not what Neptune would really look like if you were peering out the window of a passing spaceship.

Why Does Uranus Turn Green?

In the process of working out what color the ice giants actually were, Irwin and his colleagues also solved a decades-long mystery about Uranus. They now know why Uranus sometimes turns green (seriously, stop laughing; we mean it).

Earth’s axis is tilted at about a 23-degree angle, which is why we have seasons. Uranus, on the other hand, is at closer to a 90-degree angle; it’s basically lying on its side while it spins. The planet’s 98-degree axial tilt means that each pole points directly at the Sun during its summer solstice and directly away from the Sun during its winter solstice (instead of just sort of leaning one way or the other, as our relatively well-behaved planet does).

At each solstice, Uranus looks greener than it does during the rest of its 84-Earth-year-long Uranian year. And for decades, planetary scientists have been trying to work out why.

Irwin and his colleagues noticed that, based on the spectra from Hubble and the VLT, there’s less methane in Uranus’s atmosphere at the poles than near the equator. But what methane is floating around at Uranus’s poles tends to be ice crystals, drifting in a chilly (and smelly) haze in the upper atmosphere. And those ice crystals reflect a lot of light, which accounts for the seasonal color change.

Methane absorbs red light and reflects blue-green light. So for the parts of the long Uranian year when one pole, swathed in sparkly methane ice clouds, is pointed at the Sun, the whole planet seems to sparkle with greenish reflected light.

And that’s why Uranus turns green (and smells like farts).

Thousands of Worlds Could Lurk Beyond Pluto – This New Animation Shows Them AlI

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Welcome to our cosmic neighbourhood.

 You may be familiar with our Solar System’s eight planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There’s also their famous dwarf-planet companion, Pluto.

But this icy world may just be an appetiser to what lurks beyond in a region called the Kuiper Belt.

 

As this stunning animation suggests, dwarf planets may outnumber regular planets 100- or even 1,000-fold.

However, if a small group of astronomers gets its way, most of these worlds may become fully fledged planets and drop the “dwarf” label.

Where the animation comes from

We first saw the animation in a Reddit post by user Nobilitie. It’s actually a recording of a physics-based simulator game called Universe Sandbox2, according to Dan Dixon, the creator and director of the software.

Each ring represents an object’s orbit, and the mess of rings beyond the inner eight rings all belong to dwarf planets.

In response to the Reddit post, Dixon said the orbits are based on a constantly updated list of candidate worlds maintained by Mike Brown, an astronomer at Caltech.

 “[I]t’s a nice illustration of what is out there!” Brown wrote in an email to Business Insider. “The striking difference between the orderly giant planets and the randomness of the dwarf planets is quite apparent.”

Brown is the person who discovered Eris, a 10th solar system object that’s about 27 percent more massive than Pluto.

artist impression of the dwarf planet Eris

Artist impression of Eris, ESO/L. Calçada and Nick Risinger

His find eventually ‘killed‘ Pluto as a bonafide planet in 2006. That’s when thousands of astronomers voted on new celestial terminology, categorising the world as a “dwarf planet” alongside Eris.

Some astronomers disagreed with the decision, with one going so far as to call it “bullsh-t”. The public also didn’t take it well: Brown has since received a torrent of hate mail from schoolchildren.

Definitions aside, the list kept by Brown sorts objects detected in deep space based on the likelihood of their existence. Larger, inner objects tend to be more certain while farther-out objects are less certain.

Pluto, Eris, Ceres, Makemake, Haumea, and five others meet Brown’s “near certainty” criteria – in other words, they’re definitely dwarf planets and not comets or some other astronomical object. Thirty are “highly likely” to be dwarf planets, 75 are “likely,” and nearly 850 other objects are “probably” or “possibly” dwarf planets.

Brown guessed that about half of the dwarf planet candidates have yet to be detected, bringing their numbers close to 2,000 or more.

Redefining “planet” again?

Pluto's orbit and Kuiper's belt objects

Even Brown’s best estimate may be low, though. In the illustration above, Pluto’s orbit is shown in yellow, and the dots beyond it are Kuiper Belt objects.

“[A]s you can see from the illustration, some of them are on exceedingly elliptical orbits. Those guys are going to spend most of their time at the outer edge of their orbit, so they’re hard to see,” Brown said. “There might be a factor of ~5 more of those objects that we don’t know about!”

Brown doesn’t think nuclear-powered spacecraft like New Horizons, which can last for decades and is now exploring the Kuiper Belt, will discover most of those missing worlds.

“The fact that there are so many of these things out there really shows that the future of their exploration is going to mostly rely on telescopes,” he said.

A twist in all of this is that astronomers are once again wondering what to call floating orbs of rock, metal, and ice in space, according to a poster that seven researchers are presenting this week at the 48th Lunar & Planetary Science Conference.

Instead of categorising worlds as planets, dwarf planets, and moons – terms based on their orbits around the sun and one other – the team wants to simplify the system: As long as an object is big enough to be mostly round and isn’t fusing hot gases (like the Sun), it should be deemed a planet.

If enough astronomers agree with them, the solar system might suddenly contain 110 official planets – and perhaps hundreds or even thousands more if Brown’s list pans out.

Neptune’s New Moon May Be Named after One of Sea God’s Monstrous Children.

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This past Monday, the planet Neptune officially got a new moon, a relatively tiny chunk of rock and ice about as wide as Manhattan is long. The object is currently dubbed S/2004 N 1, and it’s the fourteenth now known to circle that distant icy world. Mark Showalter, a researcher at the SETI Institute in Mountain View, California, found the moon in early July in archived images that the Hubble Space Telescope had snapped between 2004 and 2009. While using special software that stacks up and manipulates sequential images to reveal the motion of orbiting companions around a planet, Showalter tweaked a single line of code, switching the software’s gaze from close-in to Neptune to hundreds of thousands of miles further out. He walked away for an hour, and came back to see the software had found something curious in the old Hubble images, a small white dot that seemed to circle Neptune once every 22.5 hours. Further analyses confirmed it was a moon, one that had previously gone unseen because of its speedy orbit and small size.

 

Such discoveries have become old hat for Showalter, who has also discovered moons around Saturn, Uranus and Pluto. After discovering his two Plutonian moons in 2011 and 2012, Showalter held a contest to allow the public to nominate and vote on its favorite names for both new worlds. The results helped inspire the final names for the new moons, Kerberosand Styx, which wereannounced by the International Astronomical Union (IAU) on July 2.

Shortly after the announcement of Neptune’s newest moon, I called up Showalter to chat about the moon’s environment, its scientific value, and what he plans to name his latest discovery. An edited version of our conversation follows.

Scientific American: Was this a surprise?

Showalter: Not really, no. We went into this more focused on the ring arcs of Neptune, which are peculiar and persistent bright regions in a couple of dust rings around the planet. There were four arcs in the data from Voyager 2’s 1989 flyby, but two of those have now faded away, and we wanted to piece together what’s going on there and make sense of how the arcs are evolving. We always knew there was a possibility for more moons, things that would have been too small for Voyager 2 to see, so we had our eyes peeled the whole time. It’s definitely still a rush to find something like this, though.

Tell us more about the moon — what do we know about it?

We know its orbit pretty well. But we can only see it as an unresolved dot. We don’t even know its color, because to see these things with Hubble you have to use the whitest filters, which don’t give you info about how red, green, or blue something is. Everything else, we infer from context. We can guess how big it is based on how much light it reflects. It sits between two much larger moons, Proteus and Larissa. These and other moons near it all have similar surface reflectivity, or albedo, within 8 to 10 percent of each other. They’re about as dark as asphalt. When we make the educated guess that this moon shares that same albedo, that tells us this thing is probably on the order of 12 miles across.

What would it look like on the surface?

We don’t know for sure, but someday in the distant future, if and when we get a closer look at this thing, we’ll probably find it to be a cratered, irregularly shaped rock. One reason I’m in this field of astronomy — planetary astronomy — is that I like to visualize things, but it’s hard for me to picture a cosmological object like a quasar in my mind. It’s bright, it’s very far away, and that’s about all I can see. But when I think about the objects I study — planets, moons, asteroids, comets — they have landscapes, they can have geysers and volcanoes, they have things that are much more relatable. They’re more “Earth-like,” but also very exotic and different from what we see in our everyday lives. That combination of the familiar and the alien is something anyone who reads science fiction or watches Star Wars or Star Trek can appreciate.

I’m glad you mentioned Star Trek, since so many Trekkies unsuccessfully lobbied to name one of Pluto’s new moons “Vulcan” after Spock’s home planet. Might this new moon get the Star Trek treatment?

Let me just say first that I’m not surprised the IAU nomenclature committee rejected Vulcan despite the support of so many Star Trek fans. I was a little disappointed, but that’s a name already associated with hypothetical objects that may orbit interior to Mercury, so I knew it would be a tough sell. If they didn’t buy it, no problem. It’s still an honor just to have the opportunity to name a moon. Since Vulcan was rejected, I’ve been publicly mocked by William Shatner, and that’s an honor in its own way, too. But getting back to this new moon, the name has to somehow relate to Poseidon or Neptune, the Greek or Roman gods of the sea. At first I thought that wasn’t as interesting as naming Pluto’s moons for minions of Hades, but after a bit of reading I’ve found some great stuff, and I’ve gotten good suggestions from in and out of the research group. And we are talking about involving the public in this again, but having done it once, I know it’s a huge amount of work, whereas I could just sit down with my group in a room and decide on potential names in an hour or two.

One of my favorite possible names comes from The Odyssey, where Odysseus and his crew are on an island with a giant cyclops. That cyclops’s name is Polyphemus, and he is actually a son of Poseidon. “Polyphemus” is also good because it hasn’t yet been used for an asteroid — asteroids have already taken a lot of the great names. So that will probably be on the list. Another is a goddess, a daughter of Poseidon namedLamia. Lamia got in trouble with Zeus and was turned into a nightmarish creature that stalks and eats children. Even into the Middle Ages, people would tell their children to behave themselves, or else the Lamia will get you! So that’s another colorful one. You can probably guess that I’d prefer to name it after a hideous monster. I was a 12-year-old boy once, too, you know.

This is the sixth moon you’ve discovered, and you’re also credited with discovering rings around Jupiter and Uranus. What’s next?

Unlike those earlier moons, this new moon wouldn’t have shown up in the analyses I have done for Hubble observations of Uranus and Pluto, so it might be worth revisiting that data. There are also some very long exposures of the Saturn and Jupiter systems in the archive. Having this refined technique now, where we can take something from being undetectable in a single image to being detectable in several images combined by motion-tracking, is very powerful. One limitation of the technique is that you have to assume what you’re looking for is something in a circular, co-planar orbit, which is generally a good assumption. That’s what lets you extrapolate where an object should be in each image. Who knows, maybe we could find something in these other Hubble datasets, or for that matter even old spacecraft data! You never know what might turn up, so all of these archived observationsshould be reanalyzed at some point. Also, I think anyone would agree that if we sent another spacecraft out to Uranus or Neptune, there would be a huge flood of these sorts of new discoveries coming in, and many of us hope for exactly such a mission from NASA. There’s still so much we haven’t seen around these worlds because they’ve only been visited once, by Voyager 2 as it flew by [in 1989]. The big breakthroughs will always come from actually going to these places and seeing them up close.

Other than the thrill of finding and naming new objects after hideous monsters, what’s the scientific value of this?

Every one of the moons we’ve found, I think, has an interesting story to tell, and you don’t know what story the universe is trying to tell you until you find it. I think it’s possible for a truly boring moon to exist, one that tells you nothing, but so far in the history of solar system science I don’t think we’ve found one. Every moon so far has an interesting story if you look closely enough. In the case of this new moon, I keep wondering how this tiny little thing ended up wedged between two much bigger moons, Proteus and Larissa. This object has .01 percent of the mass between them. It’s minuscule, and yet somehow when they formed together it didn’t just become an extra layer of dust coating Proteus. How did it get left behind? Figuring that out will take some careful study. Neptune’s largest moon, Triton, orbits backwards and was probably captured long ago, and when that happened it must have disrupted any other moons, which means the moons we see today must have somehow re-formed afterward. Maybe this new moon can help us understand more of that early history.

Source: scientificamerican.com