The Cassini spacecraft recently sent back images of Saturn's strange hexagon, which was last photographed 30 years ago by Voyager. So what is so unusual about it? In comparing the pictures now from the pictures 30 years ago, scientists have found that the shape of the hexagon has remained unchanged, making it an extremely long-lived weather pattern, perhaps akin to Jupiter's Great Red Spot.

Researchers are trying to determine what causes the weather pattern — which has a diameter more than twice as long as Earth's — how it gets and expels its energy, and how it maintains such a rigid shape. Fortunately, the improved images from Cassini and the fact that Saturn probably has a relatively simple weather model should help the researchers get a better understanding of the hexagon and how weather works on other planets.

Saturn's Mysterious Hexagon Emerges from Winter Darkness [PhysOrg]

Phil Plait over at the Bad Astronomy blog explains further:

They pointed Hubble at a fairly empty region of space, one where very few stars are seen. Then they unleashed the new Wide Field Camera 3 (called WFC3 for short) on it, taking images in infrared wavelengths just outside what the human eye can see… and they let it stare at that spot for a solid 48 hours.

The result? This picture, showing galaxies flippin' everywhere, some seen a mere 600 million years after the Big Bang itself. Because the Universe is expanding, distant galaxies appear to recede from us, and their light gets stretched out. This Doppler Effect - the same thing that makes the sound of a car engine drop in pitch when it passes you at high speed - changes the colors we see from these far-flung galaxies, so their ultraviolet light, for example, gets stretched into visible and even infrared wavelengths. What you are seeing here is actually more energetic light emitted by galaxies that's lost energy traveling across the expanding Universe, so by the time it gets here it's infrared.

So the colors are not "real" in this image; they've been translated into red, green, and blue so we can see them. The reddest objects in the image are most likely the farthest away, and may be as much as 13 billion light years away.

Thirteen billion. With a B.

Plait's deconstruction of this epic photo is worth reading in its entirety... once you're done staring and contemplating the vastness of a cosmos that barely notices the eyeblink of our existence. [Hubblesite via Bad Astronomy Blog]

Download ginormous versions of the image at the link. [Spacetelescope.org via Wired]

Scientists at Caltech think they may have uncovered the reasons for Titan's extremely odd lake arrangement. Data gathered by the Cassini orbiter showed 20 times more area in the Northern extremities were covered by liquid ethane and methane, when compared to the South. The researchers, headed by Oded Aharonson, think that the transport of methane northwards may be due to the elliptical orbit of Saturn, and hence Titan.

Over the course of one Titan year (29.5 Earth years), the Northern hemisphere summer is long and mild, but the Southern hemisphere version is short and intense. That's because in the Southern summer season Titan is around 12% closer to the sun. While this doesn't make a huge difference over the course of a year, it does over a longer time period: It's possible that these uneven seasons result in methane evaporating in the south, drifting northward in the clouds, and then raining prodigiously in the milder north.

Around 32,000 years ago, the situation would have been reversed, with the hydrocarbons traveling Southward instead of North.

This theory is being published in this month's Nature Geoscience. Other possible explanations for the lakes include the idea that there is some (as yet unknown) fundamental difference between the hemispheres. It's also possible the methane transfer happens every season, not gradually.

Check out more of these incredible space pictures over at the photographer's Flickr stream. [s58y on Flickr]

Heart nebula - RGB.

Rosette nebula

Rosette nebula

Barndoor nebula

Elephant trunk nebula

Elephant trunk nebula

Considering hydrogen is the most plentiful element in the universe, astronomers expect to find it pretty much anywhere they look, particularly when stars are involved. And yet the nova in question, classified V445 Puppis, completely lacks the gas. Helium, which is right behind hydrogen as both the second lightest and second most plentiful gas in the universe, has taken hydrogen's place in the composition of V445 Puppis, leading to its designation as a helium nova. Such an object is unique in the history of astronomy, and it might help astronomers better understand how they date the history of the universe.

According to Danny Steeghs, an astrophysicist at the United Kingdom's University of Warwick, V445 Puppis probably came out of a rather unusual kind of binary star system. The star that went nova in 2000 was probably a hydrogen-depleted star that relied on helium to fuel itself and produce light. The other star is likely a white dwarf, the super-dense remnants of a collapsed star that previous went nova. In such systems, the white dwarf sucks in helium from the younger star when it goes nova, which can have one of two possible outcomes.

The first possibility — and the only one observed before V445 Puppis — is that the white dwarf grows in mass and temperature from all the accumulated helium, until it grows beyond what is known as the Chandrasekhar limit, which is about 1.4 times the size of our sun. When this happens, the white dwarf explodes in a special kind of supernova, known as a type Ia supernova.

However, what appears to be happening in the case of V445 Puppis - at least for now - is that the white dwarf is too small to reach the Chandrasekhar limit, and so it will not explode. Instead, the helium radiates out from the binary star system in the bow-tie-like configuration astronomers have observed. Steeghs points out, however, that this may just be a transitional state before V445 Puppis does go supernova, although there's no guarantee that any of us will be around to see such an event.

The subject is of general interest to astronomers because type Ia supernovas are often used to help date different parts of the universe. These supernovas have very consistent luminosities, meaning their brightness is almost entirely determined by their distance from Earth. Thus, type Ia supernovas are hugely useful in determining the distances of their host galaxies, but the supernovas themselves had previously been only poorly understood. Astronomers now hope that, beyond its status as an astronomical curiosity, V445 Puppis will provide a chance to improve our understanding of these supernovas.

[Scientific American]

According to National Geographic:

This new picture of the Crab Nebula combines data from the Chandra X-ray Observatory, the Hubble Space Telescope, and the Spitzer Space Telescope . . . Infrared light caught by Spitzer and visible light seen by Hubble paint the nebula's expanding debris cloud in shades of purple and red. Meanwhile, Chandra's x-ray vision is helping astronomers understand the high-energy particles (seen in blue) coming from the dead star's core, known as a [sic] white dwarf.

I just love that weird tendril of x-rays shooting out of the pulsar. It seems to be emerging from a giant maw in space (which - isn't there a Doctor Who story called Maw In Space? Maybe I'm just on crack).

via National Geographic

The Unidentified Crashing Object colliding with our galaxy is called Smith's Cloud, and is a cloud of hydrogen discovered last year. At the time, scientists believed it had a mass of a million suns, but it's been theorized that it would have to be much larger to have enough gravity to survive the impact. University of Sydney, Australia's Matthew Nichols and Joss Bland-Hawthorn have calculated that Smith's Cloud may, in fact, be up to 100 times larger than originally estimated.

Before you get too worried about the end of all known existence - or, at least, a Crisis On Infinite Earths - take some comfort in the knowledge that, if theories are correct, this has all happened before; according to the trajectory of Smith's Cloud, it would have impacted the Milky Way 70 million years ago. And it's not like anything has changed since then, right? Well, nothing important.

Dark galaxy crashing into the Milky Way [New Scientist]

New Scientist reports that the Japanese Hayabusa asteroid probe is once more on its way back to Earth after scientists worked out a way to use two of the broken engines together to make... one engine:

One engine is still able to spit out positive ions for thrust, but can no longer squirt out negatively charged electrons, a step needed to prevent electric charge buildup on the spacecraft. The team got around this by spewing the required electrons from a second sick engine that retains this ability.

But even with this "frankensteined" engine, scientists at the Japan Aerospace Exploration Agency aren't confident that the probe will reach the Australian outback destination it was supposed to have reached earlier this month; if all goes well, project manager Jun'ichiro Kawaguchi says, it should return in June next year. But, he adds,

This new configuration is very new to us and we are not sure ... how much we can count on [it].

It's like the little probe that can't.

'Frankenstein' fix lets asteroid mission cheat death [New Scientist]

According to NASA:

After forming as a tropical storm over the Southern Indian Ocean on November 14, 2009, Anja strengthened to a cyclone one day later. By November 16, 2009, Anja was a Category 3 cyclone, with maximum sustained winds of 105 knots (195 kilometers per hour), and gusts up to 130 knots (240 kilometers per hour). Anja was located near 14.7 degrees South and 68.3 degrees East.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this true-color image on November 16, 2009. Far away from any major landmasses, Anja sprawls over the Southern Indian Ocean, her long arms spiraling outward, and her eye easily detectable.

via SpaceGadget

The first image consists of a near-infrared view from the Hubble Space Telescope, an infrared view from the Spitzer Space Telescope, and an X-ray view from the Chandra X-ray Observatory, all mashed up. This is one of the most detailed images ever of our galaxy's mysterious core, and exposes the whole range of stellar evolution, from areas bursting with star birth, to hot new stars, to cooler old stars, to black holes.

The X-ray light reveals gas that has been heated to millions of degrees by outflows from the supermassive black hole as well as winds from nearby stars and stellar explosions. The infrared light reveals all of the areas teeming with bright newborn stars.

Check out the other images in our gallery.

Hubble Space Telescope image

Spitzer Space Telescope image

Chandra Observatory image

[NASA]

Researchers at the University of Warwick and Kiel University looked over the data from the Sloan Digital Sky Survey (SDSS), and spotted the two white dwarfs with large amounts of oxygen present, both approximately the size of planets. These stars, SDSS 0922+2928 and SDSS 1102+2054 are 400 and 220 light years from us, and may be some of the most massive that can produce this type of white dwarf.

How did these stars get into this state? Current theories on the lifecycle of large suns (7-10 times the mass of our Sun), state that eventually they'll consume all their hydrogen, helium and carbon, and then either collapse into a white dwarf with an oxygen-rich core, or go supernova before condensing into a neutron star. However, all the white dwarfs spotted previously have been surrounded by a hydrogen an/or helium layer, which obscures us from seeing their cores. Until now.

The current understanding of the process of how these stars are created predicts a carbon-rich layer would surround the core, and prevent the oxygen from making its way outwards. However, the higher the mass of the star, the thinner this layer, so the discovery of two stars with oxygen rich surfaces means they were originally extremely massive stars. They would have had as dense a progenitor star as possible, in order to form a white dwarf. Unfortunately, the data is insufficient to calculate precisely how much mass these stars have, but they're thought to be more than 500 million years old.

Luckily, more information on these stars could soon be available. Head researcher Boris Gänsicke wants to try to measure the mass of the suns, which can be derived from their distance. And according to Gänsicke, "once you know the distance of a star, and you know how bright it is, you can calculate its radius, and for white dwarfs there is a theoretically well-understood relation between mass and radius." They also plan to get more detailed spectroscopy, to confirm whether the elements in their cores line up with what's expected. Gänsicke believes that this research is crucial to understanding where the boundary lies between stars that end their lives as white dwarfs, and those that end as neutron stars.

via Science

Whether or not you believe Pluto is still a planet, it turns out there are tons more bodies in our solar system just like it. As Wired.com explains, we went from thinking that Pluto was a uniquely icy planet among our system of rocky planets and gas giants to realizing that we have a ton of icy planet(oid)s out in the Kuyper Belt:

"When Pluto was first discovered in 1930, it just looked like an oddball," [planetary scientist Alan] Stern said. "We had the four rocky, terrestrial planets and the four big gas giants, and then we had this odd thing Pluto."

But with the discovery of the Kuiper Belt in the 1990s, scientists discovered that the small, icy orb was hardly unique. "We found out that there are a lot of Plutos," Stern said. "In fact, it's the dominant class of planets in the solar system. This transformed our view not only of the solar system, but also of the importance of sending a spacecraft to Pluto. We realized that we had never sent a spacecraft to the most common type of planet."

The Kuiper Belt sounds more and more intriguing as we discover more — like the mysterious red spot on the surface of Haumea, one of the largest objects there. The red spot may be a gas leak, or the result of a recent collision. But most of all, there's the fact that if we ever do get our lazy asses out of this solar system on our way to other stars, then whatever resources are in the Kuiper Belt will be a crucial refueling stop.

Photo by Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. [Wired]

Legault talked to the Wall Street Journal about his hobby, driving all around the world photographing stars, nebulae, galaxies, space shuttles and the International Space Station from the absolute best vantage points. He consults a special website, Calsky.com, to know exactly when various phenomena will be best observed. He's traveled to Angola, Egypt, Russia and Shanghai, China to photograph various stellar phenomena.

The WSJ article contains the best, and simplest, explanation of why so many astrophotography pictures are so brightly colored. In the case of Legault, he uses filters:

[A]ll of the deep-sky pictures of constellations, star clusters, nebulae and galaxies, meteorites and asteroids require an exposure of several hours. For these photographs, Mr. Legault places red, green or blue filters between the camera and the telescope. Without them, the pictures would come out in black-and-white. "I prefer pastel colors because they are the colors we would see if our eyes were more sensitive to low light or if these objects were brighter."

Here are some of our favorite images by Thierry Legault. They're available in much, much higher resolution, along with many other photos, over at his website. [Astrophoto.FR via Wall Street Journal]

Take this image, of the Veil Nebula (NGC 6992). It's so rich with detail, with so many other stars showing up, the sky looks way more crowded than in pictures from the Hubble or other space telescopes or big observatories.

Ditto for this image of the Cocoon Nebula. It's just one phenomenon surrounded by countless stars.

And here's the Horsehead Nebula. Check out the horse's head at almost the exact center of the image.

Here's the nebulae M-8 and M20, with the open cluster M21 (top left) in Sagittarius.

And here's the area of M-8 and M-20.

Here's the galaxy of M-101. A lot of people would have cropped this image a lot closer around the galaxy, but it looks cool with so much space around it.

The galaxy of M-31.

The comet C/2001 Q4 NEAT on May 13, 2004.

Solar activity.

The Moon and Venus in transit.

An earlier version of this panoramic image was an Astronomy Picture Of The Day in 2001, but the Panorama 2.0 is much, much more detailed, and Mellinger has eliminated some distortions and other problems in the original image.

According to a press release from the University of Chicago Press:

Piecing together 3000 individual photographs, a physicist has made a new high-resolution panoramic image of the full night sky, with the Milky Way galaxy as its centerpiece. Axel Mellinger, a professor at Central Michigan University, describes the process of making the panorama in the forthcoming issue of Publications of the Astronomical Society of the Pacific. An interactive version of the picture can viewed on Mellinger's website.

"This panorama image shows stars 1000 times fainter than the human eye can see, as well as hundreds of galaxies, star clusters and nebulae," Mellinger said. Its high resolution makes the panorama useful for both educational and scientific purposes, he says.

Mellinger spent 22 months and traveled over 26,000 miles to take digital photographs at dark sky locations in South Africa, Texas and Michigan. After the photographs were taken, "the real work started," Mellinger said.

Simply cutting and pasting the images together into one big picture would not work. Each photograph is a two-dimensional projection of the celestial sphere. As such, each one contains distortions, in much the same way that flat maps of the round Earth are distorted. In order for the images to fit together seamlessly, those distortions had to be accounted for. To do that, Mellinger used a mathematical model-and hundreds of hours in front of a computer.

Another problem Mellinger had to deal with was the differing background light in each photograph.

"Due to artificial light pollution, natural air glow, as well as sunlight scattered by dust in our solar system, it is virtually impossible to take a wide-field astronomical photograph that has a perfectly uniform background," Mellinger said.

To fix this, Mellinger used data from the Pioneer 10 and 11 space probes. The data allowed him to distinguish star light from unwanted background light. He could then edit out the varying background light in each photograph. That way they would fit together without looking patchy.

The result is an image of our home galaxy that no star-gazer could ever see from a single spot on earth. Mellinger plans to make the giant 648 megapixel image available to planetariums around the world.

[University of Chicago via Axel Mellinger via Examiner]

[The Big Picture]