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Klaus Seiersen
17,567 followers -
Medical physicist, blogger and science communicator.
Medical physicist, blogger and science communicator.

17,567 followers
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It's as if these technologies were brought back from the future for "Back to the Future":

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SkySafari 4 for Android
I upgraded from version 1.8 to 4 of SkySafari, which I think is the best astronomy app for Android for reasons I told here https://goo.gl/79GUE1 I got SkySafari 4 Plus, an app of the SkySafari product line: https://play.google.com/store/apps/details?id=com.simulationcurriculum.skysafari4plus

What’s new
Although version 4 was completely rebuilt for Android and includes many changes and new features, if you are familiar with earlier versions you’ll notice a new user interface look based on the old one, as well as new artwork and app icons.

A nice new feature is animated meteor showers. Search for a shower and tap the Center button to get an animated view, as in this screenshot of the Perseids on my Nexus 6 phone.

Also of note are the new date and time dialog, which lets you go back or forward by thousands of years to reproduce past or future astronomical events, and new horizon panoramas, such as the Mauna Kea observatory.

I’m not sure SkyWeek is new but it’s a really handy observing guide. The SkyWeek button in the main toolbar lets you view upcoming celestial phenomena in a list reported by Sky & Telescope magazine.

#Android #Astronomy
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Ceres' bright spots - a familiar comparison. Just sayin'...
#Ceres #astronomy #comparison  
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Two Worlds, One Sun

There’s an image going around of a blue sunset on Mars. Yes, it’s a real image, and yes, the colors are reasonably true to life. It was taken by the Curiosity rover in April. Given that sunsets on Earth are typically red, how does Mars get a blue sunset? It all has to do with the way light scatters in the atmospheres of Earth and Mars.

Earth has a relatively thick atmosphere, so most of the atmospheric scattering occurs when light strikes a molecule of air, known as Rayleigh scattering. Rayleigh scattering occurs when the object a photon scatters off (the air molecule) is much smaller than the wavelength of the photon. The closer the wavelength is to the size of the molecule, the more likely it is to scatter. This means that red wavelengths (which are the longer wavelengths of visible light) don’t scatter with air molecules much, while blue wavelengths (which are shorter) tend to scatter a lot. In fact blue light is almost 10 times more likely to scatter against air molecules than red light. This is why the sky appears blue, since so much of the blue light is scattered.

When the Sun is low in the sky, it’s light has to travel a long path through the atmosphere to reach you. As the light travels through the atmosphere some of the photons are scattered off the air molecules. When the photons scatter off air molecules, they scatter randomly in all directions, so usually when a photon scatters, it scatters away from your line of sight. Since blue photons scatter much more often than red ones, much of the blue light is scattered away. This leaves red photons to reach your eye. Hence the Sun looks red when low in the sky. When the Sun is overhead, the path it takes to reach you is much shorter, so only a bit of the blue light is scattered. So the Sun looks yellow.

Mars has a much thinner atmosphere, so the amount of Rayleigh scattering is much less. But Mars also has a dry, dusty surface, and a weaker surface gravity, so the atmosphere of Mars is often filled with fine dust particles. These particles are more comparable in size to the wavelengths of visible light, so most of the light is scattered by Mie scattering. One of the main differences between Rayleigh and Mie scattering is that Rayleigh scattering tends to occur in all directions, but Mie scattering varies with scattering angle. What this means is that longer wavelengths (reds) tend to scatter more uniformly, while shorter wavelengths (blues) tend to scatter at slight angles. This means that blue light tends to be deflected less than red light. This means Mars can have a dusty red daytime sky, and a blue sunset.

Mie scattering does occur on Earth as well, but since Mie scattering is less efficient than Rayleigh scattering it’s never strong enough to give us a blue sunset. It can (rarely) produce a blue moon. The most widespread incidence of modern history occurred after the eruption of Krakatoa in 1883, which sent so much ash into the atmosphere it produced brilliantly red sunsets and visibly blue moons all across the globe for nearly two years. As a result, the phrase “once in a blue moon” came to mean a rare occurrence.

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Landmannalaugar
Landmannalaugar is a volcanic hotspot in the country’s southern highlands. Landmannalaugar is famous for the multi-coloured mountains caused by the interaction of rhyolite rock and geothermal gasses. It is tough to drive there, the road is tough for a car, but a jeep copes with the rough road much better.

#iceland #icelandphotography #volcanic #enjoyyourtime
http://icelandaurora.com/tours/landmannalaugar/
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The Sky from Mauna Kea
Image Credit & Copyright: Shane Black Photography; Rollover Annotation: Judy Schmidt
http://apod.nasa.gov/apod/ap150511.html

What if you could stand at the top of a volcano and peer out across the universe? It the timing is right, you might see an amazing panorama like the one featured here. In this case, the volcano is the Hawaii's Mauna Kea, and the time was a clear night last summer In the foreground of this south-facing panorama lies a rugged landscape dotted with rocks and hardy plants. Slightly above and further out, a white blanket of clouds spreads horizontally to the horizon, seemingly dividing heaven and Earth. City lights illuminate the clouds and sky on the far left, while orange lava in the volcanic caldera of Kilauea lights up the clouds just left of center. The summit of an even more distant Hawaiian volcano, Mauna Loa, is visible in dark silhouette near the central horizon. Green airglow is visible above the clouds, caused by air molecules excited by the Sun during the day. The Moon is the bright orb on the right. A diffuse band of light-colored zodiacal light extends up from the far right. Most distant, the dramatic central band of our Milky Way Galaxy appears to rise vertically from Mauna Loa. The person who witnessed and captured this breathtaking panorama stands before you in the image center.
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Northern Equinox Eclipse
Image Credit & Copyright: Stan Honda
http://apod.nasa.gov/apod/ap150321.html

Snowy and cold is weather you might expect at the start of spring for Longyearbyen on the Arctic archipelago of Svalbard, Norway. But that turned out to be good weather for watching the Moon's umbral shadow race across northern planet Earth. The region was plunged into darkness for 3 minutes during the March 20 total solar eclipse while insulated eclipse chasers witnessed the dark Sun in the cold clear sky. In this well-timed snapshot captured near the end of totality, the Moon's shadow sweeps away from the horizon and the solar corona fades as the lunar disk just begins to uncover the Sun. Streaming past the Moon's edge, direct rays of sunlight create the fleeting appearance of a glistening diamond ring.
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Aurora over Icelandic Glacier
Image Credit & Copyright: James Boardman Woodend (Images Inspired by Nature)
http://apod.nasa.gov/apod/ap150310.html

Several key conditions came together to create this award-winning shot. These included a dark night, few clouds, an epic auroral display, and a body of water that was both calm enough and unfrozen enough to show reflected stars. The featured skyscape of activity and serenity appeared over Iceland's Vatnajökull Glacier a year ago January, with the Jökulsárlón Iceberg Lagoon captured in the foreground. Aurora filled skies continue to be common near Earth's poles as our Sun, near Solar Maximum, continues to expel energetic clouds of plasma into the Solar System.
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