NASA Astronomy Picture of the Day 2016 January 27
Why would the sky look like a giant fan? Airglow. The featured intermittent green glow appeared to rise from a lake through the arch of our Milky Way Galaxy, as captured last summer next to Bryce Canyon in Utah, USA. The unusual pattern was created by atmospheric gravity waves, ripples of alternating air pressure that can grow with height as the air thins, in this case about 90 kilometers up. Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction. More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.
As our Cassini spacecraft enters its final 20 months before its plunge into Saturn, the mission’s science team has selected their top 10 images from 2015 (above), a year of historic discoveries, as well as the top science results (below). Take a look:
1. First Deep Seafloor Hydrothermal Vents Found Beyond Earth
Cassini found the first evidence of active hot-water chemistry beyond planet Earth. An extensive, four-year analysis of data from the spacecraft, computer simulations and laboratory experiments led researchers to the conclusion the tiny silica (SiCO2) grains most likely form when hot water containing dissolved minerals from the moon’s rocky interior travels upward, coming into contact with cooler water.
2. Global Ocean Beneath Enceladus’ Surface
A global ocean lies beneath the icy crust of Saturn’s geologically active moon Enceladus. Scientists analyzed more than seven years’ worth of images of Enceladus taken by the spacecraft, which has been orbiting Saturn since mid-2004. As a result, they found Enceladus has a tiny, but measurable wobble as it orbits Saturn. This proves that there must be a global layer of liquid separating the surface from the core.
3. Titan Observed Outside of Saturnian Magnetosphere
During Cassini’s flyby of Titan, the giant moon happened to be on the sunward side of Saturn when a powerful outburst of solar activity reached the planet. The strong surge in the solar wind so compressed the sun-facing side of Saturn’s magnetosphere that the bubble’s outer edge was pushed inside the orbit of Titan. This left the moon exposed to, and unprotected from, the raging stream of energetic solar particles. The region of space dominated by Saturn’s magnetic field is called the magnetosphere.
4. Density of a Ring Particles May Indicate Recent Origins
Saturn’s A ring was found to be warmer than expected at the planet’s equinox, and also had an unusually large thermal asymmetry about the equinox. This could be due to the A ring being mostly composed of denser particles made primarily of solid ice, with a thin top layer of fluffy regolith.
5. Titan Southern Polar Ice Cloud
Scientists have detected a monstrous new cloud of frozen compounds in Titan’s low- to mid-stratosphere – a stable atmospheric region above the troposphere, or active weather layer.
6. Curtain Vents on Enceladus?
New research using data from Cassini suggests most of the eruptions from Saturn’s moon Enceladus might actually be diffuse curtains rather than discrete jets. Many features that appear to be individuals jets of material erupting along the length of prominent “tiger stripe” fractures in the moon’s south polar region might be phantoms created by an optical illusion, according to the new study.
7. Discovery of Tethys Red Arcs
Like graffiti sprayed by an unknown artist, unexplained arc-shaped, reddish streaks are visible on the surface of Saturn’s icy moon Tethys. The origin of the features and their reddish color is a mystery to scientists.
8. Saturn’s 30-year Giant Storms Powered by Water Convection
Changes in temperature and the composition of the hydrogen-laden air within the remnants of a giant storm system on Saturn reveal that air was lofted more than 120 miles in altitude from the deeper water condensation levels.
9. Seasonal Change Seen at Saturn’s Poles
Saturn’s polar regions have displayed extreme seasonal changes during Cassini’s decade-long watch, providing the most comprehensive view ever obtained of seasonal change on a giant planet.
10. Huygens Probe Imaging Mosaic of Titan’s Surface and Descent Movie
Ten years ago, an explorer from Earth, the Huygens probe, was released from the Cassini spacecraft and parachuted into the haze of an alien moon toward an uncertain fate. After a gentle descent lasting more than two hours, it landed with a thud on a frigid floodplain on Titan, surrounded by icy cobblestones.
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NASA just released the out-of-this-world news.
Dark, cold and whipped by supersonic winds, Neptune is the last of the hydrogen and helium gas giants in our solar system. More than 30 times as far from the sun as Earth, the planet takes almost 165 Earth years to orbit our sun! In fact, in 2011, Neptune completed its first orbit since its discovery in 1846.
Here are a few things you might not know about the windiest planet:
If the sun were as tell as a typical front door, the Earth would be the size of a nickel and Neptune would be about as big as a baseball.
Neptune orbits our sun, a star. Neptune is the eighth planet from the sun at a distance of about 4.5 billion km (2.8 billion miles) or 30.07 AU.
One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once)
Neptune makes a complete orbit around the sun (a year in Neptunian time) in about 165 Earth years (60,190 Earth days)
Neptune has six rings
Voyager 2 is the only spacecraft to have visited Neptune
Neptune has 13 moons. They are named after various sea gods and nymphs in Greek mythology
Did you know that Neptune has storms?
Similar to Jupiter, Neptune has storms that create gigantic spots in its atmosphere…well, it did. When Voyager 2 flew past Neptune in 1989, it tracked and imaged the “Great Dark Spot” — a storm larger than the entire Earth! When the Hubble Space Telescope imaged Neptune the spot had disappeared, only to be replaced with two smaller storms, which in turn also disappeared.
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By now you’ve probably heard the news that gravitational waves have been directly observed for the first time ever. Are you excited?
Our friends at PBS Space Time are pretty excited about it too, and they’ve put together an awesome video explaining the physics behind this discovery and why it’s so important.
The bright spot in the lower left is SN 1994D, a star in the midst of a supernova, in the galaxy NGC 4526. During this final performance, the star will briefly outshine its parent galaxy. No supernovae have been observed in our galaxy in over four hundred years.
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It was just discovered that there is a large ocean of water deep within the surface of Saturn’s icy moon, Enceladus.
Did you hear? Astronaut applications are open! Here are a few signs that might mean you’re ready to apply:
1. You Don’t Mind Having Roommates
When you’re an astronaut, you have to work and live with your crew mates for extended periods of time. It’s important to the mission and your safety that everyone can collaborate and work together.
2. You LOVE Space
If the Milky Way, planets and space travel doesn’t excite you then this might not be the perfect job for you. But if you love galaxies, space station research and deep space exploration, then maybe you should take a look at our application.
3. Adventure Doesn’t Scare You
Being an astronaut means that you get to take part in adventures that most people will never experience. Imagine: sitting on the launch pad in the Orion spacecraft, atop a rocket that’s getting ready to launch. You’ll travel farther into space than any other humans have been and help push the boundaries of technology in the proving ground of deep space lunar orbits, leading the way for future missions to Mars.
4. You Want to be on the Cutting Edge of Science
Not only do astronauts get to travel to space, but they also get to conduct really cool research in microgravity. Did you know that right now they’re growing Zinnia flowers on the International Space Station? This research could help with our future deep space exploration and could teach us a few things about growing plants on Earth. Learn more about all the awesome research on the space station HERE.
5. You’re Not Afraid of Heights
One of the coolest things about being an astronaut, is that you get to go to SPACE! At the very least, you’ll travel to the International Space Station, which is 250 miles above Earth. Or, you could be one of the first astronauts to travel to a distant asteroid or even Mars!
Interested in applying to become an astronaut? You’re in luck, applications open Dec. 14! Learn about some common myths about becoming an astronaut HERE.
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"Astronomy compels the soul to look upwards and leads us from this world to another." - Plato
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