Sunny Saturn

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The sunny northern hemisphere on Saturn.

NASA:
Sunlight truly has come to Saturn’s north pole. The whole northern region is bathed in sunlight in this view from late 2016, feeble though the light may be at Saturn’s distant domain in the solar system.

The hexagon-shaped jet-stream is fully illuminated here. In this image, the planet appears darker in regions where the cloud deck is lower, such the region interior to the hexagon. Mission experts on Saturn’s atmosphere are taking advantage of the season and Cassini’s favorable viewing geometry to study this and other weather patterns as Saturn’s northern hemisphere approaches Summer solstice.

This view looks toward the sunlit side of the rings from about 51 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Sept. 9, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 728 nanometers.

The view was obtained at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn. Image scale is 46 miles (74 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

The 2016 Time Adjustment

I wonder if when the new year rang in if the countdown included the extra second that was added to the world clocks. Probably not and while it might not seem like much,  the time change is important to our view of the world thanks to our modern technology even if we don’t realize it.

We have added 27  “leap-seconds” to the clock since the practice started in 1972. Read more about adding leap-seconds.

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From (mostly) NASA:   On Dec. 31, 2016, official clocks around the world added a leap second just before midnight Coordinated Universal Time — which corresponds to 6:59:59 p.m. EST. NASA missions also had to make the switch, including the Solar Dynamics Observatory, or SDO, which watches the sun 24/7.

Clocks do this to keep in sync with Earth’s rotation, which gradually slows down over time. When the dinosaurs roamed Earth, for example, our globe took only 23 hours to make a complete rotation. In space, millisecond accuracy is crucial to understanding how satellites orbit.

“SDO moves about 1.9 miles every second,” said Dean Pesnell, the project scientist for SDO at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “So does every other object in orbit near SDO. We all have to use the same time to make sure our collision avoidance programs are accurate. So we all add a leap second to the end of 2016, delaying 2017 by one second.”

The leap second is also key to making sure that SDO is in sync with the Coordinated Universal Time, or UTC, used to label each of its images. SDO has a clock that counts the number of seconds since the beginning of the mission. To convert that count to UTC requires knowing just how many leap seconds have been added to Earth-bound clocks since the mission started. When the spacecraft wants to provide a time in UTC, it calls a software module that takes into consideration both the mission’s second count and the number of leap seconds — and then returns a time in UTC.

Credit: NASA/SDO

Here Comes Another Comet

Hot on the heels of 45P/Honda, here comes C/2016 U1 NEOWISE and it might be visible with binoculars by next week – maybe.  2016 U1 NEOWISE is a telescope target right now and even a modest telescope should see it.

But wait, there’s more!  We may have another possible comet called 2016 WF9 coming too; “possible” being the key-word because we just don’t know for sure.

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Here’s the story from NASA:
NASA’s NEOWISE mission has recently discovered some celestial objects traveling through our neighborhood, including one on the blurry line between asteroid and comet. Another–definitely a comet–might be seen with binoculars through next week.

An object called 2016 WF9 was detected by the NEOWISE project on Nov. 27, 2016. It’s in an orbit that takes it on a scenic tour of our solar system. At its farthest distance from the sun, it approaches Jupiter’s orbit. Over the course of 4.9 Earth-years, it travels inward, passing under the main asteroid belt and the orbit of Mars until it swings just inside Earth’s own orbit. After that, it heads back toward the outer solar system. Objects in these types of orbits have multiple possible origins; it might once have been a comet, or it could have strayed from a population of dark objects in the main asteroid belt.

2016 WF9 will approach Earth’s orbit on Feb. 25, 2017. At a distance of nearly 32 million miles (51 million kilometers) from Earth, this pass will not bring it particularly close. The trajectory of 2016 WF9 is well understood, and the object is not a threat to Earth for the foreseeable future.

A different object, discovered by NEOWISE a month earlier, is more clearly a comet, releasing dust as it nears the sun. This comet, C/2016 U1 NEOWISE, “has a good chance of becoming visible through a good pair of binoculars, although we can’t be sure because a comet’s brightness is notoriously unpredictable,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California.

As seen from the northern hemisphere during the first week of 2017, comet C/2016 U1 NEOWISE will be in the southeastern sky shortly before dawn. It is moving farther south each day and it will reach its closest point to the sun, inside the orbit of Mercury, on Jan. 14, before heading back out to the outer reaches of the solar system for an orbit lasting thousands of years. While it will be visible to skywatchers at Earth, it is not considered a threat to our planet either.

NEOWISE is the asteroid-and-comet-hunting portion of the Wide-Field Infrared Survey Explorer (WISE) mission. After discovering more than 34,000 asteroids during its original mission, NEOWISE was brought out of hibernation in December of 2013 to find and learn more about asteroids and comets that could pose an impact hazard to Earth. If 2016 WF9 turns out to be a comet, it would be the 10th discovered since reactivation. If it turns out to be an asteroid, it would be the 100th discovered since reactivation.

What NEOWISE scientists do know is that 2016 WF9 is relatively large: roughly 0.3 to 0.6 mile (0.5 to 1 kilometer) across.

It is also rather dark, reflecting only a few percent of the light that falls on its surface. This body resembles a comet in its reflectivity and orbit, but appears to lack the characteristic dust and gas cloud that defines a comet.

“2016 WF9 could have cometary origins,” said Deputy Principal Investigator James “Gerbs” Bauer at JPL. “This object illustrates that the boundary between asteroids and comets is a blurry one; perhaps over time this object has lost the majority of the volatiles that linger on or just under its surface.”

Near-Earth objects (NEOs) absorb most of the light that falls on them and re-emit that energy at infrared wavelengths. This enables NEOWISE’s infrared detectors to study both dark and light-colored NEOs with nearly equal clarity and sensitivity.

“These are quite dark objects,” said NEOWISE team member Joseph Masiero, “Think of new asphalt on streets; these objects would look like charcoal, or in some cases are even darker than that.”

NEOWISE data have been used to measure the size of each near-Earth object it observes. Thirty-one asteroids that NEOWISE has discovered pass within about 20 lunar distances from Earth’s orbit, and 19 are more than 460 feet (140 meters) in size but reflect less than 10 percent of the sunlight that falls on them.

The Canadian Lights

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Just hours after the winter solstice, a mass of energetic particles from the Sun smashed into the magnetic field around Earth. The strong solar wind stream stirred up a display of northern lights over northern Canada.

With the “day-night band” (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS), the Suomi NPP satellite acquired this view of the aurora borealis on Dec. 22, 2016. The northern lights stretched across British Columbia, Alberta, Saskatchewan, Manitoba, Nunavut, and Northwest Territories, areas that often fall under the auroral oval.

The DNB detects dim light signals such as auroras, airglow, gas flares, and reflected moonlight. In the case of the image above, the sensor detected the visible light emissions as energetic particles rained down from Earth’s magnetosphere and into the gases of the upper atmosphere.

The collision of solar particles and pressure into our planet’s magnetosphere accelerates particles trapped in the space around Earth (such as in the radiation belts). Those particles are sent crashing down into Earth’s upper atmosphere—at altitudes of 100 to 400 kilometers (60 to 250 miles)—where they excite oxygen and nitrogen molecules and release photons of light. The results are rays, sheets, and curtains of dancing light in the sky.

Suomi NPP is the result of a partnership between NASA, the National Oceanic and Atmospheric Administration, and the Department of Defense.

Annotated image: NASA’s Earth Observatory

Image Credit: NASA Earth Observatory image by Jesse Allen, using VIIRS day-night band data from the Suomi National Polar-orbiting Partnership
Caption: Mike Carlowicz

Magnetic Field Modeling

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We have a mostly quiet Sun these days.

The sun had just a few, small active regions for several days this week and its magnetic field reflected that state of affairs (Dec. 13-16, 2016). Solar scientists using computer-generated models are able to portray the magnetic field lines of the sun over just about any length of time. Here we can see that the overall magnetic field structure is rather symmetrical, stable and untangled. If there were many active regions, we’d see a much more chaotic field. The sun here is shown in a wavelength of extreme ultraviolet light. — Solar Dynamics Observatory, NASA.

From the looks of the current visible image of the solar disk shows an almost spotless face, there is a nice little sunspot group on the right side of the image just above the solar equator:

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The (US) National Oceanic and Atmospheric Administration (NOAA) has a great page to get a variety of up-to-date data pretty quickly: The Space Weather Enthusiasts Dashboard

Images: NOAA/NASA/SDO

Sweet Dreams

A peaceful looking scene from the International Space Station.

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A nighttime view of Western Europe is captured by crew members aboard the International Space Station. England is visible in the top right of the frame, Paris appearing as the bright city near the middle of the image and views of Belgium and the Netherlands occupying the middle-right of frame. — NASA

Image Credit: NASA