Best views yet

This image shows a region in Saturn’s outer B ring. NASA’s Cassini spacecraft viewed this area at a level of detail twice as high as it had ever been observed before. Image Credit: NASA/JPL-Caltech/Space Science Institute

Newly released images showcase the incredible closeness with which NASA’s Cassini spacecraft, now in its “Ring-Grazing” orbits phase, is observing Saturn’s dazzling rings of icy debris.

The views are some of the closest-ever images of the outer parts of the main rings, giving scientists an eagerly awaited opportunity to observe features with names like “straw” and “propellers.” Although Cassini saw these features earlier in the mission, the spacecraft’s current, special orbits are now providing opportunities to see them in greater detail. The new images resolve details as small as 0.3 miles (550 meters), which is on the scale of Earth’s tallest buildings.

Cassini is now about halfway through its penultimate mission phase — 20 orbits that dive past the outer edge of the main ring system. The ring-grazing orbits began last November, and will continue until late April, when Cassini begins its grand finale. During the 22 finale orbits, Cassini will repeatedly plunge through the gap between the rings and Saturn. The first finale plunge is scheduled for April 26.

For now, the veteran spacecraft is shooting past the outer edges of the rings every week, gathering some of its best images of the rings and moons. Already Cassini has sent back the closest-ever views of small moons Daphnis and Pandora.

Some of the structures seen in recent Cassini images have not been visible at this level of detail since the spacecraft arrived at Saturn in mid-2004. At that time, fine details like straw and propellers — which are caused by clumping ring particles and small, embedded moonlets, respectively — had never been seen before. (Although propellers were present in Cassini’s arrival images, they were actually discovered in later analysis, the following year.)

Cassini came a bit closer to the rings during its arrival at Saturn, but the quality of those arrival images (examples: 1, 2, 3) was not as high as in the new views. Those precious few observations only looked out on the backlit side of the rings, and the team chose short exposure times to minimize smearing due to Cassini’s fast motion as it vaulted over the ring plane. This resulted in images that were scientifically stunning, but somewhat dark and noisy.

In contrast, the close views Cassini has begun capturing in its ring-grazing orbits (and soon will capture in its Grand Finale phase) are taking in both the backlit and sunlit side of the rings. Instead of just one brief pass lasting a few hours, Cassini is making several dozen passes during these final months.

“As the person who planned those initial orbit-insertion ring images — which remained our most detailed views of the rings for the past 13 years — I am taken aback by how vastly improved are the details in this new collection,” said Cassini Imaging Team Lead Carolyn Porco, of Space Science Institute, Boulder, Colorado. “How fitting it is that we should go out with the best views of Saturn’s rings we’ve ever collected.”


Mornings bring planetary possibilities

Illustration: Five Planets Visible in the Pre-Dawn Sky
Five Planets Visible in the Pre-Dawn Sky

Over recent weeks we have watched as several planets have appeared close together in our morning sky — when clear, that is — and even seen them shift their positions as the days passed! Beginning this frigid week and continuing into mid-February, five of Earth’s Solar System siblings will be visible, spanning the southern sky. This is the first time since 2005 that this planetary lineup has occurred. If we get a break in morning cloud cover go out, just before dawn’s early light, and look for the planetary parade. Little Mercury will be the hardest to spot being both dim and close to the horizon. Venus and Jupiter will be easy as they are the brightest of the bunch. Golden Saturn and finally reddish Mars should also be easy to find though Mars isn’t a standout. The gathering will occur again late this summer and in the evening sky. The planets aren’t really very much closer together in space during this time. The chart below illustrates the current relative positions of the planets; it’s our point of view from Earth that makes creates the scene: something like watching racers on a race track, appearing closer and farther apart as they run laps in their concentric lanes.

Illustration: Lines of Sight Illustrate the Field of View from Earth
Lines of Sight Illustrate the Field of View from Earth

So… is there really a NEW PLANET? Nope!

by Jay Reynolds, CAA Observatory Director

So… is there really a new planet? Nope, at least not by the current definition of a planet.**

Thanks to new technology and techniques, the astronomy community has been making interesting finds recently. Our telescopes are becoming more sensitive and allow us to see more & more dimmer and smaller objects. These objects aren’t new, they’ve just been discovered.

The object called Biden (2012 VP113) is big, but does not meet the test for being labeled a planet.

**Definition of a planet
As of 2006, a planet must meet these qualifications:

    1. Must orbit the sun
    2. Must be large enough to be a sphere
    3. Must be free of major gravitational influences of its orbit
    4. Must not revolve around another planet

This newly-discovered object does orbit our Sun, is a sphere, does not revolve around another planet, but its orbit is greatly influenced by many other objects, including Neptune.

Its orbit is 24 degrees off of the planetary plane; Pluto’s is only 17 degrees. This suggests a different developmental history than “planets”

Try to refer to Biden as a DWARF PLANET.

Why is it called Biden? It’s easier than calling it 2012 VP113. The letters VP remind you of U.S. Vice-President (VP) Biden, 10 years ago they may have referred to it as Cheney or Gore. Biden is a temporary, informal name; the I.A.U. would never allow it to stick. About eight years ago, the dwarf planet Eris was referred to as Xena (The Warrior Princess). I’m sure Lucy Lawless was disappointed when her character was dropped.

May’s planetary dance


PLANETS AT DAWN: No coffee? No problem! To wake up any morning this week, all you need to do is look out the window. Mars, Jupiter, Venus and Mercury are aligning in the eastern sky for a spectacular dawn conjunction. Mariano Ribas observed the gathering on May 9 from his home in Buenos Aires, Argentina and wrote, “It was an awesome morning with an unforgettable view: four planets packed in just a 7º piece of sky.”

“The very compact Venus-Mercury-Jupiter triangle was simply hypnotic,” Ribas said. “And Mars, below them, was faint but still clearly visible to naked eye. Marvelous planetary gathering, but the best is yet to come.”

Indeed, on May 11th, Venus and Jupiter, the two brightest planets in the Solar System, will converge to form a pair less than 1/2 degree apart. Set your alarm for Wednesday morning and begin the day with an eye-opener–no caffeine required.

See the full story NASA Science News: