New Years Sun

The sun on 01 Jan 2015.  Image Credit: NASA/SDO

The sun on 01 Jan 2015. Image Credit: NASA/SDO

An image of the sun on 01 Jan taken by the Solar Dynamics Observatory. The image is dominated by a large coronal hole in the southern hemisphere.  As the sun rotates we should get an idea of the extent of the size.

NASA’s Dean Pesnell explains:

Coronal holes are regions of the corona where the magnetic field reaches out into space rather than looping back down onto the surface. Particles moving along those magnetic fields can leave the sun rather than being trapped near the surface. Those trapped particles can heat up and glow, giving us the lovely AIA images. In the parts of the corona where the particles leave the sun, the glow is much dimmer and the coronal hole looks dark.

Coronal holes were first seen in images taken by astronauts on board NASA’s Skylab space station in 1973 and 1974. They can be seen for a long time, although the exact shape changes all the time. The polar coronal hole can remain visible for five years or longer. Each time a coronal hole rotates by the Earth we can measure the particles flowing out of the hole as a high-speed stream, another source of space weather.

Charged particles in the Earth’s radiation belts are accelerated when the high-speed stream runs into the Earth’s magnetosphere. The acceleration of particles in the magnetosphere is studied by NASA’s Van Allen Probes mission.
As Solar Cycle 24 fades, the number of flares each day will get smaller, but the coronal holes provide another source of space weather that needs to be understood and predicted.

AirBus Jets in Formation

This really isn’t astronomy but I really liked the video. Must have been a sight to see!

The five test and development A350-900s took to the skies for a formation flight in September 2014, bringing together all of the aircraft used for Airbus’ successful campaign leading to certification of this latest Airbus widebody jetliner.

Video

Ceres

The best image of Ceres so far is from Hubble.  The blurry  surface will soon come into focus.  Image Credit: NASA/ESA/J. Parker (SWRI), P. Thomas (Cornell U.), L. McFadden (U-Md., College Park), and M. Mutchler and Z. Levay (STScI)

The best image of Ceres so far is from Hubble. The blurry surface will soon come into focus. Image Credit: NASA/ESA/J. Parker (SWRI), P. Thomas (Cornell U.), L. McFadden (U-Md., College Park), and M. Mutchler and Z. Levay (STScI)

We are very close to getting the best images of Ceres ever as the Dawn spacecraft gets closer to the March encounter. As details emerge we will get to see what the contrasts in the surface really are. Although I’m betting on impact craters I have been fooled many times before.

This image was NASA’s Image of the Day featured yesterday.

The caption released with the image by NASA:

Discovered on Jan. 1, 1801 by Giuseppe Piazzi of Italy, Ceres is the largest object in the asteroid belt – the strip of solar system real estate between Mars and Jupiter. On March 6, 2015, NASA’s Dawn spacecraft will arrive at Ceres, marking the first time that a spacecraft has ever orbited two solar system targets. Dawn previously explored the protoplanet Vesta for 14 months, from 2011 to 2012, capturing detailed images and data about that body. Dawn has entered its approach phase toward Ceres, and the next couple of months promise continually improving views prior to arrival. By the end of January, the spacecraft’s images and other data will be the best ever taken of the dwarf planet.

This image of Ceres was taken by the Advanced Camera for Surveys on NASA’s Hubble Space Telescope between December 2003 and January 2004. Hubble images of Vesta and Ceres helped astronomers plan for the Dawn spacecraft’s tour. Astronomers enhanced the sharpness in the image to bring out features on Ceres’ surface, including brighter and darker regions that could be asteroid impact features. The observations were made in visible and ultraviolet light.

The colors represent the differences between relatively red and blue regions. These differences may simply be due to variation on the surface among different types of material. Ceres’ round shape suggests that its interior is layered like those of terrestrial planets such as Earth. Ceres may have a rocky inner core, an icy mantle, and a thin, dusty outer crust inferred from its density and rotation rate of 9 hours. Ceres is approximately 590 miles (950 kilometers) across.

Battered Mimas

A view of the north polar region of the moon Mimas. Image Credit:NASA/JPL-Caltech/Space Science Institute

A view of the north polar region of the moon Mimas. Image Credit:NASA/JPL-Caltech/Space Science Institute

Cassini took this image of Mimas from just 50,000 km / 31,000 miles on 05 June 2012. North is up and rotated four degrees to the left.

Mimas shows a surface with numerous impact craters. Generally the more craters there are, the older the terrain is. As always there are other factors like surface renewal processes which can erase craters on a few moons. In most cases the rule of thumb prevails.

See the image and JPL caption at the Cassini webpage.

High Phase Geometry

Not the usual bright gem of a planet Saturn tends to be thanks to the “high phase” geometric positioning of Sun, Saturn, and Cassini in this image.

A dark looking Saturn. Image credit: NASA/JPL-Caltech/Space Science Institute

A dark looking Saturn. Image credit: NASA/JPL-Caltech/Space Science Institute

From the Cassini web page:

Saturn’s main rings, seen here on their “lit” face, appear much darker than normal. That’s because they tend to scatter light back toward its source — in this case, the Sun.

Usually, when taking images of the rings in geometries like this, exposures times are increased to make the rings more visible. Here, the requirement to not over-expose Saturn’s lit crescent reveals just how dark the rings actually become. Scientists are interested in images in this sunward-facing (“high phase”) geometry because the way that the rings scatter sunlight can tell us much about the ring particles’ physical make-up.

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