August 21, 2017

Solar Eclipse seen over Ross Lake

Solar Eclipse seen over Ross Lake

This composite image shows the progression of a partial solar eclipse over Ross Lake, in Northern Cascades National Park, Washington on Monday, August 21, 2017. A total solar eclipse swept across a narrow portion of the contiguous United States from Lincoln Beach, Oregon to Charleston, South Carolina. A partial solar eclipse was visible across the entire North American continent along with parts of South America, Africa, and Europe.

Image Credit: NASA/Bill Ingalls
Explanation from: https://www.nasa.gov/image-feature/glory-of-the-heavens

Saturn and Tethys

Saturn and Tethys

NASA's Cassini gazes across the icy rings of Saturn toward the icy moon Tethys, whose night side is illuminated by Saturnshine, or sunlight reflected by the planet.

Tethys was on the far side of Saturn with respect to Cassini here; an observer looking upward from the moon's surface toward Cassini would see Saturn's illuminated disk filling the sky.

Tethys was brightened by a factor of two in this image to increase its visibility. A sliver of the moon's sunlit northern hemisphere is seen at top. A bright wedge of Saturn's sunlit side is seen at lower left.

This view looks toward the sunlit side of the rings from about 10 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on May 13, 2017.

The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 140 degrees. Image scale is 43 miles (70 kilometers) per pixel on Saturn. The distance to Tethys was about 930,000 miles (1.5 million kilometers). The image scale on Tethys is about 56 miles (90 kilometers) per pixel.

Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21342

Dwarf Galaxy NGC 178

Dwarf Galaxy NGC 178

NGC 178 may be small, but it packs quite a punch. Measuring around 40 000 light-years across, its diameter is less than half that of the Milky Way, and it is accordingly classified as a dwarf galaxy. Despite its diminutive size, NGC 178 is busy forming new stars. On average, the galaxy forms stars totalling around half the mass of the Sun per year — enough to label it a starburst galaxy.

The galaxy’s discovery is an interesting, and somewhat confusing, story. It was originally discovered by American astronomer Ormond Stone in 1885 and dubbed NGC 178, but its position in the sky was recorded incorrectly — by accident the value for the galaxy’s right ascension (which can be thought of as the celestial equivalent of terrestrial longitude) was off by a considerable amount.

In the years that followed NGC 178 was spotted again, this time by French astronomer St├ęphane Javelle. As no catalogued object occupied that position in the sky, Javelle believed he had discovered a new galaxy and entered it into the expanded Index Catalogue under the name IC 39. Later, American astronomer Herbert Howe also observed the object and corrected Stone’s initial mistake. Many years later, astronomers finally noticed that NGC 178 and IC 39 were actually the same object!

This image of NGC 178 comprises data gathered by the Wide Field Planetary Camera 2 aboard the NASA/ESA Hubble Space Telescope.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1734a/