Lunar Eclipse seen from Garching

This image was taken by ESO Photo Ambassador Petr Horálek, and shows a partial lunar eclipse near its peak, as visible from the roof of the ESO Headquarters in Garching, Germany on 7 August 2017.

The entire Moon is turned red by its light scattering through the Earth’s atmosphere. Meanwhile, the bottom right part of the full Moon blends into the sky having entered the umbra of the Earth’s shadow.

Image Credit: ESO/P. Horálek
Explanation from: https://www.eso.org/public/images/potw1733b/

Neptune seen from Saturn by Cassini spacecraft

On August 25, 1989, NASA's Voyager 2 made its historic flyby of Neptune and that planet's largest moon Triton. The Cassini mission is publishing this image to celebrate the anniversary of that event.

Neptune appears in this natural color composite as a pale blue disk (similar to Cassini's image of Uranus from 2014), just below and to the right of image center. Most of the faint specks in the image are background stars, although some are likely cosmic rays (charged particles that strike the camera detector).

A cropped and magnified version is provided in monochrome with Triton visible as a point of light above and to the left of Neptune.

In imaging Neptune, Cassini's solar system family portrait-taking is complete. The mission's planetary photojournal includes all of the major planets except Mercury, which is too close to the Sun to be imaged, as well as dwarf planet Pluto.

This view was acquired by the Cassini narrow-angle camera on Aug. 10, 2017, at a distance of approximately 2.72 billion miles (4.38 billion kilometers) from Neptune. Red, blue and green filter images were combined to create the natural color image.

Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21629

Interacting Galaxies MCG+01-38-004 • MCG+01-38-005

Phenomena across the Universe emit radiation spanning the entire electromagnetic spectrum — from high-energy gamma rays, which stream out from the most energetic events in the cosmos, to lower-energy microwaves and radio waves.

Microwaves, the very same radiation that can heat up your dinner, are produced by a multitude of astrophysical sources, including strong emitters known as masers (microwave lasers), even stronger emitters with the somewhat villainous name of megamasers, and the centres of some galaxies. Especially intense and luminous galactic centres are known as active galactic nuclei. They are in turn thought to be driven by the presence of supermassive black holes, which drag surrounding material inwards and spit out bright jets and radiation as they do so.

The two galaxies shown here, imaged by the NASA/ESA Hubble Space Telescope, are named MCG+01-38-004 (the upper, red-tinted one) and MCG+01-38-005 (the lower, blue-tinted one). MCG+01-38-005 is a special kind of megamaser; the galaxy’s active galactic nucleus pumps out huge amounts of energy, which stimulates clouds of surrounding water. Water’s constituent atoms of hydrogen and oxygen are able to absorb some of this energy and re-emit it at specific wavelengths, one of which falls within the microwave regime. MCG+01-38-005 is thus known as a water megamaser!

Astronomers can use such objects to probe the fundamental properties of the Universe. The microwave emissions from MCG+01-38-005 were used to calculate a refined value for the Hubble constant, a measure of how fast the Universe is expanding. This constant is named after the astronomer whose observations were responsible for the discovery of the expanding Universe and after whom the Hubble Space Telescope was named, Edwin Hubble.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1735a/