Earth and the International Space Station seen from Space Shuttle Discovery

Backdropped by a blue and white Earth, the International Space Station is seen from Space Shuttle Discovery as the two spacecraft begin their relative separation. Earlier the STS-119 and Expedition 18 crews concluded 9 days, 20 hours and 10 minutes of cooperative work onboard the shuttle and station. Undocking of the two spacecraft occurred at 2:53 p.m. (CDT) on March 25, 2009.

Space Shuttle Discovery, Orbit of the Earth

March 25, 2009

Image Credit: NASA

Planetary Nebula NGC 3918

This dramatic image from the NASA/ESA Hubble Space Telescope shows the planetary nebula NGC 3918, a brilliant cloud of colourful gas in the constellation of Centaurus, around 4900 light-years from Earth.

In the centre of the cloud of gas, and completely dwarfed by the nebula, are the dying remnants of a red giant. During the final convulsive phase in the evolution of these stars, huge clouds of gas are ejected from the surface of the star before it emerges from its cocoon as a white dwarf. The intense ultraviolet radiation from the tiny remnant star then causes the surrounding gas to glow like a fluorescent sign. These extraordinary and colourful planetary nebulae are among the most dramatic sights in the night sky, and often have strange and irregular shapes, which are not yet fully explained.

NGC 3918’s distinctive eye-like shape, with a bright inner shell of gas and a more diffuse outer shell that extends far from the nebula looks as if it could be the result of two separate ejections of gas. But this is in fact not the case: studies of the object suggest that they were formed at the same time, but are being blown from the star at different speeds. The powerful jets of gas emerging from the ends of the large structure are estimated to be shooting away from the star at speeds of up to 350 000 kilometres per hour.

By the standards of astronomical phenomena, planetary nebulae like NGC 3918 are very short-lived, with a lifespan of just a few tens of thousands of years.

The image is a composite of visible and near-infrared snapshots taken with Hubble’s Wide Field Planetary Camera 2. The filters used were F658N, F814W, F555W and F502N, seen in red, orange, green and blue respectively. The image is about 20 arcseconds across.

Image Credit: ESA/Hubble and NASA
Explanation from: https://www.spacetelescope.org/images/potw1015a/

Supernova 1987A

Using the Hubble Space Telescope, astronomers are witnessing the unprecedented transition of a supernova to a supernova remnant, where light from an exploding star in a neighboring galaxy, the Large Magellanic Cloud, reached Earth in February 1987. Named Supernova 1987A, it was the closest supernova explosion witnessed in almost 400 years. The supernova's close proximity to Earth allows astronomers to study it in detail as it evolves. Now, the supernova debris, which has faded over the years, is brightening. This means that a different power source has begun to light the debris. The debris of SN 1987A is beginning to impact the surrounding ring, creating powerful shock waves that generate X-rays observed with NASA's Chandra X-ray Observatory. Those X-rays are illuminating the supernova debris and shock heating is making it glow in visible light. Since its launch in 1990, the Hubble telescope has provided a continuous record of the changes in SN 1987A.

Image Credit: NASA, ESA, and P. Challis (Harvard-Smithsonian Center for Astrophysics)
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_2058.html