Theorem of a Supernova - The NuSTAR Mission
NuSTAR has provided the first observational evidence in support of a theory that says exploding stars slosh around before detonating. That theory, referred to as mild asymmetries, is shown here in a simulation by Christian Ott of the California Institute of Technology, Pasadena.
In this simulation, a supernova explosion is already underway. The small circle in the center represents the material that will form the dense star at the center of a supernova remnant, called a neutron star. The bright ring surrounding it is the shock wave created in the explosion. The colors represent temperature fluctuations. When the movie starts, the explosion has “stalled out,” because the material falling back onto the neutron star has backed up, like too many cars on the freeway, blocking the shock wave from progressing.
As the explosion continues, material starts to slosh around, reenergized by particles called neutrinos. The neutrinos heat up the material more and more, causing the hot regions to rise into the cooler regions and form large bubbles in the material. Once the bubbles break through the surrounding material, it’s as if the top of a pressure cooker blows off. There’s nothing holding back the shock wave any more and the star explodes.
Credit: NASA/Christian Ott/Caltech

The Whirlpool Galaxy

M51, also known as NGC 5194 or the Whirlpool Galaxy, is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of this image. The companion’s gravitational pull is triggering star formation in the main galaxy, as seen in brilliant detail by numerous, luminous clusters of young and energetic stars. The bright clusters are highlighted in red by their associated emission from glowing hydrogen gas.
The Whirlpool galaxy, M51, has been one of the most photogenic galaxies in amateur and professional astronomy. Easily photographed and viewed by smaller telescopes, this celestial beauty is studied extensively in a range of wavelengths by large ground- and space-based observatories. This Hubble composite image shows visible starlight as well as light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms.
Credit: NASA/Hubble

New Horizons Flies By Neptune Exactly 25 Years After Voyager 2 In what NASA is calling a “cosmic coincidence” the New Horizons probe makes its flyby of Neptune on the 25th anniversary of Voyager 2’s Neptune encounter. On August 25, 1989, Voyager 2 made its closest flyby of Neptune, making it the first spacecraft to study the planet. During Voyager 2’s flyby, it discovered a massive anticyclonic storm system called the Great Dark Spot, similar to Jupiter’s Great Red Spot. Today, NASA’s New Horizons probe is embarking on an equally exciting journey to another world never before visited by a spacecraft. When the spacecraft arrives on July 14, 2015, it will provide the first detailed images of Pluto. The dwarf planet is so distant from us that even images captured by the Hubble Space Telescope appear blurry. Read more about the New Horizons mission and Voyager 2’s flyby of Neptune here:

NGC 3501 The thin, glowing streak slicing across this image cuts a lonely figure, with only a few foreground stars and galaxies in the distant background for company. However, this is all a case of perspective; lying out of frame is anothe…r nearby spiral. Together, these two galaxies make up a pair, moving through space together and keeping one another company. The subject of this Hubble image is called NGC 3501, with NGC 3507 as its out-of-frame companion. The two galaxies look very different — another example of the importance of perspective. NGC 3501 appears edge-on, giving it an elongated and very narrow appearance. Its partner, however, looks very different indeed, appearing face-on and giving us a fantastic view of its barred swirling arms. While similar arms may not be visible in this image of NGC 3501, this galaxy is also a spiral — although it is somewhat different from its companion. While NGC 3507 has bars cutting through its centre, NGC 3501 does not. Instead, its loosely wound spiral arms all originate from its centre. The bright gas and stars that make up these arms can be seen here glowing brightly, mottled by the dark dust lanes that trace across the galaxy. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Nick Rose. ESA/Hubble & NASA Acknowledgement: Nick Rose

Backdropped by a blue and white part of Earth, the aft section of the docked space shuttle Atlantis (STS-129) is featured in this image photographed by a crew member on the International Space Station.

(via APOD: 2014 August 3 - Dark Shuttle Approaching)