The heliosphere is the bubble-like region of space dominated by the Sun, which extends far beyond the orbit of Pluto. Plasma “blown” out from the Sun, known as the solar wind, creates and maintains this bubble against the outside pressure of the interstellar medium, the hydrogen and helium gas that permeates the Milky Way Galaxy. The solar wind flows outward from the Sun until encountering the termination shock, where motion slows abruptly. The Voyager spacecraft have explored the outer reaches of the heliosphere, passing through the shock and entering the heliosheath, a transitional region which is in turn bounded by the outermost edge of the heliosphere, called the heliopause.
The shape of the heliosphere is controlled by the interstellar medium
through which it is traveling, as well as the Sun and is not perfectly
spherical. The limited data available and unexplored nature of these structures have resulted in many theories. The word “heliosphere” is said to have been coined by Alexander J. Dessler, who is credited with first use of the word in the scientific literature.
On September 12, 2013, NASA announced that Voyager 1 left the heliopause on August 25, 2012, when it measured a sudden increase in plasma density of about forty times. Because the heliopause marks one boundary
between the Sun’s solar wind and the rest of the galaxy, a spacecraft
such as Voyager 1 which has departed the heliosphere, can be said to
have reached interstellar space. source
Abell 2744: Pandora’s Cluster of Galaxies
Image Credit: NASA, ESA, J. Merten (ITA, AOB), & D. Coe (STScI)
The Aurora Named STEVE : What’s in a name? If your name is Strong Thermal Emission Velocity Enhancement aka STEVE, then there’s quite bit behind the name. (via NASA)
Catalog Entry Number 1 : Every journey has first step and every catalog a first entry. First entries in six well-known deep sky catalogs appear in these panels, from upper left to lower right in chronological order of original catalog publication. From 1774, Charles Messier’s catalog entry number 1 is M1, famous cosmic crustacean and supernova remnant the Crab Nebula. J.L.E. Dreyer’s (not so new) New General Catalog was published in 1888. A spiral galaxy in Pegasus, his NGC 1 is centered in the next panel. Just below it in the frame is another spiral galaxy cataloged as NGC 2. In Dreyer’s follow-on Index Catalog (next panel), IC 1 is actually a faint double star, though. Now recognized as part of the Perseus molecular cloud complex, dark nebula Barnard 1 begins the bottom row from Dark Markings of the Sky, a 1919 catalog by E.E. Barnard. Abell 1 is a distant galaxy cluster in Pegasus, from George Abell’s 1958 catalog of Rich Clusters of Galaxies. The final panel is centered on vdB 1, from Sidney van den Bergh’s 1966 study. The pretty, blue galactic reflection nebula is found in the constellation Cassiopeia. via NASA
AR9077: Solar Magnetic Arcade
On July 14th, solar active region 9077 (AR9077) produced a massive flare. The event also blasted an enormous cloud of energetic charged particles toward planet Earth, triggering magnetic storms and dramatic auroral displays. This striking close-up of AR9077 was made by the orbiting TRACE satellite shortly after the flare erupted. It shows million degree hot solar plasma cooling down while suspended in an arcade of magnetic loops.
Credit: TRACE, Stanford-Lockheed ISR, NASA
There’s Always Pi! : Just by determining how circular a given crater is – using pi and the crater’s perimeter and area – planetary geologists can reveal clues about how the crater was formed and the surface that was impacted. (via NASA)
Remnants from a star that exploded thousands of years ago created a
celestial abstract portrait, as captured in this NASA Hubble Space
Telescope image of the Pencil Nebula.
Credit: NASA and The Hubble Heritage Team (STScI/AURA)
IRAS 05437+2502 – Still a little-know nebula
NGC 1309: Spiral Galaxy and Friends
Image Credit: Hubble Legacy Archive, ESA, NASA; Processing – Jeff Signorelli
Night Sky Highlights: March to May : What might you see in the night sky over the next few months? The featured graphic gives a few highlights. Viewed as a clock face centered at the bottom, sky events in March fan out toward the left, April toward the top, and May toward the right. Objects relatively close to Earth are illustrated, in general, as nearer to the cartoon figure with the telescope at the bottom center – although almost everything pictured can be seen without a telescope. Sky highlights this season include a bright Venus in the evening sky during March, the Lyrids meteor shower during April, and Jupiter entering the evening sky during May. As true in every season, the International Space Station (ISS) can be sometimes be found drifting across your sky if you know just when and where to look. via NASA