08 novembro 2017
NGC 1055 Close up
Big, beautiful spiral galaxy NGC 1055 is a dominant member of a small galaxy group a mere 60 million light-years away toward the aquatically intimidating constellation Cetus. Seen edge-on, the island universe spans over 100,000 light-years, a little larger than our own Milky Way. The colorful stars in this cosmic close-up of NGC 1055 are in the foreground, well within the Milky Way. But the telltale pinkish star forming regions are scattered through winding dust lanes along the distant galaxy's thin disk. With a smattering of even more distant background galaxies, the deep image also reveals a boxy halo that extends far above and below the central bluge and disk of NGC 1055. The halo itself is laced with faint, narrow structures, and could represent the mixed and spread out debris from a satellite galaxy disrupted by the larger spiral some 10 billion years ago.
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Why Crossbows Were Used Up Until The 1500s
The horizontally-held crossbow was invented by the Chinese around 2,000 years ago. And it was a huge improvement over the simple bow-and-arrow – with a crosspiece and stock added, the crossbow does the work of pulling and holding the string, not the person. This meant the string could have more tension, and therefore the arrows could fly farther and with more power. A well-aimed crossbow arrow could pierce armor.
Attacking from further away also meant the crossbowmen were relatively better-protected – except against other crossbowmen, of course.
Rare Encircling Filament
NASA's Solar Dynamics Observatory came across an oddity that the spacecraft has rarely observed before: a dark filament encircling an active region (Oct. 29-31, 2017). Solar filaments are clouds of charged particles that float above the sun, tethered to it by magnetic forces.
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