In the heart of the Perseus galaxy cluster lies a remarkable galaxy known as NGC 1275, which has long “filaments”of glowing gas that snake out from its center. Astronomers have tried to explain how these beautiful structures can have survived for so long, given that the filaments reach out from their home galaxy into the Perseus cluster, which is a hostile, high-energy environment with a strong, tidal pull of gravity.These combined forces should have ripped apart the filaments in a very short time, causing them to collapse into stars [The Independent].
Now, thanks to images from the Hubble Space Telescope, astronomers say they understand how the filaments have held their shape for over 100 million years: Magnetic fields are keeping the filaments together, they say. The magnetic fields … hold onto the filaments because they wield influence over charged particles – such as protons and electrons – in the filaments’ gas [New Scientist].
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The exact mechanism that triggers the colorful auroras that dance across the night sky near the Earth’s two poles has been revealed by a quintet of NASA satellites. Scientists already knew that disturbances in the Earth’s magnetic field, called “substorms,” bring charged particles into the Earth’s upper atmosphere, where they collide with gas particles. Those gas particles then release energy as light, which flickers across the sky in waves of greens, reds, and blues.
Now, researchers with NASA’s THEMIS mission say they’ve discovered what sets off those magnetic disturbances. The substorms begin far out in space, roughly a third of the way to the Moon, where magnetic fields from the Earth are thrown together and reconnect to sling charged particles back toward the planet, they say [New Scientist].
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Last January, NASA’s Messenger probe swooped past Mercury, dipping down to within 125 miles of its surface to take pictures and scientific measurements of the solar system’s smallest and hottest planet. Now the results have been analyzed, and researchers say the little planet is full of surprises.
Among other revelations, researchers realized that Mercury has a molten iron core that accounts for its strong magnetic field, but that its core is cooling, which explains the fact that the planet has shrunk more than a mile in diameter. Mission scientist Sean Solomon explains: Because solid iron is denser than the liquid form, “as you grow the inner core, the whole volume of the core shrinks,” he says, causing the planet itself to contract [Scientific American]. Messenger’s pictures reveal steep cliffs called “scarps” that researchers believe were pushed upward by the planet’s contraction.
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