All the planets, moons, and smaller things in the solar system are just dust, compared to the star that they orbit; the Sun contains 99.9% of the mass of the solar system. We think of it as our source of light, but it doesn't just emit photons. The solar wind blasts fast-moving electrons, protons, and highly ionized atoms in all directions, a constant stream punctuated by ferocious coronal mass ejections. The solar wind carries with it a magnetic field wound into a tight spiral by the Sun's rotation.
The solar wind pushes outward against the interstellar medium, penning the solar system inside a bubble called the "heliosphere" that's at least 200 AU across. The twin Voyager spacecraft are now probing the heliosphere's edges. Closer to home, a fleet of spacecraft monitors the space weather generated by the Sun, warning us of its effects on Earth, from the benevolent (aurorae) to the potentially disastrous (irradiation of astronauts and damage to communications satellites and power grids). Currently operating solar space observatories include ACE, GGS, WIND, Hinode, PICARD, RHESSI, SOHO, SDO, Solar Monitoring Observatory, and STEREO.
Latest Blog Entries about the Sun, Heliosphere, and Space Weather
The upcoming rare transit of Venus is one step in a long dance among Earth, Venus and the Sun. Transits of Venus follow a peculiar pattern—two transits 8 years apart, then 105.5 years with no transits, then two transits 8 years apart, then 121.5 years with no transits, for a total cycle of 243 years—and thereby hangs a tale.
Posted by Emily Lakdawalla on 2012/03/07 09:27 CST
Last night the Sun unleashed a large coronal mass ejection in our direction. Here is a compilation of images from SOHO's two LASCO cameras, plus a prediction from the new space weather prediction model that I learned about at the American Geophysical Union in December. The storm will arrive at Earth on March 8.
Posted by Jason Davis on 2012/01/26 05:26 CST
Before automated space observatories like SDO could send pictures and videos of solar phenomenon in real-time, humans had to do it manually, as in the case of the groundbreaking Skylab space station missions, which featured the Apollo Telescope Mount.
Unless you are lucky and healthy enough to live for another 105 years, tomorrow will be your last chance to see a Venus transit from the surface of the Earth. But this need not be the last transit of Venus that you will ever see.
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