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Illustration of the positions of the two STEREO spacecraft show that they attain 180 degrees of separation in Feb. 2011, thus allowing the world to see the entire Sun for the first time
Originally posted by Soylent Green Is People
reply to post by boo1981
To clarify -- you mean seeing the entire Sun at one time (using two spacecraft 180 degrees apart).
We can already see the whole Sun -- but it takes about 30 days time to see it all. The sun rotates once every 27 days, on average. I say "one average" because different parts of the Sun rotate at different speeds.
But this will be the first time that we can see it all at one time.
STEREO's deployment on opposite sides of the Sun solves a problem that has vexed astronomers for centuries: At any given moment they can see only half of the stellar surface. The Sun spins on its axis once every 25 days, so over the course of a month the whole Sun does turn to face Earth, but a month is not nearly fast enough to keep track of events. Sunspots can materialize, explode, and regroup in a matter of days; coronal holes open and close; magnetic filaments stretch tight and—snap!—they explode, hurling clouds of hot gas into the solar system. Fully half of this action is hidden from view, a fact which places space weather forecasters in an awkward position. How can you anticipate storms when you can't see them coming? Likewise researchers cannot track the long-term evolution of sunspots or the dynamics of magnetic filaments because they keep ducking over the horizon at inconvenient times. STEREO's global view will put an end to these difficulties.
February 6, 2011: It's official: The sun is a sphere.
On Feb. 6th, NASA's twin STEREO probes moved into position on opposite sides of the sun, and they are now beaming back uninterrupted images of the entire star—front and back.
"For the first time ever, we can watch solar activity in its full 3-dimensional glory," says Angelos Vourlidas, a member of the STEREO science team at the Naval Research Lab in Washington, DC.
NASA released a 'first light' 3D movie on, naturally, Super Bowl Sun-day:
"This is a big moment in solar physics," says Vourlidas. "STEREO has revealed the sun as it really is--a sphere of hot plasma and intricately woven magnetic fields."