Its heat powers the solar
system. Its light makes life on Earth possible. Its gravitational
pull keeps planets in orbit around it.
The sun is, in every sense of the word, a superstar. But despite its
familiarity, there is a lot we don't know about it.
Now, scientists are
planning humanity's closest visit yet to our most familiar star.
The NASA Solar Probe, an unmanned spacecraft scheduled for
launch in 2015, will explore some of the burning questions
scientists have about the sun.
The probe "takes us to where space weather and, indeed,
everything that directly affects life on Earth, starts," said
Loren Acton, research professor of physics at Montana State
University and member of the NASA team that produced the mission
definition report. "I'm really excited to send a probe to where
no mission has gone before."
The project, which costs around $750 million, will be able to
withstand inconceivably high temperatures -- up to 2,600 degrees
Fahrenheit. The probe is being developed at Johns Hopkins
University's Applied Physics Laboratory.
Scientists hope the probe will help them better understand and
forecast solar storms, which occur when the sun accelerates
energetic particles that travel to the Earth along magnetic
field lines at super-high speeds.
Such storms can disrupt power grids and communication satellites
that affect cellphones and GPS navigation. In 1989, a solar
storm caused the HydroQuebec Power Grid to lose power in Quebec,
Canada, resulting in a nine-hour blackout for millions of people
in the province.
Astronauts
in space during a solar storm
are also at risk for absorbing
dangerously large amounts of
solar radiation.
In the same way that hurricane
predictors must consider how the ocean accelerates and powers
hurricanes, scientists hope to understand how the sun accelerates
particles in solar storms.
"This isn't a space weather satellite, but if you do want to have
any hope of predicting solar storms, you have to have a better
understanding of this mechanism than we have," said said Andrew
Dantzler, Solar Probe project manager at the Applied Physics
Laboratory.
Scientists currently believe the storms have to do with the activity
of sunspots, regions of relatively low temperatures where magnetic
field lines have breached the sun's surface. A strong sunspot cycle
may signal strong solar storms, but researchers still have a lot to
learn about forecasting.
Scientists also want to know why the sun's outer atmosphere, called
the corona, is several hundred times hotter than the visible solar
surface, which is where sunlight comes from.
The corona, whose temperature is about 1.8 million degrees
Fahrenheit, seems mysteriously warm considering that the sun's
surface layer, much closer to the star's core, is less than 11,000
degrees Fahrenheit.
The probe will capture images to help solve these puzzles over a
period of almost seven years. During this time, the probe will fly
by Venus seven times, gradually reducing the size of its orbit.
At its closest, the probe will get about 4.1 million miles from the
sun. That may not seem so near, but consider that the sun is about
93 million miles from Earth. The probe will come about eight times
closer to the sun than any spacecraft before it.
The NASA probe will also achieve a top speed of 450,000 miles per
hour, which is three times the record of any man-made object in
space, Dantzler said.
During loops around the inner solar system, two sets of solar arrays
will extend or retract, regulating the temperatures and power levels
of the probe's panels, according to preliminary designs. The probe
itself will weigh about 1,000 pounds, with a shield filled with
carbon foam 9 feet in diameter and 6 inches thick.
"Everything on Earth is affected by the sun. We can't turn off the
sun or change anything about it," Dantzler said. "You can't change
or turn out a hurricane. But you can prepare for it."
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