Summer Solstice: A Great Moment to Ponder the Sun
Wednesday at 12:24 a.m. Eastern Time marks the summer solstice, the scientific start to summer for half the world. The Northern Hemisphere will dip toward the sun, basking in its warmth for longer than at any other time. The solstice occurs because the Earth spins on a tilted axis. This slouch of 23.5 degrees is also responsible for the other seasons.
The summer solstice offers the perfect opportunity to ponder the explosive ball of plasma that makes our very existence possible.
And for the United States, this is a remarkable time for the sun. On Aug. 21, the country will experience a total solar eclipse, when the moon passes in front of the sun and casts its shadow on parts of the Earth. The centerline of the eclipse will cut through Oregon, Idaho, Wyoming, Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, North Carolina, Georgia and South Carolina. For about two minutes, sections of those states will experience totality, when the moon engulfs the sun and turns day into night.
During those precious minutes of darkness, skygazers will have the chance to see the sun like they may have never seen it before. Its white outer atmosphere, called the corona, will surround the moon like a lion’s mane. This is the only time when people can see the corona from the ground, and it offers scientists an excellent opportunity to study the sun’s mysteries.
At more than a million degrees, the roaring corona is hundreds of times hotter than the solar surface beneath it, and researchers are not sure why. By studying the corona, scientists hope to better understand the solar processes that fuel its extreme heat and cause its violent eruptions.
But observing the sun from 93 million miles away can yield only so much insight. The information we collect from the eclipse is a preview of the solar data deluge to come over the next decade.
“Everyone who has an opportunity to see totality is going to get a glimpse at a part of the sun that in roughly a year from now we will actually touch,” said C. Alex Young, a solar astrophysicist for NASA.
Next July, NASA plans to launch the Parker Solar Probe, a spacecraft that will probe the plasma puzzle by dipping into the corona. In 2024 it will travel closer to the sun than any Earth spacecraft has ever done before, venturing within four million miles of the scorching surface, according to NASA.
“The main two goals are to understand why the corona is hotter than the surface, and why the solar wind gets accelerated up to a million miles an hour,” said Eric Christian, one of the NASA scientists working on the Parker Solar Probe.
Protected by a special heat shield, the craft will observe the sun’s magnetic field, electrical field and the energetic particles from the solar wind.
“It will revolutionize our understanding of the sun,” Dr. Christian said. “It’s the first time we get to go where the action is.”