Northern Sky: August 18 - 31, 2018

NORTHERN SKY – Deane Morrison       Aug. 18-31 2018

At this time of year, the stars and planets have started coming out noticeably earlier. Venus is sinking, but still bright, in the west after sunset. The bright star Spica, in Virgo, is off to the left--our left--of Venus in midmonth. Spica is also dropping toward the western horizon, and it crosses paths with Venus on Friday the 31st. That evening, If you catch them when the sky's dark enough but they haven’t set yet, you’ll see Spica about two and a half moon widths above Venus.
 
Moving east, we have Jupiter, always bright. East of Jupiter and low in the sky is Scorpius, with Antares, the gigantic red star at the heart of the scorpion. Moving east again, we have the lovely Teapot of Sagittarius with Saturn shining above it, and finally Mars. Mars, Venus and Jupiter outshine all the stars, and Mars still outshines Jupiter. But Mars is fading as Earth leaves it behind in the orbital race, and soon Jupiter will reclaim its mantle as the brightest of the outer planets.
 
August's full moon arrives at 6:56 a.m. on Sunday, the 26th. However, the moon sets at 6:07 a.m. that day, so to see it you could go out around 5:30 a.m., or look for it the night before or the night after.
 
In astronomy news, you may have heard that on Sunday, August 12, NASA launched the Parker Solar Probe, an ambitious mission to the one star we can study up close. Parker will fly through the sun’s corona—its outer atmosphere—passing closer to the sun than any previous mission, and University of Minnesota space physicists play an essential role in it. Here’s the scoop.
 
It’s been known for decades that when subatomic particles escape from the sun’s surface their temperature is about 10,000 degrees Fahrenheit. But when they pass through the corona, they get heated to a few million degrees.
 
Scientists have debated how the corona heats these particles so intensely. And also, how the corona accelerates them and spews them out in a torrent of particles that barrels through space at up to a million miles per hour. This stream of particles bathes the solar system and is known as the solar wind.
 
Earth’s magnetic field intercepts the solar wind and shields us against it. When it collides with Earth’s magnetic bubble, it can lead to spectacular auroras. But when it’s fierce, the solar wind can knock out power grids, as it did in Quebec in 1989.
 
Whatever in the corona is heating and accelerating these particles has to be electric and magnetic fields, because that’s all there is. The debate is about the details. The Parker spacecraft carries an instrument, designed by U of M researchers, to study the corona’s electric and magnetic fields and particles. This data will help settle the debate and make it easier to predict the heaviest gusts of the solar wind and take precautions to protect power grids.
 
How close will Parker get to the sun? If Earth and the sun were at opposite goal lines on a football field, the closest any spacecraft has come is the sun’s 29-yard line. But Parker will zip inside the 4-yard line, less than four million miles from the sun. NASA has dreamed of such a mission for 50 years, but the technology took time to develop. For example, engineers had to design a heat shield that’s capable of deflecting temperatures high enough to melt steel. Also, the Parker Solar Probe must, by itself, adjust its orientation to keep its heat shield between the spacecraft and the sun as it hurtles through its tightest loop around the sun at more than 400,000 miles per hour.