Bakersfield Night Sky — June 17, 2017
by Nick Strobel
The shortest night of the year will be in three days on the night of June 20/21. The sun will reach its farthest northern most position on the sky at 9:24 p.m. on June 20. This is the “June solstice” when the sun stops its northward movement with respect to the stars on our sky and the sun momentarily “stands still”, hence the term “solstice” which means “sun standing still”. This moment marks the official start of our season of summer. For those at a latitude of 23.5 degrees north, the sun will be directly overhead at the zenith at local noon. That latitude is called the “Tropic of Cancer” because when that line of latitude was named about 2000 years ago, the sun was in the constellation Cancer for the June solstice. Two thousand years of the slow wobble of Earth’s rotation axis, called precession, have moved the sun’s position at the June solstice to the constellation Taurus.
The sun’s energy will hit our part of the earth most directly, so the cooking power will be greatest on that day. Also, the sun is above the horizon for the longest amount of time, so the cooking time will be longest on that day. However, like baking something in the oven, it takes a while for everything to warm up, so our hottest days are still to come later this summer.
While we’re on the subject of the sun, NASA recently named its Solar Probe Plus spacecraft as the Parker Solar Probe in honor of the astrophysicist Eugene Parker, who was the first one to figure out that there should be a constant stream of charged particles moving outward from the sun. He introduced his revolutionary idea in a paper in the Astrophysical Journal in 1958. This “solar wind” was confirmed four years later. These charged particles moving at one million miles an hour are responsible for the aurorae on earth and they fill the solar system out to about twice Pluto’s distance from the sun.
Launching in the summer of 2018, the Parker Solar Probe will use a series of close flybys of Venus to bring the spacecraft more than seven times closer to the sun than any spacecraft has gone before. The Parker Solar Probe will get to within 3.9 million miles of the sun’s surface. At that distance it will be flying through the sun’s outer atmosphere, called the “corona”.
While the surface of the sun is about 10,000 deg F, the temperature of the corona is 1.8 million to 3.6 million deg F. At these temperatures, the particles are moving extremely fast. What makes the particles in the corona move so fast has been the subject of intense research for over 60 years. The Parker Solar Probe is going to get close enough to the sun to see how the solar wind increases from subsonic to supersonic speeds and it will fly through where the highest-energy solar particles are made. Despite its high temperature, the corona has a low amount heat because the particles are so far apart from each other. What will heat up the spacecraft is the energy coming from the surface of the sun. The probe is being built to withstand a heat environment of 2500 deg F through recently-developed technology of a carbon-composite material. That material and other cutting-edge thermal engineering advances are needed to protect the four suites of instruments that will study the magnetic fields, plasma and energetic particles and image the solar wind.
One other “first” for this mission is that it is named after someone who is still living. Born in June 1927, Eugene Parker received his doctorate from Caltech in 1951. Since 1955 Parker has held faculty positions at the University of Chicago and at its Fermi Institute.
Almost directly opposite the sun on our sky is the gorgeous ringed planet, Saturn (see the first star chart below). Now among the stars of Ophiuchus, Saturn reached opposition earlier this week on June 14. Opposition is also when Saturn is closest to us for the year. The closer distance and also the angle of its very reflective rings, now tipped wide open towards us, means that Saturn will shine brighter than all the stars in tonight’s sky except Arcturus at the bottom of Bootes. Saturn will be at its highest point around 1 a.m.
Not to be outdone, the king of the planets, Jupiter, blazes about seven times brighter than Saturn. Jupiter is highest due south at about 8 p.m. and sets at 1:50 a.m. tonight. Jupiter has spent the past few months moving retrograde away from the bright star Spica in Virgo. Jupiter has now stopped its retrograde motion and is now slowly inching its way back toward Spica. It will pass Spica in mid-September.
Early morning observers will be able to see the brightest planet, Venus, rising shortly after 3:30 a.m. below the stars of Aries. Venus will be over seven times brighter than Jupiter. A thin waning crescent moon will be to the left of Venus on the night of the solstice. See the second star chart below.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com