Planetarium Newsletter - June 2018

Cosmic Curiosities

“Let freedom reign. The Sun never set on so glorious a human achievement.”
~ Nelson Mandela, South African Lawyer & Leader

Colorful Full Moon in June

moon sequence

June’s full Moon actually looks as colorful as some of its names, like the Strawberry Moon or the Honey Moon. 

Near the summer solstice, the full Moon takes its lowest path across the southern sky. This shallow arc means the moonlight has to travel through more of the Earth’s atmosphere. The increase in air filters out all the colors of the Moon’s spectrum except the oranges and yellows -- the same reason why sunsets and sunrises are so colorful.

A full Moon is always opposite the Sun.  So, if the full Moon's path is low and short in summer, the Sun makes a high, long arc in June. In winter, it’s reversed; the Sun’s journey is  low and daylight is minimal. Meanwhile, the full Moon takes a long, lofty trek across the night sky.

moon sun path chartThis June, the full Moon arrives on the night of June 27-28. Besides turning various shades of orange-yellow, this Moon has some rather colorful names. Many monthly moon names refer to what is happening in nature or what is important for a particular culture. “Strawberry Moon” has been a popular one lately -- the Farmers’ Almanac mentions the Algonquin Native Americans as the source. June is a time to gather the ripening fruit of wild strawberries, so the name makes sense. But the most popular Moon name is probably “The Harvest Moon.” June’s Moon is also called the Honey Moon, the Rose Moon, and Fish Spoils Easily Moon. 


Not So Dark

On the summer solstice, people tend to say, “It’s the longest day of the year.” But to get technical, we experience the longest day in November -- on the first Sunday -- when we “fall back” as we switch our clocks to standard time. Thus, we experience a 25-hour day! Days can get even longer when we travel west a few time zones.  

What people mean, of course, is the summer solstice marks the longest amount of daylight. As the solstice approaches, we in the north revel under the expansive sunlight. 

earth at midnight in june   earth at midnight in december

Look at the two pictures above. Even at midnight on June 21, we are not far from the Sun’s light. People near the Arctic Circle experience no darkness. They have perpetual sunlight for 24 hours, for days straight, depending on where they live. Serious stargazers usually frown a bit with all this extra sunlight!

Here in southern Wisconsin, we get 8 hours and 37 minutes of nighttime. Sunset is at 8:35 p.m. CDT and sunrise is at 5:12 a.m. CDT.  Plenty of dark here to see the stars, right? Well, no, not really.

Twilight phases

Let me introduce you to the “three twilights” — civil, nautical, and astronomical.

  1. Civil twilight goes from sunset or sunrise to the time our star is six degrees below the horizon. It’s still fairly bright outside. Planets like Venus and Jupiter can be seen, along with the brightest stars like Sirius, Arcturus, or Vega. Some countries use civil twilight to make laws related to planes and street lighting.
  2. Nautical twilight is when the Sun is between six and 12 degrees below the horizon. This is when we start turning on our electric lights. It dates back to when sailors steered by the stars, as most of them could be seen. The U.S. military still uses this twilight to plan tactical operations.
  3. Astronomical twilight means dark-dark. The Sun is now 18 degrees below the horizon. If one is far from streetlights, you can see all the stars visible to the naked eye—over 1,000 distant suns, depending on the season and the time of night. This is time astronomers crave and need.

In the Milwaukee area, we only have four hours of true night. Astronomical twilight ends at 10:54 p.m. CDT and starts again at 2:54 a.m. CDT. As the short night slowly brightens again, you can often hear the birds chirping as if announcing a new day. 

After a Planetarium program this time of year, it’s always a bit strange to tell the younger school children to go out and stargaze or look at the Moon—when their bedtimes are probably before the sunset! 


Sun Probe Parker

sun probe

Get too close to the Sun and you incinerate! But NASA isn’t going to let that happen with the Parker Solar Probe. Launching in late July or August 2018, this spacecraft is built to be both delicate and tough. It has to be, as it will plunge to within 4 million miles of the Sun's surface. Parker will experience a star’s blistering radiation like no spaceship ever has.

Though the Sun seems amazingly stable, it’s not. There is a constant churning of energy taking place. One immense event is a coronal mass ejection, or CME. During solar maximum there can be three of these blasts in a day. When they occur, billions of tiny charged particles are ejected at ferocious speeds into space. If the CME is aimed at the Earth, then look up—or look out!

Look up when the solar particles produce the gorgeous aurora at the very top of our atmosphere. These northern or southern lights are often a shimmering green as the oxygen and nitrogen gases are bombarded by the Sun’s plasma.

cme earth interactions

Look out when these CME’s cause communication blackouts or shutdown an entire electrical grid. Recall that there is an array of satellites that orbit the Earth. Exposed in the vacuum of space, they are vulnerable to this solar attack. A dysfunctional satellite could disrupt one of your daily electronic transmissions.

NASA’s Parker Solar Probe will help solar scientists better understand the Sun’s turbulent nature.  The probe is named after Eugene Parker, the S. Chandrasekhar Distinguished Service Professor Emeritus, Department of Astronomy and Astrophysics at the University of Chicago. Back in the 1950s, Parker coined the Sun’s continuous flow of energy “the solar wind.” This is the first NASA mission that has been named for a living individual. The launch window for the Parker probe is July 31 to August 19, 2018.

Sky Sights

June 14-17

Venus blazes away in the western sky all month, setting over two hours after sunset. Look for the Moon shining nearby on June 15-16. See if you can catch the much dimmer twin stars of Gemini, Pollux and Castor. 

Mercury might be glimpsed very low in the west-northwest in mid- to late June.  A good guide will be the young crescent Moon shining to its left on June 14.

night sky in june

Jupiter high in the south after sunset. The other twin stars in Libra, Zubenelgenubi and Zubeneschamal, can be seen by the patient stargazer. A waxing gibbous  Moon rolls through from June 22-24.

june 1-3 june 29-30

Mars keeps getting brighter as it closes in on late July’s brilliant opposition.  This June, it goes from magnitude -1.2 at the start to -2.2 by the end. Then, in July, the red planet will shine brighter than Jupiter—which can happen only once every 2.2 years. Mars rises around midnight on June 1 and by 10:30 p.m. on June 30. The  Moon orbits by twice this month on June 3 and 30.

june 26-28

Saturn reaches opposition on June 27—the same night as the full  Moon Observe them very close together—only one degree apart. The width of your thumb at arm’s length is 2 degrees. So go ahead and reach out that night and cover up part of our solar system. Look for the Moon nearby on June 1, too.

Star Map

Download the June Star Map. >> 

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