Girl Scout Star-Gazer Badges

This last Monday, December 15, 2025, I was able to help the 10 third grade girls of Troop 56655 of Villa Park/Lombard, IL get their sky-gazer badges. My grand-daughter, Emily, is in the troop and she was to make a presentation about the Moon but unfortunately she had a bad bout with flu and couldn’t give her presentation. My daughter, Christine filled in for her and I added some information about star constellations and finding the North Star.

The night started with an excellent presentation from Sophia, another girl in the troop, about the characteristics of the planets. They were aware that Pluto is not a planet anymore but a dwarf planet. I shared that Pluto is still my favorite, especially since it was discovered on my birth date of February 18.

The girls also learned the linear layout size of the Solar System, where the 4 inner planets of Mercury, Venus, Earth and Mars are all relatively close to the Sun, then come the gas giants of Jupiter and Saturn and finally the ice giants of Uranus and Neptune. The girls all showed much restraint when the two pronunciations of Uranus were uttered.

Then it was our turn to talk about the Moon. Here are the pictures and comments from Emily’s presentation.

The moon is the brightest object in the night sky. The Earth is 4 times larger in diameter than the Moon. Diameter is the distance across a circle.

The Moon and the Sun have the same apparent size in the sky. That is why the moon can exactly block the Sun during a solar eclipse. But the Sun is actually 400 times the size of the Moon, but because the Sun is also 400 times farther from Earth than the Moon, they both appear to be 1/2 of a degree in size in the sky.

To define what a degree of size is, there are 360 degrees in a circle. When you are outside looking for stars, there are 180 degrees from horizon to horizon, exacting half of a full circle. The point directly above you in the sky, is called the zenith. The zenith is 90 degrees above the horizon. To measure sizes in sky you can use parts of your hand at arm’s distance.

Your fist at arm’s distance is 10 degrees across. If you alternately place one fist and then another above the first, starting at the horizon, you should get 9 fists, or 90 degrees when you reach the zenith. The Girl Scout sign with 3 fingers is 5 degrees in size and the width of your pinkie finger is 1 degree. The Moon is only half the width of your pinkie finger or 1/2 a degree.

The Moon moves from Moonrise in the East to Moonset in the West in 12 hours due to the Earth’s rotation. As the moon orbits the Earth, it moves its own diameter each hour toward the East relative to the stars. The orbital movement is why the Moon rises approximately 50 minutes later each day.

The Moon goes thru phases or different amounts of its disc being bright, every 29.5 days. The time span between the same Moon phase is where we get our month from.

New Moon is when the Moon’s disk is completely dark. Next is the 1st Quarter Moon when the right hand side of the moon is illuminated (for us in the Northern Hemisphere). It is called 1st Quarter, even though is half illuminated, because the Moon is a quarter thru its phase cycle. 1st Quarter is followed by the Full Moon, where it is fully illuminated. The last phase is Last Quarter where the left hand side is illuminated. Then you are back to New Moon and the cycle begins again. The time between each of these 4 major phases is about a week.

If the illuminated part of the Moon is increasing, that is called “waxing”. The time between New Moon and Full Moon is the waxing part of the Moon’s cycle. If the illuminated part is decreasing, that is called “waning” The time between Full Moon and New Moon is the waning part of the cycle. If the illuminated part is less than half the Moon’s disk, it is called a “crescent”. The girls referred to this stage as the “banana”, “smiley-face or “toe-nail” moon. If the lit part is more than half the disk, it is called a “gibbous” moon.

We then did a demonstration with the girls huddled in the center representing observers on the Earth and my daughter circled them with a white Styrofoam ball (the moon) and I played the Sun by shining a flashlight on the ball to show the girls that they see different amounts of the ball lit up.

Because the Moon orbits the Earth in the same 29.5 days that it rotates, it always shows the same side of the Moon to us on the Earth. This equality between the orbit and rotation period of the moon, means the Moon is “tidally locked” to the Earth. A day on the moon takes 29.5 days, so you get 2 weeks of daylight and then 2 weeks of night. Objects in the daylight on the Moon can reach 250 degrees Fahrenheit and objects in the shadows can drop to a minus 250 degrees. The 14 days of night can be a problem for any equipment that is solar powered. That is why all of the 6 Apollo stays on the Moon occurred during the daylight period.

The Earth is 4.5 billion years old. Soon after the Earth formed it was hit by a Mars-sized object that scientists call Theia. The collision threw a lot of melted rock into orbit around the Earth. The rock quickly condensed into the Moon. The Moon formed much closer to the Earth than it is now and continues to drift 1.5 inches farther each year.

The dark parts of the Moon are called Mare (or seas). They are made from dark lava. The “Poodle-on-the-moon” is made from several of these dark mare. The Apollo 11 landing site is at the lower part of the Poodle’s chest. The landing site was in the Sea of Tranquility or Mare Tranquillitatis (if you like the Latin term). There are more mare on the visible side of the moon than the far side. We demonstrated that with a moon globe we brought with us. We asked the girls if they could find the “Poodle” on the globe.

Next, I was up to show the girls some constellations. I demonstrated my green laser pen which is a great tool for showing people objects in the sky because it draws a line that people can follow to the object of interest in the sky. You just have to make sure you don’t point it at any airplanes or you could get a visit from law enforcement. Unfortunately the skies were cloudy, so we couldn’t look at any real stars.

But I did tell the girls there were 88 constellations. Astronomers decided in 1928 to carve up the entire sky with those constellations, so there wouldn’t be any confusion on which constellation a sky object belonged to. We’ve got bears (Ursa Major and Minor), a lion (Leo), a winged horse (Pegasus), dogs (Canis Major and Minor) and even a unicorn (Monoceros). Some of the constellations are thousands of years old and the ancients had quite an imagination. Canis Minor consists of only 2 eye visible stars. One of my favorites, it the bright stars of Orion, the Hunter. I showed the girls my cardboard “The Night Sky” display. With it you dial in the time of the night and the day of the year and it will show the visible constellations. Because the stars rise 4 minutes earlier each night, due to the orbit of the Earth around the Sun, you have different constellation during the seasons of the year. It is about the worst time of year to try to find the Big Dipper because it is very low in the sky, just about on the Northern Horizon.

I also showed the girls how to find the North Star, Polaris, using the 2 outer stars of the Big Dipper’s bowl. The North Star is at the end of the Little Dipper’s handle. It is probably the most useful star because you will always know your directions if you can locate it. The North Star is the only star that doesn’t move during the night. All the other stars rotate around it. If you face it, you will be facing North, with East on your right and West on your left and South to your back. For us in Villa Park, IL, the North Star will be 42 degrees or about half way up from the horizon to the zenith. That is because our city is 42 degrees north latitude. If you were on the equator, the North Star would be on the horizon and if you are at the North Pole it would be at the zenith. The Big and Little Dippers are known as asterisms. An asterism is a useful part, many times a geometric shape, of a constellation. The constellations for the Dippers are Ursa Major and Minor or Big and Little Bear. Other asterisms are the Great Square of Pegasus or the Summer Triangle which is composed of the brightest stars from 3 constellations, Vega in Lyra (the Harp), Deneb in Cygnus (the Swan) and Altair in Aquilla (the Eagle).

It was a great 2 hour meeting and the girls seemed to absorb all the great astronomical information. I found it very rewarding and appreciate the opportunity to share my knowledge with them.