I started off our last club meeting by showing my “In the Sky” post I’d written the day before – hey… why not!? Several of the students said that they had seen Ursa Major, and a couple said they could see the Mizar/Alcor double star! This week’s constellation was Cassiopeia; I showed the students where to find the constellation, and some deep-sky objects in the Cassiopeia, including the open cluster M103.
The constellation Cassiopeia in the northwestern predawn sky on Oct. 1, 2019. Credit: Stellarium / Bob TrembleyI discussed the differences between open and globular star clusters, and showed a few examples of each.
We discussed galaxy mergers, and I showed this animation of galaxy mergers seen from different perspectives:
We then discussed how the Andromeda galaxy and the Milky Way will collide in several billion years; I showed this PBS video about the collision:
During the video, one of the students asked my wife “What is that band of stars behind the narrator?” I stopped the video, and brought up a photo of the Milky Way as seen from a dark sky site, and asked my students if any of them had ever seen this:
Time-exposure of the Milky Way from northern lower Michigan. Credit: Doug Bock (Twitter: Mars_1956).Of the 15 students in the club that day, only one had ever seen the Milky Way. I hung my head and sighed. I proceeded to show the students images of the structure of the Milky Way galaxy: top-down showing the spiral arms, and a side view showing the galaxy’s disk and bulge, and where the Sun is located.
Annotated artist’s concept of a top-down view of the Milky Way galaxy. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)
Edge-on spiral galaxy ESO 121-6. Credit: ESA/Hubble & NASASo here our solar system is, in the middle of this enormous flat disk of stars, gas and dust; from our viewpoint, that disk stretches completely us around in the sky, and looks like a silvery band. Unless you are far away in space, half of that band is hidden by the Earth. From the dawn of human civilization until about 100 years ago, every human on Earth could see the Milky Way, every night. What happened? Light pollution.
“… more than 80% of the world and more than 99% of the U.S. and European populations live under light-polluted skies. The Milky Way is hidden from more than one-third of humanity, including 60% of Europeans and nearly 80% of North Americans.” – The new world atlas of artificial night sky brightness
Light Pollution in the Chicago Skyline in 2012. Credit: Bob TrembleyFor the next several minutes, my wife and I discussed light pollution with the students, and we showed them nighttime images of Earth from NASA’s Black Marble site – the students gasped!
Midwest and Northeastern U.S. at night from NASA’s Black Marble website.My wife and I related the story of the 1994 power outage in Los Angeles where residents called observatories asking what the weird silvery band of light they were seeing in the sky… This story actually tells me two things: 1) those people have never seen the night sky from a dark sky site, and 2) those people didn’t know the Milky Way was there in the first place – which speaks volumes about the quality of basic astronomy education they’ve received.
In an odd bit of serendipity, the main presentation at the recent meeting of the Warren Astronomical Society was given by Dr. Sally Oey, Professor of Astronomy at the University of Michigan, about light pollution! Dr. Oey is involved with Michigan Dark Skies; I walked away with several pamphlets from the International Dark Sky Association. Dr. Oey told the audience that if they had a non-shielded streetlight near their home that they would like replaced to simply call DTE customer service. I’ve contacted them via Twitter and am having a conversation with support as I’m writing this.
Here’s what you’re missing:
