This past week, an old friend (a verrrrrry old friend!) invited me out with him and his son to go out and explore Moab, Utah and the surrounding area: Arches National Park, Dead Horse State Park, and Canyonlands National Park. The geology of this part of the country was formed hundreds of millions of years ago when the entire area was under what is now known to be a giant inland sea. Over all that time, the water both formed and eroded the sandstone in gorgeous strata that uplifted at various angles to the rest of the ground. It was mostly the Colorado River just doing its thing, day after day, year after year, but also even the limited amount of rain that the desert gets, just constantly eating away at things.
The sandstone is rich in iron – well iron oxide, actually, which is rust. And it is this rust that gives those uplifted strata their glorious red color. This rust is the same reason that Mars is red. Add to that the strange light green colored plant life of the desert, and the combination is truly stunning.
And of course, since it’s literally out in the middle of nowhere, the skies are equally as glorious. Dead Horse and Canyonlands, being a bit further from the small town of Moab (and its pitifully small amount of light pollution) than Arches is, have been designated by the International Dark-Sky Association as International Dark Sky Parks – an area that is “an exceptional dark sky resource”. Or in other words, skies that are truly dark and unaffected by light pollution. Pretty much the opposite of what this blog is all about, but hey, ya gotta see the best to really know the worst, right?
And man, were the skies dark. They had to be easily sixth magnitude, although I didn’t check by determining what the dimmest star I could see was. However, that question may have been answered inadvertently anyway.
After literally an all-night drive from Denver, we arrived in Moab around 6am, but continued on for another half hour to Canyonlands to watch the sunrise from Mesa Arch. Unfortunately, this extra driving time cost us the opportunity to see the DSOs in the summer constellations that were dominating our view as we drove south – especially Sagittarius and Scorpius. Dawn came at about 7:30, but the pre-dawn light wiped out our chances to see any of the great stuff down that way.
Instead, we just looked at the moon and planets, which were still visible as the sun rose. I never, EVER observe in the early morning, so I got my first glimpse of Saturn for the year about four months early. Jupiter was riding high near the moon, and we took some time to explore those two as well. But with the rising sun, I didn’t get any chance to gauge the quality of the dark skies.
After three days of continous hiking and biking, including a 40-minute Bataan Death March up to the top of the mesa where the Delicate Arch is located, we took an evening out for astronomy. We had passed what we thought was a turnout off of the main road between The Needles part of Canyonlands on the way down to the day’s hiking, and pulled in there on the way back. We were roughly 20 miles south of our cabin, which itself was about 6 or 7 miles south of town, so we were deep into a very dark area – two shades darker on the dark sky map than the DAS Dark Site just north of Deer Trail, CO.
It turned out that that turnoff was actually a real through road that people used, getting from place to place, much to the chagrin of our ability to dark adapt and remain so. We were a good couple hundred yards off of the main road, and away from all the cars and their headlights, but every 15 minutes or so, another car would turn off and pass us by on this side road.
We got there just as the sun was setting, so I was able to set up in the dusk. Venus came out immediately, and I was able to catch a giant 4% crescent. Then we had to wait another good half hour or more until the sky got dark enough to do some serious observing, so we ate a well-deserved dinner after a full day of hiking. Finally, night descended and the stars came out en masse, forming one constellation after another. The sky was gorgeous. Ridiculously gorgeous. They say that under dark skies you’re capable of seeing 2000 stars, and they weren’t kidding. After seeing around 50 stars every night in Manhattan, and maybe about 200 or so here at home in Denver, this was really a treat. The sky was bespangled with stars.
Even greater than just looking up at the sky, of course, was the observing itself. I decided to show my friends a little bit of stellar evolution. I started out with the Orion Nebula – but still couldn’t see the Trapezium, unfortunately – and described the nature of cloud collapse leading to stellar formation. I moved onto the Pleiades, which is a cluster of young, hot, blue stars, with some nebulosity around them (although I understand from Phil Plait that the nebulosity there is not actually associated with the birth of those stars, but is just something that the moving cluster has happened to slam into). I pointed out the Hyades, the V-shaped cluster in Taurus next to Aldebaran. Then I moved on from there to the Double Cluster, which can be seen as being the ultimate expression of open cluster-dom.
While observing in that hour or so after sunset, we observed a couple of dim objects moving slowly across the sky. In fact, they were moving precisely north from the south – meaning that they were satellites, because airplanes just don’t travel in that direction. Satellites can generally be seen in the hour or two right after sunset or before sunrise. This is because, just as the light from a sunset hits the top of the mountains last, it hits objects that are even higher up even later than that.
This north-south path is relatively unusual, because most satellites are launched to travel west to east, to take advantage of the free speed boost that the rotation of the earth imparts to them in terms of boosting the rocket into space. This is why rockets are launched from Cape Canaveral, as opposed to, say, Acadia National Park in Maine – because the speed of the earth’s rotation increases the closer you get to the equator. It is also why the European Space Agency launches its rockets from the Guiana Space Center, only 5 degrees north of the equator. The rocket gets a free 1000 mph boost from the rotation of the earth there.
However, certain satellites are launched in a polar orbit – north and south. Checking with Stellarium, it looks like the Iridium satellites were moving in this north/south path, but from north to south – at least that night; the two we saw were moving the opposite way. One of the ones we saw might have been the WISE satellite, at just over 300 miles altitude and about magnitude 5.1 as it passed over.
Neato! The WISE is the Wide-Field Infrared Survey Explorer, a space observatory that observed 99% of the sky in the infrared over a course of ten months in 2010, until its coolant ran out. It studied asteroids, cool, dim stars such as brown dwarfs, and the most luminous infrared galaxies. Although WISE was unable to detect any Kuiper Belt Objects due to their being too cold, it was able to detect tens of thousands of new asteroids, including hundreds of near-earth objects. Even without its coolant, it was still a viable observatory, so in 2013, it was restarted with the mission of detecting even more asteroids, and continues to do so to this day.
However, we more likely saw Fengyun 3A, a Chinese satellite also moving south to north, but at magnitude 3.8 and 520 miles up. I say more likely due to that magnitude difference – they were both crossing over literally one right after another, within about a minute or two, and Fengyun is a lot brighter and more noticeable. Unfortunately, Fengyun is just a Chinese weather satellite, a lot less interesting than WISE. Boo hiss.
I then took them out to see the galaxies. First M81 and 82, which looked better than I had ever seen them before. M82 showed its distinct dust lane going across the center. This pair is the furthest away I’ve ever seen – 12 million light years. Then I decided to stretch out that distance by looking at the Leo Triplet – M65, 66, and NGC 3628. I could only see two of them, but they’re 35 million light years away. That’s halfway back to the dinosaurs and the asteroid impact that caused them to go extinct.
While showing them these galaxies, the question came up as to how we are able to know these distances in the first place. I explained the concepts of parallax, absolute brightness, and red shift. I related to them the story of how Hubble – the dude, not the scope – was able to photograph certain types of stars in the Andromeda Galaxy for the first time in the 1920s with the 100-inch telescope at Mt. Wilson. He recognized these stars as being Cepheid variables. By using the parallax created by the width of the earth’s orbit, the distances to a few of the closer of these Cepheids in our galaxies was already known, making them “standard candles” for determining how far away other things were. So, if you saw a Cepheid variable of, say, 13th magnitude in a star cluster, you could calculate the absolute magnitude of that star, and therefore the distance to that cluster.
Detecting the Cepheids in Andromeda in 1923 allowed Hubble to calculate their absolute brightness and therefore the distance to Andromeda. Hubble discovered that what was then called the Andromeda Nebula was actually outside of our own galaxy, and therefore was a galaxy itself. These findings were then repeated with other nearby galaxies to determine their distances as well.
This information was then compared to the red shift of these other galaxies. Red shift is the change in position toward the red of the absorption lines in the spectra of objects as they move away from us. A correlation was found – the farther away a galaxy was from us, the larger the red shift they found. Even though we could no longer detect Cepheid variables in galaxies beyond a certain distance, we could still calculate their distance based on their red shift away from us.
My friends complimented my explaining skills. That is, until I moved on to show them a couple of globular clusters, M3 and M53. They then stumped me by asking why globular clusters don’t collapse in on themselves. I had to look that one up. (It’s because the millions of stars all rotate every which way, and not in the same plane or direction. This counter-rotation creates a counter-pressure to the gravity that would otherwise tug them in towards the center.)
Finally, as Jupiter rose higher into the sky, I saw something visually to its northwest – a giant patch of dim stars. What the heck was that?!? I was so disbelieving what I was seeing that I actually asked them if they saw it too, because I had no idea what I was looking at.
It turned out to be Melotte 111, otherwise known as the Coma Berenices Cluster. This is a huge open cluster, obviously in the constellation Coma Berenices – meaning Queen Berenice’s hair, one of the dimmer and least remarkable constellations up there. Mel 111 is so large that it doesn’t even have a Messier or NGC designation. It’s about 5 degrees across, with a scattering of 5th and 6th magnitude stars, and is about 290 light years away, in between the distance of the Hyades at 150 l.y., and the Pleiades at 440 l.y. This was a cluster I’d never even heard of, let alone seen before. In fact, it was impossible for me to see it from either Long Island, where I grew up, or from Manhattan, or Denver.
I always find it astounding to “discover” something new like this – some object up there that I had no idea existed before. It’s like discovering it for the first time for me. I had this same thing happen to me 2 1/2 years ago when I got back into astronomy and “discovered” the Double Cluster, which I had no idea existed before as a kid.
A good time was had by all, especially me, as my friends seemed to be unsuited to the cooler temperatures of the high desert at night, and froze their butts off. Now, if only to get out there with a 9.25″ scope, and to be further away from road and its lights. That would really be something!
Light-Polluted Astronomy 
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