A classical music composer, two astronomers, and a patron saint walk into a bar...

 

Near the end of April, I was hunting for supernovae in galaxies at 14 hours of Right Ascension, and I saw in my planetarium software that a couple of minor planets were in the same field as NGC 5468. As is often my custom, I shot some pictures of the galaxy and moved on, planning to sort out the asteroids later with the assistance of the time filter. 

Following another one of my frequent customs, I then proceeded to forget all about the asteroids! But every now and then, I refresh my memory of recent minor planet targets by searching through my images and looking for asteroids that I added to the file names. If I find some that I never processed, I'll spend an hour, or so, putting together an animated GIF. And so, yesterday morning, I discovered the files containing the pair of forgotten planets with NGC 5468 and I went to work on them.

To my surprise, although NGC 5468 is a nice, face-on spiral galaxy (a good target galaxy for supernovae), it wasn't on my 14-hour targets list. And that means that I haven't shot it in many years. Once in 2016 and once in 2017, and that was with the old Starlight Xpress H9C one-shot color camera. On those two nights, I had taken just three images of NGC 5468, each of them 15 seconds long, for a total exposure of 45 seconds. However, there was enough signal there to use for a comparison image, and even though that camera's sensor array is different than my current camera (an Atik 460EX mono), I was able to use different zooms to make them close to the same size for a rough blink comparison. The blink was successful, and I spotted the two asteroids in the Atik images

After some research, I figured out which asteroid was which, and I made a non-blinking JPG, annotated with the two asteroids: (4326) McNally and (4527) Schoenberg. A blink comparison is more fun, so I added NGC 5468 to my 14-hour targets list and last night I shot the galaxy again as soon as the sky got dark. 

One thing I noted immediately was a plethora of satellites that were photobombing my images (see the animation below). Every image had at least one satellite streak, but most had 4, and a couple of them had 5. And this was within a period of 7 minutes, in a random 1-degree patch of sky. Of course, part of the problem is just the sheer bad luck of NGC 5468 being at a declination of -5°. That's the realm of the geostationary satellites, for those of us living in Tucson. But there were two other satellites that photobombed my sequence, and they were much closer to earth than the geostationary satellites. You can tell by the length of the trails. The shortest ones represent higher-altitude (slower moving) satellites. Could the longer streaks have been caused by Star Link satellites? Perhaps. Fortunately, since they aren't in the same position for each image, they all disappeared when the 12 images were stacked (using the median-combine algorithm in MaxIm DL) to become part of the GIF at the top of this page.

After disposing of the satellite streaks, the blinking of the two stacked images (one from April 28 and one from June 17) at the top of this page revealed not two but four minor planets! Two different pairs of minor planets on each night. Last night's pair were (260) Huberta and (3684) Berry. When these two asteroids were added to the list of minor planets I've imaged since 2007, my grand total comes to 402.

Minor planet (4527) Schoenberg is named for the classical composer Arnold Schönberg (1874 - 1951). I had never heard of him, but I listened to his Verklärte Nacht (Transfigured Night), by the Juliard String Quartet with Walter Trampler and Yo-Yo Ma (1992) on Apple Music, while I was putting these animated GIFs together. With all due respect to Schönberg, I must admit that I prefer classical music that was written prior to 1850. While listening to 20th century classical music like Schönberg's, I often feel like I'm being transfigured into David Byrne's "Psycho Killer" inside my brain. I feel like a much better person when I'm listening to Mozart's Nachtmusik.

On the other hand, (3684) Berry is much more in tune with my interests, without the need for transfiguration! Richard Berry is an amateur astronomer, author, telescope maker, and CCD camera builder, and one-time editor in chief of Astronomy magazine. At a time when CCD cameras became commercially available but were unaffordable, Berry's "Cookbook" camera kits provided the parts and schematics for tech-savvy amateur astronomers to make their own cameras on the cheap. These became quite popular, and many were used in supernova and asteroid hunting programs amongst amateur astronomers in the 1990s.

Minor planet (4326) McNally was named for astronomer and educator Derek McNally, who was once the director of the University of London Observatory. His research specialties were the modeling of star formation and interstellar spectroscopy. He served as the general secretary of the International Astronomical Union (IAU) from 1988-1991. The IAU is the organization that is responsible for giving the official names to the constellations, stars, major and minor planets, comets, and, yes, supernovae!

Lastly, (260) Huberta was named for St. Hubertus (656? - 727), the patron saint of hunters, which I like to think includes supernova hunters! When it was discovered in 1886, minor planets were typically named for goddesses or females. So "Hubertus" became "Huberta." According to one source, "Huberta was apparently named after Saint Hubertus, who, however, had to purchase his inclusion among the stars by changing the final syllable 'us' to 'a,' thus transforming him from a patron saint into a patroness of hunters."

Lest we should fail to see the forest for the trees here, I want to point out something about the numbering of minor planets that is, at once, both obvious and contradictory. Each of the four asteroids in my picture at the top of this page lies in the main asteroid belt between Mars and Jupiter. After their discovery, astronomers use observations of the asteroids to determine their orbits. They are then assigned a number that is in order of discovery. Thus, the very first asteroid that was discovered, Ceres, was officially dubbed "(1) Ceres." If you think about it, it kind of makes sense that the first couple hundred asteroids to be discovered must have been the brightest and most obvious ones in the Main Belt. A good number of asteroids were discovered before the advent of photography. It is generally true to say that the later their discovery, the fainter the asteroids. 

But what makes some asteroids brighter than others? There are three major factors: 1) close proximity to earth, 2) physical size of the asteroid, and 3) albedo, or reflectivity of the asteroid based on its composition.

If you apply these factors to the four asteroids I imaged here, you will find some contradictions. For instance, the brightest asteroid in the picture is (260) Huberta. So, you would think that it must be the closest one to us. In reality, (260) Huberta was the most distant asteroid on the nights when these images were taken. Thus, Huberta either has very good reflectivity or is very large compared to the others. Or perhaps it has a combination of good reflectivity and size. 

Similarly, (3684) Berry, the next number above (260) Huberta, should be the next brightest of the four. But it is the dimmest! Does that mean it's the furthest asteroid from us in this picture? No! It was actually tied with (4527) Schoenberg as the nearest asteroid to us! Therefore, these two must be either very tiny, or poor reflectors, or both, compared to the other two.

The second brightest asteroid in my animated GIF is (4326) McNally. It was also the second furthest asteroid from earth, out of the four in my picture. Not what I would have expected, given their numbers. 

One of the things that affects the relationship between the numbered order and the brightness of an asteroid is the shape of its orbit. Some of them have nearly round orbits and that means they'll have a fairly consistent brightness as we catch up with them and pass them on each orbit of the earth. But others have elliptical orbits that carry them far out, close to Jupiter's orbit, and then up close, near the orbit of Mars. These are tricky because they may have been discovered when they were closest to earth, but when we find them photobombing one of our pictures, they might be much further away and dimmer than they were at the time of discovery. Conversely, they may have been discovered when they were dim and further out, but then they may photobomb our pictures when they are closer and brighter.

We can assume that, in general, the lower an asteroid's number, the brighter it will be. That's why I made it a personal goal to take images of the first 100 numbered asteroids. That's a fun list. The first 100 asteroids are all fairly bright and stood out in my pictures very easily. All of them could have been seen in the eyepiece, too, but when you look in the eyepiece, you can't always tell which "star" is the asteroid. Most people suggest that if you want to look at asteroids through the eyepiece, you should make a sketch and then wait an hour and draw another sketch. You'll then be able to see which one of the stars moved, when you compare the two sketches. The only problem with this technique is that our sketching has to be extremely accurate, and not all of us are accurate sketchers! Even after sketching the field stars we saw, we may not be able to figure out which star moved. Sometimes they all moved, at least in my experience with sketching!