June 30 is supposed to be Asteroid Day, in commemoration of the Tunguska Event of 1908 June 30. That was when a small asteroid exploded over the Stony Tunguska River in Siberia, flattening the forest over an area of nearly a million square miles – the largest impact in recorded history.
I’m eleven years late in recognizing the Tunguska centenary (let’s hope the next Near-Earth Object that’s due to strike will also be tardy). I came to the note in my calendar this morning and bethought me of the asteroids, on which I haven’t worked for a couple of years. So I had to get some programs back into working order, making me another half day late. Here is what the first two asteroids, Ceres and Pallas, are doing.
See the end note about enlarging illustrations.
The loops in their paths are because of their apparent backward motion as Earth overtakes them on the inside.
Ceres and Pallas happen to be traveling roughly in parallel, Ceres somewhat farther out – they often remain in company like this for a while, both having periods of about 4.6 years. So they were at opposition on May 28 and May 4 respectively, both around right ascension 16 hours. But whereas Ceres, with its fairly flat orbit, is hugging the southerly Scorpius part of the ecliptic, Pallas with its remarkably high orbital inclination of 35° has climbed to as much as 44° north of Ceres.
Ceres and Pallas are the largest and first discovered of asteroids (Ceres now classified also as a dwarf planet). Ceres is at a magnitude of about 8, and Pallas about 9, and their dots in the pictures are comparable with stars of the same brightness.
Asteroid 3 Juno was at opposition in February. 4 Vesta will come to opposition in November, as usual the brightest of the year, at magnitude 6.5 – not, as it can, quite reaching naked-eye visibility, because in the outer part of its orbit.
__________
ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image”, then enlarge. Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers). I am grateful to know of what methods work for you.
I love following the brighter asteroids through binoculars. Unlike a fuzzy comet, an asteroid’s starlike appearance cuts through urban light pollution. Locating an asteroid takes enough time and effort to provide a sense of accomplishment, but not so much as to be overly frustrating. I usually need a couple of nights to find the right field and get oriented to the stars. Then there’s the first tentative identification and a rough sketch, hopefully followed the next night (or the next clear night!) by a positive identification — one of those “stars” moved relative to the others! After a few observations the asteroid starts to become a familiar friend. It really is surprising how quickly they move relative to the fixed stars, and they brighten and dim dramatically before and after opposition.
I hope you’ll provide a chart for Vesta soon. Here at 38 degrees north latitude she’s already 20 degrees above the horizon at astronomical dawn, shining at eighth magnitude. I could use sky safari on my ipad, but I find a paper chart and a red flashlight easier to use, and more pleasant.
Under Windows 10 a right click and Copy Image followed by opening it in Irfanview, pressing Enter followed by prt sc and closing Irfanview and reopening Irfanview with a second ctrl-V gives me the size I want 1902×1080 with a black border meeting my need for a wallpaper. Thanks for labeling x-y coordinates on all four sides, as well as other included information..