Halloween Fireballs

I don't know about the world where you live, but here in Iowa we have entered one of my favorite times of year. The air is finally cool and dry, and the leaves crunch underfoot. The fields are busy with harvesting activity, the woods are painted with the colors of autumn, and the skies contain large Vs of migrating geese. And for some bizarre reason, the local lilacs decided to bloom twice this year.

In the evening sky, the Milky Way is standing up straight and arching majestically from horizon to horizon (at least for Northern Hemisphere viewers) while the summer constellations yield to the autumn constellations. This year, the two brightest planets are also decorating the evening sky, and providing bright markers of the zodiac.

Stars and Planets

Scorpius and Sagittarius are two of my favorite constellations. They are both bright and easy to recognize, and they mark an especially bright and beautiful part of the Milky Way. If you live near the Equator or in the Southern Hemisphere, you can continue to enjoy these constellations high in the sky for much of the year, but here in the Northern Hemisphere, Scorpius has now pretty much finished its showing for the year. Sagittarius is closely following it into the sunset, and won't last much longer. Overhead, the Summer Triangle is gradually shifting westward as well, and the Great Square of Pegasus is rising to take its place, along with the rest of the constellations of the Andromeda Story. (If you live near the Equator or in the Southern Hemisphere, the Summer Triangle and the Great Square will not be overhead, but will be lower in the northern sky.)

The next two months should also provide a nice view of planets in the evenings. Venus, the brilliant “Evening Star”, is decorating the sunset, and it will hover there over the sunsets for the next two months. It will not begin to descend back into the sunset until the end of November. (The official date of the “greatest elongation” is October 29. After that, it will start moving closer to the sun, but very slowly at first.) Jupiter and Saturn are currently in Capricorn, heading towards Sagittarius and towards Venus. Do you remember the Great Conjunction last year in December? Jupiter and Saturn were virtually touching in the sky, and the pair of them closely followed the sun into the sunset. They then passed the sun, they rose above the sunrises for awhile, and they have now almost completed a full synodic cycle. They have passed through almost a full circle around the sky, compared to the sun. They will continue to move closer to the sun during the next few months, and they will follow the sun into the sunsets again this coming December.

Today, Wednesday the 6^th, is the date of the new moon. This means that starting in a couple of days, the beautiful crescent moon will join the sunset scene. It will then march along the zodiac night by night, passing Venus, then Saturn, and then Jupiter in the coming week. If you want to find the zodiac in the sky, or if you just enjoy beautiful sunsets, I suggest going out to watch the sunsets and the early evening stars this weekend, or roughly from October 7-10.

While you're out there, search for the Milky Way. As I mentioned, it is standing up straight in the evening sky, passing from Sagittarius in the southwest, through Cygnus and the Summer Triangle overhead, to Cassiopeia and Perseus in the northeast. (That's for Northern Hemisphere viewers. The Milky Way will also stand up fairly straight in the evening sky for viewers elsewhere in the world, but a different portion will be high in the sky. For those lucky viewers in the Southern Hemisphere, the spectacular “Milky Way Core” will be high overhead, between Sagittarius and Scorpius. I really want to visit the southern hemisphere some time.)

As I was preparing the graphic for this newsletter, I also noticed a bright dot — brighter than any star in the sky, and almost as bright as Jupiter and Saturn — zooming across my screen. I didn't realize that the graphical software I was using could show the location of the International Space Station. (Incidentally, if you haven't heard of this software before, it's called Stellarium, and it's free.) The blurry line in the picture above marks the path it will take across the Iowa sky, on the evening of Sunday the 10th, at 6:56 PM, local time. Unfortunately, seeing the ISS is a little like seeing a cloud. It depends very much on your exact location and the exact time, so I can't tell you all where or when to look for it in your local sky. If you'd like to see where it is right now, you can consult NASA's tracking map, and if you'd like to find out when it will pass over you in the near future, you can consult their sightings page.

Meteor Showers

There are a few meteor showers coming up in October which might provide some pleasant mornings of meteor-watching, but I wouldn't expect any stunning spectacles. The first will be the Orionids, which are predicted to peak on the 20^th. The rates are mediocre, with maybe 10-20 per hour on a good night, and they are known for zooming across the sky very quickly. This means that your friends have no time to swing their heads around after you yell “meteor!”, but it also means that the meteors often leave trains — glowing trails that last for a second or two, and it also means that sometimes they explode in bright fireballs. Unfortunately, the non-fireball meteors also tend to be quite dim, and this year's shower coincides with the full moon, which will drown out most or all of them.

The next two are a pair of similar, related showers: The South Taurids and the North Taurids. The Taurids are unusual in that they don't have a sharp peak. Some showers have a very brief, sharp spike in activity, going from inactive to peak to inactive again within a matter of hours. The Taurids are spread across a couple of months. The rates are low, maybe 5 per hour, but the two Taurid showers overlap for about a month, raising the rate to maybe 10 per hour, and because they last so long, you can take your sweet time about viewing them. The Taurids also sometimes explode into fireballs, and their overlap period is centered very roughly on Halloween.

The Southern Taurids run from roughly September 10 to November 20. The Northern Taurids last from around October 20 to December 10. So the overlap period runs from roughly October 20 to November 20. If you want to watch for “Halloween Fireballs”, that is your window of opportunity. The new moon in that period will be November 4^th, and I suggest circling the dates on your calendar around that time. Taurus will be rising in the late evening, so your best bet might be to go out around midnight and recline facing east, or go out in the early hours of the morning and just lie flat and try to take in the whole sky.

That's it for this time. As always, please feel free to contact me with comments or questions.

Happy Observing!