Dent County Astronomers

We'll have another nice fly-by of the International Space Station early this evening. It's so early, the sky will be twilight. This pass starts at 5:33 pm low in the northwestern skies. By 5:35, you should be able to see it rising in the sky and brightening (as it gets closer to us). A little after 5:36, the ISS will be just above Polaris (probably too dim to see) in the north. Before 5:37, it cuts through Cassiopeia. By 5:38 it will be dimming and dropping in the sky as it p...asses to the left of Mars. If you have a clear horizon to the southeast, you might see the ISS disappear into our shadow just before 5:41. The weather forecast predicts some clouds in the afternoon, but clear skies for the ISS pass. There's only one more evening pass of the ISS for us in 2020 and early forecast is poor for that night. So tonight's pass might be the end of the year for our evening ISS viewing.

Tonight (Monday 12/7/2020) we'll have a chance to see an excellent pass of the International Space Station around 6:20 pm. We'll only have a few more good passes in 2020, so try to catch this one. The pass starts in the northwest. You should see the ISS moving upward from the horizon between 6:21 and 6:23. It will pass by the bright star Vega just after 6:23 as it moves higher and to the southeast. Just before 6:24 it will pass by the bright star Deneb. The ISS will be nearly... overhead and very bright at 6:24:24. After that, the ISS will continue toward the planet Mars. It will pass close to Mars just after 6:25. Just seconds after it glides past Mars, the ISS will disappear into our shadow. The current weather forecast is for great viewing weather. Some viewers might see the ISS pass directly in front of (occult) Mars. You should also notice the closeness of the planets Saturn and Jupiter low in the southwest. We'll have updates on the upcoming Grand Conjunction later in December.

By this time of year, we often hear people commenting, "It's getting dark earlier and earlier." That has been true. But we're already at the earliest sunsets of the year. In a few days, our sunsets (Dent County and neighbors) will start seeing _later_ sunsets. Earthsky covers the issue in more detail. But the short version is that we had our earliest sunset of 2020 on December 1st -- 4:55 pm. And we'll keep having 4:55 pm sunsets through the 10th.... After that, the sunsets will slowly get later (until July 22). https://earthsky.org/earth/winter-solstice-and-late-sunrise

For our October, 2020 Wallpaper of the Month, we're offering a Halloween-related image -- the "Witch's Broom Nebula". This image was captured and processed by Ben Decker, in Florissant, MO, on June 13, 2020. The nebula is part of a large group of gas and dust clouds left over from a supernova sometime between 10,000 and 20,000 years ago. This object is also known as "NGC 6960" from William Herschel's catalog of sky objects. He discovered this object in 1784. Another descripti...ve name is the "Western Veil". The group of nebulae are known as the "Veil Nebula" (or "...Complex"). NGC 6960 is the westernmost object. The bright star is visible in the constellation Cygnus. Ben took 64 5-minute exposures using a telescope with a 60mm wide lens. The camera was a ZWO ASI 178MC. He used a light pollution filter to provide good contrast despite heavy St. Louis-area light pollution. #DCAWallpaper

We're currently in a lull in our current (poor quality) sequence of International Space Station passes. The Geminid meteor shower is a few weeks away. And the Grand Conjunction of our solar system's biggest planets a farther than that. The only current astronomy fodder is the curious (but not unprecedented) visit from an "asteroid" that's really human-made. You'll probably hear more about this object -- 2020SO -- in the news. Here are a few points:... 1) You just can't pop outside and see it. (It's way too dim.) 2) It won't hit us. (So don't bother wearing a hardhat.) 3) It's probably leaving near spring 2021. So even our bottom-of-the-barrel sky entertainment is rife with disappointment and under-achievement. Thanks, 2020.

Tonight (Thursday, 10/8) is the last night the ISS will be flying overhead during the evening for a while. The pass looks like it would be a very nice farewell showing of the ISS -- with a unique finale. Unfortunately, the weather forecasts are unanimously pessimistic for any viewing in Dent County and several other neighbors. Normally, we'd just skip the alert and await the next pass. But we do have followers outside our corner of the Ozarks. So this alert is really for all... people NOT in Dent County. (And, of course, weather forecasts can be wrong. Just sayin'.) This pass starts like many recent passes -- in the northwest. You might see it about 7:37pm in the twilight. At 7:38 it will pass near the bright star Arcturus as it moves toward the south. Its brightest point will be at 7:40, moderately high in the southwest sky. The most interesting part of this pass will be seconds before 7:41 when the ISS passes very near Jupiter in the south. If you aim a telescope or binoculars at Jupiter, you'll see the ISS fly by. (Don't blink!) For SOME lucky viewers, the ISS will be pass in front of ("transit") Jupiter. The ground map photo shows the calculated line of locations for viewing the transit. After the rendezvous with Jupiter, the ISS continues toward the SSE and winks out at 7:42:29. We'll start issuing more ISS fly-over alerts when the next evening sequence starts in mid-November.

We're in the home stretch of this sequence of evening ISS passes. The weather has been pretty good for some recent passes and the forecast for the Tuesday (10/6) night pass is excellent. This one is a keeper and a good choice for family viewing. The ISS will start in the northwest about 7:35 pm. If you can see the Big Dipper in the twilight, you can find the ISS moving through the handle at 7:36. By 7:38, the ISS will be rising and brightening as it glides toward the southeas...t. As the ISS approaches the southeast horizon it will dim steadily. A little before 7:41, the ISS will disappear into our shadow. On this pass, the ISS ground track will be very close to St. Louis. At the closest approach to our area, the ISS will be 288 miles away. The final evening pass of this sequence isn't especially bright, but it has an appealing feature: The path of the ISS will appear very close to Jupiter. At some locations in our area, the ISS will actually pass in front of Jupiter for an instant. We'll have more details for you about that soon.

We don't normally double-up on posts, but we have to strike while the iron's hot. In addition to the Mars close approach, we'll enjoy a very nice ISS pass Monday night (10/5). It's a quick one, but bright. You should be able to see the ISS about 8:23 in the northwest. Look behind the Big Dipper. It will rise toward the zenith, heading toward the southeast. Just after 8:25, it will approach the Summer Triangle (the bright stars Vega, Deneb and Altair). Just as it gets very hig...h and very bright, it will suddenly disappear into our shadow at 8:25:33. We'll have two more ISS passes for this sequence on the 6th and 8th. (updated)

On October 6th, Earth and Mars will make a "closest approach". We've been catching up to Mars in its larger orbit and. We've debunked some other articles about "opposition" and "closest approach" for the large planets -- Jupiter, Saturn, Uranus and Neptune. For those planets, the difference in visible size between the closest distance and farthest distance isn't much. That's because they're ALWAYS far from us. So those planets don't look that different to us. Mars is differe...nt. Mars gets (relatively) close and substantially far. And the planet so small that even when it's close, it looks smaller than Jupiter and Saturn. So for Mars, there's a short season when it looks its largest and a much longer season while it looks tiny. October 6 will offer the largest view. But any night in the next couple of weeks will be a great night for viewing the large appearance of Mars. Our next chance comes in 2022. This NASA article covers more details about the upcoming closest approach and the opposition (alignment of Mars, Earth and the Sun). If you have a telescope, THIS is the time to enjoy a view of Mars. While you're at it, you can catch Jupiter, Saturn, Neptune and Uranus in our night skies. https://mars.nasa.gov/all-about-m/night-sky/close-approach/