If you’ve heard about the November 11 Transit of Mercury (visible 6:39 AM – 11:04 AM, Mountain Standard
Time, here in Denver), you may have a simple question: “What is it, and why
is a transit a rare event?” The “what” is quick to answer; the “why” takes a
bit longer, but isn’t hard to understand.
During a transit of Mercury, we see Mercury’s silhouette
pass across the face of the Sun. It’s very much the same idea as a solar eclipse
(when the Moon passes in front of the Sun), except that Mercury is so much
farther away that it hardly covers the solar disk—all we see (through a telescope
set up for safe solar viewing) is the planet’s “little black dot” move across
the Sun over several hours.
If we could watch this event while looking down from a vantage high above our solar system, we’d see Mercury, the Earth, and the Sun arranged in a fairly straight line, with Mercury between the Earth and Sun (see Chart 1, below). Continue reading “The Mercury Transit Explained”
If you’re in the Denver area Tuesday,
October 8, 2019, get outside and look for the International Space Station (ISS)
just after 7:30 PM. We’ll have a brilliant, close pass as the ISS flies almost
directly overhead, about 250 miles above us.
If you’ve been reading my monthly column here for the last year, or for the last several years on the Denver Astronomical Society’s site, you might have noticed that I’ve taken a break…
Don’t worry–while the planets move across the sky from week to week, the stars keep more or less the same positions from each other year after year (you’d need some expensive astronomical instruments to tell the difference). That means that if you’re looking for good targets in August (or September, or October…), you can hit the Astronomical Society’s archived pages.
You’ll find four years of columns, from 2015 to 2019, so there will be four “Augusts” for you to peruse (and of course, four Septembers, and so on…). There’s enough material there for a book. (As it happens, I’m working on that right now!)
The archived PDF files from 2015 to the end of 2018 are linked HERE.
More recent, WordPress-based articles, from January 2019 to May 2019, are HERE. (I recently edited noted astronomy writer Jeff Kanipe’s article on observing in the Southern Hemisphere, “Five Nights in the Magellanic Clouds,” and you’ll find that there, too!)
Along with the planets this month, we’ve got two targets in the constellation Canes Venatici—one is a sun-like star, and the other a bright spiral galaxy. Let’s get going… Continue reading “May 2019 Skies”
In March, we have a relatively quiet month for planets: Most
of them are now early-morning objects, but they are at a greater angle from the
Sun, allowing better observing. In the “Stars and Deep Sky” section, we’ll look
at two stars in the constellation Cancer—the first is a wonderful binary, and
the other, a lesser-known carbon star.