Nigerian skies in 2017 – Part 3

Auspiciously, key comet sentinels forecast a flurry of activity this month, as luminous visitors take perihelion turns around the Sun—some radiating near the margins of naked-eye visibility.

Shanklin, for one, advises that “February could be a busy month, with the possibility of three periodic comets…[and] two in parabolic orbits visible in binoculars”.

This is comet-speak, for three recurring and two one-off apparitions— “periodic” meaning any comet that rounds the Sun repeatedly, at intervals of 200 years, or less.

Prime periodic visitors are: 2P/Encke; 45P/Honda-Mrkos-Pajdusakova (45P); and 41P/Tuttle-Giacobini-Kresak (41P). Having very short periods, all will return within a few years.

Still, it’s best you don’t put-off until tomorrow, the pleasure which, comet impresarios advise, await you over the next few weeks—and after.

The celestial equator rises virtually from our feet (714 km off the coast), into the expansive firmament—a precious vantage point, for viewing both the Northern and Southern skies.

Fifteen equatorial constellations provide a glittering celestial backdrop, as well as convenient points of reference, for locating astronomical events occurring in both Hemispheres.

I hope you’ve been consulting the Internet (as I’ve urged), to find out how and when to observe important exhibitions, including 45P—whose molecular carbon causes it to glow green.

Space Weather.Com projected that, between the 9th and 11th, the comet could possibly brighten to magnitude “6,” putting it “on the verge of naked-eye visibility”.

But, like Fela Anikulapo Kuti used to say, “There’s no need looking back”. Even if you miss 45P, the sky-watching future remains bright. And that’s more than just a play on words.

No less authority, than Seiichi Yoshida—Japan’s celebrated comet sentinel—projects that, in March and April, 41P/Tuttle-Giacobini-Kresak is expected to outshine 45P.

Yoshida’s famously reliable tables (in this case, “Visual Comets in the Future”), pegs 41P at magnitude “5” in March and says it could be accessible to the unaided eye, well into April.

Comet 2P/Encke is no match for 41P or 45P. But pundits believe this frequent visitor (every 3.3 years) could achieve binocular brightness, as it sails into our equatorial skies, in March.

Not infrequently, visitors with completely unfamiliar faces—non-periodic comets, on hyperbolic or parabolic trajectories—hail at the inner solar system.

Among these unscheduled alien arrivals is C/2015 V2 (Johnson). Johnson is expected to approach the Sun in June when, Shanklin believes, “it could reach around 5th magnitude”.

Comet Watch too, counsels that, prior to perihelion, the apparition “will be well placed for northern hemisphere observers,” starting in late evening, and “visible for the rest of the night”.

Meanwhile, Yoshida predicts that C/2015 ER61 (PanSTARRS)—another new cometary face—will join Johnson in July, at magnitude “6,” the former appearing over the horizon in the a.m.

Six is just inside the border of binocular visibility (except for eagle-eyed observers, in very dark environments). But when it comes to comets, you can’t always go by the numbers.

As Near-Earth Object specialist, Paul Chodas, told NASA, “a comet’s brightness is notoriously unpredictable”.

Proximity to the Sun’s searing heat, opens fissures, through which reflective volatiles are vented. These “outbursts” can, temporarily, render binocular objects viewable without aids.

Naked-eye prospects are rather bleak, from August onward, Yoshida projects, with comet Johnson dimmed to “7” and PanSTARRS to “9”. Henceforth, it’s binoculars or bust!

Departing periodic visitors routinely strew dust and pebble along their orbital paths. Earth, perforce, plows into this ejecta, producing pyrotechnic displays called “meteor showers”.

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