Friday, April 19, 2024

What Will We See in the Sky During Totality? – Sky & Telescope

AstronomyWhat Will We See in the Sky During Totality? - Sky & Telescope


Venus will be readily visible about 10 minutes before total eclipse on April 8th, with Jupiter obvious once the Sun is covered. This view faces south from Little Rock, Arkansas, during totality.
Stellarium with additions by Diana Hannikainen

Totality is so precious no one will fault you if you don’t bother or even forget to hunt for planets and stars during the April eclipse. After all, the Sun and Moon are the celebrities of this show. Millions of us will drive, fly, and sail hundreds or even thousands of miles to directly experience what it feels like to be a cog in the grand cycling of heavenly bodies.

I can’t wait to feel that emotional cocktail of terror and reverence as the Moon’s shadow descends and then moments later to gaze agog at the Sun’s spiky, subatomic hairdo. But I also plan to spend at least a few seconds taking in the planets. I want to see with my own eyes the heliocentric nature of the solar system — a rare sight if you think about it.

For those who will only get a minute or two of totality by all means keep your focus on the Sun and absorb the vibe of night at midday. But if you’re lucky enough to get a bit more, consider a commando-style stargazing session. Get in — look — get out.

A number of bright wintertime stars along with a bevy of planets — Venus, Jupiter, Mars, and Saturn — will be visible from many locations along the path of totality. Venus gleams brightest at –3.8 magnitude. You’ll spot it 15° southwest of the Sun about 10 minutes before totality in the darkening sky. During total eclipse it will be unmistakable. Jupiter will pop into view about twice as far from the silhouetted disk of the new Moon in the opposite direction to the northeast. If that’s all you have time for, great. Two planets straddling either side of the Sun clearly advertise its primacy at the center of things.

Totality sky, Dallas, TX
This all-sky map displays the bright planets, stars, and subtly sunlit horizon observers will likely see during totality from the Dallas area.
Stellarium with additions by Diana Hannikainen

Mars and Saturn, shining at magnitudes 1.2 and 1.1, respectively, will be more challenging, but it helps that both lie a healthy distance (some 35°) southwest of the Sun. To find them, shoot a line from the eclipsed Sun through Venus a little more than one Sun-Venus separation to the southwest. We’re very lucky that the two outer planets happen to be near conjunction and just 1.5° apart. Find one and it will take little effort to spot the other.

The map above depicts the sky for the Dallas, Texas, region. Here are several other all-sky views from additional locations along the eclipse path:

After you’ve gotten a taste of the planets you can return to the solar spectacle. Or you can spend a few more seconds hunting down wintertime heavyweights like Rigel (magnitude +0.1), Betelgeuse (currently +0.8), Aldebaran (+0.9), Capella (+0.1), and — if you’re located along the path’s northeastern end — Sirius (–1.5).

The umbrella effect

Is there more to see? Yes! There’s the sky itself. While the corona contributes the equivalent of a full Moon’s worth of light to the darkened sky, sunlight reflecting off the atmosphere brightens it further, illuminating the surroundings like twilight does 30 to 40 minutes after sunset. To fully appreciate the lunar umbra’s umbrella-like effect, do a slow 360° spin to take in the bright ring of sunset-tinted light along the horizon. Here we peer beyond the shadow’s edge into nearby locales where the Sun shines in partial eclipse.

I’m often asked if Comet 12P/Pons-Brooks will be visible during totality. While each eclipse is different and distance from the Sun plays a role, seeing 2nd-magnitude stars and planets is typically hit-and-miss. I found no naked-eye observations of Mars during the 2017 eclipse when the 1.8-magnitude planet stood 8° from the Sun. During the same eclipse 1st-magnitude Regulus hovered only about a degree from the solar limb. Some observers saw it without optical aid, some didn’t.

Comet wild card

Totality with Comet 12P
Jupiter points to Comet 12P/Pons-Brooks on April 8th as viewed facing south from Austin, Texas. The comet should reach magnitude 4.5 on eclipse day.
Stellarium with additions by Bob King

Unless the comet has a surprise outburst, which appears unlikely at this stage, it will be 4th magnitude at best and invisible without some kind of optical aid. If you’re using a pair of 50-mm binoculars to observe solar prominences during totality, why not take a moment to swing by Jupiter and use the planet to guide you to the comet.

Sun and stars August 2017
Amateur astronomer Bobby Guidry of Anchorage, Alaska, recorded at least four stars — one as faint as 7th magnitude — during totality on August 21, 2017. Some might be invisible in this low-resolution image, but they’re all plain in the original. He used a 300-mm telephoto at f/8, ISO 400 and a 1-second exposure.
Bobby Guidry

Imaging the comet shouldn’t pose a problem. I base that opinion on photos taken during totality in 2017, some of which recorded stars in the vicinity of the Sun down to 8th magnitude! Amateur astronomer Bobby Guidry not only captured Regulus at magnitude 1.4 but also Nu Leonis (magnitude 5.3), 34 Leonis (6.4), and even HD 87647 (7.4). Mind you that all of the stars were within 2.5° of the eclipsed Sun!

Even though the comet’s head will be fuzzy compared to a star, its greater solar elongation and considerably brighter magnitude should make it a straightforward catch in a short time-exposure. While there’s just one eclipse it thrills me to know that it will be experienced and felt in myriad ways. Clear weather to all of you!


Read more about April’s total solar eclipse in a special Sky & Telescope publication (click here for readers outside the U.S.) dedicated to the event.



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