Our Guide to This Month’s Total Solar Eclipse Over South America

2020 closes out with the final total solar eclipse of the decade, as totality crosses the southern tip of South America on December 14th.

Did you happen to catch last Monday’s slight penumbral lunar eclipse? Sure, a penumbral may be the most anti-climatic of all of the varieties of eclipses… but this event also sets us up for the ultimate in astronomical events, as a total solar eclipse crosses South America on December 14th, 2020.

This bookends the final eclipse season for the decade, though totality will only briefly span a 90-kilometer wide swath from Chile to Argentina.

The footprint for the December 14th eclipse, with times for totality and percentages for partial phases. Credit: Michael Zeiler/Atlas of Solar Eclipses: 2020 to 2045.

Eclipse-Chasing, in a Time of Covid19

This comes as many an eclipse-chaser has had to curtail their travel plans, due to the ongoing worldwide pandemic. The path even misses the major cities in Chile and Argentina as it vaults up over the Andes mountains, gracing only a few small villages as it crosses from the Pacific to the Atlantic Coast of South America in about 20 minutes. The path of totality passes over several active volcanoes (including Villarrica in Chile) making for several intriguing photogenic possibilities. Clear sky prospects are best in Patagonia in central Argentina, and cloud chances increase towards the Chilean border to the west, and the Argentinean Atlantic coast to the east.

As of writing this, we haven’t seen any planned effort(s) to livecast the eclipse from the path of totality, but we’ll drop in a link to any webcast that does turn up prior to eclipse day.

Update: Astronomer Gianluca Masi and the Virtual Telescope has indeed secured a live feed for the eclipse from South America, starting at 14:30 UT/9:30 AM EST.

Times for the Eclipse

The entirety of the eclipse, from first partial phases over the remote central Pacific at 13:34 Universal Time (UT) until departure of the Moon’s outer penumbra near Ascension Island in the Atlantic at 18:53 UT, spans 5 hours and 19 minutes.

An animation of the December 14th eclipse. Credit: NASA/GSFC A.T. Sinclair.

The maximum duration for totality along the umbra’s path is much shorter, topping out at 2 minutes and 10 seconds near Sierra Colorado, Argentina.

Partial phases for the eclipse extend from Antarctica, all the way north to the Amazon River Basin in Brazil and Guayaquil, Ecuador.

Here’s a selection of circumstances for partial phases from around the region:

Location: Partial percentage/time

Palmer Station Antarctica: 30%/16:28 UT

Falklands: 70%/16:32 UT

Buenos Aires: 82%/16:29UT

Santiago, Chile: 80%/16:02 UT

Montevideo, Uruguay: 78%/16:33 UT

La Paz, Bolivia: 30%/15:50UT

Asunción, Paraguay: 45%/16:27 UT

Lima, Peru: 25%/15:22 UT

Rio de Janiero, Brazil: 41%/17:15 UT

The passage of the shadow over South America. Credit: Michael Zeiler/Atlas of Solar Eclipses: 2020 to 2045.

Tales of the Saros

A solar eclipse occurs when the Moon passes between the Earth and the Sun near one of its nodes intersecting the ecliptic plane, and must occur by definition at New phase. Next Monday’s total solar eclipse is member 23 of 72 eclipses in solar saros cycle 142, which runs from 1624 to 2904. This cycle just started producing total eclipses on 1786.

If you’re lucky enough to stand in the shadow of the Moon on the 14th, be sure to check out brilliant Venus 24 degrees to the west of the Sun, and Jupiter closing in on Saturn for a historic 6’ conjunction on December 21st, just 35 degrees to the east of the Sun on eclipse day. Another special guest may turn up as well: Comet C/2020 S3 Erasmus, shining at +4th to +5th magnitude. The comet will be just 11 degrees from the eclipsed Sun, fresh off of perihelion on December 12th.

The sky lineup at mid-eclipse. Credit: Starry Night.

As a sort of cosmic consolation prize, the slim waning crescent Moon will also occult (pass in front of) Venus for the northwestern Pacific and far eastern Russia on the morning of December 12th, less than 48 hours prior to the eclipse.

Occultation path
The footprint of the December 12th occultation of Venus by the Moon, prior to the total solar eclipse. Credit: Occult 4.2.

What will the corona look like? That’s always a key question, as the shape and intensity of the Sun’s outer atmosphere can indeed vary from one eclipse to the next. Eclipse chasers can actually look at photos of previous eclipses, and tell you which eclipse they were from.

The predicted shape of the corona during this month’s total solar eclipse. Credit: Predictive Science, Inc.

The Sun is also waking from its long slumber. Just last week, we had a massive sunspot, easily the largest yet for the current otherwise lackluster solar cycle #25. Though it has since rotated out of view, we could easily be in for more, adding to a very photogenic eclipse during the partial phases. Whatever rotates into view over the next week will be visible on the Earthward face of the Sun, come eclipse day.

solar eclipse
Observing the 2017 total solar eclipse. Credit: Dave Dickinson.

Will we get views of the eclipse… from space? It’s not out of the question, as several solar observing missions also occasionally nab views of eclipses from orbit. One such high-flying mission is the European Space Agency’s Proba-2 observatory:

Finally, if you are fortunate enough to observe this month’s total solar eclipse in person, be sure to practice proper eclipse observing and safety. Use proper ISO 12312-2 certified eclipse glasses throughout all partial phases of the eclipse, and use aperture-fitting filters meant for solar-observing on all optics. NASA has a good page dedicated to solar observing safety. One interesting option is to build a safe binocular solar filter, using a tea-box and an extra set of eclipse glasses:

When’s the next one? Well, 2021 hosts two solar eclipses: an annular eclipse crossing the Arctic on June 10th, and a total eclipse crossing the Antarctic on December 4th.

Hopefully, worldwide travel will be opening up again by then, so we can once more witness totality in person.

Lead image credit: The 2017 total solar eclipse. Credit and copyright: Sharin Ahmad.