11/06/2019
The November 11, 2019 Transit of Mercury
Mark your calendars! The sky will put on an impressive display when on Nov. 11, 2019 from about 7:30 A.M. EST to 1:05P.M. EST, Mercury moves between the Sun and the Earth and we will be able to see Mercury’s silhouette, a completely black and tiny round dot, traverse the face of the Sun. This type of event is known as a transit and this is the 2019 Transit of Mercury. It's a rare event that you won't want to miss. And if we have a beautifully clear day next Monday as we did today, you won't have to miss it!
So provided we get some clear or partially clear skies during the day on Monday, November 11th, you will be able to come to the Olin Science Center on the Connecticut College campus and view this transit through our 3 and 8-inch telescopes. The weather willing, you will have lots of opportunities to view Mercury majestically sweep across the disk of the Sun as this syzygy dance will be visible for some 6 hours!
As long as the sky is partly clear and we can see the Sun, we will have the Olin Observatory open from 9:00A.M. EST until 1:30P.M. EST. Swing by Olin and check Mercury out! Here’s what the transit will look like about 9am EST in the New London, CT area.
MercuryTransit_9am_20191111.png
To see the full animation of this event from New London, check out: https://www.timeanddate.com/eclipse/in/usa/groton
We on the East coast of the United States are in an ideal location for this Mercury transit. The entire transit will be visible from the eastern US and far-eastern Canada as well as all of South America. For us, the transit starts about an hour after Sunrise and will end in the early afternoon. For locations in more western time zones, the transit will already have started when the Sun rises, so they won’t get to view the whole event. In fact, many people around the world will be able to see at least some part of this event. The only continent that misses out entirely this time is Australia! See the 2019 Mercury transit visibility map below.
TransMercury_20191111_visibility_FEspenak.gif
To help make sense of this map, the terms ingress and egress should be clarified. Here ingress refers to Mercury’s silhouette making first contact with the Sun’s disk and egress, as expected, is when Mercury’s silhouette last appears to touch the Sun’s disk. The whitish and light grey regions on this map show areas of the globe where at some point during the transit, the Sun is above your horizon. The dark grey areas of the map show parts of the globe for which the transit occurs after Sunset or before Sunrise.
So how rare are alignments of the Sun, Mercury and the Earth that produce such transits? Well we only get about 13 or 14 such celestial treats every century and not all of those events are visible from our New London, CT location. In fact, we will not have another Mercury transit visible in Connecticut until 2049! Here is a list of the recent past and future Mercury transits and if we in some portions of the US can observe them or could have:
Date
Universal Time (UT) at mid-transit
EST = UT – 5hours
Separation in arcseconds. This is angular distance between the centers of the Sun and Mercury at mid-transit.
2006 Nov 08
21:41
423" Visible in US.
2016 May 09
14:57
319" Visible in US.
2019 Nov 11
15:20
76" Visible in US whole.
2032 Nov 13
08:54
572" Not visible in US.
2039 Nov 07
08:46
822" Not visible in US.
2049 May 07
14:24
512" Visible Eastern US.
Source: Fred Espenak: http://eclipsewise.com/oh/tm2019.html
The Astronomy Details
Transits of either Mercury or Venus are viewable from our planet as Mercury and Venus both have orbits that are smaller than that of the Earth; such planets are called inferior planets. At some point in their orbits about the Sun, an inferior planet will pass in between the Earth and the Sun and be aligned approximately with those bodies. When this occurs, astronomers say that the inferior planet is at inferior conjunction. This is a form of syzygy. Syzygy in astronomy is a straight-line arrangement of three or more celestial bodies in a gravitational system. In this case, those bodies are the Earth, Venus or Mercury, and the Sun as shown below.
inferior planets.jpg
Some fun facts: At the time of the Mercury transit, Nov. 11, 2019, Mercury will be at a distance of about 0.6758 AUs or 101 million kilometers (km) from the Earth. Recall that the AU or Astronomical Unit is the average distance between the Sun and the Earth, a distance of about 93 million miles or 150 million kilometers. At this time and date, Mercury is close to perihelion which means that it is closest to the Sun and so a bit farther from the Earth and that makes the planet’s angular diameter (angular size that you see) a bit smaller than it gets during May transits – 10 arcseconds is typical for Mercury November transits and 12 arcseconds is typical for May transits. A diminutive planet indeed!
Transits of Mercury and Venus were used in the past to measure the size of the Astronomical Unit. This was first proposed by Edmund Halley in 1716; his method used the idea of parallax and surveying techniques to get the actual, not relative, distances between the Sun and the Earth, and Earth and the inferior planet. A copy of that paper can be found here: http://eclipsewise.com/transit/HalleyParallax.html
Transit_parallax.jpg
Above, you see a two superimposed exposures of the 2016 transit taken at the same time from Caracas, Venezuela and Hannover, Germany showing the parallax of Mercury when viewed against the disk of the Sun from two widely separated locations on Earth. Also shown is an enlargement of the region where Mercury was observed.
In the 18th and 19th centuries, several countries organized expeditions to locations all over the world to observe and measure transits of Venus, thus providing an accurate value of the Astronomical Unit for the first time.
Safe Viewing of the Sun and the Transit of Mercury
As you may recall from the fairly recent (August 21, 2017) partial eclipse of the Sun seen in Connecticut, you should never stare directly at the Sun as it can cause damage to your eyes!!! If you come and view this event though the Astronomy program’s telescopes, you will be able to view safely and comfortably as we have appropriate solar filters installed on all of the scopes we use for Sun gazing events.
If you want to try and view this event by yourself, you will need to get more than just a pair of eclipse glasses or even solar-radiation protected binoculars. The reason for this is that Mercury, being such as physically small-diameter planet, will only appear as a dot with an angular size of about 10 arcseconds. The Sun’s globe viewed from Earth spans as angle at your eye of about 1800 arcseconds on average and at the time of this transit will have an apparent angular size of a bit more than 1900 arcseconds. This means that the dot of Mercury appears some 190 times smaller than the Sun during this transit. And that suggests that without some magnification, you won’t be able to see Mercury as a distinct feature. Just looking with your naked eye won’t work here. To watch this event, you will want to use a solar-filtered telescope with a magnification of roughly 50x. We have this set up in the Olin Observatory for your safe solar viewing pleasure, weather permitting!
You can learn more about safe viewing of the Sun and the transit of Mercury from this nice video from the Open University in the UK: https://www.open.edu/openlearn/science-maths-technology/science/physics-and-astronomy/astronomy/discover-mercury-safety-advice-the-transit-mercury?in_menu=334025 . Another place you can learn about this is from this page from the Society of Popular Astronomy: https://www.popastro.com/main_spa1/solar/solar-observing-guide/2-looking-at-the-sun-safely/ and there are many more such sites out there. Just be aware that without magnification, you won’t be able to see Mercury even though you can see the Sun.
Where to See Live-streams of this event
Sky & Telescope will stream this event live between 6 a.m. and 2 p.m. EST with a commentary at the start of each hour. Check out: http://livestream.com/SkyandTelescope/Mercury.
NASA’s Jet Propulsion Lab (JPL) and NASA TV will live stream the Mercury transit at https://www.jpl.nasa.gov/edu/events/2019/11/11/watch-the-transit-of-mercury-2019/.
Time and Date (http://www.timeanddate.com) will be live streaming the Mercury Transit. They will provide the URL for this feed within a couple of days of the event. The same is true of Space.com (http://www.space.com). Visit their page on Nov. 11 to see their live webcast of the 2019 Mercury transit as shown from telescopes on Earth and in space complemented with complete coverage of this celestial event.
Summary
If it is clear to partially clear any time between 9a.m. and 1p.m. on Monday, November 11th, 2019, I will have a few telescopes set up and safely solar filtered so you can drop by the Olin Science Center and view this celestial wonder, the transit of Mercury. I will post signs on the door of Olin about the sky conditions and if viewing will be possible that day. I will also send out an email about the sky conditions and viewing early next Monday morning (11/11/2019). Please let me know if you have any questions about this event. Keep your fingers crossed for a nice sunny day!
Clear skies!
Which upcoming lunar and solar eclipses are visible in Groton, Connecticut, USA and what do they look like?
