You are here: Home News Caution, Mercury Crossing

 Members and donors are our most important source of support. 

Donate Button
Membership button
 Thank you

Sign up for 



Goodsearch button 


Write a review of  
Explorit Science Center   

on Trip Advisor Logo 




Caution, Mercury Crossing

This article first appeared in the 11/8/19 edition of the Davis Enterprise.

Caution, Mercury Crossing

NASA's SDO studios the sun 24/7 and captured the entire 7 1/2 hour event of Mercury's transit of the sun on May 9, 2016. Photo by NASA's Goddard Space Flight Center/SDO/Genna Duberstein.


Caution, Mercury Crossing

by Vinita Domier


On the morning of Monday, November 11, the elusive planet Mercury will transit the sun. This rare planetary event will commence at 4:35 am and end at 10:04 am. For observers in the western USA, the transit will already be underway when the sun rises locally at 6:43 am. Looking through binoculars or telescopes equipped with proper filters, Mercury will appear as a small black dot traversing across the face of the sun. The next opportunity to behold Mercury transiting the sun will be on November 13, 2034.


A planetary transit occurs when one planet is observed to transit the sun when viewed from another planet. The very narrow shadow cone of the small planet obscures only a very tiny portion of the sun when viewed from earth. Only Mercury and Venus transits can be viewed by earth-based observers as the planets’ orbits lie within earth’s orbital path around the sun. This is also why only Mercury and Venus exhibits phases similar to the earth’s moon phases when viewed from earth. When Mercury or Venus is in between the earth and the sun, it is known as inferior conjunction, and when the sun is between the planet and the earth, it is known as superior conjunction.


A transit can only occur during or close to inferior conjunction when the planet is between the sun and the earth. Even though Mercury takes only 88 days to revolve around the sun (its sidereal period), duration between inferior conjunctions is 118 days (its synodic period) as the earth too is revolving around the sun. A Mercury transit does not occur at every inferior conjunction as the orbital plane of the planet is inclined at 7° to the earth’s orbital plane. This usually results in the planet crossing above or below the sun from earth’s point of view. Mercury transits are possible only in May or November when its orbit crosses the earth’s orbital plane.


Ordinarily, Mercury is difficult to observe as it rises and sets close to the sun. It can be glimpsed for a brief period just before sunrise or just after sunset. All other times, it is lost in the sun’s blinding glare. Hence Mercury transits are ideal times to observe the planet even though they are relatively rare astronomical events. There are typically only 13 or 14 Mercury transits per century, each lasting for several hours.


Everyone is invited to join the Davis Astronomy Club members on Monday, November 11 from 7 am to 10 am at Explorit Science Center (3141 5th Street, Davis) to safely observe Mercury transiting across the face of the sun. There will be solar telescopes set-up for public viewing for enthusiasts of all ages.


Also join us on Saturday, November 9 at 7pm at the free public meeting of the Davis Astronomy Club at Explorit Science Center (3141 5th Street, Davis) where we will discuss the upcoming Mercury transit event indoors followed by a star party outdoors. 




Explorit's coming events:



  • Looking for something fun during Thanksgiving break?  Workshops will be available on 11/25 & 26 from 9am-12pm, as well as extended public hours on Wednesday, 11/27 from 10am-5pm.  Registration begins Monday, 11/11.  Call (530) 756-0191 for more information and registration.


  • Explorit’s Nature Bowl team is still enrolling for the school year.  This is an afterschool science team from students grades 3-6.  Call (530) 756-0191 to register.  The $25 fee covers weekly meetings and a t-shirt.


  • It’s not too early to think about the holidays.  A great gift would be an Explorit Membership for your friends and family.  For more information or to purchase or renew your membership visit or call Explorit at 530-756-0191.  Buy soon as membership prices increase January 1, 2020.



  • Giving Tuesday is December 3.  Support science in your community by giving to Explorit.
Document Actions
Personal tools