1. Transit of Mercury May 9, 2016

2. Outline A transit of Mercury is about to happen May 9, 2016 Very rare event Visually impressive event Shows the solar system orbital mechanics at work A small version of the extremely rare Venus transit St. John’s is very favoured for this event Best Mercury transit for the next 50 years This presentation will outline how transits work and give observation details and local circumstances for St. John’s

3. What is a transit? When observing a celestial body partially cover a second body If that celestial body fully covers the second body, then this is an occultation Many examples Transit of Mercury/Venus Transit of a Galilean satellite and/or its shadow on Jupiter’s disc Transit of ISS in front of the Moon/Sun On Mars, transit of Phobos/Deimos in front of the Sun An exoplanet transiting a star

8. Possible natural transits seen from Earth From Earth, only possible planetary transits in front of the Sun are Mercury and Venus Also possible for a planet to transit another planet Exceptionally rare Last was in 1818 (Venus transited Jupiter) Next is in 2065 (Venus will transit Jupiter) Annular solar eclipses are technically a transit Asteroids transiting stars or planets

9. Mercury and Venus Transits Very rare events Mercury transits: 13 or 14 times per century Always in May or November Venus transits: Pairs separated by more than a century Always in June or December

10. Orbital conditions for Mercury transit First requirement: inferior conjunction

11. Orbital conditions for Mercury transit Second requirement: Mercury at node

12. Mercury transit characteristics November transits Recur in periods of 7, 13 and 33 years Mercury is smaller at 10’’ May transits Recur in periods of 13 and 33 years Mercury is larger at 12’’ Largest disk this transit for the next 50 years (12.1’’)

13. Future Mercury transits Table 4: Transits of Mercury: 2001-2100 DateUniversal Time Separation 2003 May 0707:52708" 2006 Nov 0821:41423" 2016 May 0914:57319" 2019 Nov 1115:2076" 2032 Nov 1308:54572" 2039 Nov 0708:46822" 2049 May 0714:24512" 2052 Nov 0902:30319" 2062 May 1021:37521" 2065 Nov 1120:07181" 2078 Nov 1413:42674" 2085 Nov 0713:36718" 2095 May 0821:08310" 2098 Nov 1007:18215"

14. Visibility

15. Transit events External ingress Internal ingress Greatest transit Internal egress External egress

16. Local circumstances May 9, 2016 Events for St. John’s in local time: Contact I (external ingress): 8:43:17 Contact II (internal ingress): 8:46:29 Greatest transit: 12:27:22 Contact III (internal egress): 16:07:47 Contact IV (external egress): 16:10:59 Total duration: about 7½ hours

17. Observing the event Need a telescope with proper solar filter (white light, Hα, etc.) Very important to use safe filter, as with any solar observation! Sun’s apparent diameter is about 30’ Mercury’s apparent diameter is about 12’’ So Mercury’s disc will be 1/158 that of the Sun! Need 50-100X in a telescope for good observation Great photo op! If lucky, Mercury may pass over or near a sunspot or over prominence Watch for black drop effect during ingress and egress

18. Weather prospects Weather prospects: St. John’s May 9, past 30 years, 7.5-hour period Cloudy: 27% Mostly cloudy: 27% Mostly clear: 37% Clear: 10% Also Snow: 10% Glorious (20+ C and sunny): 13%

19. Some hype Very rare event Great opportunity if you missed Venus transit St. John’s is extremely well placed Best location in North America One of the best locations in the world Good weather prospects It’s a May transit so Mercury is bigger and weather is warmer Best transit for the next 50 years RASC event?

20. Thanks! Clear skies! Any questions?