Sic Transit Glorious Monday

Transit of Mercury weather, 2019-11-11Today, Monday, November 11th, 2019, is the long-awaited transit of the planet Mercury across the disc of the Sun, the last such event before November 2032.  Now, before the transit of Venus in June 2004, I vowed that if I got good weather for that spectacle I wouldn’t complain about the weather ever again.  The weather, and the transit, were glorious, so I’m not complaining.  But I can grumble, can’t I?  Here is the weather looking out my window.  This was taken around an hour ago, and since then the ground fog has only gotten thicker.

So, it’s off to the Webcasts.  The NASA Solar Dynamics Observatory (SDO) is watching the transit from space, where the event starts about half an hour before it becomes visible from Earth.  Their Web site was down, presumably crushed by the dozens of people hoping to see the transit there, but it has recently come up and is showing Mercury crossing the inner solar corona (which is only visible from space), approaching the solar disc.... [Read More]


Reminder: Transit of Mercury, November 11, 2019

Transit of Mercury, 2003-05-07Next Monday, November 11th, you can watch Mercury, the innermost planet, cross the disc of the Sun.  This was the subject of Saturday Night Science for September 2019, and that article gives complete details of the event, a global map of visibility (the transit is visible, in whole or in part, from almost all of North and South America, Africa, and Europe), and recommendations for visual observation and photography of the transit.

You’ll need optical assistance (binoculars, a modest telescope, or a telephoto camera lens) equipped with a safe, full-aperture solar filter, in order to see the tiny disc of Mercury (just ten arc-seconds) crossing the Sun.  If you’re interested in observing and haven’t yet secured and checked out the required gear, now’s the time to opt for overnight shipping—there’s just a few days left.... [Read More]


Saturday Night Science: Transit of Mercury, November 11, 2019

Transit of Mercury, 2003-05-07On November 11th, 2019, between 12:35 and 18:04 universal time (UTC), Mercury, the innermost planet, will pass in front of the Sun as seen from Earth: an astronomical spectacle called a “planetary transit”.  Planetary transits visible from Earth are relatively rare events: only the inner planets Mercury and Venus can ever pass between the Sun and Earth, and they are only seen to cross its disc when the plane of the planet’s orbit intersects the plane of the Earth’s orbit (the ecliptic) close to the time when the planet is at inferior conjunction with the Sun.  On most inferior conjunctions, the orbital planes do not align (or, in other words, are not close to a node crossing) and the planet “misses” the Sun, passing above or below it as seen from Earth.

Mercury’s orbit crosses the ecliptic around May 8 and November 11 at the present epoch, and so transits always occur within a few days of those dates.  The most recent transit of Mercury was on May 9th, 2016 (when, despite being clouded out for most of the event, I managed to briefly observe and photograph it through thin clouds), and the next transit will not occur until November 13th, 2032, so if you miss this one, you’ll have a thirteen year wait until the next opportunity.... [Read More]