Next 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]
On 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]
The Kepler spacecraft was launched into heliocentric orbit in 2009. Its primary mission was to stare at a small area of the sky and monitor around 150,000 stars in its field of view (around twice the size of the bowl of the Big Dipper), watching for the subtle dimming of stars when planets orbiting them passed in front of their parent stars (a transit). Before its retirement in October, 2018, it had discovered 2,662 exoplanets (planets orbiting stars other than the Sun). It also saw some other, very curious things.
You may have heard about Tabby’s Star (KIC 8462852), a main sequence star which exhibits irregular deep dimmings which have, so far defied all attempts to explain them.... [Read More]