2017 Jul 23
Dominic Ford – originally published on In-The-Sky.org
The Moon will pass close to the Sun and become lost in the Sun’s glare for a few days.
The Moon‘s orbital motion carries it around the Earth once every four weeks, and as a result its phases cycle from new moon, through first quarter, full moon and last quarter, back to new moon once every 29.5 days.
This motion also means that the Moon travels more than 12° across the sky from one night to the next, causing it to rise and set nearly an hour later each day. Click here for more information about the Moon’s phases.
At new moon, the Earth, Moon and Sun all lie in a roughly straight line, with the Moon in the middle, appearing in front of the Sun’s glare. In this configuration, we see almost exactly the opposite half of the Moon to that which is illuminated by the Sun, making it doubly unobservable because the side we see is almost entirely unilluminated.
Over coming days, the Moon will become visible in the late afternoon and dusk sky as a waxing crescent, setting an hour later each evening. By first quarter, in a week’s time, it will be visible until around midnight. The times below are given in London local time:
|Altitude of Moon
|Direction of Moon
|23 Jul 2017||20:58||20:49||-5°||north-west|
|24 Jul 2017||20:56||21:32||1°||north-west|
|25 Jul 2017||20:55||22:07||6°||west|
|26 Jul 2017||20:54||22:37||11°||west|
|27 Jul 2017||20:52||23:01||16°||west|
|28 Jul 2017||20:51||23:26||20°||south-west|
|29 Jul 2017||20:49||23:50||22°||south-west|
At the moment of closest approach, it will pass within 2°05' of the Sun, in the constellation Cancer. The exact positions of the Sun and Moon will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
The details of this observing event were provided courtesy of In-The-Sky.org