As in December, January’s action will be lunar as well as planetary with two inner planets on stage during the month.
The new year begins with a very thin crescent moon at sunrise with lunar perigee about eight hours later and the new moon at 10:33 the next day. The nearly simultaneous perigee and new moon means that the lunar tidal forces will be greater than normal and lined up with solar tidal forces. Coincidentally, Earth is closest to the sun at 23:00 on Jan. 3, so the sun’s tidal forces are at maximum as well. We’re in for big tides in that first week, just like December 2021. Since I can’t guarantee any table I could build would survive the conversion to newspaper format, I would just recommend checking the weekly tide tables the Coast Reporter publishes in every issue anyway. Basically, low tides will be around midnight and high tides will be around 06:00 to 09:00.
While all this lunar stuff is going on and the tides are awesome, Venus and Mercury are also going to put on a show. Mercury will start to be visible in the southwest, just after sunset as early as Christmas Day, below and just right of Venus. Mercury is moving daily eastward as it comes around from behind the sun while Venus is moving westward as it swings around between Earth and the sun for its inferior conjunction on Jan. 8. The two pass about 3 degrees apart on Dec. 28 and by Dec. 31, Mercury will be fairly bright and about 7 degrees straight left from Venus relative to the horizon. On Jan. 3, the pair are joined by a very thin new moon and all are no more than 7 degrees above the horizon. By Jan. 13, Mercury will have started to move westward and northward and will disappear by about Jan. 18 as it comes around in front of the sun for its inferior conjunction on Jan. 23. For all dates, the reference time is around 17:00. Note how quickly things happen with Mercury: its mean orbital radius is less than 40 per cent of our own and it moves 60 per cent faster than Earth at more than 47 km/second. As well, note that all directional references refer to the line of the ecliptic – the path that the sun follows through the sky as we orbit it each year.
Most of the planets generally follow the ecliptic but both Mercury and Venus orbit in slightly different planes than Earth, tipped 7 and 3.4 degrees to Earth’s orbit, respectively. For Earth’s current location at this time, for both planets, when they’re on the far side of the sun, their orbits are south of the ecliptic. As they pass between us and the sun in January – inferior conjunction – they’ll be as much as 5 degrees north of the ecliptic. As I mentioned in last month’s article, by Jan. 8, Venus will be only 0.266 astronomical units (the Earth-sun mean distance) from Earth and just more than 1 minute of arc in apparent diameter – one thirtieth the size of the moon. This is discernible even with a pair of 7 x 30 binoculars as a reasonably large but very thin crescent. The convenient part is that, since Venus’ orbit is tipped to our own, it will pass about five degrees north of the sun and will be visible for a week or two both in the evening in the southwest and the morning in the southeast. Mercury will do the same thing but will be at most 3 degrees north of the sun at inferior conjunction. It should reappear in the morning sky just before sunrise by the end of the month, however, below and to the left of Venus.
The next online meeting of the club should be at 19:00 on Jan. 14; signup information will be available on the club site at: sunshinecoastastronomy.wordpress.com.
