Archive for March 19, 2020

03/19/2020 – Ephemeris – Mars will pass Jupiter tomorrow morning

March 19, 2020 Comments off

Ephemeris for Thursday, March 19th. Today the Sun will be up for 12 hours and 7 minutes, setting at 7:54, and it will rise tomorrow at 7:44. The Moon, 3 days past last quarter, will rise at 6:31 tomorrow morning.

Spring will start today, or rather this evening 10 minutes before midnight. But today I’d like to talk about something more immediately visible than the vernal equinox, that is the conjunction of Mars passing Jupiter tomorrow morning. In astronomy a conjunction means that the two planets pass north and south of each other. On Earth we’d say that they had the same longitude. In the sky that would be the same right ascension. The term longitude in the sky is given to measurements along the ecliptic or Sun’s path in the sky, which were more important to ancient astrologers interested more in the motions of the planets, which hung close to the ecliptic. On Earth, measurement of longitude is made from Greenwich Observatory in England, in the sky right ascension is reckoned from the point in the sky where the Sun will be at 11:50 this evening.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Jupiter and Mars in conjunction near Saturn

The three morning planets in the southeast at 7 a.m. Friday March 20, 2020. Appearing in the southeast means that Mars being south of Jupiter does not mean that it is not directly below Jupiter. See the chart below. Created using Stellarium.

Jupiter and Mars in conjunction near Saturn with equatorial grid

The same chart as above with celestial equatorial coordinates. The lines labeled 19h and 20h near the top are right ascension lines. The lines crossing them are lines of declination which are analogous to latitude on the Earth. Created using Stellarium.

Slightly off topic

Right ascension is measured in hours, minutes and seconds.  Because the Earth revolves within the starry sky in 23 hours, 56 minutes and 4 seconds, special clocks can be made to run fast by that amount.  These are sidereal clocks, and tell sidereal time or star time for one’s location on the Earth, which is the right ascension of the sky or celestial sphere on that’s due south or more properly on the meridian.

Time panel for LookingUp

The time panel from my LookingUp program showing date, time and the sidereal time that corresponds to it for my location.