A fine sight greets early risers this week into the month of February, as all five naked eye planets: Mercury, Venus, Mars, Saturn and Jupiter ring the sky from horizon to horizon.
Though not a true planetary alignment as extolled by many websites, this is a great chance to see all five classical planets above the horizon at once… or seven, if you count the waning gibbous Moon and the rising Sun, as the ancients did as part of their geocentric, Earth-entered universe. You can kinda see how they got there, as the very heavens themselves seemed to whorl about the cradle of earthly human affairs.
Here’s a scorecard and a planet-by-planet breakdown guide to the February dawn sky:
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Jupiter is the most westward of the group, shinning at magnitude -2.3 in the constellation Leo. The Moon passes 1.3 degrees SSW of Jupiter on January 28th, and Jupiter is headed towards opposition for 2016 on March 8th.
Moving eastward, the planet Mars shines at magnitude +1.0 in the constellation Libra. The waning crescent Moon passes 2.7 degrees NNE of Mars on the first morning of February. Watch Mars later this spring, as we’re in for a fine opposition of the Red Planet on May 22nd. Oppositions of Mars happen roughly every other year, and the next opposition in 2018 will be nearly as favorable as the historic 2003 appearance of the Red Planet. This also means that 2016 is a launch year for all missions martian, and the European Space Agency’s (ESA) Gas Trace Orbiter launches from Baikonur on March 14th headed Marsward.
Next up is Saturn, shining at magnitude +0.6 in the dreaded ’13th zodiacal constellation’ of Ophiuchus. The waning crescent Moon visits Saturn on the morning after Candlemas and Groundhog’s Day (February 3rd), itself a cross quarter tie-in day lying approximately mid-way between the December solstice and the upcoming March equinox. Saturn represented the edge of the solar system right up until the discovery of Uranus in 1781 by William Herschel. You can be thankful his proposal to name Uranus ‘planet George’ after his benefactor King George the III of England didn’t stick. Saturn reaches opposition for 2016 on June 3rd.
Next is up Venus, the most brilliant of the five planets shining at magnitude -4.0 low in the dawn sky. The Moon pays Venus a visit on February 6th, with both about 30 degrees elongation west of the Sun.
Completing the picture is bashful -0.1 magnitude Mercury, which reaches greatest elongation 25.5 degrees west of the Sun on the morning of February 7th. This is the first apparition of 6 for Mercury for 2016. The shallow angle of the February dawn ecliptic shoves it down towards the southern horizon for northern hemisphere viewers, giving folks in the Sun-drenched southern hemisphere a better view. A good day to check Mercury off of your life list is February 13th, when Venus approaches four degrees to the west (without a conjunction in right ascension).
This is not a true grouping or planetary alignment in the strict sense, but a good chance to catch all the naked eye planets in a rough line in the ‘forward-looking windshield’ of planet Earth.
The closest span of the planets occurs mid-next week, when the swath from Mercury-to-Jupiter will cover a breadth of 110 degrees across the sky. The closest actual minimum difference in heliocentric longitude looking down (or up?) on the plane of the solar system is 84 degrees in early February, spanning the five planets from the solar vantage point from Saturn to Jupiter.
How rare are true groupings of all five? Jean Meeus compiled a list of close grand conjunctions from 3101 BC to 2735 BC. Hey, Stick around until September 8th, 2040 and you can witness a grouping of all five planets in the (plus the Moon!) in the dusk sky . Lets see, by then I’ll be…
Set your alarm, and don’t miss this grand planet parade through the dawn sky. Hey, is the elusive ‘Planet Nine‘ photobombing the view as we speak? Now, that’s an amateur astronomer discovery that I’d love to see…
-Intro image credit and copyright: Alan Dyer/Amazing Sky Photography