Keeping Track Of Baby, Er, I Mean Jupiter

Jupiter joins the Hyades and Pleiades star clusters in the western sky at dusk in early April. This map shows the sky facing southwest-west around 9 p.m. Maps created with Stellarium

Planets are like children. If you don’t keep you’re eye on them, they’re likely to wander away.

High in the west when it first gets dark Jupiter blazes away for all to see. A short distance below the planet you can make out the bright red-hued star Aldebaran and V-shaped pattern of the Hyades star cluster. To Jupiter’s right sparkle the Pleiades, the star cluster with the familiar “little dipper” shape. One of the reasons the Pleiades appears smaller than the Hyades is distance. At 424 light years, the Pleiades is 2 1/2 times farther away.

Orion is at center, Sirius, the sky’s brightest star at left and Jupiter at right in this photo taken April 1st north of Duluth, Minn. Photo: Bob King

All three of these eye-grabbers are in Taurus the Bull, one of the 12 zodiac constellations. All of the planets move through the zodiac star groups at different rates depending upon their distance from the sun. Mars takes about two years, Jupiter 12, Saturn 29 and Neptune, the most remote planet, 165 years. None of us will live long enough for to see Neptune cycle make a complete cycle.

The planet with an orbital period most closely matching the human life span is Uranus at 84. A child born this year could look up under a dark sky and see the planet in Pisces the Fish and then return 84 years later to find at nearly the same spot. An entire life bound up in the orbit of one planet.

Jupiter on the move! Last April it appeared in Aries, this year in Taurus and next year will be up above Orion in Gemini the Twins. Jupiter takes 12 years to cycle through the 12 zodiac constellations.

Jupiter’s not only much brighter than Uranus but moves fast enough in its orbit for us to see it skip from one to the next zodiac constellation year to year. In 2012, Jupiter held court in Aries in the Ram and stood very low in the west at twilight’s end. Since then, it’s slid eastward into Taurus and still stands high on early April evenings. As the planet continues its journey around the sun, it will sit even higher in the sky in Gemini the Twins one year from now.

While Jupiter does require “supervision”, it doesn’t wander randomly as a child might. It and the other planets keep to the main highway. One benefit of this is that you can always find the planets among these same dozen constellations. They don’t wander off toward the North Star or decide to head south for an Australian vacation. Reason why? They’re confined to the flat plane of the solar system. As each circles the sun, we see them traveling along the same narrow path in the sky.

The planets, sun and moon all travel a similar path (in pink) through the zodiac constellations shown here facing south at nightfall in early April.

Get to know the zodiac and you’ll always be able to identify that odd “star” that shouldn’t be there as a planet. Jupiter and Venus are the brilliant ones and appear white to pale yellow. Saturn is less bright, more like a typical bright star, and also looks slightly yellow. Mars waxes from as brilliant as Jupiter to only as bright as a star in the Big Dipper due to its sharply varying distance from Earth around its orbit. Oh, and it’s red.

Mercury (and Venus) either hang low in the western sky at dusk or eastern sky at dawn. Uranus can be glimpsed with the naked from a rural location and Neptune requires a small telescope or pair of binoculars.

Good wishes on a long life! May you be around long enough to see seven planets to orbital completion.

6 Responses

  1. Dan

    Hi Bob,
    I saw your presentation today at Rotary (great job!) and I thought you may want to see a couple of meteorites we’ve got at our office. One of them weighs 92 pounds, and the other is 115, and are about the size of a volleyball and a basketball. I’m around on Friday, but out next week. Drop me a note and we can make arrangements.

  2. Edward M. Boll

    I might of if I had seen Uranus at birth. I still have not positively identified it yet. Next time it is near Venus, I will give it a try. That makes the location a little easier.

  3. Mike

    Always great articles Bob. Looking for Panstars last night using your handy map. Found it…I think : ‘ ) but it was very faint smudge. Please let us know when and where you will be speaking in the future Bob. Take care!

    1. astrobob

      Hi Mike,
      Sounds like you found it alright. Depending on where you’re at and the aperture of your binoculars it would appear as a faint smudge to a pretty decent-looking comet. I observed from dark skies last night and saw it well with 10×50 binoculars. Getting your eyes dark adapted also helps alot. I took a few more photos which I’ll have in the blog today.

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