Observing the Planets: Jupiter

By Peter Forrester | March 28, 2019

Jupiter, as seen from the surface of the Earth, is on average the second brightest of the five visible planets. Only Venus is brighter (and sometimes Mars). This is reflected light from the Sun, as planets don’t produce any light of their own. Jupiter’s reflected light is bright enough to cast shadows on Earth (the brightest apparent magnitude it reaches is -2.94).

Being so bright, Jupiter has been known since ancient times, and was thought to represent the god Marduk to the Babylonians, and the gods Zeus and Jupiter in Greek and Roman mythology, the last of whom it is named for.

Unlike Venus and the Moon, Jupiter doesn’t go through a full range of phases, being more distant from the Sun (at times as much as 11.5% of the side we see is not illuminated, so it does have the Full and Gibbous phases only). It also takes 11.86 years to orbit the Sun, meaning it will move about 30 degrees in the sky every year (the twelve years of the Chinese calendar were originally based on this orbital period). So it can be hard to remember where it is located, but it (and even more so the more distant planets) tend to move very slowly among the stars, lingering in the same constellation for months to years. This is an advantage if you can remember where to look. Jupiter will take many months to cross Ophiuchus, since it is a very large constellation.

We just passed an occasion a couple of days ago where the Moon was located very close to Jupiter. But how can you find it normally?

Jupiter has just entered the constellation Ophiuchus, the “13th zodiac” constellation, located above Scorpius. According to the planet locator on timeanddate.com (see link below), it will be above the horizon (from their nearest location to Milton in Concord, New Hampshire) between 1:24 and 10:25 am tomorrow.

If you have a smartphone, you can also find the current location of any planet on the free app Sky Map (you have to make sure the constellation labels are on and follow the Zodiac constellations around to find all the planets, Moon, and Sun). You can find some other excellent websites by doing a simple Google search.

Observing Jupiter with the naked eye, it just looks like a very bright yellowish star. However, if you have a chance to look at it in a telescope, which I have had the pleasure to do, I suggest you take it. You can see its round shape, including the aforementioned Great Red Spot, as well as the many belts of clouds and some or all of the four Galilean moons, whichever happen to be on the same side. The whole planet will be lit up because we are between Jupiter and the Sun right now.

Stay tuned for more on this amazing object in the sky. Have fun watching Jupiter, and pleasant star-gazing!


Previous in series: Observing the Planets: Venus


References:

Time and Date A.S. (1995-2019). Night Sky Map & Planets Visible Tonight. Retrieved from https://www.timeanddate.com/astronomy/night/.

Wikipedia. (2019, March 26). Jupiter. Retrieved from https://en.wikipedia.org/wiki/Jupiter.

Author: Peter Forrester

I have been interested in astronomy and stargazing for many years, and now delight to offer some of my learning to others through my weekly blog posts.

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