You won’t need binoculars to penetrate the obscurity of space and spot several planets forming a large “parade” late January. It will be, technically speaking, a large planetary alignment wherein six planets will all line up among the groves of stars.
Five of the six will be visible to the naked eye. All of them—Mars, Jupiter, Uranus, Neptune, Venus, and Saturn—will be present on the night, but the brightness of Neptune will be insufficient to see without powerful binoculars while Uranus will be just visible without optical aid.
As of Jan. 15, a good number of these planets had already been positioned close together. However, this sextet will be grouped most tightly, and thus most spectacularly, on Jan. 21. A few days’ grace on either side will widen that window.
Starting with the most prominent planet, the morning star Venus will outshine the lot. With its magnitude -4.7 brightness, Venus will gleam within the constellation Aquarius. (Magnitude is the metric by which astronomers gauge brightness, whereby lower measurements equal brighter objects.)
Gas giant Jupiter will appear second-brightest with its magnitude of -2.6, shining in the constellation Taurus.
Next, Mars will radiate its rust-red hue from the constellation Gemini with a magnitude of -1.3.
Faint but still visible, Saturn, with its rings, has a magnitude of 0.6, slightly duller than Polaris, the Northern Star. This planet will sit next to Venus in the constellation Aquarius.
The limit of human sight falls on magnitude 6—equal to the faintest stars visible to the unaided eye. So, with its magnitude 5.7, Uranus will be almost invisible on the night of the alignment, appearing next to Jupiter in Aries.
Last, Neptune will be buried in darkness with its magnitude of 7.9. Sunken and invisible to the naked eye, it will dwindle somewhere within Pisces.
To look southward, gazing from east to west, the planet parade will appear in this order: Mars, Jupiter, Uranus, Neptune, Venus, and Saturn.
In answer, first imagine looking downward upon the solar system from afar. When three or more planets are grouped on one side of the sun, this is a textbook planetary alignment. (“Planetary parade” is a colloquial term used in popular space magazines.)
Actually, for anything in a three-dimensional universe to align perfectly in space is astronomically improbable. There are reasons for this, and also for why the planets line up very regularly to form a ragged row, but never a straight line. It’s no accident.
Astrophysics is the cause for orbital planes of all the planets, including Earth, being almost level with one another. Logically, it follows that the sun’s arc across the sky, called the elliptic, overlaps Earth’s orbital plane and, by extension, that of all the planets. Thus, to trace the sun’s arc at any given time is to trace a planetary procession. No wonder they look like a parade every now and then.
A few planets grouped on one side of the sun (while not being drowned out by sunlight) or in a small sky sector is a notable sight from Earth. The closer the grouping, the more impressive the formation.
The number of planets involved also distinguishes the alignments, of which there are several types. Three in a group is a mini alignment. Four make a small alignment. To have five or six is a large alignment (as the next one will be). A great alignment includes seven or more planets. An observer may always throw Earth into the mix, as it qualifies. One might even add Pluto.
Merely two planets isn’t an alignment, however, but a planetary conjunction, which we won’t cover here.
Yes.
But such jaw-dropping oddities won’t diminish the Jan. 21 not-so-rare large alignment. Nor will you have to wait long for an addition to the alignment. On Feb. 28, Mercury will join the present lineup, making a bigger parade, though it may be washed out slightly by the evening sun.
