Even if you are not normally an early riser, it is worth setting your alarm clock to have a look at the celestial spectacle in the pre-dawn sky. Like pearls on a necklace, all five planets, Mercury, Venus, Mars, Saturn and Jupiter, are visible without a telescope and lined up across the sky, from southeast to southwest. During the first week of February, the waning moon will add to the spectacle.
It has been a decade since all of the naked-eye planets have been visible simultaneously in the sky. What is perhaps most striking about the planets is their arrangement in the sky. They are not just scattered randomly around the sky, but are (more-or-less) lined up one right after the other. This is because the planets all orbit the Sun in a common plane (give or take a few degrees). In other words, the solar system is “flat.” Consequently, when all of the planets are visible at the same time, they literally trace out the orbital plane of the solar system.
Where to watch
The public can take part in telescopic viewings of the planets at the St. Petersburg College planetarium/observatory on the following dates:
- Wednesday Feb. 3
- Thursday Feb. 4
- Friday, Feb. 5
The best time for viewing will be between 6 and 7 a.m. On these dates the moon will add to the spectacle, and Mercury will be more easily visible as well.
Please be aware these event are held weather permitting; telescope viewing is cancelled if skies are not clear.
Three stars of the zodiac also visible
There are 12 constellations that lie in the plane of our solar system, where the planets are always found. These are the familiar constellations of the zodiac, which most people recognize as their astrological Sun signs (the Sun also appears to move through these constellations). In fact, three bright stars of the zodiac are included in the current astronomical alignment.
To the west of Saturn is the bright star Antares in Scorpius. The star Spica, in Virgo, lies between Mars and Jupiter. To the west of Jupiter is Regulus, the brightest star of Leo.
These stars can be easily mistaken for some of the planets, but there is a way to tell the difference. Because the stars are so very far away, they are essentially infinitesimal points of light, even in the largest telescopes. The tiny size makes them susceptible to distortion by the Earth’s atmosphere, causing them to shimmer, or “twinkle” (the technical term is scintillation). In contrast, the planets do not appear as infinitesimal points, and are less affected by the Earth’s atmosphere – they do not twinkle as the stars do.
How to identify the planets
The planets Venus and Jupiter appear as the two brightest “stars” in the pre-dawn sky, and are easy to identify (Venus is the brighter of the two, and farther to the east). Venus is our nearest planetary neighbor, and is very similar to the Earth in size and mass. However, that is where the similarity ends. Its 900 degree surface temperature, sulfuric acid clouds, and crushing atmospheric pressure make it a hellish environment.
Jupiter, shining farther to the southwest, is a resident of the outer solar system. Unlike the inner planets, Jupiter is made almost entirely of liquids and gasses, with no solid surface at all. It is also the king of the solar system, larger than all of the other planets combined.
Although not nearly as brilliant as Venus or Jupiter, Mars is easily identified because of its distinctive ruddy color. It lies between Venus and Jupiter in the morning sky. Because of its small size and great distance, it is a rather disappointing view in a telescope right now, appearing as a small amber-colored dot.
Mercury and Saturn are also easy to find. Through the middle of February, Mercury will appear as a star to the lower left of Venus – there will be no other star nearby to confuse it with.
Saturn will be to the upper right of Venus, but don’t confuse it with the bright star Antares. Remember, Saturn will shine with a steady light, but Antares (to the right of Saturn) will twinkle noticeably. The beautiful ringed planet always elicits gasps when people see it for the first time in a telescope.
Former planet Pluto joins the show
Although far too faint to see without a telescope (and a pretty big one at that), you might be interested to know that tiny Pluto (formerly a planet) is also part of this early morning celestial show. Right now it is located very close to Mercury in the sky. In fact, on the morning of Jan. 31, distant Pluto passed within a moon’s width of the closest planet to the Sun! Of course, their proximity in the sky is an illusion; Pluto is over 100 times farther from the Sun than Mercury.
Astronomy students learning about motion of planets
Students enrolled in the astronomy courses at SPC (AST1002 and AST1003) have been learning about the motions of the planets, and how people in ancient times interpreted and modeled these motions, so the timing could not be better! It is always nice to relate astronomy in the classroom to what is really going on in the sky. As Jupiter moves into the early evening sky next month, it will become the target of our telescopes and cameras in the observational astronomy lab, AST1022L. Students will take time-lapse photos of Jupiter and determine its rotation period based on the movement of cloud features.
Right now, the best time for planet viewing is around 6:30 am. However, if you simply cannot drag yourself out of bed at that early hour, don’t despair. As the planets (ours included) move along in their orbits, the five planets now visible in the morning sky will become evening planets by next August.