Answer to this question varies with the season: Mercury, Venus, Mars, Jupiter and Saturn can be observed through naked eye at various points throughout the year.
Careful daily observation will reveal each planet’s orbit around the sky; Mercury and Venus move at an especially rapid pace, while Mars and Jupiter tend to follow behind at their respective paces.
Mercury
Mercury is one of the smallest and fastest planets in our solar system, orbiting very closely around the Sun with each orbit taking just 88 days to complete. Due to this fast orbital speed, Mercury may appear very close or far away depending on when we observe its surface – making it extremely challenging to see without a telescope.
Mercury can be easily found during the final ten days of March in the predawn twilight before sunrise, when looking low over the eastern horizon about twenty minutes before sunrise. Binoculars will help provide a view; Mercury shines like a very large star! On March 25th and 26th it will come close to Venus making for an amazing sighting; both objects should fit within your binocular field of view on both days!
Mercury lies so close to the Sun that it never experiences seasons like Earth and Mars do, reaching temperatures as hot as 800 F (430 C) during daylight hours before plunging to an astonishingly frigid minus 290 F (minus 180 C) overnight. Scientists speculate that water may remain frozen within some of Mercury’s deep craters for extended periods of time, creating permanent shadows.
Astronomers have learned much from NASA’s MESSENGER spacecraft about Mercury by studying data collected by it. This probe revealed that its core is liquid and that its magnetic field differs considerably from Earth’s; experts speculate this might be caused by differences in atmospheric structure on Mercury.
The table below details when Mercury and Venus will reach their greatest elongation in the evening sky this month, providing you with information to plan when and where to look for them. These planets should remain visible for several weeks either side of these dates. In addition, there is also information regarding Mercury, Venus, and Mars reaching their closest approach to Earth for brief periods; you should find more details by consulting this table.
Venus
Venus has been stunning us this month with her brilliance, particularly after sunset twilight twilights. Sometimes misunderstood as UFO-like objects in the sky, Venus remains one of the brightest objects visible until late May – it plays an integral part in both human culture and astronomy.
Venus was the first planet ever fully mapped and studied, and is the only other known body with a magnetic field similar to our own. While not currently habitable, Venus does exist within our Sun’s Goldilocks zone and could have once supported life. Ancient peoples found Venus inspiring due to its similarities with Earth in terms of density and composition; perhaps that explains why Homer (“Iliad,” Odyssey”) and Edgar Rice Burroughs (“Pirates of the Caribbean”) wrote extensively about it in their works.
Venus may be the brightest planet in the night sky, but Jupiter can sometimes outshone it. On 1 and 2 March as evening twilight fades away, they will appear closely together just half a degree apart (about the width of your pinkie at arm’s length).
Both planets can be easily seen without binoculars. Their highest position will be within Leo, the lion constellation (though Venus will dip lower as time progresses). With patience, you may be able to find a spot where you can view directly at the horizon and directly look upon its stars to spot this duo of planets.
Binocular users stand a good chance of seeing three of Jupiter’s four largest moons: Europa, Io and Ganymede all together in front of its planet. All you need is a very dark sky free from light pollution for this to work properly.
Mars
Planets that can be seen with the naked eye move around in our sky over time, with Mercury and Venus moving at an increasingly rapid rate requiring daily observation to spot them shifting against background stars. Mars, Jupiter, and Saturn move more slowly and require longer for observation before shifting. Saturn even requires its own telescope in order to be detected at all.
As 2017 winds down, Mars continues its slow journey toward the Sun and closer alignment. You will only be able to spot this red planet for another month – make sure you search out for it daily as its closest approach to Earth will occur on January 12, 2025.
Mars can reach magnitude -1.2 at its brightest, covering 15 arcseconds across the southern horizon just after sunset. Being one of the dimmest planets, you will require a fairly large telescope in order to resolve details in its disk. Doubling magnification will reveal smudges of color where dark and lighter regions on Mars rub against each other, possibly even showing glimpses of polar ice caps!
Mars can be easily found during the evening when it rises at around 9:30 pm and rises high into the eastern sky by midnight, setting two-thirds of the way to its zenith in Taurus constellation. You should see it here until August, when it will shift into morning twilight.
Planets are bright enough to be easily seen with binoculars, while using an app such as Sky Tonight can make viewing them even simpler. Such apps will provide details on where each planet lies within their respective constellations as well as any relationships among them. Just beware: stargazing too closely towards the Sun could cause permanent eye damage. Therefore it is recommended that either using such an app or consulting a professional to achieve optimal results.
Jupiter
Jupiter, the fifth planet from the Sun, stands out brightly in the nighttime sky as it is one of the Solar System’s largest and most massive gas giants. Famously known for its Great Red Spot and multiple moons such as Io, Europa, Ganymede, and Callisto which Galileo saw through his first telescope, Jupiter can be seen even brighter by being illuminated with red.
Jupiter is distinguished by a distinct cloud cover that appears as light and dark stripes, created by crystals of frozen ammonia forming light zones while darker belts contain various other chemicals; wind speeds in some regions reach over 400 miles per hour.
Visibility of Jupiter gradually improves throughout April, reaching its best on April 1. At that time it was 18 degrees high in the morning sky two hours after Sunset. By month’s end it had grown to 25 degrees at sunrise but began fading into May until it finally vanished altogether at 10 degrees above horizon.
Venus and Mars fade with each passing month, leaving only Jupiter visible in the morning sky. Due to its brightness and rapid pace of orbital movement, Jupiter is much harder to spot. To view it you will require binoculars or small telescopes for viewing purposes.
Today is an exceptional night to observe Jupiter, as the planet is closer than it has been in 13 months, appearing larger and brighter than usual. This phenomenon occurs because Jupiter has reached opposition; each planet in our Solar System achieves this milestone approximately every 13 months, when their orbits align with that of our Sun and rise in the east before setting in the west.