May 2014 – The Planets on Parade


Hello everyone, I’m Darrell Heath with the UALR College of Science and I’ll be your guide to what’s up in the night sky.

Back in my day there were nine planets but with Pluto having been re-assigned as a dwarf planet our solar system now has eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. And you may not know it but chances are you’ve seen at least five of them with your unaided eye. That’s right, the planets Mercury, Venus, Mars, Jupiter and Saturn can all be seen as naked eye objects and all five will be on display during the month of May.

When these five planets are visible some of them can be among the brightest objects in the night sky and folks often mistake them for very bright stars, aircraft, or even UFOs.

Take the planet Venus for example. Venus is the brightest object in our sky apart from either the Sun or Moon. It and the planet Mercury orbit very close to the Sun and, depending on where they are within their orbit, we see them either in the early evening or predawn hours. When Venus is up during the evening many people refer to it as “The Evening Star” and when it is in the predawn sky it goes by the name of “The Morning Star”. Throughout May you can see Venus in the eastern sky about an hour or half hour just before sunrise. On May 25th look for a very lovely pairing of Venus with a crescent Moon.

A large number of UFO sightings turn out to be nothing more than the planet Venus but sometimes even experienced observers can mistake it for other objects. In 2011 the First Officer aboard an Air Canada flight mistook the planet for an oncoming aircraft and immediately took some drastic evasive maneuvers that gave the plane’s passengers a rather bumpy and frightening ride.

The ringed wonder of our solar system, the planet Saturn, comes into its own during May and June. On May the 10th the planet is at opposition, which means it lies opposite the Sun with the planet Earth in between the two. When a planet is at opposition it appears in the eastern sky right at sunset and is up throughout the night. On May 10th Saturn will be at its closest to Earth and will be at its very best for telescope viewing.

With its intricate ring system of ice and rocks Saturn is a beautiful and surreal looking image in a telescope. In all the years that I’ve been showing folks the planet through my own scope it never fails to elicit responses such as “Oh my gosh!” to “That isn’t real!” At a public event I actually had someone accuse me of having painted the image onto the lens of the telescope. I wasn’t offended, it’s just a testament to the awesome beauty of this planet that can actually make people believe that what they are seeing is some kind of an illusion. If you do not own a telescope be sure and check with the Central Arkansas Astronomical Society or Pinnacle Mountain State Park for free public events this summer that will allow you a close up view of this wonderful planet.

Look for Saturn in the southeastern sky after sunset during May within the constellation of Libra.

To the upper right of Saturn, in the constellation of Virgo, you will find the Red Planet Mars. Mars reached opposition back in April but its ruddy red glow still stands out quite well as it shines brightly in the southeast at nightfall. Why does Mars look red? The answer is rust. The planet is covered in a fine layer of red dust composed of iron oxides that have weathered out of the volcanic rocks that litter the surface. Through binoculars you will see a red or pink disc but with a small telescope it’s possible to see ice caps around the poles made from both water and carbon dioxide ice. Larger telescopes may even reveal dark surface features where the red dust has been blown away by one of the planet’s global dust storms. While the planet is cold and dry today, NASA rovers such as Opportunity, Spirit, and Curiosity have revealed that Mars did at one time have liquid water on its surface and that its climate was warmer than it is now. This raises the question as to whether or not life could have ever evolved there and, if it did, could it still exist beneath the soil or hidden away in underground caverns. Until we finally send human explorers to the Red Planet we will probably never know for sure.

Turning our attention away from the east and southeastern sky at nightfall we will look to the west to see both the solar system’s largest and smallest planets: Jupiter and Mercury

Jupiter, the King of the Planets, reached opposition back in January and now hangs around in our evening sky for a lesser amount of time than it did then. During the month of May look for it in the west right at sunset; it stays up for several hours before finally setting around midnight. Jupiter is very bright at magnitude -2.0, outshining all the other evening planets. Right now you can see Jupiter within the constellation of Gemini and it is very close to the stars Castor and Pollux, the famous twin brothers of the constellation. Both Jupiter and Saturn have over 60 known moons and with just a pair of binoculars you can see Jupiter’s four largest: Io, Europa, Ganymede, and Callisto. Until we visited the planet with unmanned probes we had assumed that Jupiter’s moons would be dead, frozen worlds, what we found instead was truly amazing and forced us to change many of our views about the outer parts of our solar system. For example, the moon Io turns out to be the most volcanically active place in the solar system while the moon Europa seems to hold a liquid ocean of water beneath its icy crust making it a likely place to visit in our quest for life elsewhere in the solar system. What makes these tiny worlds so active? The answer seems to be the constant gravitational tugs and squeezes that the parent planet and the other moons exert upon one another. This constant squeezing and pulling from Jupiter’s immense gravitational forces heats up the interiors of some of these moons to the point where volcanism and oceans of liquid- water become possible. This heating effect is known as “tidal heating” and we see it at work with some of the moons of Saturn as well.

With a small telescope it becomes possible to see the dark and light banding within the cloud layers of this gas giant planet. If you time it just right you can even see the Great Red Spot, a giant storm that, as far as we can tell, has been raging on Jupiter for some 400 years.

Mercury, the innermost and smallest of all the planets, always stays close to the Sun (just like Venus) and we only ever get to see it as either an early evening or early morning object. Mercury can be seen soon after sunset by the end of the first week of May but during the last two weeks of the month and the first week of June the tiny planet will be at its best for viewing. On May 24th it lies some 23 degrees away from the Sun, the greatest angular separation between the two all month. Wait until about an hour after sunset and scan along the western horizon with binoculars to first spot it. As it gets a bit darker Mercury will stand out nice and bright to where you will see it without the binoculars. On the evening of May 30th you can easily find it right above a thin crescent Moon.

During the last week of May and first part of June you can see four naked eye planets in just one evening and if you get up early enough to catch Venus that brings the total to five alien worlds you can see with your very own eyes.

Until next time I encourage you to get outside, look up, and wonder.

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