Four Planets in the Early Morning Sky? Sleep In.
May 2011
One of our main objectives at the Sudekum Planetarium is to get everyone outside to look at the real sky. After you join us for Skies Over Nashville in the planetarium, look through a telescope at a star party, or use one of our monthly star charts, our goal is that you will be able to find a few constellations or a planet on your own. The last thing we want is for you to become frustrated or disappointed by the sky, or worse - give up.
So, there’s a reason we haven’t spent much time on the much-publicized grouping of planets in the pre-dawn sky: you would have a very hard time seeing it.
If you haven’t heard, there are four planets near each other rising in the east just before sunrise: Venus, Jupiter, Mars, and Mercury. Of these, only Venus really stands out. Jupiter is there if you know where to look. Mars and Mercury are so faint and lost in the glow of sunrise that they are nearly invisible. Even under the best conditions, you’d need binoculars to spot them any time this month.
To go into a little detail, let’s look at the morning of May 31, 2011. In Nashville, official sunrise is at 5:34 am. If we go out half an hour earlier, at 5:00 am, the glow of dawn is already beginning to brighten the sky. At this time on this morning, Jupiter is 18 degrees above the horizon.
Eighteen degrees? That sounds like a temperature, but in astronomy, it’s a measure of the apparent distance between two objects in the sky. Fortunately no special tools are needed to estimate these ‘angular distances’ because all you need is your hand. If you hold your hand out at arm’s length, and stretch your fingers and thumb as wide as they go, the distance between the tip of your pinky and the tip of your thumb is approximately 18 degrees.
Now, where is the horizon? Imagine there are no trees or buildings or hills. Imagine you’re on the ocean. Imagine you’re in Kansas. Flat areas such as these are the kinds of places where you can see the actual horizon. In our part of the world, there are all kinds of things in the way, so you’ll have to give it your best guess. Fortunately, Jupiter is still relatively high and bright so you can verify your measurement.
Venus is very bright but sits only five degrees above the horizon. Your middle three fingers held together and held at arm’s length is about 4 degrees wide. Mars is higher - eight degrees - but much fainter. And on this morning tiny Mercury is just one degree above the horizon. One degree is about the width of your little finger, held at arm’s length. On this particular morning, there is another nearly invisible bonus - a very thin crescent Moon, eight degrees up, directly above Mercury.
As the Earth turns, all of these objects will continue to rise higher above the horizon, but so will the Sun, quickly hiding them all from view. Even if you could see them to begin with, they’ll all be gone by 5:20 if not much sooner.
Don’t forget the weather. Even if you have clear skies, early morning haze along the horizon will further obscure faint planets. We’re entering the humid part of the year, and in Middle Tennessee it’s almost impossible to find a morning without some haze to the east.
So, if you are really determined to see these planets, your best bet would be to get out of Tennessee. Travel west, to somewhere very dry and flat. Or, if you travel south of the equator, the planets would appear a little bit higher in the sky! Road trip!
Call us a wet blanket, but we recommend just sleeping in. Saturn is showing off its rings right now in the early evening sky. Jupiter will be great this fall, and Mars will put on a good show in early 2012. On November 12, 2011, there will be a lovely pairing of Mercury and Venus, just two degrees apart, and Venus and Jupiter will be three degrees apart on March 14, 2012. Plus, there are always constellations to find along with star clusters, nebulae and galaxies waiting for you to discover with your binoculars. We’ll be here to let you know about them all, and your questions are always welcome. Contact us at planetarium@adventuresci.com, or just bring your questions to a star party or Skies Over Nashville. We look forward to hearing from you!
