Travel Far, See New Stars

A snow-covered peak in the Rocky Mountain looms above the main road in Rocky Mountain National Park Saturday. People are walking because snow closed the road a short distance beyond. Bob King

As summer approaches, many of us like to get in a car or plane and travel to new places or spend time with distant friends and family. I recently returned from a trip to Fort Collins, Col. for my niece’s college graduation. We ate huevos rancheros, tramped around in the Rockies and talked in the glow of a drier drum fire. My niece has repurposed an old dryer drum into a fire pit. Highly recommended.

Latitude and longitude define the location of places on the globe. Latitude is measured north and south of the equator. Longitude is measured east and west of the prime meridian which passes through Greenwich, England.

When you travel east or west of your home it only affects the rising time of the stars. If you live in Iowa and fly to Baltimore the stars rise an hour earlier. It gets dark there an hour sooner. Fly to Utah, and it gets dark an hour later. Otherwise observers in both places see the identical stars. But if you travel north or south of your home, which stars you see changes. Even driving 1o0 miles (160 km) makes a difference but too subtle for most of us to notice.

But if you travel a couple thousand miles like I did, the difference becomes obvious. I live at 47°N latitude. Three hours and one pat-down later I arrived at 40°N, having flow 7° of latitude south of my Duluth, Minn. home. Right away, I noticed that the sun appeared higher in the sky, 7° to be exact or a little more than three fingers held together at arm’s length. The extra sunshine had advanced the season by about 2 weeks compared to home.

The nearly full moon also stood 7° higher in the sky, so I had to crank my neck back a little more than normal for a look. Like the sun, all the stars in the southern sky had moved upward (north) by 7°. The difference boosted the visibility of Corvus the crow, a little rhombus of stars located low in the southern sky from home. Contrariwise, when I faced north all the stars in the northern sky appeared 7° lower including the famous North Star.

When you travel south, stars otherwise hidden by your local southern horizon ascend above it. To “make room” for the newcomers every star south of the overhead point, called the zenith, also slides upward. Stars north of the zenith — in the northern sky — drop lower to make room for the pusher-uppers. I could easily tell that the North Star had descended in the north compared to the view in Duluth.

This is the sky tonight viewed from 47°N latitude around 11 p.m. local time. Compare this view with the one from Ft. Collins below. Stellarium

The really fun part of globe-trotting is seeing new stars that have always been hidden by your southern horizon. No new bright stars popped into view at 40°N, but a chunk of the southern constellation Centaurus invisible from Duluth rose high enough for me to make out. Had I traveled another 10° south, say to Houston or New Orleans (both at 30°N latitude), I would have seen the topmost star in the Southern Cross called Gacrux. Ten more degrees and the entire cross would have sailed into view. Meanwhile, the North Star would have sunk ever lower in the northern sky.

The summer Milky Way also gains visibility the farther south one travels. From the northern states one of its brightest sections, which billows from the southern sky constellation Sagittarius, has to compete with light-sucking haze and light pollution. Not so much from the southern U.S. where its increased altitude places it in a darker sky.

From Ft. Collins, Col. at 40°N notice how much higher the moon, Jupiter and Scorpius are. Centaurus and neighboring Lupus the wolf also come into better view, and Corvus stands higher. Stellarium

If you’re traveling north or south this summer, keep an a tourist’s eye on the sky. To find out if there’s a significant difference in latitude (north-south distance) between your home and your destination, use this latitude/longitude calculator. Regular skywatchers can easily discern differences of 5° or more with the naked eye. Polaris, the North Star, is a handy indicator. Shoot a line downward through the two Pointer Stars in the Big Dipper to the first star of similar brightness — that’s Polaris. If you know how high it is from home, you’ll see a difference.

The more familiar you are with the bright stars and constellations of the season the easier it will be to see their change in elevation when you travel. Download the free Star Chart app (iPhone / Android) and use it to find planets and constellations from your home. Then when you travel, it will pick up on your current latitude and show you new stars to look for. If you live in the mid-northern latitude belt and travel south, keep watch on the southern sky for new stars and increased visibility of constellations near the horizon.

Jet lag may be one of travels’ most familiar consequences, but the slipping of the stars makes one’s journey palpable in a more pleasant way.

1 Response

  1. kevan hubbard

    7 degrees is pretty significant infact canopus almost hits the horizon at that latitude.i live in Oxford in southern England (about 51.5north)and my mother lives in a village in north east England (about 54.6 north) and you can over the small 3 degrees notice the difference,for example in Oxford it gets properly dark after about 23hr around the solstice but up north it doesn’t.i don’t notice a great deal of change with stars around the southern horizon mind with those 3 degrees but if I jumped on a series of trains, about 7 of them counting metro trains in London and Paris, and go down to cassis in the south of France about 42 degrees north then new stuff is obvious to me like the tail of the scorpion (on the horizon from Oxford and under it from the north East) and grus.i have just, using my 10×42 monocular,seen m6 from near Oxford strangely by going a bit north to a village called Kings Sutton where the horizon is darker but just over the 52 parallel.i can’t get m7 or shaula.of course elevation is important to and I suspect that fort Collins is pretty high above sea level so you’d see further around the Earth’s curve.

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