Hungry for summer? Set the alarm
Winter is the shortest season of the year, at least astronomically.
Again, we’re talking astronomically. Weather-wise it can be a whole different matter! Even if you enjoy this season, winter is starting to get a little old. Visions of summertime are starting to play inside your head.
Winter is the shortest season due to the fact that the Earth travels faster around the sun this time of the year. That’s because the Earth’s 365.25-day orbit is not exactly circular, but slightly elliptical or oval-ish. This time of year the Earth is around 3 million miles closer to the sun than it is in the summer. Because we’re closer, the sun has a stronger gravitational tug on our world. That causes the Earth to move more rapidly in the winter. The same thing happens when you tie a string around, say, a doughnut, and swing it horizontally above your head. If you shorten the length of the string and swing it with the same force the donut will move faster around your head. This time of year the “string” between the Earth and the sun is shorter so the Earth moves faster.
How much faster? Quite a bit! Right now Earth is chugging along on its orbital track at well over 67,500 miles per hour, more than 2,000-mph faster than it does in the summer. Because of that lazier summer pace, it takes 94 days to go from the first day of summer to the first day of autumn, but because the Earth pounds the orbital pavement at a faster pace in winter, it only takes 89 days to travel from the first day of winter to the first day of astronomical spring. Feel better about winter now?
If that doesn’t help, use a tool that astronomers have in their toolbox, time travel. Classically, astronomers used the speed of light to travel back in time. The speed of light is 186,300 miles per second, and a light-year is the distance light travels in one year’s time. That works out to be nearly 6 trillion miles. So if you see a star that’s 100 light-years away, that works out to about 6 hundred trillion miles, but also by definition you’re seeing that star not as it appears right now, but as it appeared a century ago. A hundred years in the lifetime of stars is just a speck in time. Thanks to the Hubble Telescope and other advanced telescopes both on land and in space, astronomers now have the ability to see galaxies that are over 10 billion light-years away. When you see galaxies that far away you really get a look back into time as to what those galaxies looked like in the early stages of our known universe.
So how would you like to fast forward to summer? It’s possible with a time machine, your alarm clock! Get out of the sack and under the stars about an hour before morning twilight and you can see the same night sky that you will see in the early evening right around the Fourth of July. You can experience early summer in the middle of winter, at least astronomically. You can see summer stars without mosquitoes!
The particular set of constellations and their placement in the sky at any one time depends on what direction into space your part of the Earth is facing. That’s controlled by both the Earth’s 24-hour rotation on its axis and its slower orbit around the sun. It just so happens that before morning twilight from our vantage point in Marshall we’re facing the same direction in space as we do in the early evening in late June. In fact, if you want to get an advance viewing of your evening skies four to five months in the future, check out the sky just before morning twilight invades.
Armed with a hot cup of coffee you can enjoy summer constellations like Bootes the hunting farmer, Cygnus the swan, Delphinus the dolphin and most of Scorpius the scorpion this week in the early morning hours. Hopefully that will help you along until metrological summer gets here!
Speaking of Scorpius, the celestial scorpion is hanging very low in the southern pre-morning twilight, and above that in the same general part of the sky you can see the planet parade. Three bright planets, Saturn, Mars, and Jupiter, are lined up near one another from left to the right.
Jupiter is farthest on the right and the brightest of the planet trio. Through even a small telescope or decent pair of binoculars you can see up to four of Jupiter’s largest moons that resemble tiny little stars. I say you can see up to four because they change their positions from day to day on either side of the great planet. At times, one or more of them maybe behind the great planet or camouflaged in front of it. You might even see some of Jupiter’s darker cloud bands across the 88,000-mile diameter planet. Jupiter is about 475 million miles from Earth right now.
Saturn, on the left side of the planet parade, is way out there at nearly a billion miles away from Earth. Despite the vast distance take a look at it with even a small telescope and you should see Saturn’s ring system and maybe even some of its brighter moons. It will be a lot closer this summer.
Mars, in the middle of the early morning planet lineup in the southern sky, is a lot closer to the Earth and will be really close up and personal this summer. Earth and Mars are currently separated by 133 million miles, but in late July that gap will shrink to just over 35 million miles! That’s the closest Mars has been to Earth since 2003, and almost as close as it’s been in nearly 60,000 years. With the naked eye you can easily see Mars’ reddish hue. You can’t make out much detail on its surface even with a decent telescope, but that will change big time this summer. Stay tuned!
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St Paul and is author of the book, “Stars: a Month by Month Tour of the Constellations” published by Adventure Publications available at bookstores at http://www.adventurepublications.net.