Daylight Saving Time Puts Spring Stars On Ice / ‘Cosmos’ Premieres Tonight!

1918 post card that citizens could mail to their congressman to show support for the daylight saving time law, which was enacted on March 19, 1918 in the U.S. Click to read the history of DST. Credit: Library of Congress

It happens every year. The seasonal westward drift of the stars is temporarily put on hold when we “spring forward” an hour on the second Sunday in March.

With daylight saving time or DST we gain an hour of evening daylight and lose an hour of early morning light. After a long winter, who doesn’t welcome more light at the dinner hour?

A one-hour later sunset naturally means an additional hour for night to begin. Yesterday, twilight ended and true night began around 7:45 p.m. Darkness descends tonight around 8:45 p.m. Since we’ll have to wait that extra hour for stars to come up in the east, the time change has the effect of retarding every star’s rising by an hour.

Sirius, the brightest star, heads up the constellation Canis Major the Big Dog and is very prominent in the southern sky this month. With the start of daylight saving time, it now appears one hour east (to the left) of where it was last night at the same clock time. Stellarium

For instance, last night around 8:30 p.m. I watched brilliant Sirius twinkle west of due south. When the clock glows 8:30 p.m. tonight, Sirius will sparkle east of due south. The same holds true for Orion and the other winter stars. Compared to last night at the same clock time, the winter constellations will be higher up in the sky. Meanwhile, the spring constellations of Leo, Virgo and Bootes, which have been steadily gaining ground in the east, will be shoved back an hour.

While it’s not a great hardship, it does mean that to see the cool spring stuff, we have to go out an hour later compared to a night ago. I’ve been watching Mars finally make its way into the evening sky. To observe it now means getting out at midnight instead of 11. Oh well.

All will take care of itself in due time. We’ll come to accept the change, just as our bodies will finally figure out to do with the hour we lost. And since the westward drift of stars with the seasons never stops, come late-April, Sirius and friends will be memories and bright Arcturus and Mars will gleam in the southern sky.

View of Earth’s orbit around the sun seen from above the north pole. As we zip along at 18.5 miles per second, we see a different set of constellation in the night sky depending upon where we are in our orbit. From this moving perspective, the background constellations appear to drift to the right or westward. Credit: Bob King

As Earth travels in its orbit around the sun at 18.5 miles per second, we peer into a different direction in space as the weeks and months pass. Think of going for a ride on one of those merry-go-round horses at a carnival. As the merry-go-round turns, we look out to see a different part of the fairground as the seconds pass. After one spin, the view repeats until the ride is over.

If you substitute the Earth for the horse and our orbit for the merry-go-round, the very same thing happens during a year’s stargazing with the view repeating once every year. During Earth’s “little spin” around the sun, we see the stars and constellations drift from east to west across the sky as we pass them by.

This isn’t the same as the nightly rising and setting of stars – that’s due to Earth’s rotation. Every star you see makes a complete circle around the sky in 24 hours. The much more leisurely seasonal drift is superimposed on that pattern and reveals itself to sky watchers who spend time regularly under the stars.

Cosmos trailer on Fox-TV. The series will air at 8 p.m. Central Time Sundays starting tonight 

A final note. The new 13-part “Cosmos” TV series, hosted by astrophysicist and astronomy popularizer extraordinaire Neil deGrasse Tyson, starts tonight on Fox-TV at 8 p.m. CDT (Central time) and 9 p.m. Monday nights on the National Geographic Channel. Don’t miss it!


11 Responses

  1. Sean

    i have to admit, it kind of annoys me the way things like “the sun rises one hour later” etc. end up sounding. while technically accurate, this kinda makes it seem as tho the sun is doing something different, whereas it isn’t whatsoever. it’s we humans who have “artificially” adjusted our clocks regardless of the unchanging cycle of natural patterns. it would be nice if we had a phrase that better described that reality. like “our clocks read one hour later when the sun rises” but more elegant.

  2. Norman Sanker

    Hey Bob, the new “Cosmos” looks good though Tyson is a bit subdued from his usual, ebullient self and let’s hope it doesn’t fall in love with its own graphics and become unable to show real, unretouched images that moved science along. Lovely moment at the end where the host held Sagan’s planner from the 70’s showing a meeting with a 17-year-old named Tyson and a book inscribed “to a future scientist.” I got all misty. Later. Norman Sanker

    1. astrobob

      My feelings too. Loved the end as well as the cosmic calendar. There were a few too many asteroids in the asteroid belt but I suppose the real thing wouldn’t look anywhere near as interesting on TV.

      1. Norman Sanker

        Bob, I saw w-a-a-a-y too many asteroids as well but I’m not sure anything would be noticeable at that scale. All the asteroid belt objects added up would equal what? Mercury, the moon, Mars? Not much, anyway. I found X-1 LINEAR this AM: the one comet from those crowded mornings when ISON still existed that I couldn’t locate. Aquila had me confused for a while but, when I finally figured out where I was looking, I found it pretty quick. Typical, dimmish comet–any theories about its early outburst? Always so mysterious. Was the cosmic address part of the original “Cosmos”? I don’t remember it. Good idea, though. Later. Norman

        1. astrobob

          Good going on finding X1 LINEAR. I went out this morning to look for it, Lovejoy and PANSTARRS K1 too, but we had a lot of clouds, so I looked at Mars and Saturn instead. I haven’t heard of what may have happened but would suspect a fissure (or weakening of crust) with exposure of fresh ice. Or it could have been a bubble of trapped gas beneath the surface that ruptured the surface, again exposing fresh ice. I don’t recall the address being Sagan’s – it doesn’t show up in some of the lists of quotes attributed to him.

  3. Dave Gallant

    Now if we could find a merry-go-round horse that chases it’s tail – we’d have a great model. 🙂

    That cosmic calendar thing really got me too..that’s something that I’d love to work into my campground talks (as well as the merry-go-round analogy).

    1. astrobob

      So many great ideas out there. I loved the beam of light radiating from the “last second” of the cosmic year. Very nice effect.

  4. Troy

    The asteroid sequence bothered me as well. It was more reminiscent of the 1980s arcade game “Asteroids” rather than the real asteroid belt.
    Overall the show is well done. Neil Degrasse Tyson is an apt pick, as well as having a direct pedigree to Sagan himself. When I first heard about the Cosmos reboot I thought Bill Nye would be a better choice. As both have been CEO of the Planetary Society I always thought Nye was the more inspired writer (and he also studied under Sagan). Though I now think I was wrong about that one. Tyson is more telegenic and an apt presenter. My big complaint is that with commercials there is only about 40 minutes per episode, makes me appreciate the original PBS format.

    1. astrobob

      Another minor pick on my end about Cosmos. The Big Bang explosion. I wish there had been some way to include him inside the blast to show that it didn’t happen “out there” like a bomb blowing up.

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