For the Early Risers
Observing > There is so much attention in astronomy given to the evening skies that we often forget to mention that there is a morning sky, as well. To all those who wake at or before the crack of dawn to brave the traffic or open the store, to those who might be getting off work and making their way home in the wee hours, this column is for you.
One of the first objects our early bird readers may have noticed in the last month is a bright - very bright - "star" rising before the sun. That is Venus, our Morning Star. But wasn't it Venus that was the Evening Star just months ago, setting behind the sun in the east? What's it doing over here now, leading the sun?
It was doing what it does best and what it has been doing for countless eons, dancing around the Sun in its orbit. And since summer it has moved by us, in front of the sun, over to the other side. Thus, it now seems to lead our star through our skies rather than follow it. And the best time to see it as it leads that celestial race is in the morning before sunrise when the sky has not yet been blotted out by its starry partner.
Since our sister planet is still moving farther and farther over to the "right" side of its orbit we can observe over the next month how it rises earlier and earlier each morning before the sun. This won't go on forever of course. Venus will have to swing around back behind the sun to the other side to eventually again become our Evening Star. But don't hold your breath. She is booked as Morning Star into the next year, and won't be making an encore appearance as Evening Star until next summer.
One of the most obvious, if also very slow, processes occurring over the next couple months for our early rising readers is the sun's migration south for the winter.
It's been going on for a while, but since the sun is rising later and later every morning it is more convenient for morning commuters to notice.
Of course both the sun's delayed rising and its slow trip south are due to the tilt of our planet. We are tilting more and more away from our fiery gas giant. We are approaching North American winter. And as we do, the sun rises more and more southerly each day. And its rise is more and more parallel with the horizon, not the near straight up shot it is during summer. And it travels lower through the sky each day. Result: Less sun, less warmth, more dramatic shadows, more in-your-face sunshine.
Now migration of the sun is not restricted to the Morning Folk. Those who observe the setting of the sun will notice a similar effect in the west. The sun will set earlier, farther south and at a sharper angle. All making a homeward bound commute considerably less pleasant for them, as well.
Until next time, clear skies!
Posted by Mark Ritter at 2007.10. 8 08:34 PM | Comments (0)
