Thursday, March 15, 2012

Daytime Astronomy

Here’s something interesting you can do during the day: look for Venus in the sky. It is visible in the middle of the day in the bright, clear blue sky. Yes, even while the sun is still in the sky. For the next few weeks, it will be visible in daylight.
Finding it is the tricky part.
Venus in the day lit sky on Tuesday, March 13, 2012.
First of all, it is silly to look for it if you don’t have any idea where to look. There are astronomy programs for both iOS and Android that allow you to point your phone at the sky, and the program will show you what is in that direction. Look around the sky for Venus using this program, and it will show you roughly where to look with your own eyes.
Second, stand near a tall tree or building. If you stare into a featureless blue sky, your eyes have nothing to focus on and your eye muscles will relax. When relaxed, the average human eye focuses at just under a meter. Naturally, this means that anything beyond this point will be out of focus. As Venus appears to be a point of light in the sky, if it isn’t in focus, you aren’t going to see it. If you stand near something tall, the top of the object will give your eyes something to reference for focusing at a distance.
Another good reason for using a tall object is it gives you a point of reference to explain where it is in the sky. Invariably, people are going to note that you are standing there staring at something and will want to know what you are seeing.
Venus looks just like a star in the bright blue sky. When you spot it, you will be amazed at just how bright it is! You will then wonder how you could ever have missed it. (See my second point above about focus.)
Another trick for finding Venus is to look for the moon when it comes around again and is in the sky close to the planet. The moon is a little easier to spot and you can use it as a visual reference to find Venus. It helps to look at the moon the evening before to figure out where it is relative to Venus. Keep in mind that the moon moves more than you think in does, and by the next day it will have moved from where it was relative to Venus the previous evening.
If you really want to raise the bar, take a look at this picture. Move the cursor over the bottom-left and top right-corners if you can’t figure it out. I took this picture back in November, 2004. I'm trying to repeat that image, but the weather hasn't exactly been cooperating with me the past few days. I also think that Jupiter is further away this time, and so isn't quite as bright as it was back then.
Looking at Venus in the daytime gives me an idea of what people might have seen when SN-1006 appeared in the sky, which was much brighter than Venus can ever become. It was the brightest supernova recorded in human history. People could see their shadows by it. Not too many years after that, SN-1054 exploded, creating the Crab Nebula.