I love Isaac Newton’s saying that if he had been able to see further than others, it was only because he had stood on the shoulders of giants. Now, the exact intent of this utterance has been under debate, but there is no doubt that Newton could see far, but just how far?
At night we can see objects many light years away. The Andromeda galaxy is easily visible to the unaided eye and is nearly two and a half million light years away. This is my personal limit, as I don’t remember ever observing M33 with the unaided eye as some have claimed. M33 is roughly three million light years away, and some folks probably have seen it unaided, but I haven’t.
In 1054 a supernova exploded into Earth’s skies, shining much brighter than Venus and according to what I have read (see here), was visible in the daytime for 23 days. Today we can still see its remant, if only at night, in the Crab Nebula some 6,300 light years away.
Tycho’s Star, a supernova seen in November 1572, was said to be visible in daylight for about two weeks (see here). It’s distance has been estimated at about 10,000 light years.
While a daytime supernova is possible at any time, they are pretty rare, so I am not holding my breath. But I am not satisfied with limiting myself to the Sun — there are farther things to see in the daytime.
If I went out this afternoon (4/19/07) and looked, undoubtedly I would be able to observe Venus in daylight. As write, it is cloudy here in Denver, but it is supposed to clear up, and maybe I will try this afternoon. Right now Venus is about 165 million kilometers from Earth, some 15 million or so kilometers farther than the Sun. It can get much farther than that, but at those times it is closer to the glare of the Sun and harder to find.
But is there anything farther that can be seen by the unaided eye in daylight? The answer is yes, but not for now. Right now I have to go outside and try to blow those clouds away!
Larry S.
Clouds & Cosmos - It’s all over your head!
Postscript: It cleared up and I went out at about 3 p.m., when the Moon and Venus were crossing my meridian, high overhead to the South. Using the roof of my house as a shade, I immediately caught the two and a half-day old Crescent Moon. No worries! Easy if you just look in the right place. However, try as hard as I could, I could not find Venus. After a few teary minutes (the bright sky made my eyes water), I gave up and took the dogs on a walk. When I got back, about 4 p.m., I tried again. Immediately I found the Moon, but this time within a minute I found Venus, too. Even with my old and highly refracted eyes, it almost jumped out like a prankster on Halloween! You should try it, but keep the Sun out of your eyes!
I think those of us who love astronomy might love it partly because of its quality of letting us look across vast distances.
I know I like to look across distances on land, or on the ocean, as well.
When my kids were babies, we lived in the country for a time, and I could see a little village of lights off in the distance from my bedroom window. At night, if I couldn’t sleep, I’d just lie there looking out the window at those distant lights … and they gave me the same peaceful feeling that stargazing does.
Don’t know why!
Deborah