Hubble Target Sizes - How big?, How to estimate the size of an object in a Hubble image? Options

[David]

I was amusing myself with an entertaining online slideshow of Hubble pictures -- mostly the usual suspects, colorful or oddly shaped nebulae, galaxies and so on.

One thing that occurred to me rather quickly on seeing these structures in succession was that I had no idea how big they were compared to each other (or to anything else); nebula pictures don't usually come with a ruler attached, and there are obviously no objects in the picture to compare to! But presumably if we know the approximate distance of the object, we can estimate its size fairly accurately, certainly well enough to make comparisons.

What I was thinking would be neat would be something along the lines of the famous Starship Dimensions charts, which graduate images by factors of ten; a page showing all objects of a comparable size, with something larger and something smaller to give you a relative sense of scale, and the ability to click up and down for pictures at different scales.

Unfortunately, I have no idea where to go to get scales for these sorts of images; and asking "how big is the Horsehead Nebula" is not as easily answered as "what is the diameter of Jupiter". Does anyone have any suggestions?

[Jyril]

Many of the Hubble press releases have a "Fast Facts" page. They usually include the original press release image attached with a ruler.

Of course, if you know the distance to the object and the width of the image in degrees/archminutes, you can easily calculate the width of the image at the distance of the object.

I agree, that sounds cool idea. Unfortunately, I don't know if such a page exists...