So the editors passed on my original title for these posts; after some discussion and a small Facebook survey, I’ve chosen a new title — The Infinite Canvas — for this continuing series of space art and astronomical photographs. Thanks to Garret Moore for the title, and to my colleagues in the International Association of Astronomical Artists for all their suggestions.
As something suited to introducing the new title, I’m going to pull out one of my favorite pieces of space po… — er, of sky photography, the Hubble Deep Field.
Of course, this is hardly new — but it is, I think, the most profound thing I’ve seen in my entire life. You see, this image, taken over the course of many many hours’ exposure, is about one quarter of the whole Hubble Deep Field image; the whole image is about one minute of arc (1/60th of a degree) across, so this image is about 15 arc seconds across.
To put that in perspective — if you took a dime, and held it up for a friend 750 feet away — call it two and a half football fields — that dime would cover about the same angle as this image. Looked at another way, that’s about 3 ten-billionths of the whole sky.
Now look at the image: two of the bright spots have X-shaped lens flares. Those are stars in our Milky Way Galaxy. Every single bright spot in the image, other than those two, is a whole galaxy, most of them as big as the Milky Way or bigger.
And every single galaxy has hundreds of billions of stars, many of them just like our Sun.
And,we’re now learning from studies using a new technique called gravitational microlensing, every star has, on average, at least one planet — closer to two, in fact.
How many galaxies are in that image? A hundred? A thousand?
Take that times 300 billion.
Take that times another 3 billion. Roughly.
And take that times 2.
And that is how many planets there are in the Universe.