What is the area that Hubble Space Telescope has covered


Today I got intrigued by the following tweet.

FireShot Capture 1 - Knud Jahnke (@KnudJahnke) I Twitter - https___twitter.com_KnudJahnke

Hm… So what is the area that Hubble has actually covered in its long life? Nothing that a little bit of data can not solve!

In order to find out I queried the Hubble database with 140000 randomly selected positions on the celestial sphere and searched if the center of Hubble image, taken by one of its large field of view cameras, is found in the radius of 1.6 arcmin. If we find a match in a database, we proclaim this area “covered”, i.e. Hubble has observed it. We are not interested in multiple observations, dithering pointings etc… so multiple observations of same area count as one observation. Radius of 1.6 arcsec is chosen so that this area than corresponds to the field of view of 170×170 arcsec that Hubble cameras (WFPC, WFPC2, WFC3, ACS) have or have had. For instance ACS has 202×202 arcsec, while WFPC2 had 164×164 arcsec field of view. But, given that we do not know if the observers perhaps used smaller fields of views (observers could have for instance used near infrared channel on WFC3; information about mode of observations is not so readily available) it is better to be a bit conservative in our estimate.

Out of 140000 positions on the sky 182 produced a match, i.e. Hubble has covered around 182/140000 parts of the sky with imaging or roughly 50 square degrees (for comparison, Moon takes about 0.2 square degrees on the sky).

(Click to enlarge) Some of the found positions. This is with a bigger search radius then in the text (5 arcmin). Only overdensity I recognize is COSMOS field at Ra=10 and Dec = 2 degrees (very small cluster of points only a little bit to the left of the dashed line at that position).

Some of the found positions. This is with a bigger search radius then in the text (5 arcmin). Only overdensity I recognize is COSMOS field at Ra=10 and Dec = 2 degrees (very small cluster of points only a little bit to the left of the dashed line at that position).


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