This spectacular image, captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys, shows part of the sky in the constellation of Tucana.
This Hubble image shows a small portion of the southern sky in the constellation of Tucana. Image credit: NASA / ESA / Hubble.
While this image contains hundreds of distant stars and galaxies, one vital thing is missing — the object Hubble was actually studying at the time.
And this is not because the target has disappeared.
Hubble’s Advanced Camera for Surveys (ACS) actually uses two detectors: the first captures the object being studied — in this case an open star cluster known as NGC 299 — while the other detector images the patch of space just ‘beneath’ it. This is what can be seen here.
Technically, this picture is merely a sidekick of the actual object of interest — but space is bursting with activity, and this field of bright celestial bodies offers plenty of interest on its own.
It may initially seem to show just stars, but a closer look reveals many of these tiny objects to be galaxies.
The spiral galaxies have arms curving out from a bright center.
The fuzzier, less clearly shaped galaxies might be ellipticals.
Some of these galaxies contain billions of stars, but are so distant that all of their starry residents are contained within just a small pinprick of light that appears to be the same size as a single star.
The bright blue dots are very hot stars in our own Milky Way Galaxy, sometimes distorted into crosses by the struts supporting Hubble’s secondary mirror.
The redder dots are cooler stars, possibly in the red giant phase.
This image is made up of observations from the ACS instrument in the near-infrared and optical parts of the spectrum.
Two filters — the green filter F555W and the near-infrared filter F814W — were used to sample various wavelengths.
The color results from assigning different hues to each monochromatic image associated with an individual filter.
