Image: Hubble finds a field of stars

This picture from the NASA/ESA Hubble House Telescope exhibits a globular cluster known as NGC 1651. Like one other latest globular cluster picture, NGC 1651 is about 162,000 light-years away within the largest and brightest of the Milky Way’s satellite galaxies, the Giant Magellanic Cloud (LMC).

One notable characteristic of this picture is that the roughly 120-light-year diameter globular cluster practically fills the whole body. In distinction, different Hubble pictures characteristic total galaxies—which will be tens or tons of of hundreds of thousands of light-years in diameter—that additionally roughly fill the entire picture.

A standard false impression is that Hubble and different massive telescopes observe wildly in a different way sized celestial objects by zooming in on them, as one would with a specialised digicam right here on Earth. Whereas small telescopes may need the choice to zoom out and in to a sure extent, massive telescopes don’t. Every telescope’s instrument has a set ‘subject of view’ (the dimensions of the area of sky that it may well observe in a single remark).

For instance, the ultraviolet/seen gentle channel of Hubble’s Vast Discipline Digital camera 3 (WFC3), the channel and instrument that collected the info used on this picture, has a subject of view roughly one-twelfth the diameter of the moon as seen from Earth. When WFC3 makes an remark, its subject of view is the dimensions of the area of the sky that it may well observe.

The rationale that Hubble can observe objects of such wildly completely different sizes is two-fold. First, the space to an object will decide how large it seems from Earth, so total galaxies which might be comparatively far-off would possibly take up the identical quantity of space within the sky as a globular cluster like NGC 1651, which is comparatively shut by.

In actual fact, there is a distant spiral galaxy lurking on this picture, instantly left of the cluster—although undoubtedly a lot bigger than this star cluster, it seems sufficiently small right here to mix in with foreground stars! Secondly, picture processors can sew collectively a number of pictures spanning completely different elements of the sky right into a mosaic to create a single picture of objects which might be too large for Hubble’s subject of view.