A recent learning was that Edwin Hubble did research at Caltech starting back in the early 1930s. Dr. Hubble, according to his Wikipedia page, played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. He discovered an asteroid known as 1373 Cincinnati. More significantly, he deepened our understanding of an expanding universe.
The orbiting telescope named in Dr. Hubble’s honor settled into its low earth orbit at around 335 miles and became operational in May of 1990. The Hubble has provided a stream of mind-blowing photos, giving us spectacular images of nebulae and galaxies and our own planetary neighbors. This instrument has led scientists to deeper understandings of, among other things, the rate of the universe’s expansion- work for which Dr. Hubble himself helped lay the foundation.
Of all the pictures from Hubble, the first one that made my jaw drop is the Deep Field North, constructed from a series of observations, over a ten-day period, of a minuscule section (one 24-millionth) of the sky in Ursa Major (the Big Dipper), with an equivalent angular size of viewing a tennis ball from a distance of 100 meters, or roughly 110 yards. I seem to recall another analogy comparing this to looking at a dime edgewise from a distance of 70 feet. There have been other Deep Field composites since- the Ultra Deep Field and Extreme Deep Field- but when the first one was made public, it was an attention-getter.
According to Wikipedia, the field of view is so small that only a few foreground stars in the Milky Way lie within it, which means that almost all of the 3000 objects in the image are GALAXIES! Galaxies contain anywhere from hundreds of millions to trillions of stars. The distance across galaxies is measured in light years, sometimes thousands of light years.
A light year is a unit of astronomical distance- the distance light travels in one year at a speed of 186,000 miles per second, or 671 million miles per hour…
Almost 6 trillion miles.
It’s fun trying to get your head around that.