One of Hubble’s most famous images is the Hubble Deep Field. 324 separate exposures taken over a ten-day span in December 1995 put a picture to the insane number of galaxies in the Universe.
Thousands of galaxies can be seen in this one image. Astronomers put the estimate of galaxies in the observable Universe at between 100 to 200 billion galaxies. Just galaxies. Now imagine all the stars and planets in each one of those. Astronomers put the number of stars in the Milky Way (our home galaxy) at about 100 thousand million stars!
Did You Know: Why do astronomers call it the ‘observable Universe?’ What we see is at the mercy of the speed of light. Because the Universe kicked off about 13.8 billion years ago, we can only see objects up to a certain distance from Earth. Galaxies exist beyond this “cosmological horizon.” The light from them just hasn’t reached Earth yet.
And today, an international team of astronomers believes the 100 to 200 billion figure is off. Way off. Using data from the Hubble Space Telescope along with other telescopes, the team led by Christopher Conselice estimates the old number is at least ten times too low.
The team poured over deep space images from Hubble, and several batches of published data. Deep space Hubble images were converted into 3D to give them accurate measurements of the number of galaxies at various points in the Universe’s history. After that, mathematical models filled in the gaps with galaxies we can’t see. For the numbers to add up, 90% of the galaxies in the observable Universe aren’t visible with today’s telescopes. They’re either too far away or too faint.
Conselice explains what the massive shift in the number of galaxies means. “It boggles the mind that over 90% of the galaxies in the Universe have yet to be studied. Who knows what interesting properties we find when we observe these galaxies with the next generation of telescopes.”
The James Webb Space Telescope will be one of the first to tackle these unseen galaxies.
Work continues on the James Webb Space Telescope
The James Webb Space Telescope has quite the mission ahead of it. Hubble gave us our first glimpses into deep space. James Webb will be tasked with peering even further. In April, the covers protecting the telescope’s golden mirrors were lifted for the first time since the primary mirror was completed.
It won’t just be looking for the earliest galaxies, though. It will also be tasked with increasing our understanding of how solar systems form.