On May 20, 1990, officials at NASA instructed the Hubble Space Telescope to open its lens for the first time and gaze upon the light of the cosmos. The black-and-white image it captured, a revelation in detail compared to ground-based telescopes, would mark the beginning of more than 1.3 million observations (totaling over 150 terabytes of information) into the unexplored depths of our universe.

"Hubble has flattened the world for astronomy and for the public when it comes to science," Matt Mountain, president of the Association of Universities for Research in Astronomy, told NPR. "Everybody feels that they can understand what Hubble is doing by logging onto the website and downloading a picture."

In celebration of the 30th anniversary of the Hubble Space Telescope's launch into orbit, NASA and the European Space Agency (which contributed components to the nearly 44-foot-long telescope), have curated a digital 2020 calendar called "Hidden Gems." True to its name, the calendar's 12 images (whittled down from 100 through social media voting), comprise lesser-known but beautiful cosmic wonders captured over Hubble's three decades in space.

Below are just a few highlights from the calendar, available as a free download, to keep you in awe of our universe throughout 2020.

January

In 2014, astronomers conducted a study called the Ultraviolet Coverage of the Hubble Ultra Deep Field project.
In 2014, astronomers conducted a study called the Ultraviolet Coverage of the Hubble Ultra Deep Field project. (Photo: NASA/ESA [public domain])

In 2014, after 841 orbits of telescope viewing time, astronomers released an image taken from a small area of space in the constellation Fornax that contains an estimated 10,000 galaxies. Called the Ultraviolet Coverage of the Hubble Ultra Deep Field project, the image is composed of light stretching back 13.2 billion years.

"The XDF is the deepest image of the sky ever obtained and reveals the faintest and most distant galaxies ever seen. XDF allows us to explore further back in time than ever before", Garth Illingworth of the University of California at Santa Cruz, principal investigator of the Hubble Ultra Deep Field 2009 (HUDF09) program, said in a statement.

May

A 2011 snapshot features the fine detail and exceptionally perfect spiral structure of NGC 634, located 250 million light years away in the constellation of Triangulum.
A 2011 snapshot features the fine detail and exceptionally perfect spiral structure of NGC 634, located 250 million light-years away in the constellation of Triangulum. (Photo: NASA/ESA [public domain])

Looking like something straight out of a science fiction film, NGC 634 is a stunningly beautiful spiral galaxy located some 250 million light-years away from Earth. Astronomers turned Hubble's gaze on this cosmic wonder in 2008, a little over a year and a half after a supernova in the region briefly rivaled the brilliance of its entire host galaxy. As a whole, NGC 634 is estimated to span 120,000 light-years across.

December

The Hubble telescope revealed a rainbow of colours in the dying star IC 4406 in a beautiful 2002 image.
The Hubble telescope revealed a rainbow of colours in the dying star IC 4406 in a beautiful 2002 image. (Photo: NASA/ESA [public domain])

ICC 4406, also dubbed the "Retina Nebula," is a colorful dying star captured by Hubble in a series of observations between 2001 and 2002.

"If we could fly around IC 4406 in a starship, we would see that the gas and dust form a vast donut of material streaming outward from the dying star," says NASA of the object, which is roughly 1,900 light-years away. "From Earth, we are viewing the donut from the side. This side view allows us to see the intricate tendrils of dust that have been compared to the eye's retina."

Astronomers estimate that the hot gasses flowing from ICC 4406 will eventually cease in a few million years, leaving behind only a fading white dwarf at its center.

April

This NASA/ESA Hubble Space Telescope image features the star cluster Trumpler 14. One of the largest gatherings of hot, massive and bright stars in the Milky Way, this cluster houses some of the most luminous stars in our entire galaxy.
This NASA/ESA Hubble Space Telescope image features the star cluster Trumpler 14. One of the largest gatherings of hot, massive and bright stars in the Milky Way, this cluster houses some of the most luminous stars in our entire galaxy. (Photo: NASA/ESA [public domain])

Home to some of the most luminous objects in our Milky Way galaxy, Trumpler 14 is a young star cluster dating back 300,000-500,000 years and located approximately 8,980 light-years from Earth.

The most curious thing about the above image, captured by Hubble in 2016, is the dark splotch located close to the center of the cluster. While this appears to the naked eye some kind of photographic aberration, it's actually a cosmic phenomenon known as a Bok globule. These small dark nebulae, containing dense cosmic dust and gas, are some of the coldest objects in the universe and are believed responsible for star formation.

November

Hubble has taken this stunning close-up shot of part of the Tarantula Nebula.
Hubble took this stunning close-up shot of part of the Tarantula Nebula. This star-forming region of ionised hydrogen gas is in the Large Magellanic Cloud, a small galaxy next door to the Milky Way (Photo: NASA/ESA [public domain])

First discovered in the mid-1700s by French astronomer Nicolas-Louis de Lacaille, the Tarantula Nebula is a star-forming region of ionized hydrogen gas located in the Large Magellanic Cloud. It's luminosity is so exceptional that if it were located as close as the Orion Nebula (about 1,300 light-years) its brilliance would cast shadows on Earth.

The Tarantula Nebula, which spans 1,000 light-years across, is also home to the universe's heaviest known star. Called R136a1, astronomers studying Hubble imagery believe it's more than 250 times the size of our own sun.

One more decade?

The The Hubble Space Telescope as it appeared in March 2002 after upgrades performed by the crew of the Space Shuttle Columbia.
The The Hubble Space Telescope as it appeared in March 2002 after upgrades performed by the crew of the Space Shuttle Columbia. (Photo: NASA/ESA [public domain])

While NASA's service contract for Hubble is good through June 2021, officials fully expect the telescope to remain operational through the middle of this decade — and perhaps longer.

"Right now, all of the subsystems and the instruments have a reliability exceeding 80 percent through 2025," Hubble mission head Thomas Brown of the Space Telescope Science Institute in Maryland told Space.com in January 2019.

Once Hubble's time finally comes to an end and successors like the James Webb Space Telescope become operational, NASA will use an onboard rocket to deorbit the spacecraft. It will then break up in Earth's atmosphere, with the largest surviving pieces likely landing in the ocean graveyard known as Point Nemo.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.