2015 has been a pretty awesome year for space exploration. It has seen the likes of the New Horizons flyby of Pluto, private enterprises making some ground-breaking developments, and a whole manner of less "front-page news," which is nonetheless slowly but surely helping us increase our understanding of the vast intergalactic heavens.

Furthermore, public imagination and pop culture have both been reinvigorated with 20th century Space Race-like curiosity, with films like "The Martian" and "Star Wars: The Force Awakens" proving to be some of the most popular releases. 

Whether you have a fledgling interest or you're a full-blown space nut, nothing quenches our cosmic thirst more than beautiful images of space. But, these images aren’t simply screensaver-fodder or PR props for their relevant space agencies. Many of these images are the products of intense scientific exploration or express a landmark in the history of space travel. Beauty is truth, truth beauty, as they say.

1. Scott Kelly tweets from the International Space Station

Scott Kelly has been up on the International Space Station (ISS) since March, 2015, along with Russian cosmonaut Mikhail Korniyenko. Together they’ll spend just under a whole year in space to study long-term effects of spaceflight on the human body. In the meantime, aside from conducting numerous experiments, Kelly spends his time snapping some of the most colorful, beautiful and trippy images of space. There’s almost too many images to list, as Kelly uploads a new one at least once a day, so make sure you give him a follow on Twitter.

#EarthArt Patches of emerald, amber and purplish-blue woven over #MiddleEast like a colorful carpet. #YearInSpace pic.twitter.com/KcaqcCg8UY

— Scott Kelly (@StationCDRKelly) December 16, 2015

2. Saturn, her rings and tethys

This image was taken in visible light on August 18, 2015, by the Cassini spacecraft. With a simple monochrome effect, it shows the rings of Saturn sitting behind Tethys, one of Saturn’s moons, from over 296,000 kilometers (184,000 miles) away.

^{Image credit: NASA}

3. "Bloodstains" on Saturn's moon

Another image from the Cassini mission shows bizarre red streaks cutting across the icy surface of Saturn’s moon Tethys around early springtime this year. The image is made from numerous clear, green, infrared, and ultraviolet spectral filtered images to bring out subtle color wavelengths the human eye can’t normally see.

^{Image credit: NASA}

4. Flowing water on mars

Not only is this photograph visually stunning, it is also up there with one of the most exciting scientific discoveries of the year. The image, from NASA's Mars Reconnaissance Orbiter (MRO), shows a strong indication that Mars once had flowing water – suggesting the Red Planet had the ability to harbor life. The streaks trailing down those mountains appear to detail the path in which salty liquid water used to flow like Martian rapids.

^{Image credit: NASA}

5. Rosetta captures an comet gas outburst

This snapshot, showing a short-lived burst of gas from comet 67P/Churyumov-Gerasimenko, was captured by Rosetta's OSIRIS narrow-angle camera on July 29, 2015. Rosetta is the first spacecraft to orbit a comet, as well as the first spaceship to travel alongside a comet as it travelled in the direction of the Sun.  

^{Image credit: NASA/ESA}

6. Blue Origin and the age of private enterprise in space

Space exploration is no longer the domain of government agencies. With the likes of Elon Musk’s SpaceX and Amazon founder and CEO Jeff Bezos' company Blue Origins, private space companies have made some pretty big cosmic leaps in 2015.

In homage to this, here’s an image showing Blue Origin’s New Shepard spacecraft's historic launch from Van Horn, Texas, on November 24, 2015. This launch was the first to use a reusable space vehicle to travel out to space and successfully return to land intact. It was followed by SpaceX's arguably more impressive landing a month later.

^{Image credit: Blue Origin}

7. Hubble and the "butterfly" nebula

Hubble never ceases to amaze with their mouse mat-friendly imagery. This photograph shows the planetary nebula known as PN M2-9. And this twin jet nebula is not any old planetary nebula; it is a bipolar nebula comprised of two "suns." The motion of these two stars endow it with this rather beautiful butterfly-esque effect.

^{Image credit: NASA/ESA/Hubble}

8. Psychedelic Pluto

In July, after an epic nine-year journey, the New Horizons spacecraft finally reached humanity’s closest approach of Pluto, around 12,500 kilometers (7,800 miles) above its surface. Already, the fruits of this mission have been juicy, as well as providing some stunning images. Although this is a particularly funky image of this dwarf planet, false colors have been added to highlight differences in the soil composition.

^{Image credit: NASA}

9. The 1.5 billion pixel image of the Andromeda Galaxy

Right at the start of 2015, NASA and the European Space Agency (ESA) released a 1.5 billion pixel image of Andromeda, the Milky Way’s nearest major galactic neighbor. To truly do justice to this feat of imagery, you need to go to the Hubble site, where it is possible to zoom into patches of the galaxy.

^{Image credit: NASA/ESA}

10. Time-lapse of the Sun

2015 saw us celebrating five years of NASA's Solar Dynamics Observatory being in space. Overall, the project has captured more than 2,600 terabytes of data and 200 million images of the Sun in an attempt to better understand the Solar-Earth relationship. The observatory captures an image around every second; this video is just a little "best of" compilation.