Space dominated the headlines in 2019 with stories documenting the first successful image of a black hole, or how a crashed Israeli spacecraft spilled thousands of tardigrades onto the moon.
But the universe is a pretty big place (pardon the understatement), and countless mind-bending phenomena happen there every day, whether or not they make it onto the nightly news. To give credit to the universe where it’s due, here are nine epic space discoveries you may have missed this year.
The cosmic web revealed
Every galaxy in the universe is a pit stop on a long highway of gas known as the cosmic web. Each road, or «filament,» on this intergalactic interstate is made of hydrogen left over from the Big Bang; where large quantities of hydrogen converge, clusters of galaxies appear in the dark sea of space. The web is too faint to see with the naked eye, but in October, astronomers photographed a piece of it for the first time ever. Using the faint ultraviolet glow of a distant galaxy as backlighting, the image shows blue strands of hydrogen crisscrossing through space 12 billion light-years away, connecting bright white galaxies in its path.
There is a violent clash unfolding at the frontier of our solar system. Billions of miles from the solar system’s center, crackling solar wind collides with powerful cosmic rays at a boundary called the heliopause. When NASA’s twin Voyager probes passed through the region and entered interstellar space last year, astronomers saw that the heliopause is not just a symbolic boundary; it’s also a physical wall of soupy plasma that deflects and dilutes the worst of the incoming radiation. This plasma «shield,» as it’s described in a Nov. 4 study, may deflect about 70% of cosmic rays from entering our solar system. You could call it the shield that guards the realms of men. (You won’t find White Walkers on the other side, but you will find some white dwarfs.)
Radio bubbles in the galaxy’s gut
The Fermi Bubbles are twin blobs of high-energy gas ballooning out of both poles of the Milky Way’s center, stretching into space for 25,000 light-years apiece (roughly the same as the distance between Earth and the center of the Milky Way). The bubbles are thought to be a few million years old and likely have something to do with a giant explosion from our galaxy’s central black hole — but observations are scarce, as they are typically only visible to ultrapowerful gamma-ray and X-ray telescopes. This September, however, astronomers detected the bubbles in radio waves for the first time, revealing large quantities of energetic gas moving through the bubbles, possibly fueling them to grow even larger, according to the scientists’ report in the journal Nature.
At the center of our galaxy is a supermassive black hole. This object’s monstrously powerful gravity is sort of like the glue that holds the Milky Way together. Earlier this year, researchers discovered that the glue is letting off fumes. In a March 20 study, astronomers looked at the X-rays seeping out of the galaxy’s center and discovered two «chimneys» of superhot plasma stretching for hundreds of light-years in either direction. The giant smokestacks seem to be connecting the central black hole to the bottom of the Fermi Bubbles. It’s possible that these chimneys are fueling the bubbles’ slow but steady growth.
Planet in a dead star’s thrall
When a typical sun runs out of fuel and collapses, it may become a white dwarf — the compact, crystalline corpse of a star. If that star had any planets orbiting around it, chances are they were either obliterated in the star’s final growth spurt (Earth will likely be engulfed by our sun in its final years) or sucked up and destroyed by the white dwarf’s intense gravity. However, in early December, astronomers discovered an intact planet orbiting a white dwarf star for the first time ever. Spotted about 2,040 light-years from Earth, the white dwarf system seems to be emitting a strange combo of gases that could be a Neptune-like planet slowly evaporating as it circles the dead sun once every 10 days. The study adds major evidence to the theory that dead stars can host planets (at least temporarily).