Astronomers have made great strides this year in their quest to observe the universe. Here’s a recap of astronomy news in 2018.

It has been an exciting year for space missions. As one launched toward the inner solar system in an epic quest to touch the Sun, another left the solar system entirely to touch interstellar space — a whopping 18 billion kilometers from home. Both will shed light on extreme and distant environments. Meanwhile, other missions are focused on environments more like home — working toward better understanding Earth and the planets like it.

In April, for example, the TESS mission launched to study nearby exoplanets, increasing the chances that astronomers might soon find more habitable abodes. And in late November, NASA’s Insight lander reached Mars in the first mission to study the planet’s interior. That’s particularly exciting given that two findings this year have increased the odds that the Red Planet might have once hosted life: The first found organic molecules within ancient rocks and the second discovered a sub-surface briny lake.

While these missions highlight the potential for future discoveries, the year has also hosted an array of sad endings. We said goodbye to the beloved scientist Stephen Hawking — who helped uncover many of the secrets within black holes — and the Kepler Space Telescope — which revealed thousands of alien worlds. Yes, it has been quite a year. Below are the top 10 stories from 2018.

LIGO: The Gift That Keeps on Giving

In December, scientists identified four more ghostly signals from distant pairs of black holes that swirled in toward each other and collided — raising the total number of gravitational-wave detections to 11. Not only was the announcement the largest batch of detections released at once, but one event was the most distant and most powerful black-hole merger yet discovered. It occurred 5 billion years ago when two huge black holes merged into an 80-solar-mass behemoth, unleashing the energy equivalent to 5 solar masses in the form of powerful gravitational waves.

Voyager 2 Leaves the Solar System

On December 5th Voyager 2 entered interstellar space — making it the second probe in history to travel so far beyond home, after Voyager 1. Astronomers noted the event not by the probe’s distance (a whopping 18 billion kilometers from home) but by a drop in the solar wind. The Sun sends a steady breeze of charged particles far past Neptune, but eventually that wind gives way to the interstellar plasma that fills the galaxy. So, when the plasma detector onboard Voyager 2 recorded a significant drop in the speed of the solar wind, mission scientists knew that the probe had officially entered interstellar space. At their current rate, the Voyagers will encounter the inner edge of the Oort Cloud — the icy shell of debris surrounding our solar system — in roughly 300 years.

Insight Lander Reaches Mars

In late November NASA’s Mars Insight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander touched down on the Red Planet. It’s NASA’s eighth successful landing on Mars and the first dedicated geophysical mission.

Insight will chronicle “Mars-quakes” and other geological activity in order to answer several questions about the planet’s interior. Scientists want to know, for example, how similar the planet’s inside is to other rocky worlds. Soon, the lander will drill a mole into the planet’s surface one millimeter at a time. Then, after 30 or 40 days of drilling, Insight will sit quietly in order to take dedicated seismic measurements and assess our neighbor’s activity.

Astronomers Glimpse a Black Hole’s Event Horizon

While using the GRAVITY instrument on the Very Large Telescope Interferometer in Chile, astronomers detected three bright flares from near our galaxy’s central supermassive black hole, Sagittarius A*. Each flare lasted between 30 and 90 minutes and raced around the black hole at 30% the speed of light. As such, astronomers suspect that the flares originated within the puffy disk that slowly feeds the black hole. It’s a finding that will allow them to make precise tests of gravity in one of nature’s most extreme environments.

Scientists “Set Foot” on an Asteroid

In early October, the Mobile Asteroid Surface Scout (MASCOT) mission successfully landed on the tiny asteroid 162173 Ryugu. It was the first mission to explore the surface of an asteroid on site, traversing the tiny rock for three days and two nights in order to better assess the early days of solar system formation.

But it wasn’t the only asteroid scientists explored this year. A month later, NASA’s Osiris-REX spacecraft arrived at Bennu and quickly revealed that water once soaked its rocks. Osiris-REX will go into orbit around Bennu on December 31st of this year — ultimately grabbing a sample of material to return to Earth in 2023.

A Space Probe Launches to “Touch the Sun”

Late this summer, the Parker Solar Probe launched from Cape Canaveral on a mission that will unlock a number of secrets about our beloved host star. It will carry a suit of instruments closer to the Sun than ever before — dipping down into the lower solar corona in order to understand the origin and acceleration of the solar wind as well as the dynamics of the coronal magnetic field. It won’t be easy. The daring spacecraft will have to fight against the sun’s intense wind and sizzling heat. But, if successful, it will open a new window on solar physics.

The Potential for Martian Life Increases

Two exciting finds this year increased the odds that the Red Planet once contained the necessary ingredients for life. First, the Curiosity rover detected organic molecules in ancient rocks. While these molecules don’t have to be made by life, life does make and use some of them (such as sugars and amino acids). Then, a second instrument discovered evidence for present-day liquid water on Mars — or, more specifically, a salty sub-surface lake. Both are promising finds.

Gaia Maps the Milky Way

The Gaia space satellite released its second batch of data in late April, including precise parallaxes (and therefore distances) for more than 1.3 billion stars and the positions and brightnesses of almost 1.7 billion stars in total. That second number makes up slightly more than 1% of all the stars in our galaxy — thus providing a detailed map of our local neighborhood.

But that’s not all. Gaia has also observed roughly 14,000 known solar system objects, most of them asteroids, and more than 500,000 quasars. The final data release is scheduled for late 2022.

One Exoplanet Mission Ends, Another Begins

It has been an exciting year for exoplanet research. On April 18th, the Transiting Exoplanet Survey Satellite (TESS) launched aboard a SpaceX Falcon 9 rocket in a quest to search for exoplanets around bright stars. The mission began observations in the nick of time: On October 30th, the Kepler mission ran out of fuel, thus ending a nine-year mission that detected more than 2,600 planets along with thousands more candidate worlds. It’s safe to say that Kepler sparked an entirely new field of research that TESS will continue — potentially leading to the discovery of alien life one day.

Stephen Hawking, Renowned Physicist, Passes Away

On the morning of March 14, 2018, professor Stephen Hawking passed away at the age of 76. He had defied expectations, living decades longer than expected after his 1963 diagnosis with Lou Gehrig’s disease, building a brilliant career in physics. He is perhaps most famous for postulating that black holes are not actually black but radiate a small amount of heat and ultimately evaporate. But he was also a beloved public figure — in part thanks to his book A Brief History of Time, which sold 10 million copies in more than 40 languages, and in part thanks to his wicked sense of humor.