The supermassive black hole at the heart of the neighboring galaxy M87 has the mass of 6.6 billion suns. It's the biggest black hole to be precisely measured, and it's us our best shot at really seeing these strange objects.
The internet is burning up with the news that the zodiac has been rearranged. There's a 13th sign, Ophiuchus, and people who think they're Virgos are actually Leos. What happened here? We talked to the astronomer who caused the fuss.
Saturn's moon Iapetus has a gigantic ridge running along its equator that's twice the height of Mount Everest and covers 75% of the moon's equator. And its existence points to something stranger still: Iapetus once had its very own moon.
Saturn's rings are among the most iconic sights in the solar system, but where did they come from? Long ago, an icy moon was ripped apart by Saturn's gravity, creating rings once a 100 times bigger than they are now.
The discovery of a fourth gas giant around the star HR 8799 doesn't seem like that big a deal, but it's become the latest flashpoint for a highly controversial and often intense debate about how gas planets are born.
Far away in the frozen outermost depths of our solar system, there might be a hidden planet four times the size of Jupiter. This secret companion to the Sun could be responsible for sending comets into the inner solar system.
We've discovered 500 exoplanets, most of them gas giants even bigger than Jupiter. But some, known as super-Earths, are rocky worlds only a bit larger than our planet, and now we've discovered the cloudy atmosphere of one of these worlds.
Check out that extra-bright galaxy towards the top of this image. That's an elliptical galaxy, which are among the largest galaxies in the universe. And now scientists believe these galaxies hold five to ten times more stars than previously thought.
Large groups of galaxies come together to form clusters, and those clusters are linked together by vast streams of hot gas known as filaments. These intergalactic links reach temperatures well over a million degrees and are almost completely invisible...until now.
At the furthest edges of our solar system lies the vast Oort Cloud, a hypothetical giant shell full of billions of frozen comets. Formed 4.5 billion years ago, the cloud is a frozen museum of the chemistries of neighboring stars.
The Sun was born 4.6 billion years ago inside a nebula that likely gave birth to a thousand other stars. So what happened to the Sun's siblings? The search continues, but they could be practically anywhere in the Milky Way.
Earth actually shares its orbit with a huge ring of dust particles. Alien astronomers would likely notice the dust ring long before seeing Earth itself, which could mean the best way to find alien planets is to look for dust.
Brown dwarfs are objects that weren't quite massive enough to become stars. Stuck somewhere between lame stars and weird planets, brown dwarfs lead a solitary existence...and this newly-discovered brown dwarf could be the saddest of them all.
Gamma-ray bursts are the most powerful (and mysterious) explosions in the universe, shooting massive concentrated jets of hot plasma that are way too powerful to come from an ordinary supernova. And they might be the birth pangs of black holes.
Pluto lost its status as a planet because of the discovery of Eris, another Kuiper Belt object that was slightly larger. But now Pluto has put Eris back in its place.
The universe is thought to have consistently become cooler over time. But about 1.5 billion years ago, the cosmos overheated in a massive temperature spike, caused by runaway black holes that pumped tons of ultraviolet radiation into the universe.
The most massive neutron star ever discovered has been found 3000 light-years away. The tiny star is twice as massive as the Sun but its diameter is mere miles across. This discovery confirms these stars really are made of neutrons.
We can determine the atmospheres of exoplanets and the composition of galaxies billions of light-years away...but if you ask astronomers to weigh a star, they're stumped. Now there's an awesomely circuitous way to do it, but we'll need some exomoons.
Low-mass stars like our own Sun start life as "first cores," which is the earliest point where gas and dust clump together to form a coherent structure. They're an essential part of stellar evolution, but we've never seen one...until now.
Mars's thin atmosphere is now about 95% carbon dioxide, but when the planet's atmosphere is only 1/200th the size of Earth's, that doesn't mean very much. Now deeply buried minerals reveal Mars once had nearly Earth-like levels of carbon dioxide.