Cosmos: Origin and Fate of the Universe

supernova 1987a 30 years later

Astronomy doesn’t adhere to humans and their timescales. Cosmic objects typically take thousands, millions, or even billions of years to evolve. But every so often, the universe gifts us an exception. A brilliant explosion that appeared in our sky over 30 years ago is one such present. This cosmic object, Supernova 1987A, marked the death of a massive star. The glowing ember lies 160,000 light-years from Earth in the Milky Way’s largest satellite galaxy, the Large Magellanic Cloud (LMC). In astronomical terms, that’s next door. This proximity means that our telescopes can resolve small changes in the evolving supernova remnant, changes that would be invisible if the object lay millions of light-years away. “It changes on human timescales,” says Penn State astrophysicist Kari Frank. That uniqueness is what keeps her and the…

pulsars at 50 still going strong

A little more than 50 years ago, an unassuming bit of “scruff” appeared in Jocelyn Bell Burnell’s radio telescope data. Although barely noticeable at first, the scruff quickly led to two Nobel Prizes, provided evidence that Albert Einstein’s general relativity was right, rode on humanity’s first interstellar vehicle, and became the inspiration for a watch, a car, and an album cover. The objects revealed by the scruff — dubbed “pulsars” — turned out to be smaller than a city but more powerful than the Sun. And if everything goes right, they soon will help us detect the most colossal events in the cosmos and even help us navigate to the stars. Despite its meteoric rise to fame, the pulsar had an unpromising start. In July 1967, Bell Burnell noticed quarter-inch-wide radio signal…

dark stars come into the light

LONG, LONG AGO, the universe looked very different than it does today. When the Big Bang was a recent memory and the first stars were forming and beginning to shine, the universe was much smaller. In this dense environment, a mysterious substance known as dark matter ran amok in infant galaxies. Scientists think that out of this rich environment, a new breed of star was born: dark stars. Dark stars are somewhat of a misnomer — they’re not actually dark. In fact, they’re likely some of the biggest and brightest stars in our universe. Yet no one has ever seen one. These giants, powered differently than the stars we see in the night sky, may reveal a lot about the true nature of our universe — that is, if scientists can…

why do galaxies align?

One of the most striking features of the distribution of matter in the universe is its filamentary appearance, with long, luminous strands of galaxies woven together into a vast cosmic web. Nowhere is this more evident than the Perseus-Pisces Supercluster. This colossal chain of galaxies snakes across more than 50° of the northern sky, fed by a network of smaller filaments that resemble tributaries flowing into a river. Embedded within these filaments are densely populated groups and clusters of galaxies. Between them lie immense voids. Our own Milky Way Galaxy resides in the outskirts of a similar structure known as the Laniakea Supercluster. (Laniakea means “immeasurable heaven” in Hawaiian.) Home to an estimated 100,000 galaxies, it’s a tangled knot of filaments stretching half a billion light-years from end to end. University of…

do all galaxies have dark matter?

Some 60 million lightyears from Earth — by some researchers’ estimate, anyway — a pair of strange galaxies is causing a cosmic stir. These island universes hold far fewer stars than your average galaxy. But it’s not the lack of stars that surprises astronomers. The bizarre galaxies, named NGC 1052-DF2 and NGC 1052-DF4 (or DF2 and DF4, for short), also seem to lack any significant amount of dark matter. Because the duo could be the first known galaxies without the substance, which accounts for 85 percent of the universe’s matter, news of DF2’s discovery in 2018 quickly spread throughout the astronomical community. If confirmed, such galaxies without dark matter would throw a wrench into our understanding of how galaxies form and evolve. “We thought that every galaxy had dark matter and that…

galaxy clusters the universe’s cosmic lenses

IT ALL STARTED with a simple idea. In 2012, Matt Mountain was the director of the Space Telescope Science Institute (STScI), the organization that manages the Hubble Space Telescope. He tasked a group of a dozen astronomers to come up with an observing project for the orbiting telescope that could reveal new insights into galaxy formation and the early universe. Many times before, scientists had pointed Hubble to seemingly empty patches of sky — small areas with no Milky Way stars — and collected light for several days. In these so-called deep fields, the space telescope revealed thousands of galaxies reaching to the edge of what humans could detect. It wasn’t a stretch to imagine that if every tiny, blank field of sky holds thousands of galaxies, our home Milky Way…