Liftoff (9/8/22)

Welcome, readers, to the first edition of Parallax! This is Rachael Zisk, Payload’s staff reporter, speaking from Parallax mission control. I come in peace, bearing news from the cosmos. We at Payload are thrilled that you’ve jumped on the rocket ship early.

In astronomy, a parallax is the visual effect that occurs when viewing a target object from two different vantage points. In this newsletter, we’re going to dive into the mysteries of the universe, constantly gaining new perspectives and puzzling out the complicated bits.

From the outset, dear readers, I want to emphasize that this is a two-way street. Send me your feedback and cosmic curiosities. I’ll try to answer all your burning questions about the universe. Reply to this email at any time and let me know what you’re thinking—you might even see expert input on your questions in upcoming editions.

And with that…let’s dive in 🌌

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A New Kind of Galaxy Death

This is the way a galaxy dies. Not with a bang but a whimper.

Or, at least, that’s the case for a galaxy identified in a paper released last week. The study challenges the conventional wisdom that galaxy death—which happens when galaxies stop forming new stars—occurs alongside major cosmic events like supernovae or black hole accretion. The galaxy identified in this project, SDSS J1448+1010 (catchy!), died in a much slower way that has never been witnessed by astronomers before.

In this case, a collision between two galaxies sent the pair’s reserves of cold gas, an amount equal to 10 billion times the mass of our Sun, streaming out into space, stopping the process of star birth.

An anomaly in the data: The researchers on the project sought to answer the question of why galaxies die. They pulled from a larger survey of distant galaxies to identify a group that looked like they had been forming stars fairly quickly for a long time, then suddenly stopped.

“It's really kind of rare for a galaxy to jump off a cliff and stop forming stars really suddenly,” said Justin Spilker, an astronomer at Texas A&M and lead author on the paper. Usually, he said, galaxies are “perfectly happy” to keep slowly forming stars over time.

Of the subset of galaxies identified in the larger survey, Spilker and his team homed in on one: a galaxy that had a long tail of gas extending far from its outer edge. “This particular galaxy that we found—I have looked through a lot of data from radio telescopes in my life, and this was like the weirdest thing that I had ever seen,” said Spilker.

A star is born: Stars form in large clouds of cold gas. Over time, knots of denser gas begin to form, and the bigger these knots get, the stronger their gravity becomes. As these knots collapse in on themselves, they cool and condense faster and faster until the energy released by gravitational collapse and intense pressure causes the dense cloud to heat up and hydrogen atoms to begin to fuse in the core.

Seeing the cold universe: To see that cold gas, scientists need to use radio telescopes, which allow more detailed data from the “cold universe,” per Spilker. For this project, the team used the ALMA telescope in Chile to observe the strange tail of gas alongside the galaxy. To figure out what was causing this tail to form, though, more information was needed.

Complementary observations from Hubble allowed the team to see in more detail what was going on in the galaxy. The space telescope’s imagery revealed the structure of the collision, showing that two galaxies had nearly completed merging into one in a process that takes about a billion years.

The telescopes had to work in tandem for these observations to be possible, Spilker said. “It was hard to tell that it was a galaxy crash just from the radio telescope. And we wouldn't really have known that there was gas in any interesting place just from Hubble.”

What’s next? Now that the team has found that it’s possible for a galaxy merger to end star formation, the next question to answer is whether this phenomenon is common in the universe. The hunt for other slowly merging galaxies that might fit this description is underway.

Share this story with someone who can pick out a T.S. Eliot reference a light-year away:

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Other News from the Cosmos

Since this is our first edition, we’ve got literally the whole history of the universe to pull from, but for the sake of brevity we’ll err on the side of the recent.

• DART, or the Double Asteroid Redirection Test, is well on its way to smashing into an asteroid to see if it can change the larger object’s orbit. The NASA team has confirmed the orbit of the target asteroid, Dimorphos, and impact is expected on Sept. 26.

• Perseverance found green sand on the Red Planet. The color is caused by a greenish mineral called olivine, and its presence indicates that the sand was once wet.

• Europa Clipper, a NASA probe destined to launch in 2024 for the eponymous giant moon of Jupiter, is being put together at JPL’s Spacecraft Assembly Building.

• EP-WXT Pathfinder, an experimental X-ray module from the Chinese Academy of Sciences, has returned its first widefield images.

• Diamond rain might be fairly common on other planets. Researchers at Stanford’s SLAC National Accelerator Laboratory simulated the conditions needed to rain down nanodiamonds in a lab on Earth.

• Forensic techniques can be used to figure out where asteroids struck the Earth in the distant past, per a study from the University of Exeter.

Deeper Dives

A little something to hold you over ‘til next week.

🏝️ What’s going on in there? Black holes can seem to defy the laws of physics. Stephen Hawking first showed how black holes can dissipate into strange clouds of radiation, seemingly with no trace of the matter they had pulled in with their intense gravity. Ahmed Almheiri, a theoretical physicist at NYU Abu Dhabi, wrote about this phenomenon for Scientific American, detailing how a black hole’s inner “island” secretly residing on the outside could account for this apparent loss of matter.

🧊 Exploring the Oort cloud: At the outer edge of our solar system, there’s a mysterious band of icy debris that is so dim and slow-moving that we can’t see it, even with our most powerful telescopes. Astronomy Magazine explored what could be lurking at the outer boundaries of our home system.

👽 Martian invasion: NASA and ESA are hoping to ferry Mars rock samples back to Earth by the mid-2030s, but such an endeavor doesn’t come without its risks. One of those risks, though unlikely, is that those Martian rock samples could contain unknown pathogens. The NYT dug into the precautions that the space agencies are taking both to protect the samples from Earthly contamination and to save us from what might accompany the rocks on the journey home.

The View from Space

Last week, JWST peered into the Phantom Galaxy, a ghostly, swirling collection of stars and dust. In this image, the blue specks are stars, and the red spirals are trails of dust. Where the red swirls look brighter and pinker, stars are being born.