Anti-stars (7/20/23(

Good afternoon. Happy Moon Day! Today we’re celebrating the 54th anniversary of humankind’s first steps on the lunar surface. I don’t know about you, but I’m pretty psyched for the coming era of Moon exploration.

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The Dark Side of Star Formation

Our Sun, along with every other star we can see in the sky, is powered by atomic fusion, where two lighter atoms combine to form a heavier atom, releasing a burst of energy in the process.

But that may not be the only way to form a star.

In a study published this week in the Proceedings of the National Academy of Sciences, researchers describe a potential new type of star that uses dark matter instead of atoms to power the furnace at its center. These “dark stars” can be several million times more massive than the Sun and potentially billions—with a B—times brighter.

“When we look at the James Webb data, there are two competing possibilities for these objects,” Katherine Freese, director of the Weinberg Institute for Theoretical Physics and a coauthor on the paper, said in a release. “One is that they are galaxies containing millions of ordinary, population-III stars. The other is that they are dark stars. And believe it or not, one dark star has enough light to compete with an entire galaxy of stars.”

Looking back in time: Like many discoveries borne of JWST data, researchers found evidence for dark stars while analyzing data that’s traveled to us from the early universe. The three candidates for dark stars identified in the paper were originally cataloged as huge protogalaxies from a few hundred million years after the Big Bang in the JWST Advanced Deep Extragalactic Survey (JADES).

Before going through this catalog, Freese and her team had come up with a model for what their theorized dark stars could look like. The steps:

• Start with a huge clump of dark matter accompanied by a cloud of hydrogen and helium

• The gas cloud would then cool, pulling dark matter toward the center as it condensed

• As they condensed, dark matter particles would “annihilate,” generating heat that would keep the gas diffuse and prevent a standard stellar core from forming

• The result: a huge, puffy, extremely bright object—a “dark star.”

Aside from their size and brightness, dark stars would also differ from normal, Sun-like stars in the distribution of power. Rather than residing in a concentrated core, dark matter annihilation is theorized to take place across the whole volume of the star.

Keep up the hunt: The concept of a dark star powered by dark matter is still theoretical (as, for that matter, is “dark matter” itself). The objects identified by the researchers may turn out to be regular old galaxies in the end, and their strange signatures explained by other methods—such as an adjustment to the standard model of cosmology, which, as it’s currently written, suggests that the early universe should not contain galaxies as large and fully-formed as some that have been observed.

“It’s more likely that something within the standard model needs tuning, because proposing something entirely new, as we did, is always less probable,” Freese said. “But if some of these objects that look like early galaxies are actually dark stars, the simulations of galaxy formation agree better with observations.”

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Between 2000 and 2022, the number of commercial Earth observation satellites in orbit increased from roughly 10 to over 1,000.

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Other News from the Cosmos

• Two planets may have been spotted sharing an orbit around a star—a phenomenon theorized in the universe but not yet observed.

• JWST detected carbon-rich dust grains in the early universe, ~1B years after the Big Bang.

• A magnetar that releases ultra-long pulses of energy has been spotted for the first time by a team of scientists at the US Naval Research Laboratory.

• No dark matter appears to reside in the unusual galaxy NGC 1277, a “relic galaxy” that appears to have had no interaction with its galactic neighbors in its history.

• A methalox (that’s methane and liquid oxygen)-fueled rocket, China’s Zhuque-2, has reached orbit for the first time.

• Rogue planets—i.e., planets that float alone through space, not orbiting a star—may be as much as 20 times more abundant in the galaxy than tethered planets.

• BepiColombo, an ESA/JAXA planetary probe mission, found that electron rain can set off X-ray auroras on Mercury.

• Juno, NASA’s Jupiter craft, frequently passes through huge, swirling waves at the boundary of the solar wind and the planet’s powerful magnetosphere.

• VIPER, NASA’s ice-hunting lunar rover scheduled for launch next year, is currently being constructed at the Johnson Space Center.

• Psyche’s flight software is tested and ready to go ahead of the craft’s launch to the eponymous asteroid planned for October.

• A “two-faced” star—one made of hydrogen on one side and helium on the other—was discovered by the Zwicky Transient Facility (ZTF).

The View from Space

Happy 54th birthday to the Apollo 11 Earthrise.