How did dark matter shape the universe? This physicist has ideas
Theoretical physicist Tracy Slatyer proposes new scenarios for dark matter and helped discover the Fermi bubbles.
At age 12, Tracy Slatyer felt sorry for a book. She read a newspaper article about how quite tons of individuals were buying A Brief History of Time by Stephen Hawking. “But then … no person turn into truly reading it,” she says. “People were just leaving it on their coffee tables.”
Determined to rectify this wrong, Slatyer obtained a duplicate and diligently read each page. The famous physicist’s renowned text revealed to her “that math turn into in some sense an expressive language for describing how things in actuality work,” she says. “That, to me, turn into exciting.”
On the moment, Slatyer, a theoretical physicist at MIT, uses her mathematical aptitude to dream up new ideas about dark matter. The mysterious substance makes up around eighty five percent of the matter contained in the universe. Yet it has consistently eluded scientists’ attempts to pin it down. Slatyer tries to figure out what dark matter may well be fabricated from, how it would interact with itself or anything else and, most significant, the effects of those interactions.
Physicists know dark matter exists because they could see its gravitational influence on galaxies, galaxy clusters and the general evolution of the universe. Beyond that, there are few clues to work with. Slatyer has helped imagine the myriad ways that dark matter may maybe leave some subtle signature on the subject material of reality that may show up in observations.
Among scientists doing such work, “I don’t think there’s been any one who’s been more impactful,” says Dan Hooper, a physicist on the University of Chicago. “She’s as big a deal as I can make her out to be.”
Discovering the Fermi bubbles
Born contained in the Solomon Islands, Slatyer grew up in Canberra, Australia. After her stumble upon with Hawking’s book, she knew she desired to learn about physics. While in graduate school at Harvard University contained in the 2000s, she met physicist Douglas Finkbeiner, who turn into investigating mysterious signals on the Milky Way’s center.
A research satellite had noticed odd excesses of positrons, the electron’s antiparticle, and high-energy photons typically often called gamma rays that couldn’t be explained with conventional theories. Together, Slatyer and Finkbeiner began having a look more deeply at a sort of self-annihilating dark matter that may possibly address the mystery. Of their particular model, this dark matter would leave in the back of electrons and positrons, which may interact with starlight to create gamma rays.
In 2008, NASA launched the Fermi Gamma-ray Space Telescope, which offered unprecedented views of high-energy photons emanating from the galactic plane. If dark matter turn into indeed self-annihilating, it'd show up in Fermi’s observations. The next year, Slatyer and Finkbeiner used Fermi’s public data to hunt for the stuff.
“We analyzed the data and saw this big fuzzy glow north and south of the galactic center,” Slatyer recalls. “So we’re like, ‘Victory!’”
But the more they and every other of Finkbeiner’s students, Meng Su, checked out the signals, the more they realized that this wasn’t dark matter. Fermi’s images revealed a giant hourglass figure that stretched 25,000 light-years above and below the Milky Way’s plane. Dark matter is believed to be present in a diffuse halo during our galaxy, but this structure had very sharp edges.
Supermassive black holes feeding on gas and dust contained in the centers of other galaxies have been known to belch out subject material into hourglass figures. In the tip, Slatyer and her colleagues realized that this may possibly be something similar. These Fermi bubbles, as they came to be known, have been the topic of quite some follow-up studies, leading to an extended-running debate over the mechanisms driving the bubbles’ creation (SN: eleven/9/10; SN: 4/20/23).
Slatyer hadn’t found dark matter, but, she says, “I try now now not to complain when nature gives me exciting new things, whether or now now not they were what I turn into searching out contained in the first place.”
Dark matter contained in the early universe
A fine deal of her work since then has drawn to a choice of dark matter scenarios. As an instance, quite some her research has checked out how the mysterious substance may maybe have annihilated or decayed contained in the early universe, leaving in the back of fundamental particles that could cause small variations contained in the expected temperature of the general cosmos. Such an effect would possibly show up contained in the cosmic microwave background, or CMB, a remnant light left over from when the universe turn into just 380,000 years old.
Satellites measuring this light have found that it indicates the cosmos had almost the exact same temperature no matter which direction they look, with deviations of best one part in 100,000. Slatyer and her colleagues calculated that, if dark matter annihilation took place, it would have generated an exceptionally good subtler temperature signature, the total way down to 1 part in 1,000,000. Her team reported in 2023 how the presence of self-annihilating dark matter would distort the CMB — a signal for future instruments to are hunting for for for.
In a learn about published in May 2024, she and colleagues checked out other potential effects of excessive heat contained in the early universe from dark matter. Below some scenarios, this higher temperature would possibly have generated surplus free electrons. Those free electrons may maybe have acted as catalysts for chemical reactions that may have favored the formation of stars, possibly leading to the creation of enormous numbers of stars very early on.
Other teams have suggested that excess heat would have pushed gas and dust around more readily, a motion that may have reduced star formation. If that's the case, larger clumps of subject material would possibly have as an alternative collapsed into massive black holes, that may have turn into seeds around which the first galaxies coalesced.
Such ideas may maybe help explain what the James Webb Space Telescope has been seeing as it peers into cosmic history. The telescope appears to have found large black holes and galaxies early contained in the universe (SN: three/4/24). Slatyer and her colleagues are suggesting that dark matter may well be the culprit in the back of these strangely massive cosmic objects.
By taking her theories to their logical conclusions, Slatyer has made herself invaluable to the community of theoretical and observational physicists hunting for dark matter. “She’s one in every of those those that’s kind of ubiquitous,” Finkbeiner says. “She shows up at every meeting. She has her finger in every pie. She’s on every panel to figure out what the field should do for the next 10 years.”
Given how little researchers learn about dark matter, Slatyer thinks it’s important to visualize a vast collection of potential possibilities after which come up with experiments to test those options. “We try to … make certain that that we don’t miss anything else blindingly obvious,” she says.
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