Physicists Spot Possible Breeding Grounds for Dark Matter

A hypothetical particle that could marque up the universe’s acheronian substance whitethorn beryllium produced by and bent astir neutron stars, immoderate of the densest objects successful the universe, according to a squad of physicists.

The particles are axions, 1 of respective proposed candidates for alleged acheronian matter, the enigmatic worldly that makes up implicit a 4th of the universe’s matter. A squad of researchers from the universities of Amsterdam, Princeton, and Oxford present posit that axions could signifier clouds astir neutron stars, which are the incredibly dense, collapsed remnants of dormant stars. The uncovering offers a caller arena wherever researchers tin absorption astrophysical searches for acheronian matter, portion highlighting the imaginable inferior of a vigor scope successful space.

Possible acheronian substance factories

The squad suggests that immoderate axions produced wrong neutron stars could person into photons and flight into space. But galore of these particles would stay trapped by the star’s gravity, forming an axionic unreality astir the neutron star. The group’s probe describing the thought was precocious published successful Physical Review X and follows up connected an earlier enactment by the squad that explored axions that could flight the gravitational fields of the neutron stars that nutrient them.

“When we spot something, what is happening is that electromagnetic waves (light) bounce disconnected an entity and deed our eyes. The mode we ‘see’ axions is simply a small different,” said Anirudh Prabhu, a probe idiosyncratic astatine the Princeton Center for Theoretical Science and co-author of the paper, successful an email to Gizmodo. “While airy tin ‘bounce’ disconnected of axions, this process is highly rare. The much communal mode to observe axions is done the Primakoff effect, which allows axions to person into airy (and vice versa) successful the beingness of a beardown magnetic field.”

Some neutron stars tin beryllium among the astir magnetic objects successful the universe, and truthful are fixed a peculiar label: magnetars. This highly magnetized situation is fertile breeding grounds for axions’ conversion into light, Prabhu said, which past could beryllium detectable by space-based telescopes.

Dark substance and axion waves successful the universe

Dark substance is the catch-all sanction for the 27% of stuff successful the beingness that scientists cannot straight observe due to the fact that it does not emit airy and lone appears to interact with mean substance done gravitational interactions. Other candidates see Weakly Interacting Massive Particles (or WIMPs), dark photons, and primordial achromatic holes, to sanction a few. Axions were primitively projected arsenic a solution to a occupation successful particle physics: Basically, immoderate of the predicted characteristics of the neutron aren’t observed successful nature. Hence their name—axions—which comes from a cleaning merchandise brand. After all, the axion was projected arsenic a mode to cleanable up immoderate of the nasty conundrums that arose astir the Standard Model of particle physics. Last year, a antithetic squad of researchers studied Einstein rings—areas of abstraction wherever airy has been bent powerfully by gravity, forming a disposable “ring” successful space—and recovered evidence boosting axions arsenic a campaigner for acheronian matter.

The electromagnetic waves (i.e., light) produced by converting axions could person wavelengths a fraction of an inch up to much than fractional a mile (one kilometer) long, Prabhu noted. But Earth’s ionosphere blocks precise agelong wavelengths from Earth-based telescopes, truthful space-based observatories mightiness beryllium our champion stake for spotting grounds of axions.

Neutron stars and axions person a history

“It is good established successful the tract of axion physics that if you person large, time-varying electrical fields parallel to magnetic fields you extremity up with perfect conditions for producing axions,” said Benjamin Safdi, a particle physicist astatine UC Berkeley who was not affiliated with the caller paper, successful an email to Gizmodo. “In retrospect, it is evident and wide that if this process happens successful pulsars a sizable fraction of the axions produced could beryllium gravitationally bound owed to the beardown gravity of the neutron star. The authors merit a batch of recognition for pointing this out.”

In 2021, Safdi co-authored a paper positing that axions whitethorn beryllium produced successful the Magnificent Seven, a radical of neutron stars successful our ain galaxy. The Magnificent Seven nutrient high-frequency X-rays, and the squad projected that axions converting into photons could nutrient X-rays similar those observed by immoderate telescopes. But galore of the axions produced astatine the cores of those neutron stars enactment person to the source, the caller squad said, and physique up a ample colonisation implicit hundreds of millions—if not billions—of years.

“These axions accumulate implicit astrophysical timescales, thereby forming a dense ‘axion cloud’ astir the star,” the squad wrote successful the paper. “While a deeper knowing of the systematic uncertainties successful these systems is required, our existent estimates suggest that existing vigor telescopes could amended sensitivity to the axion-photon coupling by much than an bid of magnitude.”

“There are a batch of uncertainties, however, successful the calculations presented successful this enactment — this is nary responsibility of the authors; it is simply a hard, dynamical problem,” Safdi added. “I would besides similar to spot much thorough enactment connected the detection prospects for this signal, including a amended occupation modeling the neutron prima colonisation and estimating the sensitivity with existing and upcoming instruments.”

So however tin we observe and place acheronian matter?

But the state-of-the-art telescopes successful abstraction are not vigor telescopes. The Webb Space Telescope, launched successful 2021, observes immoderate of the oldest airy we tin spot astatine infrared and near-infrared wavelengths. ESA’s Euclid Space Telescope, launched past twelvemonth with the circumstantial extremity of improving our knowing of the universe’s acheronian matter, besides sees the cosmos successful the infrared. In fact, 1 of the astir compelling options for a radio-based observatory is the Lunar Crater Radio Telescope (LCRT), which is precisely what it sounds like: a immense vigor scope that would marque a crockery retired of a lunar crater connected the acheronian broadside of the Moon.

“Axions are 1 of our champion bets for caller physics,” Safdi said, though they are “notoriously hard to probe fixed their feeble interactions with mean matter.”

“These feeble interactions tin beryllium magnified successful utmost astrophysical environments specified arsenic those recovered successful neutron prima magnetospheres,” helium added. “Work similar this could frankincense easy unfastened the pathway towards discovery.”

There are plentifulness of vigor telescopes doing fantastic work connected Earth—MeerKAT, the Very Large Telescope, and ALMA, to sanction a few—but it seems we whitethorn request a caller space-based ngo if we privation to person a accidental of seeing axionic waves. No pressure, NASA coffers!