Sending atomic clocks close to the sun could unlock the secrets of dark matter

An artist's depiction of the Deep Space Atomic Clock spacecraft.
An artist's depiction of the Deep Space Atomic Clock spacecraft. (Image credit: NASA)

Space probes that fly close to the sun might one day help to reveal the nature of dark matter, a new study finds.

Dark matter is the invisible and largely intangible substance that researchers suggest makes up about five-sixths of all matter in the universe. Although dark matter hasn't been observed directly, its existence is hinted at via its gravitational effects on the movements of stars and galaxies. What dark matter might be composed of, however, remains a mystery.

"The discovery of dark matter would be one of the biggest achievements in human history," study lead author Yu-Dai Tsai, a physicist at the University of California, Irvine, told Space.com.

Related: Could the Large Hadron Collider discover dark matter?

In the new study, the research team proposed a new way to discover the nature of dark matter, using the most precise timepieces ever made: atomic clocks. Whereas grandfather clocks keep time by tracking swinging pendulums, atomic clocks monitor the quantum vibrations of atoms. Currently, the best atomic clock is so precise, it will essentially lose just one second every 300 billion years.

Atomic clocks are sent into space regularly. For instance, GPS satellites rely on atomic clocks to broadcast precisely timed messages that each GPS receiver uses to help pinpoint its location.

In the new study, the physicists suggest launching a mission, tentatively dubbed SpaceQ, to an orbit near the sun. Recently, NASA sent the Parker Solar Probe closer to the sun than any other spacecraft had gone before. In 2021, the probe flew across the sun's corona — its ultrahot upper atmosphere — for the first time, and it continues to circle closer and closer to our star.

"There are certainly technical challenges toward realizing a mission like the one we propose, not [the] least of which is how to most effectively shield the sensitive quantum sensors from the extreme environments one finds near the sun," study co-author Joshua Eby, a physicist at the University of Tokyo, told Space.com. "But missions like the Parker Space Probe show that incredible things are possible, and there seem to be no absolute roadblocks. It will take some R&D [research and development], but this work is hopefully just the beginning of the process."

Leading candidates for dark matter include ghostly ultralight particles. For instance, a hypothetical particle known as an axion may have a mass less than a billionth of an electron's. Theoretical physicists originally proposed the existence of axions to help explain why interactions are seen between some particles but not others.

"If this kind of dark matter exists, you can imagine that we are basking in waves of dark matter," Tsai said.

If dark matter is made of ultralight particles, their insubstantial nature would make them extraordinarily difficult to detect, explaining why they have eluded discovery to date. However, because the sun is far heavier than Earth — about 330,000 times the mass of our planet — it possesses a stronger gravitational pull. In principle, this means the sun may collect significantly more dark matter to it than Earth does. This greater density could make it easier for probes near the sun — closer than Mercury's orbit — to detect these ghostly particles.

An artist's depiction of Parker Solar Probe studying the sun. (Image credit: Johns Hopkins University Applied Physics Laboratory)

The Parker Solar Probe "showed that you could send a satellite very close to the sun, sensing new conditions and making discoveries," study co-author Marianna Safronova, a physicist at the University of Delaware, said in a statement. "That is much closer to the sun than what we are proposing here."

In principle, waves of ultralight dark matter particles could trigger variations in fundamental constants of nature, such as the mass of the electron or the strength of the electromagnetic force. This, in turn, would change how atomic clocks tick — an effect that depends on the atoms the clock uses. By comparing how two different atomic clocks keep time near the sun, researchers may find dark matter. Comparable effects also may be seen in future timekeepers that may prove even more precise than atomic clocks, such as so-called nuclear clocks.

"If ultra-light dark matter were detected in a mission like this, it would be a direct probe of both the density of the dark matter near the sun and its couplings to ordinary matter," Eby said.

The scientists noted that the SpaceQ mission would require clocks that are still under development. In addition, even if it detected dark matter signals, researchers would need independent experiments to verify its findings, Tsai noted.

However, "in principle, if we can measure dark matter in different locations, we can map out the density distribution," Tsai said. "And if the signal gets stronger towards the sun, it would be a compelling smoking-gun signature for discovery."

The scientists detailed their findings online Dec. 5 in the journal Nature Astronomy (opens in new tab).

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Charles Q. Choi
Contributing Writer

Charles Q. Choi is a contributing writer for Space.com and Live Science. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica. Visit him at http://www.sciwriter.us

  • bwana4swahili
    Nice to have a research project for life trying to find nonexistent dark matter! How about simply showing the gravitational constant is not really constant!?
    Reply
  • leoheck
    bwana4swahili said:
    Nice to have a research project for life trying to find nonexistent dark matter! How about simply showing the gravitational constant is not really constant!?

    There are people that is going to do that. It is just another path. The most promising paths are going to remain longer.
    Reply
  • orsobubu
    bwana4swahili said:
    Nice to have a research project for life trying to find nonexistent dark matter! How about simply showing the gravitational constant is not really constant!?


    IMO you are right about the dark matter scam, but the answer is that they are simply not able to calculate what the real mass is; there is not a mysterious part of the matter, they leave out some already well known phenomena from the calculation. So, the possibility that the gravitational constant is not a constant is a consequence of the exclusion of some force of field or particle or dimension from the equation.
    Reply
  • DrRaviSharma
    What amazes one is that the researchers chose strong gravitational areas where presence of matter as we know is dense while we know even from Astrophysics that DM is everywhere and not anymore pronounced in dense matter, in fact quite the contrary.
    Thanks.
    Ravi
    (Dr. Ravi Sharma, Ph.D. USA)
    NASA Apollo Achievement Award
    Chair, Ontology Summit 2022
    Particle and Space Physics
    Senior Enterprise Architect
    Reply
  • Ziggosauroos
    Has any one ever observed a lensing gravitional effect caused by a 'dark matter'?
    Reply
  • billslugg
    Yes, many images have been made of gravitational lensing where there is not enough conventional matter to account for it.

    Warped Galaxies Reveal Signs of Universe's Hidden Dark Matter | Space
    Reply
  • DrRaviSharma
    It is more than 10 years old study, is it still valid or are there recent observations, including JWST?
    Reply
  • Ziggosauroos
    billslugg said:
    Yes, many images have been made of gravitational lensing where there is not enough conventional matter to account for it.

    Warped Galaxies Reveal Signs of Universe's Hidden Dark Matter | Space
    I'm thinking about a case with no visible conventional matter source of the gravity at all or a very little.
    Reply
  • billslugg
    Ziggosauroos said:
    I'm thinking about a case with no visible conventional matter source of the gravity at all or a very little.
    No, there will always be some conventional matter in any photo.
    Reply
  • billslugg
    DrRaviSharma said:
    It is more than 10 years old study, is it still valid or are there recent observations, including JWST?
    Here is the first JWST detection of dark matter through gravitational lensing, from Max Planck Institute of JWST images in 2022
    First JWST observations of a gravitational lens - Mass model from new multiple images with near-infrared observations of SMACS J0723.3−7327 (aanda.org)
    Here is another study from Nagoya University of gravitational lensing of dark matter from JWST, also in 2022
    James Webb discovered the ancient dark matter of the Universe (universemagazine.com)Here is one by NASA last year using Hubble images
    Gravitational Lensing (hubblesite.org)Here are six examples in a study published in 2020
    Two Kinds Of Gravitational Lenses Both Reveal Dark Matter (forbes.com)
    Reply