Are We Seeing Dark Matter? Pulsars Hint at Invisible Galactic Structures

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By Lydia Amazouz Published on July 20, 2024 18:30
Are We Seeing Dark Matter Pulsars Hint At Invisible Galactic Structures
Are We Seeing Dark Matter? Pulsars Hint at Invisible Galactic Structures - © The Daily Galaxy --Great Discoveries Channel

Researchers have detected massive, mysterious objects floating through deep space that may be passing in front of pulsars and temporarily blocking their light pulses.

These findings suggest the presence of large, invisible structures in the Milky Way, sparking debates about their nature and potential connections to dark matter.

Pulsars as Cosmic Timekeepers

Pulsars, the highly magnetized remains of dead stars that spin like cosmic lighthouses, emit extremely steady flashes of light. These pulsars are some of the best clocks in the universe, surpassed only by the most advanced human-made timekeeping devices. Researchers use these consistent pulses to measure time with atomic-level accuracy and observe gravitational waves. However, there are fleeting moments when these highly regular pulses aren't exactly on time, leading to intriguing discoveries.

Pulsar

Professor John LoSecco from the University of Notre Dame explained, "I have been warned not to call them planets, not to call them dark matter, just call them mass concentrations because, just by looking in the radio, you can’t determine what they are." These masses, which could be brown dwarfs, white dwarfs, or other unknown objects, cause barely perceptible delays in the signals on the microsecond level.

Pulsars serve as cosmic timekeepers due to their precise and regular pulses, which are the remnants of supernova explosions. These neutron stars rotate rapidly, emitting beams of electromagnetic radiation that sweep across space like lighthouse beams. When these beams intersect with Earth, they are detected as pulses of radio waves. The predictability and regularity of these pulses make pulsars ideal for probing the gravitational environment of the Milky Way.

Detecting Invisible Masses

LoSecco and his colleagues have been creating a catalog of these mysterious masses using arrival time data from seven radio telescopes spread across the globe. By analyzing the deviations in the arrival time caused by the change in distance between the mass and the line of sight to the pulsar, they identified 12 candidates from eight independent pulsars.

LoSecco stated, "The research might even shed light on dark matter, the hypothetical stuff that scientists believe makes up 85 percent of the total matter in the universe, but has yet to be observed directly. We take advantage of the fact that the Earth is moving, the Sun is moving, the pulsar is moving, and even the dark matter is moving." This intricate dance of movements allows for the detection of these masses, which subtly alter the arrival times of the pulses.

The team utilized data from millisecond pulsars, which are particularly valuable due to their rapid rotation rates and stability. These pulsars act as natural laboratories for testing the effects of gravitational fields on time. By carefully monitoring the timing of pulses, researchers can detect minute changes caused by massive objects passing between the pulsar and Earth.

The Role of General Relativity

The idea behind the research is rooted in general relativity, which posits that being inside a gravitational field affects the passing of time. If a massive object passes in front of a pulsar, the pulse's arrival time is delayed. An object the mass of the Sun would create a delay of 10 microseconds. Although this is minuscule in human terms, it is significant for the precision of the Pulsar Timing Array.

LoSecco emphasized the importance of removing all motion to achieve accurate time measurements: "The pulsar doesn't exist in isolation. These pulses come from these millisecond pulsars, many of which are found in binaries. So they're moving around, they're in orbit around another object. And so you have to remove all that motion. The Earth is moving around the Sun. You have to remove that motion. You have to move all this motion so you can get the actual time of arrival."

This concept is crucial for understanding how gravity influences time, as predicted by Einstein's theory of general relativity. When a massive object, such as a brown dwarf or a clump of dark matter, passes in front of a pulsar, it creates a gravitational lensing effect that bends the path of the light. This bending causes the light to take a slightly longer path, resulting in a delay in the arrival time of the pulses.

What Are These Mass Concentrations?

The nature of these mass concentrations remains a mystery. They could be massive rogue planets, stellar remnants like brown dwarfs or white dwarfs, or even clumps of dark matter. LoSecco is cautious about drawing conclusions: "I can't even guarantee that they're dark. They could be a brown dwarf or some sort of a white dwarf or something else."

The research is ongoing, and LoSecco is open to input from the scientific community: "I am looking for people to criticize because it gives me ideas for what to go back and look at and to be skeptical about the result."

The identification of these masses opens up exciting possibilities for understanding the hidden structures within our galaxy. If some of these objects are indeed composed of dark matter, it could provide valuable insights into one of the most elusive and mysterious components of the universe. Alternatively, if they are rogue planets or stellar remnants, it would still expand our knowledge of the diversity and distribution of objects in the Milky Way.

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