Dark matter cannot be directly observed by using normal telescopes or other
imaging methods since it does not emit, absorb, or reflect light. Thus,
astronomers have been looking for alternate ways to find dark matter for
decades.
A recent investigation by scientists from Tsinghua University, Purple
Mountain Observatory, and Peking University looked at the potential for
directly detecting dark photons—prominent dark matter candidates—using radio
telescopes. Their study, which was published in Physical Review Letters, may
help future efforts to find dark photons, which are fictitious particles
that transmit an electric and magnetic field in dark matter, much like
photons do in ordinary matter.
According to Haipeng An, one of the study's authors, "our prior work
examined the conversion of dark photons into photons in the solar
corona."
"In this process, free electrons are excited by dark photon fields, which
causes the emission of regular photons. Based on this study, Jia and I
discussed the possibility of creating electromagnetic signals with free
electrons in a dish telescope and then searching for such signals with the
FAST telescope.
An and his colleagues soon realized that, given the non-relativistic nature
of dark matter, the reflector in such telescopes would need to be spherical
and the receiver of the signal should be positioned at the center of this
sphere. Shortly after they began investigating the use of dish telescopes to
look for electromagnetic signals related to dark photons, An and his
colleagues.
The receiver is positioned near the point of focus of existing dished radio
telescopes, such as the five-hundred-meter aperture spherical radio
telescope (FAST) in China, which are made to observe distant radio
waves.
This meant that dark photon-induced electromagnetic signals would not
concentrate at their receiver.
We momentarily abandoned this notion after this understanding, An said. I
was asked to present lectures on dark matter at the UFITS summer school for
cosmology conducted at the FAST site in the summer of 2021. During this
time, I also carefully examined the FAST telescope's operation. I discovered
that the telescope could view radio waves coming from various directions by
moving the receiver that was suspended above the dish. Then, I had the
thought that, despite the fact that the dark photon dark matter-induced
electromagnetic waves are not focused on the receiver, the electromagnetic
field can nonetheless create a distribution on top of the dish that can be
precisely computed theoretically.
The moveable receiver in radio telescopes should be able to gather
electromagnetic signals in various locations, according to An's subsequent
theoretical predictions. The sensitivity of the telescopes to dark
photon-induced signals might then be increased by comparing the
distributions of the signals gathered by the receiver to those anticipated
by theory.
Then, An said, "We began to calculate this signal with our colleagues." To
our surprise, we discovered that the FAST telescope's sensitivity has
already surpassed the CMB constraint, even without taking into account the
distribution or the extraordinary sensitivity, or the fact that the dark
photon dark matter induced signal is not focused at the receiver. This means
that the FAST telescope can find the dark matter if it is made up of dark
photons and is in the appropriate mass range.
An and his colleagues also examined observation data gathered by the FAST
radio telescope, which is situated in a hamlet in the mountains in the
Guizhou area of China, in order to further evaluate the efficacy of their
suggested approach to look for dark photons. Prof. Xiaoyuan Huang, who is
also a co-author of the latest article, gave this information.
An said, "We examined the data and set the tightest restriction on the
model in the frequency band of 1-1.5 GHz. We calculated the potential
sensitivity of the LOFAR telescope and the future SKA telescope and found
they both have the potential to discover dark photon dark matter. "We
realized that dark photon dark matter could induce electric signals on
dipole antennas and that due to the non-relativistic nature, we could use
interferometry technology to improve the sensitivity.
Overall, the assessments performed by this research team point to the
possibility of using radio telescopes to directly detect dark photons. Thus,
this research may open up new avenues for the ongoing hunt for dark photons,
especially ultra-light dark photons.
An said that Penzias and Wilson came into an unanticipated low-level
background noise in the early 1960s while working on radio astronomy
research. "This cacophony was eventually determined to represent the cosmic
microwave background radiation, giving crucial proof of the very hot early
universe's expansion. Through kinetic mixing with photons, ultra-light dark
photons display electromagnetic interactions similar to photons. Ultra-light
dark photons may behave like cosmic microwave background radiation as a
possibility for diffuse dark matter in the cosmos. Modern radio telescopes
may be used to carefully listen for the elusive murmurs coming from the dark
realm.
This study team demonstrated that ultralight dark photons might possibly be
discovered using radio telescopes, which are frequently used to monitor the
cosmic microwave background. Ultralight dark photons can behave similarly to
dark electromagnetic fields with certain frequencies. Future studies for
dark photon dark matter that rely on extensive radio telescope data may be
guided by their theoretical concerns.
"Our work may open a new sub-area in radio astronomy," An further stated.
The data from the LOFAR and MeerKAT telescopes will now be used to look for
dark photon dark matter signatures. Additionally, we want to use this
concept to look for axion dark matter, another viable possibility for
ultralight dark matter.
