Jupiter as a Dark Matter Detector

Title: Search for dark matter ionization on the night side of Jupiter with Cassini

Authors: Carlos Blanco and Rebecca K. Leane

First Author’s Institution: Princeton University, Department of Physics, Princeton, NJ; Stockholm University and The Oskar Klein Centre for Cosmoparticle Physics, Alba Nova, Stockholm, Sweden

Status: Accepted to PRL [open access]

Although dark matter makes up over 80% of the total matter content of the Universe, we have yet to detect it. Not only is dark matter effectively invisible (it doesn’t reflect, absorb, or emit light), we also don’t really know much  about it — like how massive it is or how likely it is to interact with other particles — which makes searching for it a particularly daunting endeavor. Over the years, researchers have implemented a variety of search strategies, ranging from building enormous liquid xenon detectors that will scintillate if dark matter particles hit them, to smashing particles together in colliders to try to create dark matter. In today’s paper, the authors present a new approach using Jupiter as a dark matter detector.

A sphere serves as a pictorial representation of Jupiter. The side facing the Sun (the day side) is shaded in yellow and the side facing away from the Sun (the night side) is shaded in black. Black arrows pointed towards the day side represent solar extreme ultraviolet (UV) radiation. Blue/green regions at the top and bottom of the sphere represent Jupiter’s magnetic poles. Dashed black arrows pointing into the poles from outside the sphere represent
accelerated electrons. A small rectangular region in the center of the night side is outlined in red and is labeled as the "search region."
Figure 1: A pictorial representation of Jupiter. The side facing the Sun (the day side) is shown in yellow and the side facing away from the Sun (the night side) is shown in black. H3+ is produced on the day side as a result of solar extreme ultraviolet (UV) radiation. The blue/green regions represent Jupiter’s magnetic poles where accelerated electrons (e), or auroras, are a source of H3+. The region outlined in red is a low-latitude region on the night side, where no H3+ is expected to be observed in the absence of dark matter annihilation. Adapted from Figure 1 in the paper.

If dark matter particles captured by Jupiter were to collide and destroy (or “annihilate”) each other, it would produce hydrogen ions (H3+) that emit infrared radiation. Therefore, an observation of this infrared radiation would indicate a detection of dark matter. However, H3+ is also produced by other processes on Jupiter, particularly from auroras at high latitudes near Jupiter’s magnetic poles and from solar extreme ultraviolet radiation incident on the side of Jupiter facing the Sun (the day side). In order to isolate the H3+ originating from dark matter annihilation, the authors focus their search on a low-latitude region on the side of Jupiter facing away from the Sun (the night side) (shown in Figure 1).

H3+ data collected by the Visual and Infrared Mapping Spectrometer (VIMS) aboard the Cassini spacecraft as it flew by Jupiter indicated that no H3+ was detected in this region. However, it’s possible that there was actually a  signal present, but it was too small for the instrument to detect. This allows  the authors to place an upper bound on the local H3+ abundance. Using this limit, they calculate the amount of power that would need to be present in order to produce an equivalent signal and compared this value to predictions of the power generated by annihilating dark matter. Because these predictions depend on dark matter’s mass and its scattering cross-section with nucleons, the authors were able to place constraints on these parameters in a previously unexplored part of the parameter space (shown in Figure 2).

A plot with dark matter mass on the x-axis and dark matter-nucleon cross section on the y-axis. A dark gray shaded region represents the constraints placed by this paper, with an orange band representing the uncertainty. A light gray region and a gray dotted line represent the constraints placed by other experiments. Dashed orange lines represent the sensitivities that applying this paper's search methods to Jupiter-like exoplanets could have.
Figure 2: The dark gray shaded region shows the constraints that this study places on the dark matter-nucleon cross section as a function of dark matter mass. The uncertainty of these constraints is represented by the orange shaded band. The orange dashed lines show the projected sensitivities that could be achieved by applying a similar search method to Jupiter-like exoplanets that are ten times as massive as Jupiter and are located 1 kpc and 100 pc from the Galactic center. The light gray shaded region and the dotted gray line show limits placed by other dark matter detection methods. Figure 2 in the paper.

The authors also investigated the possibility of applying this dark matter search method to exoplanets in the inner Galaxy, where the density of dark matter is expected to be high. In particular, researchers are interested in super-Jupiters, which are exoplanets similar to Jupiter, but more massive, which means they can more readily capture dark matter. Because of their distant locations, it’s not possible to spatially resolve low latitude signals for these exoplanets, meaning that there will be a background of H3+ signal from auroras at their poles. However, the combination of their large mass and position in a high-density dark matter environment enable these exoplanets to overcome this background and place even tighter dark matter constraints than Cassini (orange dashed lines in Figure 2).

Although dark matter hasn’t been detected (yet!), the authors of today’s paper have brought a new approach to the search effort, with promising results.

Astrobite edited by Catherine Slaughter

Featured image credit: NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Joseph DePasquale (STScI)

About Cesiley King

I'm currently a 4th year PhD candidate at Case Western Reserve University. I work on instrumentation for CMB-S4, a next generation ground-based cosmic microwave background (CMB) experiment. I am also working on analyzing data from Spider's (a balloon-borne CMB experiment) second flight.

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