The Black Hole Explorer: motivation and vision

Johnson, Michael; Akiyama, Kazunori; Baturin, Rebecca; Bilyeu, Bryan; Blackburn, Lindy; Boroson, Don; Cárdenas-Avendaño, Alejandro; Chael, Andrew; Chan, Chi-kwan; Chang, Dominic; Cheimets, Peter; Chou, Cathy; Doeleman, Sheperd S.; Farah, Joseph; Galison, Peter; Gamble, Ronald S.; Gammie, Charles F.; Gelles, Zachary; Gómez, José L.; Gralla, Samuel E.; Grimes, Paul K.; Gurvits, Leonid I.; Hadar, Shahar; Haworth, Kari; Hada, Kazuhiro; Hecht, Michael H.; Honma, Mareki; Houston, Janice; Hudson, Ben; Issaoun, Sara; Jia, He; Jorstad, Svetlana; Kauffman, Jens; Kovalev, Yuri; Kurczynski, Peter; Lafon, Robert; Lupsasca, Alexandru; Lehmensiek, Robert; Ma, Chung-Pei; Marrone, Daniel P.; Marscher, Alan P.; Melnick, Gary; Narayan, Ramesh; Niinuma, Kotaro; Noble, Scott C.; Palmer, Eric J.; Palumbo, Daniel C. M.; Paritsky, Lenny; Peretz, Eliad; Pesce, Dominic; Plavin, Alexander; Quataert, Eliot; Rana, Hannah; Ricarte, Angelo; Roelofs, Freek; Shtyrkova, Katia; Sinclair, Laura C.; Small, Jeffrey; Sridharan, Tirupati Kumara; Srinivasan, Ranjani; Strominger, Andrew; Tiede, Paul; Tong, Edward; Wang, Jade; Weintroub, Jonathan; Wielgus, Maciek; Wong, George N.

doi:10.1117/12.3019835

Cited by 6 publications

References 153 publications

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Imaging fermionic dark matter cores at the centre of galaxies

Pelle,

Argüelles,

Vieyro

et al. 2024

Monthly Notices of the Royal Astronomical Society

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Current images of the supermassive black hole (SMBH) candidates at the center of our Galaxy and M87 have opened an unprecedented era for studying strong gravity and the nature of relativistic sources. Very-long-baseline interferometry (VLBI) data show images consistent with a central SMBH within General Relativity (GR). However, it is essential to consider whether other well-motivated dark compact objects within GR could produce similar images. Recent studies have shown that dark matter (DM) halos modeled as self-gravitating systems of neutral fermions can harbor very dense fermionic cores at their centers, which can mimic the spacetime features of a black hole (BH). Such dense, horizonless DM cores can satisfy the observational constraints: they can be supermassive and compact and lack a hard surface. We investigate whether such cores can produce similar observational signatures to those of BHs when illuminated by an accretion disk. We compute images and spectra of the fermion cores with a general-relativistic ray tracing technique, assuming the radiation originates from standard α disks, which are self-consistently solved within the current DM framework. Our simulated images possess a central brightness depression surrounded by a ring-like feature, resembling what is expected in the BH scenario. For Milky Way-like halos, the central brightness depressions have diameters down to ∼35 μas as measured from a distance of approximately 8 kpc. Finally, we show that the DM cores do not possess photon rings, a key difference from the BH paradigm, which could help discriminate between the models.

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Imaging fermionic dark matter cores at the centre of galaxies

Pelle,

Argüelles,

Vieyro

et al. 2024

Monthly Notices of the Royal Astronomical Society

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The Black Hole Explorer cryocooling instrument

Rana,

Akiyama,

Canavan

et al. 2024

Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave

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The Black Hole Explorer is a space-based very-long baseline interferometry (VLBI) mission that will seek to perform precision black hole measurements, detect the photon ring around a black hole, explore the spacetime, spin, and mass properties of black holes, and attempt to experimentally validate predictions of General Relativity. These ambitious goals are achieved through the use of cryogenic receivers offering quantum-limited sensitivities across a wide frequency coverage. The dual-band receivers at 80-106 GHz and 240-320 GHz require 20 K and 4.5 K operating temperatures, respectively. To reach this, the planned cryocooling system will include two cold stages; a 20 K stage which must lift a heat load of approximately 125 mW and a 4.5 K stage lifting 10 mW of heat load. A survey of 4 K cryocooler development for spaceflight is explored in order to baseline the cryocooling system design for BHEX and leverage existing technology in the space industry at high TRLs. Notable space missions of relevance include Planck, JEM/SMILES, Hitomi, XRISM, and the advancement of US cryocoolers in this temperature range thanks to the ACTDP/JWST. Integration of the cryocooler with the receivers and broader instrument requires careful consideration, as it influences the instrument operation and thermal challenges. The latter includes thermally linking the cold ends of each cooling stage whilst minimising heat losses and ensuring adequate passive cooling for the cryocooler warm end heat rejection. Moreover, the challenges and trade-offs in sizing the mass and reducing the power consumption are explored: varying modes of operation in conjunction with other key instrument subsystems, the receiver cold temperature requirements, which in turn influence the scientific objectives of the mission, and mitigating the mission critical risks of the system. Overall, this paper presents an overview of cooling needs, initial design considerations, a survey of 4 K spaceflight cryocooler developments and current progress, and balancing scientific requirements of the instrument with the limitations of technical cryocooling capabilities, within the framework of a small-class (SMEX) space mission aiming to achieve breakthrough goals in experimental black hole physics.

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The Black Hole Explorer: instrument system overview

Marrone,

Houston,

Akiyama

et al. 2024

Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave

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The Black Hole Explorer (BHEX) is a space very-long-baseline interferometry (VLBI) mission concept that is currently under development. BHEX will study supermassive black holes at unprecedented resolution, isolating the signature of the "photon ring" -light that has orbited the black hole before escaping -to probe physics at the edge of the observable universe. It will also measure black hole spins, study the energy extraction and acceleration mechanisms for black hole jets, and characterize the black hole mass distribution. BHEX achieves high angular resolution by joining with ground-based millimeter-wavelength VLBI arrays, extending the size, and therefore improving the angular resolution of the earthbound telescopes. Here we discuss the science instrument concept for BHEX. The science instrument for BHEX is a dual-band, coherent receiver system for 80-320 GHz, coupled to a 3.5-meter antenna. BHEX receiver front end will observe simultaneously with dual polarizations in two bands, one sampling 80-106 GHz and one sampling 240-320 GHz. An ultra-stable quartz oscillator provides the master frequency reference and ensures coherence for tens of seconds. To achieve the required sensitivity, the front end will instantaneously receive 32 GHz of frequency bandwidth, which will be digitized to 64 Gbits/sec of incompressible raw data. These data will be buffered and transmitted to the ground via laser data link, for correlation with data recorded simultaneously at radio telescopes on the ground. We describe the challenges associated with the instrument concept and the solutions that have been incorporated into the baseline design.

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The Black Hole Explorer: motivation and vision

Cited by 6 publications

References 153 publications

Imaging fermionic dark matter cores at the centre of galaxies

Imaging fermionic dark matter cores at the centre of galaxies

The Black Hole Explorer cryocooling instrument

The Black Hole Explorer: instrument system overview

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