[Paper Review] Opportunities for Astrophysical Science from the Inner and Outer Solar System

M. Zemcov, I. Arcavi+23 more|arXiv (Cornell University)|Mar 13, 2019

Gamma-ray bursts and supernovae62 references4 citations

TL;DR

This white paper advocates for astrophysical science missions beyond Earth's orbit, proposing that the inner and outer solar system offer unique vantage points to study the extragalactic background light, interplanetary dust morphology, and gravitational microlensing. By leveraging distant solar system missions with astrophysically optimized instruments, researchers can achieve unprecedented sensitivity, temporal stability, and three-dimensional tomographic mapping of the dust cloud, enabling transformative insights into cosmic structure, planet formation, and fundamental physics.

ABSTRACT

Astrophysical measurements away from the 1 AU orbit of Earth can enable several astrophysical science cases that are challenging or impossible to perform from Earthbound platforms, including: building a detailed understanding of the extragalactic background light throughout the electromagnetic spectrum; measurements of the properties of dust and ice in the inner and outer solar system; determinations of the mass of planets and stellar remnants far from luminous stars using gravitational microlensing; and stable time-domain astronomy. Though potentially transformative for astrophysics, opportunities to fly instrumentation capable of these measurements are rare, and a mission to the distant solar system that includes instrumentation expressly designed to perform astrophysical science, or even one primarily for a different purpose but capable of precise astronomical investigation, has not yet been flown. In this White Paper, we describe the science motivations for this kind of measurement, and advocate for future flight opportunities that permit intersectional collaboration and cooperation to make these science investigations a reality.

Motivation & Objective

• Address the lack of astrophysical measurements from beyond 1 AU, where Earth-based observations are limited by circumsolar dust foregrounds.
• Overcome the current scarcity of deep-space astrophysical data—only 3.5 such results per decade since Pioneer 10—by advocating for dedicated instrumentation.
• Enable high-sensitivity, stable time-domain astronomy by placing instruments in the quiet, low-background environment of the outer solar system.
• Develop three-dimensional tomographic maps of the interplanetary dust cloud using multi-point observations from different solar orbits.
• Validate exoplanet observation models by simulating Earth as an exoplanet from large solar system distances, providing ground-truth data for habitable world characterization.

Proposed method

• Utilize multi-observer vantage points across the inner and outer solar system to collect interplanetary dust (IPD) brightness measurements at multiple wavelengths and lines of sight.
• Apply tomographic inversion techniques to combine multi-directional IPD observations into a 3D reconstruction of the dust cloud’s spatial distribution and optical properties.
• Leverage gravitational microlensing events detected from distant solar system locations to measure planetary and stellar remnant masses independently of luminosity.
• Integrate astrophysical instrumentation into existing or planned deep-space missions (e.g., New Horizons, Interstellar Probe) to enable time-domain and photometric surveys.
• Use spectroscopic observations from 40 AU or beyond to simulate Earth-like exoplanet observations, including Earthshine and direct imaging, for model validation.
• Combine data from Earth-based, near-Earth, and deep-space platforms to disentangle foreground dust contributions and improve modeling of the extragalactic background light (EBL).

Experimental results

Research questions

• RQ1 How can multi-point, multi-wavelength observations from different solar system locations enable a 3D tomographic reconstruction of the interplanetary dust cloud?
• RQ2 What constraints can distant solar system observations place on the composition, structure, and dynamics of dust originating from the Edgeworth-Kuiper Belt and Oort Cloud?
• RQ3 How can astrophysical measurements from beyond 1 AU improve our understanding of the extragalactic background light (EBL) and its implications for galaxy evolution and cosmology?
• RQ4 In what ways can gravitational microlensing events observed from deep space enable mass measurements of dark or low-luminosity objects like exoplanets and stellar remnants?
• RQ5 How can observations of Earth from 40 AU serve as a ground-truth benchmark for validating models of Earth-like exoplanet detection and characterization?

Key findings

• Observations from beyond 1 AU can reduce the bright foreground of circumsolar dust, significantly improving sensitivity and temporal stability for astrophysical measurements.
• Multi-point observations from different solar orbits enable tomographic mapping of the interplanetary dust cloud, revealing its 3D structure and dynamics.
• Gravitational microlensing events observed from distant vantage points allow for mass measurements of planets and stellar remnants independent of their luminosity.
• Distant observations of Earth from 40 AU provide the only known ground-truthed, close-to-interstellar analog to exoplanet observations, enabling validation of retrieval models.
• The current rate of deep-space astrophysical science is extremely low—only 3.5 results per decade since Pioneer 10—highlighting a major unmet opportunity.
• Instrumentation on deep-space missions like New Horizons can be repurposed for astrophysical science, offering a cost-effective path to transformative discoveries.