Astronomers have learned lots about the universe − but how do they study astronomical objects too distant to visit?
NASA’s OSIRIS-REx spacecraft flew by Earth on Sept. 24, 2023, dropping off its sample of dust and pebbles gathered from the surface of near-Earth asteroid Bennu.
Analysis of this sample will help scientists understand how the solar system formed and from what sorts of materials. Scientists will begin their analysis in the same facility that analyzed rocks and dust from the Apollo lunar landings.
As an astronomer studying how planets form around distant stars, I felt excited watching the broadcast of that Bennu sample descending to the Utah desert – and a little envious. Those of us who study distant young solar systems can’t send robotic spacecraft to get a closer look at them, let alone grab a sample for laboratory analysis. Instead, we rely on remote observations.
But what astronomers can measure using telescopes is not what we really want to know – instead, we calculate the properties we’re interested in studying by observing and interpreting apparent properties from afar.
Asteroids are like fossils – they’re composed of rocky material from the formation and early evolution of a solar system and they are preserved nearly unchanged. That’s how the pristine Bennu samples will help astronomers learn about our solar system’s formation.
Over the past several decades, astronomers have learned that disks of gas and dust called protoplanetary disks orbit young stars. Observing these disks – located many light years outside our solar system – can help astronomers understand the early planet formation process, but they’re too distant to send a sample-return mission like OSIRIS-REx to directly measure what the dust and asteroids in these systems are made of.
All that astronomers like me can do is observe those distant regions of the universe remotely, using telescopes here on Earth or in orbit near Earth. But even with limited tools and techniques, we’ve still managed to learn quite a bit about them.