New Horizons Images Enable First Test of Interstellar Navigation

After departing from our solar system, NASA’s New Horizons spacecraft finds itself considerably distant from Earth, causing the stars of the Milky Way to appear in notably different positions compared to our terrestrial views. Astronomers are harnessing this altered perspective to determine the location of galaxy probes, marking the first instance of intergalactic navigation.

Launched in 2006, New Horizons initially observed Pluto before continuing beyond, traversing the Kuiper Belt—an immensely expansive region of rocky debris and dust billions of miles from the Sun. Currently, the spacecraft is hurtling through space at tens of thousands of kilometers per hour.

When gazing at the night sky from Earth, stars seem widely spread apart, so unless equipped with a strong telescope, their positions appear constant from various locations. In contrast, the New Horizons perspective reveals a significant shift in star positions due to the parallax effect. This phenomenon was demonstrated in 2020 when the probe captured images of two nearby stars, Proxima Centauri and Wolf 359.

Now, Todd Lauer from the U.S. National Institute of Light Change Astronomy in Arizona and his team have utilized this effect to gain a new perspective. They accomplished this by comparing images of Proxima Centauri and Wolf 359 taken by the probe with measurements from the Gaia Space Telescope.

“There’s a three-dimensional map of the galaxies around us, allowing you to see your position,” says Lauer. “Using your own camera on a spacecraft offers incredible accuracy.”

To determine the spacecraft’s location, Lauer and his team analyzed the star positions detected by the New Horizons camera, tracing their lines back to the closest intersection point. They then referenced the precise locations of both stars from the Gaia star map to ascertain this point’s relation to the solar system.

Nearly every spacecraft utilizes NASA’s Deep Space Network (DSN) to determine its position within a margin of tens of meters through a network of radio transmitters on Earth. In contrast, the parallax method provides a less precise estimation, determining New Horizons’ location within a 6,000-kilometer sphere, roughly half the distance from Earth to the Sun.

“We don’t aim to replace the Deep Space Network; this is merely a proof-of-concept demonstration,” Lauer notes. Yet, advancements in cameras and equipment could enhance accuracy by up to 100 times.

Employing this technique for interstellar navigation could yield superior location accuracy compared to the DSN. This not only facilitates the spacecraft’s journey further from Earth but also provides more reliable location tracking, enabling autonomous operations without relying on radio signals from the solar system. Massimiliano Vasile from Strathclyde University in the UK emphasizes this potential.

“When we venture to real stars, we’re talking about light-years,” Vasile explains. “The signal from the Deep Space Network must traverse all the way there, moving at light speed, taking years to reach its destination.”

However, Vasile points out that no agency currently has a mission aimed at deeper exploration of interstellar space, limiting the immediate utility of this technique.