Five years after Pluto encounter, New Horizons probe does a far-out parallax experiment
Queen guitarist (and astrophysicist) Brian May, a member of the New Horizons science team, uses his patented OWL viewer to check Proxima Centauri's stereo images, which he combines by combining images from terrestrial telescopes and the New Horizons spacecraft created. (Photo courtesy of Brian May via New Horizons / JHUAPL / SwRI / NASA)
NASA's New Horizons probe measured the distance to nearby stars using a technique as old as that of the old sailors, but from one point of view, these sailors could only dream.
The experiment, carried out on April 22 and 23, when the spaceship was 4.3 billion miles from Earth, revealed the most distant parallax observations ever made.
"It's fair to say that New Horizons looks at an alien sky other than what we see from Earth," senior investigator Alan Stern, a planetary scientist at the Southwest Research Institute, said in a press release today. "And that allowed us to do something that had never been achieved before - to see the next stars visible in the sky from where we see them on Earth."
The parallax effect is similar to the method by which seafarers determine their position by triangulation with a sextant. You can determine the distance to an object when you see it from different locations, separated by a known distance or baseline, and note the shift in angular position.
Scientists have long used parallax to determine the distance to other stars by carefully measuring the slightest shift in the star's position from the star's background from various points in Earth's orbit.
For the April experiment, the New Horizons camera took pictures of two of the closest stars outside our solar system, Proxima Centauri and Wolf 359. These images were then compared to views of the same stars from observatories in Australia and Arizona.
This animated image flashes between New Horizons and Earth Views of the star Proxima Centauri. (JHUAPL / SwRI / NASA / Las Cumbres Observatory)
The star parallax effect would be too subtle to be seen by the human eye from different locations in Earth's orbit, where the maximum baseline is 186 million miles. However, the differences were evident in the images taken by New Horizons.
The New Horizons science team member, Tod Lauer, astronomer at the National Science Foundation's National Optical-Infrared Astronomy Research Laboratory, coordinated the parallax demonstration. "The New Horizons experiment offers the largest parallax baseline ever created - over 4 billion miles - and is the first demonstration of an easily observable star parallax," he said.
Brian May, astrophysicist and stereo image specialist in the New Horizons team and lead guitarist of the legendary rock band Queen, created stereo versions of the parallax images.
"These photographs by Proxima Centauri and Wolf 359 - stars known to both amateur astronomers and science fiction fans - use the greatest distance between viewpoints ever achieved in 180 years of stereoscopy," said May.
This animated image flashes between New Horizons and Earth Views of the Wolf 359 star. (JHUAPL / SwRI / NASA / Mt. Lemmon Observatory)
Stern said the experiment provided novel confirmation of the distances from the two stars. "We don't actually get any better information," he said to GeekWire. "We just do it the old-fashioned way."
The parallax experiment also served as a warm-up exercise for the fifth anniversary of the New Horizons flyby of Pluto on July 14. Stern said he expected the celebration to start early so as not to conflict with the build-up for the launch of NASA's Perseverance rover to Mars later next month.
After the Pluto flyby in 2015, New Horizons took close-up pictures of Arrokoth, a snowman-shaped icy object further out on the edge of the solar system. Stern and his colleagues are still searching the data that will be sent back after meeting Arrokoth on New Year's Day 2019 - and are considering further observation goals.
The New Horizons science team will answer questions about mission, imaging and space exploration during an AskScience AMA session on Reddit from 1:00 p.m. ET (10 a.m.) Friday.
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