New Horizons sees stellar parallax
New Horizons is now far enough away from Earth that its perspective of the universe shifts at least two nearby stars into slightly different positions than seen on Earth.
On April 22-23, the spacecraft turned its long-range telescopic camera to a pair of the closest stars, Proxima Centauri and Wolf 359, showing just how they appear in different places than we see from Earth. Scientists have long used this “parallax effect” – how a star appears to shift against its background when seen from different locations — to measure distances to stars.
An easy way to see parallax is to place one finger at arm’s length and watch it jump back and forth when you view it successively with each eye. Similarly, as Earth makes it way around the Sun, the stars shift their positions. But because even the nearest stars are hundreds of thousands of times farther away than the diameter of Earth’s orbit, the parallax shifts are tiny, and can only be measured with precise instrumentation. “No human eye can detect these shifts,” Stern said.
But when New Horizons images are paired with pictures of the same stars taken on the same dates by telescopes on Earth, the parallax shift is instantly visible. The combination yields a 3D view of the stars “floating” in front of their background star fields.
The resulting 3D image, available at the link, is very cool. Both stars clearly appear closer than the surrounding background stars, which of course is true as they are among the closest stars to the Sun.
New Horizons is now far enough away from Earth that its perspective of the universe shifts at least two nearby stars into slightly different positions than seen on Earth.
On April 22-23, the spacecraft turned its long-range telescopic camera to a pair of the closest stars, Proxima Centauri and Wolf 359, showing just how they appear in different places than we see from Earth. Scientists have long used this “parallax effect” – how a star appears to shift against its background when seen from different locations — to measure distances to stars.
An easy way to see parallax is to place one finger at arm’s length and watch it jump back and forth when you view it successively with each eye. Similarly, as Earth makes it way around the Sun, the stars shift their positions. But because even the nearest stars are hundreds of thousands of times farther away than the diameter of Earth’s orbit, the parallax shifts are tiny, and can only be measured with precise instrumentation. “No human eye can detect these shifts,” Stern said.
But when New Horizons images are paired with pictures of the same stars taken on the same dates by telescopes on Earth, the parallax shift is instantly visible. The combination yields a 3D view of the stars “floating” in front of their background star fields.
The resulting 3D image, available at the link, is very cool. Both stars clearly appear closer than the surrounding background stars, which of course is true as they are among the closest stars to the Sun.