Proxima Centauri, the nearest star to Earth

[ilan]

Wowzer! Pluto spacecraft sees parallax for Proxima
EarthSky in SPACE | June 15, 2020

New images from the fringes of our solar system. The fast-moving New Horizons spacecraft sees a parallax shift – a different apparent position against the background stars – for Proxima Centauri.​

The New Horizons spacecraft, which visited Pluto in 2015, is really out there! This 2-frame animation shows Proxima Centauri, the nearest star to Earth. On the left, Proxima against the star background seen by the spacecraft. On the right, Proxima and its background as we see them from Earth. The difference is due to parallax, the same effect you see if you hold up a finger and close one eye, then the other. It’s a shift in perspective, caused by New Horizons’ great distance from Earth.

For the first time, a spacecraft has sent back pictures of the sky from so far away that some stars appear to be in different positions than we’d see from Earth.

More than four billion miles (6 billion km) from home and speeding toward interstellar space, NASA’s New Horizons has traveled so far that it now has a unique view of the nearest stars. Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI) in Boulder, Colorado, said:

It’s fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth.

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And that has allowed us to do something that had never been accomplished before – to see the nearest stars visibly displaced on the sky from the positions we see them 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.