April 24, 2020Thoughts on Interstellar Navigation by Parallax

Tod Lauer, a New Horizons science team member from the National Science Foundation's National Optical-Infrared Astronomy Research Laboratory, and organizer of the New Horizons parallax experiment, jotted down some thoughts as he waited for the Sun to set (and the first stellar observations to begin).

Forever and forever we have taken the stars as fixed markers in the sky – old friends to guide your way on land, at sea, in the air and even in space. We flew to the Moon decades ago and shot the stars all along the way. One needs a sense of direction to embark on the unknown. There was a new world to explore, but one framed by the old stars you learned when you were a kid in Ohio.

It's clear today in Tucson; summer's coming and the sky is too bright. Walking in the desert I can pick out Venus, even with the Sun up. The air is thin and the universe is still out there. In a few hours, though, the Sun will retreat and cede the sky to the stars. The new moon will tag along with the Sun, and it should be spectacularly dark. Orion is still with us for a bit before stars of summer chase it off to the west. There to the east and high in the sky will be Leo, easy to pick out with its bright stars, even if it's not as showy or as arresting as Orion. In the southern part of Leo is a dim red star, Wolf 359, one of our closest stellar neighbors. You need a good-sized amateur telescope to see it by eye, but it's easy with a camera, a laptop and a chart. Never mind – you can see it in your imagination, if not with your instrument.

Tonight, New Horizons, blazing a trail out of the solar system, bound for the galaxy beyond, will also be looking at Wolf 359 – as well as Proxima Centauri, the nearest star to us (and which is below the horizon in the U.S.). Pluto is years behind New Horizons now, and the bizarre form of Arrokoth a fleeting memory from a year ago. Cold space is ahead, the Sun dimming year by year as the distance stretches farther, with stars everywhere in a sky darker than we have ever seen. But they are shifting! The sky is starting to look alien to New Horizons as it leaves the skies of home behind forever. We can see this and measure it. We have traveled so far, that from now on we navigate not by how the stars are the same, but how they are different...

Tod R. Lauer
Tucson, Arizona
April 22, 2020