This NASA file image shows one of the two Voyager spacecraft. (NASA / AFP/Getty Images )
It's rare for scientists to include personal sentiments in peer-reviewed journals. For the most part, scientific studies are dry, clinical affairs.
Yet there are moments when a paper will end on a poignant or sentimental note, and it usually involves the passing of one of the authors. Such was the case in a study appearing online Wednesday in Geophysical Research Letters about Voyager 1 nearing the threshold of interstellar space.
While study authors interpreted data taken from Voyager's sensors to mean that the spacecraft had, on Aug. 25, 2012, "exited the main solar modulation region" and entered "the local interstellar medium," NASA officials responded quickly on Wednesday by saying they don't believe the probe has yet escaped our solar system.
Although there is no doubt that Voyager, launched in 1977, will one day pass into interstellar space, there are many scientists who have spent much of their career waiting for that day. One of them was space physicist Frank McDonald, a co-author of the study. Unfortunately for McDonald, who helped design many instruments flown on NASA spacecraft, he was never able to see that day.
McDonald died on Aug. 31, just days after he and a colleague hypothesized that Voyager had exited the heliosphere -- that region of space dominated by solar winds and long considered to be the edge of the solar system.
In an acknowledgment at the end of the study, co-author Bill Webber, professor emeritus of astronomy at New Mexico State University, noted McDonald's passing.
"This article was conceived by our Voyager colleague, Frank McDonald, who is no longer with us," Webber wrote.
"Frank, we have been working together for over 55 years to reach the goal of actually observing the interstellar spectra of cosmic rays, possibly now achieved almost on the day of your passing. You wanted so badly to be able to finish this article that you had already started. Together we did it. Bon Voyage!"