Opher believes that the influence of the sun’s magnetic field may warp the heliosphere into the shape of a ‘‘croissant.’’ At its plump center, interstellar matter presses in closer than previously thought — which would mean we are less isolated from the rest of the galaxy than we believe.

Last Sept. 29, a Thursday, Larry Zottarelli awoke before 7, as he did most weekdays, and dressed quietly so as not to disturb his sleeping wife. He raked a comb through his silver hair, donned trifocals and a calculator watch and drove to the office. He brewed his first mug of coffee in the efficiency kitchen and carried it to his desk. He’d been on the job for 40 years; the next day would be his last. A printed-out email taped to his computer hutch had instructions for handing in his badge and parking pass and collecting his final paycheck. He had cleared out most of his belongings, except two gallon-size Ziploc bags, in which he had sealed the plastic arms of his office chair to protect them from disintegrating under the daily weight of his elbows. Sitting facing the door, backed by a windowless, conch-pink brick wall, he brought to mind a hermit crab wearing a seashell.

Later that morning, when Zottarelli entered the conference room to attend his last daily flight-team briefing, his colleague Adans Ko, 58, was arranging takeout containers of dim sum on the table for a celebration. He threw an arm around his shoulders and said, ‘‘Larry is going to give me a kiss today!’’ Matsumoto, who was holding a camera, said, ‘‘O.K., look at me.’’ She was making a photo album for him. When the party broke up, I found Zottarelli’s replacement, Lu Yang, at her desk. I asked her if he had given her any specific advice. ‘‘Whatever the problem, you go there and solve it,’’ she said, and laughed.

In retirement, Zottarelli told me, he would like to see Florida again. He wonders how it has changed. In his garage is a 1954 Swallow Doretti, a fixer-upper. ‘‘It probably needs new brakes,’’ he said. I asked him if there was anywhere he liked to drive for fun. ‘‘No,’’ he replied. ‘‘Not anymore.’’