“The earlier results suggested a more head-on collision, and the new results suggest a more glancing blow,” wrote Roland van der Marel, of the Space Telescope Science Institute, and lead author of the paper, in an email.

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But the ending will be the same, he said: the merger of both galaxies into a cosmic monstrosity.

So enjoy the extra half-billion years here in the tranquil suburbs of the Milky Way.

This reprieve, if it can be called one, is the latest tidbit in a cornucopia of data from Gaia, a European spacecraft tasked with measuring the precise positions, velocities and other attributes of more than a billion stars in the Milky Way and other nearby galaxies.

The data have provided new insight into the history, dynamics and future of the Local Group, the small cluster of galaxies to which the Milky Way belongs. Joining us is the Andromeda galaxy, a slightly larger twin of the Milky Way, about 2.5 million light years distant, and, slightly farther away, a smaller spiral in the Triangulum constellation called M33. Other members of the group include a few dozen dwarf galaxies such as the Large and Small Magellanic clouds — puffs of light visible in the Southern hemisphere.