An accompanying music video portrays the singer as an alien astronaut who accidentally crash-lands on Earth and must eventually choose between staying with his found family or returning to his home planet.

"[1] The following day, Big Hit Music posted a notice confirming BTS would be moving ahead with plans to fulfill their mandatory military service and that Jin would be the first member to enlist following the completion of promotions for his solo release.

[2] Several articles subsequently published by Korean news media reported that the song was gifted to Jin by Coldplay and would be released at the end of the month, despite Big Hit not having provided any details about the single at the time.

[9] The singer had developed a close friendship with the band following their working together on the "My Universe" single, and the song was borne from subsequent discussions between both artists about the former "having to leave for a while" due to his enlistment, and him missing his bandmates and fans during that time.

Titled "Outlander", the images showed Jin "standing amid green shrubbery" surrounded by planet-shaped props while "holding a large Jupiter-like sphere" then "posing against a starry blue background".

[11] The second set of concept photos—titled "Lunar Eclipse"—was posted the next day and featured Jin styled with his hair brushed back, in all black, wearing a leather jacket and "classic white Converse hi-tops", which Uproxx described as "giv[ing] off a simple, modern look to your ordinary greaser."

An official Instagram account created for the character provided updates throughout the promotion period, and shared behind-the-scenes photos and short clips from preparations for the single and music video.

"[18] Previously described as expressing Jin's affection for his fans,[6] the song's lyrics "[pay] tribute to a loved one – or a group of them – by casting its gaze skyward and rocketing into outer space".

Similar to the overarching cosmic metaphor Coldplay has used throughout their career, seen first in "Yellow" and realized in full with Music of the Spheres (2021), Jin invokes "the vastness of the great beyond to encapsulate the galactic scale of his feelings".

"[19] In contrast to Daly, MTV's Lai Frances felt that "Jin's artistic path comes full circle", opining that the song "can be seen as the ultimate passion project".

"[20] Writing for Billboard, Jeff Benjamin felt that Coldplay's "stadium-sized rock sound" was the "perfect bed for Jin's steady, soothing vocals" and noted that the singer, known for bringing "raw emotions to his ballads" such as "Awake" and "Epiphany", was "able to capture the same sentimental approach to a more upbeat, dynamic pop-rock song.

[39] "The Astronaut" earned Jin his first solo entry on the US Billboard Hot 100, debuting at number 51 on the chart issue dated November 12, 2022, with 4.9 million domestic streams and 44,000 downloads sold in its first tracking week.

[44] He slowly drifts into the "dark expanse of space" then travels "through a meteor shower, past moons and planets, satellites and asteroid fields"—at one point a dog resembling Jin's late pet Jjangu is also seen on a meteoroid[45]—at increasing velocities, before coming upon an "otherworldly source of light" which then completely envelops him in a bright purple haze.

[50] The visual opens with the same footage from the teaser then switches to Jin in the present-day, doing a crossword puzzle in his bedroom—the singer portrays an alien astronaut living on Earth after accidentally crash-landing there.

[21] Ultimately deciding to stay "where his loved ones and precious things exist",[50] Jin turns his back on the spaceship, which leaves without him, and eventually hitchhikes a ride on the tray of a truck.

[56] Rolling Stone included the track on its "100 Best songs of 2022" list at number 68, with Kristine Kwak writing that "The lyrics capture how BTS make their fans feel: 'When I'm with you/There's no one else/I get heaven to myself.'

[60] Jin appeared as a special guest during Coldplay's concert at the Estadio River Plate Stadium in Buenos Aires, Argentina, held the same day as the single's release, and performed the song live for the first time together with the band.

[61] The concert was broadcast live to over 3,500 theatres worldwide in more than 70 countries as part of a two-night-only live-event cinema special during the Latin America leg of the band's Music of the Spheres World Tour.

[62][63] Rolling Stone shared exclusive behind-the-scenes photos of Jin rehearsing with the band on October 27, as well as muted video footage of him singing while Chris Martin played along on guitar.

[66] Set against a "starry background and colorful shooting lights",[67] the band was joined onstage by Jacob Collier; vocal ensemble the Jason Max Ferdinand Singers, who held glowing orbs in their hands; and performers wearing "colourful helmets" and alien masks, the latter of whom—actress Natasha Ofili—provided an ASL-interpretation of the song.