As for your question, it looks like Pluto has an atmosphere in the picture because, well, it does. Although it's very thin, Pluto's atmosphere is primarily nitrogen, so if you stood in the surface during daytime the sky would appear a very familiar blue color.

Here's another shot taken by New Horizons where you can see it much more clearly: https://upload.wikimedia.org/wikipedia/commons/0/02/Blue_hazes_over_backlit_Pluto.jpg

[–] wjrii@lemmy.world 14 points 5 hours ago (2 children)

Short answer? Because it does. It doesn't take much to be visible compared to space.

[–] Sibbo@sopuli.xyz 4 points 4 hours ago

Oh wow that's really cool! I didn't know.

It's about one millionth of the pressure of earth's atmosphere at sea level.

[–] ShittyBeatlesFCPres@lemmy.world 5 points 4 hours ago (1 children)

I don’t think any planet^1^ has surprised us more than Pluto.

^1^ I know. If anyone gets pedantic, they’re reclassified as a dwarf clown.

[–] FaceDeer@fedia.io 3 points 4 hours ago (1 children)

Pluto's atmosphere has been studied since the 1980s, using spectroscopy and stellar occultation (watching starlight flicker as Pluto passed in front of it). It wasn't a surprise when New Horizons observed it.

[–] ShittyBeatlesFCPres@lemmy.world 2 points 4 hours ago

I wasn’t thinking about the atmosphere. I meant in general, Pluto surprised more than other first fly-bys. Uranus is obviously extra weird in a lot of ways but who was expecting Pluto to be as interesting?

[–] metaStatic@kbin.earth 7 points 4 hours ago (1 children)

(Old)

Hey, fuck you this only happened ... checks watch ... 9 years ago? God Damn, we are getting old.

[–] very_well_lost@lemmy.world 4 points 2 hours ago* (last edited 2 hours ago)

Hey, if you wanna feel really old, look up how long it's been since Pluto was demoted from being a planet.

spoiler alert: its been 18 freaking years

[–] ThotIWasSomebody@lemmy.world 5 points 4 hours ago (2 children)

That's a friggin planet....

[–] threelonmusketeers@sh.itjust.works 3 points 1 hour ago

Always "Pluto, Pluto, Pluto". Why does no one ever remember Ceres, Eris, Haumea, and Makemake? They're each as much of a planet as Pluto is. Dwarf planets, but planets nonetheless.

[–] Zannsolo@lemmy.world 3 points 2 hours ago* (last edited 2 hours ago)

It's smaller than the moon, and six other moons

[–] doomcanoe@sh.itjust.works 2 points 5 hours ago

The Old Adventures of the New Horizons

[–] cyberpunk007@lemmy.ca 0 points 5 hours ago

Probably reflection of light from the other side if I had to guess.