#1998ky26 — Public Fediverse posts

2026-07-25 15:00:00 UTC (Delta: 2026-07-18)

WHERE IS HAYABUSA2♯?
- Barycentric speed: 33.06 km/s (-0.71 km/s)
- Earth flyby: December 2027

🪨 Relative to 1998 KY26
- Distance (km): 343,167,370.08 km (+6,260,364.05 km)
- Distance (AU): 2.29 (+0.04)
- Light travel time: 19 min 4.72 s (+20.88 s)

🌎 Relative to Earth
- Distance (km): 77,913,747.28 km (-5,179,992.74 km)
- Distance (AU): 0.52 (-0.03)
- Light travel time: 4 min 19.90 s (-17.28 s)

#Hayabusa2 #1998KY26

2026-07-25 15:00:00 UTC (Delta: 2026-07-18)

WHERE IS HAYABUSA2♯?
- Barycentric speed: 33.06 km/s (-0.71 km/s)
- Earth flyby: December 2027

🪨 Relative to 1998 KY26
- Distance (km): 343,167,370.08 km (+6,260,364.05 km)
- Distance (AU): 2.29 (+0.04)
- Light travel time: 19 min 4.72 s (+20.88 s)

🌎 Relative to Earth
- Distance (km): 77,913,747.28 km (-5,179,992.74 km)
- Distance (AU): 0.52 (-0.03)
- Light travel time: 4 min 19.90 s (-17.28 s)

#Hayabusa2 #1998KY26

2026-07-18 15:00:00 UTC (Delta: 2026-07-11)

WHERE IS HAYABUSA2♯?
- Barycentric speed: 33.76 km/s (-0.68 km/s)
- Earth flyby: December 2027

🪨 Relative to 1998 KY26
- Distance (km): 336,907,006.03 km (+7,216,921.62 km)
- Distance (AU): 2.25 (+0.05)
- Light travel time: 18 min 43.84 s (+24.07 s)

🌎 Relative to Earth
- Distance (km): 83,093,740.02 km (-5,935,658.66 km)
- Distance (AU): 0.56 (-0.04)
- Light travel time: 4 min 37.18 s (-19.80 s)

#Hayabusa2 #1998KY26

2026-07-18 15:00:00 UTC (Delta: 2026-07-11)

WHERE IS HAYABUSA2♯?
- Barycentric speed: 33.76 km/s (-0.68 km/s)
- Earth flyby: December 2027

🪨 Relative to 1998 KY26
- Distance (km): 336,907,006.03 km (+7,216,921.62 km)
- Distance (AU): 2.25 (+0.05)
- Light travel time: 18 min 43.84 s (+24.07 s)

🌎 Relative to Earth
- Distance (km): 83,093,740.02 km (-5,935,658.66 km)
- Distance (AU): 0.56 (-0.04)
- Light travel time: 4 min 37.18 s (-19.80 s)

#Hayabusa2 #1998KY26

More on #1998KY26 at #ACM2026 :

Toni Santana-Ros details the 2024 lightcurve observations and how earlier fits were aliased to twice the real period - https://www.nature.com/articles/s41467-025-63697-4 .

Calls KY26 "a large boulder".

Subject to the ambiguity of what that means when it came from collisional rubble.

At #ACM2026, Davide Farnocchia presents current knowledge of the trajectory of #1998KY26 : https://iopscience.iop.org/article/10.3847/2041-8213/ae10b8 .

It is a fast-spinning and high albedo asteroid.

And the orbit is explained by radiation pressure, with no need for "dark comet" outgassing.

Good news for Hayabusa 2.

I think it was Peter Jenniskens who pointed out at #ACM2026 how sending a spacecraft to #Kamo'oalewa (and also one to #1998KY26) gives us information on just what objects the size of the Chelyabinsk impactor look like in space.

@setiinstitute

#ESO:
"
Könnte Hayabusa2 auf 1998 KY26 aufsetzen?
"
"Neue Studie zeigt, dass der Zielasteroid der Weltraummission kleiner und schneller ist als gedacht"

https://www.eso.org/public/germany/news/eso2515/

18.9.2025

#Astronomie #Asteroid #1998KY26 #Hayabusa2 #Japan #JAXA #Raumfahrt #Raumsonde #SpaceFlight #VLT

#ESO:
"
Könnte Hayabusa2 auf 1998 KY26 aufsetzen?
"
"Neue Studie zeigt, dass der Zielasteroid der Weltraummission kleiner und schneller ist als gedacht"

https://www.eso.org/public/germany/news/eso2515/

18.9.2025

#Astronomie #Asteroid #1998KY26 #Hayabusa2 #Japan #JAXA #Raumfahrt #Raumsonde #SpaceFlight #VLT

I have a 3D print of the old #TeamRadar #1998KY26 shape model, which was always suspiciously symmetric - because it turned out to be aliased.

Maybe I should order a new one.

QT Agata Rożek @agastro.bsky.social‬
2025 September 18

Check out our tiny rock featured by @esoastronomy !

Now available in Nature Comms: https://www.nature.com/articles/s41467-025-63697-4

We measured the size using the new lightcurve shape models and old radar data #TeamRadar

https://bsky.app/profile/agastro.bsky.social/post/3lz44rubvus26

I have a 3D print of the old #TeamRadar #1998KY26 shape model, which was always suspiciously symmetric - because it turned out to be aliased.

Maybe I should order a new one.

QT Agata Rożek @agastro.bsky.social‬
2025 September 18

Check out our tiny rock featured by @esoastronomy !

Now available in Nature Comms: https://www.nature.com/articles/s41467-025-63697-4

We measured the size using the new lightcurve shape models and old radar data #TeamRadar

https://bsky.app/profile/agastro.bsky.social/post/3lz44rubvus26

the paper

Santana-Ros et al: "#Hayabusa2 extended mission target asteroid #1998KY26 is smaller and rotating faster than
previously known."

https://www.eso.org/public/archives/releases/sciencepapers/eso2515/eso2515a.pdf

the paper

Santana-Ros et al: "#Hayabusa2 extended mission target asteroid #1998KY26 is smaller and rotating faster than
previously known."

https://www.eso.org/public/archives/releases/sciencepapers/eso2515/eso2515a.pdf

RE: https://mastodon.social/@esoastronomy/115224504925649507

TIL a touchdown was in the "menu". Rotating at that speed and still holding up, shouldn't it be rather compact?

#1998KY26

RE: https://mastodon.social/@esoastronomy/115224504925649507

TIL a touchdown was in the "menu". Rotating at that speed and still holding up, shouldn't it be rather compact?

#1998KY26

Additional background information on dark comets:

#TeamRadar observed the dark comet #1998KY26 in 1998: https://echo.jpl.nasa.gov/asteroids/ostro+1999_ky26_science.pdf . It is a lumpy ball ~30 m across.

The #Hayabusa2 spacecraft is now on its way there, with arrival in 2031 July.

Additional background information on dark comets:

#TeamRadar observed the dark comet #1998KY26 in 1998: https://echo.jpl.nasa.gov/asteroids/ostro+1999_ky26_science.pdf . It is a lumpy ball ~30 m across.

The #Hayabusa2 spacecraft is now on its way there, with arrival in 2031 July.

Discussed at #ACM2023 today.

QT Michael Busch 2022 Dec 19 @michael_w_busch

Today on the arXiv:

Seligman et al. 2023, "Dark Comets? Unexpectedly Large Nongravitational Accelerations on a Sample of Small Asteroids" - arxiv.org/pdf/2212.08115…

Suggests outgassing from asteroid #1998KY26, to be visited by Hayabusa 2, at a level #TeamRadar could not detect.

Discussed at #ACM2023 today.

QT Michael Busch 2022 Dec 19 @michael_w_busch

Today on the arXiv:

Seligman et al. 2023, "Dark Comets? Unexpectedly Large Nongravitational Accelerations on a Sample of Small Asteroids" - arxiv.org/pdf/2212.08115…

Suggests outgassing from asteroid #1998KY26, to be visited by Hayabusa 2, at a level #TeamRadar could not detect.

Addendum:

Seligman et al. 2023 discuss at length other things that can push small asteroids around: thermal fracturing throwing dust out, asymmetric meteoroid bombardment, etc.

Resolving this will probably have to wait for @[email protected]/@haya2e_jaxa
to get to #1998KY26.

Addendum:

Seligman et al. 2023 discuss at length other things that can push small asteroids around: thermal fracturing throwing dust out, asymmetric meteoroid bombardment, etc.

Resolving this will probably have to wait for @[email protected]/@haya2e_jaxa
to get to #1998KY26.

Addendum:

Seligman et al. 2023 discuss at length other things that can push small asteroids around: thermal fracturing throwing dust out, asymmetric meteoroid bombardment, etc.

Resolving this will probably have to wait for @[email protected] / @[email protected] to get to #1998KY26.

Addendum:

Seligman et al. 2023 discuss at length other things that can push small asteroids around: thermal fracturing throwing dust out, asymmetric meteoroid bombardment, etc.

Resolving this will probably have to wait for @[email protected] / @[email protected] to get to #1998KY26.

@astrokiwi For the NEAs in this sample; there are options on thermal fracturing, asymmetric meteoroid bombardment, etc. that would push the rock piles around a little bit without outgassing - Seligman et al. rightly discussed the possibilities at length (comparing to Bennu).

Some may not work - e.g. #1998KY26 spins fast, so thermal swings are low.

But that seems qualitatively different than #ʻOumuamua?

@astrokiwi For the NEAs in this sample; there are options on thermal fracturing, asymmetric meteoroid bombardment, etc. that would push the rock piles around a little bit without outgassing - Seligman et al. rightly discussed the possibilities at length (comparing to Bennu).

Some may not work - e.g. #1998KY26 spins fast, so thermal swings are low.

But that seems qualitatively different than #ʻOumuamua?

How could a ~30 m near-Earth asteroid like #1998KY26 hold on to volatiles long enough to still be outgassing?

Hmm...

How could a ~30 m near-Earth asteroid like #1998KY26 hold on to volatiles long enough to still be outgassing?

Hmm...

Today on the arXiv:

Seligman et al. 2023, "Dark Comets? Unexpectedly Large Nongravitational Accelerations on a Sample of Small Asteroids" - https://arxiv.org/pdf/2212.08115.pdf

Suggests outgassing from asteroid #1998KY26, to be visited by Hayabusa 2, at a level #TeamRadar could not detect.

Today on the arXiv:

Seligman et al. 2023, "Dark Comets? Unexpectedly Large Nongravitational Accelerations on a Sample of Small Asteroids" - https://arxiv.org/pdf/2212.08115.pdf

Suggests outgassing from asteroid #1998KY26, to be visited by Hayabusa 2, at a level #TeamRadar could not detect.