427P/ATLAS
A main-belt comet and second ATLAS discovery.
427P/ATLAS is a periodic comet and an active asteroid discovered by the Asteroid Terrestrial-impact Last Alert System. It is notable as the second comet discovered by that survey, after 478P/ATLAS, and for its membership in the Theobalda collisional family of main-belt asteroids.
Quick Facts
- Discovery Ref
- CBET_4434
- Discoverer
- Aren Heinze
- Discovery Site
- ATLAS–HKO (T05)
- Discovery Date
- 27 September 2017
- Mpc Name
- P/2017 S5, P/2021 L6
- Designations
- ATLAS 2nasa-pds
- Orbit Ref
- jpldata · mpc1
- Epoch
- 23 November 2017 (JD 2458080.5)
- Observation Arc
- 3.89 years
- Earliest Precovery Date
- 11 September 2017
- Obs
- 438
- Perihelion
- 2.178 AU
Facts from the source article.
Lore & Background
427P/ATLAS orbits within the main asteroid belt, ranging from 2.18 AU to 4.16 AU from the Sun. Studies of its orbital trajectory indicate it is highly likely a member of the Theobalda collisional family, a group of asteroids formed from a shattered parent body about 7 million years ago. Two other main-belt comets, 455P/PanSTARRS and 483P/PanSTARRS, also belong to this group.
Like most main-belt comets, its observed activity is driven by the sublimation of water ice on its surface. During its perihelion in 2017, its mass loss rate was estimated to be about 5.0±3.0 kg/s. Photometric observations from the Lisnyky Observatory revealed notable instability of color, likely caused by the injection of fresh material into its coma.
Observations from the Hubble Space Telescope in 2019 determined that its nucleus has an effective radius of 0.450±0.060 km, assuming a geometric albedo of 0.06±0.02.
Reader's Guide
427P/ATLAS holds significance as the second comet discovered by the Asteroid Terrestrial-impact Last Alert System, highlighting the survey's role in identifying active objects in the main belt. Its membership in the Theobalda collisional family, alongside 455P/PanSTARRS and 483P/PanSTARRS, provides context for understanding the origins and evolution of main-belt comets from a common parent body. The comet's activity, driven by water-ice sublimation, and its measured mass loss rate during the 2017 perihelion offer quantitative data on volatile release in the asteroid belt. Color instability observed from Lisnyky Observatory suggests ongoing processes that refresh its coma. Hubble Space Telescope measurements of its nucleus size and albedo contribute to physical characterization of these transitional objects. The comet's orbit, confined between 2.18 and 4.16 AU, places it firmly within the main belt, reinforcing the link between cometary activity and asteroidal populations.
Did You Know?
- Its nucleus has an effective radius of 0.450±0.060 km, based on Hubble Space Telescope observations in 2019.
- Photometric observations from the Lisnyky Observatory showed notable color instability, likely from fresh material entering its coma.
Frequently Asked Questions
What is 427P/ATLAS?
It is a periodic comet that also qualifies as an active asteroid, circling the Sun on a roughly 5.65-year orbit. It belongs to the Theobalda collisional family, a cluster of main-belt asteroids believed to share a common parent body.
Who discovered 427P/ATLAS?
The ATLAS (Asteroid Terrestrial-impact Last Alert System) survey detected it, making it the network's second-ever comet identification after 478P/ATLAS.
How large is 427P/ATLAS's nucleus?
Its effective radius is about 0.45 km (±0.06 km) with a geometric albedo near 0.06, marking it as a small, dark body against the starfield.
What does 427P/ATLAS's orbit look like?
It dips to 2.18 AU (≈326 million km) at perihelion and stretches out to 4.16 AU (≈622 million km) at aphelion, completing one full revolution every 5.65 years.
Why does 427P/ATLAS matter to the comet community?
Its dual identity as both an ATLAS-discovered comet and a Theobalda-family member offers a rare look at how collisional debris can still exhibit volatile-driven activity. During the 2017 perihelion passage it was losing mass at roughly 5 kg/s, confirming ongoing outgassing.
More in Periodic Comets 1-24
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