Active Asteroid P/2017 S5 (ATLAS)
Abstract
Observations of active asteroid P/2017 S5 when near perihelion reveal the ejection of large (102-104 μm) particles at 0.2-2 m s-1 speeds, with estimated mass-loss rates of a few kg s-1. The protracted nature of the mass loss (continuous over ∼150 days) is compatible with a sublimation origin, meaning that this object is likely an ice-bearing main-belt comet. Equilibrium sublimation of exposed water ice covering as little as 0.1 km2 can match the data. Observations a year after perihelion show the object in an inactive state from which we deduce a nucleus effective radius {450}-60+100 {{m}} (albedo 0.06 ± 0.02 assumed). The gravitational escape speed from a body of this size is just ∼0.3 m s-1, comparable to the inferred ejection speed of the dust. Time-series photometry provides tentative evidence for rapid rotation (lightcurve period 1.4 hr) that may also play a role in the loss of mass and which, if real, is a likely consequence of spin-up by sublimation torques. P/2017 S5 shares both physical and orbital similarities with the split active asteroid pair P/2016 J1-A and J1-B, and all three objects are likely members of the ∼7 Myr old, collisionally produced, Theobalda family.
- Publication:
-
The Astronomical Journal
- Pub Date:
- February 2019
- DOI:
- 10.3847/1538-3881/aaf563
- arXiv:
- arXiv:1812.00060
- Bibcode:
- 2019AJ....157...54J
- Keywords:
-
- comets: general;
- comets: individual: P&2017 S5.;
- minor planets;
- asteroids: general;
- asteroids: individual: 2017 S5.;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 15 pages, 6 figures