25 research outputs found
Large Bodies in the Kuiper Belt
We present a survey for bright Kuiper Belt Objects (KBOs) and Centaurs,
conducted at the Kitt Peak National Observatory (KPNO) 0.9 m telescope with the
KPNO 8k Mosaic CCD. The survey imaged 164 sq deg near opposition to a limiting
red magnitude of 21.1. Three bright KBOs and one Centaur were found, the
brightest KBO having red magnitude 19.7, about 700 km in diameter assuming a
dark Centaur-like 4% albedo. We estimate the power-law differential size
distribution of the Classical KBOs to have index q = 4.2 (+0.4)(-0.3), with the
total number of Classical KBOs with diameters larger than 100 km equal to 4.7
(+1.6)(-1.0) x 10^4. Additionally, we find that if there is a maximum object
size in the Kuiper Belt, it must be larger than 1000 km in diameter. By
extending our model to larger size bodies, we estimate that 30 (+16)(-12)
Charon-sized and 3.2 (+2.8)(-1.7) Pluto-sized Classical KBOs remain
undiscovered.Comment: 33 pages, 7 figures, to appear in Nov 2001 Astronomical Journa
Material Around the Centaur (2060) Chiron from the 2018 November 28 UT Stellar Occultation
A stellar occultation of Gaia DR3 2646598228351156352 by the Centaur (2060)
Chiron was observed from the South African Astronomical Observatory on 2018
November 28 UT. Here we present a positive detection of material surrounding
Chiron from the 74-in telescope for this event. Additionally, a global
atmosphere is ruled out at the tens of mircobar level for several possible
atmospheric compositions. There are multiple 3-sigma drops in the 74-in light
curve: three during immersion and two during emersion. Occulting material is
located between 242-270 km from the center of the nucleus in the sky plane.
Assuming the ring-plane orientation proposed for Chiron from the 2011
occultation, the flux drops are located at 352, 344, and 316 km (immersion),
and 357, and 364 km (emersion) from the center, with normal optical depths of
0.26, 0.36, and 0.22 (immersion) and 0.26 and 0.18 (emersion), and equivalent
widths between 0.7-1.3 km. This detection is similar to the previously proposed
two-ring system and is located within the error bars of that ring-pole plane;
however, the normal optical depths are less than half of the previous values,
and three features are detected on immersion. These results suggest that the
properties of the surrounding material have evolved between the 2011, 2018, and
2022 observations.Comment: Accepted by the Planetary Science Journal 21 Oct. 2023; 13 pages, 9
figures, 4 table
Haze in Pluto's atmosphere: Results from SOFIA and ground-based observations of the 2015 June 29 Pluto occultation
On UT 29 June 2015, the occultation by Pluto of a bright star (r′ = 11.9) was observed from the Stratospheric Observatory for Infrared Astronomy (SOFIA) and several ground-based stations in New Zealand and Australia. Pre-event astrometry allowed for an in-flight update to the SOFIA team with the result that SOFIA was deep within the central flash zone (~22 km from center). Analysis of the combined data leads to the result that Pluto's middle atmosphere is essentially unchanged from 2011 and 2013 (Person et al. 2013; Bosh et al. 2015); there has been no significant expansion or contraction of the atmosphere. Additionally, our multi-wavelength observations allow us to conclude that a haze component in the atmosphere is required to reproduce the light curves obtained. This haze scenario has implications for understanding the photochemistry of Pluto's atmosphere
Communicative and psycholinguistic abilities in children with phenylketonuria and congenital hypothyroidism
Uranus after Solstice: Results from the 1998 November 6 Occultation
this paper are given relative to the rotational North pole of Uranus, following the notation in Baron et al. 1989 and Sicardy et al. 1985.) All published occultations of the Uranian atmosphere at 1-- 100 bar occurred before Uranus' southern summer solstice in 1985, except the Voyager UVS occultation in 1986 (Broadfoot et al. 1986, Herbert et al. 1987). Since Uranus' subsolar latitude changed from 51 # in 1977 to 76 # in 1983, one major goal of 236 0019-1035/01 $35.00 Copyright c 2001 by Academic Press All rights of reproduction in any form reserve