[Iaude] CBET 4450: 20171029 : MINOR PLANETS 2017 SN_33 AND 2017 U1

quai at eps.harvard.edu quai at eps.harvard.edu
Sat Oct 28 21:08:46 EDT 2017

                                                  Electronic Telegram No. 4450
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau at eps.harvard.edu (alternate cbat at iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network

MINOR PLANETS 2017 SN_33 AND 2017 U1
     Two apparently asteroidal objects were found recently via the 1.8-m
Pan-STARRS1 telescope at Haleakala that both passed within 1 AU of the
earth in the past month but that have very unusual retrograde orbits.

     An object designated 2017 SN_33 was found on Sept. 19.6 UT near
magnitude 19-20, have passed perihelion one week earlier at q = 1.84 AU;
the orbital elements published by G. V. Williams on MPEC 2017-U156 indicate
an orbital period of 3860 yr (i = 152.1 deg).  Several observers attempted
to find cometary appearance but found none, noting only stellar appearance,
including H. Sato (Sept. 21.6; mag 19.6 in 32 stacked 15-s exposures with a
0.51-m f/6.8 astrograph at Siding Spring), K. Sarneczky (Oct. 14.8; twelve
stacked 60-s unfiltered images with the 1.02-m Ritchey-Chretien telescope
at Piszkesteto, Hunbary), and R. Wainscoat and D. Woodworth (Oct. 21.2;
mag 20.9-21.0 on 60-s w-band exposures with the 3.6-m Canada-France-Hawaii
Telescope at Mauna Kea).

     An object inadvertently designated as comet C/2017 U1 on MPEC 2017-U181
(and changed to A/2017 U1) with no claimed cometary appearance by any
observers appears to have hyperbolic orbital elements; it was discovered on
Pan-STARRS1 images taken on Oct. 18.5 UT at mag 19.8.  Curiously, 2017 U1
also has perihelion (T = 2017 Sept. 9.4 TT at q = 0.255 AU) around the same
time as 2017 SN_33, both objects being found nearest the sun in their orbits.
G. V. Williams, Minor Planet Center, finds e = 1.197 and i = 122.6 deg from
85 observations spanning Oct. 14-28 (mean residual 0".5; MPEC 2017-U263) for
2017 U1, and he reports that there were no close approaches to major planets
outside of its closest approach to the earth of 0.16 AU on Oct. 14.  The
object does not appear bound to the solar system.  Williams also posted a
report by K. Meech on MPEC 2017-U183 saying that a very deep, stacked image
taken with the Very Large Telescope (no other details provided) shows 2017 U1
to be stellar in appearance.
     A. Fitzsimmons and M. Hyland, Queen's University, Belfast; R. Jedicke,
University of Hawaii; C. Snodgrass, Open University; and B. Yang, European
Southern Observatory, obtained optical spectroscopy of 2017 U1 on Oct. 25.95
UT with the 4.2-m William Herschel Telescope (+ ACAM imager/spectrograph).
Initial analysis shows a reflectance spectrum displaying a linear red slope
of 16 percent per 100 nm between 400 and 950 nm.  No gas emission or
mineralogical absorption features are apparent within the spectrum.  They
note that it appears similar to optical spectra of red objects in the
trans-Neptunian region.
     H. Sato, Tokyo, Japan, reports that seventy-two stacked 15-s CCD
exposures taken remotely on Oct. 22.3 UT with a 0.43-m f/6.8 astrograph near
Mayhill, NM, USA, yield mag 20.7, showing only stellar appearance.  Sato also
stacked eighty 15-s exposures taken on Oct. 22.5 with a 0.51-m f/6.8
astrograph at Siding Spring, NSW, that yield w-band mag 19.9 and also show
only stellar appearance.

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2017 CBAT
2017 October 29                  (CBET 4450)              Daniel W. E. Green

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