tno


Occultations by large trans-neptunians observable from Europe
from Dec. 2016 to Jan. 2018

Jean Lecacheux (Meudon, France)
2016 december 06



Worldmaps were obtained with OCCULT 4.2.4.4 (D. Herald), using the astorb.dat version of 2016 Nov. 15 (by L.H.Wasserman, Lowell Observatory) and the star catalogs Tycho-GAIA, GAIA14 (by D.Herald), URAT1 and UCAC4.

USED CRITERIONS

I first selected all the trans-neptunian objects (TNO) of absolute magnitude H < 5.7 according to the Minor Planet Center (MPC). Among them I only kept those having at the date of the 2017 solar opposition the one standard deviation (1 s.d.) minor semiaxis of their uncertainty ellipse smaller than 140 mas (main criterion) and the major semiaxis smaller then 500 mas (secondary criterion). I preferred this not classic selection to the traditional "U parameter" of orbit quality (from 0 to 9) calculated by the MPC. My sources of uncertainty ellipses were Horizons from the JPL and AstDys-2 at Pisa University, not the MPC. The uncertainty limits plotted as dashed lines by OCCULT have a fourth source: the "current ephemeris uncertainties" (CEU) provided by astorb.dat. Those various uncertainty estimations are in rough agreement, but never in detail.
[Recall: The terrestrial diameter seen from the trans-neptunian belt is between 370 and 500 mas typically, but drops a bit under 200 mas from 136199 Eris or 2014 UZ224, the currently known most distant bodies.]

Very limited override of above criterions was finally allowed, for various reasons, to ~10 % bodies lying slightly off limits.
Especially I decided to reinstate six bodies from the Rio & Meudon program which, for obscure reason, were falling off limits. So the entire Rio & Meudon program (the Centaurs excepted) now is covered by my predictions.

So has resulted a first list of 161 trans-neptunian objects. Then I added 134340 Pluto, a body in my selection inner core, but computed not with astorb.dat as all the asteroids, rather with DE435 (JPL Development Ephemeris) like a normal planet. In spite of small diameters (Charon excepted) I added the satellites of Pluto to my list. Then I also included Neptune, discarding many unobservable occultations of faint stars by the planet itself, but obviously keeping his major satellite Triton.
[Triton, although formally he is not a TNO, is comparable to many TNOs, is even larger than Pluto and Eris, has an atmosphere like Pluto, and will offer in Europe on 2017 Oct.05 a very interesting occultation of a mag. 12 star.]
Finally I also added te small TNO 2014 MU69, that the "New Horizons" spacecraft will fly-by on 2019 Jan. 01. But as its position uncertainty still is as large as 4 Earth diameters, I have added it only for the record.
[So, please, don't be obsessed by the 2017 Jul. 17 event I propose!]

Eventually my special file AsteroidElements.dat used by OCCULT contains 164 entries: 93 numbered bodies (among them 78 still with a provisional name), plus 71 not yet numbered.


A MOSTLY EUROPEAN-ORIENTED SELECTION

My prime purpose was to show only occultations of stars brighter than the V magnitude +16.5, and potentially observable from Europe and/or Canaries (whole Europe or only a part). Bright twilight always, close horizon often, were exclusion factors I systematically applied to discard many events. In contrast I was not careful of potential Full Moon neighbourhood; so users have to evaluate the moonshine impact by themselves.

In second lecture I added southern tropical regions from where European people observe occultations more and more often, either in remote mode or on site during stays: north of Chile and adjacent countries (especially north of Argentina and Brazil), plus oversea to the east: Namibia and Réunion island.

NB: I also plan a more worldwide selection including a large Pacific area (Australia + New Zealand, Japan, Hawaii...) with target stars up to the V magnitude +18.5. That would be distributed to interested people on request, through e-mailing of an OCCULT occelmnt file, i.e. a simple textfile of 540 bytes per occultation item, to be processed by OCCULT.

Please well realize that in matter of trans-neptunian events, possible large shift of the shadow path has to be anticipated everytime. For example a path predicted (and plotted) as crossing Africa in the vicinity of terrestrial Equator might end into observed occultation, either 100 mas to the south from South-Africa, or 100 mas to the north from southern Europe!
Similarly any path missing Earth at seemingly impressive distance has 50 % chance to be shifted inward. Sometimes it happens that the TNO occults the star, at low elevation in countries lying along the limb.


ABOUT THE ASTROMETRIC STAR CATALOGS

GAIA is just beginning a revolution, still very far from achievement. Of course I have used Tycho-GAIA and GAIA14 in absolute priority. However they are tiny provisional subsets of the future GAIA database, and only countain stars of magnitude R < 14.0. Unfortunately big trans-neptunian bodies occulting stars of R magnitude 13 or 12 are just a handful every year, and moreover occurrences for V < 12 are quite vanishing. Due to the almost homogeneous distribution of stars around the Sun, if we take complete inventory of all the V < 16.5 stars, only 17 % from them are brighter than R= 14.0, or 15 % brighter than V= 14.0. So joining some more complete old catalog was an absolute necessity for my 2017 trans-neptunian predictions.


Now what about the URAT1 and UCAC4?
[I thank D.Herald, for useful discussion about this thema]

UCAC4 has a faint stars technical limit R ~ 16.0 or R ~16.3, i.e. V ~ 16.5 or so.
URAT1 does not exist south from the declination -15 degrees, excepted around Pluto and 2014 MU69 until 2017.0.

Among all the V < 16.5 stars in the sky, 50 % stand between V=16.5 and V=15.6. As moving trans-neptunian bodies made perfect random drawing through the stars they encounter, it results that 50 % from all the potential occultations I have compiled are crowded within less than a 0.9 magnitude range under the UCAC4 technical limit ...

As now we reliably know - thanks to GAIA-DR1 and VizieR - the precise 2015.0 position of many V < 16.5 stars, then for a small (N ~ 40) sub-sample of my ~2100 V < 16.5 targets which are present in both UCAC4 and URAT1, I was able to compare how far from the GAIA reference are falling the UCAC4 and URAT1 calculated positions.

Thanks to this sub-sample, which, because of my V < 16.5 fixed condition, is automatically set around V ~ 16.0, I have discovered that UCAC4 is clearly under-performing relative to URAT1. In contrast, around the magnitude R ~ 13, URAT1 and UCAC4 have shown more equal performances, though I guess that URAT1 is still keeping some advantage.

So it turns out that around V= 16.0, UCAC4 is undoubtly working too close to its technical limit. In consequence I clearly had to choose URAT1. But I must replace URAT1 by UCAC4 in all the star fields more south than declination -15 (special case of Pluto excepted).

The URAT1 possess a technical limit higher by about 2 magnitudes than the UCAC4, as using a modern back-illuminated CCD definitely outperforming its predecessor. URAT1 also uses longer exposures, plus a redder filter than the UCAC4 (by ~100 nm), which a bit reduces the atmospheric turbulence and probably improves the image sharpness of the five elements lens. I guess that the URAT positions of mean epoch were nicely close to GAIA's ones, and, as now we only are three years or so after the mean epoch, that the positional blurring due to provisional proper motions have not yet erased the URAT initial advantage.


ABOUT THE STAR MAGNITUDES

The "Mv" magnitude reported in the worldmap header sometimes will seem contradicting my V < 16.5 rule. Actually one cannot accept as a valid V neither the G-magnitude of GAIA (a very wide 650 nm band), nor the instrumental UCAC4 and URAT1 magnitudes, as all these three magnitudes actually are approximations of R.
[NB: When OCCULT prints the same value for Mv, Mp and Mr, this is R again].
So, when possible, I took V from the most reliable source, the AAVSO APASS (accessed from VizieR or through Guide9).
In GAIA-DR1 the value "phot_g_mean" of the magnitude G is very interesting, as more accurate than anything else and probably homogeneous on the whole sky. G is a red magnitude, but knowing from any source the star colour (for example from 2MASS the infrared (J-Ks) colour index), one may derive thanks to G a refined approximation of V and Rc.
Solving the faint stars photometric puzzle by combining several catalogs will disappear with the publication of the GAIA multi-colour data.



2016_11_30 471196 2010 PK66.gif
2016_11_30 471196 2010 PK66

2016_12_02 307616 2003 QW90.gif
2016_12_02 307616 2003 QW90
2016_12_06 0 2014 WP509.gif
2016_12_06 0 2014 WP509
2016_12_08 145453 2005 RR43.gif
2016_12_08 145453 2005 RR43
2016_12_15 230965 2004 XA192.gif
2016_12_15 230965 2004 XA192

2016_12_17 0 2014 WT69.gif
2016_12_17 0 2014 WT69
2016_12_30 84922 2003 VS2.gif
2016_12_30 84922 2003 VS2
2016_12_31 0 2002 VT130.gif
2016_12_31 0 2002 VT130
2017_01_02 79360 Sila-Nunam.gif
2017_01_02 79360 Sila-Nunam

2017_01_04 0 2011 FX62.gif
2017_01_04 0 2011 FX62
2017_01_23 472231 2014 FU71.gif
2017_01_23 472231 2014 FU71
2017_01_27 50000 Quaoar.gif
2017_01_27 50000 Quaoar
2017_02_06 55565 2002 AW197.gif
2017_02_06 55565 2002 AW197

2017_02_08 119951 2002 KX14.gif
2017_02_08 119951 2002 KX14
2017_02_27 47171 1999 TC36.gif
2017_02_27 47171 1999 TC36
2017_03_13 445473 2010 VZ98.gif
2017_03_13 445473 2010 VZ98
2017_03_15 0 2011 FX62.gif
2017_03_15 0 2011 FX62

2017_03_19 55637 2002 UX25.gif
2017_03_19 55637 2002 UX25
2017_03_21 307261 2002 MS4.gif
2017_03_21 307261 2002 MS4
2017_03_28 0 2014 JP80.gif
2017_03_28 0 2014 JP80
2017_04_06 P9M05 Styx (V).gif
2017_04_06 P9M05 Styx (V)

2017_04_08 470596 2008 NW4.gif
2017_04_08 470596 2008 NW4
2017_04_13 0 2014 WP509.gif
2017_04_13 0 2014 WP509
2017_04_13 0 2015 AN281.gif
2017_04_13 0 2015 AN281
2017_05_06 278361 2007 JJ43.gif
2017_05_06 278361 2007 JJ43

2017_05_09 28978 Ixion a.gif
2017_05_09 28978 Ixion a
2017_05_09 28978 Ixion b.gif
2017_05_09 28978 Ixion b
2017_05_14 0 2014 JW80.gif
2017_05_14 0 2014 JW80
2017_05_14 119951 2002 KX14.gif
2017_05_14 119951 2002 KX14

2017_05_18 308193 2005 CB79.gif
2017_05_18 308193 2005 CB79
2017_05_20 28978 Ixion.gif
2017_05_20 28978 Ixion
2017_05_20 307261 2002 MS4.gif
2017_05_20 307261 2002 MS4
2017_05_22 444745 2007 JF43.gif
2017_05_22 444745 2007 JF43

2017_06_01 307251 2002 KW14.gif
2017_06_01 307251 2002 KW14
2017_06_02 307251 2002 KW14.gif
2017_06_02 307251 2002 KW14
2017_06_06 0 2014 EZ51.gif
2017_06_06 0 2014 EZ51
2017_06_07 55636 2002 TX300.gif
2017_06_07 55636 2002 TX300

2017_06_07 90568 2004 GV9.gif
2017_06_07 90568 2004 GV9
2017_06_13 0 2014 BZ57.gif
2017_06_13 0 2014 BZ57
2017_06_21 230965 2004 XA192.gif
2017_06_21 230965 2004 XA192
2017_06_23 P9M00 Pluto.gif
2017_06_23 P9M00 Pluto

2017_06_27 24835 1995 SM55.gif
2017_06_27 24835 1995 SM55
2017_07_04 P9M00 Pluto.gif
2017_07_04 P9M00 Pluto
2017_07_12 0 2014 MY69.gif
2017_07_12 0 2014 MY69
2017_07_17 0 2014 MU69.gif
2017_07_17 0 2014 MU69

2017_07_21 470316 2007 OC10.gif
2017_07_21 470316 2007 OC10
2017_07_26 0 2003 UY413.gif
2017_07_26 0 2003 UY413
2017_07_28 90568 2004 GV9.gif
2017_07_28 90568 2004 GV9
2017_07_28 307261 2002 MS4 a.gif
2017_07_28 307261 2002 MS4 a

2017_07_28 307261 2002 MS4 b.gif
2017_07_28 307261 2002 MS4 b
2017_08_10 84922 2003 VS2.gif
2017_08_10 84922 2003 VS2
2017_08_10 230965 2004 XA192.gif
2017_08_10 230965 2004 XA192
2017_08_11 0 2010 ER65.gif
2017_08_11 0 2010 ER65

2017_08_25 0 2014 HZ199.gif
2017_08_25 0 2014 HZ199
2017_09_04 470316 2007 OC10.gif
2017_09_04 470316 2007 OC10
2017_09_06 0 2014 TD86.gif
2017_09_06 0 2014 TD86
2017_09_11 307616 2003 QW90.gif
2017_09_11 307616 2003 QW90

2017_09_12 0 2014 WT69.gif
2017_09_12 0 2014 WT69
2017_09_13 48639 1995 TL8.gif
2017_09_13 48639 1995 TL8
2017_09_23 307251 2002 KW14.gif
2017_09_23 307251 2002 KW14
2017_09_28 35671 1998 SN165.gif
2017_09_28 35671 1998 SN165

2017_10_01 470316 2007 OC10.gif
2017_10_01 470316 2007 OC10
2017_10_04 307251 2002 KW14.gif
2017_10_04 307251 2002 KW14
2017_10_05 P8M01 Triton (I).gif
2017_10_05 P8M01 Triton (I)
2017_10_06 0 2014 JJ80.gif
2017_10_06 0 2014 JJ80

2017_10_09 50000 Quaoar.gif
2017_10_09 50000 Quaoar
2017_10_20 0 2014 WT69.gif
2017_10_20 0 2014 WT69
2017_10_22 55638 2002 VE95.gif
2017_10_22 55638 2002 VE95
2017_10_27 P9M02 Nix (II).gif
2017_10_27 P9M02 Nix (II)

2017_10_28 50000 Quaoar.gif
2017_10_28 50000 Quaoar
2017_11_11 470599 2008 OG19.gif
2017_11_11 470599 2008 OG19
2017_11_18 0 2009 YG19.gif
2017_11_18 0 2009 YG19
2017_11_26 0 2013 XC26.gif
2017_11_26 0 2013 XC26

2017_11_27 24835 1995 SM55.gif
2017_11_27 24835 1995 SM55
2017_11_28 0 2014 WP509.gif
2017_11_28 0 2014 WP509
2017_12_01 84522 2002 TC302.gif
2017_12_01 84522 2002 TC302
2017_12_02 145451 2005 RM43.gif
2017_12_02 145451 2005 RM43

2017_12_03 0 2014 QY441.gif
2017_12_03 0 2014 QY441
2017_12_10 55638 2002 VE95.gif
2017_12_10 55638 2002 VE95
2017_12_12 0 2010 TY53.gif
2017_12_12 0 2010 TY53
2017_12_12 55637 2002 UX25.gif
2017_12_12 55637 2002 UX25

2017_12_13 230965 2004 XA192.gif
2017_12_13 230965 2004 XA192
2018_01_03 55638 2002 VE95.gif
2018_01_03 55638 2002 VE95
2018_01_12 0 2009 YG19.gif
2018_01_12 0 2009 YG19
2018_01_15 0 2014 TD86.gif
2018_01_15 0 2014 TD86

2018_01_16 0 2014 QY441.gif
2018_01_16 0 2014 QY441
2018_01_18 119951 2002 KX14.gif
2018_01_18 119951 2002 KX14
2018_01_22 119979 2002 WC19.gif
2018_01_22 119979 2002 WC19
2018_01_29 0 2011 FX62.gif
2018_01_29 0 2011 FX62

2018_01_31 0 2012 HG84.gif
2018_01_31 0 2012 HG84
2018_02_04 0 2002 VT130.gif
2018_02_04 0 2002 VT130
2018_02_09 0 2012 HG84.gif
2018_02_09 0 2012 HG84