The discovery of 2003 SU224
Juan Lacruz, 7 Oct 2003
Serendipity
On September the 23rd Seiichi
Yoshida posted a message to comets-ml with comets awaiting for the first observation,
one of them was P/1999 DN3.
The next
weekend (2003.09.28) I went to the observatory and tried to image the comet
starting a series of 40 pictures 60 seconds each. Then I tracked and stacked
the frames using Astrometrica. That’s where serendipity comes into the scene, blinking
the stacks I didn’t find any trace of the comet but I noticed a, faint, moving
object some 8 arc min. off the comet’s position.
I Thought
it could be the comet so did the astrometry and sent the observations to the
minor planet center (MPC in short) with the comet’s designation. I sent another
e-mail to Seiichi asking him to check the observations, the result was that
Akimasa Nakamura and Kenji Muraoka did some calculations to confirm that the
object was NOT the comet and proposing it could be an asteroid.
Was it a
new object then?, I needed more observations to try to confirm it, I entered my
observations into the new object ephemeris generator service of the MPC to get
the predictions for further observations, this service computes an approximate
orbit (Väisälä) based on two or more positions provided by the observer, the
predictions are valid up to about three weeks, then the object starts to depart
more and more from the predicted position until it gets eventually lost.
The confirmation
All the
week long was raining. Finally, the 2003.10.03, some holes appeared in between
the clouds and I started another imaging session, after reduction I blinked the
images and saw nothing I thought it could have been just noise in the first
images or the object had been lost after a week without follow up.
The next
day I was analysing at home the latest images, when I noticed a very faint
moving object, I did the astrometry to find that the position and movement was
in agreement with that predicted by the MPC’s “New Object Ephemeris Generator”
based on the initial observations. I sent then the additional observations
together with these from the first night to MPC under my own temporary
designation.
|
COD
J87 LC30928 C2003 09
28.02198 23 33 54.54 -08 34
57.8 19.2
R J87 |
Some days
passed and I had no input from the MPC (later on I realized that my e-mail had
changed and the feedback was being sent to a no longer valid address), I
e-mailed Timothy Spahr at the MPC asking him about the object, he answered that
in a first instance he didn’t give a designation to the object due to large
residuals (errors in the position determination) but he did when he found a
couple of additional nights of observations and that the object discovery was
credited to J87. The packed provisional designation is K03SM4U.
Below is a
picture, courtesy of JPL, with the relative positions at the discovery date,
click on it to have a dynamical view of the orbit.
Below are the
orbital elements after these observations, according to the MPC minor planet
ephemeris service. A semimajor axis (a) about 3 together with an eccentricity (e)
very low (orbit nearly circular) and a not too high inclination (i) means this
asteroid is on the main belt between mars and jupiter.
|
2003 SU224 Epoch 2003 Sept. 18.0 TT = JDT 2452900.5 MPCM 104.92695 (2000.0) P Q n 0.18263485 Peri. 211.30082 -0.48430652 +0.87316328 a 3.0766655 Node 29.83611 -0.77809142 -0.40108249 e 0.0647998 Incl. 6.35542 -0.40002617 -0.27698143 P 5.40 H 15.2 G 0.15From 14 observations 2003 Sept. 16-Oct. 3. Residuals 20030916 644 0.1- 0.0+ 20030928 J87 2.2+ 0.2+ 20030928 704 0.2- 0.6+20030916 644 0.1- 0.0+ 20030928 J87 1.8- 1.1- 20030928 704 0.2- 0.6+20030916 644 0.0+ 0.1- 20030928 704 0.3+ 0.0+ 20030928 704 0.7+ 0.7+20030916 644 0.0+ 0.1- 20030928 704 0.3+ 0.0+ 20030928 704 0.7+ 0.7+20030916 644 0.0+ 0.1+ 20030928 704 0.6+ 0.5+ 20031003 J87 1.3- 0.4-20030916 644 0.0+ 0.1+ 20030928 704 0.6+ 0.5+ 20031003 J87 1.2+ 0.4+20030928 *J87 0.9- 0.4- 20030928 704 0.1- 0.1+20030928 J87 0.7- 0.6- 20030928 704 0.1- 0.1+
Last observed on 2003 Oct. 3.
Ephemeris below based on elements from MPEC 2003-T49. Further observations? Desirable between 2003 Nov.
13-22. |
Below is the observability chart
prepared, using the Lowell observatory online services, after the first
observations the nights of 28 Sept and 3 Nov, note the rapidly growing
uncertainty reaching beyond 1000 “ (lost?) after a few months,
According to the Lowell online
services, The observation strategy to get the asteroid numbered with a minimum
of observations consisted of six, from 2003 Dec 22 to 2014 Sep 30.
After some
more days of heavy rain, additional observations were done on the night of
October the 23rd and sent to the MPC with the new provisional
designation,
|
COD J87 AC2 juan_lacruz@yahoo.com
|
To reach
such a magnitude (about 21 in the red band) I had to track and stack 3 x 20 x
60 sec exposures i.e. one hour integration time.
The next day, observations since
April 1996 were linked by the MPC spanning a total of four oppositions (the
opposition is when the Earth passes in between the Sun and the Asteroid, it’s
the best time to view it). Here follows an extract from the MPES service, note
that the uncertainty
parameter U is equal to 1 meaning
small uncertainty (in this logarithmic scale 0 is very small uncertainty
and 9 is extremely large), according to the current mpc guidelines, in order to
get the asteroid numbered and then named, observations at four
oppositions(various nights in each) and a value of U less than or equal to 2
are needed.
|
2003 SU224 Epoch 2003 Dec. 27.0 TT = JDT 2453000.5 MPCM 122.72639 (2000.0) P Q n 0.18270166 Peri. 210.22066 -0.50498010 +0.86137045 a 3.0759154 Node 29.55241 -0.76785792 -0.41916878 e 0.0820227 Incl. 6.41423 -0.39419450 -0.28694683 P 5.39 H 15.5 G 0.15 U 1 From 23 observations at 4 oppositions, 1996-2003, mean residual 0".59. Residuals 19960413 691 0.1- 0.1+ 20030916 644 0.5- 0.0 20030928 704 0.1- 0.1+19960413 691 0.4+ 0.1+ 20030916 644 0.3- 0.1- 20030928 704 0.2- 0.6+19960413 691 0.1- 0.3+ 20030916 644 0.3- 0.1+ 20030928 704 0.7+ 0.7+19981029 691 0.3- 0.0 20030928 J87 0.9- 0.4- 20031003 J87 (3.1- 0.5+)19981029 691 0.1+ 0.1- 20030928 J87 0.6- 0.6- 20031003 J87 0.6- 1.3+19981029 691 0.1+ 0.4+ 20030928 J87 (2.3+ 0.2+) 20031023 J87 1.3+ 0.3-20010319 704 0.2+ 0.9+ 20030928 J87 1.7- 1.1- 20031023 J87 0.2+ 0.1+20010319 704 0.5+ 0.4+ 20030928 704 0.4+ 0.0 20031023 J87 1.4+ 0.4+20010319 704 (2.6+ 1.0+) 20030928 704 0.6+ 0.5+
Last observed on 2003 Oct. 23.
Perturbed ephemeris below based on elements from MPEC 2003-U57. Further observations? Very desirable between 2003 Nov.
22-Dec. 22. |
After the observations on the night
of 23 October when it was linked to observations in 1986 the Uncertainty
reduced dramatically to about 1” or less over many years on, anyhow the orbit
didn’t change that much.
The resulting strategy to get the
asteroid numbered, according to Lowell asteroid services didn’t prompt for any
observations needed.
Skymorph
On November the 1st I was
using Skymorph, a service of the Laboratory for High Energy
Astrophysics (LHEA) at NASA/ GSFC, to obtain images of the asteroid by
the NEAT project, I was lucky to find a triplet of images (2001.03.26) by the
AMOS telescope at Haleakala, Hawaii. I did the astrometry and sent it to MPC,
note the COD 608 meaning NEAT/Haleakala and MEAsurer J. Lacruz
|
COD 608
|
The observations were included that night,
as a result the mpes returned the residuals of the new observations and a
refined orbit, not very different from the previous one.
|
2003 SU224 Epoch 2003 Dec. 27.0 TT = JDT 2453000.5 MPCM 122.72635 (2000.0) P Q n 0.18270167 Peri. 210.22075 -0.50497935 +0.86137088 a 3.0759153 Node 29.55237 -0.76785818 -0.41916798 e 0.0820226 Incl. 6.41425 -0.39419496 -0.28694671 P 5.39 H 15.5 G 0.15 U 1 From 26 observations at 4 oppositions, 1996-2003, mean residual 0".56. Residuals 19960413 691 0.1- 0.1+ 20010326 608 0.0 0.2+ 20030928 704 0.6+ 0.5+19960413 691 0.4+ 0.1+ 20010326 608 0.3+ 0.1+ 20030928 704 0.1- 0.2+19960413 691 0.1- 0.3+ 20030916 644 0.5- 0.1+ 20030928 704 0.2- 0.6+19981029 691 0.3- 0.0 20030916 644 0.4- 0.1- 20030928 704 0.7+ 0.7+19981029 691 0.1+ 0.1- 20030916 644 0.4- 0.1+ 20031003 J87 (3.1- 0.5+)19981029 691 0.1+ 0.4+ 20030928 J87 0.9- 0.3- 20031003 J87 0.6- 1.3+20010319 704 0.1+ 0.9+ 20030928 J87 0.7- 0.6- 20031023 J87 1.3+ 0.3-20010319 704 0.4+ 0.4+ 20030928 J87 (2.2+ 0.2+) 20031023 J87 0.1+ 0.1+20010319 704 (2.5+ 1.0+) 20030928 J87 1.7- 1.0- 20031023 J87 1.4+ 0.5+20010326 608 0.2+ 0.2+ 20030928 704 0.4+ 0.1+
Last observed on 2003 Oct. 23.
Perturbed ephemeris below based on elements from MPEC 2003-V02. Further observations? Very desirable between 2003 Nov. 22-Dec.
22. |
The night of November the 17th
the sky was quite clear and there was an interesting object in the NEOCP list
(this resulted to be new comet C/2003 W1) I had to expose 90x60 sec pictures to
get two stacks with the object barely discernible at an acceptable signal to
noise ratio,
|
I was lucky to find more positions in NEAT images available from
SkyMorph
|
|
And some others were obtained by measuring
trails in DSS (Digital Sky Survey) plates
|
COD 260 MEA R.
Stoss NET
USNO-B1.0 ACK K03SM4U 260
AC2
rstoss@hrz1.hrz.tu-darmstadt.de COM
Trail very faint, segmented and ends not well defined K03SM4U 1996 04 21.55707
13 24 53.99 -08 11 09.8 260 K03SM4U 1996 04
21.60915 13 24 51.40 -08 11 01.8 260 COD 261 MEA
R. Stoss NET
USNO-B1.0 ACK
K03SM4U 261 AC2
rstoss@hrz1.hrz.tu-darmstadt.de COM
Trail quite faint and ends not well defined K03SM4U 1993 11 09.27292 03 06 19.57 +20 36 49.7 261 K03SM4U 1993 11 09.30070 03 06 18.13 +20 36 46.5 261 |
Now the asteroid is a five
oppositions object, further observation is not needed at the moment.
|
2003 SU224 Epoch 2003 Dec. 27.0 TT = JDT 2453000.5 MPCM 122.72734 (2000.0) P Q n 0.18270167 Peri. 210.22066 -0.50499417 +0.86136221 a 3.0759153 Node 29.55148 -0.76784973 -0.41918048 e 0.0820232 Incl. 6.41439 -0.39419244 -0.28695446 P 5.39 H 15.5 G 0.15 U 1 From 33 observations at 5 oppositions, 1993-2003, mean residual 0".66. Residuals 19931109 675 0.9- 0.6+ 20010319 704 0.3+ 0.3+ 20030928 704 0.3+ 0.019931109 675 0.2- 0.6+ 20010319 704 (2.4+ 0.9+) 20030928 704 0.5+ 0.5+19960324 566 0.0 1.1- 20010326 608 0.2+ 0.1+ 20030928 704 0.2- 0.1+19960413 691 0.5- 0.8+ 20010326 608 0.0 0.1+ 20030928 704 0.3- 0.6+19960413 691 0.0 0.9+ 20010326 608 0.2+ 0.0 20030928 704 0.6+ 0.6+19960413 691 0.5- 1.1+ 20030916 644 0.6- 0.0 20031003 J87 (3.2- 0.4+)19960421 413 0.9+ 0.1- 20030916 644 0.5- 0.1- 20031003 J87 0.7- 1.2+19960421 413 1.2+ 0.1+ 20030916 644 0.5- 0.1+ 20031023 J87 1.3+ 0.4-19981029 691 0.1+ 0.3- 20030928 J87 1.0- 0.4- 20031023 J87 0.1+ 0.019981029 691 0.6+ 0.3- 20030928 J87 0.7- 0.6- 20031023 J87 1.4+ 0.4+19981029 691 0.6+ 0.2+ 20030928 J87 (2.1+ 0.1+) 20031117 J87 0.4+ 1.7+20010319 704 0.0 0.8+ 20030928 J87 1.8- 1.1- 20031117 J87 0.2+ 0.8+
Last observed on 2003 Nov. 17. Perturbed
ephemeris below based on elements from MPEC 2003-X29. Further observations? None needed at this opposition. |
The current uncertainty is below one
arc second for the next ten years
The Numbering
One year passed and the asteroid was
observable again, I did further observations, Rafael Ferrando from observatory
Pla d’Arguines was able to image it as well, with the astrometry at a new
opposition, the new minor planet was officially numbered by the MPC on the 2004
October the 27th batch.
Conclusions:
International collaborative effort
over the internet is key point.
It is very remarkable how a
telescope just 30 cm in diameter is able to capture a magnitude about 21
asteroid by stacking frames with the appropriate software.
Recovering positions by carefully
inspecting archived images accelerates the process of getting the orbit secure
for possible numbering.
According to MPC the size of this
asteroid given H=15.5 and albedo 0.05 < a < 0.25 should be between 2 and
5 km.
Akcnowledgements :
MPC Minor Planet Center
Minor Planet Ephemeris Service has
been made possible by Process Software Corporation, and their excellent VMS Web
server, Purveyor. These calculations have been performed on the Tamkin Foundation Computing Network.
The Lowell Observatory
Asteroid
observability charts and asteroid observing strategy plans thanks to the Lowell
Observatory Asteroid Services.
JPL
Chart
with relative positions at the moment of discovery
Horizons system
NASA/NEAT
Skymorph
system http://skys.gsfc.nasa.gov/skymorph/skymorph.html
References :
Guide to Minor Body Astrometry
Minor Planet Ephemeris
Service