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TOPIC: (136108) 2003EL61
Blobrana


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RE: (136108) 2003EL61
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An unusual dwarf planet discovered in the outer Solar System could be en route to becoming the brightest comet ever known.
2003 EL61 is a large, dense, rugby-ball-shaped hunk of rock with a fast rotation rate.
Professor Mike Brown has calculated that the object could be due a close encounter with the planet Neptune.
If so, Neptune's gravity could catapult it into the inner Solar System as a short-period comet.

"If you came back in two million years, EL61 could well be a comet...When it becomes a comet, it will be the brightest we will ever see" -  Professor Brown, from the California Institute of Technology (Caltech) in Pasadena.

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Blobrana


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Rudolph and Blitzen
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S/2005 (136108) 1
S/2005 (2003 EL61) 1 (provisional designation; nicknamed "Rudolph" by the Caltech team), renamed S/2005 (136108) 1 once its primary was numbered, was the first satellite discovered around (136108) 2003 EL61. It orbits once every 49.12 ± 0.03 days with semimajor axis 49,500 ± 400 km and eccentricity 0.050 ± 0.003. Mutual occultations of the moon and the primary, as seen from Earth, occurred in 1999 and will not occur again until 2138.
Only the total mass of the system is known, but assuming the moon has the same density and albedo as the primary, the mass of the satellite is 1% of the mass of (136108) 2003 EL61 and it has a diameter of ~310 km.


S/2005 (136108) 2
S/2005 (2003 EL61) 2 (provisional designation), later renamed S/2005 (136108) 2, is the smaller inner satellite of (136108) 2003 EL61. The object has been nicknamed "Blitzen".

Its discovery was announced on November 29, 2005. It was found 39,300 km away and, with the assumption of a circular orbit, it orbits the primary in 34.1 ± 0.1 days, and is inclined 39 ± 6° from the larger moon.
The measured brightness implies a diameter 12% that of (136108) 2003 EL61, ~170 km, assuming similar albedo.

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Blobrana


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RE: New solar object
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Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase     V
2006 11 01    13 31.83   +18 59.5   51.989   51.186    35.7     0.6    17.4
2006 11 06    13 32.24   +18 58.4   51.952   51.186    39.0     0.7    17.4
2006 11 11    13 32.63   +18 57.5   51.910   51.185    42.6     0.8    17.5
2006 11 16    13 33.02   +18 56.9   51.861   51.184    46.4     0.8    17.5
2006 11 21    13 33.39   +18 56.6   51.808   51.184    50.4     0.9    17.5
2006 11 26    13 33.75   +18 56.5   51.750   51.183    54.5     0.9    17.5
2006 12 01    13 34.08   +18 56.8   51.688   51.183    58.7     0.9    17.5
2006 12 06    13 34.39   +18 57.3   51.621   51.182    63.0     1.0    17.5
2006 12 11    13 34.68   +18 58.1   51.552   51.181    67.4     1.0    17.5
2006 12 16    13 34.95   +18 59.2   51.479   51.181    71.8     1.0    17.5
2006 12 21    13 35.18   +19 00.6   51.405   51.180    76.3     1.1    17.5
2006 12 26    13 35.39   +19 02.2   51.328   51.179    80.8     1.1    17.5
2006 12 31    13 35.56   +19 04.1   51.250   51.179    85.3     1.1    17.5
2007 01 05    13 35.71   +19 06.2   51.172   51.178    89.8     1.1    17.5
2007 01 10    13 35.82   +19 08.5   51.094   51.178    94.3     1.1    17.5
2007 01 15    13 35.90   +19 11.0   51.016   51.177    98.9     1.1    17.4
2007 01 20    13 35.94   +19 13.7   50.940   51.176   103.4     1.1    17.4
2007 01 25    13 35.95   +19 16.6   50.865   51.176   107.9     1.0    17.4
2007 01 30    13 35.93   +19 19.6   50.793   51.175   112.3     1.0    17.4
2007 02 04    13 35.87   +19 22.7   50.723   51.174   116.7     1.0    17.4
2007 02 09    13 35.78   +19 25.9   50.657   51.174   121.1     0.9    17.4
2007 02 14    13 35.67   +19 29.1   50.596   51.173   125.4     0.9    17.4
2007 02 19    13 35.52   +19 32.3   50.538   51.173   129.5     0.9    17.4
2007 02 24    13 35.34   +19 35.6   50.485   51.172   133.5     0.8    17.4
2007 03 01    13 35.13   +19 38.8   50.438   51.171   137.4     0.8    17.4
2007 03 06    13 34.90   +19 42.0   50.396   51.171   141.0     0.7    17.4
2007 03 11    13 34.65   +19 45.1   50.361   51.170   144.3     0.6    17.4
2007 03 16    13 34.38   +19 48.1   50.331   51.169   147.2     0.6    17.4
2007 03 21    13 34.09   +19 50.9   50.308   51.169   149.5     0.6    17.4
2007 03 26    13 33.78   +19 53.6   50.291   51.168   151.3     0.5    17.4
2007 03 31    13 33.46   +19 56.1   50.281   51.168   152.3     0.5    17.4
2007 04 05    13 33.14   +19 58.4   50.278   51.167   152.5     0.5    17.4
2007 04 10    13 32.81   +20 00.5   50.281   51.166   151.9     0.5    17.4
2007 04 15    13 32.47   +20 02.4   50.291   51.166   150.4     0.6    17.4
2007 04 20    13 32.13   +20 04.0   50.307   51.165   148.4     0.6    17.4
2007 04 25    13 31.80   +20 05.3   50.330   51.164   145.8     0.6    17.4
2007 04 30    13 31.47   +20 06.4   50.359   51.164   142.7     0.7    17.4


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Blobrana


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Posts: 131433
Date:
2003 EL61
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With the controversy over the classification of Eris, Pluto, and "dwarf planets," a lesser known Kuiper Belt object (KBO) is vying to be the most interesting solar system object beyond Neptune. Soon after they found it, astronomers learned that 2003 EL61 is shockingly strange. Its spin period, just 3.9 hours, makes it the fastest rotating known body in our solar system larger than 100 kilometres across. Its shape is even weirder — it looks like a squashed American football, and at its widest point the highly elongated body likely exceeds even Eris's diameter. Astronomers also found two moons of it: an inner one with a 35-day non-circular orbit, and a brighter one in a 49-day circular orbit. Moreover, the object's density and rapid rotation imply that it is solid rock, with only the thinnest of icy veneers coating its surface.

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Blobrana


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Date:
(136108) 2003 EL61 Ephemeris
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Date       UT      R.A. (J2000) Decl.    Delta     r     El.    Ph.   V 
2006 09 25 000000 13 28 45.1 +19 15 30  52.071  51.191   28.4   0.5  17.4   
2006 09 26 000000 13 28 49.8 +19 14 55  52.073  51.191   28.1   0.5  17.4    
2006 09 27 000000 13 28 54.6 +19 14 21  52.075  51.190   27.8   0.5  17.4    
2006 09 28 000000 13 28 59.4 +19 13 48  52.077  51.190   27.5   0.5  17.4    
2006 09 29 000000 13 29 04.2 +19 13 14  52.079  51.190   27.3   0.5  17.4    
2006 09 30 000000 13 29 09.1 +19 12 42  52.080  51.190   27.0   0.5  17.4    
2006 10 01 000000 13 29 14.0 +19 12 09  52.081  51.190   26.9   0.5  17.4    
2006 10 02 000000 13 29 18.9 +19 11 37  52.082  51.190   26.7   0.5  17.4    
2006 10 03 000000 13 29 23.8 +19 11 06  52.083  51.190   26.6   0.5  17.4    
2006 10 04 000000 13 29 28.7 +19 10 35  52.083  51.190   26.5   0.5  17.4    
2006 10 05 000000 13 29 33.7 +19 10 04  52.083  51.189   26.4   0.5  17.4    
2006 10 06 000000 13 29 38.6 +19 09 34  52.083  51.189   26.4   0.5  17.4    
2006 10 07 000000 13 29 43.6 +19 09 04  52.083  51.189   26.4   0.5  17.4    
2006 10 08 000000 13 29 48.6 +19 08 35  52.082  51.189   26.4   0.5  17.4    
2006 10 09 000000 13 29 53.6 +19 08 06  52.081  51.189   26.5   0.5  17.4    
2006 10 10 000000 13 29 58.7 +19 07 38  52.080  51.189   26.6   0.5  17.4    
2006 10 11 000000 13 30 03.7 +19 07 10  52.078  51.189   26.7   0.5  17.4    
2006 10 12 000000 13 30 08.7 +19 06 43  52.077  51.189   26.9   0.5  17.4    
2006 10 13 000000 13 30 13.8 +19 06 16  52.075  51.189   27.1   0.5  17.4    
2006 10 14 000000 13 30 18.8 +19 05 50  52.073  51.188   27.3   0.5  17.4   
2006 10 15 000000 13 30 23.9 +19 05 24  52.070  51.188   27.6   0.5  17.4


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Blobrana


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Posts: 131433
Date:
2003EL61
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Title: The Surface of 2003EL61 in the Near Infrared
Authors: C. A. Trujillo, M. E. Brown, K. M. Barkume, E. L. Schaller, D. L. Rabinowitz
Date: 26 Jan 2006

Researchers report the detection of crystalline water ice on the surface of 2003EL61.
Reflectance spectra were collected from Gemini North telescope from 1.0 to 2.4 micron wavelength range, and from the Keck telescope across the 1.4 to 2.4 micron wavelength range. The signature of crystalline water ice is clear and obvious in all data collected. Like the surface of many outer solar system bodies, the surface of 2003EL61 is rich in crystalline water ice, which is energetically less favoured than amorphous water ice at cold temperatures, suggesting resurfacing processes may be taking place.
The near infrared colour of the object is much bluer than a pure water ice model. Adding a near infrared blue component such as hydrogen cyanide or phyllosilicate clays improves the fit considerably, with hydrogen cyanide providing the greatest improvement.
The addition of hydrated tholins and bitumens also improves the fit but is inconsistent with the neutral V-J reflectance of 2003EL61. A small decrease in reflectance beyond 2.3 micron may be attributable to cyanide salts.
Overall, the reflected light from 2003 EL61 is best fit by a model of 2/3 to 4/5 pure crystalline water ice and 1/3 to 1/5 near infrared blue component such as hydrogen cyanide or kaolinite. The surface of 2003 EL61 is unlikely to be covered by significant amounts of dark material such as carbon black, as their pure ice models reproduce published albedo estimates derived from the spin state of 2003 EL61.

Relative reflectance spectrum of 2003 EL61 from Gemini and Keck (black filled circles and x’s) normalised to the model. Overplotted is their best fit 100% pure crystalline water ice model with kaolinite clay at its true geometric albedo.
The dotted line is the water ice component and the solid gray line is the spectrum of kaolinite alone, shifted upwards by 0.1 for clarity.


Read more (345kb, PDF)

-- Edited by Blobrana at 07:54, 2006-05-08

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Blobrana


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Researchers believe the new moons coalesced from debris after another large KBO smashed into 2003 EL61 when the solar system was forming, more than 4 billion years ago. In their scenario, the crash heated 2003 EL61 so much that it lost most of its ice and was left as mostly rock. It also set the hot rock spinning so fast it got stretched into its cigar shape before cooling.

This may explain a few of the system's features. But the "tough question" is why the two tiny moons are in such different orbital planes.

"My best guess is that when both moons were closer, they gravitationally interacted and moved...My guess is that while many objects underwent collisions, only the most massive ones retained a disc of material out of which moons could coalesce" - Mike Brown, Caltech in Pasadena

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Blobrana


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RE: New solar object
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Observations reveal a double-peaked rotational light curve with period of 3.9154 ±0.0002 hours and peak to peak amplitude of about 0.28 ± 0.04 magnitudes.
The double peaks indicate an elongated object with large to small axis ratio of 1.4.
Observations also reveal a total length of 1960 - 2500 km, a mean density of 2600 - 3340 kg m-3, and a visual albedo greater than 0.6.
They also measured a neutral reflectance at visible wavelengths and a linear phase curve with slope varying from 0.09 mag deg-1 in the B band to 0.13 mag deg-1 in the I band.
The absolute V-band magnitude is 0.259 ± 0.028.

Observations made during 5 commissioning nights between 26 January and 30 June 2005 allow the researchers to derive the following orbital solution for the delta K=3.8 magnitude satellite with respect to the primary:

a=49100±400 km
P=49.05±0.03 days
e=0.048±0.002.

This implies a total mass of the system of 3.9±0.1 x 1021 kg, or 30.2±0.8% the mass of Pluto.

WebLink:

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Blobrana


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Posts: 131433
Date:
2003EL61
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Mike Brown has reported the discovery of a second satellite around 2003 EL61:

The first moon to 2003 EL61 was discovered on January 28th 2005 by observations at the Keck Observatory, the second satellite is fainter than the first, but still detected in three of the five images of the first satellite.


Credit Mike Brown

The orbits of the two satellites are seen almost edge on, which is why they look so elongated. The orbits are tilted to each other by about 40 degrees.



Both satellites appear to be quite small. The larger one is perhaps 1% of the mass of the primary while the smaller is only 0.2% of the mass of the primary.
The new satellite appears to circle 2003 EL61 once every 34 days.


Image of the new moons (above left and directly below).


“Two faint point sources are seen near 2003 EL61 on the image from the night of 2005 June 30, the night with the highest quality image correction.
The brighter source is the well-characterized satellite discovered by Brown et al. (2005a). The second source appears in each individual frame and is stationary to a measurement error of 4 pixels with respect to the KBO over 5 separate observations spaced by a total of 5 minutes.
A background star would have moved by 10 pixels during this time period. A faint source is also clearly seen in the full coadded observations of 2005 March 3. The source is too faint to be seen in individual exposures, but in two stacks of four 30 second exposures taken 6.8 minutes apart the source is also stationary to a measurement error of 4 pixels. A background star would have moved 25 pixels between these two observations.
Both of these sources are consistent with a relative brightness of 1:5 ± 0:5% the brightness of the primary. In the 2005 Mar 04 image a source consistent with this brightness is seen 0.3 arc seconds from the primary. The source remains stationary over a time period when a background star should have moved 23 pixels. At this small separation from the primary, PSF artefacts are possible, though no artefacts of this brightness are seen in any of the other LGS AO images, so we tentatively consider the detection real.
A source this faint would not have been detected in the lower quality 2005 Jan 26 image, but would have been seen at a separation greater than 0.4 arc seconds in the 2005 Mar 01 image.”


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First moon:
V magnitude 17.5
FWHM (arcseconds) 0.063
Strehl ratio 0.18
Satellite fractional brightness 5:9 ± 0:5%
Apparent semi-major axis (arcsec) 1.3
True semi-major axis (km) 49500


Second moon:
V magnitude 17.5
FWHM (arcseconds) 0.063
Strehl ratio 0.18
Satellite fractional brightness 1:5 ± 0:5
Apparent semi-major axis (arcsec) 1.0c
True semi-major axis (km) 39300c
Orbital period (days) 34.1c

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Blobrana


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Posts: 131433
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