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Title: ALMA Observations of Asteroid 3 Juno at 60 Kilometer Resolution
Author: T. R. Hunter (1), R. Kneissl (2,3), A. Moullet (1), C. L. Brogan (1), E. B. Fomalont (2,1), C. Vlahakis (2,3), Y. Asaki (4,5), D. Barkats (2,3), W. R. F. Dent (2,3), R. Hills (6), A. Hirota (2,4), J. A. Hodge (1), C. M. V. Impellizzeri (2,1), E. Liuzzo (7), R. Lucas (8), N. Marcelino (7), S. Matsu****a (9), K. Nakanishi (2,4), L. M. Perez (10), N. Phillips (2,3), A. M. S. Richards (11), I. Toledo (2), R. Aladro (3), D. Broguiere (12), J. R. Cortes (2,1), P. C. Cortes (2,1), V. Dhawan (10), D. Espada (2,4), F. Galarza (2), D. Garcia-Appadoo (2,3), L. Guzman-Ramirez (3), A. S. Hales (2,1), E. M. Humphreys (13), T. Jung (14), S. Kameno (2,4), R. A. Laing (13), S. Leon (2,3), G. Marconi (2,3), B. Nikolic (6), L. -A. Nyman (2,3), M. Radiszcz (2), A. Remijan (2,1), J. A. Rodon (3), T. Sawada (2,4), et al. (26 additional authors not shown)

We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum images of the asteroid 3 Juno obtained with an angular resolution of 0.042 arcseconds (60 km at 1.97 AU). The data were obtained over a single 4.4 hr interval, which covers 60% of the 7.2 hr rotation period, approximately centered on local transit. A sequence of ten consecutive images reveals continuous changes in the asteroid's profile and apparent shape, in good agreement with the sky projection of the three-dimensional model of the Database of Asteroid Models from Inversion Techniques. We measure a geometric mean diameter of 259pm4 km, in good agreement with past estimates from a variety of techniques and wavelengths. Due to the viewing angle and inclination of the rotational pole, the southern hemisphere dominates all of the images. The median peak brightness temperature is 215pm13 K, while the median over the whole surface is 197pm15 K. With the unprecedented resolution of ALMA, we find that the brightness temperature varies across the surface with higher values correlated to the subsolar point and afternoon areas, and lower values beyond the evening terminator. The dominance of the subsolar point is accentuated in the final four images, suggesting a reduction in the thermal inertia of the regolith at the corresponding longitudes, which are possibly correlated to the location of the putative large impact crater. These results demonstrate ALMA's potential to resolve thermal emission from the surface of main belt asteroids, and to measure accurately their position, geometric shape, rotational period, and soil characteristics.

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Asteroid (3) Juno in the constellation Hydra captured with a 100mm f5 refractor and EOS 350D camera on an EQ1 motorised mount.

Picture 045Asteroid Juno
  


Green + IR-cut filter. 
20 seconds, ISO 1600.



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Asteroid (3) Juno is at Opposition in the constellation Hydra on the 29th January 2015.

Magnitude: 8.1 
Distance to Earth: 1.334 AU 
Distance to Sun: 2.300 AU



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Occultation of HIP 43357 by Asteroid Juno on 19 November 2014

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On 2014 Nov 20, asteroid (3) Juno will occult a 7.4 mag star in the constellation Hydra for observers along a path across NE USA, S Canada.
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On 2013 Sep 2, asteroid (3) Juno will occult TYC 5741-02620-1  in the constellation Capricornus for observers in S. Africa.

http://asteroidoccultation.com/

 



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Asteroid (3) Juno is at Opposition in constellation the Aquarius on the 4th August, 2013. 

Magnitude: 9.0 
Distance to Earth: 1.703 AU
Distance to Sun center: 2.701 AU 

9432510100_d4fa411b4f_m.jpg



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Asteroid (3) Juno is at Opposition on the 19th May, 2012 

Magnitude: 10.2
Distance to Earth: 2.373 AU  
Distance to Sun center: 3.353 AU 


 

Ephemeris

Date       UT      R.A. (J2000) Decl.    Delta     r     El.    Ph.   V 
2012 05 18 000000 16 04 25.5 -03 09 43   2.374   3.353  162.6   5.2  10.2
2012 05 19 000000 16 03 35.8 -03 05 54   2.373   3.353  162.7   5.2  10.2
2012 05 20 000000 16 02 46.1 -03 02 13   2.373   3.353  162.7   5.2  10.2
2012 05 21 000000 16 01 56.2 -02 58 38   2.373   3.353  162.6   5.2  10.2
2012 05 22 000000 16 01 06.2 -02 55 10   2.373   3.352  162.5   5.2  10.2
2012 05 23 000000 16 00 16.3 -02 51 50   2.374   3.352  162.3   5.3  10.2
2012 05 24 000000 15 59 26.3 -02 48 37   2.374   3.352  162.0   5.4  10.2
2012 05 25 000000 15 58 36.5 -02 45 32   2.376   3.352  161.7   5.5  10.2
2012 05 26 000000 15 57 46.8 -02 42 35   2.377   3.352  161.3   5.6  10.2
2012 05 27 000000 15 56 57.2 -02 39 45   2.378   3.352  160.8   5.7  10.2
2012 05 28 000000 15 56 07.9 -02 37 03   2.380   3.352  160.3   5.9  10.2
2012 05 29 000000 15 55 18.8 -02 34 29   2.383   3.352  159.7   6.0  10.2
2012 05 30 000000 15 54 30.0 -02 32 04   2.385   3.352  159.1   6.2  10.2
2012 05 31 000000 15 53 41.6 -02 29 46   2.388   3.351  158.4   6.4  10.2
2012 06 01 000000 15 52 53.5 -02 27 37   2.391   3.351  157.7   6.6  10.2
2012 06 02 000000 15 52 05.8 -02 25 36   2.394   3.351  157.0   6.8  10.3
2012 06 03 000000 15 51 18.6 -02 23 43   2.398   3.351  156.2   7.0  10.3
2012 06 04 000000 15 50 31.9 -02 21 59   2.401   3.351  155.4   7.2  10.3
2012 06 05 000000 15 49 45.8 -02 20 23   2.405   3.351  154.6   7.5  10.3
2012 06 06 000000 15 49 00.1 -02 18 56   2.410   3.350  153.8   7.7  10.3
2012 06 07 000000 15 48 15.1 -02 17 37   2.414   3.350  152.9   7.9  10.3


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 Asteroid (3) Juno is Stationary on the 27th March, 2012.

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Asteroid (3) juno

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