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Astronomical Observatory: Cool Images


Named Calvin Asteroids : Asteroid 145475 Rehoboth

What event has just occurred?

What is the history of this asteroid?

Why was this name chosen?

What event has just occurred? Asteroid 145475 (2005 TP52), discovered 12 October 2005 by Calvin Prof. Larry Molnar, was officially given the name "Rehoboth" (Minor Planet Circular 59389, 2007 April 2).

What is the history of the asteroid? Asteroid Rehoboth was discovered on 12 October 2005 by Calvin professor Larry Molnar and given the provisional designation 2005 TP52. The discovery images were obtained with the purpose of obtaining additional measurements of 2005 SP243, which in turn was discovered pursuing 2005 SN58. Asteroid 2005 SN58 was discovered by Calvin College students in the introductory astronomy class Astronomy 111. (See separate web pages on the asteroid discovery lab and the table of asteroid discoveries.)

Additional observations over the following months allowed the determination of a good preliminary orbit. Using this, the Minor Planet Center was able to identify scattered observations made in 1998, 2000, and 2003 as also being of the same object. (Although the two nights of observations in October 2000 were enough to get a provisional designation, 2000 TZ30, the earlier data were too sparse to put together as all belonging to the same object.) A new, greatly refined, orbit based on the complete data set was then computed. Using it, we recovered the asteroid in November 2006 as it again approached opposition. With extensive sightings in November, the orbit was sufficiently established to receive its permanent designation, 145475, the following month.

Asteroid Rehoboth

The movie loop shows the asteroid as it appeared on October 22, 2005, a sequence of five images, one taken every 18 minutes. It condenses 1.2 hours of motion into 1.0 seconds. The asteroid is the faint point of light initially above and to the right of the bright star on the left and then gradually moving to the right and a bit down, crossing the center of the image. (The images are 3.7 by 2.3 arcminutes across; each one was a 300 second unfiltered exposure; north is up, east to the left; the coordinates of the asteroid in the first image are J2000 = (01:59:54.73, +12:19:44.1), which is in the constellation of Aries.) At that time the asteroid was very near opposition, and so moving rapidly (0.23 degrees/day) along the ecliptic in a retrograde (westerly) direction.

The asteroid resides in the midst of the main belt of asteroids (a = 2.77 AU), and has an orbit that is fairly circular (e = 0.02) and nearly coplanar (i = 2.99 degrees). It takes 4.62 years to orbit the Sun. Its absolute magnitude (H = 16.4) implies a size a little less than 3 km across. See an animated orbit of asteroid Rehoboth using a NASA web tool. For current position, distance, and brightness go to the Minor Planet Center Ephemeris page, type the name "Rehoboth" in the text box, and click on the "Get ephemerides" button.

Why was the specific name chosen? Once an asteroid has received its permanent numerical designation, it is the privilege of the discoverer to suggest a permanent name to the committee on nomenclature of the International Astronomical Union (IAU). Prof. Molnar, together with the Physics and Astronomy department, chose Rehoboth to honor the Rehoboth Christian School, located east of Gallup, New Mexico. This is the site of Calvin College's recently established, remotely operated observatory (which was used to discover the asteroid). The school has been very generous sharing their dark, clear southwestern skies with us. It is always a pleasure to visit. The formal citation as published by the IAU is as follows:

"Rehoboth Christian School (founded 1903) in northwest New Mexico primarily serves Native American families. The school is widely known for its high academic standards and Christian values as well as alumni leadership and achievement. The Rehoboth campus is the site of the Calvin-Rehoboth Observatory."

Rehoboth Christian School

The photograph shows the Rehoboh campus (at left) as viewed from the south. The beautiful New Mexico skyline can be seen behind it, including Church Rock on the far right. The pretty clouds are typical August afternoon weather. Click on the image to view a higher resolution version.

[Text by L. Molnar, posted 4/11/07.]


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