Tag: asteroid occultation

Does 790 Pretoria Have a Moon?

On 14 Dec 2023 at 10:17:12.943 UT, the 13.6-magnitude outer main belt asteroid 790 Pretoria was in the middle of covering up the 10.9-magnitude star TYC 1299-730-1 (UCAC4 532-018101) in the constellation Taurus, as seen from my vantage point on the west side of Tucson, Arizona.

Stellar Occultation of TYC 1299-730-1 by 790 Pretoria

I observed a 6.6-second occultation, but noticed a single-point event with the same magnitude drop as the main occultation, but 0.5 second earlier. A close up of that section of the light curve is shown below.

Stellar Occultation of TYC 1299-730-1 by 790 Pretoria showing possible moonlet

If 790 Pretoria has a moon that also occulted the star, then you would expect the magnitude drop when the star is covered up to be the same—the magnitude of the asteroid (and its satellite) alone. This is indeed the case here.

An analysis of all the data points prior to these two occultation events indicates that there is only a 1/130,000 chance that the single-point dip was caused by noise. The time-resolution of each data point is 0.03 seconds, so it seems likely that the moonlet occultation event was very close to 0.03 seconds in duration, as the data points on either side fall comfortably within the baseline.

Originally, there were four other observers signed up for this event (three in Arizona and two in Texas), but the other two Arizona observers were not able to observe and the two Texas observers were clouded out, leaving only me with my 8-inch Meade LX90 telescope on the back patio of my home to observe the event.

No moon of 790 Pretoria has yet been reported, and since no one else observed the 14 Dec 2023 event, my observation can only serve as a suggestion that 790 Pretoria might have a moon, but not proof.

Prior to my observation there were 14 stellar occultation events of 790 Pretoria observed, the first in 1998 and the last in 2021. We don’t yet have a shape model for 790 Pretoria.

Only three light curves from previous 790 Pretoria occultation events are available through the VizieR archive. These are listed and shown below.

VizieR Light Curves of previous stellar occultations by 790 Pretoria
LC 238 by R. Sandy
LC 7658 by Dean Hooper
LC 7939 by S. Messner

Here is a list of all previous occultation chords for 790 Pretoria.

And details of the North American events, including the 14 Dec 2023 event I observed.

The 19 Jul 2009 event resulted in the discovery that TYC 2255-01354-1 is a double star.

Desiderata

The word desideratum has been a part of the English language since at least 1651, according to the Oxford English Dictionary, which provides this definition:

Something for which a desire or longing is felt; something wanting and required or desired.

This word comes from the Latin dēsīderātum “thing desired”, and its plural is desiderata.

The French astronomer Auguste Charlois (1864-1910) discovered the asteroid 344 Desiderata on 15 Nov 1892 at the Nice Observatory, in southeastern France near the border with Italy. Like most of his 99 asteroid discoveries between 1887 and 1904, it is named to honor a woman. In this case, that would be Désirée Clary (1777-1860), French woman who became Queen Desideria of Sweden.

On 25 Feb 2019, I recorded 14.1-magnitude 344 Desiderata passing in front of the 14.6-magnitude star UCAC4 639-020401 in the constellation Auriga. Right before the event, star and asteroid formed a 13.6-magnitude blended image, and when the asteroid covered up the star, the brightness dipped 0.5 magnitude to the brightness of the asteroid alone. This great cover-up event lasted 16.8 seconds. Here’s a light curve of the event as a function of time.

Light curve of asteroid 344 Desiderata passing in front of UCAC4 639-020401 in Auriga

That dip to the right (after) the asteroid covered up the star suggests that a smaller satellite of the asteroid might have also passed in front of the star. Alas, it is only noise. We can tell this by looking at the light curve of a nearby comparison star at the same time.

Wind gust caused a dip in brightness of both stars at the same time after the main occultation event
A view of just the comparison star clearly showing the dip in brightness from a wind gust

Here is the smoothed and fitted light curve of the asteroid occultation event.

Asteroid occultation of the star UCAC4 639-020401 by the asteroid 344 Desiderata on 25 Feb 2019

Max Ehrmann (1872-1945) wrote a prose poem Desiderata (Latin: “things desired”) in 1927 that has since become well known, and for good reason.

Desiderata

Go placidly amid the noise and the haste, and remember what peace there may be in silence.  As far as possible, without surrender, be on good terms with all persons.

Speak your truth quietly and clearly; and listen to others, even to the dull and the ignorant; they too have their story.

Avoid loud and aggressive persons; they are vexatious to the  spirit.  If you compare yourself with others, you may become vain or bitter, for always there will be greater and lesser persons than yourself.

Enjoy your achievements as well as your plans.  Keep interested in  your own career, however humble; it is a real possession in the changing fortunes of time.

Exercise caution in your business affairs, for the world is full of trickery.  But let this not blind you to what virtue there is; many persons strive for high ideals, and everywhere life is full of heroism.

Be yourself.  Especially do not feign affection.  Neither be cynical about love; for in the face of all aridity and disenchantment, it is as perennial as the grass.

Take kindly the counsel of the years, gracefully surrendering the things of youth.

Nurture strength of spirit to shield you in sudden misfortune.  But do not distress yourself with dark imaginings.  Many fears are born of fatigue and loneliness.

Beyond a wholesome discipline, be gentle with yourself.  You are a child of the universe no less than the trees and the stars; you have a right to be here.

And whether or not it is clear to you, no doubt the universe is unfolding as it should.  Therefore be at peace with God, whatever you conceive Him to be.  And whatever your labors and aspirations, in the noisy confusion of life, keep peace in your soul.  With all its sham, drudgery and broken dreams, it is still a beautiful world.  Be cheerful.  Strive to be happy.