Red Barn Observatory MPC/IAU H68
Established 2006
A Practical Guide To Chasing Asteroids
For The Astrometrist
By: Steve E. Farmer Jr. & Marcelo Saavedra
Members of the Asteroid Hunters
So, you are interested in Asteroid chasing and learning how to perform Astrometry on these objects? Within this guide, we want to introduce you to this fascinating world. But be warned, Astrometry can be an addiction!!
This is a general guide to perform and organize an Asteroid study session and might change in some aspects due to astronomer experience, instrument setups, sky conditions, observatory characteristics and the type of object being observed. Nevertheless, this guide could be a useful aid to accelerate or improve the observing experience. Knowledge and certain skill using some astrometric software and planetarium programs are recommended when using this guide.
INTRODUCTION
Asteroids are a class of astronomical bodies or objects that orbit around the sun. The term "asteroid" comes from the Greek word meaning "star like" used in a common way to indicate the bodies are "wandering" around in the Solar System. The International Astronomical Union prefers to call them Minor Planet Bodies. They are also known as Planetoids ("planet-like") and more actually as Small Solar System Bodies (SSSB). This last term includes Comets, Centaurs, Trans Neptunian and other objects also. Today, the largest minor planets are called “Dwarf Planets”
Ceres was the first Asteroid discovered and it is the largest known to date. According to what we said before regarding the "largest minor planets", it is considered as a Dwarf Planet. It was discovered in 1801 by the director of the observatory of Palermo in Sicily, Giuseppe Piazzi. Notable asteroid hunters of this early era were J. R. Hind, Annibale de Gasparis, Robert Luther, H. M. S. Goldschmidt, Jean Chacornac, James Ferguson, Norman Robert Pogson, E. W. Tempel, J. C. Watson, C. H. F. Peters, A. Borrelly, J. Palisa, Paul Henry and Prosper Henry and Auguste Charlois. The pioneer on using photograph methods for Asteroid discovering was Max Wolf in 1891.
Asteroids come from different Solar System zones and they are identified according to these zones as follow:
MAIN BELT ASTEROIDS: They reside in a band between Mars and Jupiter orbits and are the most common and numerous of the asteroids.
NEA's (Near Earth Asteroids): Are those having orbits near to our planet. More than 4000 NEA's are known to date and are sub-divided into three groups: Amor, Apollo and Aten. The Amor group crosses Mars' orbit but not the Earth Orbit. Apollo and Aten Asteroids are crossing the Earth orbit in different periods: Apollo cross the Earth orbit in more than one year period. Aten do the same in less than a year.
JOVIANS: The Jovian Asteroids have orbits around the Sun following planet Jupiter.
CENTAURS: Orbit between Jupiter and Neptune.
TRANSNEPTUNIAN: Objects crossing Neptune orbit (very distant).
Nevertheless, Asteroids are classified into groups based on the characteristics of their orbits and on the details of the spectrum of sunlight they reflect.
These groups are known as “families” and are defined this way because they are sharing similar orbital elements, such as semi axis, eccentricity, and orbital inclination. It is customary to name a group of asteroids after the first member of that group to be discovered. Also, “cratering families” are distinguished and they are formed by ejecting fragments from Asteroid impacts. Thus we have families as Themis, Eos, Nemesis, Maria and others. The spectral classifications are defined by the Asteroid’s physical characteristics as colors, albedo, materials composition and spectral shape. They are known as taxonomic properties. The spectral classification was introduced by Clark Chapman, David Morrison, and Ben Zellner in 1975.
The near-Earth asteroid 433 Eros had been discovered as long ago as 1898, and the 1930s brought a flurry of similar objects. In order of discovery, these were: 1221 Amor, 1862 Apollo, 2101 Adonis, and finally 69230 Hermes, which approached within 0.005 AU of the Earth in 1937. Astronomers began to realize the possibilities of Earth impact. (Wikipedia)
All the Small Solar System Bodies (asteroids or comets), which are approaching within 1.3 astronomical units of the Sun (150 Millions Km or 96 millions Miles), are called and considered Near Earth Objects or NEOs.
Two events in later decades increased the level of alarm: the increasing acceptance of Walter Alvarez' theory of dinosaur extinction being due to an impact event, and the 1994 observation of Comet Shoemaker-Levy 9 crashing into Jupiter. The U.S. military also declassified the information that its military satellites, built to detect nuclear explosions, had detected hundreds of upper-atmosphere impacts by objects ranging from one to 10 meters across. All of these considerations helped spur the launch of highly efficient automated systems that consist of Charge-Coupled Device (CCD) cameras and computers directly connected to telescopes. Since 1998, a large majority of the asteroids have been discovered by such automated systems. (Wikipedia)
In spite of all the existing automated searching systems installed around the world and the well documented discovers until date, Asteroid searching and study continues within an area in which the Amateur astronomers have the opportunity to contribute and interact in a direct way with the professional Astronomy world.
The most collaborative practice today is Asteroid’s light curves. With them we can detect the way the Asteroids moves in the space, including its rotation movement. Asteroids can be grouped in systems of two and even three bodies interacting between them. These studies are a conjunction of Astrometry and Photometry given a more interesting fact to the Asteroid chasing world, but this kind of work demands more instrument power. More on Photometry can be found at the Palmer Divine Observatory
This Guide is still in the developing and correcting stage and will continue to develop as time passes. Please report any errors found to sefarmer[at]cometary[dot]net or caracasastronomica[at]gmail[dot]co.
Hope you enjoy and find this guide very useful.
Steve E. Farmer Jr. & Marcelo Saavedra
Chapter 1: Introduction to Astrometry
Chapter 2: Preparing the Observing Session
Chapter 4: At the Computer - Data Reductions
Chapter 5: How to Obtain an Observatory Code
Chapter 6: How to Image Fast Moving Objects
A Mirror Site To This Guide Can Be Found Here:
Copyright © 2006 The Cometary Space Web of Steve E. Farmer Jr.
Last modified 08/31/2010 02:23 PM -0700
This web site has been active since March 1, 2006
For Information send e-mail to INFO