General knowledge of the Asteroid
The Asteroids are found in 1000km diameter of Solar system and can be any kind of shape.
Picture 1. Asteroids
98 percent of Asteroid are found in between Asteroid Belt of Mars and Jupiter. There are Asteroids that irrelative to Asteroid Belt also have different path than orbit path.
Picture 2. Asteroid Belt
Those are:
Near Earth Asteroids –The Asteroids are located in orbit’s path that intersect with Earth and Mars path or nearby it.
Trojans Asteroids – The Trojans Asteroids are located in Jupiter path or nearby Jupiter.
There are roughly 300000 Asteroids in Asteroid Belt, 11000 Asteroids nearby Earth by reliable source. The quantity of Asteroids will depend on their inverse N~D-2. The numbers go up when diameter decreases by this source. Asteroids can count up to millions. Most Asteroids diameter can be from 1 meter up to 1 km. Half of total mass of Asteroids are 400-500 km diameter and Pallas, Vesta, Hygiea diameter of 950 km also can be found in Ceres. Asteroids are small and have low mass because of the low gravity, that’s why they are any kind of shaped. In 1596 German scientist J.Kepler believed there should be planets in between Mars and Jupiter by his research study. The first Asteroid was found by Italian Astronomer G.Piazzi in 1801 and was the biggest out of all Asteroids also named Ceres. After 2006 Ceres was registered as a dwarf planet. Scientists had to face explanation of how Asteroids developed as there are many Asteroids. After started discovering Asteroids German scientist H.Olbers believed Asteroids are developed from blown-up pieces of big planets but there was disagreement by looking at his theory. After many years of research scientists Asteroids are not planets as they are not fully developed as a planet and by theory research they were right. The Asteroids in Asteroid Belt are not developed planets because of high mass of Jupiter gravity force. Big planets are developed when planet system started, small and tiny objects are developed from Asteroids bumping in to each other. Asteroids angular measure is too low so it’s impossible to observe the feature of physics from the ground. Can only measure the Asteroid`s light curves by ground observation. It’s necessary to get basic information about asteroids, sometimes called “minor planets”, from this light curves. So we use some indirect methods based on light curves chemical compositions, albedos and diameters of around 300 asteroids, and rotational and shape parameters of around 200 asteroids including polarimetry, spectrometry and photometry in order to determine physical parameters of asteroids. Currently in result of developing and implementing those methods, have been identified. In terms of chemical composition, asteroids are classified into three main groups. The relation between albedo or reflectance and chemical composition of asteroid is inseparable. Dark asteroids with an albedo of less than 0.06 are called C-type asteroids which are similar to carbonaceous achondrite in terms of reflectance and chemical composition. Fairly bright asteroids with an albedo between 0.06 and 0.23 are called S-type asteroids containing properties of inorganic substances. The albedo of M-type asteroids is the same as S-type asteroids, but they are composed of mostly metals and their polarities contain spectral features of metal. The ratio of C, S and M-type asteroids is 75% 15% 4%.
In addition to revolving around the sun in elliptical orbits, asteroids rotate around their principle axis. The time to complete on revolution around their axis is called the rotation period. The rotation periods for each asteroid are different from two or three hours to several days. For instance, 1566 Icarus (2.273 hours) and 321 Florentina (2.87 hours) have the shortest rotation period when it’s about 160 hours and 1150 hours for 1481 Tubingia and 288 Glauke respectively. When observing precisely asteroids, you can see that light curves is changing over time. The periodic function described this change is called the light curve.
Picture 3. Light curves of Asteroid
A typical light curve has two pairs of extremities (tow maximum and two minimum) in rotation. Light curve is basically defined by rotation period and amplitude of light curves for asteroids. Amplitude is difference between the highest and the lowest light curves values. Value of amplitude is not more than 0.3 or 0.4 units, average is usually 0.2 units. Asteroid with 1 unit amplitude is so rare. This change of light curves is caused by the rotation about its axis of the irregularly-shaped object. Therefore, most asteroids is represented by three-axis ellipsoid rotating around the lowest axis.
The time between adjacent maximum and minimum is equal to approximately one-quarter rotation period because a typical light curve has two pairs of extremities. If you couldn’t measure a full light curve at night, it’s possible to calculate rotation period in accordance with standard light curve identified by at least one maximum and minimum. In this manner, using light curve can determine rotational and shape parameters of steroids. Asteroids are the objects containing conditions for the formation of the solar system and chemical and physical properties of the first generations of planets formed. In this context, it is important to investigate certain stages in the formation of the solar system. Studying the asteroids come closer to Earth gives us the significant social and economic benefits, such as calculate the probability of collisions between those asteroids and Earth, anticipate potential hazards and evaluate degree of hazards. Also asteroids are studied in terms of sources of metals, raw materials and some minerals.
In Mongolia, we have started to observe asteroids through ORI-40 telescope since January, 2014 and registered as 075 observational point of asteroids in international Minor Planet Center on February 05, 2014. From initial observations, we have determined that range of light receptions is a stellar magnitude of 19.5~, in other word it’s difficult to observe more faint asteroids for ORI-40. This conclusion is so important to plan objectives and observations for the telescope. Now astrometry and photometric observations are made once or twice a month on the asteroids near Earth with a stellar magnitude of 19-30 observations confirming the position of the asteroids near Earth and 6 comet observations have been made from 2014 to 2016. The results of those observations have published in the electronic circular of Minor Planet Electronic Circular. Photometric observations take place on V-band of UBV photometric system in accordance with Johnson’s standard and amplitude and the stellar magnitude and amplitude are determined by establishing a combined light curve based on development CCD images through ASTPHOT and IRAF software.
To study physical properties of asteroids, it is used methods based on data of the light curve obtained from observations. The time between adjacent maximum and minimum is equal to approximately one-quarter rotation period because a typical light curve has two pairs of extremities. If you couldn’t measure a full light curve at night, it’s possible to calculate rotation period in accordance with standard light curve identified by at least one maximum and minimum. If convexity and concavity on surface of asteroids affect the light curve, it means the light curve depends primarily on shape of asteroids. Simple model of asteroids, give two pairs of extremities in rotation, is three-axis ellipsoid or half round cylinder.
Computing application is developing using MATLAB. After developed by MATLAB, it is possible to show 3 dimensional mapping for shape of asteroids and corresponding parameters.
