Bug Bites Herpes Body

COURSE Introduction to Astronomy (40)

asteroids.

In 1920, K. Hirayama noted that some asteroids had some of their orbital elements grouped in the family. A family comprising a main asteroid which gives its name and a tag associated with much smaller asteroids. For example, the family associated to 8 Flora (160 km) is the most popular and populated as it is known more than 400 members, the family of 24 Themis (200 km) has 150 members, of which three are over 100 km . as 90 Antiope, 268 Adorea, 171 Ophelia.
At the orbit of Jupiter, about Langraje points, one at 60 ° before the gas giant and the other at 60 degrees behind it, is a group of asteroids called Greeks and Trojans each other.
If a diagram is represented in abundance asteroid as a function of distance from the Sun, is that the distribution is discontinuous, gaps or voids exist asteroid, caused by the gravitational action of Jupiter. These gaps or sparsely populated regions of called "Kirtwood Lagoons." The classic explanation is that the attraction of Jupiter eliminates the effect of resonance orbits whose period is a rational fraction of theirs. For example, objects that have a semi-major axis of 2.50 AU, run three laps around the sun at the same time that Jupiter runs a twist: the resonance 3 / 1, other resonances are 2 / 1, 3 / 2. The farther away from the main belt stabilizer is more resonance.
Today know one small asteroids whose orbits are very close to Earth's orbit at high speed, are called "Aten-Apollo-Amor" and distinguished into several categories:
1) The bodies whose orbits pass close to the planet Mars and the asteroid Hungaria.
2) objects whose perihelion is closer to the Sun than Mars, often called "Mars-crossers." These are subdivided into four subsets:
2.1) Those who do not come to less than 1.20 AU from the Sun
2.2) Those that pass near the Earth but not deep into Earth's orbit, its prototype is 2.3
Love 1221 ) Those who enter the Earth's orbit and have a longer period a year. Its prototype is 1862 Apollo.
2.4) Same as 2.3 but with an orbital period less than one year. Typical example: 2062 Aten.
must know that 75% of the asteroids are concentrated in the zodiac (defined as a band of apparent width 15 ° centered on the ecliptic). Most of them are too weak to be detected by an amateur telescope, only a few, the brightest, m can be realized. For this, consult the ephemeris of astronomical journals and astronomy software.