Second Moon for the Earth

A point of light leaving a trace on the camera chip's Catalina Sky Survey in Arizona. Thursday evening, 14 September 2006, scientists witnessed a 2.3-meter-diameter asteroid the size of small cars are being completed one revolution around the earth. Celestial bodies named 2006 RH120 was later known as the second moon of the earth.

But the title as the companion of the earth does not apply forever. In July 2007, the satellite is divorced with earth after the "dance" together for 11 months.

Asteroid is not really the second moon, the first, or last for the earth. In the past century, astronomers witnessed a number of turns around the earth asteroids.

In 1913, C.A. Chant, who lived in North America, saw "a large meteor" revolve around the earth at an altitude of 4184 kilometers on a nearly circular orbit. Flakes of space rocks are also observed around the Earth in 1991. Its small size makes this object is estimated to result in an asteroid collision with Earth's gravity ejected and trapped.

In a recent study by the Institute for Astronomy, University of Hawaii, which turned into celestial bodies orbiting the earth is known as a temporary satellite capture. Satellite catches generally occur because the asteroid orbits nearly tangent to the orbit of the earth. Consequently, when it was very close, the asteroid will be trapped by Earth's gravity.

There is a possibility of the existence of the satellite is indeed a very big catch. Astronomers have long recognized tens of thousands of asteroids, meteoroids, and comets near the Earth. These objects swept many parts of the sky and the earth's orbit and potentially touching a satellite captive catchment.

"There are many asteroids in the solar system, so the chances of the earth to pull one of them is not surprising," said Jeremie Vauballion, an astronomer at the Paris Observatory, France.

Vauballion is one of the astronomers who support the idea that the earth is always surrounded by two months, not just one, as believed so far. The first month is the month that reflect sunlight and illuminate the night sky, while the second is the moon-sized space rocks at least 1 meter that surrounds our earth. The idea is published by a number of scientists in scientific journals ICARUS.

Under their scenario, a space object that mimics the routines moon rotates around the earth. The difference, "second month" is not always around the earth.

"In these two always come and go," said Mikael Gravnik, physicists from the University of Helsinki and the principal investigator for the report.

He has good reason to explain the mortality satellite catches it. Computer simulations show that he did catch the satellite can survive up to 890 years in Earth orbit. While 99.9 percent of the second moon requires 400 days to circle the earth. After that, the stability of the satellite orbit disturbed and re-released and free surfing in outer space.

Although only temporary, satellite catches pose a threat to the inhabitants of the earth. Approximately 1 percent of the catch was confirmed satellite falls to earth. There is a possibility of increasing the intensity of collisions in the asteroid satellites are able to survive much longer in orbit.

"Every year there are 10 satellites catch that fell to earth. This figure is very high," said Gravnik. The greater threat with increasing duration of the satellite orbit catches. For example, satellite catches that lasts six years would have increased the potential for collision with earth up to 18 percent.

Research on the population of temporary satellite capture are generally clustered on the size of 3 meters, 1 meter, and 0.2 meters. With a small enough size, the satellites capture dim glow that astronomers are guaranteed trouble detecting movement.

"When approaching the earth, a space object motion is too fast to be detected," he said. Luckily, these items will generally be burned out when they want to pierce the earth's atmosphere.

Not only brings the potential for disaster, the second month it also has other uses. Since 1957, researchers believe could be fitted with a temporary catch satellite telemetry device that turned into an artificial satellite.

Astronomy researchers from Southwest Research Institute in Boulder, Colombia, Clark Chapman, mentions this idea will save the cost of space travel. "It does not take a rocket size to embed satellite equipment in the catch. Mileage will also be shorter," he said. *** [ANTON WILLIAM | LIVESCIENCE | SPACE | KORAN TEMPO 3749]

Determining Size of Asteroids

This chart illustrates how infrared used to accurately measure asteroid sizes.

On the top chart, the three asteroids of various sizes look the same when viewed in visible light. This occurs because the visible light from the Sun is deflected by a stone surface. The more reflective, or a shiny object, the more light is refracted. Based on the feature called the albedo, the darker an object, sun light reflected also becoming small, so large and dark asteroids will appear by the telescope as a small asteroid. Thus, the brilliance of an asteroid in visible light strongly influenced by the albedo and size.

Chart below shows the same three asteroids when viewed using an infrared telescope. Direct infrared heat detector detects an object, thus directly related to its size. Larger stones will appear more brilliant.

In this case, the level of brightness is not unduly influenced by the albedo, or surface brightness. When the measurement of visible and infrared light combined, albedo asteroids can be measured more accurately. *** [NASA | KORAN TEMPO 3749]