02 - Full Moon
at 19:14 UT
05 - Taurid
(south) meteor shower peaks. Active
between 25 Sept and 25 Nov.
Associated with Comet 2P/Encke.
09 - Moon near
Mars (morning sky) at 14h UT. Mag. +0.3.
12 -Taurid (north) meteor
shower peaks. May produce the occasional
17 -Leonid meteor shower
peaks at 9h UT. Arises from debris ejected
Comet Tempel-Tuttle in 1533. Expect about 25
to 30 meteors per hour under
dark skies. Predictions of enhanced activity
between 21-22h UT on 17 Nov
(favours sky watchers in Asia).
21 -Alpha Monocerotid meteor
shower peaks at 15:25 UT. A usually minor
shower active 15-25 Nov. Radiant is near Procyon.
Predictions of enhanced
activity this year. Timing favours Far East
Asia, Australia and across the
Pacific to Alaska.
00 0 0
0 0 0//
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Saturday, July 19, 2008
New Video Sees Earth from Alien Perspective
NASA's Deep Impact spacecraft has made a movie of the moon passing in front of the Earth from the probe's vantage point millions of miles away.
Astronomers plan to use the video to develop techniques to look for Earth-like worlds in other solar systems.
"Making a video of Earth from so far away helps the search for other life-bearing planets in the universe by giving insights into how a distant, Earth-like alien world would appear to us," said Michael A'Hearn of the University of Maryland and the principal investigator for the Deep Impact extended mission.
Deep Impact, which sent an impactor into comet Tempel 1 on July 4, 2005, is currently 31 million miles away from Earth on its way to a flyby of comet Hartley 2 on Nov. 4, 2010.
During its cruise to Hartley 2, Deep Impact will be searching for extrasolar planets.
Deep Impact took several images of the Earth during a full planetary rotation; these images have been combined into a color video. During the video, the moon enters the frame as it orbits the Earth and then is shown transiting, or passing in front of, the Earth.
While other spacecraft, including Voyager 1 and Galileo, have imaged Earth and the moon from space, Deep Impact is the first to show a transit of Earth with enough detail to see large craters on the moon and oceans and continents on Earth.
"Our video shows some specific features that are important for observations of Earth-like planets orbiting other stars," said Drake Deming of NASA's Goddard Space Flight Center in Greenbelt, Md., and the deputy principal investigator for the extended mission. "A 'sun glint' can be seen in the movie, caused by light reflected from Earth's oceans, and similar glints to be observed from extrasolar planets could indicate alien oceans."
The team used infrared light to look at the Earth because plants reflect more strongly in the near-infrared, so the video will help scientists evaluate the potential for detecting vegetated land masses on alien planets.
Most of the nearly 300 extrasolar planets that have been found to date are Jupiter-sized behemoths, though a few "super-Earths," around four to nine times the mass of our planet, were recently detected.
NASA is currently studying planet-characterizing telescopes that would observe extrasolar planets as a single point of light and would distinguish land masses and oceans by changes in the total brightness, said planetary theorist Sara Seager of MIT and a co-investigator on the Deep impact extended mission.
NASA's Phoenix Mars Lander used its robotic arm to expose more of the hard icy layer just below the Martian surface so that it can more easily gather a sample of the material for analysis.
The trench, informally called "Snow White," was about 8 by 12 inches (20 by 30 centimeters) after digging by the arm Saturday. Mission controllers sent commands to the spacecraft Monday to further extend the length of the trench by about 6 inches (15 centimeters).
Scientists said tests in a lab on Earth suggested more area must be exposed in order to collect a proper sample.
Exploding asteroid theory strengthened by new clues
Was the course of life on the planet altered 12,900 years ago by a giant comet exploding over Canada? New evidence found by University of Cincinnati Assistant Professor of Anthropology Ken Tankersley and colleagues suggests the answer is affirmative.
Geological evidence found in Ohio and Indiana in recent weeks is strengthening the case to attribute what happened 12,900 years ago in North America - when the end of the last Ice Age unexpectedly turned into a phase of extinction for animals and humans - to a cataclysmic comet or asteroid explosion over top of Canada.
The solar system may not be a nice round shape, but rather a bit squashed and oblong, according to data from the Voyager 2 spacecraft exploring the solar system's outer limits, scientists said on Wednesday.
Launched in 1977, the Voyager 1 and Voyager 2 unmanned probes are now studying the edges of the heliosphere, the huge magnetic "bubble" around our solar system created by the solar wind as it runs up against the thin gas in interstellar space.
The solar wind is made up of electrically charged particles blown into space in all directions by the sun. The boundary between the heliosphere and the rest of interstellar space is known as the "termination shock."
Voyager 2 in August 2007 crossed this boundary 7.8 billion miles from the sun.
Voyager 1 had crossed the boundary in December 2004 about 10 billion miles away from Voyager 1 and almost a billion miles farther from the sun.
Scientists think this indicates that the bubble carved into interstellar space by the heliosphere, which extends well past the distant orbit of Pluto, is not perfectly round, and the solar system is shaped a bit like an oblong.
"Imagine a balloon is being blown up by the solar wind. You might imagine that if you took a balloon, which is mainly spherical, and pushed it against the wall, it would be blunted on one side," said Edward Stone of the California Institute of Technology, one of the scientists involved in the research.
That's what has happened with the heliosphere, he said.
The findings were published in the journal Nature.
The Voyager spacecraft were launched in 1977 with a mission to fly by and observe the giant planets Jupiter and Saturn. The two spacecraft then continued their mission into the outer solar system. They are flying through remote, cold and dark conditions, powered by long-life nuclear batteries in the absence of solar energy.
Oort cloud, is a postulated spherical cloud
of comets situated about 50,000 to 100,000 AU from
the Sun. This is approximately 1000 times the distance
from the Sun to Pluto or roughly one light year, almost
a quarter of the distance from the Sun to Proxima
Centauri, the star nearest the Sun. The Oort cloud
would have its inner disk at the ecliptic from the
Kuiper belt. Although no direct observations have
been made of such a cloud, it is believed to be the
source of most or all comets entering the inner solar
system (some short-period comets may come from the
Kuiper belt), based on observations of the orbits
of comets. Source: Wikipedia