Latest Celestial mechanics Stories

2010-10-16 11:38:26

How do astronomers weigh a star that's trillions of miles away and way too big to fit on a bathroom scale? In most cases they can't, although they can get a best estimate using computer models of stellar structure.New work by astrophysicist David Kipping says that in special cases, we can weigh a star directly. If the star has a planet, and that planet has a moon, and both of them cross in front of their star, then we can measure their sizes and orbits to learn about the star."I often get...

2010-09-14 08:15:00

In August 1960, NASA launched its first communications satellite, Echo 1. Fifty years later, NASA has achieved another first by placing the ARTEMIS-P1 spacecraft into a unique orbit behind the moon, but not actually orbiting the moon itself. This type of orbit, called an Earth-Moon libration orbit, relies on a precise balancing of the Sun, Earth, and Moon gravity so that a spacecraft can orbit about a virtual location rather than about a planet or moon. The diagrams below show the full...

2010-08-12 20:12:02

There are places in space where the gravitational tug between a planet and the Sun balance out, allowing other smaller bodies to remain stable. These places are called Lagrangian points. So-called Trojan asteroids have been found in some of these stable spots near Jupiter and Neptune. Trojans share their planet's orbit and help astronomers understand how the planets formed and how the solar system evolved. Now Scott Sheppard at the Carnegie Institution's Department of Terrestrial Magnetism...

2010-06-10 06:00:00

For decades, researchers have been puzzled over the origins of Saturn's baby moons, which, according to many models, are so small that they should have been blown to pieces long ago by impacts with asteroids and comets. But a group of researchers from France and Britain now think they have the answer. Saturn's icy rings might have given birth to the planet's odd-shaped, small moons, scientists now believe. Scientists theorize that these unusual moons, some of which resemble flying saucers,...

2010-04-14 12:20:00

Two new and independent studies have put Einstein's General Theory of Relativity to the test like never before. These results, made using NASA's Chandra X-ray Observatory, show Einstein's theory is still the best game in town. Each team of scientists took advantage of extensive Chandra observations of galaxy clusters, the largest objects in the Universe bound together by gravity. One result undercuts a rival gravity model to General Relativity, while the other shows that Einstein's theory...

2010-04-06 13:57:48

In an analysis of the past 1.2 million years, UC Santa Barbara geologist Lorraine Lisiecki discovered a pattern that connects the regular changes of the Earth's orbital cycle to changes in the Earth's climate. The finding is reported in this week's issue of the scientific journal Nature Geoscience. Lisiecki performed her analysis of climate by examining ocean sediment cores. These cores come from 57 locations around the world. By analyzing sediments, scientists are able to chart the Earth's...

2010-03-11 08:51:40

Distant galaxy clusters mysteriously stream at a million miles per hour along a path roughly centered on the southern constellations Centaurus and Hydra. A new study led by Alexander Kashlinsky at NASA's Goddard Space Flight Center in Greenbelt, Md., tracks this collective motion -- dubbed the "dark flow" -- to twice the distance originally reported. "This is not something we set out to find, but we cannot make it go away," Kashlinsky said. "Now we see that it persists to much greater...

2010-03-11 07:40:00

Sloan Digital Survey data provide test that rules out alternative theories of gravity An analysis of more than 70,000 galaxies by University of California, Berkeley, University of Zurich and Princeton University physicists demonstrates that the universe "“ at least up to a distance of 3.5 billion light years from Earth "“ plays by the rules set out 95 years ago by Albert Einstein in his General Theory of Relativity. By calculating the clustering of these galaxies, which stretch...

2010-03-10 13:06:00

GREENBELT, Md., March 10 /PRNewswire-USNewswire/ -- Distant galaxy clusters mysteriously stream at a million miles per hour along a path roughly centered on the southern constellations Centaurus and Hydra. A new study led by Alexander Kashlinsky at NASA's Goddard Space Flight Center in Greenbelt, Md., tracks this collective motion -- dubbed the "dark flow" -- to twice the distance originally reported. (Logo: http://www.newscom.com/cgi-bin/prnh/20081007/38461LOGO) "This is not something...

2010-03-10 09:33:33

The Purple Mountain Observatory and the Department of Astronomy, Nanjing University, in Nanjing China-Research, cooperating with the Albert Einstein institute, in Hannover, Germany, put forward a model of the planar co-orbital circular restricted three-body problem, gave the equations of motion, a set of approximation formulas, and an approximate semi-analytical solution. The study is reported in Issue 53, No. 1 of SCIENCE CHINA Physics, Mechanics & Astronomy because of its significant...

Latest Celestial mechanics Reference Libraries

Earth Day
2012-04-23 12:12:49

Earth Day is a day early each year on which events are held to increase awareness and appreciation of the Earth’s natural environment. It is now coordinated worldwide through the Earth Day Network, founded by Dennis Hayes, and is celebrated in more than 175 countries every year. The United Nations designated April 22 as International Mother Earth Day in 2009, and will continue to be held each year on April 22 through at least 2015. The name and concept of Earth Day was allegedly...

2011-06-20 11:32:36

The Summer Solstice, or "Midsummer," derived from the Latin sol (sun) and sistere (to stand still), occurs exactly when the Earth's axial tilt is most inclined towards the sun at its maximum of 23° 26'. This is the time when the Sun is at its highest, or most northerly, point in the sky in the Northern Hemisphere. Except in the polar regions, where daylight is continuous for many months during the spring and summer, the day on which the Summer solstice occurs is the day of the year with...

2014-01-12 00:00:00

Sample Entry: Astronomy is the scientific study of stars, planets, comets, galaxies, and other phenomena that occur outside Earth's atmosphere (e.g. cosmic radiation). Astronomy deals with the evolution, physics, chemical makeup, meteorology, and motion of celestial objects, and also the formation of the universe. The word Astronomy comes from the Greek words astron (meaning "star") and nomos (meaning "law"). Astronomy is one of the oldest sciences. Since the dawn of man, people always...

2004-10-19 04:45:44

Autumnal Equinox -- In astronomy, is the equinox at the beginning of autumn in the northern hemisphere: the moment when the sun appears to cross the celestial equator, heading southward. The equinox occurs around September 22-24, varying slightly each year according to the 400 year cycle of leap years in the Gregorian Calendar. In the southern hemisphere, the equinox occurs at the same moment, but at the beginning of spring. There are two conventions for dealing with this: either the...

2004-10-19 04:45:44

Satellite -- A satellite is an object that orbits another object. With sufficient tangential velocity, the object does not collide with the primary object it orbits, but maintains a distance from that object as the rate at which it falls towards that object is similar to the rate that it travels away, thus the object orbits the primary object and becomes a satellite. In other words: gravitational force serves as the centripetal force needed to make the object circle the primary...

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Word of the Day
  • The hard inner (usually woody) layer of the pericarp of some fruits (as peaches or plums or cherries or olives) that contains the seed.
This word comes from the Greek 'endon,' in, within, plus the Greek 'kardia,' heart.