APOD: 2004 August 27

[ElPelado]

Did you see today's APOD?
Here is the text:

The discovery of Sedna (aka 2003 VB12), the most distant known object orbiting the Sun, presents a mystery. Pluto's orbit averages about 40 AU in radius, where an AU (Astronomical Unit) is the Earth-Sun distance. But the closest point in Sedna's eccentric orbit scarcely comes within 75 AU, while its farthest point extends to nearly 1,000 AU. So how did something as large as Sedna get so far out there? Exploring the problem with computer simulations, astronomers Alessandro Morbidelli and Harold Levison suggest that while Sedna was not formed in its current location, it was also not moved there by encounters with other solar system objects. Instead, they find it more likely that Sedna resides in its present orbit because of an encounter with another star. In one scenario, objects like Sedna are yanked out of closer orbits by the gravitational pull of a Sun-sized star passing near the solar system during its formative years. Alternatively Sedna could have formed of material from another system entirely, captured during an early encounter with a much smaller star. Both Sedna-forming stellar encounter scenarios are consistent with idea that the Sun itself was born in an ancient, dense, cluster of stars.

Can someone explain me the bold part? I cant understand how a star can pass near an other one...

[selden]

El Pelado,

The orbits of stars within the galaxy are not very well coordinated. When stars first condense out of a cloud of dust and gas, for example, they are travelling in almost random directions relative to one another. Some of those stars will go by one another very closely.

Also, later, after the clusters of newly formed stars have gradually dispersed, over billions of years, stars will randomly pass near one another. Sometimes they'll pass at great distances, less often at very close distances. It is believed that this may be one cause for comets to be disturbed out of their orbits in the Oort cloud and fall into the inner solar system.

A recent study of the motions of more than 14,000 nearby stars has discovered that the orbits of the stars in our neighborhood are very different from one another. Take a look at http://www.eso.org/outreach/press-rel/pr-2004/pr-08-04.html
It's amazing there aren't more close encounters!

[Slalomsk8er]

BTW is there a star movement in Celestia, if not we need it as soon as eso give the data out of hand. If I am right no star movement meens no age of lion or aquarius and so on?

bye, Dominik

[selden]

Dominik,

Sorry, no: Celestia does not (yet?) display star motions.

Also, don't forget that the change of "Zodiacal Ages", formally called "precession of the equinoxes," is due to changes in the rotational axis of the Earth, not the motion of the stars on their own. Although Celestia accurately models the Earth's orbit for about +/- 2000 years around the current date, it does not (yet?) model the precession of its rotational axis. As a result, the precession of the equinoxes can't be seen.

[Slalomsk8er]

It is a shame not to have "precession of the equinoxes" as it renders the stonehenge addon nerly useless, as I wanted to look up the exact points plus time of the complex in a book my love has and study the stars like the druids BTW how exact is the stonhenge addon?

Then it was the indian yugas wich were coused by the motion of the solar system with syrius!? Kaliyuga (age of darkness and so on) is gone it is going up for us all. For you science heads this meens we get closer to the galaxy center and vibrations are going up (atom clocks wich had to be adjust more then regular in the last time and so on).

Ups now I am outed as an esoteric, Dominik