Ladies and Gentlemen! Voyager 1 Has Left the Solar System!

BadBrain

I should have stated clearly in my original post that my statement on this matter represents a minority report, as the NASA people still say passage through the heliopause is yet to come. My statement is in accord with the criteria laid out for measuring passage through the heliopause and into the bow wave, which have clearly been satisfied per the measurements to which I refer in my original post.

mfb

For every distance, there is an ideal time to launch a probe to reach the destination :). For up to ~200 AU (and maybe more), I think Voyager will be first. And after that, I doubt that there are many interesting targets within 4 light years.

Dotini

Every once in a while I've heard it said that the Oort cloud is part of the solar system, presumably traveling along with us a light year or so off. I've also heard from NASA that the heliopause defines the limit of the solar system. Who's right? Is it a fact or merely a surmise that the Oort cloud really even exists? What would it mean if it doesn't exist? Could Voyager, or any device, make the trip to the Oort cloud and still keep on ticking? What sorts of instruments would be needed to verify the Oort cloud?

Respectfully submitted,
Steve

mfb

The Oort cloud is an area where (afaik) no objects are known today - and even if the cloud exists with objects of relevant mass, they would be so sparse that a mission will never hit one by chance. If we detect some objects there, they might become a target for a future mission.

BadBrain

Steve:

There's no conflict between those two contentions, as the heliopause lies beyond the Oort Cloud, enveloping a region known as the Heliosheath where only charged particles exist. The Heliosheath might be thought of as the Solar System's fuselage, resisting the dynamic pressure of the Interstellar Medium as the Solar System flies through it. In addition to a bow wave, the Heliosheath also has a "stern tail", giving the Solar System overall the shape of a teardrop or drop tank.

Dotini

Dear BadBrain,

Due to my hobbyist status and the august nature of the Physics Forum, I've never had the temerity to attempt a scientific correction of any statement I've ever found in the Physics Forum. However, I will do so now.

My research indicates the heliopause is being found a bit over 100 AU from the Sun.
Additional research shows the hypothesized Oort cloud is thought to be about a light year distant.

100 AU is about 15 billion kilometers
http://en.wikipedia.org/wiki/Heliosphere

1 light year is roughly 10 trillion kilometers (or about 6 trillion miles).
http://starchild.gsfc.nasa.gov/docs/...uestion19.html

Therefore, if my research and math are correct, the heliopause is well inside any Oort cloud, and my questions remain completely unanswered. I will continue looking into this small matter and let you know what I find.

Respectfully submitted,
Steve (distantly related to Kepler!?) :)

DaveC426913

I am not schooled on the specifics, but I think Dotini is correct. I understood that the Oort cloud in principle includes all objects out to the edge of Sol's gravity well, which extends halfway to Centauri.

arabianights

isn't the new boundary of solar system the Oort cloud? which is 1 ly and Voyager is still inside solar system by that definition.

BadBrain

Steve:

Thanks for the correction!

BadBrain

Steve:

I did a little further research of my own, and I found that the existence of the Oort Cloud may be irrelevant to a discussion of whether or not the Heliopause constitutes the outer edge of the Solar System, as the minor planet (if that's what she is) 90377 Sedna, undoubtedly part of the Solar System, has an aphelion of 937 AU, and a perihelion of 76.361 AU, which means that, barring the highly unlikely prospect of her orbit being perfectly aligned with the Heliopause's Tail Cone, she spends most of her orbit beyond the Heliopause.

I feel like I don't know anything anymore!

EDIT:

The Heliosphere now appears not to have a tail, per Cassini and IBEX. Boy do I feel like the dunce of the forum!

PhilDSP

Very interesting! But now where is the solar system heading towards? Can a rough direction be estimated?

DaveC426913

The Solar system is orbiting our galactic core; one revolution every 260 million years.

Actually, wiki has some interesting figures on its movement in the page's sidebar:
http://en.wikipedia.org/wiki/Milky_Way

Dotini

Many stars are found in the four arms of the Milky Way galaxy (duh). I think ours is a bit of an oddball, because instead of residing in one arm, it orbits through all four.

Respectfully,
Steve

DaveC426913

I am not sure that makes it an oddball. I believe the spiral arms are not fixed structures, but density variations, like the bars.

I should get a reference for that though.

BadBrain

Yep!

I'm thinking "zones of resonance" to describe the arms.

PhilDSP

Does this mean that since Voyager is encountering the solar system's bow wave (so to speak) where energy streams at an angle normal to the solar system's trajectory (solar apex), that Voyager's trajectory is within the hemisphere pointing at the star Vega and presumably closer towards Vega than the outer rim of the hemisphere?

DaveC426913

You could define such a hemisphere with Vega at its centre - but it would be a hemisphere 25 light years in radius and be dotted with a dozen other, closer stars. I don;t see what physical significance it would have.