Celestia Forums

Whenever articles are written lately about the Voyager spacecraft, they usually refer to them as "leaving the solar system", or "approaching the boundary of our solar system", as if the event will come soon. In fact, NASA claims on one of its sites that "Voyager is reaching the edge of the solar system". On that same NASA website, they refer to the Heliopause as the edge of the sun's influence, and when Voyager reaches it, it will be in "interstellar space". Presumably that means the outer edge of the solar system. Here is another quote from the NASA webpage: "The boundary between solar wind and interstellar wind is the heliopause, where the pressure of the two winds are in balance. Once Voyager passes the heliopause, it will be in interstellar space ". Several other locations in the NASA web make similar claims, as do numerous news organizations and Astronomy websites

According to NASA, the Heliopause is approximately 9 - 10 billion miles from the sun. Thus, at Voyager's current speed of about 3.5 au/yr, it will pass that outer boundary in the next 10 years.

I guess that is newsworthy. In fact, however, if the edge of the solar system is defined as "the outer reaches of the sun's influence", then the outer limits of the Oort Cloud of comets would mark the true outer boundary of our Solar Ssytem. All of the Oort cloud comets orbit the sun and are, therefore, within its gravitational influence.

According to numerous sources, that outer boundary is estimated to be from 1 LY to 100,000 au (1.5 LY) from the sun. That is almost 9 trillion miles. At the speed of Voyager, it will take over 25,000 YEARS for Voyager to fly past that last Oort comet orbit and officially leave our solar system.

Why is the Oort cloud and this fact continually ignored by the media and by NASA when discussing Voyager reaching the edge of the solar system? While I could consider it simply as media hype, so many organizations (including NASA and JPL) are referencing it that there must be something I'm missing.


Thanks,

Frank

As I understand it, the Oort cloud isn't proven to exist yet, but rather a hypothetical cloud of comets that can support the reason for the existence of Sedna-like objects.

Hungry4Info:

That's a good point.

While the entire Oort cloud has not been directly observed, it is my understanding that comets that are theorized to come from it have been seen. Since it is assumed to exist and is referenced as such numerous times on both the NASA site and ESA sites, and is a common component of our Solar system in probably all Astronomy texts, I would think that its existance would not be ignored when discussing the outer boundary of the solar system ... certainly not by NASA or the general media.

Frank

Perhaps a more interesting definition of the limits of the solar system may come from working out the relative influences of the solar and galactic gravitational fields.

I thought the heliopause was considered the edge of the solar system.