Comments on: “Assuming no non-gravitational forces…” https://www.habitablezone.com/2017/11/29/interstellar-visitor-update/ Fri, 03 Apr 2026 18:20:54 -0700 hourly 1 http://wordpress.org/?v=3.3.1 By: hank https://www.habitablezone.com/2017/11/29/interstellar-visitor-update/#comment-40587 hank Thu, 30 Nov 2017 14:41:56 +0000 https://habitablezone.com/?p=67952#comment-40587 Suppose Oumuamua had been bigger? Much bigger? Maybe even planet-sized? What if this is only a small representative of a class of numerous objects that could devastate planetary orbits and solar system stability, even without a direct collision? It could be argued that a Jupiter(or even Earth)-sized object suddenly flying through the inner solar system could wreak havoc or could gravitationally unleash a rain of planet-killing comets from the Oort Cloud. It has been suggested that these rogue planets, worlds not associated with any star, may be fairly common objects in the galaxy. Some clever gravitational lensing studies have put an upper limit to the possible number of these bodies, but they have not ruled out their existence altogether. A massive gas giant sized object would probably have been detected already, a long way off. These guys are big and highly reflective and the Sun would illuminate them brightly. But a rocky world about the size of the Earth or Mars could easily sneak in unobserved. Its surface would be dark, as is Oumuamua's, and it might not easily show up unless we knew exactly where to look. And it could be approaching from any direction. Most of our minor planet searches concentrate on the ecliptic. A planetary defense system would not help much. These proposals rely on long-term surveys of our own system to identify bodies that presented a potential danger to earth sometime in the future. We would be able to prioritize these hazards by their destructive capacity and the imminence of a collision. We would have plenty of time to devise some sort of defensive action to break up or divert the planet-killer, or at least, brace for impact. A useful side benefit of this sort of program is that it would provide an accurate chart of all the loose debris flying around the system, which would have great value for science or future space exploration. Even if we identified no real hazards, the program would pay for itself in other ways. On the other hand, an outside intruder the size of a planet would offer little time to prepare, and there would be little we could do to protect ourselves or mitigate the damage anyway. Phillip Wylie (<em>When Worlds Collide</em>) and Fritz Leiber (<em>The Wanderer</em>) have visited this scenario fictionally. No doubt there have been others. Suppose Oumuamua had been bigger? Much bigger? Maybe even planet-sized? What if this is only a small representative of a class of numerous objects that could devastate planetary orbits and solar system stability, even without a direct collision? It could be argued that a Jupiter(or even Earth)-sized object suddenly flying through the inner solar system could wreak havoc or could gravitationally unleash a rain of planet-killing comets from the Oort Cloud.

It has been suggested that these rogue planets, worlds not associated with any star, may be fairly common objects in the galaxy. Some clever gravitational lensing studies have put an upper limit to the possible number of these bodies, but they have not ruled out their existence altogether.

A massive gas giant sized object would probably have been detected already, a long way off. These guys are big and highly reflective and the Sun would illuminate them brightly. But a rocky world about the size of the Earth or Mars could easily sneak in unobserved. Its surface would be dark, as is Oumuamua’s, and it might not easily show up unless we knew exactly where to look. And it could be approaching from any direction. Most of our minor planet searches concentrate on the ecliptic.

A planetary defense system would not help much. These proposals rely on long-term surveys of our own system to identify bodies that presented a potential danger to earth sometime in the future. We would be able to prioritize these hazards by their destructive capacity and the imminence of a collision. We would have plenty of time to devise some sort of defensive action to break up or divert the planet-killer, or at least, brace for impact. A useful side benefit of this sort of program is that it would provide an accurate chart of all the loose debris flying around the system, which would have great value for science or future space exploration. Even if we identified no real hazards, the program would pay for itself in other ways.

On the other hand, an outside intruder the size of a planet would offer little time to prepare, and there would be little we could do to protect ourselves or mitigate the damage anyway.

Phillip Wylie (When Worlds Collide) and Fritz Leiber (The Wanderer) have visited this scenario fictionally. No doubt there have been others.

]]> By: RL https://www.habitablezone.com/2017/11/29/interstellar-visitor-update/#comment-40586 RL Thu, 30 Nov 2017 02:33:22 +0000 https://habitablezone.com/?p=67952#comment-40586 A sample from a sibling sun would be fascinating... just the elemental and isotopic composition would be valuable to know... A sample from a sibling sun would be fascinating… just the elemental and isotopic composition would be valuable to know…

]]> By: ER https://www.habitablezone.com/2017/11/29/interstellar-visitor-update/#comment-40585 ER Wed, 29 Nov 2017 17:17:50 +0000 https://habitablezone.com/?p=67952#comment-40585 please consider these earlier Hab Zone entries Proper Motion of the Fixed Stars. by ER April 19, 2014 9:12 am parsecs, parallax and proper motion by ER May 20, 2015 5:49 pm https://habitablezone.com/?prosc_taxopt=global%3A&s=proper+motion+of+the+fixed+stars Astronomical knowledge is mind-blowing and inspirational, but acquiring it is slow, plodding, meticulous drudgery. Its not what we know that matters, its how we know what we know. please consider these earlier Hab Zone entries

Proper Motion of the Fixed Stars. by ER April 19, 2014 9:12 am
parsecs, parallax and proper motion by ER May 20, 2015 5:49 pm

https://habitablezone.com/?prosc_taxopt=global%3A&s=proper+motion+of+the+fixed+stars

Astronomical knowledge is mind-blowing and inspirational, but acquiring it is slow, plodding, meticulous drudgery. Its not what we know that matters, its how we know what we know.

]]>