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Hans
2018-Jul-26, 08:12 PM
If the basis of the book 'When worlds collide' were to happen today how far out would we detect Bellus and Zyra coming?

In the novel, the object that destroys the Earth is another planet. The change to a star makes the film's title inaccurate.

In both cases how far out could we detect a 'rogue star' and a large planet and accompanying earth size planet?

schlaugh
2018-Jul-26, 09:03 PM
IIRC the film changed the plot so that a rogue star impacts the Earth and the accompanying planet ends up in orbit. The book dealt with two rogue planets, Bronson Alpha and Bronson Beta.

I think Bronson Alpha (the Earth killer) was larger than Beta so it may have become visible somewhere around the orbit of Neptune or maybe Uranus. Depends of course on its actual size and I can’t recall what the book said.

As for a rogue star, even a red dwarf, I would think it would become visible within *1000 AU, or even further out.

ETA: I also don’t recall what the movie said about Bellus and where it fell on the HR spectrum. M class? G class? Radius? Etc.

*ETA2: 1000 AU? Brain cramp! Maybe 10,000 AU. If Bellus had any kind of luminosity it should have been visible at 1 LY, minimum. Unless the discovering astronomers were using binoculars. If Proxima Centauri were moving towards the sun then the motion would be measurable.

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George
2018-Jul-26, 11:09 PM
If the basis of the book 'When worlds collide' were to happen today how far out would we detect Bellus and Zyra coming?The HST could detect large Jupiter to about 10,000 AU. IR scopes can detect fainter objects farther especially if these are warm objects Perhaps the guess of 10,000 AU for an Earth-sized planet is pretty close.

Hans
2018-Jul-27, 06:39 AM
Thanks George & Schlaugh

Yeah if the movie version is followed then the star would have been seen for generations the planet on the hand could 'sneak up' in the manner suggested.

Shaula
2018-Jul-27, 10:00 AM
The HST could detect large Jupiter to about 10,000 AU. IR scopes can detect fainter objects farther especially if these are warm objects Perhaps the guess of 10,000 AU for an Earth-sized planet is pretty close.
Although there is a caveat about search rate and coverage. HST can detect very dim targets - but the sensor that does that doesn't really do wide area searches. It would have to be cued in by another sensor, a survey system which generally has wider area coverage but lower sensitivity. You'd also have to be processing for anomalies or new sources.

George
2018-Jul-27, 01:22 PM
Although there is a caveat about search rate and coverage. HST can detect very dim targets - but the sensor that does that doesn't really do wide area searches. It would have to be cued in by another sensor, a survey system which generally has wider area coverage but lower sensitivity. You'd also have to be processing for anomalies or new sources. Yes, and I would assume a rogue would be more likely to be coming from the galactic plane where the background noise would make it even more difficult, such as in the search for Planet 9.