1.   He argued that the habitable zones around stars were in fact quite narrow, with planets at their edges either boiling hot or freezing cold.

2.   In planning their search, scientists said they think they can rule out at least parts of the galaxy and focus on so-called habitable zones.

3.   Moreover, Gonzalez suggested, the habitable zone was unlikely to include the densely packed spiral arms of the galaxy.

4.   Scientists recently concluded from meteorite evidence that dry Mars, the only planet in the habitable zone between Earth and Jupiter, had water in its distant past.

5.   The two detected Jupiter-class objects are almost certainly huge gaseous bodies, presumably beyond the so-called habitable zone around a Sun-like star.