Search results
Results From The WOW.Com Content Network
For a stable orbit the ratio between the moon's orbital period P s around its primary star P p must be < 1 ⁄ 9, e.g. if a planet takes 90 days to orbit its star, the maximum stable orbit for a moon of that planet is less than 10 days.
If a day takes years, the temperature differential between the day and night side will be pronounced, and problems similar to those noted with extreme orbital eccentricity will come to the fore. The planet also should rotate quickly enough so that a magnetic dynamo may be started in its iron core to produce a magnetic field.
Humans have achieved some mediated presence throughout the Solar System, but the most extensive presence has been in orbit around Earth. Humans reached outer space mediated in 1944 and have sustained mediated presence since 1958 , [a] as well as having reached space directly for the first time on 12 April 1961 (Yuri Gagarin) and continuously ...
In recent years, there has been an increase in research on the issue of how humans can survive and work in space for extended and possibly indefinite periods of time. This question requires input from the physical and biological sciences and has now become the greatest challenge (other than funding) facing human space exploration. A fundamental ...
Planetary habitability in the Solar System is the study that searches the possible existence of past or present extraterrestrial life in those celestial bodies. As exoplanets are too far away and can only be studied by indirect means, the celestial bodies in the Solar System allow for a much more detailed study: direct telescope observation, space probes, rovers and even human spaceflight.
Surface planetary habitability is thought to require an orbit at the right distance from the host star for liquid surface water to be present, in addition to various geophysical and geodynamical aspects, atmospheric density, radiation type and intensity, and the host star's plasma environment. [2]
For instance, a small body in circular orbit 10.5 cm above the surface of a sphere of tungsten half a metre in radius would travel at slightly more than 1 mm/s, completing an orbit every hour. If the same sphere were made of lead the small body would need to orbit just 6.7 mm above the surface for sustaining the same orbital period.
It is the lunar equivalent of the division between night and day on the Earth spheroid, although the Moon's much lower rate of rotation [7] means it takes longer for it to pass across the surface. At the equator, it moves at 15.4 kilometres per hour (9.6 mph), as fast as an athletic human can run on earth.