What planet can not be seen from Earth?

Answer 1

The planet Neptune, due to its great distance from Earth, cannot be seen without aid such as a pair of binoculars or a telescope. Uranus, though very dim, can sometimes be made out with the naked eye. All of the other planets are visible with the naked eye.

Answer 2

Short answer: Both Neptune & Mercury.

97% of the time, Mercury is seen only during twilight hours, hence a small amount of daylight is in the sky. Neptune is only visible with a telescope and cannot be seen with the naked eye - regardless of how much twilight is in the sky.

Long answer:

First, some assumptions:

1. A "dark sky" refers to a clear nighttime sky, with no Moon visible, in at least one location on Earth with a clear view of the horizon and minimal air pollution, between the end of Astronomical Twilight in the Evening and the beginning of Astronomical Twilight in the morning. (Astronomical twilight times are available at the 'sunrisesunset' link given.)

2. "Seen" means can be seen with the naked eye, since obviously all of the planets can be seen with a telescope. Furthermore, "seen" includes instances of "just barely visible", including cases where the object may be just above the horizon. In other words, to be "seen" does not necessarily mean "easily seen".

3. Earth itself will be assumed to be visible in this sense since under the above conditions there will be enough light from the stars to see the Earth beneath your feet.

4. It is recognized that, of course, any planet otherwise visible is sometimes not visible because it is currently below the horizon in its orbit.

Given these assumptions, the planets Venus, Mars, Jupiter, and Saturn are unquestionably visible.

The planet Mercury comes very close to not being visible under condition 1, however at maximum elongation (for example on or about April 25th, 2009) it sets just after the end of evening Astronomical twilight, so it is visible in a "dark sky" just above the horizon before it sets. Of course, relaxing the twilight requirement, Mercury is readily visible in a night sky considerable above the horizon as long as you know when and where to look. That is, it is, in fact, easy to see Mercury in a reasonably dark sky. (Reference: Sky & Telescope's Skygazer's Almanac for 2009.)

Uranus, while difficult to find, is technically visible to the naked eye. For example, referring to Wikipedia, at its brightest, Uranus has a magnitude of +5.9 while the limit of naked eye visibility is +6.5 (note that higher magnitudes represent dimmer objects).

Finally (discounting Pluto, now a dwarf planet, and definitely never visible to the naked eye in any case), Neptune is, according to Wikipedia: "... never visible to the naked eye, having a brightness between magnitudes +7.7 and +8.0".

So the only definitive answer is Neptune, although Mercury barely qualifies as visible in a "dark sky".

(Astronomical twilight web site: http://www.sunrisesunset.com/calendar.asp )

Answer 3

Basically, with a good telescope or even binoculars, on a good night and without any significant light pollution, all planet are visible.

With the exception of Neptune, all of the other seven planets are visible with the naked eye, although Uranus has to have "perfect" conditions.

Answer 4

Neptune, the furthest planet from the sun. It has a maximum apparent magnitude (maximum brightness to us) of 7.78, where the visible limit is around 6. The lower the number the brighter the object.

Its possible to just see Uranus when at maximum brightness and under perfect conditions, it has a maximum apparent magnitude of 5.32.

Answer 5

Uranus is the only planet in our solar system that cannot be seen from Earth without the help of a telescope. It is located at a distance of about 1.8 billion miles from Earth and appears as a tiny, faint dot in the night sky.

Answer 6

earth