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Separation, PositionAngle, ElongationSiderealTime, HourAngle, Culmination, ModifiedJulianDay, LocalDate

8.2 The FindNearestObject Function

FindNearestObject is useful for identifying the name of a star or other object that is near to a known object.

Finding the brightest star near an object.

Use FindNearestObject, for example, to find the name of the star nearest to the Moon, at a given time, that is brighter than magnitude 3.5.

You can also identify a star name by first clicking inside any star chart graphic (it must be the last graphic you have computed) and then while holding the CommandKey key down, clicking again near a star. If you then use Copy followed by Paste into FindNearestObject, the function returns the name of the star nearest to where you clicked in the graphic. This method works with all functions that require an object. For example, you can also find the equator coordinates of the selection.

At the given time the Moon and the returned star are separated by about 6 degrees, determined precisely using Separation.

In[15]:=FindNearestObject[Moon, {1993,11,17,3,20,0},
MagnitudeRange -> 3.5,
Clusters -> False,
Nebulae -> False]

Out[15]=

This is a plot of Ursa Major centered on Mizar, which is also known as Zeta (zeta) Ursae Majoris. If you hold the CommandKey key down and click on the star just to the left of CurlyEpsilon (epsilon), you get the numbers {3.05, 1.55}.

In[16]:=RadialStarChart[Mizar,
Epilog -> StarNames[UrsaMajor]];

Input the numbers selected from the previous graphics to determine the name of the small star just to the left of CurlyEpsilon (epsilon) Ursae Majoris.

In[17]:=FindNearestObject[{3.05414, 1.55386},
MagnitudeRange -> 5.5]

Out[17]=

Similarly, you can find the equator coordinates of the point that was clicked.

In[18]:=EquatorCoordinates[{3.05414, 1.55386}]

Out[18]=

You can use FindNearestObject to determine the name of a partner in a double star system.

Beta (beta) Cygni is one of the most beautiful double stars. The main component is a third magnitude gold-colored (K3) star. In Scientific Astronomer notation the star is referred to as Beta.Cygnus.

In[19]:=Appearance[Beta.Cygnus]

Out[19]=

The other component is a star called Beta2.Cygnus.

In[20]:=FindNearestObject[Beta.Cygnus]

Out[20]=

Beta2 (beta2) Cygni is a fifth magnitude blue (B8) star, separated by 0.009 degrees from the main gold-colored star. The contrasting blue and gold colors give this pair a distinctive appearance in a telescope.

In[21]:=Separation[Beta2.Cygnus, Beta.Cygnus]

Out[21]=

Separation, PositionAngle, ElongationSiderealTime, HourAngle, Culmination, ModifiedJulianDay, LocalDate



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