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MathGroup Archive 2007

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Re: Questions on AstronomicalData

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80680] Re: Questions on AstronomicalData
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Tue, 28 Aug 2007 06:43:06 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <fb0dmv$djv$1@smc.vnet.net>

Robert Pigeon wrote:

> Is there a problem with the AstronomicalData link with Wolfram database ?
> Try this:  AstronomicalData["AndromedaGalaxy","DistanceLightYears"] , as
> listed in the Help documentation.
> I get a dash for answer, but the Help documentation gives an answer before
> evaluating. When I try to get something from evaluating from the Help
> documentation I get the dash for answer.

On my system (Wintel XP SP2 Mathematica 6.0.1), I do not get a dash but 
the missing data symbol rather than the value 2.573*10^6, which seems to 
be correct (see http://en.wikipedia.org/wiki/Andromeda_Galaxy ).

In[1]:= AstronomicalData["AndromedaGalaxy", "DistanceLightYears"]

Out[1]= Missing["NotAvailable"]

> Also, I think that Pluto is not a planet anymore! But it is still listed as
> one. 

 From the online help:

   Possible classes for solar system objects include:

     "PlanetaryMoon"    natural planetary satellite
     "Planet"           solar system planet (including Pluto)

he last line indicates that WRI is aware of the demotion of Pluto as a 
planet by International Astronomical Union (IAU); but they have chosen 
to keep it listed as a planet (at least at the time of this writing), 
perhaps for practical reason.

Also, you may want to read the section "Possible Issues" (still on the 
online help).

Pluto is included in the list of Solar System planets :

In[2]:= AstronomicalData["Planet"]

Out[2]= {"Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", \
"Uranus", "Neptune", "Pluto"}

Though it is considered a "dwarf planet" :

In[3]:= AstronomicalData["Pluto", "ObjectType"]

Out[3]= "DwarfPlanet"

> So, where does the database come from? Same question for the other
> databases that we get data from! How can I be sure that the data is
> accurate!

Again, browsing the online help up to the section "Related Links", one 
can see _AstronomicalData Source Information_. Clicking on this link

http://reference.wolfram.com/mathematica/note/AstronomicalDataSourceInformation.html

brings you to a list of references that are used to build the database. 
(And even a pointer to contact the Wolfram Research AstronomicalData 
team if one wants to report an error or suggest an addition to the 
database.)

-- 
Jean-Marc



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