FYI…

 

As far as any kind of a response is concerned, I’ll keep everyone posted.

 

Tom

 

 

Re: The color of Antares and the Astronomy Picture of the Day (APOD) for today, 27 June 2009 and Monday, 15 June 2009

 

Robert and Jerry,

 

            For the 2nd time in as many weeks, the APOD website has made explicit reference to Antares as a “Yellow” star.  With respect, Antares is a red supergiant with an effective temperature of 3,500 K and peak emission in the near infrared (828 nm); that, combined with interstellar reddening towards the galactic center, an effect where scattering is a sharp function of the wavelength (yellow light would be scattered almost 4x more readily than red light), would conspire to render even its visual appearance as decidedly red.  Although there may be some consideration for an individual’s eye having a slightly different [spectral] response, a slightly different palette, if you will, to dispel any confusion, an explanation is warranted, either as an addendum or an errata.  Failing that, there is no subjective or astrophysical justification for this reference to Antares as being “Yellow” and, as such, it is decidedly incorrect.

 

In today’s APOD, reference is made to the APOD for 3 June 2008.  In that posting, Antares is again referred to as a “yellow” star; to wit: “Antares, the bright star that appears yellow just below the center".  Antares in that image appears decidedly orange-red, not yellow.  Our sun is a bright yellow star; Antares is a bright red star.

 

Regards,

Tom Madigan, FRAS, AAS

Associate Instructor of Astronomy and Physics, QCC, LIU

NASA/ JPL Solar System Ambassador