Nicesociety at 01:01, 8 January 2009

2009-01-08T01:01:56Z

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<h2 align=center>Spectral (Stellar) Classification System</h2>
The original version of the current MK system
was defined by Morgan, Keenan, and Kellman (1943), and a revised
list of standards was published in 1953 by Morgan and Johnson.
Additional refinements have been added since then.
MK Spectral Classification System (Standard)


<CENTER>
<TABLE borderColor=#008080 cellSpacing=4 cellPadding=1 width=578 border=1>
<TR>
<TD vAlign=center width="12%"> <h5 align=center>Class**
</h5></TD>
<TD vAlign=center width="33%"> <h5 align=center>Color
</h5></TD>
<TD vAlign=center width="23%"> <h5 align=center>Temperature
(K)</h5></TD>
<TD vAlign=center width="53%"> <h5 align=center>Composition
</h5></TD>
</TR>
<TR>
<TD vAlign=center width="12%"> O</TD>
<TD vAlign=center width="13%"> Dark Blue</TD>
<TD vAlign=center width="23%"> 28,000-50,000</TD>

<TD vAlign=center width="53%"> ionized atoms,
especially helium</TD>
</TR>
<TR>
<TD vAlign=center width="12%"> B</TD>
<TD vAlign=center width="13%"> Blue</TD>
<TD vAlign=center width="23%"> 10,000-28,000</TD>

<TD vAlign=center width="53%"> neutral helium,
some hydrogen</TD>
</TR>
<TR>
<TD vAlign=center width="12%"> A</TD>
<TD vAlign=center width="13%"> Light Blue</TD>
<TD vAlign=center width="23%"> 7,500-10,000</TD>

<TD vAlign=center width="53%"> strong hydrogen,
some ionized metals</TD>
</TR>
<TR>
<TD vAlign=center width="12%"> F</TD>
<TD vAlign=center width="13%"> White</TD>
<TD vAlign=center width="23%"> 6,000-7,500</TD>

<TD vAlign=center width="53%"> hydrogen
and ionized metals; calcium and iron</TD>
</TR>
<TR>
<TD vAlign=center width="12%"> G</TD>
<TD vAlign=center width="13%"> Yellow</TD>
<TD vAlign=center width="23%"> 5,000-6,000</TD>

<TD vAlign=center width="53%"> ionized calcium;
both neutral and ionized metals</TD>
</TR>
<TR>
<TD vAlign=center width="12%"> K</TD>
<TD vAlign=center width="13%"> Orange</TD>
<TD vAlign=center width="23%"> 3,500-5,000</TD>

<TD vAlign=center width="53%"> Neutral metals</TD>
</TR>
<TR>
<TD vAlign=center width="12%"> M</TD>
<TD vAlign=center width="13%"> Red</TD>
<TD vAlign=center width="23%"> 2,500-3,500</TD>

<TD vAlign=center width="53%"> Strong molecules;
titanium oxide, neutral calcium</TD>
</TR>
</TABLE>

<BLOCKQUOTE ALIGN="CENTER">**Three additional categories are also
in the scheme: R, N, and S types, which were later realized to
represent stars with peculiar heavy-metal abundances. Other types
(Q for novae, W for Wolf-Rayet stars, T for T Tauri stars, etc...)
are encountered infrequently. Thus, the above listing is considered
the standard classification scheme, and R, N, S, T, Q, W, etc...
are addendums in the rare cases they are observed.**</BLOCKQUOTE>

<BLOCKQUOTE ALIGN="CENTER">Each class is subdivided into 10 categories by decreasing
temperature within each class. This scale ranges from 0 (the hottest)
to 9 (the coolest), i.e., A0, A1, A2, ... A8, A9. So, an A4 star
is hotter then an A7. For instance, Vega is an A0 and the Sun
is a G2.
<BLOCKQUOTE ALIGN="CENTER">Stars are then further classified
by their type into six luminosity categories by the Yerkes scheme,
as seen in the Hertzsprung-Russell Diagram below (based on Luminosity
and Temperature (K))::

:Ia: Most Luminous Supergiants
:Ib: Less Luminous Supergiants
:II: Luminous Giants
:III: Normal Giants
:IV: Sub-Giants
:V: Main Sequence (Dwarfs)
<BLOCKQUOTE ALIGN="CENTER">''Thus, Sol, is categorized a G2V classification. That is, a G-Type 2
Main Sequence star.''</BLOCKQUOTE>

[[Category: Science]][[Category: Database]]

Spectral (Stellar) Classification System - Revision history

Nicesociety at 01:01, 8 January 2009