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<h2 align=center><b>Spectral (Stellar) Classification System</b></h2> | |||
<P><font size="2">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.</font></P> | |||
<P align=center><b>MK Spectral Classification System (Standard)</b></P> | |||
<P align=center> | <P align=center> | ||
<CENTER> | <CENTER> | ||
<TABLE borderColor=#008080 cellSpacing=4 cellPadding=1 | <TABLE borderColor=#008080 cellSpacing=4 cellPadding=1 width=578 border=1> | ||
width= | |||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <h5 | <TD vAlign=center width="12%"> <h5 align=center><b>Class** | ||
align=center><b> | |||
</b></h5></TD> | </b></h5></TD> | ||
<TD vAlign=center width=" | <TD vAlign=center width="33%"> <h5 align=center><b>Color | ||
align=center><b> | |||
</b></h5></TD> | </b></h5></TD> | ||
<TD vAlign=center width="23%"> <h5 align=center><b>Temperature | |||
(K)</b></h5></TD> | |||
<TD vAlign=center width="53%"> <h5 align=center><strong>Composition | |||
</strong></h5></TD> | |||
</TR> | </TR> | ||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <P | <TD vAlign=center width="12%"> <P align=center>O</P></TD> | ||
<TD vAlign=center width="13%"> <P align=center>Dark Blue</P></TD> | |||
align=center> | <TD vAlign=center width="23%"> <P align=center>28,000-50,000</P></TD> | ||
<TD vAlign=center width=" | |||
<TD vAlign=center width=" | |||
align=center> | <TD vAlign=center width="53%"> <P align=center>ionized atoms, | ||
especially helium</P></TD> | |||
</TR> | </TR> | ||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <P | <TD vAlign=center width="12%"> <P align=center>B</P></TD> | ||
<TD vAlign=center width="13%"> <P align=center>Blue</P></TD> | |||
<TD vAlign=center width="23%"> <P align=center>10,000-28,000</P></TD> | |||
<TD vAlign=center width="53%"> <P align=center>neutral helium, | |||
<TD vAlign=center width=" | some hydrogen</P></TD> | ||
</TR> | |||
align=center> | |||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <P | <TD vAlign=center width="12%"> <P align=center>A</P></TD> | ||
<TD vAlign=center width="13%"> <P align=center>Light Blue</P></TD> | |||
<TD vAlign=center width="23%"> <P align=center>7,500-10,000</P></TD> | |||
<TD vAlign=center width="53%"> <P align=center>strong hydrogen, | |||
<TD vAlign=center width=" | some ionized metals</P></TD> | ||
</TR> | |||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <P | <TD vAlign=center width="12%"> <P align=center>F</P></TD> | ||
<TD vAlign=center width="13%"> <P align=center>White</P></TD> | |||
<TD vAlign=center width="23%"> <P align=center>6,000-7,500</P></TD> | |||
<TD vAlign=center width="53%"> <P align=center>hydrogen | |||
<TD vAlign=center width=" | and ionized metals; calcium and iron</P></TD> | ||
</TR> | |||
align=center> | |||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <P | <TD vAlign=center width="12%"> <P align=center>G</P></TD> | ||
<TD vAlign=center width="13%"> <P align=center>Yellow</P></TD> | |||
<TD vAlign=center width="23%"> <P align=center>5,000-6,000</P></TD> | |||
<TD vAlign=center width="53%"> <P align=center>ionized calcium; | |||
<TD vAlign=center width=" | both neutral and ionized metals</P></TD> | ||
</TR> | |||
align=center> | |||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <P | <TD vAlign=center width="12%"> <P align=center>K</P></TD> | ||
<TD vAlign=center width="13%"> <P align=center>Orange</P></TD> | |||
<TD vAlign=center width="23%"> <P align=center>3,500-5,000</P></TD> | |||
<TD vAlign=center width="53%"> <P align=center>Neutral metals</P></TD> | |||
</TR> | |||
<TD vAlign=center width=" | |||
align=center> | |||
<TR> | <TR> | ||
<TD vAlign=center width="12%"> <P | <TD vAlign=center width="12%"> <P align=center>M</P></TD> | ||
<TD vAlign=center width="13%"> <P align=center>Red</P></TD> | |||
<TD vAlign=center width="23%"> <P align=center>2,500-3,500</P></TD> | |||
<TD vAlign=center width="53%"> <P align=center>Strong molecules; | |||
titanium oxide, neutral calcium</P></TD> | |||
</TR> | |||
<TD vAlign=center width=" | |||
align=center> | |||
</TABLE> | </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, <I>etc...</I>) | |||
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)):: | |||
<STRONG> | |||
:Ia: Most Luminous Supergiants | |||
:Ib: Less Luminous Supergiants | |||
:II: Luminous Giants | |||
:III: Normal Giants | |||
:IV: Sub-Giants | |||
:V: Main Sequence (Dwarfs)</STRONG> | |||
<BLOCKQUOTE ALIGN="CENTER">''Thus, Sol, is categorized a G2V classification. That is, a G-Type 2 | |||
Main Sequence star.''</BLOCKQUOTE> | |||
[[Category: Science]][[Category: Database]] | |||
[[Category: |