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© by Zane B. Stein

CENTAUR BINARIES

On January 20, 2006, the Hubble Space Telescope was aimed at the Centaur #42355 (2002 CR46), and were stunned to find out that it was actually a binary. That is, a two-body system, with one part orbiting the other at a distance of 1,300 kilometers (800 miles). (CR46 was originally discovered February 5, 2002, so it took astronomers almost four years to discover it had a moon.)

While other binary minor planets have been found, CR46 was the first known binary Centaur. This led astronomers into all sorts of speculations, including the possibility that there may be binary comets orbiting our Sun.

It's eccentricity is 0.5407609, and an orbital period of 235.76 years. (Typhon and Echidna's orbital elements.) First thing I thought when I read that was that the orbit was huge compared to the other Centaurs. We'll go back to that in a moment.

Only a few months later, on April 11, 2006, a second binary Centaur was observed, #65489 (2003 FX128). (FX128 had been originally discovered March 22, 2003.)(

But this body had an even stranger orbit for a Centaur than CR46. The eccentricity was 0.8258985, and the orbital period of 1,039.67 years! (Ceto and Phorcys' orbital elements.) When astronomers realized this, they did some thinking, and reclassified both of these bodies. They are now no longer called Centaurs. Rather, they are SDO's, or Scattered Disk Objects. (I'm actually relieved, considering the names they later were given!)

#42355 was named Typhon on November 9, 2006. Typhon was god of wind, whose parents were Gaia and Tartarus. Typhon was oft descried as the largest, most grotesque of all creatures, often pictured as having a hundred serpent heads. He attempted to overthrow Zeus and take over, but Zeus defeated him by crushing Mount Etna on him.

Typhon's companion, or moon, was named Echidna. Hesiod wrote that Echidna was Typhon's mate, and together they gave birth to almost every horrible monster in Greek mythology.

#65489 was named Ceto on the same date, November 9, 2006, after a terrible sea monster, daughter of Gaia and Pontus, who personified all the known an unknown dangers and terrible creatures in the sea. Ceto, in fact, became short for sea monster, and the word Cetacean was derived from her name.

Ceto's moon was named Phorcys, after her husband in mythology, they also gave birth to many terrible children, including the Gorgons such as Medusa.

Now do you see why I'm glad they weren't kept as Centaurs?

For those interested, here is a 2008-2012 ephemeris, for every fifteen days, for Typhon and Ceto. It is set to 0 Hr UT:

DATE TYPHON
Longitude
TYPHON
Latitude
. . CETO
Longitude
CETO
Latitude
Jan 1 2008 13°Vi52' R +00°29' 03°Sc50' +14°33'
Jan 16 2008 13°Vi38' +00°29' 04°Sc05' +14°42'
Jan 31 2008 13°Vi13' +00°28' 04°Sc11' +14°52'
Feb 15 2008 12°Vi40' +00°28' 04°Sc10' R +15°01'
Mar 1 2008 12°Vi03' +00°27' 04°Sc01' +15°10'
Mar 16 2008 11°Vi25' +00°26' 03°Sc44' +15°17'
Mar 31 2008 10°Vi52' +00°26' 03°Sc23' +15°23'
Apr 15 2008 10°Vi25' +00°25' 02°Sc58' +15°27'
Apr 30 2008 10°Vi08' +00°24' 02°Sc32' +15°29'
May 15 2008 10°Vi03' D +00°23' 02°Sc07' +15°29'
May 30 2008 10°Vi10' +00°22' 01°Sc46' +15°26'
Jun 14 2008 10°Vi29' +00°21' 01°Sc29' +15°23'
Jun 29 2008 11°Vi00' +00°20' 01°Sc19' +15°18'
Jul 14 2008 11°Vi40' +00°19' 01°Sc16' D +15°12'
Jul 29 2008 12°Vi29' +00°19' 01°Sc21' +15°06'
Aug 13 2008 13°Vi24' +00°18' 01°Sc33' +15°00'
Aug 28 2008 14°Vi24' +00°17' 01°Sc52' +14°55'
Sep 12 2008 15°Vi24' +00°17' 02°Sc18' +14°51'
Sep 27 2008 16°Vi24' +00°16' 02°Sc47' +14°49'
Oct 12 2008 17°Vi21' +00°16' 03°Sc21' +14°48'
Oct 27 2008 18°Vi12' +00°15' 03°Sc56' +14°48'
Nov 11 2008 18°Vi55' +00°15' 04°Sc31' +14°51'
Nov 26 2008 19°Vi28' +00°14' 05°Sc04' +14°55'
Dec 11 2008 19°Vi49' +00°14' 05°Sc33' +15°01'
Dec 26 2008 19°Vi57' +00°13' 05°Sc57' +15°09'
Jan 10 2009 19°Vi53' R +00°13' 06°Sc15' +15°17'
Jan 25 2009 19°Vi36' +00°13' 06°Sc26' +15°27'
Feb 9 2009 19°Vi09' +00°12' 06°Sc28' R +15°36'
Feb 24 2009 18°Vi35' +00°11' 06°Sc22' +15°45'
Mar 11 2009 17°Vi57' +00°11' 06°Sc10' +15°53'
Mar 26 2009 17°Vi21' +00°10' 05°Sc51' +16°00'
Apr 10 2009 16°Vi49' +00°09' 05°Sc28' +16°05'
Apr 25 2009 16°Vi24' +00°09' 05°Sc03' +16°08'
May 10 2009 16°Vi10' +00°08' 04°Sc38' +16°08'
May 25 2009 16°Vi08' D +00°07' 04°Sc15' +16°07'
Jun 9 2009 16°Vi17' +00°06' 03°Sc56' +16°03'
Jun 24 2009 16°Vi39' +00°06' 03°Sc43' +15°59'
Jul 9 2009 17°Vi12' +00°05' 03°Sc36' +15°53'
Jul 24 2009 17°Vi54' +00°04' 03°Sc37' D +15°47'
Aug 8 2009 18°Vi44' +00°04' 03°Sc45' +15°41'
Aug 23 2009 19°Vi39' +00°03' 04°Sc00' +15°35'
Sep 7 2009 20°Vi38' +00°03' 04°Sc22' +15°30'
Sep 22 2009 21°Vi39' +00°02' 04°Sc48' +15°27'
Oct 7 2009 22°Vi37' +00°02' 05°Sc19' +15°25'
Oct 22 2009 23°Vi32' +00°01' 05°Sc53' +15°25'
Nov 6 2009 24°Vi21' +00°00' 06°Sc27' +15°26'
Nov 21 2009 25°Vi01' -00°00' 07°Sc00' +15°30'
Dec 6 2009 25°Vi30' -00°01' 07°Sc30' +15°35'
Dec 21 2009 25°Vi48' -00°01' 07°Sc57' +15°41'
Jan 5 2010 25°Vi52' R -00°02' 08°Sc17' +15°49'
Jan 20 2010 25°Vi44' -00°03' 08°Sc31' +15°58'
Feb 4 2010 25°Vi25' -00°03' 08°Sc37' +16°08'
Feb 19 2010 24°Vi56' -00°04' 08°Sc35' R +16°17'
Mar 6 2010 24°Vi21' -00°05' 08°Sc26' +16°25'
Mar 21 2010 23°Vi44' -00°05' 08°Sc10' +16°33'
Apr 5 2010 23°Vi08' -00°06' 07°Sc49' +16°38'
Apr 20 2010 22°Vi38' -00°07' 07°Sc26' +16°42'
May 5 2010 22°Vi16' -00°07' 07°Sc01' +16°44'
May 20 2010 22°Vi05' -00°08' 06°Sc37' +16°43'
Jun 4 2010 22°Vi05' D -00°08' 06°Sc17' +16°41'
Jun 19 2010 22°Vi18' -00°09' 06°Sc01' +16°36'
Jul 4 2010 22°Vi41' -00°09' 05°Sc51' +16°31'
Jul 19 2010 23°Vi16' -00°10' 05°Sc48' D +16°25'
Aug 3 2010 24°Vi00' -00°10' 05°Sc52' +16°18'
Aug 18 2010 24°Vi50' -00°11' 06°Sc03' +16°12'
Sep 2 2010 25°Vi46' -00°11' 06°Sc21' +16°07'
Sep 17 2010 26°Vi45' -00°12' 06°Sc44' +16°02'
Oct 2 2010 27°Vi44' -00°12' 07°Sc12' +16°00'
Oct 17 2010 28°Vi41' -00°13' 07°Sc44' +15°58'
Nov 1 2010 29°Vi33' -00°13' 08°Sc17' +15°59'
Nov 16 2010 00°Li19' -00°14' 08°Sc50' +16°01'
Dec 1 2010 00°Li56' -00°15' 09°Sc21' +16°05'
Dec 16 2010 01°Li22' -00°16' 09°Sc48' +16°11'
Dec 31 2010 01°Li35' -00°16' 10°Sc11' +16°18'
Jan 15 2011 01°Li36' R -00°17' 10°Sc28' +16°27'
Jan 30 2011 01°Li25' -00°18' 10°Sc37' +16°36'
Feb 14 2011 01°Li03' -00°19' 10°Sc39' R +16°45'
Mar 1 2011 00°Li32' -00°20' 10°Sc33' +16°54'
Mar 16 2011 29°Vi57' -00°20' 10°Sc21' +17°02'
Mar 31 2011 29°Vi20' -00°21' 10°Sc03' +17°08'
Apr 15 2011 28°Vi46' -00°21' 09°Sc41' +17°13'
Apr 30 2011 28°Vi18' -00°22' 09°Sc17' +17°15'
May 15 2011 27°Vi59' -00°22' 08°Sc53' +17°16'
May 30 2011 27°Vi50' -00°23' 08°Sc31' +17°14'
Jun 14 2011 27°Vi53' D -00°23' 08°Sc13' +17°10'
Jun 29 2011 28°Vi08' -00°23' 08°Sc00' +17°05'
Jul 14 2011 28°Vi34' -00°23' 07°Sc53' +16°59'
Jul 29 2011 29°Vi11' -00°24' 07°Sc54' D +16°53'
Aug 13 2011 29°Vi55' -00°24' 08°Sc01' +16°46'
Aug 28 2011 00°Li46' -00°24' 08°Sc15' +16°41'
Sep 12 2011 01°Li42' -00°25' 08°Sc35' +16°35'
Sep 27 2011 02°Li40' -00°25' 09°Sc01' +16°32'
Oct 12 2011 03°Li38' -00°26' 09°Sc30' +16°29'
Oct 27 2011 04°Li33' -00°26' 10°Sc01' +16°29'
Nov 11 2011 05°Li23' -00°27' 10°Sc34' +16°30'
Nov 26 2011 06°Li05' -00°28' 11°Sc05' +16°33'
Dec 11 2011 06°Li38' -00°29' 11°Sc34' +16°38'
Dec 26 2011 07°Li00' -00°30' 11°Sc58' +16°45'
Jan 10 2012 07°Li10' -00°31' 12°Sc17' +16°53'
Jan 25 2012 07°Li07' R -00°32' 12°Sc30' +17°02'
Feb 9 2012 06°Li52' -00°33' 12°Sc35' +17°11'
Feb 24 2012 06°Li28' -00°34' 12°Sc33' R +17°20'
Mar 10 2012 05°Li56' -00°34' 12°Sc23' +17°28'
Mar 25 2012 05°Li20' -00°35' 12°Sc08' +17°35'
Apr 9 2012 04°Li44' -00°36' 11°Sc48' +17°40'
Apr 24 2012 04°Li12' -00°36' 11°Sc25' +17°44'
May 9 2012 03°Li47' -00°36' 11°Sc02' +17°45'
May 24 2012 03°Li30' -00°36' 10°Sc39' +17°44'
Jun 8 2012 03°Li25' D -00°37' 10°Sc19' +17°41'
Jun 23 2012 03°Li31' -00°37' 10°Sc04' +17°37'
Jul 8 2012 03°Li48' -00°37' 09°Sc54' +17°31'
Jul 23 2012 04°Li16' -00°37' 09°Sc51' D +17°25'
Aug 7 2012 04°Li54' -00°37' 09°Sc55' +17°18'
Aug 22 2012 05°Li40' -00°37' 10°Sc06' +17°12'
Sep 6 2012 06°Li31' -00°37' 10°Sc23' +17°06'
Sep 21 2012 07°Li26' -00°38' 10°Sc45' +17°02'
Oct 6 2012 08°Li23' -00°38' 11°Sc12' +16°58'
Oct 21 2012 09°Li19' -00°39' 11°Sc41' +16°57'
Nov 5 2012 10°Li12' -00°40' 12°Sc12' +16°57'
Nov 20 2012 10°Li59' -00°40' 12°Sc44' +16°59'
Dec 5 2012 11°Li37' -00°41' 13°Sc13' +17°04'
Dec 20 2012 12°Li07' -00°42' 13°Sc39' +17°09'

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