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Planets Discovered at the Detroit Observatory (1868) January 6, 2011

Posted by aquillam in Astronomy, Detroit Observatory, MichiganAstro.
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On Friday, August 21, 1868, the following item appeared in the Michigan Argus

About midnight of Saturday last, Prof. WATSON bagged another planet, which he describes as shining like a star of the tenth magnitude, and situated at twilight Sunday morning in right ascension 358 degrees and 25 minutes; declination 48 minutes south; with an apparent motion west and north 34 seconds of time in right ascension, an four minutes of arc in declination. Prof. W. is driving business in the planet line, having discovered one on the 11th of July.

Using a combination of Starry Night and an internet search (especially ADS), I believe this is the asteroid Helena.

In case you’re wondering, in 1868 anything that moved relative to the stars was generally considered a planet. Ceres, now known as a dwarf planet, was considered a full fledged planet when it was discovered on January 1, 1801. By the 1850s, about a dozen of these small objects were known, and astronomers began using the word “asteroid” to describe them, rather like some planetary scientists started calling Pluto a dwarf planet, ice dwarf, or “trans-Neptunian Object” back in the 1970s. It was another 20 or so years before asteroid became the common name for such objects.

There were several “planets” discovered at the Detroit Observatory during this period, despite the Michigan Weather.  Check out this report from the Lick Observatory in 1943: http://adsabs.harvard.edu/full/1943LicOB..19..161H.

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