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Hipparchus, Greek astronomer

(Encyclopedia)Hipparchus, fl. 2d cent. b.c., Greek astronomer, b. Nicaea, Bithynia. He is the first systematic astronomer of whom there are records. He made his observations chiefly on the island of Rhodes. Ptolemy...

Stonehenge

(Encyclopedia)Stonehenge stōnˈhĕnjˌ [key], group of standing stones on Salisbury Plain, Wiltshire, S England. Preeminent among megalithic monuments in the British Isles, it is similar to an older and larger mon...

corona, in astronomy

(Encyclopedia)corona, luminous envelope surrounding the sun, outside the chromosphere. Its density is less than one billionth that of the earth's atmosphere. The corona is visible only at the time of totality durin...

Newcomb, Simon

(Encyclopedia)Newcomb, Simon no͞oˈkəm, nyo͞oˈ– [key], 1835–1909, American astronomer, b. Nova Scotia, grad. Lawrence Scientific School, Harvard, 1858. Living in the United States from 1853, he was appointe...

saros

(Encyclopedia)saros: see eclipse.

Baily's beads

(Encyclopedia)Baily's beads: see eclipse.

umbra

(Encyclopedia)umbra: see eclipse; sunspots. ...

Hevelius, Johannes

(Encyclopedia)Hevelius, Johannes yōhänˈəs hāvāˈlēo͝os [key], 1611–87, Polish astronomer, b. Danzig. From a finely equipped observatory in his house at Danzig, assisted by his wife Elizabeth, he made valu...

penumbra

(Encyclopedia)penumbra pĭnŭmˈbrə [key]: see eclipse; sunspots. ...

tektite

(Encyclopedia)tektite tĕktīt [key], naturally occurring, silica-rich (65%–80% SiO2) glass resembling obsidian and sometimes shale, and is normally jet black to olive green. They appear as small rounded or elong...