optical double


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Related to optical double: Binary star system

optical double:

see binary starbinary star
or binary system,
pair of stars that are held together by their mutual gravitational attraction and revolve about their common center of mass. In 1650 Riccioli made the first binary system discovery, that of the middle star in the Big Dipper's handle, Zeta
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.

optical double

1. See double star.
2. See double galaxy.
References in periodicals archive ?
I've also indicated whether the pair is known or suspected to be a true binary or an optical double; if I've listed an orbital period (P), it's a binary!
Astronomers call the true couples binary stars and the chance alignments optical doubles.
It's an easy, uneven optical double, with the primary about three times as bright as the companion.
Eta Draconis is one of the "backbone" stars of the dragon asterism, and a wide optical double. Its companion is a 5th-magnitude star, HD 148374, 662" away on a nearly direct line to the celestial pole.
6, 7 The M-type star 64 Draconis isn't a true double, but forms a wide optical double with 65 Draconis.
10 The cool, dim, yellow-white G9 giant sun 75 Draconis, in the northernmost reaches of the constellation, makes an easy optical double with its neighbor, HD 196565, a yellow-orange KO star.
"Double stars" include both binaries and optical doubles, pairs that merely look close together on the sky but whose stars are at different distances and physically unrelated.
Yet all of the included pictures show the potential for dozens of other optical doubles (especially the illustration for 16 and 17 Draconis).
"Matt Wedel replies: If there's a standard designation system for optical doubles, it's news to me.
Tau2 and Tau4 Serpentis are wide optical doubles that seem to mirror each other across an imaginary line extending southwest from Tau5 Serpentis.
Visual observers will still be needed, but for the highest scientific value they will need to perform specific observations--watching for an outburst of a rare class of star, making time-critical observations when robotic facilities might be clouded out, measuring the brightness of close optical doubles, and so on.