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Zeta (ζ) Cancri
Multipls Star System
| Right Ascension | 8h 12m 12.6s | Best Seen | 1/15 - 5/1 |
| Declination | 17° 38' 52" | Combined Magnitude | 4.67 |
| Apparent Separation | 9.00" | Constellation | Cancer |
Actual |
Compared to Sun |
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| Distance | 83 ly | -- |
| Separation | ~ 1.8 / 16.3 billion miles | ~ 19 / 175 au |
| Orbital Period | varies - see below | -- |
| Actual Brightness | -- | 2.8 / 1.9 / 1.7 |
| Magnitude | 5.68 / 6.09 / 6.22 | -- |
| Mass | varies - see below | -- |
| Surface Gravity | -- | -- |
| Surface Composition (by mass) | 74% hydrogen 24% helium 2% everything else |
same |
| Spectral Type | F8V / F9V / G5V | G2 V |
| Density (gram/cubic cm) | -- | -- |
What To Look For Through The Telescope
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Recommended eyepiece: 24mm or 40 mm.
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When people look through the telescope they should see two stars next to each other, with a third star close by. One star may be slightly dimmer than the others.
Zeta Cancri Information:
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The two stars next to each other can be called Star A and Star B.
a. Stars A and B are separated by 0.8 arcseconds.
b. A and B take about 60 years to orbit each other, and are about 19 AU’s apart.
c. Star A’s mass is 1.11 times that of our sun. Star B’s mass is the same as our sun.
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The third star can be called Star C.
a. AB and C take about 1100 years to orbit each other.
b. Star C’s mass is estimated to be about 0.99 times that of our sun.
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A fourth, unseen star orbits Star C. This unseen star can be called Star D.
a. Star D’s existence was suggested for years based on Star C’s motion. The Canada-France-Hawaii Telescope was the first to take a picture of D, with the help of adaptive optics. The European Southern Observatory’s observations confirmed its existence.
b. Stars C and D are separated by 0.3 arcseconds.
c. D orbits C in about 17 years.
d. Star D’s mass is about 0.93 times that of our sun.
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Interesting stuff
a. The Canada-France-Hawaii Telescope’s observations indicate that Star D may really be a multiple system consisting of two low mass, very red M dwarfs. The European Southern Observatory’s observation strengthen that argument.
b. The ESO may have even detected another star, called Star E, orbiting even closer to Star C than Star D.
c. For both of these possibilities, more time and data are needed to know for sure.
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References
| Item | Updated | Notes |
| Coordinates | 2002-11-13 | OK - Scott’s The Flamsteed Collection and SIMBAD |
| Combined Magnitude | 2002-11-13 | OK - Flamsteed |
| Apparent Separation | 2002-11-13 | OK - Flamsteed |
| Distance | 2002-11-13 | OK - in agreement with Flamsteed and SIMBAD |
| Separation | 2002-11-13 | OK – http://www.sciencenet.org.uk/astron/const/Cancer/zetacan.html |
| Orbital Period | 2002-11-22 | see other information |
| Actual Brightness | 2002-11-13 | OK – Flamsteed |
| Magnitude | 2002-11-13 | OK - Flamsteed |
| Mass | 2002-11-22 | see other information |
| Surface Gravity | -- | |
| Surface Composition | -- | OK for all stars |
| Spectral Type | 2002-11-18 | Flamsteed says star C is the F9 star, but SIMBAD and other web searches give info here |
| Density | -- | |
| Other Information | 2002-11-13 | info from http://www.eso.org/~arichich/publications/2000a_a...364..225.pdf and http://www.cfht.hawaii.edu/Science/Astros/Imageofweek/ciw010500.html and http://www.sciencenet.org.uk/astron/const/Cancer/zetacan.html |