Tarf — Star in Cancer
HIP 40526; Beta Cancri; 17 Cancri
About Tarf
Description
Tarf, Beta Cancri, is a K-type giant of spectral class K4 III with a weak s-process (barium) chemical anomaly, located 303 light-years away. It is the brightest star in the faint zodiac constellation Cancer, shining at magnitude 3.52. Tarf hosts a confirmed exoplanet, Beta Cancri b, a super-Jupiter in a 605-day orbit discovered in 2014.
Observing Tips
Tarf is the brightest star in Cancer — but that is no high bar, since Cancer's other stars are all fainter than magnitude 3.9. Tarf lies in the southwestern corner of the constellation, southeast of Castor and Pollux. Its warm orange-red color is obvious in binoculars. Best observed January through May.
History
The name Tarf comes from the Arabic "al-ṭaraf," meaning "the edge" or "end" — referring to the tip of one of the crab's legs. The IAU adopted the name in 2014. The exoplanet was announced the same year.
Fun Facts
Tarf's barium enrichment is the signature of past mass transfer from a companion that has since evolved into a white dwarf. Tarf b at 1.7 AU orbits beyond the zone that would have been engulfed during the star's giant-branch evolution, suggesting it formed at its current location or migrated outward during the giant phase.
Observe
1Physical Properties
2Position & Identifiers
3How easy to spot?
| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | Easy | Easy | Medium+ |
| 50 mm finder 50mm finder | Easy | Easy | Easy |
| 150 mm telescope 150mm scope | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Survey Image
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Explore
7
Size Comparison
8
Compare Stars
9
Spectral Classification
10
Hertzsprung-Russell Diagram
11
Stellar Lifecycle
12
Blackbody Spectrum
13
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
14
Stellar Fusion
15
Exoplanets
1 known planet
View in 3D
| Planet | Radius | Mass | Period | Distance |
|---|---|---|---|---|
| bet Cnc b | 12.60R⊕ | 7.80M♃ | 1.7yr | 290ly |
Habitable Zone
Size & Mass Comparison
About exoplanets — how we find them and which host stars you can observe
Discover
16Stellar Notes
17
Light Travel Time Machine
18
Relativistic Travel
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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