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Altarf (Beta Cancri, 17 Cancri) Star Facts

Altarf Facts

  • Altarf is a giant star that can be located in the constellation of Cancer. The description is based on the spectral class.
  • Altarf is a main star of the constellation outline.
  • Based on the spectral type (K4III) of the star, the star's colour is orange to red .
  • Altarf is the 1st brightest star in Cancer based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Altarf has at least 1 Extrasolar Planets believed to be in orbit around the star.
  • Altarf has a radius that is 61.00 times bigger than the Suns. Radius
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 303.41 light years away from us. Distance

Altarf's Alternative Names

Beta Cancri (Bet Cnc) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR3249. HIP40526 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD69267.

Altarf has alternative name(s) :- , Beta Cnc.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 17 Cancri. The Flamsteed name can be shortened to 17 Cnc.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+09 1917.

More details on objects' alternative names can be found at Star Names .

Location of Altarf

The location of the giant star in the night sky is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the object is compared to the celestial equator and is expressed in degrees. For Altarf, the location is 08h 16m 30.95 and +09° 11` 08.4 .

Radial Velocity and Proper Motion of Altarf

Proper Motion

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving -49.24 ± 0.10 milliarcseconds/year towards the north and -46.82 ± 0.19 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 22.94000 km/s with an error of about 0.19 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of Altarf

Altarf Temperature and Colour

Based on the star's spectral type of K4III , Altarf's colour and type is orange to red giant star. The star's effective temperature is 3,990 Kelvin which is cooler than our own Sun's effective Temperature which is 5,777 Kelvin

Altarf Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 785.70 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Altarf Radius

Altarf Radius has been calculated as being 61.00 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 42,443,800.00.km. If you need the diameter of the star, you just need to multiple the radius by 2.

Altarf Metalicity

The star's metallicity is -0.290000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

Altarf Apparent and Absolute Magnitudes

Altarf has an apparent magnitude of 3.53 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of -1.22 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.31. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Distance to Altarf

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 11.23000 which gave the calculated distance to Altarf as 290.44 light years away from Earth or 89.05 parsecs. If you want that in miles, it is about 1,707,387,953,387,447.69, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 10.75000 which put Altarf at a distance of 303.41 light years or 93.02 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

Using the 2007 distance, the star is roughly 19,186,618.58 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. The star's Galacto-Centric Distance is 7,471.00 Parsecs or 24,367.66 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to Altarf

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Walking450,867,947,851.22
Car1201,695,598,261.71
Airbus A380736276,456,238.32
Speed of Sound (Mach 1)767.269265,189,641.97
Concorde (Mach 2)1,534.54132,594,648.17
New Horizons Probe33,0006,165,811.86
Speed of Light670,616,629.00303.41

Meteor Showers Radiating from near Altarf

The Beta Cancrids Meteor Shower radiants from a point near this star. The meteor shower runs typically between with a peak date of 5th February. The speed of a meteor in the shower is 15 Km/s.

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

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Additional Altarf Facts and Figures

Visual Facts


Primary / Proper / Traditional NameAltarf
Alternative NamesBeta Cancri, Bet Cnc, HD 69267, HIP 40526, HR 3249, 17 Cancri, 17 Cnc, BD+09 1917, Beta Cnc
Spectral TypeK4III
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
ColourOrange to Red
GalaxyMilky Way
ConstellationCancer
Absolute Magnitude -1.22 / -1.31
Visual / Apparent Magnitude3.53
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)08h 16m 30.95
Declination (Dec.)+09° 11` 08.4
Galactic Latitude23.04773570 degrees
Galactic Longitude214.25310718 degrees
1997 Distance from Earth11.23000 Parallax (milliarcseconds)
 290.44 Light Years
 89.05 Parsecs
2007 Distance from Earth10.75000 Parallax (milliarcseconds)
 303.41 Light Years
 93.02 Parsecs
 19,186,618.58 Astronomical Units
Galacto-Centric Distance24,367.66 Light Years / 7,471.00 Parsecs
Proper Motion Dec.-49.24000 ± 0.10000 milliarcseconds/year
Proper Motion RA.-46.82000 ± 0.19000 milliarcseconds/year
B-V Index1.48
Radial Velocity22.94000 ± 0.19 km/s
Iron Abundance-0.1700 ± 9.99 Fe/H
Eccentricity0.10470
Semi-Major Axis6747.0000000
Stellar Luminosity (Lsun)785.7000000

Companions (Multi-Star and Exoplanets) Facts


Exoplanet Count1

Estimated Calculated Facts


Radius (x the Sun)61.00
Effective Temperature4,025 Kelvin

Sources and Links


SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
69267+09 1917.0A3.80000-45.00000-52.00000K2Orange
B14.30000-45.00000-52.000001889

Location of Altarf in Cancer


Altarf Location in Cancer

The map was generated using Night Vision, an awesome free application by Brian Simpson.


List of Extrasolar Planets orbiting Altarf


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
beta Cnc bConfirmed0.8605.2000.0820141.758.900

Cancer Main Stars

Altarf Solar System


This is a N.A.S.A. impression of what the solar system might look like. If the star is not on display, its because its so small compared to the orbits of the outer planets. The green area denotes the habital zone which if the planet is within that area, life could exist. The habital zone might not appear on the picture because its outside the area for the picture. Our planets show the orbit of the planet if its was in our solar system. For more information about the planet and other exoplanetary stuff, visit N.A.S.A.

Altarf Solar System

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