The Astrogators' Guide to

Tau Ceti

Back to Contents

    Also called Durre Menthor or 52 Ceti, Tau Ceti offers us yet another way station for Humanity's initial exploration of our galaxy. As a Sun-like star, it may offer planets similar to those in our solar system.

Location in Space

Radial Distance:

    Parallax = 0.27418 0.0008 arc-seconds, which leads to

        1. 11.91 lightyears 0.03 lightyear (3.65 0.01 parsecs).

        2. 752,298 AU 2,195 AU.

Equatorial Coordinates:

    Right Ascension; 1 hr, 44 min, 4.0829 sec - 11.4796t sec.

    Declination; -15 deg, 56 arc-min, 14.928 arc-sec + 85.417t arc-sec.

        [t measured in centuries, Jan 2000 is t = 0]

    Imagine standing on the north side of a plane in which Earth's equator lies with the north celestial pole directly overhead and look toward the First Point of Aries (now in Pisces just southeast of the Circlet). Slide your gaze eastward (to your left) along the celestial equator by a little less than one minute more than 26 degrees, reaching a point on a nondescript part of the sky where Pisces segues into Aries. Then tilt your view south (down) by 3-3/4 arc-minutes less than 16 degrees to another point on a part of the celestial sphere with no prominent skymarks. Tau Ceti itself, as the name implies, appears only faintly.

Ecliptic Coordinates:

    Ecliptic Latitude; -24.8159 degrees + 143.33t arc-sec.

    Ecliptic Longitude; 17.8186 degrees +124.64t arc-sec.

        [elapsed time measured in centuries, Jan 2000 is t = 0]

    Look toward the First Point of Aries (the point on the sky that the sun occupies on the first day of spring), shift your gaze eastward along the Ecliptic (the line that the sun traces through the Zodiac in the course of a year) by almost 50 arc-minutes more than 17 degrees, reaching a point in the southern part of Pisces. Then tilt your view southward by about 11 arc-minutes less than 25 degrees along a line perpendicular to the Ecliptic. Tau Ceti appears as a third-magnitude star.

Galactic Coordinates:

    Galactic Latitude; -73.4397 degrees + 16.79t arc-sec.

    Galactic Longitude; 173.0975 degrees - 191.48t arc-sec.

        [elapsed time measured in centuries, Jan 2000 is t = 0]

    Look toward the radio source Sagittarius-A by casting your gaze across the Orion-Sagittarius Gap toward the Sagittarius-Carina Arm of the galaxy and at a point about six degrees south of the Ecliptic on the west (right) side of Sagittarius and two degrees south of X Sagittarii (the point of the arrow in the Archer's bow). Then move your gaze in an easterly direction along the plane of the Milky Way by a little over 173 degrees to a point in Cygnus. Then tilt your gaze by a little less than 73-1/2 degrees in southerly direction, more or less downward and to your left, at right angles to the plane of the Milky Way.

Annual Proper Motion

    in Right Ascension = -1.72194 arc-sec/yr (6.2879 AU/yr = 29.8075 km/sec).

    in Declination = +0.85417 arc-sec/yr (3.12 AU per yr = 14.786 km/sec).

        Total Proper Motion = 1.922 arc-sec/yr (7.019 AU/yr = 33.2732 km/sec) in a direction 296.42 degrees counterclockwise from due celestial north, 319.58 degrees counterclockwise from due Ecliptic north, and 275.01 degrees counterclockwise from due galactic north.

    in Radial Distance = -16.4 km/sec (-3.4596 AU/yr).

        Total motion = 7.825 AU/yr = 37.095 km/sec.


From the present; moving toward Sol at 3.46 AU per year and across the sky at 7.012 AU per year, in 42,595 years Tau Ceti will reach its perihelion 10.68 lightyears (675,500 AU) from Sol on the northwest border of the constellation of Cetus, just going into Aquarius, after crossing 26.27 degrees of sky.

Orientation in Space

    We generally only get this information for binary stars. Tau Ceti has no detectable companion, so we have no data that would describe an orbital plane around the star. Thus we dismiss this section as irrelevant.

The Star Itself

    Diameter; 1,135,790 km 18,095 km (0.816 0.013 Sol)

    Harvard Class; G8 V (5344 K)

    Age; 10 billion years

    Mass; 0.77 Sol

    Brightness; 0.52 0.03 Sol

    Habitable zone: 0.72 AU (0.696 yr)

    Surface composition: hydrogen 74.6%, helium 24.65%, other 0.60% (Sol = hydrogen 73.7%, helium 24.5%, other 1.81%).

Planetary system properties:

    Infrared study of Tau Ceti indicates that the Tau Ceti system contains ten times as much dust as does our solar system. With heavy elements about one-third as abundant as they are in our sun, Tau Ceti would likely have rocky planets much smaller than the ones we have. But the amount of dust in the system implies the possibility of larger planets as well. Only further study will tell whether the planets of Tau Ceti fall in the larger than ours range or the smaller than ours range.

    The debris disk ranges from 35 AU to 50 AU from Tau Ceti, making it analogous to the Kuiper Belt, which lies outside the orbit of Neptune. With ten times the amount of dust orbiting Sol, the Tau Ceti dust disk likely sends comets and other bodies into the inner reaches of the Tau Ceti system at a rate ten times that of our solar system. The consequent bombardment of an hypothetical Earth-like planet would yield extinction-level events on a scale of millions of years instead of the tens of millions of years that elapse between such events on Earth. Though such a bombardment would slow down the evolution of complex ecosystems and organisms, it would not prevent life from coming into existence and evolving.

    In any case, the existence of the debris disk provides future expeditions the material necessary to build a new civilization, even if the planets don't provide a suitable foundation for it. We can thus mark Tau Ceti as a good candidate for a target of interstellar exploration.


Back to Contents