Zeta1,2 Reticuli

JPL, CalTech, NASA



Larger illustration



Astronomers have identified Zeta1
Reticuli as a prime target for the
Terrestrial Planet Finder (TPF),
now postponed indefinitely.

Zeta1 Reticuli became one of the top 100 target stars for NASA's Terrestrial Planet Finder (TPF), but this project was indefinitely postponed after NASA budget cutbacks.

From left: Betty Hill's post-hypnotic drawing, and Marjorie Fish's best-fit star map (larger image).
(Or "a view of the Solar System from slightly beyond Saturn towards the Sun," or hypnotic delusion?)

Based on the UFO conspiracy theorists on Earth believe that Zeta2, the brighter component, harbors the base of space-travelling beings (whom they call Greys"). Apparently, these Greys have been visiting Earth to abduct humans for research and other nefarious purposes. One of their vehicles purportedly crash landed in Roswell, New Mexico, which the U.S. Government is alleged to have been trying to cover up. (On April 1, 1997, PBS aired a NOVA television show called "Kidnapped by UFOs?" in the United States, which included the Hill incident -- see transcript.)

Star map (by unknown artist) with "trade routes" -- derived from drawings and best-fit stars by
Betty Hill, Marjorie Fish, and Jeffrey Kretsch -- can be compared with a ChView map centered on
Zeta2 that includes our Sun, Sol, and other bright stars now known to be located within 40 light-years.

Zeta1 Reticuli

This is a yellow-orange main sequence dwarf star of spectral and luminosity type G2.5-5 V, with about 93 to 104 percent of Sol's mass, around 87 to 91 percent of its diameter, and around 75 percent of its bolometric luminosity (NASA Star and Exoplanet Database; David F. Gray, 1992; and Kenneth R. Lang, 1980). The star may be 42 to 126 percent as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (NASA Star and Exoplanet Database; and del Peloso et al, 2000). Zeta1 has a brighter but distant stellar companion, Zeta2 Reticuli, currently located around 3,750 AUs away (based on an observed separation of 310" and HIPPARCOS distance estimates of 39.40 to 39.53 ly), with common proper motion and equal radial velocities (Da Silva and Foy, 1987). The evidence has grown against either star having a close stellar companion (Da Silva and Foy, 1987; and Bonneau et al, 1980, pp. 187-188). Useful catalogue numbers and designations for the star include: Zet1 Ret, HR 1006*, Gl 136, Hip 15330, HD 20766, CP(D)-63 217, SAO 248770, LHS 171, LTT 1573, LFT 275, and LPM 146.

Once thought to be old Population II, galactic-halo-type subdwarf stars, Zeta1 and its companion are more likely to be old disk stars (Da Silva and Foy, 1987), that may be as much as eight billion years old, but more recent analysis of chromospheric activity and rotation with spectral analysis and calibration with other Sol-type stars suggest that the two stars could be as young as 1.5 to three billion years old (Mamajek and Hillenbrand, 2008, Table 13). An earlier hypothesis that the stars were relatively dim because of a high abundance of helium (Da Silva and Foy, 1987) has been refuted recently (del Peloso et al, 2000). The pair is now thought to be part of the Zeta Herculis stellar moving (kinematic) group of high velocity stars as defined by Olin J. Eggen in 1958, which no longer includes Zeta Herculis itself (del Peloso et al, 2000).

Zeta2 Reticuli

A yellow-orange main sequence dwarf star of spectral and luminosity type G1-2 V, Zeta2 has around 99 to 111 percent of Sol's mass, 94 to 99 percent of its diameter, and 96 to 97 of its bolometric luminosity (Eiroa et al, 2010; and NASA Star and Exoplanet Database; David F. Gray, 1992; and Kenneth R. Lang, 1980). The star may be 38 to 126 percent as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (NASA Star and Exoplanet Database; and del Peloso et al, 2000). As mentioned above, Zeta2 is thought to be an old disk star, but more recent analysis of chromospheric activity and rotation with spectral analysis and calibration with other Sol-type stars suggest that the two stars could be as young as 1.5 to three billion years old (Eiroa et al, 2010; and Mamajek and Hillenbrand, 2008, Table 13). .

A close stellar companion around Zeta2 with a separation of 0.046" and a position angle of 11° (1978.86) was once suspected from observations in 1978. However, the object was unresolved when observed 334 days later in 1979 and so it was assumed to be an artifact of the telescope's spider (Bonneau et al, 1980, page 187). Useful catalogue numbers and designations for the star include: Zet2 Ret, HR 1010*, Gl 138, Hip 15371, HD 20807, CP(D)-62 265, SAO 248774, LHS 172, LTT 1576, LFT 276, and LPM 148.

Dust Disk

Hunt for Substellar Companions

On September 20, 1996, astronomers at the European Southern Observatory announced that they had detected possible indications of a giant planet around Zeta2 with around 27 percent of Jupiter's mass, moving in a close inner orbit (0.14 AUs) with a period of 18.9 days. Within two days, however, the discovery announcement was retracted because the detected radial velocity variations could be attributed to the aging star's pulsations (more). In any case, the orbit of an Earth-like planet (with liquid water) around Zeta2 would have to be centered at around one AU -- the orbital distance Earth in the Solar System -- with an orbital period of just over a year. Around dimmer Zeta1, the orbit of an Earth-like planet would be closer in around 0.9 AU -- between the orbital distances of Venus and Earth in the Solar System -- with an orbital period of around 320 days.

Astronomers are hoping to use NASA's Terrestrial Planet Finder (TPF) and the ESA's Darwin planned groups of observatories to search for a rocky inner planet in the so-called "habitable zone" (HZ) around Zeta1 Reticuli. As currently planned, the TPF will include two complementary observatory groups: a visible-light coronagraph to launch around 2014; and a "formation-flying" infrared interferometer to launch before 2020, while Darwin will launch a flotilla of three mid-infrared telescopes and a fourth communications hub beginning in 2015.