Tau Ceti

Single yellow-hued star in the constellation Cetus

Not to be confused with T Ceti. For the video game, see Tau Ceti (video game).

Tau Ceti

Location of τ Ceti (circled)

Observation data
Epoch J2000 Equinox J2000
Constellation | Cetus
Pronunciation | /ˌtaʊ ˈsiːtaɪ/
Right ascension | 01h 44m 04.083s[1]
Declination | −15° 56′ 14.93″[1]
Apparent magnitude (V) | 3.50±0.01[2]
Characteristics
Evolutionary stage | Main sequence
Spectral type | G8V[3]
U−B color index | +0.21[4]
B−V color index | +0.72[4]
Astrometry
Radial velocity (Rv)| −16.68±0.05[5] km/s
Proper motion (μ)|  RA: −1721.728 mas/yr[1]
Dec.: +854.963 mas/yr[1]
Parallax (π)| 273.8097 ± 0.1701 mas[1]
Distance| 11.912 ± 0.007 ly
(3.652 ± 0.002 pc)
Absolute magnitude (MV)| 5.69±0.01[2]
Absolute bolometric
magnitude (Mbol)| 5.52±0.02[2]
Details
Mass| 0.800±0.008[6] M☉
Radius| 0.793±0.004[6] R☉
Luminosity| 0.488±0.010[2] L☉
Luminosity (visual, LV)| 0.45[nb 1] L☉
Surface gravity (log g)| 4.48±0.05[6] cgs
Temperature| 5,320±40[6] K
Metallicity| 28±3% Sun
Metallicity [Fe/H]| −0.55±0.05[7] dex
Rotation| 46±4 d[6]
Rotational velocity (v sin i)| 0.1±0.1[6] km/s
Age| 8–10[8] Gyr
Other designations

52 Cet, BD−16° 295, FK5 59, GJ 71, HD 10700, HIP 8102, HR 509, SAO 147986, LFT 159, LHS 146, LTT 935[4]

Database references
SIMBAD| data
Exoplanet Archive| data
ARICNS| data

Tau Ceti, Latinized from τ Ceti, is a single star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass. At a distance of just under 12 light-years (3.7 parsecs) from the Solar System, it is a relatively nearby star and the closest solitary G-class star. The star appears stable, with little stellar variation, and is metal-deficient (low in elements other than hydrogen and helium) relative to the Sun.

It can be seen with the unaided eye with an apparent magnitude of 3.5.[2] As seen from Tau Ceti, the Sun would be in the northern hemisphere constellation Boötes with an apparent magnitude of about 2.6.[nb 2][9]

Observations have detected more than ten times as much dust surrounding Tau Ceti as is present in the Solar System. Since December 2012, there has been evidence of at least four planets—all likely super-Earths—orbiting Tau Ceti, and two of these are potentially in the habitable zone.[10][11][12] There is evidence of up to an additional four unconfirmed planets, one of which would be a Jovian planet between 3 and 20 AU from the star.[13] Because of its debris disk, any planet orbiting Tau Ceti would face far more impact events than present day Earth. Note that those planetary candidates have been contested[14] and recent discoveries about the stellar inclination cast doubt about the terrestrial nature of these worlds.[6] Despite this hurdle to habitability, its solar analog (Sun-like) characteristics have led to widespread interest in the star. Given its stability, similarity and relative proximity to the Sun, Tau Ceti is consistently listed as a target for the search for extraterrestrial intelligence (SETI).[15]

## Name

[edit]

The name "Tau Ceti" is the Bayer designation for this star, established in 1603 as part of German celestial cartographer Johann Bayer's Uranometria star catalogue: it is "number T" in Bayer's sequence of constellation Cetus. In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, written at Cairo about 1650, this star was designated Thālith al Naʽāmāt (ثالث النعامات - thālith al-naʽāmāt), which was translated into Latin as Tertia Struthionum, meaning the third of the ostriches.[16] This star, along with η Cet (Deneb Algenubi), θ Cet (Thanih Al Naamat), ζ Cet (Baten Kaitos), and υ Cet, were Al Naʽāmāt (النعامات), the Hen Ostriches.[17][18]

In Chinese astronomy, the "Square Celestial Granary" (Chinese: 天倉; pinyin: Tiān Cāng) refers to an asterism consisting of τ Ceti, ι Ceti, η Ceti, ζ Ceti, θ Ceti and 57 Ceti.[19] Consequently, the Chinese name for τ Ceti itself is "the Fifth Star of Square Celestial Granary" (Chinese: 天倉五; pinyin: Tiān Cāng wǔ).[20]

## Motion

[edit]

The proper motion of a star is its rate of movement across the celestial sphere, determined by comparing its position relative to more distant background objects. Tau Ceti is considered to be a high-proper-motion star, although it only has an annual traverse of just under 2 arc seconds.[nb 3] Thus it will require about 2000 years before the location of this star shifts by more than a degree. A high proper motion is an indicator of closeness to the Sun.[21] Nearby stars can traverse an angle of arc across the sky more rapidly than the distant background stars and are good candidates for parallax studies. In the case of Tau Ceti, the parallax measurements indicate a distance of 11.9 ly. This makes it one of the closest star systems to the Sun and the next-closest spectral class-G star after Alpha Centauri A.[22]

The radial velocity of a star is the component of its motion that is toward or away from the Sun. Unlike proper motion, a star's radial velocity cannot be directly observed, but can be determined by measuring its spectrum. Due to the Doppler shift, the absorption lines in the spectrum of a star will be shifted slightly toward the red (or longer wavelengths) if the star is moving away from the observer, or toward blue (or shorter wavelengths) when it moves toward the observer. In the case of Tau Ceti, the radial velocity is about −17 km/s, with the negative value indicating that it is moving toward the Sun.[23] The star will make its closest approach to the Sun in about 43,000 years, when it comes to within 10.6 ly (3.25 pc).[24]

The distance to Tau Ceti, along with its proper motion and radial velocity, together give the motion of the star through space. The space velocity relative to the Sun is 37.2 km/s.[25] This result can then be used to compute an orbital path of Tau Ceti through the Milky Way. It has a mean galacto-centric distance of 9.7 kiloparsecs (32000 ly) and an orbital eccentricity of 0.22.[26]

## Physical properties

[edit]

The Sun (left) is both larger and somewhat hotter than the less active Tau Ceti (right).

The Tau Ceti system is believed to have only one stellar component. A dim optical companion has been observed with magnitude 13.1. As of 2000, it was 137 arcseconds distant from the primary. It may be gravitationally bound, but it is considered more likely to be a line-of-sight coincidence.[27][28][29]

Most of what is known about the physical properties of Tau Ceti and its system has been determined through spectroscopic measurements. By comparing the spectrum to computed models of stellar evolution, the age, mass, radius and luminosity of Tau Ceti can be estimated. However, using an astronomical interferometer, measurements of the radius of the star can be made directly to an accuracy of 0.5%.[2] Through such means, the radius of Tau Ceti has been measured to be 79.3%±0.4% of the solar radius.[2] This is about the size that is expected for a star with somewhat lower mass than the Sun.[30]

### Rotation

[edit]

The rotation period for Tau Ceti was measured by periodic variations in the classic H and K absorption lines of singly ionized calcium (Ca II). These lines are closely associated with surface magnetic activity,[31] so the period of variation measures the time required for the activity sites to complete a full rotation about the star. By this means the rotation period for Tau Ceti is estimated to be 34 d.[32] Due to the Doppler effect, the rotation rate of a star affects the width of the absorption lines in the spectrum (light from the side of the star moving away from the observer will be shifted to a longer wavelength; light from the side moving towards the observer will be shifted toward a shorter wavelength). By analyzing the width of these lines, the rotational velocity of a star can be estimated. The projected rotation velocity for Tau Ceti is

veq · sin i ≈ 1 km/s,

where veq is the velocity at the equator, and i is the inclination angle of the rotation axis to the line of sight. For a typical G8 star, the rotation velocity is about 2.5 km/s. The relatively low rotational velocity measurements may indicate that Tau Ceti is being viewed from nearly the direction of its pole.[33][34]

More recently, a 2023 study has estimated a rotation period of 46±4 d and a veq sin i of 0.1±0.1 km/s, corresponding to a pole-on inclination of 7°±7°.[6]

### Metallicity

[edit]

The chemical composition of a star provides important clues to its evolutionary history, including the age at which it formed. The interstellar medium of dust and gas from which stars form is primarily composed of hydrogen and helium with trace amounts of heavier elements. As nearby stars continually evolve and die, they seed the interstellar medium with an increasing portion of heavier elements. Thus younger stars tend to have a higher portion of heavy elements in their atmospheres than do the older stars. These heavy elements are termed "metals" by astronomers, and the portion of heavy elements is the metallicity.[35] The amount of metallicity in a star is given in terms of the ratio of iron (Fe), an easily observed heavy element, to hydrogen. A logarithm of the relative iron abundance is compared to the Sun. In the case of Tau Ceti, the atmospheric metallicity is

[ Fe H ] ≈ − 0.50 {\displaystyle \left[{\frac {\text{Fe}}{\text{H}}}\right]\approx -0.50} dex,

equivalent to about a third the solar abundance. Past measurements have varied from −0.13 to −0.60.[36][37]

This lower abundance of iron indicates that Tau Ceti is almost certainly older than the Sun. Its age had previously been estimated to be 5.8 Gyr, but is now thought to be around 9 Gyr.[8] This compares with 4.57 Gyr for the Sun. However, age estimates for Tau Ceti can range from 4.4 to 12 Gyr, depending on the model adopted.[30]

Besides rotation, another factor that can widen the absorption features in the spectrum of a star is pressure broadening. The presence of nearby particles affects the radiation emitted by an individual particle. So the line width is dependent on the surface pressure of the star, which in turn is determined by the temperature and surface gravity. This technique was used to determine the surface gravity of Tau Ceti. The log g, or logarithm of the star's surface gravity, is about 4.4, very close to the log g = 4.44 for the Sun.[36]

### Luminosity and variability

[edit]

The luminosity of Tau Ceti is equal to only 55% of the Sun's luminosity.[26] A terrestrial planet would need to orbit this star at a distance of about 0.7 AU to match the solar insolation level of Earth. This is approximately the same as the average distance between Venus and the Sun.

The chromosphere of Tau Ceti—the portion of a star's atmosphere just above the light-emitting photosphere—currently displays little or no magnetic activity, indicating a stable star.[38] One 9-year study of temperature, granulation, and the chromosphere showed no systematic variations; Ca II emissions around the H and K infrared bands show a possible 11-year cycle, but this is weak relative to the Sun.[33] Alternatively it has been suggested that the star could be in a low-activity state analogous to a Maunder Minimum—a historical period, associated with the Little Ice Age in Europe, when sunspots became exceedingly rare on the Sun's surface.[39][40] Spectral line profiles of Tau Ceti are extremely narrow, indicating low turbulence and observed rotation.[41] The star's asteroseismological oscillations have an amplitude about half that of the Sun and a lower mode lifetime.[2]

## Planetary system

[edit]

The Tau Ceti planetary system[7][13][42][43][44] Companion
(in order from star) | Mass | Semimajor axis
(AU) | Orbital period
(days) | Eccentricity | Inclination | Radius

|
|
|
|
|
|

b (unconfirmed) | ≥2.0 ± 0.8 M🜨 | 0.105+0.005
−0.006 | 13.965+0.017
−0.024 | 0.16 ± 0.22  | —  | —
g (unconfirmed) | ≥1.75+0.25
−0.40 M🜨 | 0.133+0.001
−0.002 | 20.00+0.02
−0.01 | 0.06 ± 0.13  | —  | —
c (unconfirmed) | ≥3.1+1.4
−1.1 M🜨 | 0.195+0.009
−0.011 | 35.362+0.088
−0.106 | 0.03 ± 0.28  | —  | —
h (unconfirmed) | ≥1.83+0.68
−0.26 M🜨 | 0.243 ± 0.003  | 49.41+0.08
−0.10 | 0.23+0.16
−0.15 | —  | —
d (unconfirmed) | ≥3.6 ± 1.7 M🜨 | 0.374+0.017
−0.020 | 94.11+0.70
−0.63 | 0.08 ± 0.26  | —  | —
e (unconfirmed) | ≥3.93+0.83
−0.64 M🜨 | 0.538 ± 0.006  | 162.87+1.08
−0.46 | 0.18+0.18
−0.14 | —  | —
f (unconfirmed) | ≥3.93+1.05
−1.37 M🜨 | 1.334+0.017
−0.044 | 636.13+11.70
−47.69 | 0.16+0.07
−0.16 | —  | —
i (unconfirmed) | ≤5 MJ | 3–20  | —  | —  | —  | —
Debris disk | 6.2+9.8
−4.6–52+3
−8 AU | 35±10° | —

Principal factors driving research interest in Tau Ceti are its proximity, its Sun-like characteristics, and the implications for possible life on its planets. For categorization purposes, Hall and Lockwood report that "the terms 'solarlike star', 'solar analog', and 'solar twin' [are] progressively restrictive descriptions".[45] Tau Ceti fits the second category, given its similar mass and low variability, but relative lack of metals. The similarities have inspired popular culture references for decades, as well as scientific examination. In 1988, radial-velocity observations ruled out any periodical variations attributable to massive planets around Tau Ceti inside of Jupiter-like distances.[46][47] Ever more precise measurements continue to rule out such planets, at least until December 2012.[47] The velocity precision reached is about 11 m/s measured over a 5-year time span.[48] This result excludes hot Jupiters and probably excludes any planets with minimal mass greater than or equal to Jupiter's mass and with orbital periods less than 15 years.[49] In addition, a survey of nearby stars by the Hubble Space Telescope's Wide Field and Planetary Camera was completed in 1999, including a search for faint companions to Tau Ceti; none were discovered to limits of the telescope's resolving power.[50]

However, these searches only excluded larger brown dwarf bodies and closer orbiting giant planets, so smaller, Earth-like planets in orbit around the star, like those discovered in 2012, were not precluded.[50] If hot Jupiters were to exist in close orbit, they would likely disrupt the star's habitable zone; their exclusion was thus considered positive for the possibility of Earth-like planets.[46][51] General research has shown a positive correlation between the presence of planets and a relatively high-metallicity parent star, suggesting that stars with lower metallicity such as Tau Ceti have a lower chance of having planets.[52]

### Discovery

[edit]

On December 19, 2012, evidence was presented that suggested a system of five planets orbiting Tau Ceti.[7] The planets' estimated minimum masses were between 2 and 6 Earth masses, with orbital periods ranging from 14 to 640 days. One of them, Tau Ceti e, appears to orbit about half as far from Tau Ceti as Earth does from the Sun. With Tau Ceti's luminosity of 52% that of the Sun and a distance from the star of 0.552 AU, the planet would receive 1.71 times as much stellar radiation as Earth does, slightly less than Venus with 1.91 times Earth's. Nevertheless, some research places it within the star's habitable zone.[10][11] The Planetary Habitability Laboratory has estimated that Tau Ceti f, which receives 28.5% as much starlight as Earth, would be within the star's habitable zone, albeit narrowly.[12]

New results were published in August 2017.[43] They confirmed Tau Ceti e and f as candidates but failed to consistently detect planets b (which may be a false negative), c (whose weakly defined apparent signal was correlated to stellar rotation), and d (which did not show up in all data sets). Instead, they found two new planetary candidates, g and h, with orbits of 20 and 49 days. The signals detected from the candidate planets have radial velocities as low as 30 cm/s, and the experimental method used in their detection, as it was applied to HARPS, could in theory have detected down to around 20 cm/s.[43] The updated 4-planet model is dynamically packed and potentially stable for billions of years.

However, with further refinements, even more candidate planets have been detected. In 2019, a paper published in Astronomy & Astrophysics suggested that Tau Ceti could have a Jupiter or super-Jupiter based on a tangential astrometric velocity of around 11.3 m/s. The exact size and position of this conjectured object have not been determined, though it is at most 5 Jupiter masses if it orbits between 3 and 20 AU.[13][nb 4] A 2020 Astronomical Journal study by astronomers Jamie Dietrich and Daniel Apai analyzed the orbital stability of the known planets and, considering statistical patterns identified from hundreds of other planetary systems, explored the orbits in which the presence of additional, yet-undetected planets are most likely. This analysis predicted three planet candidates at orbits coinciding with planet candidates b, c, and d.[54] The close match between the independently predicted planet periods and the periods of the three planet candidates previously identified in radial velocity data supports the genuine planetary nature of candidates b, c, and d. Furthermore, the study also predicts at least one yet-undetected planet between planets e and f, i.e., within the habitable zone.[54] This predicted exoplanet is identified as PxP-4.[nb 5]

All proposed planet candidates remain unconfirmed; studies of Tau Ceti's radial velocity in 2019 and 2021 were unable to confirm any planets.[55][14]

Since Tau Ceti is likely aligned in such a way that it is nearly pole-on to Earth (as indicated by its rotation),[6] if its planets share this alignment and have nearly face-on orbits, they would be less similar to Earth's mass and more to Neptune, Saturn, or Jupiter. For example, were Tau Ceti f's orbit inclined 70 degrees from being face-on to Earth, its mass would be 4.18+1.12
−1.46 Earth masses, making it a middle-to-low end super-Earth. However, these scenarios aren't necessarily true; since Tau Ceti's debris disk has an inclination of 35±10, the planets' orbits could be similarly inclined. If the debris disk and f's orbits were assumed to be equal, f would be between 5.56+1.48
−1.94 and 9.30+2.48
−3.24 Earth masses, making it slightly more likely to be a mini-Neptune. On top of that, the lower the inclination of the planetary orbits the less stable they tend to be over a given time period, as the planets would have greater masses and therefore more gravitational pull which would in turn disturb the orbital stability of neighbouring planets. So, for example, if as estimated in the Korolik et al 2023 study Tau Ceti has a pole-on inclination of around 7 degrees, and the postulated planets do as well, then those planets' orbits would be verging on instability within just a 10 million year timeframe, and therefore it is extremely unlikely they would have survived for the billions of years that make up the lifetime of the star system.[6]

### Tau Ceti e

[edit]

Main article: Tau Ceti e

Tau Ceti e is a candidate[43] planet orbiting Tau Ceti that was first proposed in 2012 by statistical analyses of the data of the star's variations in radial velocity that were obtained using HIRES, AAPS, and HARPS.[7][56] Its possible properties were refined in 2017:[43] if confirmed, it would orbit at a distance of 0.552 AU (between the orbits of Venus and Mercury in the Solar System) with an orbital period of 168 days and has a minimum mass of 3.93 Earth masses. If Tau Ceti e possessed an Earth-like atmosphere, the surface temperature would be around 68 °C (154 °F).[57] Based upon the incident flux upon the planet, a study by Güdel et al. (2014) speculated that the planet may lie outside the habitable zone and closer to a Venus-like world.[58]

### Tau Ceti f

[edit]

Main article: Tau Ceti f

Tau Ceti f is a candidate[43] planet orbiting Tau Ceti that was proposed in 2012 by statistical analyses of the star's variations in radial velocity, and also recovered by further analysis in 2017.[7] It is of interest because its orbit places it in Tau Ceti's extended habitable zone.[59] However, a 2015 study implies that it would have been in the temperate zone for less than one billion years, so there may not be a detectable biosignature.[60][61][62]

Few properties of the planet are known other than its orbit and mass. It orbits Tau Ceti at a distance of 1.35 AU (near Mars's orbit in the Solar System) with an orbital period of 642 days and has a minimum mass of 3.93 Earth masses.[43]

However, a reanalysis of the data in 2021 provided an in-depth study of the HARPS spectrograph systematics, showing that the 600-day signal was likely a spurious combination of instrumental systematics with a potential 1000-day yet unknown signal.[14]

### Debris disk

[edit]

In 2004, a team of UK astronomers led by Jane Greaves discovered that Tau Ceti has more than ten times the amount of cometary and asteroidal material orbiting it than does the Sun. This was determined by measuring the disk of cold dust orbiting the star produced by collisions between such small bodies.[63] This result puts a damper on the possibility of complex life in the system, because any planets would suffer from large impact events roughly ten times more frequently than present day Earth. Greaves noted at the time of her research that "it is likely that [any planets] will experience constant bombardment from asteroids of the kind believed to have wiped out the dinosaurs".[64] Such bombardments would inhibit the development of biodiversity between impacts.[65] However, it is possible that a large Jupiter-sized gas giant (such as the proposed planet "i") could deflect comets and asteroids.[63]

The debris disk was discovered by measuring the amount of radiation emitted by the system in the far infrared portion of the spectrum. The disk forms a symmetric feature that is centered on the star, and its outer radius averages 55 AU. The lack of infrared radiation from the warmer parts of the disk near Tau Ceti implies an inner cut-off at a radius of 10 AU. By comparison, the Solar System's Kuiper belt extends from 30 to 50 AU. To be maintained over a long period of time, this ring of dust must be constantly replenished through collisions by larger bodies.[63] The bulk of the disk appears to be orbiting Tau Ceti at a distance of 35–50 AU, well outside the orbit of the habitable zone. At this distance, the dust belt may be analogous to the Kuiper belt that lies outside the orbit of Neptune in the Solar System.[63]

Tau Ceti shows that stars need not lose large disks as they age, and such a thick belt may not be uncommon among Sun-like stars.[66] Tau Ceti's belt is only 1/20 as dense as the belt around its young neighbor, Epsilon Eridani.[63] The relative lack of debris around the Sun may be the unusual case: one research-team member suggests the Sun may have passed close to another star early in its history and had most of its comets and asteroids stripped away.[64] Stars with large debris disks have changed the way astronomers think about planet formation because debris disk stars, where dust is continually generated by collisions, appear to form planets readily.[66]

### Habitability

[edit]

Tau Ceti's habitable zone—the locations where liquid water could be present on an Earth-sized planet—spans a radius of 0.55–1.16 AU, where 1 AU is the average distance from the Earth to the Sun.[67] Primitive life on Tau Ceti's planets may reveal itself through an analysis of atmospheric composition via spectroscopy, if the composition is unlikely to be abiotic, just as oxygen on Earth is indicative of life.[68]

Tau Ceti could have been a search target for the canceled Terrestrial Planet Finder

The most optimistic search project to date was Project Ozma, which was intended to "search for extraterrestrial intelligence" (SETI) by examining selected stars for indications of artificial radio signals. It was run by the astronomer Frank Drake, who selected Tau Ceti and Epsilon Eridani as the initial targets. Both are located near the Solar System and are physically similar to the Sun. No artificial signals were found despite 200 hours of observations.[69] Subsequent radio searches of this star system have turned up negative.

This lack of results has not dampened interest in observing the Tau Ceti system for biosignatures. In 2002, astronomers Margaret Turnbull and Jill Tarter developed the Catalog of Nearby Habitable Systems (HabCat) under the auspices of Project Phoenix, another SETI endeavour. The list contained more than 17000 theoretically habitable systems, approximately 10% of the original sample.[70] The next year, Turnbull would further refine the list to the 30 most promising systems out of 5000 within 100 light-years from the Sun, including Tau Ceti; this will form part of the basis of radio searches with the Allen Telescope Array.[71] She chose Tau Ceti for a final shortlist of just five stars suitable for searches by the (now cancelled)[72] Terrestrial Planet Finder telescope system, commenting that "these are places I'd want to live if God were to put our planet around another star".[73]

## See also

[edit]

* Epsilon Eridani
* List of nearest stars
* List of potentially habitable exoplanets
* List of nearest terrestrial exoplanet candidates
* Tau Ceti in fiction

## Notes

[edit]

1. ^ From knowing the absolute visual magnitude of Tau Ceti,  M V ∗ = 5.69 {\displaystyle M_{V_{\ast }}=5.69} , and the absolute visual magnitude of the Sun,  M V ⊙ = 4.83 {\displaystyle M_{V_{\odot }}=4.83} , the visual luminosity of Tau Ceti can therefore be calculated:  L V ∗ / L V ⊙ = 10 0.4 ( M V ⊙ − M V ∗ ) {\displaystyle L_{V_{\ast }}/L_{V_{\odot }}=10^{0.4(M_{V_{\odot }}-M_{V_{\ast }})}} .
2. ^ From Tau Ceti the Sun would appear on the diametrically opposite side of the sky at the coordinates RA = 13h 44m 04s, Dec = 15° 56′ 14″, which is located near Tau Boötis. The absolute magnitude of the Sun is 4.8, so, at a distance of 3.65 pc, the Sun would have an apparent magnitude  m = M v + 5 ⋅ ( log 10 ⁡ 3.64 − 1 ) = 2.6 {\displaystyle m=M_{v}+5\cdot (\log _{10}3.64-1)=2.6} .
3. ^ The net proper motion is given by  μ = μ δ 2 + μ α 2 ⋅ cos 2 ⁡ δ = 1907.79 mas/y {\displaystyle \mu ={\sqrt {\mu _{\delta }^{2}+\mu _{\alpha }^{2}\cdot \cos ^{2}\delta }}=1907.79~{\text{mas/y}}} , where μα and μδ are the components of proper motion in the RA and declination respectively, and δ is the declination. See: Majewski, Steven R. (2006). "Stellar Motions". University of Virginia. Archived from the original on 2012-01-25. Retrieved 2007-09-27.
4. ^ If a planet is confirmed to be the cause of this signal, as of August 2020 it would be designated as Tau Ceti i in accordance with IAU exoplanet naming policies.[53]
5. ^ If a planet corresponding to this predicted candidate is confirmed, as of August 2020 it would be designated as Tau Ceti i in accordance with IAU exoplanet naming policies, or Tau Ceti j were the candidate Jovian planet confirmed first.[53]

## References

[edit]

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66. ^ a b Greaves, Jane S. (January 2005). "Disks Around Stars and the Growth of Planetary Systems". Science. 307 (5706): 68–71\. Bibcode:2005Sci...307...68G. doi:10.1126/science.1101979. PMID 15637266. S2CID 27720602.68-71&rft.date=2005-01&rft_id=info:doi/10.1126/science.1101979&rft_id=https://api.semanticscholar.org/CorpusID:27720602#id-name=S2CID&rft_id=info:pmid/15637266&rft_id=info:bibcode/2005Sci...307...68G&rft.aulast=Greaves&rft.aufirst=Jane+S.&rfr_id=info:sid/en.wikipedia.org:Tau+Ceti" class="Z3988">
67. ^ Cantrell, Justin R; et al. (October 2013). "The Solar Neighborhood XXIX: The Habitable Real Estate of Our Nearest Stellar Neighbors". The Astronomical Journal. 146 (4): 99. arXiv:1307.7038. Bibcode:2013AJ....146...99C. doi:10.1088/0004-6256/146/4/99. S2CID 44208180.
68. ^ Woolf, Neville; Angel, J. Roger (September 1998). "Astronomical Searches for Earth-like Planets and Signs of Life". Annual Review of Astronomy and Astrophysics. 36 (1): 507–537\. Bibcode:1998ARA&A..36..507W. doi:10.1146/annurev.astro.36.1.507. S2CID 45235649.507-537&rft.date=1998-09&rft_id=https://api.semanticscholar.org/CorpusID:45235649#id-name=S2CID&rft_id=info:doi/10.1146/annurev.astro.36.1.507&rft_id=info:bibcode/1998ARA&A..36..507W;&rft.aulast=Woolf&rft.aufirst=Neville&rft.au=Angel,+J.+Roger&rfr_id=info:sid/en.wikipedia.org:Tau+Ceti" class="Z3988">
69. ^ Alexander, Amir (2006). "The Search for Extraterrestrial Intelligence, A Short History". The Planetary Society. Archived from the original on 2007-09-29. Retrieved 2006-11-08.
70. ^ Turnbull, Margaret C.; Tarter, Jill (March 2003). "Target Selection for SETI. I. A Catalog of Nearby Habitable Stellar Systems". Astrophysical Journal Supplement Series. 145 (1): 181–198\. arXiv:astro-ph/0210675. Bibcode:2003ApJS..145..181T. doi:10.1086/345779. S2CID 14734094.181-198&rft.date=2003-03&rft_id=info:arxiv/astro-ph/0210675&rft_id=https://api.semanticscholar.org/CorpusID:14734094#id-name=S2CID&rft_id=info:doi/10.1086/345779&rft_id=info:bibcode/2003ApJS..145..181T&rft.aulast=Turnbull&rft.aufirst=Margaret+C.&rft.au=Tarter,+Jill&rfr_id=info:sid/en.wikipedia.org:Tau+Ceti" class="Z3988">
71. ^ "Stars and Habitable Planets". Sol Company. Archived from the original on 2011-06-28. Retrieved 2007-09-21.
72. ^ "NASA budget statement". Planetary Society. 2006-02-06. Archived from the original on 2006-06-16. Retrieved 2006-07-17.
73. ^ "Astronomer Margaret Turnbull: A Short-List of Possible Life-Supporting Stars". American Association for the Advancement of Science. February 18, 2006. Archived from the original on July 22, 2011. Retrieved 2007-09-21.

## Further reading

[edit]

* Pagano, Michael; et al. (April 2015), "The Chemical Composition of τ Ceti and Possible Effects on Terrestrial Planets", The Astrophysical Journal, 803 (2): 90, arXiv:1503.04189, Bibcode:2015ApJ...803...90P, doi:10.1088/0004-637X/803/2/90, S2CID 119103881, 90.
* Teixeira, T. C.; et al. (January 2009), "Solar-like oscillations in the G8 V star τ Ceti", Astronomy and Astrophysics, 494 (1): 237–242, arXiv:0811.3989, Bibcode:2009A&A...494..237T, doi:10.1051/0004-6361:200810746, S2CID 59353134.237-242&rft.date=2009-01&rft_id=info:arxiv/0811.3989&rft_id=https://api.semanticscholar.org/CorpusID:59353134#id-name=S2CID&rft_id=info:doi/10.1051/0004-6361:200810746&rft_id=info:bibcode/2009A&A...494..237T;&rft.aulast=Teixeira&rft.aufirst=T.+C.&rft.au=Kjeldsen,+H.&rft.au=Bedding,+T.+R.&rft.au=Bouchy,+F.&rft.au=Christensen-Dalsgaard,+J.&rft.au=Cunha,+M.+S.&rft.au=Dall,+T.&rft.au=Frandsen,+S.&rft.au=Karoff,+C.&rft.au=Monteiro,+M.+J.+P.+F.+G.&rft.au=Pijpers,+F.+P.&rfr_id=info:sid/en.wikipedia.org:Tau+Ceti" class="Z3988">
* di Folco, E.; et al. (November 2007), "A near-infrared interferometric survey of debris disk stars. I. Probing the hot dust content around ɛ Eridani and τ Ceti with CHARA/FLUOR", Astronomy and Astrophysics, 475 (1): 243–250, arXiv:0710.1731, Bibcode:2007A&A...475..243D, doi:10.1051/0004-6361:20077625, S2CID 9594917.243-250&rft.date=2007-11&rft_id=info:arxiv/0710.1731&rft_id=https://api.semanticscholar.org/CorpusID:9594917#id-name=S2CID&rft_id=info:doi/10.1051/0004-6361:20077625&rft_id=info:bibcode/2007A&A...475..243D;&rft.aulast=di+Folco&rft.aufirst=E.&rft.au=Absil,+O.&rft.au=Augereau,+J.+-C.&rft.au=Mérand,+A.&rft.au=Coudé+du+Foresto,+V.&rft.au=Thévenin,+F.&rft.au=Defrère,+D.&rft.au=Kervella,+P.&rft.au=ten+Brummelaar,+T.+A.&rft.au=McAlister,+H.+A.&rft.au=Ridgway,+S.+T.&rft.au=Sturmann,+J.&rft.au=Sturmann,+L.&rft.au=Turner,+N.+H.&rfr_id=info:sid/en.wikipedia.org:Tau+Ceti" class="Z3988">
* Rammacher, W.; Cuntz, M. (September 2003), "Acoustic Heating Models for the Basal Flux Star τ Ceti Including Time-dependent Ionization: Results for Ca II and Mg II Emission", The Astrophysical Journal, 594 (1): L51 – L54, Bibcode:2003ApJ...594L..51R, doi:10.1086/378312, S2CID 120328068.L51+-+L54&rft.date=2003-09&rft_id=https://api.semanticscholar.org/CorpusID:120328068#id-name=S2CID&rft_id=info:doi/10.1086/378312&rft_id=info:bibcode/2003ApJ...594L..51R&rft.aulast=Rammacher&rft.aufirst=W.&rft.au=Cuntz,+M.&rfr_id=info:sid/en.wikipedia.org:Tau+Ceti" class="Z3988">
* Gray, David F.; Baliunas, Sallie L. (June 1994), "The Activity Cycle of tau Ceti", Astrophysical Journal, 427: 1042, Bibcode:1994ApJ...427.1042G, doi:10.1086/174210.
* Arribas, S.; Martinez-Roger, C. (1988), Cayrel de Strobel, G.; Spite, Monique (eds.), "Iron Lines and Surface Gravity Determination for τ Ceti", The Impact of Very High S/N Spectroscopy on Stellar Physics: Proceedings of the 132nd Symposium of the International Astronomical Union held in Paris, France, June 29-July 3, 1987. International Astronomical Union. Symposium no. 132, vol. 132, Dordrecht: Kluwer Academic Publishers, p. 445, Bibcode:1988IAUS..132..445A.

## External links

[edit]

Wikimedia Commons has media related to Tau Ceti.

* Tau Ceti at Jim Kaler's STARS site
* Tau Ceti: Life Amidst Catastrophe? at Centauri Dreams

* v
* t
* e

Tau Ceti system

Stars|

* Tau Ceti

Planets
(parentheses are unconfirmed) |

* (b)
* g
* (c)
* h
* (d)
* e
* (PxP-5)
* (PxP-4)
* f
* (i)

See also
Exoplanets

* v
* t
* e

← Celestial objects within 10–15 light-years →

| Primary member type|

Celestial objects by systems.

| Subgiant stars|

| F-type|

* Procyon (Alpha Canis Minoris) (11.402±0.032 ly)
* white dwarf B

|

| Main-sequence
stars|

| G-type|

* Tau Ceti (11.9118±0.0074 ly)
* 4 (8?) planets: (b), (c), (d), e, f, g, h, (i)

|

K-type|

* Epsilon Eridani (Ran) (10.4749±0.0037 ly)
* 1 (2?) planets: b (Ægir), c?
* 61 Cygni (11.4039±0.0012 ly)
* K-type main-sequence star B
* Epsilon Indi (11.8670±0.0041 ly)
* 2 T-type brown dwarfs: Ba, Bb
* planet Ab

M-type
(red dwarfs)|

* Ross 248 (10.3057±0.0014 ly)
* Lacaille 9352 (10.7241±0.0007 ly)
* 2 (3?) planets: b, c, d?
* Ross 128 (11.0074±0.0011 ly)
* planet b
* EZ Aquarii (11.109±0.034 ly)
* 2 red dwarfs: B, C
* Struve 2398 (11.4908±0.0009 ly)
* red dwarf B
* 1 (3?) planets: Ab, Bb?, Bc?
* Groombridge 34 (11.6191±0.0008 ly)
* red dwarf B
* 2 planets: Ab, Ac
* DX Cancri (11.6797±0.0027 ly)
* GJ 1061 (11.9839±0.0014 ly)
* 3 planets: b, c, d
* YZ Ceti (12.1222±0.0015 ly)
* 3 planets: b, c, d
* Luyten's Star (12.3485±0.0019 ly)
* 2 (4?) planets: b, c, d?, e?
* Teegarden's Star (12.4970±0.0045 ly)
* 3 planets: b, c, d
* Kapteyn's Star (12.8308±0.0008 ly)
* Lacaille 8760 (12.9472±0.0018 ly)
* SCR 1845−6357 (13.0638±0.0070 ly)
* T-type brown dwarf B
* Kruger 60 (13.0724±0.0052 ly)
* red dwarf B
* DENIS J1048−3956 (13.1932±0.0027 ly)
* Ross 614 (13.363±0.040 ly)
* red dwarf B
* Wolf 1061 (14.0500±0.0016 ly)
* 3 planets: b, c, d
* Gliese 1 (14.1747±0.0022 ly)
* TZ Arietis (14.5780±0.0046 ly)
* planet b
* Wolf 424 (14.595±0.031 ly)
* red dwarf B
* Gliese 687 (14.8395±0.0014 ly)
* 2 planets: b, c
* Gliese 674 (14.8492±0.0018 ly)
* planet b
* LHS 292 (14.8706±0.0041 ly)

| Degenerate
stars|

| White dwarfs|

* van Maanen 2 (14.0718±0.0011 ly)

|

| Brown dwarfs|

| T-type|

* UGPS J0722-0540 (13.43±0.13 ly)

|

* v
* t
* e

Constellation of Cetus

* List of stars in Cetus
* Cetus in Chinese astronomy

Stars|

| Bayer|

* α (Menkar)
* β (Diphda)
* γ (Kaffaljidhma)
* δ
* ε
* ζ (Baten Kaitos)
* η
* θ
* ι
* κ1
* κ2
* λ
* μ
* ν
* ξ1
* ξ2
* ο (Mira)
* A
* B
* π
* ρ
* σ
* τ
* υ
* φ1
* φ2
* φ3
* φ4
* χ

|

Flamsteed|

* 1
* 2
* 3
* 6
* 7
* 9
* 13
* 14
* 20
* 46
* 49
* 56 (υ1)
* 63
* 64
* 69
* 75
* 77
* 79
* 81
* 84
* 94
* 25 Ari

Variable|

* T
* UV
* YZ
* ZZ
* AY
* BL
* BW
* DK

HR|

* 10
* 72
* 159
* 228
* 500
* 672
* 870

HD|

* 984
* 1690
* 2638
* 4747
* 5319
* 6718
* 7449
* 11506
* 11964
* 15115
* 16008
* 224693 (Axólotl)

Other|

* 2MASS J01225093−2439505
* BD-07 436
* BD−17 63 (Felixvarela)
* Cayrel's Star
* CFBDS J005910.90–011401.3
* DENIS-P J020529.0−115925
* GD 40
* Gliese 65
* Gliese 105
* GJ 1002
* GJ 1005
* HIP 5158
* HIP 11952
* LHS 1140
* NGC 156
* NGC 158
* NGC 302
* NGC 308
* NGC 310
* PSR J0108−1431
* SDSS J001820.5−093939.2
* SDSS J0106−1000
* ULAS J003402.77−005206.7
* WD J2356−209
* WASP-20
* WASP-26
* WASP-44
* WASP-71 (Mpingo)
* WISE J0254+0223
* WHL0137-LS

| Exoplanets|

* 79 Ceti b
* 81 Ceti b
* 94 Ceti b
* BD−17 63 b
* HD 1461 b
* HD 2638 b
* HD 5319 b
* HD 11506 b
* c
* HD 11964 b
* c
* HD 224693 b
* HIP 5158 b
* c
* HIP 11915 b
* τ Ceti e
* f

|

| Nebulae|

* NGC 246

|

Galaxies|

| Messier|

* 77

|

NGC|

* 17
* 35
* 45
* 47
* 50
* 54
* 59
* 61
* 62
* 64
* 65
* 66
* 73
* 77
* 102
* 107
* 113
* 114
* 116
* 117
* 118
* 120
* 124
* 132
* 135
* 142
* 143
* 144
* 145
* 151
* 154
* 155
* 157
* 161
* 163
* 165
* 166
* 167
* 168
* 170
* 171
* 172
* 173
* 177
* 178
* 179
* 187
* 191
* 192
* 195
* 196
* 197
* 201
* 207
* 209
* 210
* 216
* 217
* 219
* 223
* 227
* 230
* 232
* 235
* 237
* 239
* 244
* 245
* 247
* 255
* 259
* 263
* 268
* 270
* 271
* 273
* 274
* 275
* 276
* 277
* 279
* 283
* 284
* 285
* 286
* 291
* 293
* 297
* 298
* 301
* 303
* 307
* 309
* 320
* 321
* 325
* 327
* 329
* 331
* 333
* 335
* 336
* 337
* 340
* 341
* 342
* 343
* 344
* 345
* 347
* 349
* 350
* 351
* 352
* 353
* 355
* 356
* 357
* 359
* 363
* 364
* 367
* 369
* 377
* 391
* 413
* 417
* 426
* 428
* 429
* 430
* 435
* 442
* 445
* 448
* 450
* 478
* 480
* 481
* 487
* 493
* 497
* 519
* 521
* 533
* 540
* 541
* 545
* 547
* 555
* 560
* 570
* 578
* 584
* 585
* 596
* 615
* 622
* 655
* 681
* 682
* 690
* 701
* 720
* 747
* 755
* 779
* 800
* 806
* 833
* 838
* 864
* 874
* 880
* 895
* 908
* 936
* 945
* 950
* 960
* 965
* 966
* 985
* 988
* 1009
* 1015
* 1019
* 1022
* 1032
* 1042
* 1052
* 1055
* 1073
* 1087
* 1090
* 1128
* 1142
* 1153
* 1218
* 7808
* 7828
* 7829

Other|

* Arp 146
* Arp 147
* Arp 256
* 3C 75
* Cetus Dwarf
* HCM-6A
* HD2
* Holmberg 15A
* HXMM01
* IC 1613
* IC 1623
* IRAS 01003-2238
* Markarian 1014
* Markarian 1018
* MCG -03-04-014
* PGC 2456
* SDSS J0303-0019
* SXDF-NB1006-2
* 9Spitch
* TON S180
* UGC 711
* UGC 1775
* Wolf–Lundmark–Melotte

| Galaxy clusters|

* Abell 133
* Abell 222
* Abell 223
* Abell 370
* Abell 400
* Arp 251
* Gioiello
* IRC 0218
* JKCS 041

|

| Astronomical events|

* SN 2005E
* SN 2005gj

|

Category

* v
* t
* e

2012 in space

* « 2011

2013 »

Space probe launches |

* High Resolution Coronal Imager (solar observatory; Jul 2012)
* Van Allen Probes (Earth orbiter; Aug 2012)

Impact events|

* Sutter's Mill meteorite
* 2012 UK meteoroid
* Novato meteorite

Selected NEOs|

* Asteroid close approaches
* 2012 BX34
* 433 Eros
* (192642) 1999 RD32
* 2012 FN
* 2012 FP35
* 2012 EG5
* 2012 KP24
* 2012 KT42
* 2012 LZ1
* (308242) 2005 GO21
* (523662) 2012 MU2
* 2012 TV
* 2012 TC4
* (214869) 2007 PA8
* 4179 Toutatis

Exoplanets |

* CFBDSIR 2149−0403 (rogue planet)
* CoRoT-21b
* Gliese 163 c
* Gliese 667
* Cc
* Cd
* Giese 676 A
* d
* e
* GJ 3470 b
* HD 40307
* e
* f
* g
* HW Virginis b
* J1407b (rogue object)
* Kappa Andromedae b
* KELT-2Ab
* Kepler-24
* b
* c
* Kepler-25
* b
* c
* Kepler-30
* b
* c
* d
* Kepler-32
* d
* e
* f
* Kepler-33
* b
* c
* d
* e
* f
* Kepler-34b
* Kepler-35b
* Kepler-36
* b
* c
* Kepler-42
* b
* c
* d
* Kepler-46
* b
* c
* Kepler-47
* b
* c
* Kepler-51
* b
* c
* Kepler-56
* b
* c
* Kepler-80
* b
* c
* d
* e
* f
* Kepler-84
* b
* c
* Kepler-89
* b
* c
* d
* e
* MOA-2010-BLG-477Lb
* PH1b
* Pr0201 b
* Pr0211 b
* Tau Ceti
* b?
* c?
* d?
* e
* f
* RR Caeli b
* WASP-47b
* WASP-49b
* WASP-56b
* WASP-66b
* WASP-79b

Discoveries|

* 2 moons of Jupiter
* LEDA 74886
* LAE J095950.99+021219.1
* BD+48 740
* Styx (moon)
* Q2343-BX442
* Phoenix Cluster
* WISE 1639−6847
* SN 2012fr
* NGC 1277 supermassive black hole
* Huge-LQG

Comets |

* 78P/Gehrels
* 21P/Giacobini–Zinner
* C/2012 E2 (SWAN)
* 96P/Machholz

Space exploration|

* Curiosity (Mars landing; Aug 2012)
* Dawn (departure from 4 Vesta; Sep 2012)
* Chang'e 2 (flyby of 4179 Toutatis; Dec 2012)
* GRAIL (lunar impacts; Dec 2012)

* Outer space portal
* Category:2011 in outer space — Category:2012 in outer space — Category:2013 in outer space

* v
* t
* e

2017 in space

* « 2016

2018 »

Space probe launches |

* ASTERIA (miniature space telescope; August 2017)

Impact events|

* Bolides in 2017
* 2017 China bolide

Selected NEOs|

* Asteroid close approaches
* 2017 AG13
* 2017 BS5
* 2017 BQ6
* 2016 WF9
* (671294) 2014 JO25
* 2017 OO1
* 2017 QP1
* 3122 Florence
* 2017 SX17
* 2012 TC4
* 2017 TD6
* 2017 VL2
* 2017 VW13
* 2017 XO2
* 3200 Phaethon

Exoplanets |

* HATS-36b
* HD 113996 b
* KELT-18b
* Kepler-19d
* Kepler-80g
* Kepler-90i
* K2-66b
* K2-138b
* LHS 1140 b
* Luyten b
* NGTS-1b
* OGLE-2016-BLG-1190Lb
* OGLE-2016-BLG-1195Lb
* Ross 128 b
* Tau Ceti
* g
* h
* TRAPPIST-1
* e
* f
* g
* h
* dark albedo of WASP-12b
* WASP-107b
* YZ Ceti
* b
* c
* d

Discoveries|

* GW170104
* Ring of Haumea
* 2 moons of Jupiter
* GW170608
* Saraswati Supercluster
* GW170814
* IGR J17329-2731 (X-ray source)
* GW170817 neutron star merger
* ʻOumuamua
* ULAS J1342+0928
* RZ Piscium

Comets |

* C/2016 U1 (NEOWISE)
* 41P/Tuttle–Giacobini–Kresák
* 103P/Hartley
* C/2015 ER61 (PanSTARRS)
* C/2015 V2 (Johnson)
* P/2006 VW139
* C/2017 O1 (ASASSN)
* 96P/Machholz

Space exploration|

* Cassini retirement (impacted into Saturn; Sep 2017)
* OSIRIS-REx (Earth gravity assist; Sep 2017)

* Outer space portal
* Category:2016 in outer space — Category:2017 in outer space — Category:2018 in outer space

* v
* t
* e

2019 in space

* « 2018

2020 »

Space probe
launches |

* Beresheet (lunar lander; Feb 2019)
* LightSail 2 (solar sail demonstration; Jun 2019)
* Chandrayaan-2 / Vikram / Pragyan (lunar obiter, lander and rover; Jul 2019)

Impact events|

* Kamchatka meteor (announced)
* 2019 MO

Selected NEOs|

* Asteroid close approaches
* 2018 XB4
* 2019 AS5
* 2016 AZ8
* 66391 Moshup
* 2019 OK
* 1620 Geographos
* 2006 QV89
* 2100 Ra-Shalom
* 2019 SU3
* 2019 TA7
* 2019 UN13

Exoplanets |

* AD Leonis b
* Beta Pictoris c
* DS Tucanae b
* Gliese 251 c
* Gliese 357 d
* Gliese 588
* b
* c
* Gliese 687 c
* Gliese 555 b
* Gliese 754 b
* Gliese 784 b
* HR 5183 b
* Kepler-47d confirmed
* K2-288Bb
* L 1159-16
* b
* c
* d
* LP 816-60 b
* LTT 1445 Ab
* Luyten's Star
* d
* e
* PDS 70c
* Proxima Centauri c
* Struve 2398
* Bb
* Bc
* Tau Ceti i (hypothesized)
* Teegarden's Star
* b
* c
* V1298 Tauri
* b
* c
* d
* e
* Wolf 359
* b
* c

Discoveries|

* 2019 AQ3
* ASASSN-19bt
* AT2019qiz
* GRB 190114C
* EPIC 204376071
* GW190412
* GW190521g (first-ever light from bh-bh merger)
* GW190814 (first-ever "mass-gap" collision)
* J043947.08+163415.7
* K2-18b water vapor
* M87* imaged
* PSR J0030+0451 mapped
* PSR J0740+6620
* S5-HVS1
* 2I/Borisov
* 20 moons of Saturn
* WD 0145+234 detection of exoasteroid disruption
* WD J0914+1914

Comets |

* C/2018 Y1 (Iwamoto)
* 78P/Gehrels
* 168P/Hergenrother
* 163P/NEAT
* 138P/Shoemaker–Levy
* 171P/Spahr
* 289P/Blanpain

Space exploration|

* New Horizons (encounter with 486958 Arrokoth; Dec 2018 / Jan 2019)
* Chang'e 4 / Yutu-2 (landing on the far side of the Moon; Jan 2019)
* Opportunity (end of mission; Aug 2018 / Feb 2019)
* Hayabusa2 (departure from 162173 Ryugu; Dec 2019)

* Outer space portal
* Category:2018 in outer space — Category:2019 in outer space — Category:2020 in outer space

* v
* t
* e

2020 in space

* « 2019

2021 »

Space probe
launches |

* Solar Orbiter (Feb 2020)
* Hope (Jul 2020)
* Tianwen-1 (Jul 2020)
* Mars 2020 (Jul 2020)
* Perseverance rover
* Mars Helicopter Ingenuity
* Chang'e 5 (lunar sample return mission; Nov 2020)

Impact events|

* 2020 China bolide

Selected
NEOs|

* Asteroid close approaches
* 594913 ꞌAylóꞌchaxnim
* 2020 BX12
* 2020 CW
* 2020 CD3 (temporary satellite)
* (52768) 1998 OR2
* 2020 HS7
* 2020 JJ
* 2020 LD
* (163348) 2002 NN4
* 2020 OY4
* 2020 QG
* 2011 ES4
* 2018 VP1
* 2020 SO (space debris)
* 2020 SW
* 2020 SL1
* 2020 UA
* 2020 VV
* 2020 VT4
* (153201) 2000 WO107
* (501647) 2014 SD224
* (614689) 2020 XL5

Exoplanets |

* AU Mic b
* Gliese 229 Ac
* Gliese 414
* Ab
* Ac
* Gliese 433
* b
* c
* d
* GJ 1151 b radio emissions
* K2-315b
* Kepler-1649c
* KOI-456.04
* Lacaille 9352
* b
* c
* M51-ULS-1b
* OGLE-2016-BLG-1928 (rogue planet)
* Tau Ceti j (predicted)
* TOI-561
* b
* c
* d
* e
* TOI-700
* b
* c
* d
* TOI-732
* b
* c
* TOI-1338 b
* TOI-1339
* b
* c
* d
* TYC 8998-760-1 c
* WD 1856+534 b

Discoveries|

* Betelgeuse dimming
* FRB 180916 location and periodicity
* Radcliffe wave
* Ophiuchus Supercluster explosion
* PSO J03094+27 (distant blazar)
* 2MASS J1047+21 wind speed measurements
* SGR 1935+2154 (soft gamma ray repeater)
* HR 6819 black hole hypothesis
* PHL 293B ending of P Cygni profile hydrogen emission lines
* Swift J1818.0–1607 (young magnetar)
* GW190814 (announced)
* South Pole Wall
* GW190521 (announced)
* Phosphine detection in the atmosphere of Venus
* Water detection on the sunlit surface of the Moon

Comets |

* C/2019 Y4 (ATLAS)
* P/2019 LD2 (ATLAS)
* C/2017 T2 (PANSTARRS)
* C/2020 F8 (SWAN)
* C/2019 U6 (LEMMON)
* C/2020 F3 (NEOWISE)
* 2P/Encke
* 88P/Howell
* 156P/Russell–LINEAR

Space
exploration|

* Spitzer retirement (Jan 2020)
* BepiColombo (Earth gravity assist; Apr 2020, Venus gravity assist; Oct 2020)
* OSIRIS-REx (sample collection from asteroid Bennu; Oct 2020)
* Hayabusa2 (sample return from asteroid Ryugu; Dec 2020)
* Chang'e 5 (lunar sample return; Dec 2020)

* Outer space portal
* Category:2019 in outer space — Category:2020 in outer space — Category:2021 in outer space

Portals:

* Astronomy
* Stars
* Spaceflight
* Outer space
* Solar System

*[RA:]: Right Ascension
*[Dec.:]: Declination
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template
*[Primary]: Primary member of a system is the brightest one (and, in most cases, also the most massive one).