V1400 Centauri

V1400 Centauri

V1400 Centauri imaged by the Dark Energy Survey
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension 14h 07m 47.92976s[1]
Declination −39° 45′ 42.7671″[1]
Apparent magnitude (V) 12.2–15.6[2]
Characteristics
Evolutionary stage Pre-main sequence[3]
Spectral type K5 IVe Li[3][4]
Variable type rotational T Tau and eclipsing[2]
Astrometry
Radial velocity (Rv)5.904±0.151[4] km/s
Proper motion (μ) RA: −23.108±0.015 mas/yr[1]
Dec.: −21.048±0.017 mas/yr[1]
Parallax (π)7.2351 ± 0.0140 mas[1]
Distance450.8 ± 0.9 ly
(138.2 ± 0.3 pc)
Details
MassGaia DR3 with magnetism:[5]
0.977+0.023
−0.045 M☉
Gaia DR3 without magnetism:[5]
0.891+0.062
−0.144 M☉
Gaia DR2:[6]: 2 
0.95±0.10 M☉
Radius1.0661+0.0062
−0.0139[7] R☉
Luminosity0.3431+0.0067
−0.0064[7] L☉
Surface gravity (log g)4.302+0.0243
−0.0243[7] cgs
Temperature4343+24
−29[7] K
Metallicity [Fe/H]−0.1903+0.0448
−0.0422[7] dex
Rotation3.206±0.002 d[8]: 6 [a]
Rotational velocity (v sin i)14.6±0.4[9] km/s
Age~16[3] or 21.38+4.30
−7.60[6]: 2  Myr
Other designations
V1400 Cen, GSC 07807-00004, 2MASS J14074792–3945427, WISE J140747.91–394542.9, 1SWASP J140747.93–394542.6, ASAS J140748–3945.7[4]
Database references
SIMBADdata

V1400 Centauri (known under its SuperWASP catalogue entry 1SWASP J140747.93−394542.6, or simply J1407) is a young, pre-main-sequence star that was eclipsed by a likely free-floating substellar object with a circumplanetary disk or rings (known as J1407b or Mamajek's Object[10]) in April–May 2007. With an age around 20 million years, the star is about as massive as the Sun and is located in the constellation Centaurus at a distance of 451 light-years away from the Sun. V1400 Centauri is a member of Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association, a group of young, comoving stars close to the Sun.

The discovery of J1407b and its 2007 eclipse of V1400 Centauri was announced in 2012 by a team of astronomers led by Eric E. Mamajek, who directed an analysis of photometric data from the Super Wide Angle Search for Planets (SuperWASP) sky survey. Mamajek's team hypothesized that J1407b is a substellar object that could either be orbiting the star as a planet or binary companion, or is a gravitationally unbound (free-floating) object that coincidentally passed in front of the star.[3] Later studies have since found evidence disfavoring the bound companion hypothesis: V1400 Centauri showed no eclipses after 2007 nor during the past 100 years,[6][8] which suggests that J1407b does not orbit the star.[6]: 7  Since this means J1407b is likely a free-floating object, its eclipse of V1400 Centauri would be considered an extremely rare event.[11]: 9 [b]

High-resolution imaging by the Atacama Large Millimeter Array (ALMA) in 2017 revealed a single faint object near V1400 Centauri, which could either be a young substellar object surrounded by a circumplanetary disk, or a background galaxy. The object's distance from V1400 Centauri appears to match the expected distance travelled by J1407b if it was a free-floating object. However, the faint object has only been observed once, so it is not yet confirmed whether it is a moving foreground object or a stationary background galaxy. If this faint object is J1407b, then it would have a mass below 6 Jupiter masses, which would also make it a sub-brown dwarf or a rogue planet.[12]

Name and catalogue history

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The star was first catalogued in the 1990s by the Hubble Guide Star Catalog, which found the star and measured its position in a pair of photographic plates taken in 1974 and 1979.[13] The star has been catalogued by other sky surveys, including the All Sky Automated Survey (ASAS), Two Micron All-Sky Survey (2MASS), Super Wide Angle Search for Planets (1SWASP), and the Wide-field Infrared Survey Explorer (WISE).[4] Typically in these catalogues, the star is given designations such as 1SWASP J140747.93–394542.6, which comprises the survey name followed by the star's location in equatorial coordinates.[4] As such designations can be unwieldy, researchers simply call the star "J1407".[3]: 5 [12] The star was given the official variable star designation V1400 Centauri in 2015, when it was added to the International Astronomical Union's General Catalogue of Variable Stars.[14]

Stellar properties

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Location and age

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V1400 Centauri is located in the constellation Centaurus.
V1400 Centauri is located in the constellation Centaurus.
V1400 Centauri
class=notpageimage|
Location of V1400 Centauri in the constellation Centaurus

V1400 Centauri is located in the constellation Centaurus, about 40 degrees south of the celestial equator. The most recent parallax measurements by the Gaia spacecraft indicate V1400 Centauri is located 450.8 ± 0.9 light-years (138.2 ± 0.3 parsecs) from the Sun.[1] Observations of V1400 Centauri's position over time have shown that it has a southwestward[c] proper motion consistent with that of the Scorpius–Centaurus association, an OB association of young stars with ages between 11–17 million years and distances between 380–470 ly (118–145 pc) from the Sun.[3]: 4  The Scorpius–Centaurus association is the nearest OB association to the Sun, and is believed to have formed out of a molecular cloud that has since been blown away by the stellar winds of the association's most massive stars.[15]: 236, 250 

V1400 Centauri is closest to the Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association, which has an age range of 14–18 million years and distance range of 380–460 ly (115–141 pc).[3]: 5-6  Given V1400 Centauri's similar distance and proper motion, it very likely belongs to the Scorpius–Centaurus association, which would mean it must be a young star within the age range of the Upper Centaurus–Lupus subgroup.[3]: 5-6  A 2012 estimate of V1400 Centauri's age assumes it is equal to 16 million years,[3]: 6  the mean age of the Upper Centaurus–Lupus subgroup, while a 2018 estimate from Gaia measurements puts the star's age at 21.38+4.30
−7.60 million years.[6]: 2 

Spectral type and physical characteristics

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V1400 Centauri is a pre-main sequence star of spectral class K5 IVe Li.[4][3]: 5  "K" means V1400 Centauri is an orange K-type star, and the adjoining number "5" ranks V1400 Centauri's relative temperature on a scale of 9 (coolest) to 0 (hottest) for K-type stars. V1400 Centauri is given the subgiant luminosity class "IV", because it has a brighter luminosity than K-type main-sequence stars (luminosity class V).[3]: 5 [d] The letter "e" indicates V1400 Centauri exhibits weak hydrogen-alpha emission lines in its visible light spectrum.[3]: 5  Lastly, "Li" indicates V1400 Centauri is abundant in lithium.[3]: 5 

Measurements from the Gaia spacecraft's third and most recent data release (Gaia DR3) indicate V1400 Centauri is about 7% larger than the Sun in radius (1.07 R☉; 740,000 km; 460,000 mi),[7] but is slightly less massive than the Sun.[5][6]: 2  Depending on whether magnetic effects are taken into account in V1400 Centauri's stellar evolution or not, the star's mass could be either 0.98 M☉ or 0.89 M☉, respectively.[5]: 4  Young stars tend to be magnetically active,[16] and neglecting their magnetic effects results in an underestimation of their mass.[5]: 4, 9  An older estimate of V1400 Centauri's mass from Gaia's second data release (Gaia DR2) in 2018 gives 0.95 M☉, but does not take magnetic effects into account.[6]: 2 

V1400 Centauri is cooler and less luminous than the Sun, with an effective temperature of about 4,300 K (4,030 °C; 7,280 °F) and a luminosity about 34% that of the Sun.[7] V1400 Centauri has an estimated surface gravity of about 200 m/s2 (over 20 times the gravity of Earth), based on Gaia measurements of the star's brightness, distance, and color.[1][e] Gaia measurements also indicate V1400 Centauri has a lower metallicity than the Sun.[1][f] Viewed from Earth, V1400 Centauri appears marginally redder than a typical K5-type star due to light extinction by interstellar dust between Earth and the star.[g] The star does not exhibit excess thermal emission in near- and mid-infrared wavelengths and lacks strong emission lines in its spectrum, which indicates it lacks a substantial accretion disk.[3]: 10 

Rotation and variability

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Like most young stars, V1400 Centauri rotates rapidly with a rotation period of approximately 3.2 days.[3]: 8  The rapid rotation of V1400 Centauri strengthens its magnetic field via the dynamo process, which leads to the formation of starspots on its surface.[8]: 6  As V1400 Centauri rotates, its starspots come into and out of view, causing the star's brightness to periodically fluctuate by 5%, or about 0.1 magnitudes in amplitude.[8]: 2  The star's rotation period varies by 0.02 days over a 5.4-year-long magnetic activity cycle, due to the long-term movement of starspots across the star's differentially rotating surface.[8]: 6 [17]: 2847  V1400 Centauri is known to emit soft X-rays[3]: 8  due to its corona being heated by its rotationally-strengthened magnetic field.[18]

Spectroscopic measurements of Doppler broadening in V1400 Centauri's spectral absorption lines indicate the star has a projected rotational velocity of 14.6±0.4 km/s.[9]: 415–416  Given V1400 Centauri's rotation period, radius, and temperature, the star's true equatorial rotation velocity is 15.7±1.7 km/s,[9]: 418  which indicates that the star's rotation axis is inclined 68°±10° with respect to Earth's line of sight.[9]: 419 

Because of its young age, starspot variability, and lack of dust accretion, V1400 Centauri is classified as a weak-lined T Tauri variable.[9]: 412 [2] The star underwent a series of deep eclipse-like dimmings in 2007, which have been ascribed to the coincidental transit of J1407b's circumplanetary disk.[12] The star shows no signs of periodic dimming caused by transiting planets larger than Jupiter.[8]

2007 eclipse by J1407b

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Visual-band light curve of V1400 Centauri, showing the 2007 eclipse. The main plot shows the SuperWASP data.[19] The inset plot, adapted from Mamajek et al.,[3] shows the data near mid-eclipse. The purple markers show the pairs of small brightness dips due to eclipses by rings.
Artist's impression of a circumstellar disk eclipsing a star, similar to J1407b's eclipse of V1400 Centauri in 2007

During April–May 2007, telescopes of the Super Wide Angle Search for Planets (SuperWASP) and All Sky Automated Survey (ASAS) projects recorded V1400 Centauri undergoing a series of significant dimming events, each lasting several days.[8] The pattern of these dimming events was complex yet nearly symmetrical, indicating they were caused by an opaque, disk-like structure eclipsing V1400 Centauri. The light curve of V1400 Centauri during 2007 showed at least five major dimming events, including a very long and deep central eclipse bracketed by two pairs of shorter eclipses symmetrically occurring 12 days and 26 days before and after the deep eclipse midpoint.[3] The deep eclipse lasted about 14 days (7 days from midpoint) and blocked out at least 95% of V1400 Centauri's light, causing it to dim by at least 3.3 magnitudes.[3] The short eclipses before and after the deep eclipse were shallower and blocked out at least 60% of the star's light, causing it to dim by at least 1 magnitude.[3][17]

A team of astronomers led by Eric E. Mamajek discovered the 2007 eclipse of V1400 Centauri while they were investigating SuperWASP's photometric data. Mamajek's team originally intended to use the SuperWASP data to validate candidate low-mass stars of the Scorpius–Centaurus association, which they had been studying since 2009.[3] Mamajek's team presented their discovery of V1400 Centauri's eclipse in January 2012 at the 219th American Astronomical Society conference in Austin, Texas,[20][21] and then formally published their results in The Astronomical Journal in March 2012.[3]

Unsuccessful searches for companions around V1400 Centauri suggest that the object that eclipsed the star must be substellar in mass (below 80 Jupiter masses), which means it could either be a brown dwarf or a planetary-mass object.[9] Mamajek's team hypothesized that this substellar object could either be orbiting V1400 Centauri as an exoplanet or binary companion, or is a gravitationally unbound, free-floating object that coincidentally passed in front of the star. The substellar object was first dubbed "J1407b" in a paper published by Tim van Werkhoven, Matthew Kenworthy, and Eric Mamajek in 2014: they assumed the object was orbiting V1400 Centauri as a planet, hence they followed the exoplanet naming convention by adding the letter "b" after the star's name (known as J1407 at the time).[17]

Disk properties

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J1407b's disk may be considered a circumplanetary disk[3]: 9 [11] or a massive ring system.[22][12] The rate of V1400 Centauri's dimming during J1407b's eclipses indicates that J1407b and its disk were moving at a transverse velocity of 35 km/s (22 mi/s) relative to the star,[12]: 5  which corresponds to a radius of 0.6 astronomical units (90 million km; 56 million mi) between J1407b and its disk's outer edge.[17]: 2850  To compare, the radius of J1407b's disk is roughly 200 times larger than that of Saturn's E Ring,[h] and lies between the orbital radii of Mercury (0.39 AU) and Venus (0.72 AU).[24] J1407b's circumplanetary disk or ring system has been frequently compared to that of Saturn's, which has led popular media outlets to dub it a "Super Saturn"[25][26] or a "Saturn on steroids".[21][27]

The radius of the disk extends far beyond J1407b's Roche limit at 0.001 AU (150 thousand km; 93 thousand mi), which allows exomoons (or exoplanets if J1407b is a brown dwarf) to form within the disk as evidenced by gaps seen in J1407b's disk.[28]: 1682  J1407b's disk is tilted by 13° relative to the plane of J1407b's path and Earth's line of sight, which explains its nearly-symmetrical eclipse light curve and differing time durations between eclipse ingress and egress.[3]: 12 [17]: 2846  Variations in V1400 Centauri's dimming rate during the eclipses suggest that J1407b's disk has a height-to-radius ratio of approximately 0.0015, which corresponds to a vertical disk thickness of 0.0009 AU (130 thousand km; 84 thousand mi).[17]: 2850 [i]

The varying depths of J1407b's eclipses indicate its disk consists of various concentric rings and gaps of different opacities. A 2015 analysis of J1407b's eclipse light curve by Kenworthy and Mamajek found that J1407b's disk comprises at least 37 distinct rings with radii from 0.2 to 0.6 AU (30 to 90 million km; 19 to 56 million mi).[11]: 1, 5 [8]: 1  Assuming the rings have a mass density proportional to their opacity, the total mass of J1407b's disk is roughly 100 lunar masses (1.23 Earth masses).[11]: 9 [28]: 1686  J1407b's disk contains a 4-million km (2.5-million mi)-wide gap between radii 0.39 to 0.42 AU (58 to 63 million km; 36 to 39 million mi), which is believed to have have been created by a nearly-Earth-sized (<0.8 M🜨) exomoon orbiting within that gap and clearing out material, in a similar fashion to the shepherd moons of Saturn's rings.[11]: 7 [28]: 1682  Other possible mechanisms for creating J1407b's disk gaps, such as orbital resonances between multiple exomoons, are deemed unlikely because they cannot produce the observed structure of J1407b's disk.[28]: 1684  Altogether, the presence of rings and gaps outside J1407b's Roche limit combined with evidence of a possible exomoon suggests that J1407b's disk is currently in the process of accreting into more exomoons, and will eventually become a satellite system in less than a few billion years.[11]: 9 [28]: 1682 

Bound companion hypothesis

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Mamajek's team initially considered the bound companion hypothesis plausible because V1400 Centauri is young enough that a protoplanetary disk could exist around the star and its putative companion, and there are known eclipsing binary stars where one component is surrounded by a circumstellar disk (for example Epsilon Aurigae).[3]: 8  Although it is now considered obsolete, the hypothesis of J1407b being a substellar companion or exoplanet orbiting V1400 Centauri was popularized by Mamajek and Kenworthy in 2015, when they announced their research on J1407b in a press release published by their respective universities.[29][30]

Proposed orbit

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Diagram of the hypothesized V1400 Centauri planetary system, with J1407's supposed planetary rings shown to scale. The range of possible elliptical orbits for J1407b is shown in red.

Following the assumption that J1407b is a companion orbiting V1400 Centauri, its transverse speed of 35 km/s (22 mi/s) during the 2007 eclipse would be the same as its orbital speed around the star. This orbital speed suggests a range of possible orbits depending on J1407b's orbital eccentricity: if J1407b has a circular orbit with a constant orbital speed, then it would have an orbital period around 200 days, whereas if J1407b's orbit is more eccentric with a varying orbital speed, then it could have longer orbital periods of up to several years.[3]: 8 

Continuous observations of V1400 Centauri's brightness after 2007 did not show any signs of eclipse-like dimming, which rules out the possibility of near-circular and short-period orbits for J1407b.[11]: 9  A more extensive analysis of V1400 Centauri's brightness in archival observations from 1890–1990 similarly found no signs of eclipses, ruling out 90% of all possible orbital periods between 10–20 years for J1407b.[6]: 6–7  Although these observations do not rule out the possibility of orbital periods longer than 25 years, such long orbital periods are considered unlikely because they require an extremely eccentric orbit for J1407b, which would destabilize J1407b's disk.[6]: 6–7  Overall, these constraints suggest a probable orbital period range of 14–17 years (with the most probable orbital periods around 16.5–17 years) if J1407b orbits V1400 Centauri.[6]: 6  For this orbital period range, J1407b's orbital eccentricity must be between 0.72–0.78.[6]: 7 

The V1400 Centauri planetary system[17]: 2846 [22]: 1 [6]: 6–7 
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b (disputed) 5–20 MJ[6]: 7 
or 20–80[9][22] MJ 		>5.0±0.1 AU
(for >11 yr orbital period)[22]: 1  		14–17 yr
(5110–6200 d)[6]: 6–7  		0.72–0.78
[6]: 7  		89.995° —

Problems with the hypothesis

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A 2016 study by Steven Rieder and Matthew Kenworthy investigated the orbital dynamics of J1407b's postulated eccentric orbit and found that the disk of J1407b either fills a large fraction of or extends beyond J1407b's Hill radius (extent of J1407b's gravitational influence against V1400 Centauri) regardless of its mass, which meant that J1407b's disk could be easily destabilized by V1400 Centauri's gravitational influence whenever it makes its closest approach to the star at periapsis.[22]: 2 

To remedy the issue with J1407b's disk stability in an eccentric orbit, Rieder and Kenworthy proposed that J1407b's disk must orbit J1407b in retrograde motion, opposite to the direction J1407b orbits its host star.[22]: 3–4  A retrograde-orbiting disk would survive longer against V1400 Centauri's gravitational influence, although it would still slowly shrink over timescales of 10,000 years.[22]: 4  Rieder and Kenworthy suggested that the lifetime of a retrograde-orbiting disk could be prolonged by dust-producing processes such as tidal disruption of comets around J1407b.[22]: 4  However, if J1407b is a companion that formed in orbit around V1400 Centauri, then its disk is expected to be prograde, orbiting J1407b in the same direction as its supposed orbit around the star. The origin of a retrograde-orbiting disk together with J1407b's postulated eccentric orbit could not be easily explained by current theories for planetary formation,[22]: 5  which would make J1407b a very unusual object if it is still stably orbiting V1400 Centauri.[6]: 7 

One hypothesis to explain J1407b's supposed eccentric orbit proposes that V1400 Centauri could have another undetected substellar companion that is orbiting beyond J1407b and gravitationally perturbing its orbit.[8]: 2  However, the existence of additional substellar companions beyond the distance of J1407b's supposed orbit had already been shown to be unlikely by Mamajek's team, who attempted a search for J1407b using various telescopes during 2012–2013.[9]: 412  High-resolution imaging of V1400 Centauri using Mauna Kea Observatory's Keck telescopes and European Southern Observatory's Very Large Telescopes found no signs of J1407b or any brown dwarf-mass companions within a few AU from the star.[9]: 414–415  Doppler spectroscopy of V1400 Centauri using Las Campanas Observatory's Magellan–Clay Telescope and La Silla Observatory's Euler Telescope showed no evidence of radial velocity variations that would be caused by a >12 MJ companion orbiting the star.[9]: 422  Furthermore, continuous observations of V1400 Centauri's brightness over a 19-year timespan between 2001–2020 found no evidence of transits by Jupiter-sized exoplanets or substellar companions before and after J1407b's 2007 eclipse.[8]: 2  Overall, the lack of recurring eclipses, non-detections of orbiting companions, and complications in explaining J1407b's eccentric orbit and disk stability suggest that J1407b is more likely a free-floating object than a companion orbiting V1400 Centauri.[6]: 1 [12]: 2 

Unbound object hypothesis

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ALMA radio image of V1400 Centauri and the nearby faint object, which might be J1407b
Artist's impression of OTS 44, a young brown dwarf surrounded by a dusty circumplanetary disk. J1407b most likely resembles this if it is a free-floating young substellar object.

Mamajek's team initially rejected the idea that J1407b is a free-floating object because they considered it extremely unlikely for a small, unbound object to coincidentally eclipse a star.[11]: 9  Their reasoning was that stars and other interstellar objects are typically separated extremely far apart from each other (~1,000 AU), so the probability of two unbound objects overlapping each other in position is extremely small.[b] They further argued that the existence of J1407b's massive disk implies that the object must be considerably younger than the stars surrounding its location.[11]: 9  However, they eventually reconsidered their stance on J1407b's nature as they uncovered issues with the bound companion hypothesis.[6][12]

High-resolution imaging of V1400 Centauri in millimeter radio frequencies by the Atacama Large Millimeter Array (ALMA) in 2017 found no evidence of a bound companion >4 MJ in mass, but did detect a faint, nearby object 438±8 milliarcseconds away from V1400 Centauri's observed position. At V1400 Centauri's distance from Earth, this angular separation corresponds to a projected distance of 61 AU, which is too far away for this object to be orbiting the star.[12]: 4  This observed angular separation is consistent with the expected distance (543±82 mas) travelled by an unbound object moving at J1407b's transverse velocity of 35 km/s (22 mi/s) during 2007–2017, which makes it possible that this faint object could be J1407b. Furthermore, the brightness of this faint object is consistent with a <6 MJ substellar object surrounded by a disk of warm dust.[12]: 1 

While the properties of the faint object strongly suggest that it is J1407b, it has only been observed once so it is not yet confirmed whether this faint object is moving, let alone in the right direction and speed. It is possible that this faint object could be a stationary background galaxy or a spurious detection caused by image noise, although these two possibilities are considered unlikely.[12]: 5  ALMA reobserved V1400 Centauri in June and July 2024, which will provide confirmation of the faint object's nature once the data is analyzed and published.[31]

See also

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Notes

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  1. ^ 3.206±0.002 d is the median rotation period of V1400 Centauri throughout its 5.4-year magnetic activity cycle.[8]: 6 
  2. ^ a b To further elaborate on the probability of J1407b's 0.6 AU-radius disk overlapping a star, consider a circular 2D area of empty space 1,000 AU in radius (the average projected separation distance between stars).[11]: 9  In the center of this 2D area lies a single star, whose radius (0.0047 AU or 1 R☉ for a Sun-like star) is negligible compared to that of the surrounding empty space.
    To calculate the probability of J1407b's disk overlapping that star, take the ratio of J1407b's projected disk area over the empty space area. Note that since J1407b's disk is tilted 13° with respect to Earth's line of sight, it takes up less area than a 0.6 AU-radius circle. By treating J1407b's tilted disk as an ellipse, its projected area is AJ1407b = π(0.6 AU)2sin(13°) ≈ 0.25 AU2. On the other hand, the total area of empty space around the star is Aspace = π(1,000 AU)2 ≈ 3.1×106 AU2.
    Taking the ratio of areas AJ1407b / Aspace gives 8.1×10−8 (1 in 810 million) as the probability of J1407b's disk overlapping a star. Note that this calculation does not take into account the probability of J1407b being in front or behind the overlapping star, so the actual probability of J1407b eclipsing the star by being in front of it is lower. For additional context, see Orders of magnitude (probability).
  3. ^ Proper motion is split into right ascension (RA) and declination (Dec) components. By convention, positive RA is eastward and positive Dec is northward in the equatorial coordinate system. The measured proper motion components of V1400 Centauri are −23.108±0.015 mas/yr and −21.048±0.017 mas/yr in RA and Dec, respectively.[1] Since both RA and Dec components of V1400 Centauri's proper motion are negative, its proper motion is pointed towards the west and south directions, hence southwest.
  4. ^ The term "subgiant" and its associated luminosity class "IV" can either refer to the life stage between the main-sequence and giant phases near the end of a star's life, or it can strictly refer to a star's luminosity only. In the case of V1400 Centauri, the latter definition is used since it is appropriate for the star's young age.
  5. ^ The Gaia DR3 table gives log g = 4.302 as the base 10 logarithm of surface gravity in cgs units.[1] Raising 10 to the power of log g gives the star's surface gravity g in cgs units of cm/s2. Converting the result to the SI acceleration units of m/s2 gives g ≈ 200.4 m/s2 for V1400 Centauri's surface gravity.
  6. ^ The Gaia DR3 table gives the [Fe/H] metallicity (iron abundance relative to the Sun) as a base 10 logarithmic quantity. V1400 Centauri has a negative [Fe/H] metallicity of –0.1903, which indicates a lower iron abundance than the Sun.[1]
  7. ^ The latest estimate for V1400 Centauri's extinction reddening index is E(GBP–GRP) = 0.0414+0.0518
    −0.0314     mag, from Gaia DR3 (2022).[7] Mamajek et al. (2012) claimed V1400 Centauri is consistent with being slightly reddened,[3]: 5  whereas van Werkhoven et al. (2014) claimed it is statistically consistent with being unreddened.[17]: 2848 
  8. ^ The outer edge of Saturn's E Ring is approximately 480,000 km (300,000 mi) in radius from Saturn.[23] For J1407b, the outer edge of its circumplanetary disk is 90 million km (56 million mi) in radius,[11] which is approximately 188 times that of Saturn's E Ring.
  9. ^ Multiplying J1407b's disk radius (r = 0.6*nbsp;AU by the height-to-radius ratio h/r = 0.0015 gives h = 0.0009 AU for height.

References

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  1. ^ a b c d e f g h i j Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c "V1400 Cen". International Variable Star Index. AAVSO. Archived from the original on 1 August 2023. Retrieved 1 August 2023.
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