![]() A light curve for V377 Geminorum, plotted from TESS data, [1] with the 6.46 day rotation period shown in red, | |
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Gemini [a] |
Right ascension | 07h 49m 55.05s [2] |
Declination | 27° 21′ 47.45″ [2] |
Apparent magnitude (V) | 6.92 [3] |
Characteristics | |
Evolutionary stage | Main sequence [4] |
Spectral type | G5V [4] |
Variable type | BY Draconis [5] [6] |
Astrometry | |
Radial velocity (Rv) | −16.07±0.13 [3] km/s |
Proper motion (μ) | RA: −10.0268±0.0846 mas/yr [3] Dec.: −11.3143±0.0487 mas/yr [3] |
Parallax (π) | 44.6848 mas [7] |
Distance | 73.035±0.073 ly (22.4035±0.0225 pc) [3] |
Absolute magnitude (MV) | 5.19 [8] |
Details [9] | |
Mass | 0.99±0.03 M☉ |
Radius | 0.912±0.034 R☉ |
Luminosity | 0.753±0.026 L☉ |
Surface gravity (log g) | 4.52±0.05 [4] cgs |
Temperature | 5640±74 K |
Metallicity [Fe/H] | 0.03±0.05 [4] dex |
Rotation | 6.45±0.05 d |
Rotational velocity (v sin i) | 7.3±0.3 km/s |
Age | 414±23 Myr |
Other designations | |
Database references | |
SIMBAD | data |
HD 63433 (TOI-1726, V377 Geminorum) is a G-type main sequence star located 73 light-years from Earth in the zodiacal constellation Gemini, [9] [a] visually close to the star Pollux. [7] It has nearly the same radius and mass of the Sun, hence being classified as a Sun-like star. [9] However, it is much younger than the Sun, less than one tenth as old with an age of about 400 million years. [9] [b] With an apparent magnitude of 6.9, it is not visible to the naked eye, but can be seen with a small telescope [11] or binoculars. [12] Based on its kinematic, rotational and lithium abundance properties, it is part of the Ursa Major Moving Group. [9] There are three exoplanets orbiting it, one is classified as an Earth-sized planet, while the two others are mini-Neptunes. [4]
HD 63433 is a G-type main sequence star with a radius of 0.912 R☉ , a mass of 0.99 M☉ , an effective temperature of 5640 K and a spectral type G5V. [9] Its properties are quite similar to those of the Sun, which has a spectral type G2V and a temperature of 5772 K. [13] Therefore, it is classified as a solar analog. [9] HD 63433, however, is much younger than the Sun, having an age of 414 million years, [9] just 9% of the solar age of 4.6 billion years. [10] It has a surface gravity of 33.8 g [c] and a rotational period of 6.45 days, [9] which is 3.8 times faster than the Sun.
With an apparent magnitude of 6.92m, [3] it is below the limit for naked-eye visibility, generally defined as 6.5m, [14] which would mean that this star is not visible to the naked eye, but easily visible using a small telescope [11] or binoculars. [15] [12] Despite being faint, HD 63433 is actually the third-brightest star with transiting exoplanets confirmed by the Transiting Exoplanet Survey Satellite, with only Pi Mensae (5.65m) [16] and HR 858 (6.38m) [17] being brighter. [9] [18]
According to stellar kinematics, lithium abundance and stellar rotation, HD 63433 is part of the Ursa Major moving group. [9] It was initially identified as a possible member of this group by Gaidos (1998) [19] and included as a possible member in later analyses, until HD 63433's membership in this moving group was finally confirmed by Mann et al. in 2020. [9] As it is part of this moving group, its age is estimated at 414 ± 23 million years, the same as the group. [9]
It is located in the northern hemisphere, about 73 light-years from the Earth, in the constellation of Gemini. [11] It is visually close to Pollux, the brightest star in the constellation. [7] HD 63433 is predicted to approach within 7.33 light-years of the Sun in 1.33 million years. [20] That will make it one of the nearest stars to the Sun. Its closest neighbor is the orange dwarf HD 63991, located at a distance of 2.7 light years. [11]
Name | Distance (light-years) |
---|---|
HD 63991 | 2.7 |
LSPM J0801+2342 | 6.1 |
HD 68017 | 9 |
BD+31 1781 | 9.1 |
G 90-52 | 9.2 |
HD 63433 belongs to the class of BY Draconis variables, [5] [6] stars have variations in their luminosity due to their rotation together with sunspots and other chromospheric activities. The brightness of the star varies by 0.05 magnitudes over a period of 6.46 days. [6]
It was found to be variable by Gaidos et al. in 2000. [21] The star was given the variable-star designation V377 Geminorum in 2006. [22]
The star HD 63433 is orbited by 3 exoplanets, all discovered by the transit method.
The first ones to be discovered, HD 63433 b and HD 63433 c, are mini-Neptunes [23] that were discovered in by Mann et al. in 2020 using the Transiting Exoplanet Survey Satellite. [24] In 2024, an additional planet was discovered, after an analysis of a transit signal detected by TESS. Named HD 63433 d, it is an Earth-sized planet. [25]
According to theoretical models, the compositions of the mini-Neptunes HD 63433 b and c are mostly silicate and water, with no iron dominance, surrounded by a gaseous envelope which, in the case of planet c, makes up around 2% of the planet. [23]
The planetary system of HD 63433 is quite young, at around 400 million years old, it is only 9.13% as old as the Solar System. [4] [25] [d] HD 63433 d is also the smallest planet that is less than 500 million years old.
Temperature comparisons | HD 63433 b [23] | HD 63433 c [23] | HD 63433 d [4] |
Global equilibrium temperature | 769 – 967 K 496 – 694 °C 925 – 1281 °F | 540 – 679 K 267 – 406 °C 513 – 763 °F | 1040 K 767 °C 1413 °F |
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
d | — | 0.0503±0.0027 | 4.21 | 0.16+0.36 −0.12 | 88.73±1 ° | 1.073+0.046 −0.044 R🜨 |
b | <21.76 M🜨 | 0.0719+0.0044 −0.0031 | 7.11 | 0.24+0.27 −0.18 | — | 2.14+0.087 −0.069 R🜨 |
c | 15.54±3.86 M🜨 | 0.1458±0.015 | 20.55 | 0.161+0.014 −0.013 | — | 2.692+0.108 −0.088 R🜨 |
The middle planet, HD 63433 b, is a mini-Neptune planet that was discovered together with HD 63433 c. [4] HD 63433 b is 2.14 times larger than Earth, [23] but is about 45% smaller than Neptune. [e] The planet has an upper mass limit of 21.7 M🜨 , [23] which is 21% greater than the mass of Neptune (17.15 M🜨 [26] ). These values calculate an upper density limit of 13 g/cm3, [23] 2 times greater than that of Earth, [f] and similar to that of the chemical element Mercury. HD 63433 b orbits its parent star at a distance of 0.0719 astronomical units (10,760,000 km) – about 5 times closer than Mercury is to the Sun – and completes one revolution every 7 days and 3 hours. The relative proximity of its star makes it hot, with an equilibrium temperature between 769 and 967 Kelvin (496 and 694 °C). [23] [g]
HD 63433 b was probably a mini-Neptune that later lost its atmosphere. [28] Some factors, such as the fact that no absorption of Ly-α was detected during its transit, and its mass-loss timescale being shorter than the age of the planetary system, indicate that it has already lost its primordial atmosphere, and could be a rocky planetary core. [28] However, if HD 63433 b were a rocky core, it would need to be unusually massive and, therefore, a water-rich composition in addition to an atmosphere with a high mean molecular weight could explain both the radius and the non-detection of the Ly-α. [28]
The outermost planet, HD 63433 c, is a mini-Neptune planet discovered together with HD 63433 b. [9] It is 2.7 times larger than Earth, [23] but 30% smaller than the Solar System's ice giants, Neptune and Uranus. Being 15.5 times more massive than the Earth, [23] it is more massive than Uranus (14.54 M🜨 ), but still less massive than Neptune (17.15 M🜨 ). The density of HD 63433 c calculated at 4.6 g/cm3, slightly lower than that of Earth, [23] but greater than the densities of all gas giants in the Solar System.
Orbiting its star at a distance of 0.145 astronomical units (21,700,000 km) in an orbital period of 20 days, [23] it is the outermost planet in its planetary system, but still close to its star, making it a warm planet, with a planetary equilibrium temperature estimated between 267 and 406 °C. [23] [h]
Due to the high radiation received from its star, the atmosphere of HD 63433 c, made up of hydrogen, is slowly being stripped away and escaping from the planet, like a hot air balloon. [29] The hot gas escapes into the space at a velocity of 50 km/s, forming a gas cocoon 12 times larger than the planet itself. [29] As its atmosphere evaporates, HD 63433 c will slowly become a super-Earth planet. [29]
HD 63433 d was the last planet to be discovered in the system, 4 years after planets b and c. [4] With a diameter of ~13,690 km, it is very similar to Earth in size, being only 7% larger, but its mass is currently unknown. [4] It is the innermost planet orbiting HD 63433, having a semi-major axis (mean distance from its star) of 0.0503 astronomical units (7,520,000 km) and an orbital period of just 4 days. [4] The extreme proximity to its star makes it extremely hot, having a daytime temperature estimated at 1,260 °C (2,300 °F), [4] [i] hot enough to melt all the minerals present on its surface, [30] as well as being tidally locked, meaning that one half of the planet is always facing towards its star, while the other is always facing away from it. [31] [25] The planet also possibly lacks a substantial atmosphere. [4] [25] [30]
It is believed that the dayside of the planet, always facing its star due to tidal locking, is fully composed of lava due to the high surface temperature, [32] [25] in addition to possibly having volcanic activity. [33] [34] Meanwhile, the nightside of the planet, which never faces its star, may be the opposite, resembling Pluto with glaciers of frozen nitrogen. [35]
HD 63433 d was discovered in 2024, through an analysis of a transit observation made by the Transiting Exoplanet Survey Satellite (TESS). [25] As two other planets had already been discovered in the system, the transit signals of these objects were removed, thus revealing an additional transit signal that reappeared every 4.2 days. [25] [36] [4] Further investigation allowed researchers to confirm that this signal was from another orbiting exoplanet, now called HD 63433 d. [25] The discovery was announced on January 10, 2024, in The Astronomical Journal. [31] [35]
The HD 63433 planetary system plays an important role in understanding the evolution of planetary systems in the first billion years after formation. [9] [4] As HD 63433 is relatively bright (6.9 m ) and close (73 ly away), its planets b and c can have their atmospheres characterized by the Hubble Space Telescope and James Webb Space Telescope. [28] This star is also a favorable target for studies of atmospheric mass loss in exoplanets, as it is a young and active star with close-in mini-Neptune planets, in addition to having a negative radial velocity (−16.07 km/s ). [28]
HD 219134 is a main-sequence star in the constellation of Cassiopeia. It is smaller and less luminous than the Sun, with a spectral class of K3V, which makes it an orange-hued star. HD 219134 is relatively close to our system, with an estimated distance of 21.34 light years. This star is close to the limit of apparent magnitude that can still be seen by the unaided eye. The limit is considered to be magnitude 6 for most observers. This star has a magnitude 9.4 optical companion at an angular separation of 106.6 arcseconds.
55 Cancri e is an exoplanet orbiting a Sun-like host star, 55 Cancri A. The mass of the exoplanet is about eight Earth masses and its diameter is about twice that of the Earth. 55 Cancri e was discovered on 30 August 2004, thus making it the first super-Earth discovered around a main sequence star, predating Gliese 876 d by a year. It is the innermost planet in its planetary system, taking less than 18 hours to complete an orbit. However, until the 2010 observations and recalculations, this planet had been thought to take about 2.8 days to orbit the star.
HD 69830 d is an exoplanet likely orbiting within the habitable zone of the star HD 69830, the outermost of three such planets discovered in the system. It is located approximately 40.7 light-years (12.49 parsecs, or 3.8505×1014 km) from Earth in the constellation of Puppis. The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star.
A Super-Earth or super-terran or super-tellurian is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term.
Kepler-4b, initially known as KOI 7.01, is an extrasolar planet first detected as a transit by the Kepler spacecraft. Its radius and mass are similar to that of Neptune; however, due to its proximity to its host star, it is substantially hotter than any planet in the Solar System. The planet's discovery was announced on January 4, 2010, in Washington, D.C., along with four other planets that were initially detected by the Kepler spacecraft and subsequently confirmed by telescopes at the W.M. Keck Observatory.
HD 10180, also designated 2MASS J01375356-6030414, is a Sun-like star in the southern constellation Hydrus that is notable for its large planetary system. Since its discovery, at least six exoplanets have been observed orbiting it, and some studies have proposed up to nine potential planets, which would make it potentially the largest of all known planetary systems, including the Solar System.
An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems, with 1007 systems having more than one planet. This is a list of the most notable discoveries.
Kepler-11, also designated as 2MASS J19482762+4154328, is a Sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,110 light years from Earth. It is located within the field of vision of the Kepler space telescope, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars. Announced on February 2, 2011, the star system is among the most compact and flattest systems yet discovered. It is the first discovered case of a star system with six transiting planets. All discovered planets are larger than Earth, with the larger ones being about Neptune's size.
Kepler-90, also designated 2MASS J18574403+4918185, is a F-type star located about 2,790 light-years (855 pc) from Earth in the constellation of Draco. It is notable for possessing a planetary system that has the same number of observed planets as the Solar System.
K2-33b is a very young super-Neptune exoplanet, orbiting the pre-main-sequence star K2-33. It was discovered by NASA's Kepler space telescope on its "Second Light" mission. It is located about 453 light-years away from Earth in the constellation of Scorpius. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured.
HD 3167 is a single, orange-hued star in the zodiac constellation of Pisces that hosts a system with three exoplanets. The star is too faint to be seen with the naked eye, having an apparent visual magnitude of 8.97. The distance to HD 3167 can be determined from its annual parallax shift of 21.1363 mas as measured by the Gaia space observatory, yielding a range of 154 light years. It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.204″ per year. Since it was first photographed during the Palomar observatory sky survey in 1953, it had moved over 12.5″ by 2017. The star is moving away from the Earth with an average heliocentric radial velocity of +19.5 km/s.
GJ 3929 b is a confirmed exoplanet located 52 light-years away orbiting the red dwarf star GJ 3929. It is an Earth-sized planet, having a radius only 9% larger than that of Earth. It orbits its star at a distance of 0.0252 astronomical units (3,770,000 km), being located in the Venus zone of its star, and completes one orbit around it every 2 days and 15 hours. Because of the proximity of its star, and its low mass, GJ 3929 b is classified as a Venus-like planet, having an equilibrium temperature of around 300 °C and receiving planetary insolation 17 times more intense than Earth receives from the Sun.
HD 63433 d is a confirmed exoplanet orbiting HD 63433, a Sun-like star located 73 light-years away in the constellation Gemini. Its radius is measured at around 1.1 R🜨, which makes it similar to the Earth in size. It was the third exoplanet to be discovered in orbit around this star; the other two, HD 63433 b and c, were discovered in 2020. Orbiting its star at a distance of 0.0503 astronomical units (7,520,000 km), HD 63433 d is the innermost planet orbiting HD 63433, and completes an orbit around it just every 4 days. Due to the proximity of its star, the planet is scorching hot, having a temperature estimated at 1260 °C at daytime. The proximity of its star also causes it to be tidally locked.
HD 63433 c is a mini-Neptune exoplanet orbiting the Sun-like star HD 63433. It is the outermost planet in its planetary system, being located 0.1448 astronomical units (21,660,000 km) from its star, and completing one orbit every 21 days. Despite being the outermost planet in the system, it is still located close to its star, meaning that its temperature is hot, being estimated between 267 and 406 °C. HD 63433 c is about 2.7 times larger than Earth and 15.5 times more massive, but still smaller and less massive than Neptune. In 2022, a study showed that its atmosphere, made up of hydrogen, is being evaporated by the strong radiation from its star, causing it to slowly turn into a super-Earth planet.
HD 15337 (TOI-402) is a star with two orbiting exoplanets in the southern constellation of Fornax. It has an apparent magnitude of 9.09, making it too faint to be observed by the naked eye from Earth, but readily visible using a small telescope. It is located 146 light-years distant based on stellar parallax, and is currently heading towards the Solar System with a radial velocity of −3.9 km/s.
HD 73344 is a star located in the constellation Cancer. It has a faint apparent magnitude of 6.9 and therefore can't be seen by the naked eye. It is located 35.2 parsecs away based on parallax measurements. This star hosts three confirmed exoplanets.