This image from the NASA/ESA Hubble Space Telescope shows a visible light view of the outer dust around the young star HD 100546, with the newly discovered protoplanet positioned and marked by an orange spot. Artifacts from the brilliant central star dominate the inner part of this picture, which has been digitally subtracted. Black blobs are also artifacts. [1] [2] | |
Observation data Epoch J2000.0 [3] Equinox J2000.0 [3] | |
---|---|
Constellation | Musca |
Right ascension | 11h 33m 25.441s [4] |
Declination | −70° 11′ 41.24″ [4] |
Apparent magnitude (V) | 6.68 –6.87 [5] |
Characteristics | |
Evolutionary stage | Herbig Ae/Be star [6] |
Spectral type | kB8 –A0Vae [7] [3] |
Apparent magnitude (B) | 6.71±0.01 [8] |
Apparent magnitude (V) | 6.30 [9] |
Apparent magnitude (G) | 6.686±0.003 [4] |
Apparent magnitude (I) | 6.64±0.05 [1] |
Apparent magnitude (J) | 6.425±0.020 [10] |
Apparent magnitude (H) | 5.96±0.03 [10] |
Apparent magnitude (K) | 5.418±0.023 [10] |
Astrometry | |
Radial velocity (Rv) | 9.10±1.2 [11] km/s |
Proper motion (μ) | RA: −38.730(46) mas/yr [4] Dec.: −0.097(39) mas/yr [4] |
Parallax (π) | 9.2494 ± 0.0375 mas [4] |
Distance | 353 ± 1 ly (108.1 ± 0.4 pc) |
Details | |
Mass | 2.18+0.02 −0.17 [12] M☉ |
Radius | 1.5±0.1 [13] R☉ |
Luminosity | 19.5+7.42 −5.37 [lower-alpha 1] [13] L☉ |
Surface gravity (log g) | –4.0 [14] [ dubious – discuss ] cgs |
Temperature | 9,800 [14] K |
Metallicity [Fe/H] | –1.0 [7] ––1.4±0.2 [15] dex |
Age | 4.8+2.0 −1.1 [14] Myr |
Other designations | |
Database references | |
SIMBAD | data |
HD 100546, also known as KR Muscae, is a pre-main sequence star of spectral type B8 to A0 located 353 light-years (108 parsecs ) from Earth in the southern constellation of Musca. [4] The star is surrounded by a circumstellar disk from a distance of 0.2 to 4 AU, and again from 13 AU out to a few hundred AU, with evidence for a protoplanet forming at a distance of around 47 AU. [16]
Estimated to be less than 10 million years old, it belongs to Herbig Ae/Be stars, and also the nearest example to the Solar System. [14] [17]
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
Inner disk | 0.2–4 AU | 33±11 [18] ° | — | |||
d [19] (unconfirmed) | 33–71 [20] MJ | 7.8 [19] | — | — | — | — |
c (unconfirmed) | 15 [18] MJ | 10 [6] | — | — | — | 1.265 [18] RJ |
Outer disk | 13 [21] –400 [22] AU | 44±8 [18] ° | — | |||
candidate 1(unconfirmed) | 8 [23] MJ | 13 [23] | — | — | — | — |
b [16] (disputed [24] ) | 1.65 [14] MJ | 53±2 [21] | — | — | — | 3.4 [25] RJ |
candidate 2(unconfirmed) | 3 [23] MJ | 143 [23] | — | — | — | — |
The HD 100546 system as a whole has one confirmed protoplanet candidate and there is evidence for 1–2 others, thus it is considered an important evolutionary precursor to intermediate-mass stars with multiple super-jovian planets at moderate/wide separations like HR 8799. [26] While other hypothetical planets have been claimed to exist around the star, none of the discoveries have been confirmed.
In 2013, researchers reported that they had found what seems to be a planet in the process of being formed, embedded in the star's large disc of gas and dust. If confirmed, it would represent the first opportunity to study the early stages of planet formation observationally. [28] The flux from HD 100546 b [16] and its circumplanetary disk (CPD) are superimposed, leaving its properties such the radius and temperature thus very uncertain. [21]
Various estimates for the mass of HD 100546 b has been varying between 1 and 25 MJ. [29] [25] Although standard hot-start models imply a mass of approximately 15 MJ, other models and HD 100546 b's H-band photometry implies masses below 10 MJ for a 1-million-years-old newly born planet or if made visible by its CPD, while older ages suggest higher masses. [26] [21]
More recently in 2019 an upper limit for the planetary mass was given to be as low as 1.65 MJ based on the relation between the planet, CPD, and circumstellar disk (CSD) masses derived from numerical simulation. [14] The CPD has been assumed to be optically thin with derived upper mass and radius limits of 1.44 times as massive as Earth (ME) and 0.44 astronomical unit (AU), while the mass of CSD was given to be 50 MJ. [14] While gas-starved models are also still compatible, this would suggest that HD 100546 b is inconsistent with several planet accretion models. [14]
Fitting a single temperature blackbody to the observed fluxes of the point source component gives a very large radius of 6.9+2.7
−2.9 times that of Jupiter (RJup) and an effective temperature of 932+193
−202 K for the emitting area surrounding the embedded protoplanet respectively. [21] This large radius refers to the diffuse dust and gas envelope or debris disk surrounding the planet, not the planet itself; these estimates are mistakenly used as a single planetary radius and effective temperature for HD 100546 b by the NASA Exoplanet Archive. A best-fit luminosity was also found by the same study to be 2.3+0.6
−0.4×10−4 times as luminous as the Sun (L☉). [21]
Despite the uncertainty of the planet's properties, a 2017 study calculated HD 100546 b as a very highly reddened substellar object with a good-fit effective temperature of 2,630 K and a planetary mass and radius of 25 MJup and 3.4 RJup, making it still one of the largest exoplanets discovered by size. [25]
In April 2003, another planetary companion candidate was proposed and evidence was later gathered using the UVES echelle spectrograph at the VLT in Chile in 2005. [30] This confirms other data indicating a planetary companion with a mass approximately 20 MJ and a distance of 6.5 AU from HD 100546, [30] although further examination of the disk profile indicates it might be a more massive object such as a brown dwarf or more than one planet. [6]
The same planetary companion, dubbed "HD 100546 c", [19] [29] was observed in 2014, and is calculated to have a mass estimated to be between 5 MJ and 20 MJ. [31] [29] With an estimated distance roughly 13 AU from HD 100546, circumstantial evidence suggests that HD 100546 c may be responsible for clearing out the inner disk cavity, although it would have been rapidly accreting gas, and thus it would be unusually bright. [29] It was also expected to be surrounded by a circumplanetary disk of about 0.1 AU in radius. [31] The planet is calculated to have an accretion rate up to 10−8 M☉ per year assuming a planetary mass of 15 MJup, which would correspond to a planetary radius of 0.13 R☉ based on evolutionary tracks. [18] Thus, HD 100546 c is either in a relatively quiescent stage or its growth from accretion is at a low level or has already ceased. [18] The presence of disturbance, possibly created by HD 100546 c, is also confirmed by the detection of sulphur monoxide, indicating a shockwaves propagating through the gas disk. [32]
The position where HD 100546 c was detected was inside compared with the gap between the inner and outer disks, and outside compared with the central cavity, so the validity of the planet was shown from the characteristics of the star disk. There was a discrepancy with the discussion. This companion candidate has been contested, however, and it may be a weakly polarized disk feature instead.
ALMA observations at 1.3 mm have revealed a point source at a position angle of 37° and a projected separation of 7.8 AU, it has a mass of 33 to 77 Jupiter masses which would make it a brown dwarf, which could represent an additional planetary candidate, hereafter HD 100546 d. [19]
A disturbance in disk may have been caused by a ~10 ME planet completely embedded in the dust shroud. [12]
Coronagraphic optical observations with the Hubble Space Telescope [1] [17] show complex spiral patterns in the circumstellar disk. The causes of these structures remain uncertain, although spirals are consistent with the instabilities caused by forming planets. [27] The disk colors are similar to those derived for Kuiper Belt objects, suggesting that the same weathering processes are at work in HD 100546. The disk is fairly flat, consistent with an advanced evolutionary state, [1] and have a wide gap at 40–150 AU radii, possibly carved by an outer planet in the gap. [27]
Spectroscopic analysis of mid-IR data taken from OSCIR on the 4 m Blanco Telescope at Cerro Tololo Inter-American Observatory indicates the presence of a small particles (10–18 μm) containing silicates. [17] The material is found at distances out to 17 AU away from the star and has a temperature of approximately 227 K. [17]
A protoplanet is a large planetary embryo that originated within a protoplanetary disk and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant planets.
HD 107146 is a star in the constellation Coma Berenices that is located about 90 light-years (28 pc) from Earth. The apparent magnitude of 7.028 makes this star too faint to be seen with the unaided eye.
HD 210277 is a single star in the equatorial constellation of Aquarius. It has an apparent visual magnitude of 6.54, which makes it a challenge to view with the naked eye, but it is easily visible in binoculars. The star is located at a distance of 69.6 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −20.9 km/s.
HD 113766 is a binary star system located 424 light years from Earth in the direction of the constellation Centaurus. The star system is approximately 10 million years old and both stars are slightly more massive than the Sun. The two are separated by an angle of 1.3 arcseconds, which, at the distance of this system, corresponds to a projected separation of at least 170 AU.
HD 141569 is an isolated Herbig Ae/Be star of spectral class A2Ve approximately 364 light-years away in the constellation of Libra. The primary star has two red dwarf companions at about nine arcseconds. In 1999, a protoplanetary disk was discovered around the star. A gap in the disk led to speculation about a possible extrasolar planet forming in the disk.
AB Aurigae is a young Herbig Ae star in the Auriga constellation. It is located at a distance of approximately 531 light years from the Sun based on stellar parallax. This pre-main-sequence star has a stellar classification of A0Ve, matching an A-type main-sequence star with emission lines in the spectrum. It has 2.4 times the mass of the Sun and is radiating 38 times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K. The radio emission from the system suggests the presence of a thermal jet originating from the star with a velocity of 300 km s−1. This is causing an estimated mass loss of 1.7×10−8 M☉ yr−1.
An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987 around Beta Pictoris, a very young A-type main-sequence star. There are now a total of 27 stars around which exocomets have been observed or suspected.
HD 142527 is a binary star system in the constellation of Lupus. The primary star belongs to the Herbig Ae/Be star class, while the companion, discovered in 2012, is a red dwarf star or accreting protoplanet with a projected separation of less than 0.1″. The system is notable for its circumbinary protoplanetary disk and its discovery has helped refine models of planet formation. The orbit of companion is strongly inclined to the circumbinary protoplanetary disk.
MWC 480 is a single star, about 500 light-years away in the constellation of Auriga. It is located in the Taurus-Auriga Star-Forming Region. The name refers to the Mount Wilson Catalog of B and A stars with bright hydrogen lines in their spectra. With an apparent magnitude of 7.62, it is too faint to be seen with the naked eye.
HD 169142 is a single Herbig Ae/Be star. Its surface temperature is 7650±150 K. HD 169142 is depleted of heavy elements compared to the Sun, with a metallicity Fe/H index of −0.375±0.125, but is much younger at an age of 7.5±4.5 million years. The star is rotating slowly and has relatively low stellar activity for a Herbig Ae/Be star.
LkCa 15 is a T Tauri star in the Taurus Molecular Cloud. These types of stars are relatively young pre-main-sequence stars that show irregular variations in brightness. It has a mass that is about 97% of the Sun, an effective temperature of 4370 K, and is slightly cooler than the Sun. Its apparent magnitude is 11.91, meaning it is not visible to the naked eye.
GG Tauri, often abbreviated as GG Tau, is a quintuple star system in the constellation Taurus. At a distance of about 450 light years away, it is located within the Taurus-Auriga Star Forming Region. The system comprises three stars orbiting each other in a hierarchical triple system, known as GG Tauri A, and another binary star system more distant from the central system, known as GG Tauri B.
PDS 70 is a very young T Tauri star in the constellation Centaurus. Located 370 light-years from Earth, it has a mass of 0.76 M☉ and is approximately 5.4 million years old. The star has a protoplanetary disk containing two nascent exoplanets, named PDS 70b and PDS 70c, which have been directly imaged by the European Southern Observatory's Very Large Telescope. PDS 70b was the first confirmed protoplanet to be directly imaged.
HD 36112, also known as MWC 758, is a young Herbig Ae star located in the constellation Taurus, surrounded by irregular rings of cosmic dust. The system is about 3.5 million years old. The disk has a cavity at 50 astronomical units and two spiral arms at 30-75 au that are seen in near-infrared scattered light, but only one spiral arm is seen in ALMA images.
CI Tauri is a young star, about 2 million years old, located approximately 523 light-years away in the constellation Taurus. It is still accreting material from a debris disk at an unsteady pace, possibly modulated by the eccentric orbital motion of an inner planet. The spectral signatures of compounds of sulfur were detected from the disk.
A circumplanetary disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. They are reservoirs of material out of which moons may form. Such a disk can manifest itself in various ways.
HD 100453 is a binary star system which lies in the constellation Centaurus about 350 light years away from the Sun and is a member of the open cluster Scorpius–Centaurus association.
CQ Tauri is a young variable star in the equatorial constellation of Taurus. It is too faint to be visible to the naked eye with an apparent visual magnitude that ranges from 8.7 to 12.25. The distance to this star is approximately 487 light years based on parallax measurements, and it is drifting further away with a radial velocity of ~23 km/s. It appears to be part of the T-association Tau 4. CQ Tauri lies close enough to the ecliptic to undergo lunar occultations.