HD 179949 is a 6th
magnitude
Magnitude may refer to:
Mathematics
*Euclidean vector, a quantity defined by both its magnitude and its direction
*Magnitude (mathematics), the relative size of an object
*Norm (mathematics), a term for the size or length of a vector
*Order of ...
star in the
constellation of
Sagittarius. It is a yellow-white
dwarf
Dwarf or dwarves may refer to:
Common uses
*Dwarf (folklore), a being from Germanic mythology and folklore
* Dwarf, a person or animal with dwarfism
Arts, entertainment, and media Fictional entities
* Dwarf (''Dungeons & Dragons''), a humanoid ...
(
spectral class
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...
F8 V), a type of star hotter and more luminous than the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
. The star is located about 90
light years from
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
and might be visible under exceptionally good conditions to an experienced observer without technical aid; usually
binoculars are needed.
The star HD 179949 is named Gumala. The name was selected in the
NameExoWorlds
NameExoWorlds (also known as IAU NameExoWorlds) is the name of various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, which would later be considered for official ad ...
campaign by
Brunei
Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely surrounded by t ...
, during the 100th anniversary of the
IAU
The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...
. Gumala is a
Malay word, which means a magic
bezoar stone found in snakes, dragons, etc.
Properties
This is an
F-type main-sequence star
An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables VII ...
classified with a
spectral type
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...
of F8V.
[ It has an estimated mass of 1.23 times the solar mass and a radius of 1.20 times the ]solar radius
Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3:
:1\,R_ = 6.957\ ...
.[ Its photosphere is shining with 1.95 times the ]solar luminosity
The solar luminosity (), is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun.
One nominal ...
at an effective temperature of 6,220 K.[ Its metallicity, the abundance of elements other than hydrogen and helium, is high, with 162% the solar iron abundance, following the trend that stars with giant planets are more metal-rich.][
With an estimated age of 1.2 billion years,][ HD 179949 is a chromospherically active star and has a complex magnetic field with a maximum strength of 10 G. Like the Sun, this star has ]differential rotation
Differential rotation is seen when different parts of a rotating object move with different angular velocities (rates of rotation) at different latitudes and/or depths of the body and/or in time. This indicates that the object is not solid. In fl ...
, with the equatorial region having a faster rotation period, of 7.62 ± 0.07 days, compared to a rotation period of 10.3 ± 0.8 days in the poles.[ The star's ]projected rotational velocity
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface.
The rotation of a star produces an equatorial bulg ...
is 7.0 km/s,[ corresponding to an inclination angle of about 60°.][ HD 179949 has been classified as a ]BY Draconis variable
BY Draconis variables are variable stars of late spectral types, usually K or M, and typically belong to the main sequence. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in thei ...
, which varies in brightness due to rotational modulation
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outsi ...
of spots on the surface.[
Monitoring of the star's ]spectral lines
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...
suggested a possible correlation between the star's chromospheric activity and the orbital period of its planet HD 179949 b. Later observations showed that this correlation is not present, with the star's activity being in synchrony with the star's rotation, instead of the exoplanet's orbit.[ By 2022, stellar X-ray flares correlation with the planetary orbit was not detected too.]
Planetary system
The discovery of an extrasolar planet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
orbiting HD 179949 with a period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
of only 3.1 days was published in 2001. It was detected with the radial velocity method
Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in t ...
from observations of the star with the UCLES spectrograph, in the Anglo-Australian Telescope
The Anglo-Australian Telescope (AAT) is a 3.9-metre equatorially mounted telescope operated by the Australian Astronomical Observatory and situated at the Siding Spring Observatory, Australia, at an altitude of a little over 1,100 m. In 2 ...
, as part of the Anglo-Australian Planet Search
The Anglo Australian Planet Search or (AAPS) is a long-term astronomical survey started in 1998 and continuing to the present. It is being carried out on the 3.9-metre Anglo-Australian Telescope (AAT) of the Anglo-Australian Observatory in Austral ...
.[ With a ]minimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes.
Minimum mass is a widely cited statistic for extrasolar planets detected by the radial veloci ...
of 92% of the mass of Jupiter, it is a hot Jupiter
Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere tem ...
, orbiting the star at a distance of only 0.04 AU. Its orbit is nearly circular, with a best fit orbital eccentricity of 0.022 ± 0.015.[ Planets close to their stars have high chances of ]transit
Transit may refer to:
Arts and entertainment Film
* ''Transit'' (1979 film), a 1979 Israeli film
* ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world
* ''Transit'' (2006 film), a 2006 ...
, but photometric observations of HD 179949 ruled out this possibility.[
]Infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
observations of HD 179949 with the Spitzer Space Telescope detected 0.14% variations in the system's brightness in phase with the orbital period of the planet, indicating large luminosity variation between the illuminated side and the dark side of the planet, implying that less than 21% of the incident stellar energy is transferred to the dark side.[ In 2014, infrared observations of the system with the CRIRES instrument, at the ]Very Large Telescope
The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m acro ...
, directly detected the thermal spectrum of the planet, revealing absorption features of carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
and water vapor
(99.9839 °C)
, -
, Boiling point
,
, -
, specific gas constant
, 461.5 J/( kg·K)
, -
, Heat of vaporization
, 2.27 MJ/kg
, -
, Heat capacity
, 1.864 kJ/(kg·K)
Water vapor, water vapour or aqueous vapor is the gaseous p ...
in its atmosphere. The radial velocity of the planet has variations of 142.8 ± 3.4 km/s due to orbital motion, which allowed the calculation of a real mass of 0.98 ± 0.04 Jupiter masses and an orbital inclination
Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object.
For a satellite orbiting the Eart ...
of 67.7 ± 4.3 degrees.[
]
References
External links
SIMBADstar entry
planet entry
{{DEFAULTSORT:HD 179949
179949
094645
Sagittarius (constellation)
F-type main-sequence stars
7291
0749
Durchmusterung objects