47 Ursae Majoris
Encyclopedia
47 Ursae Majoris (often abbreviated 47 UMa) is a solar analog
, yellow dwarf
star
approximately 46 light-year
s away from Earth in the constellation
of Ursa Major
. , it has been confirmed that three Jupiter-like extrasolar planet
s orbit the star. Because of this, 47 Ursae Majoris was listed as one of top 100 target stars for NASA
's former Terrestrial Planet Finder
mission.
: according to astrometric
measurements made by the Hipparcos
astrometry satellite
, the star exhibits a parallax
of 71.11 milliarcseconds, corresponding to a distance of 14.1 parsec
s. With an apparent magnitude
of +5.03, it is visible to the naked eye
under good conditions.
to that of our Sun. It is slightly more metal-rich than the Sun, having around 110% of the solar abundance
of iron
. With a spectral type
of G1V, it is also slightly hotter than the Sun, at around 5,882 K
. 47 Ursae Majoris has an absolute magnitude
of +4.29, implying it has a visual luminosity
around 60% greater than the Sun.
Like the Sun, 47 Ursae Majoris is on the main sequence
, converting hydrogen
to helium
in its core by nuclear fusion
. Based on its chromospheric
activity, the star may be around 6,000 million years old, though evolutionary models
suggest an older age of around 8,700 million years. Other studies have yielded estimates of 4,400 and 7,000 million years for the star.
and R. Paul Butler
. The discovery was made by observing the change in the star's radial velocity
as the planet's gravity pulled it around. The measurements were made by observing the Doppler shift of the star's spectrum
. The planet, designated 47 Ursae Majoris b
, was the first long-period
extrasolar planet discovered. Unlike the majority of known long-period extrasolar planets, 47 Ursae Majoris b has a low-eccentricity orbit. The planet is at least 2.53 times the mass of Jupiter
and takes 1,078 days or 2.95 years to orbit its star. If it were to be located in our solar system, it would lie between the orbits of Mars
and Jupiter.
In 2001, preliminary astrometric measurements made by the Hipparcos
probe suggest the orbit of 47 Ursae Majoris b is inclined
at an angle of 63.1° to the plane of the sky. If these measurements are confirmed, this implies the planet's true mass
is around 2.9 times that of Jupiter. However, subsequent analysis suggests that the Hipparcos measurements are not precise enough to accurately determine the orbits of substellar companions, and the inclination and true mass remain unknown.
A second planet, designated 47 Ursae Majoris c
, was announced in 2002 by Debra Fischer
, Geoffrey Marcy, and R. Paul Butler. The discovery was made using the same radial velocity
method used to detect the first planet. According to Fischer et al., the planet takes around 2,391 days or 6.55 years to complete an orbit. This configuration is similar to the configuration of Jupiter and Saturn in our solar system, with the orbital ratio (close to 5:2), and mass ratio roughly similar.
Subsequent measurements failed to confirm the existence of the second planet, and it was noted that the dataset used to determine its existence left the planet's parameters "almost unconstrained". Analysis of a longer dataset spanning over 6,900 days suggests that while a second planet in the system is likely, periods near 2,500 days have a high false alarm probability, and the best fit model gives an orbital period of 7,586 days at a distance of 7.73 AU from the star. Nevertheless, the parameters of the second planet are still highly uncertain. On the other hand, the Catalog of Nearby Exoplanets gives a period of 2,190 days, which would put the planets close to a 2:1 ratio of orbital periods, though the reference for these parameters is uncertain: the original Fischer et al. paper is cited as a reference in spite of the fact that it gives different parameters, though this solution has been adopted by the Extrasolar Planets Encyclopaedia
.
In 2010, the discovery of a third planet, designated 47 Ursae Majoris d
, was made by using the Bayesian Kepler Periodogram. Using this model of this planetary system found out it is 100,000 times more likely to have three planets than two planets. This discovery was announced by Debra Fischer and P.C. Gregory. This 1.64 MJ planet has an orbital period of 14,002 days or 38.33 years and a semimajor axis of 11.6 AU with a moderate eccentricity of 0.16. It would be the longest-period planet discovered by radial velocity method, although longer-period planets only priorly been discovered by direct imaging and pulsar timing.
Simulations suggest that the inner part of the habitable zone
of 47 Ursae Majoris could host a terrestrial planet in a stable orbit, though the outer regions of the habitable zone would be disrupted by the gravitational influence of the planet 47 Ursae Majoris b. However, the presence of a giant planet within 2.5 AU
of the star may have disrupted planet formation in the inner system, and reduced the amount of water delivered to inner planets during accretion
. This may mean any terrestrial planet
s orbiting in the habitable zone of 47 Ursae Majoris are likely to be small and dry. , there have been two METI messages sent to 47 Ursae Majoris. Both were transmitted from Eurasia
's largest radar
— 70-meter (230-foot) Eupatoria
Planetary Radar. The first message, the Teen Age Message
, was sent on September 3, 2001, and it will arrive at 47 Ursae Majoris in July 2047. The second message, Cosmic Call 2, was sent on July 6, 2003, and it will arrive at 47 Ursae Majoris in May 2049.
Solar analog
Solar-type, solar analog, and solar twin stars are those stars that are particularly similar to the Sun. The classification is a hierarchy with solar twin being most like the Sun followed by solar analog and then solar-type...
, yellow dwarf
Yellow dwarf
A G-type main-sequence star , often called a yellow dwarf, is a main-sequence star of spectral type G and luminosity class V. Such a star has about 0.8 to 1.2 solar masses and surface temperature of between 5,300 and 6,000 K., Tables VII, VIII...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
approximately 46 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away from Earth in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Ursa Major
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...
. , it has been confirmed that three Jupiter-like extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
s orbit the star. Because of this, 47 Ursae Majoris was listed as one of top 100 target stars for NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's former Terrestrial Planet Finder
Terrestrial Planet Finder
The Terrestrial Planet Finder was a proposed project by NASA to construct a system of telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled...
mission.
Distance and visibility
47 Ursae Majoris is located fairly close to our solar systemSolar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
: according to astrometric
Astrometry
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...
measurements made by the Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
astrometry satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
, the star exhibits a parallax
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...
of 71.11 milliarcseconds, corresponding to a distance of 14.1 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s. With an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +5.03, it is visible to the naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
under good conditions.
Stellar components
47 Ursae Majoris has a similar massMass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
to that of our Sun. It is slightly more metal-rich than the Sun, having around 110% of the solar abundance
Abundance of the chemical elements
The abundance of a chemical element measures how relatively common the element is, or how much of the element is present in a given environment by comparison to all other elements...
of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
. With a spectral type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
of G1V, it is also slightly hotter than the Sun, at around 5,882 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
. 47 Ursae Majoris has an absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...
of +4.29, implying it has a visual luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
around 60% greater than the Sun.
Like the Sun, 47 Ursae Majoris is on the main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
, converting hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
to helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
in its core by nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
. Based on its chromospheric
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....
activity, the star may be around 6,000 million years old, though evolutionary models
Stellar evolution
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years to trillions of years .Stellar evolution is not studied by observing the life of a single...
suggest an older age of around 8,700 million years. Other studies have yielded estimates of 4,400 and 7,000 million years for the star.
Planetary system
In 1996 an extrasolar planet was announced in orbit around 47 Ursae Majoris by Geoffrey MarcyGeoffrey Marcy
Geoffrey W. Marcy is an American astronomer, who is currently Professor of Astronomy at the University of California, Berkeley, famous for discovering more extrasolar planets than anyone else, 70 out of the first 100 to be discovered, along with R...
and R. Paul Butler
R. Paul Butler
R. Paul Butler is an astronomer who searches for extrasolar planets.He received a BA and an MS from San Francisco State University, completing a Master's thesis with Geoffrey Marcy, and then completed his doctoral studies at the University of Maryland, College Park in 1993...
. The discovery was made by observing the change in the star's radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
as the planet's gravity pulled it around. The measurements were made by observing the Doppler shift of the star's spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
. The planet, designated 47 Ursae Majoris b
47 Ursae Majoris b
47 Ursae Majoris b is an extrasolar planet approximately 46 light-years from Earth in the constellation of Ursa Major. The planet was discovered located in a long-period orbit around the star 47 Ursae Majoris in January 1996 and as of 2011 is the innermost of three known planets in its planetary...
, was the first long-period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
extrasolar planet discovered. Unlike the majority of known long-period extrasolar planets, 47 Ursae Majoris b has a low-eccentricity orbit. The planet is at least 2.53 times the mass of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
and takes 1,078 days or 2.95 years to orbit its star. If it were to be located in our solar system, it would lie between the orbits of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
and Jupiter.
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
probe suggest the orbit of 47 Ursae Majoris b is inclined
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
at an angle of 63.1° to the plane of the sky. If these measurements are confirmed, this implies the planet's true mass
True mass
The term true mass is synonymous with the term mass, but is used in astronomy to differentiate the measured mass of a planet from the lower limit of mass usually obtained from radial velocity techniques...
is around 2.9 times that of Jupiter. However, subsequent analysis suggests that the Hipparcos measurements are not precise enough to accurately determine the orbits of substellar companions, and the inclination and true mass remain unknown.
A second planet, designated 47 Ursae Majoris c
47 Ursae Majoris c
47 Ursae Majoris c is an extrasolar planet approximately 46 light-years from Earth in the constellation of Ursa Major. The planet was discovered located in a long-period around the star 47 Ursae Majoris...
, was announced in 2002 by Debra Fischer
Debra Fischer
Debra A. Fischer is a professor of astronomy at Yale University. Fischer has co-authored over 100 papers on dwarf and sub-stellar mass objects in the galactic neighborhood, including many on extrasolar planets. She is a principal investigator with the N2K Consortium searching for exoplanets...
, Geoffrey Marcy, and R. Paul Butler. The discovery was made using the same radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
method used to detect the first planet. According to Fischer et al., the planet takes around 2,391 days or 6.55 years to complete an orbit. This configuration is similar to the configuration of Jupiter and Saturn in our solar system, with the orbital ratio (close to 5:2), and mass ratio roughly similar.
Subsequent measurements failed to confirm the existence of the second planet, and it was noted that the dataset used to determine its existence left the planet's parameters "almost unconstrained". Analysis of a longer dataset spanning over 6,900 days suggests that while a second planet in the system is likely, periods near 2,500 days have a high false alarm probability, and the best fit model gives an orbital period of 7,586 days at a distance of 7.73 AU from the star. Nevertheless, the parameters of the second planet are still highly uncertain. On the other hand, the Catalog of Nearby Exoplanets gives a period of 2,190 days, which would put the planets close to a 2:1 ratio of orbital periods, though the reference for these parameters is uncertain: the original Fischer et al. paper is cited as a reference in spite of the fact that it gives different parameters, though this solution has been adopted by the Extrasolar Planets Encyclopaedia
Extrasolar Planets Encyclopaedia
The Extrasolar Planets Encyclopedia is an astronomy website, founded in Paris, France at the Meudon Observatory by Jean Schneider in February 1995, which maintains a database of all the currently known and candidate extrasolar planets, with individual "note" pages for each planet and a full list...
.
In 2010, the discovery of a third planet, designated 47 Ursae Majoris d
47 Ursae Majoris d
47 Ursae Majoris d is an extrasolar planet approximately 46 light-years away in the constellation of Ursa Major. The planet was discovered located in a long-period orbit around the star 47 Ursae Majoris. As of 2011, it is the outermost of three known planets in its planetary system...
, was made by using the Bayesian Kepler Periodogram. Using this model of this planetary system found out it is 100,000 times more likely to have three planets than two planets. This discovery was announced by Debra Fischer and P.C. Gregory. This 1.64 MJ planet has an orbital period of 14,002 days or 38.33 years and a semimajor axis of 11.6 AU with a moderate eccentricity of 0.16. It would be the longest-period planet discovered by radial velocity method, although longer-period planets only priorly been discovered by direct imaging and pulsar timing.
Simulations suggest that the inner part of the habitable zone
Habitable zone
In astronomy and astrobiology, a habitable zone is an umbrella term for regions that are considered favourable to life. The concept is inferred from the empirical study of conditions favourable for Life on Earth...
of 47 Ursae Majoris could host a terrestrial planet in a stable orbit, though the outer regions of the habitable zone would be disrupted by the gravitational influence of the planet 47 Ursae Majoris b. However, the presence of a giant planet within 2.5 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
of the star may have disrupted planet formation in the inner system, and reduced the amount of water delivered to inner planets during accretion
Accretion (astrophysics)
In astrophysics, the term accretion is used for at least two distinct processes.The first and most common is the growth of a massive object by gravitationally attracting more matter, typically gaseous matter in an accretion disc. Accretion discs are common around smaller stars or stellar remnants...
. This may mean any terrestrial planet
Terrestrial planet
A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun...
s orbiting in the habitable zone of 47 Ursae Majoris are likely to be small and dry. , there have been two METI messages sent to 47 Ursae Majoris. Both were transmitted from Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
's largest radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
— 70-meter (230-foot) Eupatoria
Eupatoria
Yevpatoria or Eupatoria is a city in Crimea, Ukraine.-History:The first recorded settlement in the area, called Kerkinitis , was built by Greek colonists around 500 BC...
Planetary Radar. The first message, the Teen Age Message
Teen Age Message
The Teen Age Message was a METI message, transmitted from the Yevpatoria Planetary Radar to 6 nearby Sun-like stars during August–September 2001. Unlike the previous digital-only Messages, Arecibo-1974 and Cosmic Call 1, the TAM has complex, three-section structure with different forms of...
, was sent on September 3, 2001, and it will arrive at 47 Ursae Majoris in July 2047. The second message, Cosmic Call 2, was sent on July 6, 2003, and it will arrive at 47 Ursae Majoris in May 2049.
See also
- 47 Ursae Majoris in fiction
- 14 Herculis14 Herculis14 Herculis or 14 Her is an orange dwarf star approximately 59 light-years away in the constellation Hercules. Because of its apparent magnitude, the star cannot be seen with the naked eye...
- 51 Pegasi51 Pegasi51 Pegasi is a Sun-like star located 15.6 parsecs from Earth in the constellation Pegasus...
- 70 Virginis70 Virginis70 Virginis is a yellow dwarf star approximately 59 light-years away in the constellation Virgo. It is rather unusually bright for its spectral type and may be just starting to evolve into the subgiant phase....
- List of extrasolar planets