HD 149026
Encyclopedia
HD 149026 is a yellow subgiant star
approximately 257 light-year
s away in the constellation
of Hercules
. The star is thought to be much more massive, larger, and brighter than the Sun
. , an extrasolar planet
has been confirmed to be orbiting the star. The name of this star comes from its identifier in the Henry Draper Catalog.
. The higher mass of the star causes that despite considerably younger age (2.0 Ga) it is already much more evolved
than the Sun. The internal fusion
of hydrogen
in the core of the star is coming to an end, and it is beginning to evolve towards red giant
hood. HD 149026 is about 260 light-year
s distant, which means the star is not visible to the unaided eye. However, it should be an easy target to binoculars
or a small telescope
.
The star is over twice as enriched with chemical element
s heavier than hydrogen
and helium
as the Sun. Because of this and the fact that the star is relatively bright, a group of astronomer
s in N2K Consortium
began to study the star. The star's anomalous composition as measured may be surface pollution only, from the intake of heavy-element planetesimals.
orbiting the star. The planet, designated HD 149026 b
, was detected transiting the star allowing its diameter to be measured. It was found to be smaller than other known transiting planets, meaning the planet is unusually dense for a closely orbiting giant planet. The temperature of the giant planet is calculated to be 3700 °F (2,037.8 °C), generating so much infrared heat that it glows. Scientists believe the planet absorbs nearly all the sunlight and radiates it into space as heat.
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 257 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 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 Hercules
Hercules (constellation)
Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today...
. The star is thought to be much more massive, larger, and brighter than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. , an 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...
has been confirmed to be orbiting the star. The name of this star comes from its identifier in the Henry Draper Catalog.
The star
The star is thought to be much more massive, larger, and brighter than the SunSun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. The higher mass of the star causes that despite considerably younger age (2.0 Ga) it is already much more evolved
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...
than the Sun. The internal 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...
of 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...
in the core of the star is coming to an end, and it is beginning to evolve towards red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
hood. HD 149026 is about 260 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 distant, which means the star is not visible to the unaided eye. However, it should be an easy target to binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
or a small telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
.
The star is over twice as enriched with chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
s heavier than 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...
and 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...
as the Sun. Because of this and the fact that the star is relatively bright, a group of astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
s in N2K Consortium
N2K Consortium
The N2K Consortium is a collaborative multinational effort by American, Chilean and Japanese astronomers to find additional extrasolar planets around stars that are...
began to study the star. The star's anomalous composition as measured may be surface pollution only, from the intake of heavy-element planetesimals.
Planetary system
In 2005 they discovered an unusual extrasolar planetExtrasolar 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...
orbiting the star. The planet, designated HD 149026 b
HD 149026 b
HD 149026 b is an extrasolar planet approximately 257 light-years away in the constellation of Hercules. The planet was discovered after it transited its parent star, HD 149026...
, was detected transiting the star allowing its diameter to be measured. It was found to be smaller than other known transiting planets, meaning the planet is unusually dense for a closely orbiting giant planet. The temperature of the giant planet is calculated to be 3700 °F (2,037.8 °C), generating so much infrared heat that it glows. Scientists believe the planet absorbs nearly all the sunlight and radiates it into space as heat.