HAT-P-11, also designated GSC 03561-02092 and Kepler-3, is a

metal-rich In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...

orange dwarf A K-type main-sequence star, also referred to as a K-type dwarf, or orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("r ...

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

with a planetary system, away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Cygnus. This star is notable for its relatively large rate of

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

. The

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of this star is about 9.6, which means it is not visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

but can be seen with a medium-sized

amateur telescope Amateur telescope making is the activity of building telescopes as a hobby, as opposed to being a paid professional. Amateur telescope makers (sometimes called ATMs) build their instruments for personal enjoyment of a technical challenge, as a wa ...

on a clear dark night. The age of this star is about 6.5 billion years. The star has active latitudes that generate

starspot Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in gene ...

s. The spots are similar in distribution to those on the Sun, but HAT-P-11 is a more active star and has a starspot coverage approximately 100 times greater than the Sun. The star appears to have an unusually small radius, which can be explained by the anomalously high helium fraction.

Planetary system

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

, designated

HAT-P-11b HAT-P-11b (or Kepler-3b) is an extrasolar planet orbiting the star HAT-P-11. It was discovered by the HATNet Project team in 2009 using the transit method, and submitted for publication on 2 January 2009. This planet is located approximatel ...

, was discovered by the

HATNet Project The Hungarian Automated Telescope Network (HATNet) project is a network of six small fully automated "HAT" telescopes. The scientific goal of the project is to detect and characterize extrasolar planets using the transit method. This network is us ...

using the

transit method Methods of detecting exoplanets usually rely on indirect strategies – that is, they do not directly image the planet but deduce its existence from another signal. Any planet is an extremely faint light source compared to its parent star. For e ...

, believed to be a little larger than the planet

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

. The planet orbits out of alignment from the star's spin axis, with an obliquity of about 100°. This star system was within the field of view of the

Kepler Mission The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

planet-hunter

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

Water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

and

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

have been detected in the atmosphere of HAT-P-11b. A trend in the

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

measurements taken to confirm the planet indicated a possible additional body in the system. This was confirmed in 2018 when a second planet, HAT-P-11c, was detected on an approximately nine-year orbit. In 2020, an

astrometric Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. History ...

detection of HAT-P-11c was published, along with

Pi Mensae b Pi Mensae b (π Men b, π Mensae b), also known as HD 39091 b, is an extrasolar planet approximately 60 light-years away in the constellation of Mensa (constellation), Mensa. The planet was announced orbiting the G-type main-sequence star, yellow ...

, allowing its inclination and true mass to be determined. Multiple 2024 studies present conflicting results about HAT-P-11c. One study suggests that the radial velocity variations attributed to HAT-P-11c may actually be caused by a magnetic activity cycle of the star. If this is the case, an outer planet may still exist given the evidence for one from astrometry, but farther from the star and with a different mass than previously thought. Another study instead claims further confirmation of the previously proposed planet. A third paper, published in response to the first, also corroborates the planetary nature of HAT-P-11c based on additional radial velocity data.

References

External links

* {{Sky, 19, 50, 50.2469, +, 48, 04, 51.085, 123 Cygnus (constellation) K-type main-sequence stars Planetary transit variables Planetary systems with two confirmed planets 3 097657 BD+47 2936

1144 Year 1144 ( MCXLIV) was a leap year starting on Saturday of the Julian calendar. Events By place Levant * Autumn – Imad al-Din Zengi, Seljuk governor (''atabeg'') of Mosul, attacks the Artuqid forces led by Kara Arslan – who ...

Planetary system

See also

References

External links