R Leonis
Encyclopedia
R Leonis is a red hypergiant
Mira-type variable star
in the constellation
Leo
.
The apparent magnitude
of R Leonis varies between 4.31 and 11.65 with a period of 312 days. At maximum it can be seen with the naked eye
, while at minimum a telescope of at least 7 cm
is needed. The star's effective temperature is estimated between 2930 and 3080 kelvin
s and radius spans between 320 and 350 solar radii (as large as 1.36–1.5 astronomical unit
s, roughly Mars
's orbital zone).
. They have inferred a putative mass for the orbiting body of twice the mass of Jupiter
, orbital period of 5.2 years and likely orbital separation of 2.7–3 astronomical units.
If confirmed such a planetary object could likely be an evaporating planet, with long comet
-like trail as hinted by intense SiO maser emissions. Planetary temperature would exceed 1500 kelvins, accounting a stellar luminosity of more than 8,000 times that of the Sun
.
Hypergiant
A hypergiant is a star with a tremendous mass and luminosity, showing signs of a very high rate of mass loss.-Characteristics:...
Mira-type variable star
Mira variable
Mira variables , named after the star Mira, are a class of pulsating variable stars characterized by very red colors, pulsation periods longer than 100 days, and light amplitudes greater than one magnitude in infrared and 2.5 magnitude in visual...
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....
Leo
Leo (constellation)
Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:...
.
The 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 R Leonis varies between 4.31 and 11.65 with a period of 312 days. At maximum it can be seen with 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"...
, while at minimum a telescope of at least 7 cm
Centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...
is needed. The star's effective temperature is estimated between 2930 and 3080 kelvin
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...
s and radius spans between 320 and 350 solar radii (as large as 1.36–1.5 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s, roughly 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...
's orbital zone).
A planetary system?
In 2009 Wiesemeyer et al. proposed that quasi-periodic fluctuations observed for the star R Leonis may be due to the presence of an evaporating substellar companion, probably an 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...
. They have inferred a putative mass for the orbiting body of twice 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,...
, orbital period of 5.2 years and likely orbital separation of 2.7–3 astronomical units.
If confirmed such a planetary object could likely be an evaporating planet, with long comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
-like trail as hinted by intense SiO maser emissions. Planetary temperature would exceed 1500 kelvins, accounting a stellar luminosity of more than 8,000 times that of 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...
.