Frosty Leo Nebula
Encyclopedia
The Frosty Leo Nebula is a protoplanetary nebula
(PPN) located roughly at 3,000 light-year
s away from Earth
in the direction of the constellation
Leo
. It is a spectral bipolar nebula
. Its central star
is of optical spectral type K7II, by itself called Frosty Leo. It is unusual in that it has an extremely deep absorption feature at 3.1 µm and is unusually located at more than 900 pc above the plane of our galaxy. Further, as of 1990, it has the only known PPN circumstellar outflow in which crystalline ice dominates the long-wavelength emission spectrum and the only known PPN with point-reflection-symmetric deviations from axial symmetry.
like shape. It has an inclination angle of 15° relative to the plane of the sky. Its molecular envelope is expanding at a rate of ~25 km/s
.
survey due to its exceptionally cold IRAS color temperature
s. It also has a uniquely sharp maximum at 60-μM.
). Point symmetry is a fairly common trait of planetary nebulae as found in NGC 2022
, NGC 2371-2
, NGC 6309, Cat's Eye Nebula
, NGC 6563, Dumbbell Nebula
, Saturn Nebula
, A24, and Hb5. postulate that point symmetry is either due to the bipolar outflow
being directed by a precessing disc or a precessing common envelope binary
.
is largely depleted in its gaseous state by ice condensation into grains and for its location in the Leo constellation. Their interpretation was subsequently verified in 1988 by three independent papers. further observed in the band between 35 to 65 μM that very cold (<50 K
) silicate
dust grains, abundantly coated with crystalline ice, are responsible for the 60-μM excess.
Protoplanetary nebula
A protoplanetary nebula or preplanetary nebula is an astronomical object which is at the short-lived episode during a star's rapid stellar evolution between the late asymptotic giant branch phase and the subsequent planetary nebula phase. A PPN emits strongly in infrared radiation, and is a...
(PPN) located roughly at 3,000 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
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
in the direction of 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:...
. It is a spectral bipolar nebula
Bipolar nebula
A bipolar nebula is a distinctive nebular formation characterized by an axially symmetric bi-lobed appearance.Many, but not all, planetary nebulae exhibit an observed bipolar structure...
. Its central star
Central Star
Central Star consists of four residential skyscrapers under construction in Busan, South Korea. The tallest landmark tower measures tall and has 58 floors. Ground was broken by POSCO E&C in 2007 and is completing in 2011....
is of optical spectral type K7II, by itself called Frosty Leo. It is unusual in that it has an extremely deep absorption feature at 3.1 µm and is unusually located at more than 900 pc above the plane of our galaxy. Further, as of 1990, it has the only known PPN circumstellar outflow in which crystalline ice dominates the long-wavelength emission spectrum and the only known PPN with point-reflection-symmetric deviations from axial symmetry.
Characteristics
The Frosty Leo Nebula has two lobes that are separated by 2″ between which is an almost edge-on dust ring. It also has two relatively faint but prominent compact nebulosities, or ansae, separated by ~23″ along the polar axis of the PPN. The PPN as a whole has an hourglassHourglass
An hourglass measures the passage of a few minutes or an hour of time. It has two connected vertical glass bulbs allowing a regulated trickle of material from the top to the bottom. Once the top bulb is empty, it can be inverted to begin timing again. The name hourglass comes from historically...
like shape. It has an inclination angle of 15° relative to the plane of the sky. Its molecular envelope is expanding at a rate of ~25 km/s
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
.
Observation history
This PPN was first noticed in the IRASIRAS
The Infrared Astronomical Satellite was the first-ever space-based observatory to perform a survey of the entire sky at infrared wavelengths....
survey due to its exceptionally cold IRAS color temperature
Color temperature
Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, and other fields. The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of...
s. It also has a uniquely sharp maximum at 60-μM.
Point symmetry
It is the first bipolar PPN known to have point reflection symmetry (all others being axially symmetricAxial symmetry
Axial symmetry is symmetry around an axis; an object is axially symmetric if its appearance is unchanged if rotated around an axis . For example, a baseball bat or a tea saucer looks the same if it is rotated by any angle about the line passing lengthwise through its center, so it is axially...
). Point symmetry is a fairly common trait of planetary nebulae as found in NGC 2022
NGC 2022
NGC 2022 is an planetary nebula in the constellation Orion.In medium sized amateur telescopes it looks like small grayish patch of light. It is not very bright but it is still easy to spot it in the eyepiece....
, NGC 2371-2
NGC 2371-2
NGC 2371-2 is a dual lobed planetary nebula located in the constellation Gemini. Visually, it appears like it could be two separate objects; therefore, two entries were given to the planetary nebula by William Herschel in the "New General Catalogue", so it may be referred to as NGC 2371, NGC...
, NGC 6309, Cat's Eye Nebula
Cat's Eye Nebula
The Cat's Eye Nebula is a planetary nebula in the constellation of Draco. Structurally, it is one of the most complex nebulae known, with high-resolution Hubble Space Telescope observations revealing remarkable structures such as knots, jets, bubbles and sinewy arc-like features...
, NGC 6563, Dumbbell Nebula
Dumbbell Nebula
The Dumbbell Nebula is a planetary nebula in the constellation Vulpecula, at a distance of about 1,360 light years....
, Saturn Nebula
Saturn Nebula
The Saturn Nebula is a planetary nebula in the constellation Aquarius. It was discovered by William Herschel on September 7, 1782, using a telescope of his own design in the garden at his home in Datchet, England, and was one of his earliest discoveries in his sky survey...
, A24, and Hb5. postulate that point symmetry is either due to the bipolar outflow
Bipolar outflow
A bipolar outflow represents two continuous flows of gas from the poles of a star. Bipolar outflows may be associated with protostars , or with evolved post-AGB stars ....
being directed by a precessing disc or a precessing common envelope binary
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
.
Naming
dubbed IRAS 09371+1212 as the "Frosty Leo Nebula" because of their interpretation of the object's extremely unusual far infrared spectrum that waterWater
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
is largely depleted in its gaseous state by ice condensation into grains and for its location in the Leo constellation. Their interpretation was subsequently verified in 1988 by three independent papers. further observed in the band between 35 to 65 μM that very cold (<50 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...
) silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
dust grains, abundantly coated with crystalline ice, are responsible for the 60-μM excess.