Comet 96P/Machholz or 96P/Machholz 1 is a short-period

sungrazing comet A sungrazing comet is a comet that passes extremely close to the Sun at perihelion – sometimes within a few thousand kilometres of the Sun's surface. Although small sungrazers can completely evaporate during such a close approach to the Sun, la ...

discovered on May 12, 1986, by

amateur astronomer Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers m ...

Donald Machholz Donald Edward Machholz (October 7, 1952 – August 9, 2022) was an American amateur astronomer who was credited with the discovery of 12 comets that bear his name. Personal life and death In 2014, he married photojournalist Michele Machholz ...

Loma Prieta Loma Prieta (from Spanish ''loma'' -hill, ''prieta'' -dark) is high and is the highest peak in the Santa Cruz Mountains in Northern California. Although the 1989 Loma Prieta earthquake was named for this mountain, the actual epicenter was fi ...

peak, in central

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

using binoculars. On June 6, 1986, 96P/Machholz passed from the Earth. 96P/Machholz last came to

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

on October 27, 2017, and will next come to perihelion on January 31, 2023. The comet has an estimated diameter of around . 96P/Machholz is unusual among comets in several respects. Other than small SOHO comets, its highly

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

5.29 year orbit has the smallest

distance known among numbered/regular short-period comets, bringing it considerably closer to the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

than the orbit of

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

. It is also the only known short-period comet with both high orbital

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

and high eccentricity. In 2007, 96P/Machholz was found to be both

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

-depleted and

cyanogen Cyanogen is the chemical compound with the formula ( C N)2. It is a colorless and highly toxic gas with a pungent odor. The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups – analogous to diatomic halogen molecule ...

-depleted, a chemical composition nearly unique among comets with known compositions. The chemical composition implies a different and possible extrasolar origin.

Orbit

The orbit of 96P/Machholz corresponds to the

Arietids The Arietids are a strong meteor shower that lasts from May 22 to July 2 each year, and peaks on June 7. The Arietids, along with the Zeta Perseids, are the most intense daylight meteor showers of the year. The source of the shower is unknown, but ...

and the Marsden and Kracht comet groups. Its

Tisserand parameter Tisserand's parameter (or Tisserand's invariant) is a value calculated from several orbital elements (semi-major axis, orbital eccentricity and inclination) of a relatively small object and a larger " perturbing body". It is used to distinguish dif ...

with respect to

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

, T_J, is 1.94 and comets are generally classified as Jupiter family if T_J > 2. Orbital integrations indicate that T_J was greater than 2 about 2500 years ago. 96P/Machholz is currently in a 9:4

orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with Jupiter. It will not make another close approach to the Earth until 2028, when it will pass at a distance of . It may eventually be ejected from the Solar System. 96P/Machholz has a

(closest approach to the Sun) of . At perihelion Comet Machholz passes the Sun at . It comes closer to the Sun than any numbered comet less than 321P/SOHO.

Observations

Machholz 1 entered the field of view of the orbiting

Solar and Heliospheric Observatory The Solar and Heliospheric Observatory (SOHO) is a European Space Agency (ESA) spacecraft built by a European industrial consortium led by Matra Marconi Space (now Airbus Defence and Space) that was launched on a Lockheed Martin Atlas IIAS l ...

(SOHO) in 1996, 2002, 2007, 2012, and 2017, where it was seen by the

corona Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...

-observing LASCO instrument in its C2 and C3

coronagraph A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view ...

2001/02 perihelion

Comet 96P-Machholz 1 perihelion 2001-02 skymap

During the 2001/2002 passage the comet brightened to

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

−2, and was very impressive as seen by SOHO.

2007 perihelion

Comet 96P-Machholz 1 perihelion 2007 skymap

In 2007, it appeared in SOHO's LASCO C3's field of view from April 2 to 6, peaking in brightness on April 4, 2007, around magnitude +2. In these observations, its

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

was substantially smaller than the Sun in volume, but the

forward scattering In physics, telecommunications, and astronomy, forward scatter is the deflection—by diffraction, nonhomogeneous refraction, or nonspecular reflection by particulate matter of dimensions that are large with respect to the wavelength in question ...

of light made the comet appear significantly brighter. The

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

SOHO 2333 is believed to be a fragment of Machholz that came off during the 2007 perihelion. It was discovered by

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

amateur astronomer Prafull Sharma in August 2012 by analyzing data from the

, specifically the

Large Angle and Spectrometric Coronagraph The Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory satellite (SOHO) consists of three solar coronagraphs with nested fields of view: * C1 - a Fabry–Pérot interferometer coronagraph imaging from ...

. Data analysis of this sort has become

commonplace Commonplace may refer to: *Commonplace book *Literary topos In classical Greek rhetoric, topos, ''pl.'' topoi, (from grc, τόπος "place", elliptical for grc, τόπος κοινός ''tópos koinós'', 'common place'), in Latin ''locus'' ( ...

based on public availability of SOHO images. Sharma became the third Indian to have discovered a comet in this manner.

2012 perihelion

Comet 96P-Machholz 1 perihelion 2012 skymap

Between July 12–17, 2012, 96P/Machholz was visible in the SOHO LASCO/C3 field of view and expected to brighten to about magnitude +2. Two small faint fragments of 96P/Machholz were detected in the SOHO C2 images. The fragments were five hours ahead of 96P/Machholz, and probably fragmented from the comet during the 2007 perihelion passage.

2017 perihelion

The 2017 perihelion was on October 27, 2017. At closest approach, it passed from the Sun. Coronagraphs on SOHO were monitoring the flyby for a fifth time. Its peak brightness was expected to be about 2.0, when it was closest to the Sun.

Unusual composition

Spectrographic In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a ...

analysis of the

of 96P/Machholz was made during its 2007 apparition, as part of the

Lowell Observatory Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark ...

comet composition long-term observing program. When compared with the measured abundances of five molecular species in the comae of the other 150 comets in their database, these measurements showed 96P/Machholz to have far fewer

molecules. These other comets had on average 72 times as much

as 96P/Machholz. The only comet previously seen with similar depletion both in carbon-chain molecules and cyanogens is , but it has a substantially different orbit. There are currently three hypotheses to explain the chemical composition of 96P/Machholz. One hypothesis for the difference is that 96P/Machholz was an

interstellar comet An interstellar object is an astronomical object (such as an asteroid, a comet, or a rogue planet, but not a star) in interstellar space that is not gravitationally bound to a star. This term can also be applied to an object that is on an interst ...

from outside the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

and was captured by the Sun. Other possibilities are that it formed in an extremely cold region of the Solar System (such that most carbon gets trapped in other molecules). Given how close it approaches the Sun at

, repeated baking by the Sun may have stripped most of its

References

External links

Orbit and Observations for 96P/Machholz
at the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...

Fourth sighting of 96P/Machholz by SOHO
(July 13, 2012)
"Family ties: Meet the Machholz's"
''Sungrazer Project'' (July 13, 2012) * {{DEFAULTSORT:Machholz, 096P Periodic comets Sungrazing comets 0096 096P Meteor shower progenitors Comets in 2007 Comets in 2012 Comets in 2017 19860512