433 Eros

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433 Eros
Eros - PIA02923 (color).jpg
Discovery [1]
Discovered by G. Witt
Discovery site Berlin Urania Obs.
Discovery date13 August 1898
MPC designation (433) Eros
Named after
Eros (Greek mythology) [2]
1898 DQ ·1956 PC
NEO  · Amor (I) [1]
Adjectives Erotian
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 53.89 yr (19,683 days)
Aphelion 1.7825 AU
Perihelion 1.1334 AU
1.4579 AU
Eccentricity 0.2226
1.76 yr (643 days)
 33m 35.64s / day
Inclination 10.828°
Earth  MOID 0.1505 AU ·58.6 LD
Physical characteristics
Dimensions16.84±0.06 km (mean diameter) [1] [3]
34.4×11.2×11.2 km [1] [4]
Mass (6.687±0.003)×1015 kg [3]
Mean density
2.67±0.03 g/cm³ [1] [3]
5.270 h [1]
0.25±0.06 [1]
S (Tholen), S (SMASS) [1]
B–V = 0.921 [1]
U–B = 0.531 [1]
7.0–15 [5]
11.16 [1]

    Eros ( /ˈɪərɒs/ EER-os; minor planet designation: 433 Eros), provisional designation 1898 DQ, is a stony and elongated asteroid of the Amor group and the first discovered and second-largest near-Earth object with a mean-diameter of approximately 16.8 kilometers. Visited by the NEAR Shoemaker space probe in 1998, it became the first asteroid ever studied from orbit.

    A formal minor planet designation is, in its final form, a number–name combination given to a minor planet. Such designation always features a leading number assigned to a body once its orbital path is sufficiently secured. The formal designation is based on the minor planet's provisional designation, which was previously assigned automatically when it had been observed for the first time. Later on, the provisional part of the formal designation may be replaced with a name. Both formal and provisional designations are overseen by the Minor Planet Center (MPC), a branch of the International Astronomical Union.

    Asteroid Minor planet that is not a comet

    Asteroids are minor planets, especially of the inner Solar System. Larger asteroids have also been called planetoids. These terms have historically been applied to any astronomical object orbiting the Sun that did not resemble a planet-like disc and was not observed to have characteristics of an active comet such as a tail. As minor planets in the outer Solar System were discovered they were typically found to have volatile-rich surfaces similar to comets. As a result, they were often distinguished from objects found in the main asteroid belt. In this article, the term "asteroid" refers to the minor planets of the inner Solar System including those co-orbital with Jupiter.


    The eccentric asteroid was discovered by German astronomer Carl Gustav Witt at the Berlin Urania Observatory on 13 August 1898, and later named after Eros, a god from Greek mythology. [2]

    Carl Gustav Witt German astronomer

    Carl Gustav Witt was a German astronomer and discoverer of two asteroids who worked at the Berlin Urania Observatory, a popular observatory of the Urania astronomical association of Berlin.

    Eros god of love in Greek mythology

    In Greek mythology, Eros is the Greek god of love and sex. His Roman counterpart was Cupid ("desire"). Normally, he is described as one of the children of Aphrodite and Ares and, with some of his siblings, was one of the Erotes, a group of winged love gods. In some traditions, he is described as one of the primordial gods.

    Greek mythology body of myths originally told by the ancient Greeks

    Greek mythology is the body of myths originally told by the ancient Greeks. These stories concern the origin and the nature of the world, the lives and activities of deities, heroes, and mythological creatures, and the origins and significance of the ancient Greeks' own cult and ritual practices. Modern scholars study the myths in an attempt to shed light on the religious and political institutions of ancient Greece and its civilization, and to gain understanding of the nature of myth-making itself.



    Eros was discovered on 13 August 1898, by Carl Gustav Witt at Berlin Urania Observatory and Auguste Charlois at Nice Observatory. [6] Witt was taking a 2-hour exposure of Beta Aquarii to secure astrometric positions of asteroid 185 Eunike. [7]

    Auguste Charlois French astronomer

    Auguste Honoré Charlois was a French astronomer who discovered 99 asteroids while working at the Nice Observatory in southeastern France.

    Nice Observatory observatory

    The Nice Observatory is an astronomical observatory located in Nice, France on the summit of Mount Gros. The observatory was founded in 1879, by the banker Raphaël Bischoffsheim. The architect was Charles Garnier, and Gustave Eiffel designed the main dome.

    Beta Aquarii double star in the constellation Aquarius

    Beta Aquarii is a star in the constellation of Aquarius. Based upon parallax measurements obtained during the Hipparcos mission, it is approximately 540 light-years (165 parsecs) from the Sun. The primary or 'A' component is officially named Sadalsuud, the traditional name for the system.

    Later studies

    During the opposition of 1900–1901, a worldwide program was launched to make parallax measurements of Eros to determine the solar parallax (or distance to the Sun), with the results published in 1910 by Arthur Hinks of Cambridge. [8] A similar program was then carried out, during a closer approach, in 1930–1931 by Harold Spencer Jones. [9] The value of the Astronomical Unit (roughly the Earth-Sun distance) obtained by this program was considered definitive until 1968, when radar and dynamical parallax methods started producing more precise measurements.

    Parallax difference in the apparent position of an object viewed along two different lines of sight

    Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects show a larger parallax than farther objects when observed from different positions, so parallax can be used to determine distances.

    Cambridge City and non-metropolitan district in England

    Cambridge is a university city and the county town of Cambridgeshire, England, on the River Cam approximately 50 miles (80 km) north of London. At the United Kingdom Census 2011, its population was 123,867 including 24,506 students. Cambridge became an important trading centre during the Roman and Viking ages, and there is archaeological evidence of settlement in the area as early as the Bronze Age. The first town charters were granted in the 12th century, although modern city status was not officially conferred until 1951.

    Sir Harold Spencer Jones KBE FRS FRSE PRAS was an English astronomer. He became renowned as an authority on positional astronomy and served as Astronomer Royal for 23 years. Although born "Jones", his surname became "Spencer Jones".

    Eros was the first asteroid detected by the Arecibo Observatory's radar system. [10] [11]

    Arecibo Observatory Radio telescope in Arecibo, Puerto Rico

    The Arecibo Observatory is a radio telescope in the municipality of Arecibo, Puerto Rico. As of 2018, the observatory is operated by University of Central Florida, Yang Enterprises and UMET, under cooperative agreement with the US National Science Foundation (NSF). The observatory is the sole facility of the National Astronomy and Ionosphere Center (NAIC), which is the formal name of the observatory. From its construction in the 1960s until 2011, the observatory was managed by Cornell University.

    Eros was one of the first asteroids visited by a spacecraft, the first one orbited, and the first one soft-landed on. NASA spacecraft NEAR Shoemaker entered orbit around Eros in 2000, and landed in 2001.

    NASA US government agency responsible for civilian space programs, and aeronautical and aerospace research

    The National Aeronautics and Space Administration is an independent agency of the United States Federal Government responsible for the civilian space program, as well as aeronautics and aerospace research.

    <i>NEAR Shoemaker</i> First mission of the Discovery program; orbital reconnaissance of the near-Earth asteroid 433 Eros

    The Near Earth Asteroid Rendezvous – Shoemaker, renamed after its 1996 launch in honor of planetary scientist Eugene Shoemaker, was a robotic space probe designed by the Johns Hopkins University Applied Physics Laboratory for NASA to study the near-Earth asteroid Eros from close orbit over a period of a year. The mission succeeded in closing in with the asteroid and orbited it several times, finally terminating by touching down on the asteroid on 12 February 2001.


    Eros is a Mars-crosser asteroid, the first known to come within the orbit of Mars. Objects in such an orbit can remain there for only a few hundred million years before the orbit is perturbed by gravitational interactions. Dynamical integrations suggest that Eros may evolve into an Earth-crosser within as short an interval as two million years, and has a roughly 50% chance of doing so over a time scale of 108–109 years. [12] It is a potential Earth impactor, [12] about five times larger than the impactor that created Chicxulub crater and led to the extinction of the dinosaurs. [lower-alpha 2]


    Eros is named after the Greek god of love, Erōs. It is pronounced /ˈɪərɒs/ EER-os or sometimes /ˈɛrɒs/ ERR-os. The rarely used adjectival form of the name is Erotian /ɪˈrʃən/ . [13]

    NEAR Shoemaker

    Animation of NEAR Shoemaker trajectory from May 31, 1996 to February 12, 2001.
NEAR Shoemaker; 433 Eros; Earth;   253 Mathilde ; Sun; Animation of NEAR Shoemaker trajectory.gif
    Animation of NEAR Shoemaker trajectory from May 31, 1996 to February 12, 2001.
    NEAR Shoemaker; 433 Eros; Earth;    253 Mathilde ; Sun;
    Animation of NEAR Shoemaker's trajectory around 433 Eros from April 1, 2000 to February 12, 2001
NEAR Shoemaker *   433 Eros Animation of NEAR Shoemaker trajectory around 433 Eros.gif
    Animation of NEAR Shoemaker 's trajectory around 433 Eros from April 1, 2000 to February 12, 2001
       NEAR Shoemaker  ·  433 Eros

    The NEAR Shoemaker probe visited Eros twice, first with a 1998 flyby, and then by orbiting it in 2000 when it extensively photographed its surface. On February 12, 2001, at the end of its mission, it landed on the asteroid's surface using its maneuvering jets.

    This was the first time a Near Earth asteroid was closely visited by a spacecraft. [14]

    Physical characteristics

    Surface gravity depends on the distance from a spot on the surface to the center of a body's mass. Eros's surface gravity varies greatly because Eros is not a sphere but an elongated peanut-shaped (or potato- or shoe-shaped) object. The daytime temperature on Eros can reach about 100 °C (373 K) at perihelion. Nighttime measurements fall near −150 °C (123 K). Eros's density is 2.67 g/cm3, about the same as the density of Earth's crust. It rotates once every 5.27 hours.

    NEAR scientists have found that most of the larger rocks strewn across Eros were ejected from a single crater in an impact approximately 1 billion years ago. [15] (The crater involved was proposed to be named "Shoemaker", but is not recognized as such by the International Astronomical Union (IAU), and has been formally designated Charlois Regio.) This event may also be responsible for the 40 percent of the Erotian surface that is devoid of craters smaller than 0.5 kilometers across. It was originally thought that the debris thrown up by the collision filled in the smaller craters. An analysis of crater densities over the surface indicates that the areas with lower crater density are within 9 kilometers of the impact point. Some of the lower density areas were found on the opposite side of the asteroid but still within 9 kilometers. [16]

    It is theorized that seismic shockwaves propagate through the asteroid, shaking smaller craters into rubble. Since Eros is irregularly shaped, parts of the surface antipodal to the point of impact can be within 9 kilometres of the impact point (measured in a straight line through the asteroid) even though some intervening parts of the surface are more than 9 kilometres away in straight-line distance. A suitable analogy would be the distance from the top centre of a bun to the bottom centre as compared to the distance from the top centre to a point on the bun's circumference: top-to-bottom is a longer distance than top-to-periphery when measured along the surface but shorter than it in direct straight-line terms. [16]

    Compression from the same impact is believed to have created the thrust fault Hinks Dorsum. [17]

    Data from the Near Earth Asteroid Rendezvous spacecraft collected on Eros in December 1998 suggests that it could contain 20 billion tonnes of aluminum and similar amounts of metals that are rare on Earth, such as gold and platinum. [18]

    Visibility from Earth

    Path in sky during opposition 2011/2012 Eros path 2012.png
    Path in sky during opposition 2011/2012

    On January 31, 2012, Eros passed Earth at 0.17867  AU (26,729,000  km ; 16,608,000  mi ), [19] [20] about 70 times the distance to the Moon, with a visual magnitude of +8.1. [21] During rare oppositions, every 81 years, such as in 1975 and 2056, Eros can reach a magnitude of +7.0, [5] which is brighter than Neptune and brighter than any main-belt asteroid except 1 Ceres, 4 Vesta and, rarely, 2 Pallas and 7 Iris. Under this condition, the asteroid actually appears to stop, but unlike the normal condition for a body in heliocentric conjunction with Earth, its retrograde motion is very small. For example, in January and February 2137, it moves retrograde only 34 minutes in right ascension. [1]

    See also


    1. A composite image of the north polar region, with the craters Psyche above and Himeros below. The long ridge Hinks Dorsum, believed to be a thrust fault, can be seen snaking diagonally between them. The smaller crater in the foreground is Narcissus (Watters, 2011)
    2. Ratio of mean diameters is 16.84 km/~10 km; the volume ratio is approximately 4.8 (cubed value).

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    4 Vesta second largest asteroid of the main asteroid belt

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    Further reading