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Asteroid 100

Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets. Asteroids are material left over from the formation of the solar system.

They are known as minor planets; (in 2006 the International Astronomical Union reclassified Ceres - see Dwarf Planets below. Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles. Sixteen asteroids have a diameter of 240 km or greater. They have been found inside Earth's orbit to beyond Saturn's orbit. Most, however, are contained within a main belt that exists between the orbits of Mars and Jupiter. Some have orbits that cross Earth's path and some have even hit the Earth in times past. One of the best preserved examples is Barringer Meteor Crater near Winslow, Arizona.

Asteroids are categorised by their position in the solar system. 

• Main Belt located between Mars and Jupiter approximately 2 to 4 AU from the Sun. At then end of the 18th century it was realised that, from the calculated orbits of the known planets, there should have been another planets between Mars and Jupiter. As a systematic search was being established, Guiseppe Piazza (1801) discovered Ceres. It was established that the 'missing planet' had not formed, the gravitational influence of the massive Jupiter had stirred up the growing small bodies, subjecting them to frequent collisions and forming the multitude of small bodies we observe today. Many asteroids from this 'Main Belt' have been ejected from the belt and collided with other planets and moons of the Solar System.
• Near-Earth Asteroids (NEA) which closely approach the Earth
• Trojans which are located near to Jupiter's Lagrange points.

Asteroids are given a number indicating the sequence of their discovery. 

The image to the left shows the comparative size of the Moon and the first 10 asteroids; Ceres, Pallas, Juno. Vesta, Astraea, Hebe, Iris, Flora, Metis and Hygiea.

The number of known asteroids (minor planets) is maintained by the Minor Planet Center, see MPC; the total was 37,226,817 on 2006 June 13. See MPC Archive Statistics for the latest figures. The MPC also maintain records of the known comets.

For a 'real time' plot of the location of major and minor planets within Jupiter's orbit see Plot of the Inner Solar System.

Dwarf Planets

The International Astronomical Union had a controversial meeting in Prague in 2006; it reviewed the classification of a planet. On August 24^th 2006, the General Assembly "agreed that a 'planet' is defined as a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

This means that the Solar System consists of eight "planets" Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A new distinct class of objects called "dwarf planets" was also decided. It was agreed that "planets" and "dwarf planets" are two distinct classes of objects. The first members of the "dwarf planet" category are Ceres, Pluto and 2003 UB313 (later named - Eris). More "dwarf planets" are expected to be announced by the IAU in the coming months and years."

The IAU further defined the classification as:

1. A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

2. A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

3. All other objects3 except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

Click image for more details and larger image from IAU

Thus Ceres, previously a minor planet or asteroid, was promoted to become a 'dwarf planet' where it joins Pluto, previously a 'planet'. The IAU further resolved that Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

NASA's DAWN spacecraft is off to visit Asteroids Vesta and Ceres

NASA launched a spacecraft, Dawn, on September 27th 2007 with the mission objective of flying to the two giant asteroids Vesta and Ceres.

Dawn's first stop is Vesta - an asteroid that may implicate ancient supernovas in the solar system's birth.

Telescopic observations of Vesta and studies of meteorites believed to have come from Vesta suggest that the asteroid may have been partially molten early in its history, allowing heavy elements like iron to sink and form a dense core with a lighter crust on top. 

If all goes as planned, Dawn would reach Vesta and enter orbit in the year 2011. Detailed images of Vesta's surface will reveal traces of its molten past, while spectrometers catalog the minerals and elements that make up its surface.

After orbiting Vesta for about 7 months, Dawn will undertake a manoeuvre never before attempted: leave the orbit of one distant body, and fly to and orbit another.

This kind of "asteroid hopping" would be practically impossible if Dawn used conventional rocket fuel. "We would need one of the largest rockets that the US has to carry all the propellant," says Marc Rayman, Project System Engineer for Dawn at JPL. Instead, Dawn uses ion propulsion, which requires only one-tenth as much propellant. Dawn is planned to arrive at Ceres in 2015.

Asteroid 100

I am gradually working my way through collecting images of the Messier 110, Lunar 100 and the Caldwell Objects. I became interested in capturing the movement of asteroids over hours and days. Asteroids are known by name and a sequential number indicating the order of their discovery. The first 100 were discovered between 1801 and 1868.

So why not try to image the first 100 asteroids to be discovered? Capturing asteroid images is one thing I can do on poor seeing nights in my light polluted backyard.

My images of the first 100 asteroids are shown below, click on individual asteroid name to go straight to the image, or scroll down:

Note that each of the images below cover approximately 14.5' x 10.9' of sky.

1 Ceres

Ceres was the first asteroid to be discovered (Guiseppe Piazza, January 1st 1801). Ceres is the largest and most massive Main Belt asteroid (Diameter 590 miles, Orbit period 4.60 years, Distance 178 million miles).

Ceres was discovered by accident. Piazzi was searching for a star listed by Francis Wollaston as Mayer 87 because it was not in Mayer's zodiacal catalogue in the position given (it eventually transpired that Wollaston had made a mistake —the star was in fact Lacaille 87). Instead, Piazzi found a moving star-like object, which he thought at first was a comet.

Note that Ceres was promoted to a 'dwarf planet' at the IAU Assembly in 2006 - see Dwarf Planets above

2 Pallas

Pallas was discovered by Wilhelm Olbers on March 28th 1802. Pallas is the second largest Main Belt asteroid (Diameter 334 miles, Orbit period 4.61 years).

Pallas is only a little larger than 4 Vesta. Its orbit is located in the central part of the belt but it is somewhat inclined and eccentric for a large asteroid. 

2 Pallas in Coma Berenices Meade LX200GPS 10" f6.3 Starlight Xpress MX7C CCD Camera 30secs Dorridge, UK  20:56 UT 2005-04-29	3 days later: 2Pallas moved on Meade LX200GPS 10" f6.3 Starlight Xpress MX7C CCD Camera 30secs Dorridge, UK  20:32 UT 2005-05-02
2 Pallas in Coma Berenices Meade LX200GPS 10" f6.3 Starlight Xpress MX7C CCD Camera 30secs Dorridge, UK  20:42 UT 02 2005-05-02
	2 Pallas in Coma Berenices Meade LX200GPS 10" f6.3 Starlight Xpress MX7C CCD Camera 20secs Dorridge, UK  21:29 UT 2005-05-07

3 Juno

Juno is a  Main belt asteroid which was discovered in 1804 by Karl L Harding with a 2" telescope. Juno is the highest Roman Goddessh. (Dimensions: 290 x 240 x 190 km, Orbit period 4.36 years). Spectroscopic studies of the Junonian surface conclude that Juno could be the body of origin of ordinary chondrites, a common group of stony meteorites composed of iron-containing silicates such as olivine and pyroxene.

4 Vesta

Vesta was the fourth asteroid to be discovered (Heinrich Wilhelm Olbers 1807). Vesta is the third largest Main Belt asteroid (Diameter 285 miles, Orbit period 3.63 years) and the only Main Belt asteroid visible to the naked eye.

After the discovery of Vesta in 1807, no other asteroids were discovered for 38 years; the next was 5 Astraea.

		The same area of sky revisited 9 days later (under poor seeing conditions) - Asteroid Vesta has moved on.
Meade LX90 with MX7C Starlight Xpress CCD Dorridge, UK 21:45UT 2003-05-05 30secs @ f6.3		Meade LX90 with MX7C Starlight Xpress CCD Dorridge, UK 22:05UT 2003-05-14 20secs @ f6.3

5 Astraea

Astraea is a large Main belt asteroid which was discovered in 1845 by Karl Ludwig Hencke.  (Dimensions 167x123x82 km, Orbit period 4.13 years, Distance 261.7m km). It has a highly reflective surface and its probable composition is nickel-iron with magnesium and iron silicates.

6 Hebe

Hebe is a very large Main belt asteroid which was discovered in 1847 by Karl Ludwig Hencke. Hebe is the Greek goddess of youth (Diameter 115 miles, Orbit period 3.78 years). It has a bright surface and composition of nickel-iron metals and silicate rocks.

7 Iris

Iris is a large Main belt asteroid which was discovered in 1847 by J R Hind from London, UK.  (Dimensions 225x190x190 km, Orbit period 3.68 years, Distance 131.3million km). It has a highly reflective surface and its probable composition is nickel-iron with magnesium and iron silicates.

8 Flora

Flora is a bright Main belt asteroid. It is the innermost large asteroid; no asteroid closer to the sun has a diameter above 25 km. Flora was discovered in 1847 by J R Hind.  (Dimensions 145x145x120 km, Orbit period 3.27 years, Distance 133.9million km). The composition is a mixture of silicate rocks and nickel-iron metal.

9 Metis

9 Metis is one of the largest Main belt asteroids; it is composed of silicates and metallic nickel-iron. Metis was discovered by Andrew Graham on April 25, 1848; his only asteroid discovery. It is also the only asteroid to have been discovered as a result of observations from Ireland. Its name comes from the mythological Metis, a Titaness, daughter of Tethys and Oceanus. Metis is also the name of a satellite of Jupiter. (Size 235 x 195 x 140 km, Orbit period 3.69 years, Distance 241.9 million km).

10 Hygiea

Hygiea is the fourth largest Main belt asteroid. It was discovered by A. de Gasparis in 1849 (Diameter 253 miles, Orbit period 5.56 years). Hygiea is composed of primitive carbonaceous material similar to the chondrite meteorites. It is the main member of the Hygiea family.

11 Parthenope

11 Parthenope is a large, bright Main belt asteroid. It was discovered by A. de Gasparis in 1850 (Diameter 153.3 miles, Orbit period 3.84 years, Distance 250.8 million km).

12 Victoria

12 Victoria is a large Main belt asteroid. It is probably composed of silicate rock and nickel-iron. It was discovered by J. R. Hind on September 13, 1850.

Victoria is officially named after the Roman goddess of victory, but the name also honours Queen Victoria of the United Kingdom.   (Diameter 112.8 km, Orbit period 3.57 years, Distance 254.8 million km). 

13 Egeria

Egeria is a large Main belt asteroid. It was discovered by de Gasparis in 1850 (Diameter 129 miles, Orbit period 4.13 years).

14 Irene

Irene is a large Main belt asteroid. This stony asteroid contains also metallic iron-nickel. It was discovered by John Russell Hind in 1851 (Diameter 113 miles, Orbit period 4.16 years, Distance 133 million  miles).

15 Eunomia

Eunomia is a very large inner Main belt asteroid. It is the largest of the stony (S-type) asteroids. It was discovered by A de Gasparis in 1851 (Diameter 330 km, Orbit period 4.30 years, Distance 281.7 million  km.)

16 Psyche

Psyche is a very large Main belt asteroid. It is the largest of the metallic (M-type) asteroids. It was discovered by Annibale de Gasparis in 1852 (Diameter 280 x 230 x 190 km, Orbit period 4.99 years, Distance 357.3 million  km.)

17 Thetis

17 Thetis is a large Main belt asteroid. It is a S-type asteroid so it has a relatively bright silicate surface. It was discovered by John Russell Hind in 1852 (Diameter 90 km, Orbit period 3.88 years, Distance 243.8 million  km).

18 Melpomene

Melopmene is a large bright Main belt asteroid. It is composed of silicates and metals. It was discovered by John Russell Hind in 1852 (Diameter 93 x 78 miles, Orbit period 3.48 years, Distance 129 million  miles).

19 Fortuna

Fortuna  is one of the largest main belt asteroids. It has a composition similar to 1 Ceres; a darkly coloured surface and composition of primitive carbonates. It was discovered by John Russell Hinds in London in 1852 (Diameter 215 km, Orbit period 3.81 years, Distance 164.2 million  km).

20 Massalia

Massalia is a large, fairly bright Main belt asteroid. It was discovered by A de Gasparis in 1852 (Diameter 145.5 km, Orbit period 3.74 years, Distance 238 million  km).

21 Lutetia

Lutetia is a large Main belt metallic M-type asteroid. It was discovered by Hermann Goldschmidt in 1852 (Diameter 100 km, Orbit period 3.80 years, Distance 232.3 million  km).

22 Kalliope

Kalliope is a large Main belt metallic M-type asteroid. It was discovered by J R Hind in 1852 (Dimensions 215 x 180 x 150 km, Orbit period 4.96 years, Distance 260.4 million  km).

23 Thalia

23 Thalia is a large Main belt asteroid. It was discovered by J R Hind in 1852 (Dimensions 107.5 km, Orbit period 4.26 years, Distance 189.9 million  km).

24 Themis

Themis is a large Main belt asteroid which was discovered in 1853 by Annibale de Gasparis.  (Dimensions 198 km, Orbit period 5.54 years, Distance 354.0m km). 

25 Phocaea

Phocaea is a Main belt asteroid. It was discovered by J Chacomac in 1853 (Diameter 75.1 km, Orbit period 3.72 years, Distance 156.0 million  km).

26 Proserpina

Proserpina is a Main belt asteroid. It was discovered by R Luther in 1853 (Diameter 95.1 km, Orbit period 4.33 years, Distance 309.1 million  km).

27 Euterpe

27 Euterpe is a large Main belt asteroid. It was discovered by J R Hind in 1853 (Diameter 124 x 75 km, Orbit period 3.60 years, Distance 247.1 million  km).

28 Bellona

28 Bellona is a large, Main belt asteroid. It was discovered by R Luther in 1854 (Diameter 120.9 km, Orbit period 4.63 years, Distance 242.2 million  km).

29 Amphitrite

Amphitrite was discovered by Albert Marth in 1854; it is named after Amphitride, a sea goddess in Greek mythology. Amphitride is a Main belt asteroid (Diameter 132 miles, Orbit period 4.08 years).

30 Urania

30 Urania  was discovered by J R Hind on July 22nd 1854; it is named after Urania, the Greek Muse of Astronomy. It is a large Main belt asteroid (Diameter 100.15 km, Orbit period 3.64 years, Distance 173.2 million km).

31 Euphrosyne

31 Euphrosyne was discovered by James Ferguson in 1854; it is named after Euphrosyne, one of the Charities in Greek mythology. Amphitride is one of the kargest Main belt asteroids (Diameter 255.9 km, Orbit period 5.59 years, Distance 389.2 million km.).

32 Pomona

32 Pomona is a main belt asteroid. Pomona was discovered by H. Goldschmidt on October 26, 1854. It is named after Pomona, the Roman goddess of fruit trees.  (Diameter 80.8 km, Orbit period 4.16 years, Distance 228 million km).

33 Polyhymia

Polyhymnia was discovered by J Chacomac in 1854; it is named after Polyhymnia, the Greek Muse of sacred hymns. Polyhymnia is a Main belt asteroid (Diameter 50-120 km, Orbit period 4.85 years).

34 Circe

34 Circe is a large, very dark Main Belt asteroid. It was discovered by J Chacomac in 1854; it is named after Circe, a goddess in the Greek mythology.  (Diameter 113.5 km, Orbit period 4.40 years, Distance) 341.1 million km.)

35 Leukothea

35 Leukothea is a large dark Main Belt asteroid. It was discovered by R. Luther on April 19th 1855; it is named after Leukothea, a sea goddess in the Greek mythology.  (Diameter 103.1 km, Orbit period 5.17 years, Distance) 384.1 million km.)

36 Atalante

36 Atalante is a large, dark Main Belt asteroid. It was discovered by H Goldschmidt in 1855; it is named after Atalante, a horeine in the Greek mythology.  (Diameter 105.6 km, Orbit period 4.55 years, Distance 230.1 million km.)

37 Fides

37 Fides is a large Main Belt asteroid. It was discovered by R Luther in 1855; it is named after Fides, the Roman goddess of loyalty.  (Diameter 108.3 km, Orbit period 4.29 years, Distance 203.1 million km.)

38 Leda

38 Leda was discovered by J Chacomac in 1856; it is named after Leda, the mother of Helen of Troy in Greek mythology. Leda is a large, dark Main belt asteroid (Diameter 115.9 km, Orbit period 4.54 years, Distance 1.49 million km).

39 Laetitia

39 Laetitia  was discovered by J Chacornac in 1856; it is named after Laetitia, a Roman goddess of gaiey. It is a Main belt asteroid (Diameter 149.5 km, Orbit period 4.61 years, Distance 254 million km).

40 Harmonia

40 Harmonia is a large main belt asteroid. It was discovered by H. Goldschmidt on March 31, 1856 and named after Harmonia, the Greek goddess of harmony. The name was chosen to mark the end of the Crimean War. (Diameter 107.6 km, Orbit period 3.41 years, Distance 230.6 million km).

41 Daphne

41 Daphne is a large main belt asteroid. This dark-surfaced body is likely composed of primitive carbonaceous chondrites. It was discovered by H. Goldschmidt on May 22nd, 1856 and named after Daphne, the nymph in Greek mythology who was turned into a laurel tree. (Diameter 174 km, Orbit period 4.6 years, Distance 374.3 million km).

42 Isis

42 Isis is a large main belt asteroid. It was discovered by N R Pogson on May 23rd, 1856 and named after Isis, the Greek name of an Egyptian goddess. (Diameter 100.2 km, Orbit period 3.82 years, Distance 301.3 million km).

43 Ariadne

43 Ariadne is a large, bright, main belt asteroid. It was discovered by N R Pogson on April 15th, 1857 and named after the Greek heroine Ariadne. (Diameter 95 x 60 x 50 km, Orbit period 3.27 years, Distance 220.8 million km).

44 Nysa

44 Nysa is a quite large and very bright main belt asteroid. It is the brightest member of the Nysa asteroid family. It is classified as a rare class E asteroid. It was discovered by H Goldschmidt on May 27th, 1857 and named after Nysa in Greek mythology. (Diameter 70.6 km, Orbit period 3.77 years, Distance 183.3 million km).

45 Eugenia

45 Eugenia is a large Main belt asteroid. It is famed as one of the first asteroids to be found to have a moon orbiting it. Eugenia was discovered in 1857 by Hermann Goldschmidt.  (Diameter 134 miles, Orbit period 4.49years, Distance 150 million miles).

46 Hestia

Hestia is a large, dark Main belt asteroid: it is also the primary body of the Hestia asteroid clump. It was discovered by N R Pogson in 1857 (Diameter 124.1 km, Orbit period 4.02 years, Distance 194.5 million  km).

47 Aglaja

47 Aglaja is a large and dark Main belt asteroids. Kalyso was discovered on September 15th by R. Luther; it is named after Aglaea, one of the Charities in Greek Mythology.  (Diameter 127 km, Orbit period 4.89 years, Distance 360.6 million km).

48 Doris

48 Doris is one of largest Main belt asteroids. Doris was discovered in 1857 by Hermann Goldschmidt.  (Diameter 221.8 km, Orbit period 5.48years, Distance 334.1 million km).

49 Pales

49 Pales a large, dark Main belt asteroid. Pales was discovered on September 19th 1857 by Hermann Goldschmidt.  Pales is the goddess of shepherds in Greek mythology. (Diameter 149.8 km, Orbit period 5.42years, Distance 344.8 million km).

50 Virginia

50 Virginia is a large, very dark Main belt asteroid. It was discovered by J. Ferguson on October 4, 1857. R. Luther found it independently on October 19, and his discovery was announced first. The reason for Virginia's name is not known.  (Diameter 99.8 km, Orbit period 4.31 years, Distance 373.5 million km).

51 Nemausa

51 Nemausa is a large, very dark Main belt asteroid. It was discovered by A. Laurent in 1858.  (Diameter 147.9 km, Orbit period 3.64 years, Distance 224.5 million km).

52 Europa

52 Europa a large, dark Main belt asteroid. Pales was discovered on February 4th 1858 by Hermann Goldschmidt.  Europa is the seventh largest asteroid and contains a little less than 2% of the mass of the main belt. (Diameter 289 km, Orbit period 5.46 years, Distance 377.9 million km).

52 Europa in Virgo Meade LX200GPS 10" f6.3 Starlight Xpress MX7C CCD Camera 28 secs AstroArt + Paintshop Pro X Dorridge, UK  21:48 UT 2006-06-21

53 Kalypso

53 Kalypso is a large and very dark Main belt asteroids. Kalyso was discovered on April 4th 1858 by R. Luther.  (Diameter 115.4 km, Orbit period 4.24 years, Distance 186.1 million km).

54 Alexandra

Alexandra is a very large, darkMain belt asteroid. It was discovered by H Goldschmidt in 1858 (Diameter 165.8 km, Orbit period 4.47 years, Distance 289.3 million  km).

55 Pandora

55 Pandora is a quite large and very bright Main belt asteroid. Pandora was discovered by G. Searle on September 10, 1858. It was his first and only asteroid discovery. It is named after Pandora, the first woman in Greek mythology.  (Diameter 66.7 km, Orbit period 4.58years, Distance 216.0 million km).

56 Melete

56 Melete is a large dark Main belt asteroid. Melete was discovered by H. Goldschmidt on September 9th 1857. Melete is an unusual class P asteroid, composition probably organic rich silicates, carbon and anhydrous silicates with possible internal water ice. It is named after Melete, the Muse of meditation in Greek mythology.  (Diameter 113.2 km, Orbit period 4.18 years, Distance 350.9 million km).

57 Mnemosyne

57 Mnemosyne is a large Main belt asteroid. Mnemosyne was discovered by R. Luther on September 22nd 1859. Melete is an S-type asteroid. It is named after Mnemosyne, a Titaness in Greek mythology.  (Diameter 112.6 km, Orbit period 5.59 years, Distance 376.4 million km).

58 Concordia

58 Concordia is a quite large Main belt asteroid. Concordia was discovered by R. Luther on March 24th 1860. Concordia is a class C asteroid, its surface is dark and it's composition is likely to be carbonaceous. It is named after Concordia, the Roman goddess of harmony.  (Diameter 93.4 km, Orbit period 4.44 years, Distance 252.9 million km).

59 Elpis

59 Elpis is a very large Main belt asteroid. Concordia was discovered byJ. Chacomac on September 12th 1860. Elpis is a class C asteroid, its surface is dark and it's composition is carbonaceous. It is named after Elpis, a personification of hope.  (Diameter 164.8 km, Orbit period 4.47 years, Distance 371.7 million km).

60 Echo

60 Echo is a quite large Main belt asteroid. Echo was discovered by James Ferguson on September 14th 1860. Concordia is a class S asteroid, its surface is bright in color and it is probably a mixture of iron-nickel metals and silicate rock. It is named after Echo, a nymph in Greek mythology.  (Diameter 60.2 km, Orbit period 3.70 years, Distance 197.5 million km).

61 Danae

61 Danae is a quite large, rocky Main belt asteroid. Echo was discovered by H Goldschmidt on September 9th 1860. It is named after Danae, the mother of Perseus, in Greek mythology.  (Diameter 82.0 km, Orbit period 5.15 years, Distance 359.0 million km).

62 Erato

62 Erato is a large and dark, probably carbonaceous main belt asteroid. It is a member of the Themis asteroid family. Erato is the first asteroid to have been credited with co-discoverers, Oskar Lesser and Wilhelm Forster, who discovered it on September 14, 1860. It was their first and only asteroid discovery. It is named after Erato, the Muse of lyric poetry in Greek mythology.  (Diameter 95.4 km, Orbit period 5.51 years, Distance 395.7 million km).

63 Ausonia

63 Ausonia is a large main belt asteroid. It was discovered it on February 10^th, 1861 by A de Gasparis. Ausonia is an alternative name for Italy.   (Diameter 103.1 km, Orbit period 3.71 years, Distance 234.7 million km).

64 Angelina

64 Angelina is a quite large Main belt asteroid. It belongs to the less common spectral class E. It was discovered on March 4, 1861 by a prolific comet discoverer, E. W. Tempel. It was first of his five asteroid discoveries.  (Diameter 85 - 190 km, Orbit period 4.39 years, Distance 232.9 million km).

65 Cybele

65 Cybele is one of the largest asteroids in the Main belt. Cybele was discovered by Ernst Tempel on March 8th 1861. Cybele is a class C asteroid, its surface is dark and it's composition is likely to be carbonaceous. It is named after Cybele, the earth goddess.  (Diameter 237.3 km, Orbit period 6.73 years, Distance 423.1 million km).

66 Maja

66 Maja is a dark large asteroid in the Main belt. Maja was discovered by Horace Tuttle on April 9th 1861. It is named after Maia, one of the Pleiades in Greek mythology.  (Diameter 72.8 km, Orbit period 4.30 years, Distance 407.8 million km).

67 Asia

67 Asia is a bright Main belt asteroid. Asia was discovered by Norman Pogson on April 17th 1861. It is named after Asia, a Titaness in Greek mythology, but also after the continent, because the  asteroid was the first to be discovered from Asia.  (Diameter 58.1 km, Orbit period 3.77 years, Distance 281.6 million km).

68 Leto

68 Leto is a large Main Belt asteroid. Cybele was discovered by Robert Luther on April 29, 1861. It is named after Leto, the mother of Apollo and Artemis in Greek mythology.  (Diameter 122.6 km, Orbit period 4.65 years, Distance 220.8 million km).

69 Hesperia

Hesperia is a large, metal rich, Main belt asteroid. Hesperia was discovered by Giovanni Schiaparelli in 1861 (Diameter 86 miles, Orbit period 5.14 years).

70 Panopaea

Panopaea is a large, dark, primitive carbonaceous C-type, Main belt asteroid. It was discovered by H Goldsmidt in 1861 (Dimensions 122.2 km, Orbit period 4.23 years, Distance 330.3 million  km).

71 Niobe

71 Niobe  is a large Main belt asteroid. Niobe was discovered by Robert Luther in 1861 (Diameter 83.4 km, Orbit period 4.57 years, Distance 233.4 million km).

72 Feronia

72 Feronia  is a large, dark Main belt asteroid. Feronia was discovered by C H F Peters in 1861 (Diameter 86.1 km, Orbit period 3.14years, Distance 159.4 million km).

73 Kyltia

73 Klytia  is a Main belt asteroid. Klytia was discovered by Horace Tuttle in 1862. (Diameter 44.4 km, Orbit period 4.35 years, Distance 260.4 million km).

74 Galatea

Galatea is a large, dark, Main belt asteroid. It was discovered by Ernst Tempel in 1862 (Dimensions 118.7 km, Orbit period 4.63 years, Distance 250.3 million  km).

75 Eurydike

75 Eurydike  is a Main belt asteroid. It has an M-type spectrum and a relatively high albedo and may be rich in nickel-iron. Eurydike was discovered by C H F Peters on September 22nd 1862. (Diameter 55.7 km, Orbit period 4.38 years, Distance 150.2 million km).

76 Freia

76 Freia  is a very large Main Belt asteroid. It orbits in the outer part of the asteroid belt and is classified as a Cybele asteroid. Freia was discovered by Heinrich d'Arrest on October 21st. 1862. (Diameter 183.7 km, Orbit period 6.31 years, Distance 366.2 million km).

77 Frigga

77 Frigga  is a very large, M-type, possibly metallic Main Belt asteroid. Frigga was discovered by C H F Peters on November 12th. 1862. (Diameter 69.2, Orbit period 4.36 years, Distance 354.3 million km).

78 Diana

78 Diana  is a large and dark Main Belt asteroid. It was discovered by R Luther in 1863. (Diameter 120.6 km, Orbit period 4.24 years, Distance 165.2 million km).

79 Eurynome

79 Eurynome  is a large, bright Main belt asteroid. It is composed of nickel-iron metals and silicate rocks. Eurynome was discovered by J.C. Watson on September 14th 1863. (Diameter 66.5 km, Orbit period 3.82 years, Distance 211.3 million km).

80 Sappho

Sappho is a quite large main belt asteroid. It was discovered by Norman Pogson on May 2, 1864 and is named after Sappho, the Greek poet. (Diameter 78.4 km, Orbit period 3.48 years, Distance 278.5 million km).

81 Terpsichore

81 Terpsichore is a large and very dark main belt asteroid. It has most likely a very primitive carbonaceous composition. It was found by the prolific comet discoverer Ernst Tempel on September 30, 1864. It is named after Terpsichore, the Muse of dance in Greek mythology. (Diameter 119.1 km, Orbit period 4.82 years, Distance 338.5 million km).

82 Alkmene

Alkmene is a Main belt asteroid. It was discovered by R Luther in 1864. The lightcurve data suggests suggests a satellite. (Diameter 61 km, Orbit period 4.58 years, Distance 294.8 million  km).

83 Beatrix

Beatrix is a quite large asteroid orbiting in the inner part of the main belt asteroid. It was discovered by Annibale de Gasparis in April 1865.  (Diameter 81.4 km, Orbit period 3.79 years, Distance 239.9 million  km).

84 Klio

Klio is a quite large and very dark Main belt asteroid. It was discovered by R Luther in 1864. (Diameter 79.2 km, Orbit period 3.63 years, Distance 177.2 million  km).

85 Io

Io is a large and dark-colored Main belt asteroid. It is probably a primitive body composed of carbonates. Like 70 Panopaea it orbits within the Eunomia asteroid family but it is most likely not related to the shattered parent body. It was discovered by C. H. F. Peters on September 19, 1865 and named after Io, a lover of Zeus in Greek mythology. Io is also the name of the volcanic satellite of Jupiter. (Diameter 154.8 km, Orbit period 4.32 years, Distance 350.8 million km).

86 Semele

Semele is a very large, dark Main belt asteroid; discovered by Friedrich Tietjen in 1866 (Diameter 75 miles, Orbit period 5.51years).

87 Sylvia

87 Sylvia is one of the largest Main belt asteroids; discovered by N R Pogson in 1866. It is a member of the Cybele group located beyond the core of the belt.  Sylvia is remarkable for being the first known asteroid to possess more than one moon. (Diameter 385 x 265 x 10 km, Orbit period 6.52 years, Distance 413.3 million km).

88 Thisbe

88 Thisbe is one of the largest main belt asteroids. It was discovered by C. H. F. Peters on June 15, 1866 and named after Thisbe, heroine of a Roman fable. An occultation of a star by Thisbe was observed on October 7, 1981. Results from the occultation indicate a larger than expected diameter of 232 km.  (Diameter 232.0 km, Orbit period 4.60 years, Distance 265.2 million km).

89 Julia

89 Julia is a large main belt asteroid. It is likely composed of silicate rock and nickel-iron metals. It was discovered by a French astronomer Édouard Stephan on August 6, 1866. It was first of his two asteroid discoveries; the other was 91 Aegina.   (Diameter 151.5 km, Orbit period 4.07years, Distance 197.4 million km).

90 Antiope

Antiope is a Main belt asteroid. It was discovered by R Luther in 1866.  In 2000, using adaptive optics at the Keck Telescope on Mauna Kea it was discovered that Antiope is in fact a double asteroid. It consists of two individual bodies (the "secondary" is designated S/2000 (90) 1), each about 110±16 km across, separated by only 170 kilometers, orbiting around a common centre. (Diameter 110 +/- 16 km each component, Orbit period 5.61 years, Distance 331.1 million  km). More recent observations with the European Southern Observatory’s 8-metre Very Large Telescope have taken the observations to the next level. The observatory has helped to reveal 90 Antiope as two egg-shaped piles of rubble orbiting one another. Each asteroid is roughly 86 km (53 miles) in diameter, and they’re separated by only 171 kilometres (106 miles).

91 Aegina

Aegina is a Main belt asteroid. It was discovered by Edouard Jean-Marie Stephan on November 4th 1866.  Its surface coloring is very dark and the asteroid has probably a primitive carbonaceous composition. The asteroid's name comes from Angina, a Greek mythological figure associated with the island of the same name. (Diameter 109.8 km, Orbit period 4.71 years, Distance 289.0 million  km). 

92 Undina

92 Undina is a large main belt asteroid. It has an unusually high albedo and an M-type spectrum. It was discovered by C H F Peters on July 7th, 1867. Undina is a member of the Veritas asteroid family, which formed some eight million years ago.    (Diameter 126.4 km, Orbit period 5.70 years, Distance 368.8 million km).

93 Minerva

93 Minerva is a large main belt asteroid. It is probably a C-type asteroid of carbonaceous composition. It was discovered by J C Watson on August 24, 1867. Minerva was the goddess of wisdom.    (Diameter 146 km, Orbit period 4.57years, Distance 462.4 million km).

94 Aurora

Aurora is one of the largest Main belt asteroids. It is very dark, darker than soot. It was discovered by J C Watson in 1867; Aurora is the Roman goddess of the dawn. (Diameter 127 miles, Orbit period 5.63 years).

95 Arethusa

95 Arethusa is a large main belt asteroid. It is of carbonaceous composition. It was discovered by Robert Luther on November 23, 1867. There are several Arethusas in Greek Mythology.    (Diameter 136 km, Orbit period 5.38 years, Distance 299.6 million km).

96 Aegle

Aegle is a very large main belt asteroid. It has a dark surface and is probably a primitive carbonaceous composition. It was discovered by Jerome Coggia in 1868. (Diameter 127 miles, Orbit period 5.63 years, Distance 407 million km).

97 Klotho

97 Klotho is a  large main belt asteroid. It was discovered by Ernst Tempel in 1868. (Diameter 82.8 km, Orbit period 4.36 years, Distance 193.4 million km).

98 Ianthe

98 Ianthe is a  large main belt asteroid. It is very dak and is composed of carboantes. It was discovered by C H F Peters on Aptil 18^th 1868 from Clinton, New York. (Diameter 104.5 km, Orbit period 4.40 years, Distance 274.6 million km).

Below is an animation of 98 Ianthe in Triangulum. It shows the movement of the asteroid against the star background over 115 minutes. This project was only taken as we had a super clear night BUT a full moon. Quality of images is not good because of adjacent moon but it was something to try.

99 Dike

99 Dike is a  large, dark main belt asteroid. It was discovered by Alphonse Borrelly in 1868. (Diameter 71.9 km, Orbit period 4.35 years, Distance 194.3 million km).

100 Hekate

100 Hekate is a  large main belt asteroid. It orbits in the same region of space as the Hygiea asteroid family, however it is actually an unrelated interloper. Its albedo of 0.19 is too high, and it is of the wrong spectral class to be part of the dark carbonaceous Hygiea family. It was discovered by J C Watson in 1868. (Diameter 89 km, Orbit period 5.44 years, Distance 396.9 million km).

Meteor Crater, Arizona

Asteroids can make a big hole in the ground if they happen to collide with the Earth. Meteor Crater, 35 miles east of Flagstaff, Arizona, is a gigantic hole in the middle of the high desert. The crater is nearly a mile wide and 570 feet deep and was formed some 50,000 years ago. 30 tons of meteoric iron have been found within 10 miles of the crater. Recent theories suggest that the large meteorite fragmented before impact as it passed through the Earth's atmosphere.

Meteor crater is worth a visit if you are in Arizona: the scale of the impact can only be imagined if you stand on the rim. No access is allowed down into the crater, which is a protected area, but walks along the rim are in managed groups.

If you get that way then the Lowell Observatory is in nearby Flagstaff where evening viewing through Lowell's telescope is provided - see if you can see the canals on Mars! More details on my Mars page; see Lowell Observatory.

Meteorites

Much of our understanding about asteroids comes from examining pieces of space debris that fall to the surface of Earth. Asteroids that are on a collision course with Earth are called meteoroids. When a meteoroid strikes our atmosphere at high velocity, friction causes this chunk of space matter to incinerate in a streak of light known as a meteor. If the meteoroid does not burn up completely, what's left strikes Earth's surface and is called a meteorite.

Of all the meteorites examined, 92.8 percent are composed of silicate (stone), and 5.7 percent are composed of iron and nickel; the rest are a mixture of the three materials.

Pieces of meteorites are available for purchase; I purchased a piece of the 12^th Feb 1947 Sikhote Alin meteorite. This is an iron-nickel coarsest octahedrite which fell in Siberia. My piece weighs only 24.5gm but adds much interest to those who see an asteroid through the telescope and can then touch a specimen from a similar object.

My first meteorite was purchased at a Leeds Astromeet from York Meteorites. I have purchased further meteorites from sites on

Reference

O. Richard Norton's book, Rocks from Space, is an attractive and easily read book giving an introduction to all hazards arriving on Earth from Space - asteroids, comets and meteorites and their impact on the surface.

The book also covers the 'Meteorite Hunters', lists the authenticated impact craters worldwide and provides a useful glossary.

It is well illustrated and has good diagrams and cartoons.

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