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The Naked-eye Planets: Asteroids

Vesta: The Only Naked-eye Asteroid (2011 article)

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Finder chart for asteroid 4 Vesta and dwarf planet 1 Ceres during Vesta's period of naked-eye visibility in Virgo between early March and late May 2014 (Copyright Martin J Powell 2014)

Finder Chart showing the position of asteroid 4 Vesta and the dwarf planet 1 Ceres at 5-day intervals from early March to late May 2014, the period during which Vesta was technically visible to the naked-eye (i.e. it was brighter than apparent magnitude +6.5). The two bodies were positioned in North-eastern Virgo during this time, North of the star Heze (Greek lower-case letter 'zeta' Vir or Zeta Virginis, mag. +3.4) and East of the star Minelauva or Auva (Greek lower-case letter 'delta' Vir or Delta Virginis, mag. +3.4). A Southern hemisphere view of the chart can be found here and a printer-friendly (greyscale) version can be obtained for Northern and Southern hemisphere views. The faintest stars shown on the chart are magnitude +8.5. A night sky photograph of the constellation Virgo can be found here (the faintest stars visible in the photograph are about mag. +7.5).

 

Rotation of asteroid 4 Vesta, as imaged by NASA's 'Dawn' spacecraft, based on an 18MB video by NASA (Credit: NASA/JPL-Caltech/UCLA/PSI/MPS/DLR/IDA)

A full 5-hour rotation of Vesta as imaged by NASA's Dawn spacecraft. The animation was produced by the author using captures from NASA's 18 MB video showing Hydrogen Spots on Vesta (NASA / JPL-Caltech / UCLA / PSI / MPS / DLR / IDA)

Northern hemisphere observers can easily find Virgo from The Big Dipper (Plough) asterism using the method shown here. Southern hemisphere observers should use the Mini-AstroViewer JavaScript utility here to help locate the constellation in their night sky. The planet Mars was also shining brightly in Southern Virgo during the period; its path in the night sky is shown on the Mars 2013-15 page.

 

Vesta reached opposition to the Sun on April 13th 2014, peaking at magnitude +5.8, when it was 1.2325 Astronomical Units from the Earth (114.5 million miles or 184.3 million kms). The asteroid would have been visible to the naked-eye from dark sky locations, however from urban locations binoculars would probably have been needed to see it. Vesta will next reach naked-eye visibility in May 2018 (further details of its past and future oppositions can be found here).

 

Ceres (pronounced 'SEER-ees') is included on the chart because it was coincidentally near Vesta in the night sky during this time (although it was below naked-eye magnitude throughout the period, reaching +7.0 at opposition on April 15th 2014). In fact, between early April and late July 2014 Vesta and Ceres were separated by less than 2 in the night sky.

 

Vesta and Ceres were in conjunction (at the same celestial longitude) on July 5th 2014 at 17h UT, when they were just 10' (0.16) apart. By this time Vesta had faded to magnitude +7.1 and Ceres had faded to +8.5 so they were both binocular objects. Their position on this date is indicated on the chart by the letters 'V' and 'C', about 1.5 to the South-west of Heze.

 

Vesta has been the subject of much scientific interest in recent years, having been observed at close range by NASA's Dawn space probe which orbited the asteroid between July 2011 and September 2012. The probe is now on its way to Ceres, which it will reach in March 2015 (see NASA article). The Herschel Space Observatory recently observed jets of water vapour streaming from the surface of Ceres - the first time water has been detected anywhere in the asteroid belt (see article in the Nature journal). Ceres was re-classified as a dwarf planet by the International Astronomical Union (IAU) in 2006; at 590 miles (950 kms) in diameter, it is the largest object in the asteroid belt.

 

Much of the star field in the chart should be easily contained within a binocular field of view (which typically ranges from 5 to 9). Right Ascension and Declination co-ordinates are marked around the border for cross-referencing in a star atlas. A 'clean' star map of this region (i.e. without tracks) can be obtained here and a printer-friendly version is here (for manually position-plotting). 

 

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The Naked-eye Planets: Asteroids

Appearance of the Naked-Eye Planets

Planetary Movements through the Zodiac

Star Charts showing Positions of the Planets:

Mercury

Venus

Mars

Jupiter

Saturn

Uranus

Neptune

Pluto


Credits

 


Copyright  Martin J Powell  February 2014


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