Arcsecond

An arcsecond (second of arc), represented by the symbol ${\displaystyle ''}$, is a unit of angle used in mathematics and astronomy. An arcsecond is 1/60th of an arcminute (minute of arc), which in turn is 1/60th of a degree. Therefore, an arcsecond is equal to 1/3600th of a degree, meaning that there are 360 × 60 × 60 = 1,296,000 arcseconds in a full circle.

1m @ 200km

One milliarcsecond (mas) is a thousandth (1/1000th) of an arcsecond. So there are 1,296,000,000 milliarcseconds in a full circle. The red supergiant stars Antares, Betelgeuse, Mu Cephei, VV Cephei A, and VY Canis Majoris all have angular diameters (apparent sizes in the sky) of more than 10 milliarcseconds, when seen from Earth.

1mm @ 200km

Related pages

• Radian

References

1. ↑ "List of Geometry and Trigonometry Symbols". Math Vault. 2020-04-17. Retrieved 2020-08-31.
2. 1 2 Weisstein, Eric W. "Arc Second". mathworld.wolfram.com. Archived from the original on 2023-03-17. Retrieved 2020-08-31.
3. ↑ Weisstein, Eric W. "Arc Minute". mathworld.wolfram.com. Archived from the original on 2021-04-24. Retrieved 2020-08-31.
4. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2011-07-15. Retrieved 2023-09-06.{{cite web}}: CS1 maint: archived copy as title (link)

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