Spica / Alpha Virginis Star Facts (Type, Distance, Magnitude, Age, Mass, Colour, Location and more)

Facts

Spica (Alpha Virginis) is the brightest star in the constellation of Virgo, The Virgin. Based on the spectral type (B1V), Spica's colour is blue, which means that the star is one of the hottest stars in the Universe, hotter than our star.

In addition to being its constellation's brightest star, it is the 16th in the night sky based on the Hipparcos 2007 apparent magnitude. Spica is a naked eye star and can be seen on a clear night without binoculars or a telescope.

Spica is a Spectroscopic Binary Star, these are Binary Star System where it is hard to differentiate without the use of equipment. The secondary star (Spica B) orbits its main star at a close distance of 0.12 A.U. which is considerably closer to the main star than what Mercury orbits at (0.4) . A complete orbit around the barycentre is four days. The barycentre is the centre of gravity for the two stars. The smaller one does not orbit the larger one, like our planets orbit the Sun.

Spica is the traditional/proper name for the star, which means "Head of the grain" in English. Alpha Virginis is the Bayer Designation for the star. Typically, the brightest star in the constellation is classified as Alpha. A list of additional names and identifications is in the facts list at the bottom of the page.

Spica is a Beta Cephei type variable star. Variable stars are stars whose size and/or brightness changes over time. Spica brightness ranges from a magnitude of 0.907 to 0.866 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 4.0145 days.

Location

The location of the Spica in the night sky is determined by the right ascension (R.A.) and declination (Dec.). These are equivalent to the longitude and latitude of Earth. The Right Ascension (Longitude) is expressed in time (hh:mm:ss) and is how far the star is along Earth's celestial equator. If the R.A. is positive, then it is eastwards and vice versa.

The Declination (Latitude) is how far north or south the object is compared to the celestial equator and is expressed in degrees. If the value is positive, it is north of the celestial equator. For Spica, the location is 13h 25m 11.60 and -11° 09' 40.5.

Based on the location of Virgo, Spica can be located in the equatorial region of the celestial sky. The celestial hemisphere is equivalent to the hemispheres on Earth. Being in the equatorial region, Spica can be seen in both terrestrial hemispheres, but there is a caveat depending on how far south and north you are. Virgo is on the Ecliptic. Of the major stars in the constellation, Spica has the distinction of being the only one that is south of the Ecliptic.

The Ecliptic is Earth's path as it orbits the Sun. As the Earth is titled, we have Celestial and Ecliptic hemispheres, which can be different for a star.

Physical Properties

Colour and Type

Spica spectral type of B1V means its colour and type is blue main sequence star. Although some places state the spectral type is B1 III-IV, my spectral type comes from Hipparcos. There is no relationship between colour and size. For example, a red star can be large or small. Small stars are more energy efficient than larger stars and live longer.

Temperature

Spica's effective temperature is 25,300 Kelvin, hotter than our Sun's effective temperature, 5,777 Kelvin. The uncertainty range for the effective temperature is between -24800 and +25800.

Luminosity

Luminosity is the amount of energy a star pumps out relative to the amount that our star, the Sun, gives out. Our star, the Sun's value, is 1. The spica luminosity figure of 4.312 is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012. The star generates more energy than our star.

Size (Radius)

The primary Spica radius has been calculated as being 7.47 times bigger than the Sun. The Sun's radius is 695,800km. Therefore, the Spica's radius is an estimated 5,197,626 km. If you need the star's diameter, multiply the radius by 2. The error range for the radius is between 6.93000 and 8.01000.

The second Spica star is half the size of the larger one at about 3.5 radii. It is still much larger than our star.

Magnitude (Apparent / Absolute)

A number represents a star’s magnitude, whether apparent/visual or absolute. The smaller the number, the brighter the star is. Our Sun is the brightest star and therefore has the lowest magnitudes, -26.74. A faint star will have a high number.

Spica's apparent magnitude is 0.98, a measure of the star's brightness as seen from Earth. Apparent Magnitude is also known as Visual Magnitude.

Using the 1997 parallax value, Spica's absolute magnitude is -3.55. Using the 2007 parallax value, Spica's absolute magnitude is -3.44. Absolute Magnitude is the star's apparent magnitude from 10 parsecs or 32.6 light-years. The magnitude assumes nothing is between the object and the viewer, such as dust clouds. You would best use Absolute rather than Apparent Magnitude to compare different stars' brightness.

Spica is visible from Earth without needing binoculars or a telescope. The lower the Apparent Magnitude of a star or other object is, the easier it is to see in the night sky. An object with a magnitude greater than 6.5 cannot be seen without a telescope or other device.

Meteor Showers

One meteor showers radiate from a location near Spica during the year.

• Alpha Virginids Meteor Shower March 10-May 6 (Peak: 7th Apr).

Distance from Earth

Spica distance from Earth is 262.19 light-years away from Earth or 80.39 parsecs. If you want that in miles, it is about 1,541,316,786,595,010.706, based on 1 Ly = 5,878,625,373,183.61 miles. The distance is calculated using the parallax from the original Hipparcos data released in 1997, which is 12.44000.

In 2007, Hipparcos data was revised with a new parallax of 13.06000, which puts the Spica distance from Earth as 249.74 light-years or 76.57 parsecs. It should not be taken as though the star is moving closer or further away from Earth. It is purely that the distance was recalculated.

An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times the star is from the Earth compared to the Sun. When you use the 2007 distance, Spica is roughly 15,793,586.163 Astronomical Units from the Earth/Sun, give or take a few.

Spica Galacto-Centric Distance is 7,366 Parsecs or 24,025.192 Light Years. The Galacto-Centric Distance is the distance from the Spica to the Centre of the Galaxy, Sagittarius A*.

How long it will take to get to Spica

The time it takes to travel to Spica depends on how fast you are going. U.G. has done some calculations as to how long it will take to go at differing speeds. A note about the calculations: when I am talking about years, I am talking about non-leap years only (365 days).

The New Horizons space probe is the fastest one that we have sent into space at the time of writing. Its primary mission was to visit Pluto, which, at the time of launch (2006), Pluto was still a planet.

Mach 1 is the speed of sound; Mach 2 is twice the speed. |Before retiring, Concorde was the fastest commercial aeroplane and the only passenger jet that could do Mach 2.

You may need to swipe the table to see the information on some small screens. If you need an explanation, hover over the bold text. These methods assume you have unlimited fuel and travel at a constant speed.

• Walking - 41,869,949,231.615
• Car - 2,392,568,527.521
• Airbus A380 - 227,554,071.911
• Mach 1 - 218,280,416.551
• Mach 2 - 123,692,612.206
• New Horizons - 4,601,093.322
• Speed of Light - 249.74