Zosma Star Facts (Delta Leonis)

Zosma, also known as Delta Leonis (Bayer) is a main sequence star located in the constellation of Leo, The Lion. Zosma colour is blue - white, although not the hottest stars, they are considerably hotter than our own star which is white.

Zosma temperature range is between 7,500 and 10,000 Kelvin. Based on the spectral type (A4V) as we don't have the exact temperature', we can deduce that the surface temperature of Zosma is in the order of 7,500 and 10,000K based on the notes from Harvard University. To put this in context, the temperature of our Sun is about 5,778 Kelvin as said by Google.

Based on a parallax of 55.82, Zosma distance from Earth can be calculated at being 58.43 light years away or 17.69 parsecs.

Zosma is a naked-eye star, so you don't need a telescope or binoculars when you look up on a clear night. The lower the magnitude, the easier it will be to see it.

Zosma is a major star and forms part of the constellation.

Zosma is one of the brightest stars in the constellation of Leo. It is about 2.2x, or read it another way, twice as big as the Sun. Its name is Arabic for Girdle from where it gets its name from, i.e. its location in the constellation. It is one of the brightest in the night sky compared to the other stars but is not the brightest in Leo, that honour goes to Regulus. As it is travelling through the galaxy at a speed of 26.6km/s relative to the Sun, it will come close to the Sun in about 518,000 years when it will brighten in the night sky but not any where near as the Sun or Moon. ¹

Although Zosma is fourth brightest evident by the fact it is Delta, the fourth letter of the Greek constellation, it is brighter than the third star, Algieba which is a double star. Zosma is brighter than both stars but it falls in the pecking order because the sum of the brightness of the two Algieba stars is brighter than Zosma. It is a dying star and is over half way through its dying process. ²

Physical Properties

Zosma Colour and Spectral Type

Zosma spectral type of A4V which means its colour and type is blue - white main sequence star. 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.

Zosma 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. Zosma luminosity figure of 25.61 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.

Zosma Size (Radius)

Zosma radius has been calculated as being 2.14 times bigger than the Sun. The Sun's radius is 695,800km, therefore, the Zosma radius is an estimated 1,489,012 km. The error range for the radius is between 0.04000 and 0.04000.

Zosma Magnitude (Apparent / Absolute / Visible)

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

Zosma apparent magnitude is 2.56, which is a measure of the star's brightness as seen from Earth. Apparent Magnitude is also known as Visual Magnitude.

If you use the 1997 parallax value, Zosma' absolute magnitude is 1.32. If you use the 2007 parallax value, Zosma' absolute magnitude is 1.29. 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. To compare different stars' actual brightness, you would best use Absolute rather than Apparent Magnitude.

Zosma is a naked-eye star, that is one 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.

Zosma Distance from Earth

Zosma distance from Earth is 57.71 light-years away from Earth or 17.69 parsecs. If you want that in miles, it is about 339,255,470,286,426.133, 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 56.52000.

In 2007, Hipparcos data was revised with a new parallax of 55.82000, which puts the Zosma distance from Earth as 58.43 light years or 17.91 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 that the star is from the Earth compared to the Sun. When you use the 2007 distance, Zosma is roughly 3,694,176.939 Astronomical Units from the Earth/Sun give or take a few.

Zosma Galacto-Centric Distance is 7,405 Parsecs or 24,152.396 Light Years. The Galacto-Centric Distance is the distance from the Zosma to the Centre of the Galaxy which is Sagittarius A*.