Asellus Borealis (γ Cancri) | Facts, Distance, Size, Mass & Formation

Asellus Borealis, designated as Gamma Cancri, is a multiple star system located in the zodiacal constellation of Cancer, the celestial crab.

Key Facts & Summary

Asellus Borealis is located at around 181 light-years / 55.6 parsecs away from the Solar System.
It is the fifth brightest star in the constellation of Cancer.
Asellus Borealis consists of a spectroscopic binary, designated Gamma Cancri A, and a single companion star, Gamma Cancri B.
The two components of Gamma Cancri A are designated as Gamma Cancri Aa, which is known as Asellus Borealis, and Gamma Cancri Ab.
Asellus Borealis has an apparent magnitude of 4.652, and an absolute magnitude of +1.1.
This star system has a radial velocity of around 28.7 km / 17.8 mi per second.
Asellus Borealis is a fast-spinning star, having a rotational velocity of around 86 km / 53.4 mi per second.
Gamma Cancri / Asellus Borealis is a white A-type subgiant star of spectral type A1IV.
This star has around 2.18 solar masses and 2.5 solar radii. It is five times bigger than our Sun.
Asellus Borealis is 36 times brighter than our Sun, while its surface average temperatures have been recorded at 8,800 K.
This star is almost twice as hot as our Sun.
The surface gravity on Asellus Borealis is 4.17 cgs.
Asellus Borealis is quite a young star, having an estimated age of around 171 million years. Our Sun, for comparison, is 4.6 billion years old.
The zodiacal constellation of Cancer is the 31^st largest constellation in the sky, stretching for around 506 square degrees.
It is however a faint constellation, being the second faintest out of the twelve zodiacal constellations. Asellus Borealis, the other stars and deep-sky objects in Cancer, are best seen during the month of March.

γ Cancri

Gamma Cancri is formally named as Asellus Borealis. The name comes from Latin, and it means “northern little donkey”. This named was approved by the IAU in 2016.

Gamma Cancri together with Delta Cancri, formed the Aselli, flanking the open cluster Praesepe, which is also known as the Beehive Cluster, or Messier 44.

Formation

Asellus Borealis / Gamma Cancri is a very young star that formed around 171 million years ago, from an interstellar medium of gas and dust.

Gravity pulled the swirling gas and dust together, and when it reached the right temperature, the fifth brightest star in the constellation of Cancer, Asellus Borealis, was born. It is unknown if the other stars near Asellus Borealis are related to one another.

Distance, Size, and Mass

Asellus Borealis is located at around 181 light-years / 55.6 parsecs away from Earth. It is visible through binoculars if the conditions are favorable.

Asellus Borealis is five times bigger than our Sun and more massive. This star has around 2.18 solar masses, or 218% of our Sun’s mass, and 2.5 solar radii, or 250% of our Sun’s radius.

Other Characteristics

Asellus Borealis is a white A-type subgiant star of spectral type A1IV. It has an apparent magnitude of 4.652, and an absolute magnitude of around +1.1.

The surface gravity on this star has been recorded at around 4.17 cgs, while its rotational velocity is at 86 km / 53.4 mi per second, quite fast for a star. It may be possible that this star has an unusual shape due to its speed, or a circumstellar disk of dust, which is typical of fast-spinning stars.

Asellus Borealis is 36 times brighter than our Sun, and it is much hotter, having surface average temperatures of around 8,800 K, or 1.5 times hotter than our Sun.

Star System

This star system consists of a spectroscopic binary star, designated as Gamma Cancri A, and a single companion star, designated as Gamma Cancri B.

Gamma Cancri A is made out of two components, the primary star, is named Asellus Borealis, and it is designated as Gamma Cancri Aa, and the companion star is designated as Gamma Cancri Ab. This star system has a radial velocity of around 28.7 km / 17.8 mi per second.

Location

Asellus Borealis / Gamma Cancri is located in the zodiacal constellation of Cancer, the celestial Crab. Cancer is the second faintest zodiacal constellation in the sky.

Asellus Borealis is situated near the famous open star cluster Messier 44, also known as the Beehive Cluster, or Praesepe. The cluster is situated in the middle of Asellus Borealis and Asellus Australis. In antiquity, Messier 44 was used as a weather gauge.

The constellation of Cancer is part of the zodiac family of constellations, and it is the 31^st largest constellation in the sky out of the 88 modern constellations.

There are many interesting stars and deep-sky objects in the zodiacal constellation of Cancer, such as Asellus Australis, Tarf, X Cancri, YBP 1194, the Messier 67 open cluster, Messier 44, the QSO J0842+1835 quasar, or the OJ 287 BL Lacertae objects, among many others.

The best time to view Asellus Borealis, the other stars, and deep-sky objects in the constellation of Cancer, is during the month of March when the constellation is the most prominent in the sky.

The Future

Asellus Borealis appears to be a stable star, and it will continue to be so for many millions of years. It is not massive enough to explode as a supernova when its time comes, and as such, Asellus Borealis may evolve into a white dwarf star in the last stages of its life.

Did you know?

Since Asellus Borealis is near the ecliptic, it can be occulted by the Moon, and, very rarely, by planets.
The Chinese know Asellus Borealis as Gui Xiu san – which translates to the Third Star of Ghost.
In Chinese astronomy, Gui Xiu – Ghost – is an asterism comprised out of Asellus Borealis, Asellus Australis, Theta Cancri, and Eta Cancri.
The stars of the constellation of Cancer, lie within the Vermillion Bird of the South – in Chinese astronomy.