La Hamal star, ancient reference to the equinoxIt is much more than the brightest point of the aries constellationFor millennia, it was a true landmark in the sky for astronomers, navigators, priests, and farmers, to the point of becoming a kind of "cosmic marker" of the arrival of spring in the Northern Hemisphere. Although its equinoctial role has shifted today, its historical, scientific, and symbolic importance remains enormous.
Today, Hamal is being studied as a nearby giant orange with a giant planet orbiting around it, but also as a key piece for understanding the precession of the equinoxes, the so-called "First Point of Aries," and the evolution of celestial maps. Furthermore, it is intimately linked to the constellation of Aries, the zodiac, legends such as that of the Golden Fleece, and the way ancient cultures looked to the sky to measure time.
What is Hamal and where is it located in heaven?
The star Hamal (Alpha Arietis) is the brightest of AriesAries, the Ram, is a zodiacal constellation located between Pisces and Taurus in the sky. Its name comes from the Arabic "ħamal," which literally means "ram," and was originally used to refer to the entire constellation, leading to some confusion between the individual star and the complete celestial figure.
Within the Aries star group, Hamal, Sheratan, and Mesarthim draw the ram's headforming a very characteristic, slightly curved line. These three stars are used as a visual reference to locate the constellation, especially on clear autumn and winter nights in the Northern Hemisphere.
If we're talking about visibility, Hamal can be easily observed with the naked eye It is visible from mid-latitudes in the northern hemisphere and also from much of the southern hemisphere. Its apparent magnitude is around 2.0, making it a prominent star in relatively dark skies, even in areas with some moderate light pollution.
Regarding their movement throughout the year, Hamal appears towards the east on November nightsIt rises to high positions in the sky during January and heads towards the western horizon throughout March. In April it practically disappears from the night sky as it gets too close to the Sun, only to reappear again from June onwards, but in the dawn sky.
From the point of view of spatial position, Hamal is located about 66 light-years from Earth., a relatively short distance in galactic terms, which explains why we can characterize its physical properties and environment, including its known planet, with considerable accuracy.
Origin of the name and traditional names
Name Hamal comes from classical Arabic حمال (ħamal), which translates as "ram," was associated in that tradition with the constellation of Aries as a whole. Because of this, it is not uncommon to find references in ancient texts where the term is used for both the constellation and its main star.
In some Arabic manuscripts, Hamal is also mentioned as راس حمل (rās al-ħamal)This expression can be translated as "the head of the ram." This name fits very well with its location within the figure of Aries, since it forms, along with Sheratan and Mesarthim, precisely the head of the animal in traditional celestial charts.
The correspondence between Arabic name, Greek tradition and modern astronomy This reinforces the idea that this star was of enormous importance to the peoples of the Near East and the Mediterranean, both in religious and mythological contexts and in practical uses, such as the determination of seasons and the agricultural calendar.
Hamal as an ancient equinox star
During Antiquity, Hamal had a starring role as an equinoctial starBetween approximately 2000 BC and 100 BC, the Sun, as seen from Earth, was positioned opposite the stars of Aries, including Hamal, at the time of the spring equinox in the Northern Hemisphere. That is, when spring began, the Sun "rose" in the region of the sky occupied by the Ram.
At that time, The Sun and Hamal coincided at the March equinoxThus, the star served as a very clear marker of the beginning of the new agricultural cycle. It is not unreasonable to think that this coincidence reinforced the symbolic and ritual significance of Aries, the ram, and, by extension, of Hamal, in civilizations such as the Sumerian, Babylonian, and Greek.
Today things have changed: If we could see the stars in broad daylightWe would find that the Sun aligns with Hamal around April 24th, that is, almost a month after the spring equinox. This difference in time is not due to an error by the ancients, but to a well-known physical phenomenon: the precession of the equinoxes.
Precession of the equinoxes and displacement of the equinoctial point
The call The precession of the equinoxes is a slow "wobble" of the Earth's axis.similar to a spinning top losing speed. This movement causes the direction of Earth's rotational axis to vary over time, describing a circle on the celestial sphere with a period of approximately 26.000 years.
As a consequence of that precession, The celestial coordinates of the stars change very slowly And, above all, the point where the ecliptic (the apparent path of the Sun) crosses the celestial equator at the vernal equinox slowly shifts against the background stars. This causes the equinox to "travel" from one zodiacal constellation to another over the centuries.
About two millennia ago, The spring equinox occurred in the region of AriesThat's why, for centuries, many astronomers and astrologers placed the origin of the zodiac and certain coordinate references in this sign. However, due to precession, that equinoctial point is no longer in Aries, but in Pisces, and in the future it will eventually shift towards Aquarius and beyond.
This progressive shift explains why, although Hamal no longer directly marks the equinoxIt continues to be considered a star symbolically linked to spring and beginnings, since for a long stretch of human history it was the main reference for the start of the agricultural year and the growing light cycle.
The First Point of Aries and its astronomical importance
In astronomy, the The First Point of Aries is the point of intersection between the ecliptic and the celestial equator at the moment of the vernal equinox. It is, simply put, the “zero” of the right ascension coordinate, the celestial equivalent of the zero longitude meridian (Greenwich) on Earth.
Originally, This point was located in the constellation of AriesHence its name and the historical association between the spring equinox and Aries. At that time, when many of the foundations of classical astronomy were being established, it made perfect sense to call it that, since the Sun did indeed enter Aries precisely at the equinox.
However, precession has been slowly shifting that point across the zodiac, so that Currently, the First Point of Aries is located in the constellation of Pisces.Even so, due to tradition and convenience, the historical name is retained, although it no longer coincides with the constellation that gave rise to it.
In practice, The First Point of Aries functions as a zero celestial meridian for right ascension, which allows for the consistent definition of equatorial coordinates for cataloging stars, nebulae, galaxies, and any other astronomical object. The choice of this point as a reference is forever linked to the ancient significance of Aries and, by extension, to stars like Hamal.
Physical characteristics of Hamal
From an astrophysical point of view, Hamal is a giant orange star It is generally classified as K1 III or K2 III in the spectral system. The "III" notation indicates that it is an evolved giant that has left the main sequence after exhausting the hydrogen in its core.
According to the most precise spectroscopic studies, Hamal can be described as being of type K2III or K2IIICawhere the indication “Ca” refers to the prominent presence of calcium lines in its spectrum. This spectral detail provides information about the composition and physical conditions of its outer layers.
Regarding its dimensions, The diameter of Hamal is about 14,7 times larger than that of the SunThis value was obtained from the very precise measurement of its angular diameter, approximately 0,00680 arcseconds, and its known distance. Thanks to its size and relative proximity, it is one of the few stars for which the "limb darkening" effect has been clearly detected, whereby the edges of the stellar disk appear somewhat fainter than the central region.
If we're talking about intrinsic brilliance, Hamal emits approximately 90 times more light than the Sun when considering the entire radiation range, including the infrared portion. Its surface temperature is around 4.590 K, a typical value for K-type giants, which gives it that characteristic orange hue when observed with appropriate instruments.
As for its composition, Hamal exhibits a metallicity of around 60% of the solarThat is, it contains fewer heavy elements than our star. Its mass is estimated to be approximately twice the mass of the Sun, which fits with its evolutionary state: a star more massive than the Sun that has progressed more rapidly through its stellar life cycle.
Furthermore, astronomers have detected that Hamal shows a slight variability in its brightnesswith changes on the order of 0,05 magnitudes. This variation is not extreme, so it is still considered a stable star for naked-eye observation, but it is enough to interest those who study the physics of orange giants.
The exoplanet Alpha Arietis b
In 2011 it was announced discovery of an extrasolar planet orbiting around Hamaldesignated as Alpha Arietis b. It is a gas giant, detected using radial velocity techniques, which has turned this classical star into a planetary system of great interest for exoplanetology.
Observations indicate that Alpha Arietis b has a minimum mass of about 1,8 times that of Jupiter (with a margin of error of ±0,2 Jovian masses). Since it is an indirect method, the figure refers to a minimum mass, as it depends on the orbital inclination with respect to the line of sight from Earth.
Regarding its orbit, The planet travels along a path with a period of about 380,8 days (with an uncertainty of just a few tenths of a day). The semi-major axis of its orbit is around 1,2 astronomical units (AU), that is, it is located somewhat farther from its star than the Earth is from the Sun.
The orbit is not perfectly circular: It has an eccentricity of around 0,25 (±0,03), which implies that the planet moves significantly closer to and farther from Hamal throughout the local year. Since the star is already a giant much more luminous than the Sun, the conditions on this giant gas planet and any associated moons would be very different from those in our solar system.
| Companion (From the star outwards) |
Mass (MJ) |
Orbital period (days) |
Major semi-axis (UA) |
Eccentricity |
|---|---|---|---|---|
| Alpha Arietis b | > 1,8 ± 0,2 | 380,8 0,3 ± | 1,2 | 0,25 0,03 ± |
Aries in the sky: location and nearby objects
The constellation of Aries is relatively modest in size and brillianceHowever, it stands out for its historical and symbolic value. It is located west of the constellation Pegasus (the famous Autumn Square) and shares borders with Triangulum, Perseus, and Andromeda to the north; with Cetus to the south; with Pisces to the east; and with Taurus to the west.
Although Aries does not harbor no object included in the Messier catalogueIt contains some interesting deep-sky objects. Among them, the spiral galaxy NGC 772 stands out, having earned a special place in observation guides due to its size, its peculiar structure, and its interaction with a close companion.
NGC 772 is a large spiral galaxy located about 115 million light-years awayIts apparent magnitude is around 10,3, so it is not visible to the naked eye, but it is observable with medium-aperture amateur telescopes. Its physical diameter is estimated at about 240.000 light-years, which means it is almost twice the size of the Milky Way.
In the sky, NGC 772 has an approximate angular size of 7,4 by 4,9 arcminutesThis makes it appear as a relatively large oval patch in telescopes with good apertures. One of its most striking features is the presence of a dominant spiral arm, full of bright star-forming regions, which gives it a somewhat asymmetrical appearance, almost like a luminous apostrophe.
This peculiarity is largely due to the gravitational interaction with the neighboring galaxy NGC 770The other, more compact and closer, is located about 3,5 arcminutes away (approximately 108.000 light-years in three-dimensional distance). Both form an interacting system that was included in Arp's famous "Atlas of Peculiar Galaxies" with the number 78.
How to observe NGC 772 from Aries
To locate NGC 772 in the sky, a good reference point is the star γ Ari (Mesarthim). The galaxy is located only about 2,8 degrees east of this star, so by making a small jump with the telescope or with a good quality finder scope, it can be framed in the eyepiece.
Keep in mind that NGC 772 has a brightness comparable to that of the faintest galaxies in the Messier catalog (like M91 or M98), so it's not an easy object to see with small binoculars. Ideally, you should use a telescope with at least a 10 cm aperture to begin to perceive it as a faint, slightly irregular, oval-shaped nebula.
With apertures larger than 20 cm and magnifications around 120x, It is now possible to distinguish the asymmetric core of the galaxysmall, luminous, and almost star-like, as well as part of the diffuse envelope that surrounds it. The technique of lateral vision (looking slightly out of the corner of your eye) greatly helps to perceive low-contrast details in the outer halo.
In the northwest quadrant of the halo, one can see the main spiral arm of NGC 772That dominant structure gives it its distinctive appearance. With larger telescopes, starting at 40 cm aperture, different fragments and bright knots can be distinguished in the arm, in addition to more clearly detecting the small galaxy NGC 770 to the south, forming the interacting duo.
Aries, Hamal and the zodiac: symbolic meaning
From a cultural and astrological point of view, Aries represents courage, initial impulse, and an adventurous spirit.It is associated with the energy of beginnings, courageous decisions, and leadership, qualities that fit well with its ancient role as a marker of spring, a season of rebirth and the start of cycles.
Within this constellation, Hamal acts as a true beacon of equinoctial energy In astrological tradition, it is linked to willpower, determination, and the ability to forge new paths. Sheratan and Mesarthim complete the ram's head, contributing nuances of initiative, sign, and beginning, as suggested by the etymology of their names.
The relevance of Aries is not limited to its own figure: It is part of the set of twelve constellations of the zodiac.The celestial belt, through which the ecliptic passes and along which the Sun, Moon, and planets appear to move throughout the year, includes, in addition to Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces, each with its principal stars and particular symbolic significance.
Eg Taurus highlights Aldebaran like the reddish eye of the bull; in Gemini, Castor and Pollux shine like a pair of twins; in Scorpio highlights Antares, the “rival of Mars”; in Leo prevails, Regulus, the heart of the lion; and in Virgo stands out, Ear of Wheat as a symbol of abundance and harvest. Each of these stars functions as an interpretive axis within its constellation.
Similarly, Aries and Hamal are interpreted as catalysts for initiative and courageinviting us to take the lead, take risks, and launch new projects. Although today the equinox is technically located in Pisces, the symbolic legacy of Aries as the "gateway" to the annual cycle remains deeply rooted in many traditions.
Aries in Greek mythology and the Golden Fleece
In Greek mythology, the The constellation of Aries is associated with the myth of the Golden FleeceThe figure of the celestial ram represents the winged animal sent by the gods to rescue two siblings: Phrixus and Helle, children of King Athamas and the goddess Nephele.
According to legend, Athamas abandoned Nephele and took Ino as his new wifeNephele, who detested her stepchildren, conspired to get rid of them. Faced with this situation, Nephele begged the gods for help, and Hermes responded by sending an extraordinary flying ram with a golden fleece to save the children.
The ram succeeded He rescued Phrixus and Helle and took them on a flight eastwardHowever, during the flight over the strait separating Europe from Asia, Helle fell into the sea and drowned. From then on, that strait became known as the Hellespont, "the sea of Helle," a name that has endured in historical tradition.
Phrixus, on the other hand, managed to arrive safely in the kingdom of Colchiswhere he was welcomed by King Aeetes. In gratitude for the divine help received, Phrixus sacrificed the ram in honor of Zeus and gave the golden fleece to the monarch, who hung it in a sacred grove dedicated to the god Ares.
To protect such a valuable treasure, The fleece was guarded by a ferocious dragon, which devoured anyone who came near. Years later, the hero Jason, with the help of Medea, managed to steal the Golden Fleece, giving rise to one of the most famous epic adventures in Greek mythology, narrated in the story of the Argonauts and their legendary ship.
In recognition of the feat and the symbolism of the saving ramThe gods placed the animal in the sky, transforming it into the constellation of Aries. In this way, the winged ram with the golden fleece was immortalized in the celestial vault, with Hamal as one of its main stars, perpetuating the link between myth, sky, and seasonal cycles.
Hamal and the constellation of Aries condense astronomy, history, myth, and symbolism: a nearby orange giant star with a giant planet around it, once aligned with the spring equinox, turned into a reference for celestial coordinates, surrounded by galaxies like NGC 772 and loaded with cultural meanings ranging from ancient agriculture to the zodiac and the story of the Golden Fleece.
