Aries
Aries is a small zodiac constellation that rises into autumn evening skies. It has only a handful of noticeable stars, but because the spring equinox point sat here about 2,000 years ago, it has long been counted as the first sign of the zodiac.
| Latin name | Aries |
|---|---|
| Abbreviation | Ari |
| Brightest star | Hamal (mag 2.0) |
| Best seen | Autumn–early winter evenings (Northern Hemisphere) |
| Astrological dates | March 21 – April 19 |
| Sun actually passes | April 19 – May 13 |
| Stars used by Planetica | 938 |
How to find it
From the Northern Hemisphere, Aries is well placed in the evening sky from autumn into early winter. From mid-northern latitudes it climbs high in the south around 9–10 p.m. in November and December. The whole constellation is small and fairly faint, so it is much easier to spot from somewhere away from city lights.
Good signposts are the Great Square of Pegasus, the classic autumn landmark, and the Pleiades star cluster in Taurus. Look roughly halfway between them, just south of Andromeda, and you'll see three stars of 2nd–3rd magnitude forming a short, slightly bent line. That's the Ram's head. The brightest, orange-tinted star is Hamal, next to it is Sheratan, and the fainter one is Mesarthim. Right to the north lies the long, thin triangle of Triangulum, which helps you confirm you're in the right spot.
Honestly, it's hard to see a ram in Aries. Only the few stars of the head stand out to the naked eye; the body and legs are faint 4th–5th magnitude stars. If you have binoculars or a small telescope, aim at Mesarthim: it splits cleanly into two white stars of almost equal brightness, a lovely double star.
The myth: the ram with the Golden Fleece
In Greek mythology, Aries is a flying ram with a golden fleece. King Athamas of Boeotia had two children, Phrixus and Helle, but his new queen, Ino, hated them and plotted to have them sacrificed to the gods. Their real mother, the cloud goddess Nephele, found out and sent the golden ram to rescue them.
The ram carried both children on its back and flew east over the sea. On the way, Helle slipped and fell into the water, and that stretch of sea became known as the Hellespont, "Helle's sea" (today's Dardanelles). Phrixus arrived safely in Colchis, at the far eastern end of the Black Sea, sacrificed the ram to Zeus, and gave the golden fleece to the local king. The fleece was guarded by a dragon that never slept, and it was this very fleece that the hero Jason and the Argonauts later set out to find. The ram itself is said to have risen into the sky as a constellation.
In East Asian astronomy, the sky was divided into 28 "lunar mansions" along the Moon's path around the sky. The stars of Aries fall within two of them, the Bond (婁宿) and the Stomach (胃宿).
Main stars
| Name | Apparent magnitude | Distance (approx., ly) | Notes |
|---|---|---|---|
| Hamal (Alpha) | 2.0 | ~66 | The brightest star in Aries, an orange giant. Research has reported a planet orbiting it. |
| Sheratan (Beta) | 2.6 | ~60 | A white star with a very close companion orbiting it, making it a binary. |
| Mesarthim (Gamma) | 3.9 (combined) | ~160 | One of the first double stars discovered in the early telescope era; even a small telescope splits it. |
| 41 Arietis | 3.6 | ~170 | Once the brightest star of Musca Borealis, an old constellation no longer in use. |
Aries has almost no bright clusters or nebulae worth viewing with the naked eye or binoculars. The spiral galaxy NGC 772 is its best-known telescopic target, but it's fairly faint and not easy for beginners.
Birthday sign dates: two different answers
There are two ways to give the dates for Aries. In astrology (Western sun signs), Aries runs from March 21 to April 19. But during that time, the real Sun is actually in Pisces, not Aries. The Sun passes through the boundaries of the Aries constellation from about April 19 to May 13.
The first reason is precession. Earth's axis slowly wobbles in a circle like a spinning top, taking about 26,000 years per turn. As a result, the Sun's position at the spring equinox (the vernal equinox point) drifts west by about 1 degree every 72 years. The 12 astrological signs were fixed based on the sky of about 2,000 years ago, when the equinox point was in Aries, and they still divide the ecliptic into equal 30-degree slices starting from the equinox point. Meanwhile, the equinox point has moved by almost a full constellation and now sits in Pisces.
The second reason is constellation boundaries. The boundaries made official by the International Astronomical Union (IAU) in 1930 vary in size, so the Sun spends anywhere from 6 to 44 days in a single constellation. Aries is on the short side, at about 25 days. The dates can shift by a day or so from year to year.
In Planetica
Planetica builds a one-of-a-kind planetary system from your name and birthday, then places it near a real star in the Milky Way. If your birthday's astrological sign is Aries, your system settles next to a real star inside the Aries constellation.
Candidate stars come from the HYG catalog, a public database of real star positions and brightnesses. There are 938 stars within about 3,000 light-years of Earth that fall inside the IAU boundaries of Aries. One of them is picked at random, and your system is placed about 1–6 light-years from it, so you can think of that star as your close neighbor.
People with exactly the same name and birthday get "twin systems": they all sit in Aries, but each next to a different star. Planetica also shows which constellation the Sun was really in on your birthday. For example, someone born on April 10 is an Aries in astrology, but on that day the Sun was actually in Pisces.
Fun facts
- Astronomers still call the vernal equinox point the "First Point of Aries," even though it's actually in Pisces now. The old name simply stuck.
- The equinox point keeps moving and will cross into Aquarius around the year 2600.
- The name Hamal comes from the Arabic word for "sheep" or "lamb."
Other constellations
Create your own planetary system
Enter a name and a birthday to get a one-of-a-kind planetary system, placed next to a real star in your birthday constellation.