On a clear autumn night, away from the brightest streetlights, there is a smudge of light in the Massachusetts sky that does not belong to our galaxy at all. It is the Andromeda Galaxy, and the first person known to have written it down was a Muslim astronomer working in Persia more than a thousand years ago.

His name was 'Abd al-Rahman al-Sufi, known in Latin Europe as Azophi. This fall, as the long nights return and Isha comes earlier, his "little cloud" is one of the best reasons for a family to step outside, look up and reflect.

Who was al-Sufi?

Al-Sufi lived from 903 to 986. Around the year 964 he finished his famous star catalogue, the Book of the Fixed Stars (Kitab Suwar al-Kawakib al-Thabita). According to London's Science Museum, he worked for the Buyid ruler 'Adud al-Dawla, and the Buyid rulers funded an observatory in Shiraz, in what is now Iran, where he carried out his work.

The book was not written from scratch. Al-Sufi took the star catalogue in the Almagest, written by the Alexandrian astronomer Ptolemy in the second century, and revised and enlarged it with his own observations. For the stars he knew in the 48 classical constellations, he recorded positions, brightness and color, and he added illustrations of each constellation. He also brought in the older Arabic star traditions, so the book places Greek figures and Arabian star pictures side by side.

That blending is exactly where the galaxy shows up.

The "little cloud" by the mouth of a fish

In his notes on the constellation Andromeda, al-Sufi described a faint patch he called a "little cloud" (al-latkha al-sahabiya). In the illustrations, it appears as a cluster of dots at the mouth of a large fish, an Arabic constellation that al-Sufi drew overlapping the Greek figure of Andromeda.

The Science Museum calls this the earliest known reference to a galaxy other than the Milky Way. A copy of the book made around 1009 to 1010 is kept at Oxford's Bodleian Library (MS. Marsh 144) and shows the fish with the little cloud at its mouth.

Al-Sufi did not claim to have found it alone. The Messier catalogue site run by SEDS notes that the "cloud" was apparently already known to astronomers in Isfahan, very probably before 905. His book also contains the first recorded mention of the Large Magellanic Cloud, which he said southern Arabs called al-Bakr, the White Ox.

His work was not known in Europe when the telescope was invented. The German astronomer Simon Marius found the Andromeda "nebula" again with a telescope in 1612, about six and a half centuries after al-Sufi wrote it down.

What the little cloud really is

For a long time no one knew what the smudge was. NASA explains that a century ago, many astronomers did not accept that other galaxies existed, so the object was called the "Andromeda Nebula." In 1920, Harlow Shapley and Heber Curtis argued about its nature in what became known as the "Great Debate." A few years later, Edwin Hubble, building on Henrietta Leavitt's work with Cepheid variable stars, found Cepheids in photographs of Andromeda and concluded that it lies far outside our Milky Way.

Today NASA describes Andromeda, also called M31, as our galaxy's largest neighbor, about 2.5 million light-years away and holding around a trillion stars. Its light is so old that, in NASA's words, it left the galaxy's stars when our earliest ancestors were figuring out stone tools.

Looking up as an act of reflection

The Qur'an repeatedly invites believers to think about the sky. In Surah Al 'Imran, Allah says: "Indeed, in the creation of the heavens and the earth and the alternation of the day and night there are signs for people of reason" (3:190). The next verse describes those people as the ones "who remember Allah while standing, sitting, and lying on their sides, and reflect on the creation of the heavens and the earth," and who say, "Our Lord! You have not created all of this without purpose. Glory be to You!" (3:191, translation from Quran.com).

These verses do not teach astronomy, and they do not need to. They ask for something else: attention, wonder and gratitude. Al-Sufi's careful measurements and the verses' call to reflect sit comfortably together. One is the work of a scientist describing what he saw; the other is a reminder of why looking is worth doing. Standing in a dark field and knowing that faint glow is a whole other galaxy is a good way to feel both at once.

How to find Andromeda from Massachusetts

Set your expectations. Our header is a long-exposure photograph taken through a telescope. To the naked eye, NASA says, Andromeda looks like a faint, fuzzy patch, about magnitude 3.4. Binoculars show more: the bright core and a hint of its saucer-shaped disk.

Use the star guides. Andromeda's constellation becomes prominent as autumn arrives in the Northern Hemisphere. NASA suggests using the Great Square of Pegasus or the W-shaped constellation Cassiopeia to find it; the galaxy sits near the border between Andromeda and Cassiopeia. A sky-chart app can help you match the shapes, but let your eyes adjust to the dark for a while before searching.

Mind the Moon. Moonlight washes out faint objects. According to Timeanddate.com, the Moon over Boston is waxing toward full on Oct. 26 at 12:11 a.m., the Hunter's Moon, so evenings this week and next will be bright. After the third-quarter Moon on Nov. 1, the Moon rises later in the night, and the new Moon arrives Nov. 9 at 2:02 a.m. The first half of November should give the darkest evening skies.

Get away from city light. NASA notes that light pollution, haze and thin clouds hurt the view, though a patient observer can still pick out the galaxy's core from moderately lit suburbs on a clear night. A backyard in a smaller town, a field or a beach will usually beat a city street.

Where to look through a telescope

  • Boston University's Judson B. Coit Observatory, 725 Commonwealth Ave., Boston, holds Public Open Nights most Wednesday evenings, weather permitting. From October to March the program starts promptly at 7:30 p.m., and there is no late admission. Tickets are free but required, limited to five per person, and released on Eventbrite on Thursday mornings around 11 a.m. for the following Wednesday. Call 617-353-2630 no earlier than two hours before start time to check whether the night is on. The observatory is reached only by stairs, and unaccompanied minors are not admitted.
  • The Center for Astrophysics | Harvard & Smithsonian at 60 Garden St., Cambridge, hosts public Observatory Nights with a non-technical talk and rooftop telescope viewing when the weather allows. Admission is free, tickets are limited, and parking is free on event nights. The Harvard College Observatory says they are usually held on the last Thursday of selected months, so check its events page or join its mailing list for the next date.
  • The Amateur Telescope Makers of Boston keep a clubhouse at 20 Millstone Hill Road in Westford. It is open most clear, moonless Friday and Saturday nights, but non-members may visit only with a member or by prior arrangement through the club. Call 978-692-8708 before heading out, and follow the club's red-light rules after sunset.

A small family plan

Pick a clear evening in early November, after Isha. Bring a blanket, binoculars if you have them, and warm layers. Find Cassiopeia's W or the Great Square, sweep slowly with your binoculars, and wait for the faint oval glow. Then tell your children the story: a scholar in Shiraz, a fish drawn in ink, and a little cloud he wrote down more than a thousand years before anyone knew it was a galaxy.

As al-Sufi's later readers discovered, sometimes the most important thing is simply to look carefully, and to write down what you see.