“In 1976, Janet and I signed up for an ‘astronomy cruise’ to Bermuda. We have been on deck one night time the place Fred Hess, a planetarium professional, identified the star patterns seen to the bare eye. Janet used her binoculars to have a look at the objects described, and the excessive level got here once we noticed the Andromeda Galaxy for the primary time. If the cruise had ended at that time, we’d have had our cash’s price.”
— Isaac Asimov, from “In Pleasure Nonetheless Felt” (Doubleday & Firm, 1980)
There was a great motive why the famed science author Isaac Asimov and his spouse Janet have been jubilant on that night time at sea. For they’d simply had their very first have a look at essentially the most distant object that may be glimpsed with the unaided eye: the Andromeda Galaxy.
And this week, with the intense moon having left our night sky, you too could have an opportunity to see this most wonderful of deep sky objects, which can be passing virtually straight overhead between 7:30 and eight p.m. native time.
Associated: Evening sky, November 2023: What you’ll be able to see tonight [maps]
The place to look
BEST BINOCULARS
Take a look at our information on one of the best binoculars of 2023 that will help you discover the suitable optics for viewing the Andromeda Galaxy or the rest within the night time sky.
To seek out the Andromeda Galaxy, first find the Nice Sq. of Pegasus — a landmark of the autumn sky. Then, focus binoculars on the intense star Alpheratz, which is on the higher left nook of the Sq.. Then transfer straight throughout to the east (left) and get the star Mirach (in Andromeda) in your area of view. From there, transfer slowly as much as a reasonably vivid star above Mirach and proceed to run up in the identical route till you may discover the “little cloud” described by Al-Sufi, greater than a millennium in the past.
That can be your stopping place, for you’ll have discovered the Andromeda Galaxy.
For those who aren’t aware of these stars or the Pegasus constellation, you can all the time use a stargazing app that will help you discover the Andromeda Galaxy — however put the cellphone away as quickly as you have situated it to let your eyes regulate to the darkish night time sky to make sure they’ll absorb as a lot mild from this distant metropolis of stars as attainable.
Recall that the Asimov’s had the benefit of being situated on shipboard in the course of the Atlantic after they made their Andromeda Galaxy sighting; not a lot concern about mild air pollution on the market! However so as so that you can see it requires good eyesight and a darkish, crystal-clear night time with no avenue or home lighting close by.
With the unaided eye it seems as nothing greater than an indefinite, mysterious glow; a diffuse elongated cloud maybe two or 3 times the obvious width of the moon.
The “Little Cloud”
The Andromeda Galaxy was supposedly first famous by the Persian astronomer Abd-al-Rahman Al-Sufi, who described it as a “little cloud” in his “Ebook of Mounted Stars” in 964 A.D. However it could even have been identified to Persian astronomers in what’s now Iran way back to 905 A.D., and even earlier. An professional on star nomenclature, Richard Hinckley Allen, as soon as reported that it additionally appeared on a Dutch star map from the 12 months 1500.
Galileo’s rival, Simon Marius is often credited with the primary telescopic remark of this object in December of 1612. He described the nebula as an indefinite glow “like a candle shining via the horn window of a lanthorn (lantern).”
An amazing metropolis of stars
Even right this moment, binoculars and telescopes reveal this “cloud” as little greater than a clean oval blur, which step by step brightens within the middle to a star-like nucleus. Whereas it’ll definitely look bigger and brighter than along with your eyes alone, there may be little to recommend the grandeur of this object as it’s typically proven in lengthy publicity observatory images. It is oval as a result of from our vantage level we’re viewing it not removed from edgewise, however in actual fact, it is a practically round, flat spiral assemblage of star clouds.
The sunshine from that “little cloud” is definitely the full accumulation of sunshine from roughly one trillion (1,000,000,000,000) stars. It’s listed as Messier (“M”) 31, in Charles Messier’s well-known catalog: hazy objects resembling comets, however later proved to be galaxies, nebulae and star clusters.
Right here is essentially the most distant object that may be seen with the unaided eye. M31 has been estimated to be practically 200,000 mild years in diameter or one and a half instances as large as our personal Milky Method galaxy. Its vivid nucleus is the hazy patch that’s seen to the unaided eye.
Like our personal galaxy, M31 has a number of attendant satellite tv for pc galaxies. Two of those: M32 and M110 might be picked out with low magnification in a small-to-medium sized telescope, in the identical area of view as M31. There are but two different smaller companions (NGC 147 and 185) that are a lot fainter and positioned a lot farther away, near the border of close by Cassiopeia.
Starlight that traveled a great distance
As you have a look at the Andromeda Galaxy tonight, you may be doing one thing that nobody else on this planet besides a stargazer can do; you’ll truly be wanting again into the distant previous.
There’s a excellent motive that this patch of sunshine seems so very faint to the bare eye. Once you see it tonight, contemplate that this mild has been touring some 2,500,000 years to succeed in you, touring all that point on the great velocity of 671 million miles (1.08 billion km) per hour. The sunshine you’re seeing is round 25,000 centuries outdated and commenced its journey across the time of the daybreak of human consciousness. The sunshine you at the moment are getting is not less than 480 instances older than the Pyramids; the space it has traveled is so inconceivable that even to put in writing the variety of miles appears all however meaningless.
When it started its practically 15-quintillion (15,000,000,000,000,000,000)-mile journey earthward, mastodons and saber-toothed tigers roamed over a lot of pre-ice-age North America and prehistoric man was struggling for existence in what’s now the Olduvai Gorge of East Africa.
And that is truly only a neighbor of ours. With giant observatory telescopes, we’ve got noticed galaxies which can be over a billion mild years away, or greater than 400 instances farther than Andromeda!
Then contemplate these galaxies that the James Webb House Telescope is at present detecting. Mild left a few of them effectively over 13 billion years in the past, inside just some hundred million years of the Huge Bang.
Cosmic collisions of the previous … and future
Current research point out that about six billion years in the past, the Andromeda Galaxy was breached by one other giant spiral galaxy. After a number of billion years, this intruder looped round Andromeda and eventually smashed into its core and triggered it to broaden. Andromeda’s satellite tv for pc galaxy, M32 — a small, compact elliptical galaxy — is regarded as the core of the renegade galaxy that collided with Andromeda. Initially it was itself most likely a spiral galaxy, whose arms have been stripped off by Andromeda’s gravity.
Apparently, Andromeda is approaching our personal Milky Method galaxy at a fee of 186.411 miles per second (300 km/s) and a galactic collision between the 2 is now anticipated to happen in about 4.5 billion years. Based mostly on present calculations there’s a 50% likelihood that in such a merged galaxy, our photo voltaic system can be swept out 3 times farther from the galactic core than its present distance. There’s additionally a 12% likelihood that the photo voltaic system can be ejected from the newly merged galaxy someday throughout the collision.
That is all a moot level as far as life on Earth is anxious. In about 0.5 to 1.5 billion years the solar’s luminosity could have risen by 35% to 40%, seemingly initiating a runaway greenhouse impact on our planet. As a consequence, the floor of the Earth could have already change into far too scorching for liquid water to exist, ending all terrestrial life by the point the 2 galaxies collide.
Joe Rao serves as an teacher and visitor lecturer at New York’s Hayden Planetarium. He writes about astronomy for Pure Historical past journal, the Farmers’ Almanac and different publications.
