by “In 1976, Janet and I signed up for an ‘astronomical cruise’ to Bermuda. One night we were on deck where Fred Hess, a planetarium expert, pointed out star patterns visible to the naked eye. Janet used her binoculars to observe” The objects described, and the climax came when we saw the Andromeda galaxy for the first time. “If the cruise had ended at that point, we would have gotten our money’s worth.”
— Isaac Asimov, from “In Joy Still Felt” (Doubleday & Company, 1980)
There was a good reason why famous science writer Isaac Asimov and his wife Janet were jubilant that night at sea. Because they had just observed for the first time the most distant object that can be glimpsed with the naked eye: the Andromeda galaxy.
And this week, when the bright moon has left our night sky, you will also have the opportunity to see this amazing deep sky object, which will pass almost directly overhead between 7:30 and 8 pm local time.
Related: Night sky, November 2023: what you can see tonight [maps]
Where to look
BEST BINOCULARS
Check out our guide to the best binoculars of 2023 to help you find the right optics for viewing the Andromeda Galaxy or anything else in the night sky.
To find the Andromeda Galaxy, first locate the Great Plaza of Pegasus, a landmark of the autumn sky. Next, focus your binoculars on the bright star Alpheratz, which is located in the upper left corner of the square. Then move east (left) and place the star Mirach (in Andromeda) in your field of vision. From there, move slowly to a fairly bright star above Mirach and continue running in the same direction until you find the “small cloud” described by Al-Sufi, over a millennium ago.
That will be your stopping place, because you will have found the Andromeda galaxy.
If you’re not familiar with these stars or the Pegasus constellation, you can always use a stargazing app to help you find the Andromeda galaxy, but Keep your phone as soon as you have located it to let your eyes adjust to the dark night sky and ensure that they can capture as much light as possible from this distant city of stars.
Let us remember that the Asimovs had the advantage of being located aboard a ship in the middle of the Atlantic when they made their sighting of the Andromeda galaxy; There is not much concern about light pollution! But to see it you need good eyesight and a dark, crystal clear night, with no lighting on the streets or nearby houses.
At first glance it appears to be nothing more than an indefinite and mysterious glow; an elongated, diffuse cloud perhaps two or three times the apparent width of the moon.
The “little cloud”
The Andromeda galaxy was supposedly first discovered by the Persian astronomer Abd-al-Rahman Al-Sufi, who described it as a “small cloud” in his “Book of Fixed Stars” in 964 AD But it is It may also have been known to Persian astronomers. in what is now Iran dates back to 905 AD, or even earlier. An expert in star nomenclature, Richard Hinckley Allen, once reported that it also appeared on a Dutch star map from the 1500s.
Galileo’s rival, Simon Marius, is often credited with the first telescopic observation of this object in December 1612. He described the nebula as an indefinite glow “like a candle shining through the window of a lantern.”
A tremendous city of stars
Even today, binoculars and telescopes reveal this “cloud” as little more than a soft oval blob, which gradually brightens in the center until it becomes a star-like core. While it will certainly appear larger and brighter than the naked eye, there is little to suggest the grandeur of this object as often shown in long-exposure photographs from observatories. It is oval because from our point of view we are seeing it not far from the edge, but in fact, it is a set of spiraling stellar clouds, flat and almost circular.
The light from that “little cloud” is actually the total accumulation of light from approximately one trillion (1,000,000,000,000) stars. It is cataloged as Messier (“M”) 31, in Charles Messier’s famous catalogue: hazy objects that look like comets, but were later shown to be galaxies, nebulae and star clusters.
Here is the most distant object that can be seen with the naked eye. M31 has been estimated to be nearly 200,000 light-years across, or one and a half times the width of our Milky Way galaxy. Its bright core is the nebulous spot that is visible to the naked eye.
Like our own galaxy, M31 has several companion satellite galaxies. Two of them: M32 and M110 can be distinguished at low magnification in a small to medium-sized telescope, in the same field of view as M31. There are two other smaller companions (NGC 147 and 185) that are much weaker and located much further away, near the edge of nearby Cassiopeia.
Starlight that traveled a long way
When you look at the Andromeda Galaxy tonight, you will be doing something that no one else in the world except a stargazer can do; you will actually be looking into the distant past.
There is a very good reason why this patch of light appears so dim to the naked eye. When you see it tonight, consider that this light has been traveling some 2,500,000 years to reach you, all that time traveling at the tremendous speed of 671 million miles (1.08 billion kilometers) per hour. The light you are seeing is around 25,000 centuries old and began its journey at the time of the dawn of human consciousness. The light they are receiving now is at least 480 times older than the Pyramids; the distance he has traveled is so inconceivable that even writing down the number of miles seems almost insignificant.
As he began his nearly 15 trillion (15,000,000,000,000,000,000) mile journey toward Earth, mastodons and saber-toothed tigers roamed much of pre-Ice Age North America and prehistoric man struggled to survive. existence in what is now the Olduvai Gorge in East Africa. .
And this is actually just a neighbor of ours. With large observatory telescopes, we have observed galaxies that are more than a billion light years away, or more than 400 times farther than Andromeda!
Then consider those galaxies that the James Webb Space Telescope is currently detecting. Light left some of them more than 13 billion years ago, just a few hundred million years after the Big Bang.
Cosmic collisions from the past… and the future
RELATED STORIES:
— Andromeda Galaxy: facts about our closest galactic neighbor
—The Andromeda galaxy crash triggered a massive galactic migration 2 billion years ago.
— Galactic archeology reveals that Andromeda, neighbor of the Milky Way, has a violent past
Recent studies indicate that about six billion years ago, the Andromeda galaxy was crossed by another large spiral galaxy. After several billion years, this intruder circled Andromeda, eventually colliding with its core and causing it to expand. Andromeda’s satellite galaxy, M32, a small, compact elliptical galaxy, is believed to be the core of the renegade galaxy that collided with Andromeda. Initially it was probably a spiral galaxy, whose arms were torn off by Andromeda’s gravity.
Interestingly, Andromeda is approaching our own galaxy, the Milky Way, at a speed of 186,411 miles per second (300 km/s) and a galactic collision between the two is now anticipated to occur within about 4.5 billion years. According to current calculations, there is a 50% chance that in such a merging galaxy, our solar system will be swept three times farther from the galactic core than its current distance. There is also a 12% chance that the solar system will be ejected from the newly merged galaxy at some point during the collision.
All of this is debatable when it comes to life on Earth. In approximately 500 to 1.5 billion years, the Sun’s luminosity will have increased by 35% to 40%, likely initiating a runaway greenhouse effect on our planet. As a consequence, the Earth’s surface will have already become too hot for liquid water to exist, putting an end to all terrestrial life when the two galaxies collide.
Joe Rao serves as an instructor and guest lecturer at New York University. Hayden Planetarium. Write about astronomy during natural history magazinehe Farmers’ Almanac and other publications.
