NSHow far can you see? Well, as I write this, the upper reaches of the Cotswolds are visible in the hazy distance, about 40 km away. Of course, in terms of astronomy, our horizons are much broader. Saturn, as seen tonight, is 1,420 million km away, while the star Deneb is at 25,000 trillion km, or 2,600 light years: the light we see from Deneb was left behind when the Babylonians The famous Hanging Gardens were being built.
But look to the zenith on a dark moonlit night, and you’ll see a faint faint patch that puts all these objects to shame. The Andromeda galaxy is 2.5 million light years away. We are looking at Andromeda as the first humans began to evolve.
It’s a shame it’s so far away, because the Andromeda galaxy close-up will be a stunning sight—a spectacular spiral shape comprised of hundreds of billions of stars, along with glowing gas clouds and dark cobwebs of interstellar gas. It is a close twin of our own Milky Way, the galaxy that is home to the Sun and all the stars we see at night.
And there’s a smaller brother on view tonight, the Triangulum Galaxy – although “small” is a relative term, as it still hosts more than 10 billion stars. Look for this dimly lit blur with binoculars near the pointed end of the constellation Triangle (triangle) in Andromeda’s lower left. If you’re lucky enough to be out in the desert on a completely black night, you might be able to see this galaxy with your unaided eye – pushing your record for distance-sight by about 3 million light-years.
These three-star cities are not alone. Dozens of other galaxies swarm between and around them, forming the Local Group of galaxies. Most of these cosmic neighbors are very small, some containing only a million stars.
You might wonder why astronomers spend time studying these dwarf galaxies even though there are much more spectacular specimens far and wide, including starburst galaxies and quasars. That’s because our neighborhood is so general: it’s likely typical of conditions in most of the universe. The Local Group is a microcosm of the universe.
The smallest galaxies at our doorstep are the most common type of star cluster in the universe, yet they are so faint that we can’t see them outside the Local Group. And they are the building blocks of galaxies: In the distant past, millions of these galaxies combined to form galaxies like our Milky Way.
And this trend continues even today. From the Southern Hemisphere, you can easily see two more members of our group, the Large and the Small Magellanic Clouds. They look like stars and clouds torn from the Milky Way. In fact, the opposite is true: our galaxy’s gravity is tearing the two Magellanic Clouds apart, and eventually the Milky Way will swallow them up.
The most interesting of our neighbors are the invisible galaxies that are believed to revolve around us. Normal matter in our universe is much more than unseen “dark matter”, and our best theories of galaxy birth say that much of it ended up in tiny clumps. Some of these also include stars, and we see these clusters as dwarf galaxies near the Milky Way.
But in many cases, astronomers think, there was not enough gas inside these dark condensates to form stars. So many of our close neighbors may be invisible, made only of dark matter – and researchers are hot on their way. The Local Group is the only place where these strange dark galaxies are close enough for us to study, giving us unique insights into the mysteries of the universe.
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You might think that Venus, shining after sunset, is spectacular enough—but this month it tightens the glare control even more, as the planet heads toward Earth. The evening star joins with the crescent moon on 9 October, creating an unforgettable sight.
The giant planet Jupiter, second only to Venus in brightness, lies to the south. To its right, you’ll find dim Saturn – although the Ringworld still overtakes most stars. The Moon orbits under the two giant planets on the night of October 13-15.
Up in the southern sky, you can’t miss a large square of stars. For the ancient Greeks, it was the body of the flying horse Pegasus. Oddly enough, they saw him upside down in the sky: the stars to the right of the square depict his neck and head, with his nose (Star Enif) pointing up.
Pegasus was the child of the sea-god Poseidon and the demonic Medusa (so ugly that humans turned to stone upon seeing him). And her birth was very unusual: a winged horse sprang from her mother’s neck when the superhero Perseus beheaded her.
You’ll find Perseus next to Princess Andromeda in the east. He won her hand by killing the sea-demon Cetus (at Pegasus’s lower left) and using Medusa’s severed head to turn Andromeda’s other suitors into stone.
Meanwhile, in the morning sky, at the end of October you have a chance to see the innermost planet. This month, the elusive Mercury is decelerating in the east before sunrise, in its best morning appearance of the year.
October 9: Crescent very near Venus
October 10: Crescent moon near Antares
October 13, 4:25 a.m.: First Trimester Moon near Saturn
October 14: Moon between Jupiter and Saturn
October 15: Moon near Jupiter
October 16: Venus near Antara
October 20, 3.56 pm: Poornima
October 21: Maximum Orionid meteor shower
October 22: Moon near the Pleiades
23 October: Moon near Aldebarani
October 25: Mercury at greatest elongation in the west
October 27: Moon near Castor and Pollux
October 28, 9.05 p.m.: Last Quarter Moon
October 29: Venus at greatest eastward
October 31, 2:00 pm: British summer time ends
Philip’s 2022 Stargazing by Nigel Henbest (Phillip’s £6.99) is your guide to everything happening in the sky next year
Credit: www.independent.co.uk /