The Universe’s giant galaxies pose a thorny problem for astronomers. The galaxies have grown large somehow, and the only things that can make a galaxy giant are probably other galaxies. So mergers must have played an important role.
Astronomers have known about galaxy mergers for a long time, but the process is still mysterious. A new study based on ten years of work presents observations and direct measurements of the galaxy merger process that remove some of the mystery.
A newly discovered supercluster of galaxies is so distant that astronomers say its light has been traveling for over twelve billion years to reach telescopes on Earth. But this cluster, named SPT2349 ?56 is gigantic, and so old that it is actually classified as a proto-cluster of galaxies, meaning it might be one of the earliest large clusters of galaxies in our Universe. It is also one of the most actively star-forming proto-clusters known.
Things may seem quiet and peaceful in the Andromeda Galaxy when you gaze at it in the sky. However, if you know what to look for, there’s evidence of a violent rumble in this galaxy’s past. That’s the takeaway from research by Ivanna Escala, an astronomer at Carnegie Institution for Science in Pasadena. She found telltale clues for a merger a few billion years ago. That’s when Andromeda actively cannibalized another galaxy.
The Universe is full of massive galaxies like ours, but astronomers don’t fully understand how they grew and evolved. They know that the first galaxies formed at least as early as 670 million years after the Big Bang. They know that mergers play a role in the growth of galaxies. Astronomers also know that supermassive black holes are involved in the growth of galaxies, but they don’t know precisely how.
A new Hubble survey of galaxies should help astronomers figure some of this out.
Two peculiar spiral galaxies are in the latest image release from the Hubble Space Telescope. The two galaxies, collectively known as Arp 303, are located about 275 million light-years away from Earth. IC 563 is the odd-shaped galaxy on the bottom right while IC 564 is a flocculent spiral at the top left.
Fittingly, these two oddball galaxies are part of the Atlas of Peculiar Galaxies, which is a catalog of unusual galaxies produced by astronomer Halton Arp in 1966. He put together a total of 338 galaxies for his atlas, which was originally published in 1966 by the California Institute of Technology.
We all know that a humongous black hole exists at the center of our galaxy. It’s called Sagittarius A* (Sgr A* for short) and it has the mass of 4 million suns. We’ve got to see a radio image of it a few weeks back, showing its accretion disk. So, we know it’s there. Astronomers can chart its actions as it gobbles up matter occasionally and they can see how it affects nearby stars. What astronomers are still trying to understand is how Sgr A* formed.
Take a good look at the latest image provided by the Hubble Space Telescope. It shows a huge elliptical galaxy called NGC 474 that lies about 100 million light-years away from us. At about two and a half times larger than our Milky Way Galaxy, it’s really a behemoth. Notice its strange structure—mostly featureless and nearly round, but with layered shells wrapped around the central core. Astronomers want to know what caused these shells. The answer might be in what this galaxy represents: a vision of the future Milky Way and the Andromeda Galaxy.
Sometimes you have to just sit back and marvel at a particularly gorgeous view of a galaxy interaction. When these giant space cities merge with each other, wild and crazy things happen—a sort of “Galaxies Gone Wild” scenario. Take this pair, for example. We see them locked together in a cosmic dance that has lasted for not quite a half-billion years. With each turn on the intergalactic dance floor, they change each other permanently. Eventually, they’ll combine to make one giant galaxy.
Since the Renaissance astronomer Galileo Galilee first studied the heavens using a telescope he built himself, astronomers have been pushing the boundaries of what they can observe. After centuries of progress, they have been able to study and catalog objects in all but the earliest periods of the Universe. But thanks to next-generation instruments and technologies, astronomers will soon be able to observe the “Cosmic Dawn” era – ca. 50 million to billion years after the Big Bang.
In recent years, astronomers have made discoveries that preview what this will be like, the most recent of which is the galaxy candidate known as HD1. This galaxy is about 13.5 billion light-years from Earth (32.2 billion light-years in terms of “proper distance“), making it the farthest ever observed. This discovery implies that galaxies existed as early as 300 million years after the Big Bang, a finding which could have drastic implications for astronomy and cosmology!