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A galaxy cluster could be likened to an excellent metropolis of galaxies, a galactic conurbation the place every galaxy represents a person, twinkling construction. Simply as an archaeologist would possibly search proof of the oldest cities on Earth, astronomers have lengthy sought to find the oldest galaxy clusters within the universe – every the cosmic equal of an historical civilization like Jericho or Ur.
I’ve been lucky to steer a staff of astronomers in discovering simply such an instance of an outdated galaxy cluster. How outdated? The sunshine from the galaxy cluster, named XLSSC 122 has taken 10.four billion years to journey throughout the universe to us.
A youthful universe
Astronomers consider that the universe itself is 13.7 billion years outdated, so slightly maths tells us that we’re observing XLSSC 122 when the universe was a mere three.three billion years outdated. Think about our shock then, when every new view of this galaxy cluster revealed a bodily construction seemingly each bit as mature and developed as galaxy clusters in our present-day universe – a scenario reasonably like taking a look at a photograph out of your youth during which you seem a lot older than you had been.
XLSSC 122 is a remarkably precocious presence in a youthful universe, a clue maybe that the universe – not less than the densest components of it – can kind stars, accumulate into galaxies and ultimately be drawn into galaxy clusters with stunning rapidity. On condition that pc simulations of the meeting of galaxy clusters point out extra gradual progress, the invention of XLSSC 122 means that our present concepts of how construction types within the universe could also be incomplete.
Discovering galaxy clusters
After I first noticed it, XLSSC 122 appeared as an unassuming assortment of photons on an X-ray picture of the sky taken by the European House Company’s X-ray Multi-Mirror house observatory. Although considered at nice distance, we knew we had been probably observing a scorching halo of gasoline – at 10 million Kelvin – confined throughout the gravitational discipline of a large cluster of galaxies.
Nevertheless, seen mild photos taken with the Canada-France-Hawaii Telescope revealed no galaxies related to the X-ray supply. This was an attention-grabbing clue that we could have found a distant galaxy cluster the place the enlargement of the universe had shifted the seen mild emitted by the cluster galaxies into the infrared.
From this realization, we proceeded to acquire a picture of our candidate cluster utilizing the European Southern Observatory’s Very Giant Telescope. This picture, taken with an infrared digicam, revealed the telltale presence of faint purple objects – distant galaxies; however precisely how distant remained a thriller.
Hubble House Telescope brings final readability
Having compiled a powerful case that XLSSC 122 was a distant galaxy cluster, maybe probably the most distant, we had been awarded observing time with the Hubble House Telescope. On condition that just one out of each 10 Hubble proposals is profitable, this represented an achievement in itself.
Though the Hubble telescope is sort of 30 years outdated, it stays a pre-eminent astronomical facility. Our photos of XLSSC 122 appeared sharp and clear in comparison with the fuzzy photos obtained from ground-based observatories. Though I’ve been an expert astronomer for 20 years, seeing the Hubble photos of our cluster represented a near-unique discovery second. It was instantly clear from the galaxy colors and spectra that XLSSC 122 was supremely distant: it lay at a redshift of two, that means that the sunshine from XLSSC 122 had taken 10.four billion years to achieve Earth.
Simulating galaxies
How does a cluster akin to XLSSC 122 match into our wider image of how the universe is structured? Pc simulations permit astronomers to recreate the uneven distribution of matter within the early universe after which to observe the drive of gravity because it attracts the extra dense areas into large clusters whereas much less dense areas turn out to be ever extra sparse.
One can establish clusters in these simulations which have the identical properties as XLSSC 122. As a simulation is just like a film of the universe, we are able to quick ahead to the current. Once we did this for XLSSC 122 we realized that it might turn out to be some of the large clusters within the universe – corresponding to the nice cluster in Coma, our closest assortment of galaxies. The identical simulations point out that XLSSC 122 would possibly solely have existed as a cluster of galaxies for maybe a billion years earlier than the second we noticed it.
Herein lies the thriller. Our examine of the starlight from the galaxies that make up XLSSC 122 tells us they’re a couple of billion years outdated, maybe as a lot as three billion years outdated. Furthermore, all of them appeared to start out forming stars at virtually the identical time. However as all of this occurred lengthy earlier than these galaxies ever clumped collectively to kind XLSSC 122, we’re left with the query as to what brought about them to start out forming stars in such a synchronized method within the early universe?
Fortuitously, we’ve a fairly good thought of the place to look subsequent. NASA plans to launch the James Webb House Telescope in March 2021, and we’re already planning forward to focus on XLSSC 122. The Webb telescope will gather roughly six instances extra mild than Hubble and can analyze that mild with a lot of delicate devices. Our intention is to make use of high-resolution infrared spectroscopy to drastically enhance our information of the stellar ages of the galaxies that make up XLSSC 122 and pin down the formative years story of this exceptional cluster of galaxies.
Associated Hyperlinks
University of Victoria
Stellar Chemistry, The Universe And All Within It
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A Cosmic Jekyll and Hyde
Boston MA (SPX) Feb 21, 2020
A double star system has been flipping between two alter egos, in keeping with observations with NASA’s Chandra X-ray Observatory and the Nationwide Science Basis’s Karl F. Jansky Very Giant Array (VLA). Utilizing practically a decade and a half price of Chandra knowledge, researchers observed stellar duo behaved like one kind of object earlier than switching its identification, after which returning to its unique state after just a few years. It is a uncommon instance of a star system altering its habits on this approach.
Astro … read more
