The space between galaxies has long been considered a dead area. Single rogue stars may pop stars may pop up here or there‚ but the majority of this cosmic backward was considered empty by astronomers. But now‚ a paper from astronomers at various European and California institutions has found a trail of stars flowing between galaxies in a cluster. They’re calling it the Giant Coma Stream‚ after the Coma Cluster of galaxies where it originates. Observing this cluster back in 1933‚ Fritz Zwicky‚ a Swiss astronomer‚ noticed that the galaxies in the cluster were moving too fast to be caused by only ordinary matter. The “dunkele Materie” (dark matter) that he proposed back then is still our best guess as to what is causing these galaxies to move so fast‚ even if we still don’t entirely understand what that means. There were plenty of galaxies for Zwicky and the modern-day astronomers to look at. The Coma Cluster contains over a thousand cataloged galaxies and is about 300 million light-years away in the Coma Berenices constellation. It remains a favor of amateur astronomers because some of its brighter galaxies can seen with relatively small amateur telescopes. EarthSky has a video describing the new discovery.Credit – EarthSky YouTube Channel It was a relatively small amateur telescope‚ though one run by professional astronomer Michael Rich of UCLA‚ who also happens to be Neil de Grass Tyson’s PhD advisor. He initially used a 70-cm telescope in Califonia to detect a faint wisp of a trail of stars between galaxies in the cluster. As with so much in astronomy‚ a bigger telescope was needed‚ so Dr. Rich reached out to his colleagues across the Atlantic and got some time on the 4.2-m William Herschel Telescope in Spain. This much larger telescope could see the full extent of the stream‚ and its scale was breathtaking.  From our perspective‚ the stream runs in a straight line in the middle of a complex gravitational environment of galaxies constantly disrupting each other’s trajectories. Even in that disruptive environment‚ the stream appears coherent and is almost ten times the size of our own galaxy. Isaac Arthur explains how useful these streams of stars might turn out to be if we ever decide to colonize other galaxies.Credit – SFIA YouTube Channel This isn’t the first time astronomers have found streams of stars. Some have even been spotted in the Milky Way itself. But this is the first time that astronomers have found a stream large enough that it crosses the chasm between galaxies. It wasn’t even what they were looking for in the first place – Dr. Javier Roman of the University of Groningen and the University of La Laguna‚ who served as lead author on the paper‚ mentioned in a press release that his team was actually looking for halos around stars located in large galaxies‚ of which there are plenty in the Coma Cluster.  But now‚ this new research path has got him excited. Computer simulations the team developed after this first observation show that there could be many faint extragalactic bridges out there. With time‚ larger telescopes such as the Extremely Large Telescope‚ with a whopping 39-meter observational dish‚ and Euclid‚ which recently started releasing color images. With these more capable observational tools‚ Dr. Roman is confident they will find more extragalactic streams of stars. Due to the high demand‚ it might be a while before they can get some observational time on these newest observatories. Given the success of this paper‚ though‚ there might be plenty more star streams that can be found with smaller telescopes as well. Learn More:Astonomie.nl – Astronomers spot giant stream of stars between galaxiesJavier Roman et al. – A giant thin stellar stream in the Coma Galaxy ClusterUT – A Star Near the Center of the Milky Way is a Visitor from BeyondUT – A River of Stars Streaming Across the Sky Lead Image:Image of the Coma Cluster with the Giant Coma Stream shown as the black line from upper left to bottom right.Credit – Roman et al. The post A Giant Stream of Stars is Flowing in Deep Space appeared first on Universe Today.

Anyone who regularly watches the skies may well be familiar with the constellation Orion the hunter. It is one of the few constellations that actually looks like the thing it is supposed to look like rather than some abstract resemblance. One prominent star is Betelgeuse and back in 2020 it dimmed to a level lower than ever before in recorded history. A team of astronomers have been studying the event with some fascinating results. Betelgeuse is a red supergiant star almost 650 light years from Earth. With a radius of 617 million kilometres‚ if it were in the position of the Sun‚ then the orbit of Earth would be buried deep within its layers. It’s also a variable star which means it varies its output of light and in the case of Betelgeuse this variability is semi-regular or in other words‚ regular with a few irregularities along the way! Its variability is related to a pulsating of the stars radius which occurs over a period of around 400 days although there is a longer period of variability of around 2‚100 days of uncertain origin‚ possibly linked to variation in convective flow.  Back in 2020 Betelgeuse dimmed to a level that had never been recorded in what has since been dubbed the “Great Dimming”. It’s visual brightness or magnitude‚ dropped by 1.6 although its dimming did not seem consistent across the star’s sphere; the southern hemisphere was much darker than the northern and there have been many theories put forward to explain the event. Among them‚ large formations of star spots or dust clouds above the photosphere are favourite. A paper published recently in Astronomy and Astrophysics by a team of astronomers led by Daniel Jadlovský explores the Great Dimming event using 15 years of data from the STELLA robotic telescope. The STELLA system comprises two robotic telescopes in Spain coupled with a high resolution spectrograph and a wide field imager.  STELLA Observatory in Tenerife‚ Spain. The data allowed the team to explore the photosphere (visible layer) of Betelgeuse in incredible detail. They were able to gain valuable insight into the radial pulsations‚ shockwaves and how they passed through the photospheric layers. Five distinct layers of the photosphere were identified using the tomogrpahic technique – a method where images are constructed form a series of projections.  Analysis revealed that the variations in the innermost photospheric layer‚ known as C1 was in line with the timescales of the visual magnitude variations. Shockwaves travelling through the layers also seemed to be broadly in line with the brightness variations.  In regards to the Great Dimming vent of 2020‚ the data showed two powerful shock waves in the photosphere‚ the first likely to be the cause of a major outflowing of material which caused an infall of all layers. As the infall reached maximum velocity the second‚ more powerful shockwave occurred leading to the a significant outflow of material. Due to the different photospheric layers‚ these events didn’t happen simultaneously across them all and it wasn’t until early 2022 that Betelgeuse settled back down.  Source : The Great Dimming of Betelgeuse: the photosphere as revealed by tomography during the past 15 years The post 15 Years of Data Reveal the Events Leading Up to Betelgeuse’s “Great Dimming” appeared first on Universe Today.

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