HomeNewsNanotechnology'Double' galaxy mystifies Hubble astronomers

‘Double’ galaxy mystifies Hubble astronomers


Oct 07, 2021 (Nanowerk News) Astronomers have seen some fairly bizarre issues scattered throughout our huge universe, from exploding stars to colliding galaxies. So, you’d suppose that once they see a wierd celestial object, they’d have the ability to determine it. But NASA’s Hubble Space Telescope uncovered what seems to be a pair of similar objects that look so bizarre it took astronomers a number of years to find out what they’re. “We were really stumped,” stated astronomer Timothy Hamilton of Shawnee State University in Portsmouth, Ohio. The oddball objects encompass a pair of galaxy bulges (the central star-filled hub of a galaxy) and a minimum of three practically parallel cut up streaks. Hamilton noticed them by chance whereas utilizing Hubble to survey a set of quasars, the blazing cores of energetic galaxies. After chasing dead-end theories, soliciting assist from colleagues, and doing plenty of head-scratching, Hamilton and the rising staff, led by Richard Griffiths of the University of Hawaii in Hilo, lastly put collectively all the clues to resolve the thriller (The Monthly Notices of the Royal Astronomical Society, “Hamilton’s Object – a clumpy galaxy straddling the gravitational caustic of a galaxy cluster: constraints on dark matter clumping”). The linear objects had been the stretched pictures of a gravitationally lensed distant galaxy, situated greater than 11 billion light-years away. And, they seemed to be mirror pictures of one another. This Hubble Space Telescope snapshot exhibits three magnified pictures of a distant galaxy embedded in a cluster of galaxies. These pictures are produced by a trick of nature known as gravitational lensing. The galaxy cluster’s immense gravity magnifies and distorts the sunshine from the distant galaxy behind it, creating the a number of pictures. The galaxy cluster, catalogued as SDSS J223010.47-081017.8, is 7 billion light-years from Earth. Hubble has noticed many gravitationally lensed galaxies. However, the photographs noticed on this Hubble snapshot are distinctive. Two of the magnified pictures, proven within the pull-out at backside proper, are actual copies of one another. The two shiny ovals are the cores of the galaxy. This uncommon phenomenon happens as a result of the background galaxy straddles a ripple within the material of space. This “ripple” is an space of best magnification, brought on by the gravity of dense quantities of dark matter, the unseen glue that makes up a lot of the universe’s mass. As mild from the faraway galaxy passes by means of the cluster alongside this ripple, two mirror pictures are produced, together with a 3rd picture that may be seen off to the facet. A detailed-up of the third picture is proven within the pull-out at high proper. This picture most intently resembles the distant galaxy, which is situated greater than 11 billion light-years away. Based on a reconstruction of this picture, the researchers decided that the distant galaxy seems to an edge-on, barred spiral with ongoing, clumpy star formation. The mirror pictures are named “Hamilton’s Object” for the astronomer who found them. (Image: NASA, ESA, Richard Griffiths (University of Hawaii), and Jenny Wagner (Heidelberg University) (click on on picture to enlarge) The staff found that the immense gravity of an intervening, and uncatalogued, foreground cluster of galaxies was warping space, magnifying, brightening, and stretching the picture of a distant galaxy behind it, a phenomenon known as gravitational lensing. Though Hubble surveys reveal loads of these funhouse-mirror distortions brought on by gravitational lensing, this object was uniquely perplexing. In this case, a exact alignment between a background galaxy and a foreground galaxy cluster produces twin magnified copies of the identical picture of the distant galaxy. This uncommon phenomenon happens as a result of the background galaxy straddles a ripple within the material of space. This “ripple” is an space of best magnification, brought on by the gravity of dense quantities of dark matter, the unseen glue that makes up a lot of the universe’s mass. As mild from the faraway galaxy passes by means of the cluster alongside this ripple, two mirror pictures are produced, together with a 3rd picture that may be seen off to the facet. Griffiths compares this impact to the brilliant wavy patterns seen on the underside of a swimming pool. “Think of the rippled surface of a swimming pool on a sunny day, showing patterns of bright light on the bottom of the pool,” he defined. “These bright patterns on the bottom are caused by a similar kind of effect as gravitational lensing. The ripples on the surface act as partial lenses and focus sunlight into bright squiggly patterns on the bottom.” In the gravitationally lensed distant galaxy, the ripple is drastically magnifying and distorting the sunshine from the background galaxy that’s passing by means of the cluster. The ripple acts like an imperfect curvy mirror that generates the twin copies.

Solving the Mystery

But this uncommon phenomenon wasn’t well-known when Hamilton noticed the unusual linear options in 2013. As he appeared by means of the quasar pictures, the snapshot of the mirrored pictures and parallel streaks stood out. Hamilton had by no means seen something prefer it earlier than, and neither had different staff members. “My first thought was that maybe they were interacting galaxies with tidally stretched-out arms,” Hamilton stated. “It didn’t really fit well, but I didn’t know what else to think.” So Hamilton and the staff started their quest to resolve the thriller of those tantalizing straight traces, later dubbed Hamilton’s Object for its discoverer. They confirmed the unusual picture to colleagues at astronomy conferences, which elicited a wide range of responses, from cosmic strings to planetary nebulae. But then Griffiths, who was not a member of the unique staff, supplied probably the most believable rationalization when Hamilton confirmed him the picture at a NASA assembly in 2015. It was a magnified and distorted picture brought on by a lensing phenomenon just like these seen in Hubble pictures of different huge galaxy clusters which can be amplifying pictures of very distant galaxies. Griffiths confirmed this concept when he realized of the same linear object in one among Hubble’s deep-cluster surveys. The researchers, nonetheless, nonetheless had an issue. They could not determine the lensing cluster. Normally, astronomers who examine galaxy clusters first see the foreground cluster that is inflicting the lensing, after which discover the magnified pictures of distant galaxies inside the cluster. A search of the Sloan Digital Sky Survey pictures revealed {that a} galaxy cluster resided in the identical space because the magnified pictures, however it didn’t present up in any catalogued survey. Nevertheless, the truth that the unusual pictures had been on the heart of a cluster made it clear to Griffiths that the cluster was producing the lensed pictures. The researchers’ subsequent step was in figuring out whether or not the three lensed pictures had been on the similar distance, and due to this fact had been all of the distorted portraits of the identical faraway galaxy. Spectroscopic measurements with the Gemini and W. M. Keck observatories in Hawaii helped the researchers make that affirmation, exhibiting that the lensed pictures had been from a galaxy situated greater than 11 billion light-years away. The distant galaxy, primarily based on a reconstruction of the third lensed picture, seems to be an edge-on, barred spiral with ongoing, clumpy star formation. Around the identical time because the spectroscopic observations by Griffiths and undergraduates in Hilo, a separate group of researchers in Chicago recognized the cluster and measured its distance utilizing Sloan knowledge. The cluster resides greater than 7 billion light-years away. But, with little or no details about the cluster, Griffiths’ staff was nonetheless fighting tips on how to interpret these uncommon lensing shapes. “This gravitational lens is very different from most of the lenses that were studied before by Hubble, particularly in the Hubble Frontier Fields survey of clusters,” Griffiths defined. “You don’t have to stare at those clusters for long to find many lenses. In this object, this is the only lens we have. And we didn’t even know about the cluster at first.”

Mapping the Invisible

That’s when Griffiths known as an skilled on gravitational lensing principle, Jenny Wagner of the University of Heidelberg in Germany. Wagner had studied related objects and, with colleague Nicolas Tessore, now on the University of Manchester in England, developed pc software program for decoding distinctive lenses like this one. Their software program helped the staff determine how all three lensed pictures got here to be. They concluded that the dark matter across the stretched pictures needed to be “smoothly” distributed in space at small scales. “It’s great that we only need two mirror images in order to get the scale of how clumpy or not dark matter can be at these positions,” Wagner stated. “Here, we don’t use any lens models. We just take the observables of the multiple images and the fact they can be transformed into one another. They can be folded into one another by our method. This already gives us an idea of how smooth the dark matter needs to be at these two positions.” This result’s necessary, Griffiths stated, as a result of astronomers nonetheless do not know what dark matter is, practically a century after its discovery. “We know it’s some form of matter, but we have no idea what the constituent particle is. So we don’t know how it behaves at all. We just know that it has mass and is subject to gravity. The significance of the limits of size on the clumping or smoothness is that it gives us some clues as to what the particle might be. The smaller the dark matter clumps, the more massive the particles must be.”





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