You’re looking at NGC 346, a star cluster 210 light years away that is energetically pumping out brand new stars from a dense cloud of gas and dust. Between 10 and 11 billion years ago, nearly all galaxies in the Universe underwent an era of intense star formation similar to what we see in NGC 346. This flurry of stellar birth is poetically nicknamed cosmic noon. Since then, star formation in the Universe has gradually dwindled, though it still blazes away in small pockets. By studying NGC 346 and other clusters like it, we can learn more about the era of cosmic noon and the evolution of galaxies.
To that end, researchers pointed the James Webb Space Telescope’s NIRCam infrared camera at NGC 346 last year, and they announced their preliminary findings at the American Astronomical Society’s annual meeting on January 11, 2023.
A radio-telescope image of the Small Magellanic Cloud reveals more detail than ever seen before. Image Credit: N. Pingel et al.
The Small Magellanic Cloud (SMC) is over 200,000 light-years away, yet it’s still one of our galaxy’s closest neighbours in space. Ancient astronomers knew of it, and modern astronomers have studied it intensely. But the SMC still holds secrets.
By studying it and revealing its structure in more detail, astronomers at The Australian National University hope to grow our understanding of the SMC and galaxies in general.
Part of the SMASH dataset showing an unprecedented wide-angle view of the Large Magellanic Cloud. Image Credit: CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever (Montana State University)
Acknowledgment: Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin
The Magellanic Clouds are two of our closest neighbours, in galactic terms. The pair of irregular dwarf galaxies were drawn into the Milky Way’s orbit in the distant past, and we’ve been looking up at them since the dawn of humanity. Some of our ancestors even gathered pigments and created images of them in petroglyphs and cave paintings.
Following in the footsteps of those ancient artists, astronomers recently used the Dark Energy Camera (DECam) to capture an in-depth portrait of the pair of galaxies.
Image of the night sky taken at the European Southern Observatory’s Very Large Telescope in Chile. The Large and Small Magellanic Clouds are visible in the night sky. Credit: ESO, Y. Beletsky
The Magellanic Clouds are a pair of dwarf galaxies that are bound to the Milky Way. The Milky Way is slowly consuming them in Borg-like fashion, starting with the gas halo that surrounds both Clouds. They’re visible in the southern sky, and for centuries people have gazed up at them. They’re named after the Portuguese explorer Ferdinand Magellan, in our current times.
A view of the gas in the Magellanic System as it would appear in the night sky. The Magellanic Corona covers the entire sky while the Magellanic Stream is seen as gas flowing away from the two dwarf galaxies, the Large and the Small Magellanic Clouds. This image, taken directly from the numerical simulations, has been modified slightly for aesthetics. Image Credit: COLIN LEGG / SCOTT LUCCHINI
Massive galaxies like our Milky Way gain mass by absorbing smaller galaxies. The Large Magellanic Cloud and the Small Magellanic Cloud are irregular dwarf galaxies that are gravitationally bound to the Milky Way. Both the clouds are distorted by the Milky Way’s gravity, and astronomers think that the Milky Way is in the process of digesting both galaxies.
A new study says that process is already happening, and that the Milky Way is enjoying the Magellanic Clouds’ halos of gas as an appetizer, creating a feature called the Magellanic Stream as it eats. It also explains a 50 year old mystery: Why is the Magellanic Stream so massive?
A newfound cluster of young stars (blue star) sits on the periphery of the Milky Way. These stars probably formed from material originating from neighboring dwarf galaxies called the Magellanic Clouds. Credit: NASA/D. Nidever
For some time, astronomers have known that collisions or mergers between galaxies are an integral part of cosmic evolution. In addition to causing galaxies to grow, these mergers also trigger new rounds of star formation as fresh gas and dust are injected into the galaxy. In the future, astronomers estimate that the Milky Way Galaxy will merge with the Andromeda Galaxy, as well as the Small and Large Magellanic Clouds in the meantime.
According to new results obtained by researchers at the Flatiron Institute’s Center for Computational Astrophysics (CCA) in New York city, the results of our eventual merger with the Magellanic Clouds is already being felt. According to results presented at the 235th meeting of the American Astronomical Society this week, stars forming in the outskirts of our galaxy could be the result of these dwarf galaxies merging with our own.
Rotation of the Large Magellanic Cloud, as revealed by the ESA's Gaia spacecraft. Copyright: ESA/Gaia/DPAC
On December 19th, 2013, the European Space Agency’s (ESA) Gaia spacecraft took to space with for a very ambitious mission. Over the course of its planned 5-year mission (which was recently extended), this space observatory would map over a billion stars, planets, comets, asteroids and quasars in order to create the largest and most precise 3D catalog of the Milky Way ever created.
Since that time, the ESA has made two data releases that cover the first three years of the Gaia mission. The second data release, which took on April 25th, 2018, has already proven to be a treasure trove for astronomers. In addition to the positions, distance indicators and motions of over a billion stars and celestial objects in the Milky Way Galaxy, it also contained a hidden gem – the proper motions of stars within the Large Magellanic Cloud (LMC).
Located about 200,000 light-years from Earth, the LMC has dense clouds of dust that results in it experiencing high rates of star formation. In addition, it’s central bar is warped (where the east and west ends are nearer to the Milky Way), suggesting that it was once a barred dwarf spiral galaxy who’s spiral arms were disrupted by interaction with the Small Magellanic Cloud (SMC) and the Milky Way.
The proper motions of the stars in the LMC, as captured by the Gaia spacecraft (without color). Copyright: ESA/Gaia/DPAC
For these reasons, astronomers have been hoping to derive the orbits of dwarf galaxies (and globular clusters) that revolve around the Milky Way. In so doing, they hope to learn more about how our galaxy evolved due to mergers with clusters and other galaxies. By determining the proper motions of the LMC’s stars, the Gaia mission has provided clues as to how the Milky Way and its largest satellite galaxy have interacted over time.
As you can see from the image (at top), the bar of the LMC is outlined in great detail, along with individual star-forming regions like the Tarantula Nebula (aka. 30 Doradus, which is visible just above the center of the galaxy). The image combines the total amount of radiation detected by the observatory in each pixel. The radiation measurements were then taken through different filters on the spacecraft to generate color information.
This allowed Gaia to obtain information about the total density of stars within the LMC as well as their proper motions. As you can see, the image is dominated by the brightest, most massive stars, which greatly outshine their fainter, lower-mass counterparts. The proper motions of the stars observed is represented as the texture of the image – which looks a lot like a fingerprint.
The Large Magellanic Cloud (LMC), one of the nearest galaxies to our Milky Way, as viewed by ESA’s Gaia satellite using information from the mission’s second data release. Copyright ESA/Gaia/DPAC
From this, scientists were able to see an imprint of the stars rotating clockwise around the center of the galaxy. Using this information, astronomers will be able to create new models on how the LMC, SMC, and Milky Way evolved together over time. This, in turn, could shed light on how galaxies like our own, formed and evolved over the course of billions of years.
As with other information contained in the first and second data releases, this latest discovery demonstrates that the Gaia mission is fulfilling its intended purpose. The third release of Gaia data is scheduled to take place in late 2020, with the final catalog being published in the 2020s. Meanwhile, an extension has already been approved for the Gaia mission, which will now remain in operation until the end of 2020 (to be confirmed at the end of this year).
And be sure to enjoy this animated view of the LMC’s rotation, courtesy of the ESA:
Hubble image of NGC 248, two nebulas located in the Small Magellanic Cloud. Credit: NASA, ESA, STScI, K. Sandstrom/SMIDGE team
The Hubble Space Telescope has revealed some amazing things over the past few decades. Over the course of its many missions, this orbiting observatory has spotted things ranging from distant stars and galaxies to an expanding Universe. And today, twenty-six years later, it is still providing us with rare glimpses of the cosmos.
For example, just in time for the holidays, Hubble has released images of two rosy, glowing nebulas in the Small Magellanic Cloud (SMC). These glowing clouds of gas and dust were spotted as part of a study known as the Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE), an effort to study this neighboring galaxy in an attempt to better understand our own.
The images were taken by Hubble’s Advanced Camera for Surveys (ACS) in September 2015 and feature NGC 248 – two gaseous nebulas that were first observed by astronomer Sir John Herschel in 1834 and are situated in such a way as to appear as one. Measuring about 60 light years in length and 20 light-years in width, these nebulas are among a series of emission nebulas located in the neighboring dwarf satellite galaxy.
Small and Large Magellanic Clouds over Paranal Observatory Credit: ESO/J. Colosimo
Emission nebulas are essentially large clouds of ionized gases that emit light of various colors – in this case, bright red. The color and luminosity of NGC 248 is due to the nebulas heavy hydrogen content, and the fact that they have young, brilliant stars at the center of them. These stars emit intense radiation that heats up the hydrogen gas, causing it to emit bright red light.
As noted, the images were taken as part of the SMIDGE study, an effort on behalf of astronomers to probe the Milky Way satellite – which is located approximately 200,000 light-years away in the southern constellation Tucana – using the Hubble Space Telescope. The ultimate goal of this study is to understand how dust is different in galaxies that have a far lower supply of the heavy elements needed to create it.
In the case of the SMC, it has between one-fifth and one-tenth the amount of heavy metals as the Milky Way. In addition, its proximity to the Milky Way makes it a convenient target for astronomers who are looking to better understand the history of the earlier Universe. Essentially, most star formation in the Milky Way happened at a time when the amount of heavy elements was much lower than it is now.
Ground-based image of the Small Magellanic Cloud. showing the area of the SMIDGE survey and the position of NGC 248. Credit: NASA/ESA/Hubble/Digitized Sky Survey 2
According to Dr. Karin Sandstrom, a professor from the University of California and the principle investigator of SMIDGE, studying the SMC’s can tell us much about neighboring galaxies, but also about the evolution of the Milky Way. “It is important for understanding the history of our own galaxy, too,” he said. “Dust is a really critical part of how a galaxy works, how it forms stars.”
In addition to the stunning images, the SMIDGE team and the Space Telescope Science Institute have also produced a video that shows the location of NGC 248 in the southern sky. As you can see, the video begins with a ground-based view of the night sky (from the southern hemisphere) and then zooms in on the Small Magellanic Cloud, emphasizing the field where NGC 249 appears.
Check out the video below, and have yourselves a Merry Christmas and some Happy Holidays!
The night sky above the Danish 1.54-metre telescope at ESO's La Silla Observatory. The Magellanic Clouds are visible to the right of the central bar of the Milky Way. Credit: ESO/Z. Bardon
Since ancient times, human beings have been staring at the night sky and been amazed by the celestial objects looking back at them. Whereas these objects were once thought to be divine in nature, and later mistaken for comets or other astrological phenomena, ongoing observation and improvements in instrumentation have led to these objects being identified for what they are.
For example, there are the Small and Large Magellanic Clouds, two large clouds of stars and gas that can be seen with the naked eye in the southern hemisphere. Located at a distance of 200,000 and 160,000 light years from the Milky Way Galaxy (respectively), the true nature of these objects has only been understand for about a century. And yet, these objects still have some mysteries that have yet to be solved.
Characteristics:
The Large Magellanic Cloud (LMC) and the neighboring the Small Magellanic Cloud (SMC) are starry regions that orbit our galaxy, and look conspicuously like detached pieces of the Milky Way. Though they are separated by 21 degrees in the night sky – about 42 times the width of the full moon – their true distance is about 75,000 light-years from each other.
Ultraviolet view of the Large Magellanic Cloud from Swift’s Ultraviolet/Optical Telescope. Credit: NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)
The Large Magellanic Cloud is located about 160,000 light-years from the Milky Way, in the constellation Dorado. This makes it the 3rd closest galaxy to us, behind the Sagittarius Dwarf and Canis Major Dwarf galaxies. Meanwhile, the Small Magellanic Cloud is located in the constellation of Tucana, about 200,000 light-years away.
The LMC is roughly twice the diameter of the SMC, measuring some 14,000 light-years across vs. 7,000 light years (compared to 100,000 light years for the Milky Way). This makes it the 4th largest galaxy in our Local Group of galaxies, after the Milky Way, Andromeda and the Triangulum Galaxy. The LMC is about 10 billion times as massive as our Sun (about a tenth the mass of the Milky Way), while the SMC is equivalent to about 7 billion Solar Masses.
In terms of structure, astronomers have classified the LMC as an irregular type galaxy, but it does have a very prominent bar in its center. Ergo, it’s possible that it was a barred spiral before its gravitational interactions with the Milky Way. The SMC also contains a central bar structure and it is speculated that it too was once a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular.
Aside from their different structure and lower mass, they differ from our galaxy in two major ways. First, they are gas-rich – meaning that a higher fraction of their mass is hydrogen and helium – and they have poor metallicity, (meaning their stars are less metal-rich than the Milky Way’s). Both possess nebulae and young stellar populations, but are made up of stars that range from very young to the very old.
The Small Magellanic Cloud as seen by Swift’s Ultraviolet/Optical Telescope. This composite of 656 separate pictures has a cumulative exposure time of 1.8 days. Credit: NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)
In fact, this abundance in gas is what ensures that the Magellanic Clouds are able to create new stars, with some being only a few hundred million years in age. This is especially true of the LMC, which produces new stars in large quantities. A good example of this is it’s glowing-red Tarantula Nebula, a gigantic star-forming region that lies 160,000 light-years from Earth.
Astronomers estimate that the Magellanic Clouds were formed approximately 13 billion years ago, around the same time as the Milky Way Galaxy. It has also been believed for some time that the Magellanic Clouds have been orbiting the Milky Way at close to their current distances. However, observational and theoretical evidence suggests that the clouds have been greatly distorted by tidal interactions with the Milky Way as they travel close to it.
This indicates that they are not likely to have frequently got as close to the Milky Way as they are now. For instance, measurements conducted with the Hubble Space Telescope in 2006 suggested that the Magellanic Clouds may be moving too fast to be long terms companions of the Milky Way. In fact, their eccentric orbits around the Milky Way would seem to indicate that they came close to our galaxy only once since the universe began.
The Small and Large Magellanic Clouds visible over the Paranal Observatory in Chile. Credit: ESO/J. Colosimo
This was followed in 2010 by a study that indicated that the Magellanic Clouds may be passing clouds that were likely expelled from the Andromeda Galaxy in the past. The interactions between the Magellanic Clouds and the Milky Way is evidenced by their structure and the streams of neutral hydrogen that connects them. Their gravity has affected the Milky Way as well, distorting the outer parts of the galactic disk.
History of Observation:
In the southern hemisphere, the Magellanic clouds were a part of the lore and mythology of the native inhabitants, including the Australian Aborigines, the Maori of New Zealand, and the Polynesian people of the South Pacific. For the latter, they served as important navigational markers, while the Maori used them as predictors of the winds.
While the study Magellanic Clouds dates back to the 1st millennium BCE, the earliest surviving record comes from the 10th century Persian astronomer Al Sufi. In his 964 treatise, Book of Fixed Stars, he called the LMC al-Bakr (“the Sheep”) “of the southern Arabs”. He also noted that the Cloud is not visible from northern Arabia or Baghdad, but could be seen at the southernmost tip of Arabian Peninsula.
By the late 15th century, Europeans are believed to have become acquainted with the Magellanic Clouds thanks to exploration and trade missions that took them south of the equator. For instance, Portuguese and Dutch sailors came to know them as the Cape Clouds, since they could only be viewed when sailing around Cape Horn (South America) and the Cape of Good Hope (South Africa).
Panoramic view of the Large and Small Magellanic Clouds above the ESO’s VLT observation site in Chile. Credit: ESO/Y. Beletsky
During the circumnavigation of the Earth by Ferdinand Magellan (1519–22), the Magellanic Clouds were described by Venetian Antonio Pigafetta (Magellan’s chronicler) as dim clusters of stars. In 1603, German celestial cartographer Johann Bayer published his celestial atlas Uranometria, where he named the smaller cloud “Nebecula Minor” (Latin for “Little Cloud”).
Between 1834 and 1838, English astronomer John Herschel conducted surveys of the southern skies from the Royal Observatory at the Cape of Good Hope. While observing the SMC, he described it as a cloudy mass of light with an oval shape and a bright center, and catalogued a concentration of 37 nebulae and clusters within it.
In 1891, the Harvard College Observatory opened an observing station in southern Peru. From 1893-1906, astronomers used the observatory’s 61 cm (24 inch) telescope to survey and photograph the LMC and SMC. One such astronomers was Henriette Swan Leavitt, who used the observatory to discover Cephied Variable stars in the SMC.
Her findings were published in 1908 a study titled “1777 variables in the Magellanic Clouds“, in which she showed the relationship between these star’s variability period and luminosity – which became a very reliable means of determining distance. This allowed the SMCs distance to be determined, and became the standard method of measuring the distance to other galaxies in the coming decades.
Hubble image of variable star RS Puppis, a Cepheid Variable located in the Milky Way Galaxy. Credit: NASA/ESA/Hubble Heritage Team
As noted already, in 2006, measurements made suing the Hubble Space Telescope were announced that suggested the Large and Small Magellanic Clouds may be moving too fast to be orbiting the Milky Way. This has given rise to the theory that they originated in another galaxy, most likely Andromeda, and were kicked out during a galactic merger.
Given their composition, these clouds – especially the LMC – will continue making new stars for some time to come. And eventually, millions of years from now, these clouds may merge with our own Milky Way Galaxy. Or, they could keep orbiting us, passing close enough to suck up hydrogen and keep their star-forming process going.
But in a few billion years, when the Andromeda Galaxy collides with our own, they may find themselves having no choice but to merge with the giant galaxy that results. One might say Andromeda regrets spitting them out, and is coming to collect them!
