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This artist’s concept shows a closeup of the Large Magellanic Cloud, a dwarf galaxy that is one of the Milky Way galaxy’s nearest neighbors. Credits:
NASA, ESA, Ralf Crawford (STScI) A story of survival is unfolding at the outer reaches of our galaxy, and NASA’s Hubble Space Telescope is witnessing the saga.
The Large Magellanic Cloud, also called the LMC, is one of the Milky Way galaxy’s nearest neighbors. This dwarf galaxy looms large on the southern nighttime sky at 20 times the apparent diameter of the full Moon.
Many researchers theorize that the LMC is not in orbit around our galaxy, but is just passing by. These scientists think that the LMC has just completed its closest approach to the much more massive Milky Way. This passage has blown away most of the spherical halo of gas that surrounds the LMC.
Now, for the first time, astronomers been able to measure the size of the LMC’s halo – something they could do only with Hubble. In a new study to be published in The Astrophysical Journal Letters, researchers were surprised to find that it is so extremely small, about 50,000 light-years across. That’s around 10 times smaller than halos of other galaxies that are the LMC’s mass. Its compactness tells the story of its encounter with the Milky Way.
“The LMC is a survivor,” said Andrew Fox of AURA/STScI for the European Space Agency in Baltimore, who was principal investigator on the observations. “Even though it’s lost a lot of its gas, it’s got enough left to keep forming new stars. So new star-forming regions can still be created. A smaller galaxy wouldn’t have lasted – there would be no gas left, just a collection of aging red stars.”
This artist’s concept shows the Large Magellanic Cloud, or LMC, in the foreground as it passes through the gaseous halo of the much more massive Milky Way galaxy. The encounter has blown away most of the spherical halo of gas that surrounds the LMC, as illustrated by the trailing gas stream reminiscent of a comet’s tail. Still, a compact halo remains, and scientists do not expect this residual halo to be lost. The team surveyed the halo by using the background light of 28 quasars, an exceptionally bright type of active galactic nucleus that shines across the universe like a lighthouse beacon. Their light allows scientists to “see” the intervening halo gas indirectly through the absorption of the background light. The lines represent the Hubble Space Telescope’s view from its orbit around Earth to the distant quasars through the LMC’s gas. NASA, ESA, Ralf Crawford (STScI)
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Though quite a bit worse for wear, the LMC still retains a compact, stubby halo of gas – something that it wouldn’t have been able to hold onto gravitationally had it been less massive. The LMC is 10 percent the mass of the Milky Way, making it heftier than most dwarf galaxies.
“Because of the Milky Way’s own giant halo, the LMC’s gas is getting truncated, or quenched,” explained STScI’s Sapna Mishra, the lead author on the paper chronicling this discovery. “But even with this catastrophic interaction with the Milky Way, the LMC is able to retain 10 percent of its halo because of its high mass.”
A Gigantic Hair Dryer
Most of the LMC’s halo was blown away due to a phenomenon called ram-pressure stripping. The dense environment of the Milky Way pushes back against the incoming LMC and creates a wake of gas trailing the dwarf galaxy – like the tail of a comet.
“I like to think of the Milky Way as this giant hairdryer, and it’s blowing gas off the LMC as it comes into us,” said Fox. “The Milky Way is pushing back so forcefully that the ram pressure has stripped off most of the original mass of the LMC’s halo. There’s only a little bit left, and it’s this small, compact leftover that we’re seeing now.”
As the ram pressure pushes away much of the LMC’s halo, the gas slows down and eventually will rain into the Milky Way. But because the LMC has just gotten past its closest approach to the Milky Way and is moving outward into deep space again, scientists do not expect the whole halo will be lost.
Only with Hubble
To conduct this study, the research team analyzed ultraviolet observations from the Mikulski Archive for Space Telescopes at STScI. Most ultraviolet light is blocked by the Earth’s atmosphere, so it cannot be observed with ground-based telescopes. Hubble is the only current space telescope tuned to detect these wavelengths of light, so this study was only possible with Hubble.
The team surveyed the halo by using the background light of 28 bright quasars. The brightest type of active galactic nucleus, quasars are believed to be powered by supermassive black holes. Shining like lighthouse beacons, they allow scientists to “see” the intervening halo gas indirectly through the absorption of the background light. Quasars reside throughout the universe at extreme distances from our galaxy.
This artist’s concept illustrates the Large Magellanic Cloud’s (LMC’s) encounter with the Milky Way galaxy’s gaseous halo. In the top panel, at the middle of the right side, the LMC begins crashing through our galaxy’s much more massive halo. The bright purple bow shock represents the leading edge of the LMC’s halo, which is being compressed as the Milky Way’s halo pushes back against the incoming LMC. In the middle panel, part of the halo is being stripped and blown back into a streaming tail of gas that eventually will rain into the Milky Way. The bottom panel shows the progression of this interaction, as the LMC’s comet-like tail becomes more defined. A compact LMC halo remains. Because the LMC is just past its closest approach to the Milky Way and is moving outward into deep space again, scientists do not expect the residual halo will be lost. NASA, ESA, Ralf Crawford (STScI)
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The scientists used data from Hubble’s Cosmic Origins Spectrograph (COS) to detect the presence of the halo’s gas by the way it absorbs certain colors of light from background quasars. A spectrograph breaks light into its component wavelengths to reveal clues to the object’s state, temperature, speed, quantity, distance, and composition. With COS, they measured the velocity of the gas around the LMC, which allowed them to determine the size of the halo.
Because of its mass and proximity to the Milky Way, the LMC is a unique astrophysics laboratory. Seeing the LMC’s interplay with our galaxy helps scientists understand what happened in the early universe, when galaxies were closer together. It also shows just how messy and complicated the process of galaxy interaction is.
Looking to the Future
The team will next study the front side of the LMC’s halo, an area that has not yet been explored.
“In this new program, we are going to probe five sightlines in the region where the LMC’s halo and the Milky Way’s halo are colliding,” said co-author Scott Lucchini of the Center for Astrophysics | Harvard & Smithsonian. “This is the location where the halos are compressed, like two balloons pushing against each other.”
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contacts:
Claire Andreoli (claire.andreoli@nasa.gov)
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Ann Jenkins, Ray Villard
Space Telescope Science Institute, Baltimore, MD
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Last Updated Nov 14, 2024 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Astrophysics Astrophysics Division Galaxies Hubble Space Telescope Irregular Galaxies Spiral Galaxies The Milky Way Keep Exploring Discover More Topics From NASA
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Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s X-59 quiet supersonic research aircraft sits in its run stall at Lockheed Martin’s Skunk Works facility in Palmdale, California, firing up its engine for the first time. These engine-run tests start at low power and allow the X-59 team to verify the aircraft’s systems are working together while powered by its own engine. The X-59 is the centerpiece of NASA’s Quesst mission, which seeks to solve one of the major barriers to supersonic flight over land by making sonic booms quieter.NASA/Carla Thomas NASA’s Quesst mission marked a major milestone with the start of tests on the engine that will power the quiet supersonic X-59 experimental aircraft.
These engine-run tests, which began Oct. 30, allow the X-59 team to verify the aircraft’s systems are working together while powered by its own engine. In previous tests, the X-59 used external sources for power. The engine-run tests set the stage for the next phase of the experimental aircraft’s progress toward flight.
The X-59 team is conducting the engine-run tests in phases. In this first phase, the engine rotated at a relatively low speed without ignition to check for leaks and ensure all systems are communicating properly. The team then fueled the aircraft and began testing the engine at low power, with the goal of verifying that it and other aircraft systems operate without anomalies or leaks while on engine power.
Lockheed Martin test pilot Dan Canin sits in the cockpit of NASA’s X-59 quiet supersonic research aircraft in a run stall at Lockheed Martin’s Skunk Works facility in Palmdale, California prior to its first engine run. These engine-run tests featured the X-59 powered by its own engine, whereas in previous tests, the aircraft depended on external sources for power. The X-59 is the centerpiece of NASA’s Quesst mission, which seeks to solve one of the major barriers to supersonic flight over land by making sonic booms quieter.NASA/Carla Thomas “The first phase of the engine tests was really a warmup to make sure that everything looked good prior to running the engine,” said Jay Brandon, NASA’s X-59 chief engineer. “Then we moved to the actual first engine start. That took the engine out of the preservation mode that it had been in since installation on the aircraft. It was the first check to see that it was operating properly and that all the systems it impacted – hydraulics, electrical system, environmental control systems, etc. – seemed to be working.”
The X-59 will generate a quieter thump rather than a loud boom while flying faster than the speed of sound. The aircraft is the centerpiece of NASA’s Quesst mission, which will gather data on how people perceive these thumps, providing regulators with information that could help lift current bans on commercial supersonic flight over land.
The engine, a modified F414-GE-100, packs 22,000 pounds of thrust, which will enable the X-59 to achieve the desired cruising speed of Mach 1.4 (925 miles per hour) at an altitude of approximately 55,000 feet. It sits in a nontraditional spot – atop the aircraft — to aid in making the X-59 quieter.
Engine runs are part of a series of integrated ground tests needed to ensure safe flight and successful achievement of mission goals. Because of the challenges involved with reaching this critical phase of testing, the X-59’s first flight is now expected in early 2025. The team will continue progressing through critical ground tests and address any technical issues discovered with this one-of-a-kind, experimental aircraft. The X-59 team will have a more specific first flight date as these tests are successfully completed.
The testing is taking place at Lockheed Martin’s Skunk Works facility in Palmdale, California. During later phases, the team will test the aircraft at high power with rapid throttle changes, followed by simulating the conditions of an actual flight.
NASA’s X-59 quiet supersonic research aircraft sits in its run stall at Lockheed Martin’s Skunk Works facility in Palmdale, California, prior to its first engine run. Engine runs are part of a series of integrated ground tests needed to ensure safe flight and successful achievement of mission goals. The X-59 is the centerpiece of NASA’s Quesst mission, which seeks to solve one of the major barriers to supersonic flight over land by making sonic booms quieter.NASA/Carla Thomas “The success of these runs will be the start of the culmination of the last eight years of my career,” said Paul Dees, NASA’s deputy propulsion lead for the X-59. “This isn’t the end of the excitement but a small steppingstone to the beginning. It’s like the first note of a symphony, where years of teamwork behind the scenes are now being put to the test to prove our efforts have been effective, and the notes will continue to play a harmonious song to flight.”
After the engine runs, the X-59 team will move to aluminum bird testing, where data will be fed to the aircraft under both normal and failure conditions. The team will then proceed with a series of taxi tests, where the aircraft will be put in motion on the ground. These tests will be followed by final preparations for first flight.
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Last Updated Nov 06, 2024 EditorLillian GipsonContactMatt Kamletmatthew.r.kamlet@nasa.gov Related Terms
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By USH
While observing the Orion Nebula with his 12-inch Dobsonian telescope, a sky-watcher noticed an unusual flashing object. As stars appeared to drift due to Earth's rotation, this particular object while flashing approximately every 20 seconds clearly travels through deep space.
The observer wonders whether it might be a rotating satellite or not. However, this isn’t the first sighting of cigar-shaped UFOs or other mysterious objects traveling through space near the Orion Nebula, so it is quite possible that it could be an interstellar craft.
Over the years, I have shared several articles, complete with images and videos, documenting similar UFO sightings around the Orion Nebula. You can explore these under the tag: Orion Nebula.
Interestingly, these sightings have all occurred between November and February, suggesting there may be a seasonal pattern to these observations.
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By NASA
Curiosity Navigation Curiosity Home Mission Overview Where is Curiosity? Mission Updates Science Overview Instruments Highlights Exploration Goals News and Features Multimedia Curiosity Raw Images Images Videos Audio Mosaics More Resources Mars Missions Mars Sample Return Mars Perseverance Rover Mars Curiosity Rover MAVEN Mars Reconnaissance Orbiter Mars Odyssey More Mars Missions The Solar System The Sun Mercury Venus Earth The Moon Mars Jupiter Saturn Uranus Neptune Pluto & Dwarf Planets Asteroids, Comets & Meteors The Kuiper Belt The Oort Cloud 3 min read
Sols 4352-4354: Halloween Fright Night on Mars
NASA’s Mars rover Curiosity acquired this image of the target surface feature nicknamed “Reds Meadow,” using its Mars Hand Lens Imager (MAHLI), located on the turret at the end of the rover’s robotic arm. Curiosity captured the image Oct. 31, 2024, at 19:09:10 UTC, on sol 4350 — Martian day 4,350 of the Mars Science Laboratory Mission. NASA/JPL-Caltech/MSSS Earth planning date: Friday, Nov. 1, 2024
Yesterday evening (Thursday) was Halloween for many of us here on Earth. My neighborhood in eastern Canada was full of small (and not so small!) children, running around in the dark collecting sweets and candy but also getting scared by the ghostly decorations hung at each house. Little did we suspect that our poor rover on Mars was also getting spooked. Curiosity completed about a meter (about 3 feet) of the planned drive before becoming unsettled … scared, if you will! … when its left front wheel got hung up on a rock and stopped moving.
Luckily, we understood this kind of frightened behavior and were able to resume planning today as per usual. That meter was enough to give us a whole new set of targets to choose from. As APXS Strategic Planner this week, I had chosen darker-looking targets in the workspace — “Ladder Lake” and “Reds Meadow” (shown in the accompanying MAHLI image) — earlier in the week. I was happy that bumping backwards by a meter allowed us to reach some of the more typical pale colored bedrock at “Eureka Valley” and a second APXS analysis on “Black Bear Lake,” which is a mixture of both pale bedrock and some darker layers. MAHLI added in a bonus set of images on “Stag Dome,” focusing on small, rougher patches on the pale bedrock.
ChemCam is taking advantage of the short bump, too, adding a passive observation on the brushed Reds Meadow target, analyzed by APXS and MAHLI in Monday’s plan. A ChemCam LIBS target “Hoist Ridge” focuses on a small vertical face of dark material. Two long distance images planned for ChemCam’s Remote Micro Imager (RMI) look at the distribution of rocks along the Gediz Vallis ridge in the distance.
Mastcam is taking several mosaics this weekend (must have gotten extra energy from the Halloween sugar!). Close to the rover, Mastcam will acquire single-frame images of the targets Hoist Ridge and Eureka Valley, and a small mosaic of some surficial troughs just a little further away. Moving further afield, a small 3×1 mosaic (three images in one row) will image the same area as the ChemCam RMI of the Gediz Vallis ridge, and a larger 9×2 mosaic will focus on the faraway yardang unit, where we hopefully will be in a few years.
Then for the really big images: Mastcam will image the whole landscape in a special 360-degree view, so big it needs to be broken into two parts. The first will have 43×4 frames, the second 34×5 frames. These mosaics are huge, so we save them for when we are at a really good vantage point to allow us to capture as much detail as possible for science and engineering planning.
As ever, we continue our environmental monitoring of conditions, with Mastcam and Navcam movies and images looking at dust in the atmosphere above and around us in Gale crater, and watching out for dust devils.
Written by Catherine O’Connell-Cooper, Planetary Geologist at University of New Brunswick
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Last Updated Nov 04, 2024 Related Terms
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By NASA
3 Min Read November’s Night Sky Notes: Snowballs from Space
This diagram compares the size of the icy, solid nucleus of comet C/2014 UN271 (Bernardinelli-Bernstein) to several other comets. The majority of comet nuclei observed are smaller than Halley’s comet. They are typically a mile across or less. Comet C/2014 UN271 is currently the record-holder for big comets. And, it may be just the tip of the iceberg. There could be many more monsters out there for astronomers to identify as sky surveys improve in sensitivity. Though astronomers know this comet must be big to be detected so far out to a distance of over 2 billion miles from Earth, only the Hubble Space Telescope has the sharpness and sensitivity to make a definitive estimate of nucleus size. Credits:
Illustration: NASA, ESA, Zena Levy (STScI) by Kat Troche of the Astronomical Society of the Pacific
If you spotted comet C/2023 A3 (Tsuchinshan-ATLAS) in person, or seen photos online this October, you might have been inspired to learn more about these visitors from the outer Solar System. Get ready for the next comet and find out how comets are connected to some of our favorite annual astronomy events.
Comet Composition
A comet is defined as an icy body that is small in size and can develop a ‘tail’ of gas as it approaches the Sun from the outer Solar System. The key traits of a comet are its nucleus, coma, and tail.
The nucleus of the comet is comprised of ice, gas, dust, and rock. This central structure can be up to 80 miles wide in some instances, as recorded by the Hubble Space Telescope in 2022 – large for a comet but too small to see with a telescope. As the comet reaches the inner Solar System, the ice from the nucleus starts to vaporize, converting into gas. The gas cloud that forms around the comet as it approaches the Sun is called the coma. This helps give the comet its glow. But beware: much like Icarus, sometimes these bodies don’t survive their journey around the Sun and can fall apart the closer it gets.
The most prominent feature is the tail of the comet. Under moderately dark skies, the brightest comets show a dust tail, pointed away from the Sun. When photographing comets, you can sometimes resolve the second tail, made of ionized gases that have been electronically charged by solar radiation. These ion tails can appear bluish, in comparison to the white color of the dust tail. The ion tail is also always pointed away from the Sun. In 2007, NASA’s STEREO mission captured images of C/2006 P1 McNaught and its dust tail, stretching over 100 million miles. Studies of those images revealed that solar wind influenced both the ion and dust tail, creating striations – bands – giving both tails a feather appearance in the night sky.
Comet McNaught over the Pacific Ocean. Image taken from Paranal Observatory in January 2007. Credits: ESO/Sebastian Deiries Coming and Going
Comets appear from beyond Uranus, in the Kuiper Belt, and may even come from as far as the Oort Cloud. These visitors can be short-period comets like Halley’s Comet, returning every 76 years. This may seem long to us, but long-period comets like Comet Hale-Bopp, observed from 1996-1997 won’t return to the inner Solar System until the year 4385. Other types include non-periodic comets like NEOWISE, which only pass through our Solar System once.
But our experiences of these comets are not limited to the occasional fluffy snowball. As comets orbit the Sun, they can leave a trail of rocky debris in its orbital path. When Earth finds itself passing through one of these debris fields, we experience meteor showers! The most well-known of these is the Perseid meteor shower, caused by Comet 109P/Swift-Tuttle. While this meteor shower happens every August in the northern hemisphere, we won’t see Comet Swift-Tuttle again until the year 2126.
The Perseids Meteor Shower. NASA/Preston Dyches See how many comets (and asteroids!) have been discovered on NASA’s Comets page, learn how you can cook up a comet, and check out our mid-month article where we’ll provide tips on how to take astrophotos with your smartphone!
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