Astronomy

The world was much different in 1990 when NASA astronauts removed the Hubble Space Telescope from Space Shuttle Discovery’s cargo bay and placed it into orbit. The Cold War was ending, there were only 5.3 billion humans, and the World Wide Web had just come online.

Now, the old Soviet Union is gone, replaced by a smaller but no less militaristic Russia. The human population has ballooned to 8.1 billion. The internet is a fixture in daily life. We also have a new, more powerful space telescope, the JWST.

But the Hubble keeps delivering, as this latest image shows.

The lenticular galaxy NGC 4753 is about 60 million light-years away. Lenticular galaxies are midway between elliptical and spiral galaxies. They have large-scale disks but only poorly defined spiral arms. NGC 4753 sees very little star formation because like other lenticulars, it’s used up most of its gas. The fact that they contain mostly older stars makes them similar to elliptical galaxies.

Among lenticulars, NGC 4753 is known for the dust lanes surrounding its nucleus. Astronomers think that spirals evolve into lenticulars in dense environments because they interact with other galaxies and with the intergalactic medium. However, NGC 4753 is in a low-density environment. Its environment and complex structure make it a target for astronomers to test their theories of galaxy formation and evolution.

This Hubble image is the sharpest ever taken of NGC 4753, revealing its intriguing complexity and highlighting the space telescope’s impressive resolving power.

Astronomers think that NGC 4753 is the result of a merger with a dwarf galaxy over one billion years ago. The dwarf galaxy was gas-rich, and NGC 4753’s distinct dust rings probably accreted from the merger. NGC 4753’s powerful gravity then shaped the gas into the complex shapes we see in this image. Image Credit: ESA/Hubble & NASA, L. Kelsey

NGC 4763’s unique structure results from a merger with a dwarf galaxy about 1.3 billion years ago. The video below from NOIRlab explains what happened.

NGC 4753 also hosts two known Type 1a supernovae, which are important because they help astronomers study the expansion of the Universe. They serve as standard candles, an important rung in the cosmic distance ladder.

Galaxies like NGC 4753 may not be rare, but the viewing angle plays a key role in identifying them. Our edge-on view of the galaxy makes its lenticular form clear. We could be seeing others like it from different angles that obscure its nature.

This is a model of NGC 4753, as seen from various viewing orientations. From left to right and top to bottom, the angle of the line of sight to the galaxy’s equatorial plane ranges from 10° to 90° in steps of 10°. Although galaxies similar to NGC 4753 may not be rare, only certain viewing orientations allow for easy identification of a highly twisted disk. This infographic is a recreation of Figure 7 from a 1992 research paper.

If we were looking at NGC 4753 from the “top” down, its detailed dust lanes wouldn’t be obvious to us. But fortunately, we are.

And so is the Hubble.

The post The Venerable Hubble Space Telescope Keeps Delivering appeared first on Universe Today.

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BepiColombo is a joint ESA/JAXA mission to Mercury. It was launched in 2018 on a complex trajectory to the Solar System’s innermost planet. The ESA reports that the spacecraft’s thrusters have lost some power.

BepiColombo’s mission is to complete a comprehensive investigation of Mercury’s magnetosphere, magnetic field, and internal and external structure. But travelling around in the inner Solar System is complicated, and the BepiColombo spacecraft will use more energy getting to Mercury than it takes to get to Pluto. The spacecraft will perform nine planetary flybys before reaching its destination at the end of 2025. BepiColombo has already performed one gravity assist at Earth, two at Venus, and five at Mercury. It’ll perform one more at Mercury in January 2025.

The Mercury Transfer Module (MTM) is the part of the spacecraft that delivers a pair of orbiters to Mercury. On April 26th, as the spacecraft was about to execute its next maneuver, the MTM didn’t deliver enough electrical power to its thrusters. A team working on it restored the thrust back to 90% on May 7th. But the MTM still isn’t deliver enough electricity to get back to 100% thrust.

Despite the power problems, the spacecraft is on track to complete its final Mercury flyby. A team is working to maintain the current power level and to understand how the diminished thrust will affect future maneuvers. They’re also working on restoring full power to the thrusters. To facilitate this, the mission’s flight control team at the European Space Operations Centre in Darmstadt, Germany, has arranged additional ground station passes.

BepiColombo employs a solar-electric propulsion system. Two 15-meter-long solar cells gather energy and deliver it to four ion thrusters that use xenon propellant. The thrusters are mounted on gimbals, making them aimable.

This schematic shows the components of BepiColombo’s solar-electric propulsion system minus the solar arrays. There are four T6 gridded ion thrusters mounted on gimbals, three tanks of xenon gas holding 1,400 kg of xenon gas, a high-pressure regulator, four flow control units and two power processing units. The system also includes several metres of high-voltage harness and piping required to connect this complex system together. Image Credit: ESA

BepiColombo consists of three separate spacecraft. The Mercury Transfer Module is kind of like a tugboat delivering two separate orbiters to Mercury. One of the orbiters is the Mercury Planetary Orbiter and it carries 11 scientific instruments, including cameras, several spectrometers, a magnetometer, and others. The other one is the Mercury Magnetospheric Orbiter, largely built by JAXA. It carries five groups of instruments, including one group that will study the plasma and neutral particles from the planet, its magnetosphere, and the solar wind.

This simple schematic shows the three separate spacecraft that combine to make the BepiColombo mission. Image Credit: ESA

The ESA says that they’ll share more information as it becomes available.

The post The BepiColombo Mission To Mercury is Losing Power appeared first on Universe Today.

Walking along on the surface of the Moon, as aptly demonstrated by the Apollo astronauts, is no easy feat.  The gravity at the Moon’s surface is 1/6th of Earth’s and there are plenty of videos of astronauts stumbling, falling and then trying to get up! Engineers have come up with a solution; a robotic arm system that can be attached to an astronauts back pack to give them a helping hand if they fall. The “SuperLimbs” as they have been called will not only aid them as they walk around the surface but also give them extra stability while carrying out tasks. 

The team of MIT engineers identified the problem when considering movement across the lunar surface and were inspired to innovate when they saw videos of astronauts struggling. They acknowledged that while the astronauts were physically very capable, the combination of bulky space suits and 1/6th gravity was recipe for disaster. If an astronaut becomes unbalanced then even though gravity is less, their inertia is the same and they will still fall. 

Sample collection on the surface of the Moon. Apollo 16 astronaut Charles M. Duke Jr. is shown collecting samples with the Lunar Roving Vehicle in the left background. Image: NASA

The solution they designed has been dubbed the Supernumerary Robotic Limbs can be built into their backpack and when needed, be extended. A prototype has been built and it includes a control system to operate the limbs. It was tested on a willing group of volunteers who donned suits to restrict mobility in an attempt to simulate the cumbersome space suits.

As the volunteers attempted to get up from sitting or lying position, the researchers looked at how they moved and how the restrictive suits limited their mobility. The suits were adjusted to more closely simulate a space suit. Using the suit to mimic the stiffness of a traditional suit they got as close as possible to real world testing. The movements of the team in the restricted suits was similar to normal movement but the effort was far less when the SuperLimbs were used. They also found that the volunteers used a common sequence of motions from one step in the process to the next. Using this information enabled them to build the control system to provide maximum efficiency. 

The control system that has been built is intelligent enough to detect the movement of the volunteers be they lying on their side, front or back. Having learned how people usually get up from such positions the system can detect the movement and provide suitable assistance to help. 

The team hope that the benefits of the system will go further than just helping the astronauts recover. By making it easier to get up, the astronauts will be able to conserve energy for other important tasks. With Artemis just around the corner and a return to human lunar exploration, it may well be that the ‘SuperLimbs’ will soon be a regular sight on human space explorers.

Source : Robotic “SuperLimbs” could help moonwalkers recover from falls

The post Astronauts Could Deploy Extra Arms to Stay Stable on the Moon appeared first on Universe Today.

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Some Supermassive Black Holes (SMBHs) consume vast quantities of gas and dust, triggering brilliant light shows that can outshine an entire galaxy. But others are much more sedate, emitting faint but steady light from their home in the heart of their galaxy.

Observations from the now-retired Spitzer Space Telescope help show why that is.

It appears that every large galaxy has an SMBH at its heart. This is true of our Milky Way galaxy and of our closest galactic neighbour, Andromeda (M31.) Like all black holes, SMBHs draw material towards them that gathers in an accretion disk. As the material in the disk rotates and heats up, it emits light before it falls into the hole.

It turns out that both of those SMBHs are among the quiet eaters in the black hole population. Others are much more ravenous, consuming large amounts of matter in clumps and shining brightly for periods of time. Astrophysicists wonder what’s behind the difference.

Recent research published in The Astrophysical Journal has determined what’s happening in these different black holes. The title is “The Accretion Mode in Sub-Eddington Supermassive Black Holes: Getting into the Central Parsecs of Andromeda.” The lead author is Christian Alig, a post-doc student at the Max Planck Institute for Extraterrestrial Physics.

Andromeda (M31) is a close neighbour in cosmic terms. It’s about 780 kiloparsecs away, or about 2.5 million light years. It’s a sub-Eddington SMBH, meaning that it hasn’t reached the theoretical maximum accretion rate. Its proximity makes it an excellent target for observing and studying large-scale galactic structure, especially the nucleus. The nucleus is where most of the action is, dominated by an SMBH and containing a dense population of stars and a network of gas and dust. This research focuses on the gas and dust.

“This paper investigates the formation, stability, and role of the network of dust/gas filaments surrounding the M31 nucleus,” the authors write in their research. “The proximity of M31, 780 kpc, allows us to visualize in great detail the morphology, size, and kinematics of the filaments in ionized gas and dust.”

The researchers worked with images from the Hubble and Spitzer Space Telescopes. Using different filters, the telescope images revealed the shape and other characteristics of the network of gas and dust. “The appearance of the central region of M31 varies dramatically in the different mid-infrared bands, from a smooth, featureless bulge dominated by the old stellar population at 3.6 ?m to the distinct spiral dust filament structure that dominates the 8 ?m image,” the authors explain.

These images from the research show how different telescopes and filters can work together to reveal structure. The top row is Spitzer images of M31 at different wavelengths. Structure emerges successively with each image. The bottom right image is the 8 ?m image minus the 4.5 ?m image, which basically removes starlight. The middle right bottom image is a Hubble image showing H-alpha and ionized nitrogen. The bottom left image is a Hubble UV image, and the middle left is the same image with starlight removed. Image Credit: Alig et al. 2024.

The researchers found a circumnuclear dust ring around the galactic nucleus that measures between 0.5 and 1 kpc from the center (1,630 to 3,260 light-years.) Filaments of dust emanate from this ring, forming a spiral inside it. “Inside the ring, the dust filaments follow circularized orbits around the center, ending in a nuclear spiral in the central hundred parsecs,” the authors explain.

These images from the research successive zoom-ins at different wavelengths. In the middle image, a dotted white line outlines the circumnuclear ring in M31. The third image “… is a pure dust map of the central kiloparsec of M31,” the authors write. In the third image, an arrow shows the filament used as a reference in simulations. Image Credit: Alig et al. 2024.

After identifying structures in the telescope images, the researchers turned to simulations. They used hydrodynamical simulations to see what initial conditions made filaments and streamers of flowing gas move nearer to the SMBH. “By predicting the orbit and velocity of the filaments, we aim to infer the role of the nuclear spiral as a feeder of the M31 BH,” they explain.

The hydrodynamical simulations cover a wide area of the nucleus, from 900 parsecs to 6 parsecs from the SMBH in M31. The starting point for the simulations is the brightest and longest dust filament the team found in the images. In the image above, it’s marked with a white arrow. “The filament curves progressively toward the center as it approaches,” the researchers write. “It is also seen in the ionized gas <H-alpha and NII> though more diffuse, in the central few hundred parsecs.”

The simulations assume that the dust filament is made of dust infalling from the circumnuclear ring, though the researchers didn’t investigate how the dust made its way into the ring in the first place. The simulation began by injecting gas into the ring. The team let the simulation fun for millions of years to see how the gas behaves. “In the end, we needed about 200 Myr of simulation time to arrive at a configuration that best reproduces the observations,” the authors explain.

This figure shows snapshots from the simulation at different intervals from 17.5 million years to 156 million years. (a) and (b) don’t deviate much from an N-body simulation, but eventually, a ring takes shape. In (b,) the freshly injected material collides with the uppermost arc. That heats up the gas, creating a hot surrounding atmosphere shown in blue/pink. The stream crosses itself repeatedly after that and experiences friction from the atmosphere. (d) through (f) shows how the gas eventually circularizes into a ring shape. Image Credit: Alig et al. 2024.

“Friction at the inner edge of an elongated ring structure that forms in (e) causes thin filaments to spiral inward, eventually forming a small disk in the inner 100 pc, visible in (f),” the authors explain.

All of the team’s simulations arrived at similar results, even though they began with different parameters like initial angles, velocities, distances, and angle of injection. “Interestingly, due to the relatively good radial symmetry of the M31 potential in the inner 1 kpc, all simulations lead to very similar results,” the researchers explain.

The observations and images of M31’s inner region are in line with what astronomers find in other quiet galaxies. Those surveys “… reveal a common pattern in the dust morphology, formed by narrow, long dust filaments ending in a spiral in the central few hundred parsecs,” the authors write. The majority of low-luminosity galaxies in a 2003 study also have nuclear spirals that span several hundred parsecs.

Interestingly, high-accreting galaxies different than M31 also show a network of dust lanes and filaments, but their morphology is less organized. It often consists of one long filament that runs right across the nucleus. This could be the critical difference between the sedate SMBH in M31 and galaxies with much brighter black holes.

M31 and its ilk are fed a slow, steady diet of gas, which means their brightness is steady. But other galaxies are fed matter in larger clumps, which makes their brightness reach brilliant peaks, outshining all the stars in their galaxy. That’s the difference between gluttonous SMBHs and well-behaved ones.

“The hydrodynamical simulations show that the role of these filaments <in M31> is to transport matter to the center; however, the net amount that they transport to the center is small—a consequence of their extensive interaction with themselves, their surrounding atmosphere, and the ISM over a timescale of several million years,” the authors conclude. “We postulate that when dust/gas filaments in the central hundred parsecs of galaxies get to settle in a nuclear spiral configuration, a low accretion mode of the central BH will result.”

So galaxies with spiral patterns of gas in their nuclei have low accretion modes and lower, steadier luminosity. Galaxies without these patterns accrete more matter irregularly, and their luminosity surges.

One of the interesting things about this research is that it didn’t rely on new observations from new, powerful telescopes like the JWST. Instead, it relied on images from NASA’s Spitzer Space Telescope, which ended its mission in January 2020. It illustrates how modern telescopes and observatories generate massive amounts of data that scientists can utilize in different ways long after the telescope’s mission has ended.

“This is a great example of scientists reexamining archival data to reveal more about galaxy dynamics by comparing it to the latest computer simulations,” said study co-author Almudena Prieto, an astrophysicist at the Institute of Astrophysics of the Canary Islands and the University Observatory Munich. “We have 20-year-old data telling us things we didn’t recognize in it when we first collected it.”

The post Not All Black Holes are Ravenous Gluttons appeared first on Universe Today.

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