# What is that light of the middle of the milky way galaxy?

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I'm Being confused what is that light in the middle of milky way galaxy?

Image is from Charting the Milky Way From the Inside Out

The text with the image explains a lot about the spiral arms and the location of the Earth, but the central bright area isn't explained in great depth.

The galactic bulge is formed by tightly packed stars and interstellar dust Also most stars are in the direction towards the galactic center Thus it would appear brightest if it were viewed from outside the plane of the galaxy as this image is intended to show.

However, we don't see this from Earth, and the reason why is explained in Phys.org's Why can't we see the center of the Milky Way? explains why we don't see this at night.

A brief outline of what is described there is as follows:

When it is dark enough, and conditions are clear, the dusty ring of the Milky Way can certainly be discerned in the night sky. However, we can still only see about 6,000 light years into the disk with the naked eye, and relying on the visible spectrum. Here's a rundown on why that is.

• Size and Structure
• Low Surface Brightness
• Dust and Gas
• Limited Instrumentation

However we could see a bright spot if we were outside the Earth's atmosphere and could see in certain wavelengths of infrared. The article shows the following image from COBE

Milky Way in infrared. Credit: COBE Source

False-color image of the near-infrared sky as seen by the DIRBE. Data at 1.25, 2.2, and 3.5 µm wavelengths are represented respectively as blue, green and red colors. The image is presented in Galactic coordinates, with the plane of the Milky Way Galaxy horizontal across the middle and the Galactic center at the center. The dominant sources of light at these wavelengths are stars within our Galaxy. The image shows both the thin disk and central bulge populations of stars in our spiral galaxy. Our Sun, much closer to us than any other star, lies in the disk (which is why the disk appears edge-on to us) at a distance of about 28,000 light years from the center. The image is redder in directions where there is more dust between the stars absorbing starlight from distant stars. This absorption is so strong at visible wavelengths that the central part of the Milky Way cannot be seen. DIRBE data will facilitate studies of the content, energetics and large scale structure of the Galaxy, as well as the nature and distribution of dust within the Solar System. The data also will be studied for evidence of a faint, uniform infrared background, the residual radiation from the first stars and galaxies formed following the Big Bang.

## Researchers Map Light Energy Distribution in Milky Way Galaxy

An all-sky image of the Milky Way Galaxy, as observed by ESA’s Planck Space Observatory in IR. The data contained in this image were used in this research and were essential in calculating the distribution of the light energy of the Galaxy. Image credit: ESA / HFI / LFI consortia.

The research, published in the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint), shows how the stellar photons within the Milky Way control the production of the gamma-rays — the highest energy photons in the Universe.

This was made possible using a new method involving computer calculations that track the destiny of all photons in the Galaxy, including the photons that are emitted by interstellar dust, as infrared (IR) light.

“We have not only determined the distribution of light energy in the Milky Way, but also made predictions for the stellar and interstellar dust content of our Galaxy,” said University of Central Lancashire Professor Cristina Popescu, lead author of the study.

Previous attempts to derive the distribution of all light in the Milky Way based on star counts have failed to account for the all-sky images of the Milky Way, including recent images provided by the Planck observatory, which map out IR light.

By tracking all stellar photons and making predictions for how the Milky Way should appear in ultraviolet (UV), IR, and visual radiation, Professor Popescu and co-authors have been able to calculate a complete picture of how stellar light is distributed throughout the Galaxy.

An understanding of these processes is a crucial step towards gaining a complete picture of our Galaxy and its history.

The modeling of the distribution of light in the Milky Way follows on from previous research that the team conducted on modeling the stellar light from star-forming galaxies in the nearby Universe.

“It has to be noted that looking at galaxies from outside is a much easier task than looking from inside, as in the case of our Galaxy,” said co-author Dr. Richard Tuffs, of the Max Planck Institute for Nuclear Physics.

The authors have also been able to show how the stellar light within our Galaxy affects the production of gamma-ray photons through interactions with cosmic rays.

“Cosmic rays are high-energy electrons and protons that control star and planet formation and the processes governing galactic evolution,” they said.

“They promote chemical reactions in interstellar space, leading to the formation of complex and ultimately life-critical molecules.”

“Working backwards through the chain of interactions and propagations, one can work out the original source of the cosmic rays,” Dr. Tuffs said.

## What is that light of the middle of the milky way galaxy? - Astronomy

Determining the structure of our galaxy is not an easy task because the solar system is stuck inside the Galaxy and we can only look in all different directions. Our situation is like you having to determine the layout of your hometown from just looking out on your front porch (or back porch) and not being able to move even across the street. The fact that you see a narrow band of stars tells you that our galaxy is shaped like a thin disk. If we lived in a more spherical galaxy, the stars would be distributed more uniformly across the sky. If we lived in an irregular galaxy, there would be
patchier distribution of material in various parts of the sky instead of the narrow band of stars. There is a hint of a bulge in the direction of the Sagittarius constellation (toward the Galaxy center). Careful star counts and determining their distances shows hints of a spiral pattern in the disk. The interstellar dust limits our view a small section of the Galaxy. However, clear evidence of the spiral structure in the disk comes from the 21-cm line radiation discussed in the previous section.

Our galaxy, the Milky Way, is disk-shaped with spiral arms in the disk. It has an elliptical bulge in the center with a bar-shaped distribution of gas/dust/stars going through the middle out of which the spiral arms extend and a spherical halo of stars that is denser closer to the Galaxy center. The disk of stars is about 100,000 light years across but only about 1000 light years thick (the dust layer is even thinner). The bar going through the middle of the bulge is about 25,000 by 4000 light years in dimension. Our solar system is about two-thirds of the way out from the center in a spur off one of the major spiral arms. For comparison, our solar system with the Oort Cloud is about 1 light year across. If Pluto's orbit were fit inside a U.S. quarter coin (so 80 AUs scaled to 24.26 mm), the Oort Cloud would be about 19 meters across, the next star system (Rigel Kentaurus & companions) would be about 84 meters away and the Galaxy would be about 1920 kilometers across (select the figure below to bring up a larger version).

You can make a rough guess of the number of stars in our galaxy by dividing the Galaxy's total mass by the mass of a typical star (e.g., 1 solar mass). The result is about 200 billion stars! The actual number of stars could be several tens of billions less or more than this approximate value. The disk contains over 98% of the dust and gas in the Galaxy. The bulge is made of a few tens of billions of stars while the stellar halo that extends out from it contains several hundreds of millions of stars. Most of the globular clusters are in the stellar halo and, like the halo stars, the number of them increases toward the galactic center. Astronomers have discovered that most of the mass of the Galaxy (and other galaxies) is not in the form of stars, gas, or dust. It is made of some other material, as yet unknown, and is given the descriptive name dark matter''. Note that this affects your guess of the number of stars in the galaxy! (Does it increase the number or decrease it?) The dark matter halo may extend out two or three times the extent of the stars.

Our galaxy probably closely resembles the galaxy NGC 891 as seen edge-on. Note the prominent dust lanes going through the disk mid-plane and how flat the galaxy is.

## Gargantuan 'Bubbles' of Radio Energy Spotted at the Center of Our Galaxy. How'd They Get There?

Two huge bubbles of radio energy swirling out of the Milky Way's middle could be evidence of an ancient cosmic explosion — or maybe the start of a new one.

A few million years ago, the center of the Milky Way experienced a bout of bad gas.

Suddenly, some unknown quantity of matter and electromagnetic energy swirling near our galaxy's central black hole erupted in a gargantuan explosion. Electrons moving at nearly the speed of light tore into nearby clouds of dust and gas, causing them to balloon into two enormous, nearly identical bubbles of invisible energy. They're still there today, each one towering some 25,000 light-years high (about a quarter of the width of the Milky Way itself), but you won't see them unless you have an eye for the most energetic radiation in the universe.

Astronomers discovered these galactic fart bubbles in 2010, while looking toward the center of the galaxy with NASA's Fermi Gamma-ray Space Telescope. Now known as the Fermi Bubbles, these massive, gassy blobs appear only in X-ray and gamma-ray light, teasing at an ancient and extremely powerful origin. How and when this galactic bubble-blowing blast occurred, astronomers can't say. But in a new study published today (Sept. 11) in the journal Nature, an international team of researchers reported some fresh clues found by looking to the opposite end of the electromagnetic spectrum, at radio waves.

Using a radio telescope array called MeerKAT to look through the dust clouding our galaxy's navel, researchers in South Africa have detected a pair of bubble-like radio-wave structures bulging out of the galactic center right next to the Fermi Bubbles. While these "radio bubbles" appear much smaller and much less energetic than the frenetic Fermi Bubbles, they likely originated from a similarly cataclysmic event involving our galaxy's central black hole. They may even be part of an ongoing process that's slowly fueling the Fermi Bubbles' inflation, the researchers wrote.

"The Milky Way's central black hole can, from time to time, become uncharacteristically active, flaring up as it periodically devours massive clumps of dust and gas," study co-author Ian Heywood, an astrophysicist at the University of Oxford in the United Kingdom, said in a statement. "It's possible that one such feeding frenzy triggered powerful outbursts that inflated this previously unseen feature."

Heywood and his colleagues detected the radio bubbles while searching the galaxy's center for a very specific band of short wavelengths that correspond to a type of energy called synchrotron radiation. The process occurs when electrons moving at near light speed collide with magnetic fields, resulting in a distinct radio signal. While mapping this signal near the center of the galaxy, the study authors discovered a long oval of radio energy spanning about 1,400 light-years in diameter, with the galaxy's central black hole sitting at the middle.

Based on the speed of gas flowing near the bottom of the radio bubbles, the researchers estimated the structures to be about 7 million years old, which aligns with younger estimates for the ages of the Fermi Bubbles. It's possible, then, that the two sets of bubbles resulted from the very same cosmic eruption — or, at least, the same sort of explosion.

"The shape and symmetry of [the radio bubbles] strongly suggest that a staggeringly powerful event happened a few million years ago very near our galaxy's central black hole," study co-author William Cotton, an astronomer with the U.S. National Radio Astronomy Observatory, said in the statement. "This eruption was possibly triggered by vast amounts of interstellar gas falling in on the black hole or a massive burst of star formation which sent shock waves careening through the galactic center."

Alternatively, the radio bubbles may be a sign of a new galaxy-scale explosion in the making, the researchers wrote. Given their relatively small size and low energy, the radio bubbles could be the result of small-scale energy bursts that, over millions of years, fuel much larger explosions, creating vast, high-energy clouds like the Fermi Bubbles.

While the detection of these newfound energy bubbles won't solve any mysteries, it does add another piece to the puzzle that is the Milky Way's middle. Seething with giant bubbles of both low-energy and high-energy radiation, our central black hole's indigestion clearly hasn't passed yet.

## The Milky Way’s ‘yellowballs’ are clusters of baby stars

The Milky Way is strewn with ‘yellowballs’ (green circles), as seen in this false-color infrared panorama from the Spitzer Space Telescope. These regions of ionized gas bubbles are where baby stars are born.

Charles Kerton/Iowa State University, Spitzer/NASA

Astronomers have cracked a curious cosmic case: What are “yellowballs”? These mysterious space objects were first thought to be signs of young, supermassive stars. Scientists now have confirmed that they do mark stellar nurseries. But these birthplaces for stars can host many types of stars with a wide range of masses.

Researchers shared their discovery April 13 in The Astrophysical Journal.

The stars in the clusters are relatively young, only about 100,000 years old. “I think of these as stars in utero,” says Grace Wolf-Chase. She’s an astronomer at the Planetary Science Institute and lives in Naperville, Ill. For comparison, massive stars forming in the Orion nebula are already 3 million years old. Our sun, at 4.6 billion years old, is considered middle-aged.

Volunteers with the Milky Way Project were the first to spot the unknown objects. The splotches showed up in pictures of the galaxy taken by the Spitzer Space Telescope. That telescope, which worked until last year, saw the cosmos in infrared light. And Spitzer’s images were like a sort of stellar ultrasound. They let astronomers “probe what’s going on in these cold environments before the stars are actually born,” explains Wolf-Chase.

Astronomers first thought “yellowballs” (circled left) were precursors to gas bubbles blown around massive, young stars (right). A new study instead suggests yellowballs are actually clusters of smaller stars. JPL-Caltech/NASA

Citizen scientists had been scouring the images for signs of baby stars and their birthplaces. The babies were expected to be at least 10 times the mass of our sun. And they blow giant bubbles of gas that is electrically charged, or ionized. A year or two into the project, some users noted small yellow blobs in the false-color images. They began tagging the objects #yellowballs. Between 2010 and 2015, the volunteers found 928 such yellowballs.

Wolf-Chase’s team first thought the balls signaled early-stage gas bubbles. But the researchers wanted more data to get a better look. The first yellowballs to be tagged were a lucky discovery. The researchers knew they probably hadn’t caught enough of them to definitively ID these objects. In 2016, the team asked volunteers with the Milky Way Project to find more. By the next year, that group had spotted more than 6,000 additional yellowballs.

Wolf-Chase and colleagues studied about 500 of those balls more closely. They compared the balls to catalogs of star clusters and other known structures to figure out what they were. “Now we have a good answer: They’re infant star clusters,” Wolf-Chase says. The clusters blow ionized gas bubbles of their own. Their bubbles are similar to the ones blown by single young, big stars.

Wolf-Chase hopes the work will help researchers spot yellowballs with newer telescopes. One, the James Webb Space Telescope, is due to launch in October. Such images could reveal more about the balls’ physical traits.

### Power Words

astronomer: A scientist who works in the field of research that deals with celestial objects, space and the physical universe.

citizen science: Scientific research in which the public — people of all ages and abilities — participate. The data that these citizen “scientists” collect helps to advance research. Letting the public participate means that scientists can get data from many more people and places than would be available if they were working alone.

colleague: Someone who works with another a co-worker or team member.

cosmos: (adj. cosmic) A term that refers to the universe and everything within it.

environment: The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).

galaxy: A group of stars — and usually dark matter — all held together by gravity. Giant galaxies, such as the Milky Way, often have more than 100 billion stars. The dimmest galaxies may have just a few thousand. Some galaxies also have gas and dust from which they make new stars.

infrared: A type of electromagnetic radiation invisible to the human eye. The name incorporates a Latin term and means “below red.” Infrared light has wavelengths longer than those visible to humans. Other invisible wavelengths include X-rays, radio waves and microwaves. Infrared light tends to record the heat signature of an object or environment.

mass: A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.

Milky Way: The galaxy in which Earth’s solar system resides.

nebula: A cloud of space gas and dust existing between major adult stars. Telescopes can detect these clouds by the light they emit or reflect. Some nebulas also appear to serve as the nurseries in which stars are born.

physical: (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).

planetary science: The science of planets other than Earth.

range: The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which variation in values is possible. Also, the distance within which something can be reached or perceived.

star: The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become hot enough, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.

stellar: An adjective that means of or relating to stars.

sun: The star at the center of Earth’s solar system. It is about 27,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.

telescope: Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.

ultrasound: (adj. ultrasonic) Sounds at frequencies above the range that can be detected by the human ear. Also the name given to a medical procedure that uses ultrasound to “see” within the body.

### Citations

Journal:​ ​​G. Wolf-Chase et al. The Milky Way Project: Probing star formation with first results on yellowballs from DR2. The Astrophysical Journal. Vol. 911, April 13, 2021. doi: 10.3847/1538-4357/abe87a.

Lisa Grossman is the astronomy writer. She has a degree in astronomy from Cornell University and a graduate certificate in science writing from University of California, Santa Cruz. She lives near Boston.

## Our Milky Way Galaxy

On a clear, dark night, you can see a glowing stream that seems to split the sky. We have called it the Milky Way Galaxy for thousands of years, and its exact nature was a mystery until less than a hundred years ago.

Although early telescopes resolved the Milky Way Galaxy into individual stars, we needed to measure the distances to and motions of these stars before a three-dimensional picture emerged: The band of stars has a depth, it encircles us, and the Sun and nearest stars are also within it.

Like a chocolate chip in the middle of a cookie, its view is of a thin disk of cookie, other chips, and then space all around. Our Sun is one of hundreds of billions of stars embedded in a large disk.

#### What Elements Are Forming The Milky Way Galaxy?

Radio data from the VLBA show movement in the giant gas clouds near the Sun to be similar to movement of clouds in the nearby giant arm of Perseus. Our galactic neighborhoods are joined.

Elsewhere in deeper space, disk-shaped collections of stars are plentiful, and we refer to them as spiral galaxies. Spiral galaxies get their name for the alternating bands of bright starry and dark dusty gas swirls that pinwheel off of a bright, central core.

The arms of spiral galaxies are packed with gas and dust, and light-years of that material acts like a blanket the blocks our view beyond it. Radio waves can make their way through,

In the crowded conditions of star-forming regions in the Milky Way’s spiral arms, tightly-packed clouds of water and methanol molecules boost radio waves in the same fashion that a laser boosts light waves.

Like a sponge, these clouds soak up the incoming photons until their molecules are saturated with extra energy. Incoming photons innocently arriving into a supersoaked cloud cause an explosion of energy: As the first molecule spits out its extra energy, that energy triggers the neighboring molecule to also spit out its extra, and so on.

This cascade of energy turns the cloud into a cosmic laser that shines in microwave-length radio waves, so we call it a MASER (Microwave Amplification by Stimulated Emission of Radiation). As long as it remains close to the energy source, the cloud soaks up and releases energy constantly.

With the Very Long Baseline Array, we use masers like glowsticks to trace deeper, arm after arm, nearly through the entire thickness of the disk to construct an accurate map of our Milky Way Galaxy.

The picture we have now is a Milky Way Galaxy about 100,000 light-years across (a light-year being a distance of about six trillion miles). It has a few major arms: The Sagittarius Arm is closer to the Galactic center and the Perseus Arm is farther out in the Galaxy. Our Solar System is nestled on its own spiral arm, called the Local Arm, between these two.

A faint trail of gas connects the Milky Way to its companion galaxies, the Magellanic Clouds. This indicates we had a close brush over 2 billion years ago that stripped gas from the smaller galaxies.

#### How Dust is Connecting Us to Our Milky Way Galaxy?

Dust is the atomic ash of exploded stars, the heavier molecules and elements used to make new stars, planets, and people. Inside collapsing gas and dust clouds lay countless areas of star and planet formation.

The gaseous, dusty clumps in a spiral galaxy’s arms are where the action is.

Frustratingly, dust diverts the passage of visible light, and these tantalizing regions appear like dark, impenetrable chestnuts to optical telescopes.

Radio waves, however, travel through the dusty shells of these veiled regions, so to a radio telescope, they glow clearly. Radio telescopes are the tools used to probe the hidden activities within and beyond our Milky Way Galaxy’s dusty lanes.

We see the complex, swirling feeder disks of gas and dust collecting onto a central core that will eventually start shining as a star. And because radio telescopes can measure the magnetic fields of radio objects, radio telescopes like the VLA, map the burps of excess gas traveling along the magnetic poles of young stars when they first start to shine.

Most stars in our galaxy are siblings, and the VLA has captured images of a few cloud systems where stellar siblings will soon shine.

With shorter wavelength-gathering radio telescopes, such as ALMA, we plot the particles of dust traveling around future suns. We see the traffic jams, merges, and open lanes that are evidence of planets forming in the young disk.

We can also see exactly where certain gases start to freeze out into solids, called the “snow zones.” Snow zones mark where materials can start to stick together, like snowballs, to make larger and larger bodies.

#### A Violent Heart At the Center of Our Milky Way Galaxy

Our Milky Way is a spiral galaxy. Just a portion of it, seen in radio waves, shows the telltale bubbles, nuggets, and streams caused by the births and deaths of stars typical of spiral galaxies elsewhere in the Universe.

The heart of our spiral Galaxy broadcasts radio waves so powerfully that it startled an antenna engineer into discovering an entirely invisible Universe.

While identifying sources of static for wireless radio transmissions in the early 1930s, Jansky discovered a huge source of radio noise coming from what he learned to be the center of the Milky Way Galaxy, behind the constellation of Sagittarius. Later observations with more powerful radio telescopes confirmed a radio bright, compact area that has been labeled Sagittarius A.

To more finely locate the Milky Way Galaxy’s bright heart, we built a higher resolution instrument called the Green Bank Interferometer in West Virginia in the 1960s. Three antennas watched Sag A, and we combined their data to give us greater detail of the Sag A area.

We found a pinpoint of radio light within the giant Sag A area, so small that it could only be coming from a compact but powerful object, such as a black hole. The source became known as Sagittarius A*.

The VLA has since mapped the entire neighborhood around Sgr A*, seen how stars orbit at ridiculous speeds around it, spotted where its magnetic field has dragged charged gas into huge streams, and discovered where new stars manage to still form in its wake. From these observations, we now know Sgr A* to be a supermassive black hole, millions of times the mass of our Sun.

The mini-spiral at the heart of the Milky Way is caused by gas and dust caught in orbit around a supermassive black hole, called Sagittarius A*.

#### Dwarf Companions Vs Milky Way Galaxy

Like stars, galaxies seem to also form in groups. These so-called “clusters” of galaxies have a diverse range of galaxy sizes and shapes. Our Milky Way Galaxy is a member of the Local Group of galaxies whose members range from our twin spiral, Andromeda, down to little companion dwarf galaxies that hover around us.

Sky watchers in the southern hemisphere have noted these “clouds” for millennia, but only recently have we been able to determine their structure and history.

The dwarf galaxies, called the Magellanic Clouds, are roughly one-tenth the size of the Milky Way and resemble miniature versions of it. They have central cores, many bright star-forming regions, and even crude spiral structures.

Radio telescopes found that these little galaxies have a larger percentage of gas in them than the Milky Way. However, they may have had even more, as a large stream of gas points back to them from our Galaxy.

Proud makers of stars, these little galaxies likely had a burst of star-formation billions of years ago, and the collective shining of their big, new stars fountained loose gas outward. The gravity of the Milky Way snatched the stray gas and has been pulling it in ever since.

## An X-Ray Hourglass Is Emerging From the Middle of the Milky Way

Astrophysicists conducting a survey of our very own Milky Way galaxy with an X-ray telescope aboard a satellite spotted a pair of enormous plasma bubbles, reports Leah Crane for New Scientist.

The blobs of hot gas extend more than 45,000 light years above and below the disc of the Milky Way itself, according to new research published in the journal Nature. That’s almost as tall as the entire galaxy is wide—the Milky Way measures around 105,000 light years across.

Researchers had actually already spotted what they’re calling the “northern bubble,” but the fainter “southern bubble” has just come into view. Without the southern bubble, astronomers couldn’t be sure if the northern bubble was actually emanating from the middle of the Milky Way as it appeared to be, or if it was just some trick of perspective making it appear that way. Now, armed with the bigger picture, researchers are more confident that both bubbles are emerging from the center of the galaxy, according to a statement.

If you’re especially knowledgeable about galactic bubbles, news of this inconceivably large hourglass-shaped structure may remind you of the Fermi Bubbles that were first discovered in 2010, reports Emily Conover for Science News. These mysterious balloons also extend above and below the Milky Way, but each one only extends about 25,000 light years from our galaxy’s center. Nobody is quite sure what produced the Fermi Bubbles. They got spotted because they emit gamma rays, which, just like X-rays, are part of the electromagnetic spectrum but are even higher energy.

A diagram showing the Fermi bubbles (purple) nested inside the newly discovered eROSITA bubbles (yellow). The Milky Way's disc is illustrated as a swirling blue plane in the middle. (Max Planck Institute for Extraterrestrial Physics)

Because the gamma ray emitting Fermi Bubbles nest inside this newly confirmed pair of plasma bubbles visible in the X-ray spectrum, researchers suspect that all four may have been caused by a single, stupendously powerful galactic event.

One possibility is a shock wave rippling out from the birth of a star near the center of the galaxy, but, per New Scientist, it’s uncommon for star formation to produce shock waves as powerful as the one implicated by this quartet of high-energy bubbles. Researchers say a more likely scenario may be that the balloons of hot gas are outbursts from the supermassive black hole at the galactic center. Outbursts may be putting it politely, as some outlets have taken to calling these emissions “burps” because they are thought to come after a black hole has “eaten” a star or some other celestial body.

“It would be no problem to have a little bit of gas falling onto the black hole and releasing the energy required to inflate these bubbles,” Andrea Merloni, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics who helped discover the plasma bubbles using the eROSITA X-ray telescope, tells New Scientist. According to the statement, in either scenario the energy needed to produce the massive bubbles would be roughly equivalent to 100,000 supernovae.

The eROSITA X-ray telescope is nestled aboard the Russian-German Spektr-RG space observatory satellite. The X-ray telescope searches the entire sky twice a year looking for new features and mapping the universe’s structure and rate of expansion--something that may help us get a better grasp of dark energy, reports Tim Childers for Popular Mechanics. The eROSITA mission is planned to last another six years or more, so more details about how the Milky Way blew these high-energy bubbles will hopefully emerge in years to come.

## This is the Core of the Milky Way, Seen in Infrared, Revealing Features Normally Hidden by Gas and Dust

The world’s largest airborne telescope, SOFIA, has peered into the core of the Milky Way and captured a crisp image of the region. With its ability to see in the infrared, SOFIA (Stratospheric Observatory For Infrared Astronomy) is able to observe the center of the Milky Way, a region dominated by dense clouds of gas and dust that block visible light. Those dense clouds are the stuff that stars are born from, and this latest image is part of the effort to understand how massive stars form.

One of the mysteries in the core region of our galaxy involves the formation of stars, particularly massive ones. While the region contains much more gas and dust than other regions of the galaxy, fewer massive stars form there: 10 times fewer than expected. Untangling the reasons for that is difficult because of the intervening gas and dust between Earth and the core.

Astronomers working with SOFIA captured an image that may shed light on the birth of massive stars. Scientists combined SOFIA’s power with NASA’s Spitzer Space Telescope and the ESA’s Herschel Space Observatory to get this image. The image shows the Arches Cluster, which contains the densest concentration of stars in the Milky Way. It also highlights the Quintuplet Cluster, which is home to stars a million times more luminous than the Sun. Both clusters are about 100 light years from the Milky Way’s galactic center.

Arches Cluster (L) and the Quintuplet Cluster (R.) Though the Quintuplet Cluster was named for the first five stars observed there, we now know the cluster contains a huge number of massive young stars, just like the Arches Cluster. Image Credit: (L) By ESO/P. Espinoza – http://www.eso.org/public/images/eso0921a/, CC BY 3.0. (R) By ESA/Hubble, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=41549596

SOFIA is designed to bypass the Earth’s atmosphere and all the problems it poses for infrared astronomy, without the expense of a space telescope. SOFIA’s FORCAST instrument (Faint Object Infrared CAmera for the SOFIA Telescope) can see material in the core of the galaxy that’s warm and emits infrared light in a wavelength that other telescopes can’t. By combining FORCAST’s data with data from the Spitzer and Herschel space telescopes, astronomers created a composite image showing new details.

“It’s incredible to see our galactic center in detail we’ve never seen before. Studying this area has been like trying to assemble a puzzle with missing pieces.”

James Radomski, Universities Space Research Association scientist, SOFIA Science Center, NASA’s Ames Research Center
<Click to enlarge.> A composite infrared image of the core of the Milky Way galaxy. The image is 600 light years across. Blue and green (25 and 36 microns) is from SOFIA’s FORCAST instrument, red (70 microns) is from the Herschel Space Observatory, and white (8 microns) is from the Spitzer space telescope. Image Credit: NASA/SOFIA/JPL-Caltech/ESA/Herschel

A paper highlighting early results from this work has been submitted to The Astrophysical Journal. The image was also presented for the first time at the 2020 annual meeting of the American Astronomical Society.

James Radomski is a Universities Space Research Association scientist at the SOFIA Science Center at NASA’s Ames Research Center in California’s Silicon Valley. In a press release, Radomski said “It’s incredible to see our galactic center in detail we’ve never seen before. Studying this area has been like trying to assemble a puzzle with missing pieces. The SOFIA data fills in some of the holes, putting us significantly closer to having a complete picture.”

The data is giving astronomers a new, detailed look at structures near the Quintuplets Cluster that may indicate star birth. It also shows some warm material near the Arches Cluster that could be the seeds for the formation of new stars. This new high-resolution look at these features could be a clue to how some of the most massive stars can from so close to each other in a small region, while the surrounding areas show a surprisingly low rate of star birth.

“Understanding how massive star birth happens at the center of our own galaxy gives us information that can help us learn about other, more distant galaxies,” said Matthew Hankins, a postdoctoral scholar at the California Institute of Technology in Pasadena, California and principal investigator of the project. “Using multiple telescopes gives us clues we need to understand these processes, and there’s still more to be uncovered.”

The Milky Way’s core is a region of complex magnetic fields that may influence star formation. This is a representation of how our Galaxy would look in the sky if we could see magnetic fields. The plane of the Galaxy runs horizontally through the middle, and the Galactic centre direction is the middle of the map. Red–pink colours show increasing Galactic magnetic field strengths where the direction is pointing towards the Earth. Blue–purple colours show increasing Galactic magnetic field strengths where the direction is pointing away from the Earth. Image Credit: Sobey et al, 2019.

There’s a lot to untangle when it comes to understanding star birth at the Milky Way’s core. The galactic core may be the most extreme region when it comes to the formation of stars. Though the region contains about 80% of the galaxy’s star-forming material, something is slowing down the process. It’s a region of complex magnetic fields, a powerful gravity well, dense molecular clouds, turbulence, and high temperatures.

At the core of the galaxy, the rate of star formation is only 0.1 solar masses per year out of the 1.2 solar masses per year produced by the entire galaxy. That’s 10 times less than predictions by current theoretical models. Scientists hope that this new image data will help make sense of the region and its lack of star birth.

But the low frequency of star birth in the Milky Way’s core is only one of the mysteries of that region. Another involves Sagittarius A-Star (Sgr. A*,) the supermassive black hole at the center of the galaxy.

An image of Sgr. A* (not from SOFIA.) Though quieter than other supermassive black holes, it still swallows material and emits high-energy radiation. In this case, it emitted an x-ray flare about 400 times brighter than its normal state. Image Credit: By NASA/CXC/Stanford/I. Zhuravleva et al.

A ring of material that’s about 10 light years in diameter surrounds Sgr. A*. Though Sgr. A* is quieter than its counterparts in other spiral galaxies, it still swallow material and emits high-energy radiation as a result. The ring of material plays an important role in feeding material into the black hole itself. But the origin of the ring itself is a puzzle, partly because the ring should get depleted over time. But the new data from SOFIA, Spitzer, and Herschel shows some structures in the region that could show new material being incorporated into the ring.

The data for these images was captured in July 2019 when SOFIA was operating near Christchurch, New Zealand, to study the southern skies.

## At the Largest Scales, Our Milky Way Galaxy is in the Middle of Nowhere

Ever since Galileo pointed his telescope at Jupiter and saw moons in orbit around that planet, we began to realize we don’t occupy a central, important place in the Universe. In 2013, a study showed that we may be further out in the boondocks than we imagined. Now, a new study confirms it: we live in a void in the filamental structure of the Universe, a void that is bigger than we thought.

In 2013, a study by University of Wisconsin–Madison astronomer Amy Barger and her student Ryan Keenan showed that our Milky Way galaxy is situated in a large void in the cosmic structure. The void contains far fewer galaxies, stars, and planets than we thought. Now, a new study from University of Wisconsin student Ben Hoscheit confirms it, and at the same time eases some of the tension between different measurements of the Hubble Constant.

The void has a name it’s called the KBC void for Keenan, Barger and the University of Hawaii’s Lennox Cowie. With a radius of about 1 billion light years, the KBC void is seven times larger than the average void, and it is the largest void we know of.

The large-scale structure of the Universe consists of filaments and clusters of normal matter separated by voids, where there is very little matter. It’s been described as “Swiss cheese-like.” The filaments themselves are made up of galaxy clusters and super-clusters, which are themselves made up of stars, gas, dust and planets. Finding out that we live in a void is interesting on its own, but its the implications it has for Hubble’s Constant that are even more interesting.

Hubble’s Constant is the rate at which objects move away from each other due to the expansion of the Universe. Dr. Brian Cox explains it in this short video.

The problem with Hubble’s Constant, is that you get a different result depending on how you measure it. Obviously, this is a problem. “No matter what technique you use, you should get the same value for the expansion rate of the universe today,” explains Ben Hoscheit, the Wisconsin student who presented his analysis of the KBC void on June 6th at a meeting of the American Astronomical Society. “Fortunately, living in a void helps resolve this tension.”

There are a couple ways of measuring the expansion rate of the Universe, known as Hubble’s Constant. One way is to use what are known as “standard candles.” Supernovae are used as standard candles because their luminosity is so well-understood. By measuring their luminosity, we can determine how far away the galaxy they reside in is.

Another way is by measuring the CMB, the Cosmic Microwave Background. The CMB is the left over energy imprint from the Big Bang, and studying it tells us the state of expansion in the Universe.

This is a map of the observable Universe from the Sloan Digital Sky Survey. Orange areas show higher density of galaxy clusters and filaments. Image: Sloan Digital Sky Survey.

The two methods can be compared. The standard candle approach measures more local distances, while the CMB approach measures large-scale distances. So how does living in a void help resolve the two?

Measurements from inside a void will be affected by the much larger amount of matter outside the void. The gravitational pull of all that matter will affect the measurements taken with the standard candle method. But that same matter, and its gravitational pull, will have no effect on the CMB method of measurement.

“One always wants to find consistency, or else there is a problem somewhere that needs to be resolved.” – Amy Barger, University of Hawaii, Dept. of Physics and Astronomy

Hoscheit’s new analysis, according to Barger, the author of the 2013 study, shows that Keenan’s first estimations of the KBC void, which is shaped like a sphere with a shell of increasing thickness made up of galaxies, stars and other matter, are not ruled out by other observational constraints.

“It is often really hard to find consistent solutions between many different observations,” says Barger, an observational cosmologist who also holds an affiliate graduate appointment at the University of Hawaii’s Department of Physics and Astronomy. “What Ben has shown is that the density profile that Keenan measured is consistent with cosmological observables. One always wants to find consistency, or else there is a problem somewhere that needs to be resolved.”

## Nasa unveils spectacular image of the Milky Way revealing the ‘heart’ of our galaxy

NASA has released a stunning new picture of our galaxy's violent, super-energized heart.

It's made up of 370 images snapped over the past two decades by the Chandra X-ray Observatory, which orbits Earth around 86,500 miles away.

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The image depicts billions of stars and countless black holes in the center, or heart, of the Milky Way.

A radio telescope in South Africa also contributed to the image, for contrast.

Astronomer Daniel Wang of the University of Massachusetts Amherst said Friday he spent a year working on this while stuck at home during the pandemic.

"What we see in the picture is a violent or energetic ecosystem in our galaxy's downtown," Wang said.

"There are a lot of supernova remnants, black holes, and neutron stars there.

"Each X-ray dot or feature represents an energetic source, most of which are in the center."

This busy, high-energy galactic center is 26,000 light years away.

His work appears in the June issue of the Monthly Notices of the Royal Astronomical Society.

### Milky Way facts

Here's what you need to know.

• The Milky Way galaxy is home to Earth and is almost as old as the Universe itself
• Recently estimates suggest the Universe is around 13.7billion years old, while the Milky Way is thought to be 13.6billion years old
• The Milky Way is disk-shaped and measures about 120,000 light years across
• It has a supermassive black hole in the middle called Sagittarius A*
• Our galaxy is thought to be home to more than 200billion stars
• It is thought to have an invisible halo made of dark matter

Launched in 1999, Chandra is in an extreme oval orbit around Earth. It specialises in X-ray radiation, allowing it to peer at cosmic events that no other telescope can.

The probe is sensitive to X-rays fired out by stars, galaxies and more that are 100 times fainter than those detectable by any previous X-ray telescope.

It has helped scientists make breakthrough discoveries about the life cycles of stars, black holes and more.

Chandra's mission was only supposed to last for five years but it's still going strong more than two decades after its launch.

### Science facts

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