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In our Milkyway all the stars are orbitting around the black hole in the center. But what is the cause it this rotation and are there galaxies where the stars aren't orbitting a center?
The cause of the rotation is that the hydrogen cloud that the galaxy condensed out of had some angular momentum which was conserved as the cloud collapsed into a galaxy.
The stars in a galaxy have to be in orbit around something. (Even if it's just the center of mass of the galaxy.) If they were at rest with respect to the center of mass, they'd fall into it!
Stars aren't really orbiting the center of a galaxy, as much as they're orbiting the gravitational potential of the galaxy. The galaxy doesn't need to have a black hole in the center for the stars to orbit, and even if it does (which in fact it does most of the time), the black hole does not dominate the gravitational potential, except in the most central part (see sphere of influence of a black hole).
All matter in the galaxy contributes to the gravitational potential, but since dark matter comprises 5/6 of the mass, this is the most important contributor. Only in the hypothetical case of a perfectly symmetrical distribution of masses, would the black hole and the center of rotation coincide. And since the paths of the stars are ellipses and not perfect circles, the center of the potential will not lie in the center of their orbits, but in one of the focal points. Furthermore, galaxies are dynamical and the potential continually changes, in turn changing the exact orbit of a star.
Galaxies form due to the collapse of a dark matter halo, and the gas that follows along. Such a halo will in general have a non-zero angular momentum, which is partially conserved during the collapse (they do lose a significant amount, for instance through minor and major merging; see e.g. D'Onghia et al. 2006).
As in the case of a forming star, a forming planet, an ice skater, or you on an office chair, reducing the radius means increasing orbital speed. This is the origin of the rotation.
New Stars Turn Galaxies Pink, Even Though There Are No 'Pink Stars'
The nearby Triangulum galaxy, one of the closest spirals to us in the Universe. The pink color . [+] tracing the spiral arms is strong evidence of new star formation.
European Southern Observatory (ESO)
If you look through a telescope's eyepiece, distant galaxies always appears white.
Spiral-shaped galaxies, so long as no new matter routinely falls into them, were long thought to . [+] remain static in size and extent over time. Through an eyepiece, a human being will see only the dominant, white color of the starlight averaged together.
NASA, ESA and W. Harris - McMaster University, Ontario, Canada
But with advanced cameras that pick up individual photons, some regions show a different color: pink.
This visible-light image composite of the Orion Nebula was created by the Hubble Space Telescope . [+] team back in 2004-2006. The colorations presented here are scientifically accurate.
NASA,ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team
In our own galaxy, it's the overwhelming color of star-forming regions like the Orion Nebula.
A young, star-forming region found within our own Milky Way. Note how the material around the stars . [+] gets ionized, and over time becomes transparent to all forms of light. Until that happens, however, the surrounding gas absorbs the radiation, emitting light of its own of a variety of wavelengths.
NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: R. O’Connell (University of Virginia) and the WFC3 Scientific Oversight Committee
In some galaxies, the pink color can dominate a telescope's entire field-of-view.
The starburst galaxy Henize 2-10, located 30 million light years away. When an entire galaxy forms . [+] stars, it undergoes a starburst, turning pink where the most active new star-formation occurs.
X-ray (NASA/CXC/Virginia/A.Reines et al) Radio (NRAO/AUI/NSF) Optical (NASA/STScI)
This isn't some optical illusion or a false-color image these regions and galaxies truly appear pink.
The star forming region 30 Doradus, in the Tarantula Nebula in one of the Milky Way's satellite . [+] galaxies, contains the largest, highest-mass stars known to humanity. The largest, R136a1, is approximately 260 times the Sun's mass the light from these hot, new, bright stars is predominantly blue, however.
NASA, ESA, and E. Sabbi (ESA/STScI) Acknowledgment: R. O’Connell (University of Virginia) and the Wide Field Camera 3 Science Oversight Committee
At first glance, it's surprising, since there are no pink stars, and the majority of young starlight is preferentially blue.
Two of the sky’s more famous residents share the stage with a lesser-known neighbour in this . [+] enormous three gigapixel image from ESO’s VLT Survey Telescope (VST). On the right lies the faint, glowing cloud of gas called Sharpless 2-54, the iconic Eagle Nebula (Messier 16) is in the centre, and the Omega Nebula (Messier 17) to the left. Note the pinkish color of all three these are all star-forming regions.
But once you realize that it isn't just stars, but gas, that can make light, the mystery solves itself.
Younger populations of stars contain short-lived objects that are hotter and bluer, and emit more . [+] ultraviolet, ionizing radiation. The net effect means that many hydrogen atoms surrounding these stars become ionized.
New star-forming regions produce lots of ultraviolet light, which ionizes atoms by kicking electrons off of their nuclei.
When free electrons recombine with hydrogen nuclei, the electrons cascade down the energy levels, . [+] emitting photons as they go. The n=3 to n=2 transition, known as Balmer alpha, is the strongest visible-light line, and is red in color.
Brighterorange & Enoch Lau/Wikimdia Commons
These electrons then find other nuclei, creating neutral atoms again, eventually cascading down through its energy levels.
Of all the possible energy-level transitions in the Hydrogen atom, only four lines are visible, with . [+] the brightest and strongest being the red line at 656.3 nanometers.
Hydrogen is the most common element in the Universe, and the strongest visible light-emitting transition is at 656.3 nanometers.
A portion of the galactic plane, with star forming regions highlighted in pink due to the emission . [+] of hydrogen atoms.
The combination of this red emission line — known as the Balmer alpha (or Hα) line — with white starlight adds up to pink.
The Whirlpool Galaxy (M51) appears pink along its spiral arms due to a large amount of star . [+] formation that's occurring. In this particular case, a nearby galaxy gravitationally interacting with the Whirlpool galaxy is triggering this star formation, but all spirals rich in gas exhibit some level of new star birth.
NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team STScI / AURA)
Red and white make pink, explaining the color of star-forming regions.
The dark swaths that permeate spiral galaxies are neutral clouds of gas and dust, and block visible . [+] and ultraviolet light. However, when gravitational collapse triggers the formation of new stars, these regions will light up in pinks and blues as they either ionize or reflect starlight, respectively.
New Milky Way map reveals a wave of stars in our galaxy’s outer reaches
(CNN) — A new map reveals the outskirts of the Milky Way galaxy, including a wave of stars disturbed by a small galaxy on a collision course with our own.
Data collected from the European Space Agency’s Gaia mission and NASA’s Near Earth Object Wide Field Infrared Survey Explorer has been used by astronomers to map the galactic halo and this group of stars. Their findings appear in a study published Wednesday in the journal Nature.
Our Milky Way is a galaxy with multiple spiral arms emanating from a central disk. The empty-looking halo lies outside of these swirling arms. But there may be more to the halo than meets the eye.
The halo, which hosts a small population of stars, is also thought to contain a lot of dark matter. This mysterious substance, which is invisible and has eluded scientists for decades, is thought to comprise most of the mass in the universe.
A small neighboring galaxy, known as the Large Magellanic Cloud, orbits the Milky Way. The data used to create the map revealed that, like a ship, the Large Magellanic Cloud has cut through the Milky Way’s outer halo. This disturbance has left a rippling wave of stars behind the Large Magellanic Cloud, which is in the halo.
A collision of galaxies
Currently, the Large Magellanic Cloud is 160,000 light-years from Earth, and it only has about a quarter of the mass of our giant galaxy.
Research from 2019 suggests it will catastrophically collide with our own galaxy in 2 billion years.
The impact has a chance of sending our solar system hurtling through space.
The wake created by the Large Magellanic Cloud is about 200,000 light-years to 325,000 light-years from the galactic center.
While previous research suggested its existence, this new data provides confirmation, as well as the most detailed and accurate map of the galaxy’s outskirts.
In the image, the strip in the middle represents a 360-degree view of our galaxy overlaying a map of the galactic halo. A bright wave in the bottom left of the image is the wake of stars, and to the right is the Large Magellanic Cloud and the path it is taking.
A large, light blue feature in the top right shows a high concentration of stars in our galaxy’s northern hemisphere.
Understanding dark matter
The ripple left by the dwarf galaxy’s movement is also an opportunity to study dark matter. Even though dark matter is invisible, it provides structure throughout the universe — including the foundation for galaxies.
So if the Large Magellanic Cloud can cut through the Milky Way’s halo and leave a wave of stars, the same ripple should essentially act as an outline of the dark matter.
Dark matter is essentially pulling on the Large Magellanic Cloud to slow it down, shrinking the dwarf galaxy’s orbit around the Milky Way and causing the eventual collision.
While it sounds violent, galactic collisions are what have created the massive galaxies populating our universe — and our own galaxy has previously experienced mergers before.
“This robbing of a smaller galaxy’s energy is not only why the (Large Magellanic Cloud) is merging with the Milky Way, but also why all galaxy mergers happen,” said Rohan Naidu, study co-author and a doctoral student in astronomy at Harvard University, in a statement. “The wake in our map is a really neat confirmation that our basic picture for how galaxies merge is on point!”
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Space Photos of the Week: A Tale of Two Galaxies
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Let’s switch the warp drive to light speed and head to deep space. The first stop is a satellite galaxy that orbits our Milky Way called the Large Magellanic Cloud, one of the most famous objects in the cosmos. Most galaxies have dwarf galaxies orbiting around them, just like moons orbit planets. Consisting of gas and newly forming stars, the LMC is only about 1/100th the size of our galaxy, but with 30 billion stars it’s certainly nothing to sneeze space dust at.
Next we’re traveling out 80 light years from Earth to a remarkable galaxy, called NGC 2655. It’s not a spiral like our Milky Way and it isn’t elliptical either NGC 2655 is what’s called a lenticular galaxy. These are disc-like bodies that have lost most of their stellar mass, but retain a lot of the gas originally present during formation. What results is an amorphous shape formed by stars and wisps of interstellar gas. Though irregular, NGC 2655 and other lenticulars are still quite spectacular.
How many galaxies are there?
It’s impossible to know for sure, but Hubble revealed that there are at least 100 billion galaxies in the universe. However, this may be a conservative estimation — other estimates put the total number of galaxies at 2 trillion.
These are all galaxies, so here goes: one, two, three…
Image credits: Hubble.
What is a galaxy
Before we start looking for galaxies and counting them, we need to know just what a galaxy is.
Essentially, a galaxy is a huge collection of gas, dust, and billions of stars all tied together by gravity. Although the distances between stars within the same galaxy can be huge, it’s important that they’re all connected into a single cluster by gravity — that’s what makes it a galaxy. Most galaxies have a supermassive black hole at their center, which helps keep it all together. As the name implies, supermassive black holes are immensely massive black holes — they have a mass on the order of millions or even billions of solar masses.
There are three types of galaxies: elliptical, spiral, and irregular. The name pretty much describes the overall shape of the galaxy: elliptical galaxies look like an “egg” of light (an ellipse), spiral galaxies extend arms around the central bulge, and irregular galaxies are pretty much everything that’s not spiral or elliptical. The Milky Way, our own galaxy, is a spiral galaxy. It seems strange that complex and diverse systems such as galaxies take on such few shapes. Researchers are still not exactly sure why this happens, but these common shapes are likely the product of rotation speed, time and gravity.
The Pinwheel Galaxy, NGC 5457. A classic spiral galaxy. Image credits: Hubble.
Galaxies can also vary greatly in size, which means that some are more easily visible than others. Dwarf galaxies have between 100 million and several billion stars (a very small number compared to the Milky Way’s 200-400 billion stars), measuring “only” 300 light-years. Meanwhile, “IC 1101” is the single largest galaxy that has ever been found in the observable universe, spanning a whopping 210,000 light-years across.
Looking for galaxies
So how does one look for galaxies? We can all see (on clear nights) the bright, milk-ish band that lends our galaxy its name. More than 2,000 years ago, the Greek philosopher Democritus (450–370 BCE) proposed that the band might consist of distant stars, a surprisingly insightful idea. Of course, there are many things that Democritus couldn’t have known, and it wasn’t until 1610 when the Italian astronomer Galileo Galilei used a telescope to study the Milky Way and discovered that it is composed of a huge number of faint and very distant stars.
Fast forwarding to modern times, telescopes have obviously gotten a lot better. But one of the biggest problems for all telescopes is the atmosphere, which contains a lot of light pollution and distortion of electromagnetic radiation. Thankfully, astronomers have by-passed that problem by building space telescopes — yes, we have telescopes in outer space. The most famous one, although not the first, is the Hubble telescope. Hubble is a vital research tool which has provided an invaluable trove of data. Among others, the landmark Hubble Deep Field, taken in the mid-1990s, gave the first real insight into the universe’s galaxy population.
The Antennae Galaxies, featured here, will eventually merge. Image credits: Hubble.
But even with Hubble, counting galaxies is extremely difficult for the simple fact that the universe is, well, very big. Looking in all directions and counting all the galaxies is nigh impossible, so instead, astronomers just focus on a sector of the night sky, count the galaxies there, and extrapolate based on that value. Of course, this can lead to some inaccuracies, but given the sheer size of the universe and the number of galaxies, the inaccuracies are unlikely to be significant.
How many galaxies are there
So, back to the question: how many galaxies are there? The first measurements from the 1990s found that there are 200 billion galaxies in the universe. However, that figure is unlikely to be reliable. Subsequent sensitive observations found that many faint galaxies were not observed the first time. The most recent, and likely the most accurate, survey found that the real number of galaxies is ten times larger: so, in total, there are 2 trillion galaxies in the universe, or 2,000 billion, if you prefer.
In late 2016, Christopher Conselice, Professor of Astrophysics at the University of Nottingham, along with several colleagues, carried out a sort of archaeological cosmology: they calculated the density of galaxies as well as the volume of one small region of space after another. This painstaking research was the culmination of 15 years of research, and it enabled the team to establish how many galaxies we have missed. The team found that, initially, astronomers missed a lot of galaxies because they were faint and very far away.
Each light speck is a galaxy, some of which are as old as 13.2 billion years. The universe is estimated to contain anywhere between 200 billion and 2 trillion galaxies. Image credits: Hubble.
“We are missing the vast majority of galaxies because they are very faint and far away. The number of galaxies in the universe is a fundamental question in astronomy, and it boggles the mind that over 90% of the galaxies in the cosmos have yet to be studied. Who knows what interesting properties we will find when we study these galaxies with the next generation of telescopes?”
Since many of the very distant galaxies are also faint, it seems that the total number of galaxies is currently decreasing over time. However, the more important takeaway lesson here is that we’re still only seeing a very small portion of the universe. Who knows what we might be missing out on. The study also says that the real number of galaxies might be even higher — up to 10 trillion galaxies.
“It boggles the mind that over 90% of the galaxies in the universe have yet to be studied,” commented Conselice. “Who knows what interesting properties we will find when we observe these galaxies with the next generation of telescopes?” he said in a statement.
Bonus: How many planets are there in the Universe?
If you’re still trying to wrap your mind around the number of galaxies, here’s another one. Estimating how many planets there are in the universe is much more a ballpark figure, and relies much more on deduction than direct observation. But for the fun of it, let’s do some simple math. Let’s say there are 2 trillion galaxies out there. The Milky Way is a fairly average galaxy, and it has over 200 billion planets. If we extrapolate based on that, we end up with 400 billion trillion planets in the universe. That’s 400,000,000,000,000,000,000,000 planets.
Again, this is definitely an approximation and not scientifically accurate, but it’s something to consider when you feel like you’re pretty important.
The Fastest Stars in the Universe May Approach Light Speed
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An artist's illustration of two black holes on the verge of merging. NASA
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Our sun orbits the Milky Way's center at an impressive 450,000 mph. Recently, scientists have discovered stars hurtling out of our galaxy at a couple million miles per hour. Could there be stars moving even faster somewhere out there?
After doing some calculations, Harvard University astrophysicists Avi Loeb and James Guillochon realized that yes, stars could go faster. Much faster. According to their analysis, which they describe in two papers recently posted online, stars can approach light speed. The results are theoretical, so no one will know definitively if this happens until astronomers detect such stellar speedsters—which, Loeb says, will be possible using next-generation telescopes.
But it's not just speed these astronomers are after. If these superfast stars are found, they could help astronomers understand the evolution of the universe. In particular, they give scientists another tool to measure how fast the cosmos is expanding. Moreover, Loeb says, if the conditions are right, planets could orbit the stars, tagging along for an intergalactic ride. And if those planets happen to have life, he speculates, such stars could be a way to carry life from one galaxy to another.
It all started in 2005 when a star was discovered speeding away from our galaxy fast enough to escape the gravitational grasp of the Milky Way. Over the next few years, astronomers would find several more of what became known as hypervelocity stars. Such stars were cast out by the supermassive black hole at the center of the Milky Way. When a pair of stars orbiting each other gets close to the central black hole, which weighs about four million times as much as the sun, the three objects engage in a brief gravitational dance that ejects one of the stars. The other remains in orbit around the black hole.
Loeb and Guillochon realized that if instead you had two supermassive black holes on the verge of colliding, with a star orbiting around one of the black holes, the gravitational interactions could catapult the star into intergalactic space at speeds reaching hundreds of times those of hypervelocity stars. Papers describing their analysis have been submitted to the Astrophysical Journal and the journal *Physical Review Letters. *
The galaxy known as Markarian 739 is actually two galaxies in the midst of merging. The two bright spots at the center are the cores of the two original galaxies, each of which harbors a supermassive black hole.
This appears to be the most likely scenario that would produce the fastest stars in the universe, Loeb says. After all, supermassive black holes collide more often than you might think. Nearly all galaxies have supermassive black holes at their centers, and nearly all galaxies were the product of two smaller galaxies merging. When galaxies combine, so do their central black holes.
Loeb and Guillochon calculated that merging supermassive black holes would eject stars at a wide range of speeds. Only some would reach near light speed, but many of the rest would still be plenty fast. For example, Loeb says, the observable universe could have more than a trillion stars moving at a tenth of light speed, about 67 million miles per hour.
Because a single, isolated star streaking through intergalactic space would be so faint, only powerful future telescopes like the James Webb Space Telescope, planned for launch in 2018, would be able to detect them. Even then, telescopes would likely only see the stars that have reached our galactic neighborhood. Many of the ejected stars probably would have formed near the centers of their galaxies, and would have been thrown out soon after their birth. That means that they would have been traveling for the vast majority of their lifetimes. The star's age could therefore approximate how long the star has been traveling. Combining travel time with its measured speed, astronomers can determine the distance between the star's home galaxy and our galactic neighborhood.
If astronomers can find stars that were kicked out of the same galaxy at different times, they can use them to measure the distance to that galaxy at different points in the past. By seeing how the distance has changed over time, astronomers can measure how fast the universe is expanding.
These superfast rogue stars could have another use as well. When supermassive black holes smash into each other, they generate ripples in space and time called gravitational waves, which reveal the intimate details of how the black holes coalesced. A space telescope called eLISA, scheduled to launch in 2028, is designed to detect gravitational waves. Because the superfast stars are produced when black holes are just about to merge, they would act as a sort of bat signal pointing eLISA to possible gravitational wave sources.
The existence of these stars would be one of the clearest signals that two supermassive black holes are on the verge of merging, says astrophysicist Enrico Ramirez-Ruiz of the University of California, Santa Cruz. Although they may be hard to detect, he adds, they will provide a completely novel tool for learning about the universe.
In about 4 billion years, our own Milky Way Galaxy will crash into the Andromeda Galaxy. The two supermassive black holes at their centers will merge, and stars could be thrown out. Our own sun is a bit too far from the galaxy's center to get tossed, but one of the ejected stars might harbor a habitable planet. And if humans are still around, Loeb muses, they could potentially hitch a ride on that planet and travel to another galaxy. Who needs warp drive anyway?
Research Box Title
In celebration of the 31st anniversary of the launching of NASA's Hubble Space Telescope, astronomers aimed the renowned observatory at a brilliant "celebrity star," one of the brightest stars seen in our galaxy, surrounded by a glowing halo of gas and dust.
The price for the monster star's opulence is "living on the edge." The star, called AG Carinae, is waging a tug-of-war between gravity and radiation to avoid self-destruction.
The expanding shell of gas and dust that surrounds the star is about five light-years wide, which equals the distance from here to the nearest star beyond the Sun, Proxima Centauri.
The huge structure was created from one or more giant eruptions about 10,000 years ago. The star's outer layers were blown into space—like a boiling teapot popping off its lid. The expelled material amounts to roughly 10 times our Sun's mass.
These outbursts are the typical life of a rare breed of star called a luminous blue variable, a brief convulsive phase in the short life of an ultra-bright, glamorous star that lives fast and dies young. These stars are among the most massive and brightest stars known. They live for only a few million years, compared to the roughly 10-billion-year lifetime of our Sun. AG Carinae is a few million years old and resides 20,000 light-years away inside our Milky Way galaxy.
Luminous blue variables exhibit a dual personality: They appear to spend years in quiescent bliss and then they erupt in a petulant outburst. These behemoths are stars in the extreme, far different from normal stars like our Sun. In fact, AG Carinae is estimated to be up to 70 times more massive than our Sun and shines with the blinding brilliance of 1 million suns.
"I like studying these kinds of stars because I am fascinated by their instability. They are doing something weird," said Kerstin Weis, a luminous blue variable expert at Ruhr University in Bochum, Germany.
Major outbursts such as the one that produced the nebula occur once or twice during a luminous blue variable's lifetime. A luminous blue variable star only casts off material when it is in danger of self-destruction as a supernova. Because of their massive forms and super-hot temperatures, luminous blue variable stars like AG Carinae are in a constant battle to maintain stability.
It's an arm wrestling contest between radiation pressure from within the star pushing outward and gravity pressing inward. This cosmic match results in the star expanding and contracting. The outward pressure occasionally wins the battle, and the star expands to such an immense size that it blows off its outer layers, like a volcano erupting. But this outburst only happens when the star is on the verge of coming apart. After the star ejects the material, it contracts to its normal size, settles back down, and becomes quiescent for a while.
Like many other luminous blue variables, AG Carinae remains unstable. It has experienced lesser outbursts that have not been as powerful as the one that created the present nebula.
Although AG Carinae is quiescent now, as a super-hot star it continues pouring out searing radiation and powerful stellar wind (streams of charged particles). This outflow continues shaping the ancient nebula, sculpting intricate structures as outflowing gas slams into the slower-moving outer nebula. The wind is traveling at up to 670,000 miles per hour (1 million km/hr), about 10 times faster than the expanding nebula. Over time, the hot wind catches up with the cooler expelled material, plows into it, and pushes it farther away from the star. This "snowplow" effect has cleared a cavity around the star.
The red material is glowing hydrogen gas laced with nitrogen gas. The diffuse red material at upper left pinpoints where the wind has broken through a tenuous region of material and swept it into space.
The most prominent features, highlighted in blue, are filamentary structures shaped like tadpoles and lopsided bubbles. These structures are dust clumps illuminated by the star's reflected light. The tadpole-shaped features, most prominent at left and bottom, are denser dust clumps that have been sculpted by the stellar wind. Hubble's sharp vision reveals these delicate-looking structures in great detail.
The image was taken in visible and ultraviolet light. Ultraviolet light offers a slightly clearer view of the filamentary dust structures that extend all the way down toward the star. Hubble is ideally suited for ultraviolet-light observations because this wavelength range can only be viewed from space.
Massive stars, like AG Carinae, are important to astronomers because of their far-reaching effects on their environment. The largest program in Hubble's history—the Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES)—is studying the ultraviolet light of young stars and the way they shape their surroundings.
Luminous blue variable stars are rare: less than 50 are known among the galaxies in our local group of neighboring galaxies. These stars spend tens of thousands of years in this phase, a blink of an eye in cosmic time. Many are expected to end their lives in titanic supernova blasts, which enrich the universe with heavier elements beyond iron.
- Launched on April 24, 1990, NASA's Hubble Space Telescope has made more than 1.5 million observations of about 48,000 celestial objects.
- In its 31-year lifetime, the telescope has racked up more than 181,000 orbits around our planet, totaling over 4.5 billion miles.
- Hubble observations have produced more than 169 terabytes of data, which are available for present and future generations of researchers.
- Astronomers using Hubble data have published more than 18,000 scientific papers, with more than 900 of those papers published in 2020.
The Hubble Space Telescope 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. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.
Space Telescope Science Institute, Baltimore, Maryland
Space Telescope Science Institute, Baltimore, Maryland
Research Box Title
Supermassive black holes, which likely reside at the centers of virtually all galaxies, are unimaginably dense, compact regions of space from which nothing — not even light — can escape. As such a black hole, weighing in at millions or billions of times the mass of the Sun, devours material, it is surrounded by a swirling disk of gas. When gas from this disk falls towards the black hole, it releases a tremendous amount of energy. This energy creates a brilliant and powerful galactic core called a quasar, whose light can greatly outshine its host galaxy.
Astronomers widely believe that the energy from quasars is responsible for limiting the growth of massive galaxies. Shortly after the launch of NASA's James Webb Space Telescope, scientists plan to study the effect of three carefully selected quasars on their host galaxies in a program called Q3D.
A supermassive black hole is very small compared to its host galaxy — it's the equivalent of a penny in relation to the size of the entire Moon. Still, supermassive black holes have an immense influence on the galaxies they inhabit.
"Physically very small objects, supermassive black holes seem to have an enormous impact on the evolution of galaxies and eventually on the way our universe looks today," said Q3D principal investigator Dominika Wylezalek, a Research Group Leader at the University of Heidelberg in Germany.
Two decades ago, scientists hypothesized the critical role of quasars in limiting galaxy growth, but specific observational evidence has been surprisingly hard to come by. Scientists think a quasar's torrential winds push out the equivalent of hundreds of solar masses of material each year. As the quasar winds sweep across the galaxy's disk, material that otherwise would have formed new stars is violently carried away from the galaxy, causing star birth to cease. But observing the power and reach of quasars on their host galaxies remains a major unresolved issue in modern astrophysics. The Webb telescope could change that.
Analyzing Data in 3D
In addition to its exquisite sensitivity, resolution and infrared vision, Webb's capabilities include unique three-dimensional imaging spectroscopy. This special observing technique allows the team to get detailed measurements of light for every single pixel across the field of view. It stitches together many images at slightly different wavelengths. This allows scientists to spatially map gas motions inside the galaxy. The technique will revolutionize the understanding of the relationship between supermassive black holes and their host galaxies by allowing scientists to probe the stars, gas and dust in nearby and distant galaxies.
"Imaging spectroscopy is important for us because the winds in these distant quasars are not necessarily symmetric," explained co-principal investigator Sylvain Veilleux, a professor of astronomy at the University of Maryland, College Park. "So, one needs a spectrum at every position to determine what is their geometry and be able to draw the important information from these winds and the impact they have on their host galaxies."
Studying Three Quasars and Their Hosts
The Q3D team will study three bright quasars to measure the activity that comes from accreting material onto supermassive black holes, and how the host galaxies are affected by that activity. The team chose the three quasars for scientific reasons, but also to test and assess the capabilities of Webb. The objects intentionally span a very broad range of distance from Earth, from relatively nearby to very far away. They are also among the most luminous quasars at their respective distances and are known to have outflows of material.
Powerful quasar outflows appear to prevent a galaxy's gas from forming new stars and growing the galaxy. Scientists think this quasar–galaxy connection is crucial in determining how galaxies evolve from the early universe to today. It’s especially important for galaxies a few times larger than the Milky Way, because quasar hosts are generally more massive galaxies.
Seeing Beyond the Bright Light
Quasars are very bright compared with the material around them, so the team is developing special software tools that allow them to study the phenomena. When quasars were discovered in the 1950s, they were brilliant radio sources that looked like stars on photographic plates, so they were called "quasi-stellar radio sources." Eventually, astronomers learned that quasars were actually inside of galaxies, but they were so bright that they outshone their host galaxies.
"We're interested in the quasar itself — the bright, star-like thing in the middle — but we’re also interested in the fainter host galaxy. And not just the host galaxy, but the even fainter outflow from the host. This is the gas that's not circling around the quasar, or the center of the galaxy, but is instead flowing out. To see this really faint stuff behind the quasar, we have to remove the quasar's light. That’s one unique thing the software will do," said co-investigator David Rupke, associate professor of physics at Rhodes College in Memphis, Tennessee. Rupke is leading the effort to write the software to analyze the Q3D data.
Paving the Way for Future Webb Studies
The Q3D study is part of the Director's Discretionary–Early Release Science program, which provides public data to the entire scientific community early in the telescope's mission. This program allows the astronomical community to quickly learn how best to use Webb’s capabilities, while also yielding robust science.
"From a technical standpoint, with our observations, we are testing different modes, filters and combinations," explained Wylezalek. "It will be very useful for the scientific community to see the performance in these different modes. Scientifically, we are probing quasars at different luminosities and cosmic times to inform the community about Webb’s performance when assessing different scientific questions."
The Q3D software will not only be useful for users observing quasars but for anyone observing bright, point-like, central sources on top of fainter sources. Such observations could include super star clusters, supernovas, tidal disruption events or gamma-ray bursts.
The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
Beyond the Stars
Each star has its own unique beauty and a heavenly place in which we can observe and appreciate them. When you observe the night sky without any light interference, you can see thousands upon thousands of these mysterious, tiny, flickering luminaries lighting up the heavens. My wife and I can give testimony to this as we witnessed it at the bottom of Grand Canyon on a clear night as we were camping in the open air. There it was, an unexpected and amazing presentation.
As we looked upon this dark night, we witnessed the most majestic display of heavenly objects covering every inch of the night skies. It was a remarkable experience that we will never forget. We had an experience like King David shared when he wrote, “The heavens declare the glory of God, And the firmament shows his handiwork.” (Psalm 19:1)
What a perfect way God declares His glory when we as humans observe the vast expanse of stars in the sky. The only way to even come close to determining the total number of stars is to estimate because it is so difficult to observe all of these bodies so numerous in space. They are counted by how they group together in galaxies and star clusters. The Milky Way Galaxy is composed of approximately 200 billion stars. If one could count three stars per second, it would take 84,000 years to count the number of stars in our galaxy. The estimated number of galaxies in the universe has reached 200 billion. Mario Livio, an astrophysicist from the Space Telescope Science Institute in Baltimore, Maryland agrees with this estimate. The eXtreme Deep Field images made after ten years of photographs from the Hubble Space Telescope have been analyzed and produced this conclusion. The number of stars estimated in the universe has been increasing as more detailed information becomes available.
The article entitled How Many Galaxies Are There? written by Elizabeth Howell on March 20, 2018, stated that Livio believes the number is more than likely to increase to 200 billion galaxies. It would certainly increase the number of stars to over septillion stars in the universe. This number is equivalent to 1 followed by twenty-four zeros.
With increasing technological advances and more time with powerful optical instrumentation like the Hubble Space Telescope, the number of known stars and galaxies has increased. There are a significant number of astronomers who theorize that 200 billion galaxies is too conservative and they believe the estimate needs to be increased to 2 trillion galaxies. Of course, we will continue to count, and the number will continue to be too large for us to imagine as humans.
How did the stars originate?
Who created all these gas giants emitting their lights as tiny specks on earth? Who put them all in place so that we can witness this colossal wonder? We are constantly being brainwashed to believe that the only force that brought this magnificent creative cosmos together with all its order was the Big Bang. The theory of how the stars were proposed by evolutionary cosmologists is based on mere speculation. It supposedly only happened once and, therefore, is absent of any direct observation. There are huge scientific challenges with the idea that gases coalesce to make a functioning star that gives off energy in the form of heat and light, caused by fusing hydrogen atoms to helium faces. In reality, this theory is a nuclear reaction that needs energy equivalent to an atomic bomb to get it started. There are so many conditions for star formation that are overlooked by those held hostages to evolutionary dogma.
What we actually observe is the highest intellectual order that man can witness. Stars burn fuel most efficiently, which is evidenced by the fact that they can last for a long period of time. They come together in galaxies and clusters because of the laws of gravity. And how can we forget our sun that is the primary energy source for all life on earth? It has a massive amount of Hydrogen 600 million tons of hydrogen fuses to helium every second. How did this system come together by a haphazard accident? Was it instead of a divine super-intellectual plan? Others see through this devastating materialistic lie and acknowledge that there is one greater than himself. It provokes humility and brings one to their knees full of worship to God, who bestows all beauty, grandeur, order, power, and love to share His glory with all. It is what brings us closer to the One who not only made the universe but also formed out of the dust of the earth, man in His image. The prophet Isaiah said it well,
“Lift up your eyes and look to the heavens: Who created all these? He who brings out the starry host one by one and calls them each by name. Because of his great power and mighty strength, not one of them is missing.” Isaiah 40:26
The number of stars created on the fourth day of creation demonstrates how magnificently big and powerful our Creator is and as Isaiah reminds us, God is in control because “not one of them is missing.” The infinitesimal number of stars shows not only His wonderful power but also His amazing grace. These stars shine their own light in the total darkness, reminding us that there is an infinite amount of mercy that our Savior sheds for everyone on earth for all time.
How Big are the Stars?
But let us not forget how big these starry objects are, moving at speeds exemplified by our sun, a medium-sized star, approaching a half-million miles per hour. It is an average distance of 93 million miles away. The star Betelgeuse, a giant red star, is 700 times bigger than the sun and 14,000 times brighter. This giant star dwarfs the sun to a mere dot in comparison. The earth disappears and becomes a pixel, and humans become microscopic next to these giant objects created by our Creator and Savior.
It causes us to meditate upon the question: who are we to defy the Creator? Who are we to question His plan? When the prophet, Job, was brought to his knees he said,
“I know that You can do everything And that no purpose of Yours can be withheld from You. You asked, ‘Who is this who hides counsel without knowledge?’ Therefore I have uttered what I did not understand, things too wonderful for me, which I did not know.” Job 42:2-3
How Vast is the Universe?
As we meditate on the number of stars, what about the space they occupy? Our neighbor, the closest star to the sun, is Alpha Centauri, which is 4.3 light-years away (about 25.2 trillion miles). As humans, we are limited to think in thousands of miles, not trillions. For us to take a trip around the earth, it would total about 25,000 miles the International Space Station is orbiting at an average of only 250 miles above the earth, and Mount Everest, one of the highest mountains on earth measures only 2.5 miles. Our sun, which the earth revolves around every year is an average 93 million miles away. The fastest jet clocked speeds at over 2,000 miles per hour, and for it to travel to the sun, it would take 5.3 years. As we move from our solar system to our Milky Way Galaxy, it is estimated that our widest part of our Milky Way Galaxy measures 100,000 light-years or 580,000 trillion miles. Of course, we have to use estimates to determine the observable diameter of the universe. If the stars were equally spaced apart, this number would be 116 million septillions, but the stars along the Milky Way Galaxy seem to bunch up, moving closer together, so it becomes harder to estimate.
Another challenging factor is that stars can warp space and time when they cluster together as in a galaxy. According to Einstein’s Laws of General Relativity, massive bodies like stars can distort space by creating holes in space. Time is also affected because as you approach the center, time slows down. And when you move away, time speeds up. Distorting both space and time is difficult to imagine, but the math works with what we observe. For example, our GPS systems have to be adjusted for Einstein's relativity because there is a correction factor as great as two minutes in navigation. The satellite clocks are electronically corrected to prevent this error. Of course, this complicates matters when attempting to measure the radius of the universe. The figure used in popular literature is 93 billion light-years (one light-year = 5.9 trillion miles), which is a conservative estimate.
The cosmos is a dynamic place with objects moving at astonishing speeds. Our sun, a star in the milky way galaxy, is moving at a speed of 450,000 miles per hour, and the Milky Way galaxy is speeding through space at 2.1 million miles per hour in a galactic cluster. The cosmos is also expanding and spreading out at incredible rates much faster than the objects moving within. The Bible addresses this phenomenon, stating that the heavens are spreading out, as shown in the following example:
“The burden of the word of the Lord against Israel. Thus says the Lord, who stretches out the heavens, lays the foundation of the earth and forms the spirit of man within him:” Zechariah 12:1
“He has made the earth by His power, He has established the world by His wisdom, And has stretched out the heavens at His discretion.” Jeremiah 10:12
When we consider the size of the universe, there is another factor that has to be determined from an evolutionist worldview, which centers on the idea that everything came from the Big Bang. Big Bang theory is described as a point in which everything began from a very dense and very high-energy super force. It is described as a singularity that happened when there were no fundamental particles like atoms, planets, stars, etc. Evolutionists have concluded that about 95% of the universe is missing in the forms identified as dark matter and dark energy. We can only see less than 5% of the universe in the forms of stars, planets, asteroids, comets, and all other visible matter. The universe is expanding at a high rate of speed, and this provokes the question: where does the energy to produce this expansion originate? It is missing and defined as dark energy, calculated at 68% of the universe. Galaxies are extremely large, numbering thousands to billions of stars. The gravitational forces needed to attract all these stars and large masses together in galaxies are absent. This missing matter is dark matter estimated at 27%. There are many theories proposed about antimatter and invisible particles, but as NASA scientists and other scientists attempt to solve this problem, it remains a mystery.
For those who believe in a supernatural Creator, we know that He shares His glory with us by revealing Himself for us to discover. He is the first cause--not the Big Bang--for our existence and hope. We also believe He made clear with His Word in Genesis 1 how the universe came to be as He spoke everything into existence. It states in Genesis 1:14, “Then God made two great lights: the greater light to rule the day, and the lesser
light to rule the night. He made the stars also.”
With all the factors mentioned above, it becomes a real challenge to determine the size of the universe. There is one conclusion that both Creationists and Evolutionists would agree upon: the dynamic universe with all its heavenly bodies is too large to measure because it is expanding continuously. The testimony of the vastness of the universe filled with twinkling lights of various stars with colors all across the spectrum gives us an awareness that our Creator is unique, huge, and in command. The Psalmist proclaimed,
“Bless the Lord, O my soul! O Lord my God, You are very great: You are clothed with honor and majesty, who cover yourself with light as with a garment, who stretch out the heavens like a curtain.” Psalm 104:1-2
As we are reminded in Isaiah 40:22, there is so much to discuss about the universe and the stars if God took the care to number, name, and account that no star is missing. God expresses His glory and power in the heavenly places so much that we are forced to continue this discussion in our next CSI Director’s Letter. He, in so many ways, has revealed Himself so that we can see His awesomeness in design. He also gave the genius of Galileo, Newton, Einstein, and so many others, which gives us a contagious inspiration to probe the universe, making discoveries that challenge man to think higher. God desires to make us look up and see through all He created and realize how much He loves us.
Your partnership matters
We are offering two wonderful resources that will help you and your loved ones appreciate how God has blessed us through the study of astronomy. A dynamic DVD titled “Beyond the Stars: Seeing Cosmic Design” presented by Branyon May, an astrophysicist, addresses many different topics engagingly and interactively through 13 short lessons told from a Creationist perspective. Every Christian should be aware of this information as the world has infiltrated astronomy with an atheistic viewpoint. Also, we will offer an Astronomy Pocket Guide that features four experts, including Jason Lisle and Danny Faulkner, who give us answers to questions about starlight and time, ETs and UFOs, and many other popular astronomy questions. We are called to give an answer for the hope we have, as stated in 1 Peter 3:15. These excellent resources will assist you in your Christian walk.
We will offer both of these resources for a donation of $35.00. Your partnership is important for us to move forward to impact lives for Christ. We submit ourselves to God’s plan and know that you are part of it. We thank God for you and all those that have supported us over the years. We know that God is going to work through us as we make ourselves available to serve Him.
I appreciate your prayers and financial support as God has placed on our hearts to expand our ministry in our new location.
Rogue stars outside galaxies may be everywhere
You’ve heard of rogue planets , floating through the universe untethered to any solar system. Now meet rogue stars, which drift through space with no galaxy to call home. A new study has come to the startling conclusion that as many as half of all stars in the universe may be rogue, having been ejected from their birthplaces by galaxy collisions or mergers.
Astronomers James Bock of the California Institute of Technology in Pasadena and Asantha Cooray of the University of California, Irvine, didn’t set off to discover a huge population of rogue stars. They wanted to study early galaxies by looking at extragalactic background light, or the EBL. The EBL is essentially all the accumulated light from stars over the history of the universe and ranges in wavelength from the ultraviolet, through the optical, and to the infrared. To get a good look at it, Bock, Cooray, and an international team of colleagues built a detector, called the Cosmic Infrared Background ExpeRiment (CIBER), that could be launched to the edge of space on a rocket and collect images with two 11-centimeter telescopes.
The EBL has long been mysterious to scientists. Observing it from Earth is hard because so many other, local sources of light must be stripped away before it is possible to see the light from further back in the universe’s history. And when astronomers have managed to get a look at the EBL, usually using orbiting infrared telescopes such as Hubble and Spitzer, the ups and downs—or fluctuations—of its light do not appear to coincide with known light sources. About 10 years ago, a team from Goddard Space Flight Center in Greenbelt, Maryland, used the Spitzer telescope to study the EBL and concluded that the fluctuations of light must be produced by primordial galaxies and black holes in the very early history of the universe, says team member Samuel Moseley.
CIBER began to look at the EBL during several flights since 2010, followed by a couple of years of intricate image processing to strip out unwanted foreground light. The fluctuations that the team came up with are “inconsistent” with early galaxies and black holes and are much more reminiscent of scattered stars between galaxies, they report online today in Science. The EBL they detected is also much stronger toward the blue end of the wavelengths CIBER can detect, a skew that also suggests a younger source of light. “The fluctuations are there, they’re really bright and they look very blue,” Bock says. “We think it’s stars.” The researchers also looked at the total brightness of the EBL and found that it was in the same ballpark as that from all the known sources—stars and galaxies—at that wavelength. That suggests that there may be as many stars outside galaxies as there are inside.
Moseley is not entirely convinced by the CIBER team’s conclusions. His team has identified some objects in x-ray observations by the orbiting Chandra telescope that seem to line up with EBL fluctuations that the NASA team detected. Those x-ray sources are much more likely to be galaxies or black holes than isolated stars, supporting his team’s early galaxy hypothesis. “We’ll have to confirm, but they are hard to accommodate with the star model,” he says. Also, he points out, if there is a huge population of stars outside galaxies, we should see a noticeable number of supernovas occurring out in the middle of nowhere as those rogues stars die. “There are ways to test in the near term. It’ll be an enthusiastically pursued question,” Moseley says.
Daniel is Science’s senior correspondent in the United Kingdom, covering astronomy, physics, and energy stories as well as European policy.