SPACE
BEAUTY,EHAstronomers pierce cosmic dust of 'Jewel Bug Nebula' to study anatomy of a dying star
Keith Cooper
Mon, November 13, 2023
A galaxy resembling a flower blossoms in shades of pink, purple and blue.
Astronomers with the Gemini North Telescope on Mauna Kea in Hawaii have released the first spectrum from a brand new spectrograph capable of peering deep into the veils of cosmic dust that line our universe.
The spectrum shows details of an expanding cloud of gas and dust that a sun-like star ejected at the end of its life. This cloud is known as a planetary nebula — perhaps a misleading name as it doesn't have anything to do with planets. More specifically, this nebula is formally called NGC 7027, or the Jewel Bug Nebula, and sits about 3,000 light years away from us in the constellation of Cygnus, the Swan.
The new spectrograph that managed to observe the light of the Jewel Bug Nebula is named IGRINS-2, which is short for Immersion Grating Infrared Spectrograph-2. It’s a high-resolution instrument that operates at near-infrared wavelengths of light — wavelengths unseeable by human eyes — specifically between 1.45 and 2.45 microns. Cosmic dust is opaque at visible wavelengths, which our eyes can see, but near-infrared light can penetrate through that dust and detect what secrets lie beneath. That’s why the James Webb Space Telescope is also said to have the ability of peering behind deep space dust curtains. It's the most powerful near-infrared wavelength detector we have.
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As for the "immersion grating" bit, this is a kind of diffraction grating that uses transparent and reflective mediums to split light into its component wavelengths. That's what IGRINS-2 did with the infrared wavelengths to achieve the vibrant, detailed spectrum we see.
Spectra of the Jewel Bug Nebula captured at 1.49 microns (blue) and 1.93 microns (red). The colors are false color, with the spectra in infrared light and not visible light.
IGRINS-2 is an updated version of the original IGRINS spectrograph, built in 2014 by scientists at the Korea Astronomy and Space Science Institute (KASI) as well as the University of Texas.
IGRINS 1.0 has already been around the block, with periods of being installed as a "visiting instrument" on a number of telescopes including the 2.7-meter (8.9 feet) Harlan J. Smith Telescope at McDonald Observatory in Texas, and the 4.3-meter (14.1 feet) Discovery Channel Telescope at Lowell Observatory in Arizona. And since 2020, IGRINS has been installed on the 8.1-meter (26.6 feet) Gemini South Telescope in Chile.
Now, the other half of NOIRLab’s International Gemini Observatory, namely Gemini North, is receiving IGRINS-2 — and on a permanent basis.
a group of people wearing hard hats pose beneath a portion of a large blue industrial machinery.
Built once more by scientists and technicians at KASI, the first-light spectrum of the Jewel Bug Nebula is only the beginning. Following a period of integrating the instrument into Gemini North’s sub-systems and getting it to work with the telescope’s software, IGRINS-2 will primarily target regions of star-birth, as well as star-death in the case of NGC 7027, exoplanets, cool brown dwarfs that radiate mostly in the infrared, and distant galaxies swathed in dust during some of the more tumultuous stages of their evolutions.
an orange laser shoots from the far side of a round observatory structure, pointed northward as stars swirl around its focal point at the north star, streaked from a prolonged camera exposure
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"The ability of IGRINS-2 to peer within otherwise opaque regions of the universe will allow us to better understand how stars are born and many other astronomical phenomena hidden behind galactic dust," Martin Still, the National Science Foundation's Program Director for the International Gemini Observatory, said in a statement.
IGRINS-2 identified elements such as isotopes of bromine, helium, iron, krypton and selenium in NGC 7027, plus copious amounts of molecular hydrogen. With the powerful light-gathering capability of Gemini North’s 8.1-meter mirror at its disposal, we can expect IGRINS-2 to make even more detailed observations and many major discoveries in the future.
Supermassive black hole at the heart of the Milky Way is approaching the cosmic speed limit, dragging space-time along with it
Robert Lea
Mon, November 13, 2023
An image of the supermassive black hole at the heart of the Milky Way, which scientists think is spinning as fast as it can.
The supermassive black hole at the heart of our galaxy isn't just spinning — it's doing so at almost maximum speed, dragging anything near it along for the ride.
Physicists calculated the rotational speed of the Milky Way's supermassive black hole, called Sagittarius A* (Sgr A*), by using NASA's Chandra X-ray Observatory to view the X-rays and radio waves emanating from outflows of material.
The spin speed of a black hole is defined as "a" and given a value from 0 to 1, with 1 being the maximum rotational speed to a particular black hole, which is a significant fraction of the speed of light. Ruth A. Daly, a physicist at Penn State, and colleagues found that the rotational speed of Sgr A* is between 0.84 and 0.96 — close to the top limit defined by a black hole's width. The team described Sgr A*'s blistering speed in a study published Oct. 21 in the journal Monthly Notices of the Royal Astronomical Society.
"Discovering that Sgr A* is rotating at its maximum speed has far-reaching implications for our understanding of black hole formation and the astrophysical processes associated with these fascinating cosmic objects," Xavier Calmet, a theoretical physicist at the University of Sussex who was not involved in the research, told Live Science in an email.
Black holes are such a drag
A black hole's spin is different from those of other cosmic objects. Whereas planets, stars and asteroids are solid bodies with physical surfaces, black holes are actually regions of space-time bounded by an outer nonphysical surface called the event horizon, beyond which no light can escape.
"While the rotation of a planet or star is governed by the distribution of its mass, the rotation of a black hole is described by its angular momentum," Calmet said. "Due to the extreme gravitational forces near a black hole, the rotation causes spacetime to become highly curved and twisted, forming what is known as the ergosphere. This effect is unique to black holes and does not occur with solid bodies like planets or stars."
That means that when they spin, black holes literally twist up the very fabric of space-time and drag anything within the ergosphere along.
This phenomenon, called "frame dragging" or the "Lensing-Thirring effect," means that to understand the way space around a black hole behaves, researchers need to know its spin. This frame dragging also gives rise to weird visual effects around black holes.
"As light travels close to a rotating black hole, the rotation of spacetime causes the light's path to be curved or twisted," Calmet said. "This results in a phenomenon called gravitational lensing, where the light's trajectory is bent due to the gravitational influence of the rotating black hole. The frame-dragging effect can lead to the formation of light rings and even the creation of the black hole's shadow. These are manifestations of the gravitational influence of black holes on light."
The theoretical top speed of a black hole is determined by how it feeds on matter and thus how it grows.
"As matter falls into a black hole, it increases the black hole's spin, but there's a limit to how much angular momentum it can possess," Calmet said. "Another factor is the mass of the black hole. More massive black holes have a higher gravitational pull, making it more challenging to increase their spin.
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"Additionally, the interaction between the black hole and its surroundings, such as accretion disks, can transfer angular momentum and affect the black hole's spin," he added.
This could explain why Sgr A*, with its mass equivalent to around 4.5 million suns, has a spin speed between 0.84 and 0.96 but the rapidly feeding supermassive black hole at the heart of galaxy M87 — the first black hole ever to be photographed — is spinning at between 0.89 and 0.91, despite having the mass of 6.5 billion suns.
Is the vacuum of space truly empty?
Paul Sutter
Mon, November 13, 2023
Artist's illustration black hole void .
Imagine going out to the deepest, emptiest place in the universe, achieving a perfect, total vacuum. Would you be surrounded by emptiness? The answer to that question is much subtler than you might realize.
The modern journey into the vacuum began in the 17th century, with a flashy experiment designed by Otto von Guericke, mayor of the town of Magdeburg in the Holy Roman Empire. As part of a political stunt to show that his city had rebounded after the ravages of the 30 Years' War, von Guericke put on a demonstration for the emperor and other notables to show off his newly invented vacuum pump. By placing two hemispheres together and pumping out all of the air, Otto showed that not even a team of horses could pull the hemispheres apart.
Contrary to millennia of thought in Europe following Aristotle's argument that "nature abhors a vacuum," von Guericke showed that the vacuum was possible.
In the decades following von Guericke's demonstration, philosophers and scientists wondered if the vast reaches of space were filled with some sort of material known as the ether, which would serve two purposes: One, it would still prevent a true vacuum from forming, and two, it would function as a medium for light waves to propagate through.
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However, in the late 1800s, two physicists in Cleveland, Albert Michelson and Edward Morley, devised a clever experiment to measure changes in the speed of light as Earth moved through the ether. No changes were detected — and soon, Einstein would demonstrate that the speed of light was always constant — so scientists eventually moved away from the concept of the ether, allowing for the possibility of a true vacuum.
Still, even far from Earth, there's plenty of stuff floating around: charged particles zipping here and there, wandering hydrogen atoms, bits of fluff and dust minding their own business. Even though the density of interstellar space is billions of times lower than even our emptiest human-made vacuum chambers, it's not 100% percent empty.
To reach the emptiest places in the universe, you have to travel to the cosmic voids, the vast regions of nothingness that dominate the volume of the cosmos. In the depths of the largest voids, you can stand hundreds of millions of light-years from the nearest galaxy. The cores of the voids are so empty that not even dark matter — the mysterious, invisible form of matter that makes up the bulk of every galaxy — doesn't even have a presence.
But still, space wouldn't really be empty. Suffusing the entire cosmos are lightweight, neutral particles called neutrinos as well as the radiation left over from the early days of the universe. This radiation, known as the cosmic microwave background (CMB), is responsible for over 99.99% of all the radiation in the universe, and it's impossible to escape. So, even in the darkest voids, you're not entirely lonely.
So let's say you were to build a giant box thick enough to block out the neutrinos and the CMB, leaving you alone inside. (Technically, the walls of the box would emit photons of their own, but let's leave that aside for this thought experiment.) Would you be alone then?
Quantum physics provides a surprising answer: No. Physicists have discovered that quantum fields soak all of space and time, and these quantum fields give rise to the particles of everyday life. But when left to their lonesome, the quantum fields have an intrinsic energy, known as vacuum energy. This energy is omnipresent throughout the universe. Even though you wouldn't have any particles around you, you'd still have this energy to be your sole companion.
So what if you concocted a device to nullify the vacuum energy (which is technically impossible, but let's keep going with the thought experiment)? Would you finally, truly be alone in the universe, surrounded by the perfect ideal of an all-encompassing nothingness?
The answer to that is … it depends. You'd still be an object in space, and some view space itself to have existence. We like to think of space as just a mathematical abstraction, a way for us to measure location and extent. But the concept of space began to take on a more concrete character with the work of René Descartes, the 17th-century genius who invented a mathematical foundation to describe space. If you've ever written down the x- and y-axes of a Cartesian grid, you have Descartes to thank for it.
Isaac Newton elevated the concept of space to serve as an absolute background for the motion of objects and the physical laws that govern their behavior. This is modern physics in a nutshell: Objects move and interact with each other on the background of space, which is assumed to exist.
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Einstein took this one step further with general relativity, where space is promoted from a background stage to a starring actor — a dynamic, flexible entity that responds to the presence of matter and directs the motion of that matter. It is space itself, and especially its dynamics, that gives rise to the force of gravity.
So is space just a mathematical abstraction, a tool we use to describe the relationship between physical objects, or is it something more? Here's an interesting thought: What about gravitational waves? Gravitational waves do not require the presence of matter or energy to move; they simply exist as undulations in space-time itself. So if space is just a mathematical tool, then how can the waves exist on their own?
There is no firm answer to the question of whether true nothingness can exist. It could be that the concept of space is just a mathematical trick and does not exist in its own right. Or it could be that no matter where you go, you're always somewhere in space, so you'll always be surrounded by something.
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