astronomy
A new ‘guest star’ will appear in the sky in 2024 − a space scientist explains how nova events work and where to look
The nova explosion in T Coronae Borealis, visible from Earth in 2024, will be a unique celestial event, unlike the supernova of 1054.
Vahe Peroomian, USC Dornsife College of Letters, Arts and Sciences
The stars aren’t fixed and unchanging, unlike what many ancient people thought. Once in a while, a star appears where there wasn’t one before, and then it fades away in a matter of days or weeks.
The earliest record of such a “guest star,” named so by ancient Chinese astronomers, is a star that suddenly appeared in skies around the world on July 4, 1054. It quickly brightened, becoming visible even during the day for the next 23 days.
Astronomers in Japan, China and the Middle East observed this event, as did the Anasazi in what is now New Mexico.
In the second half of 2024, a nova explosion in the star system called T Coronae Borealis, or T CrB, will once again be visible to people on Earth. T CrB will appear 1,500 times brighter than usual, but it won’t be as spectacular as the event in 1054.
I am a space scientist with a passion for teaching physics and astronomy. I love photographing the night sky and astronomical events, including eclipses, meteor showers and once-in-a-lifetime astronomical events such as the T CrB nova. T CrB will become, at best, the 50th brightest star in the night sky – brighter than only half the stars in the Big Dipper. It might take some effort to find, but if you have the time, you’ll witness a rare event.
What is a nova?
In 1572, the famous Danish astronomer Tycho Brahe observed a new star in the constellation Cassiopeia. After reporting the event in his work “De Nova Stella,” or “On the New Star,” astronomers came to associate the word nova with stellar explosions.
Stars, regardless of size, spend 90% of their lives fusing hydrogen into helium in their cores. How a star’s life ends, though, depends on the mass of the star. Very massive stars – those more than eight times the mass of our Sun – explode in dramatic supernova explosions, like the ones people observed in 1054 and 1572.
In lower mass stars, including our Sun, once the hydrogen in the core is exhausted, the star expands into what astronomers call a red giant. The red giant is hundreds of times its original size and more unstable. Eventually, all that is left is a white dwarf – an Earth-sized remnant made up of carbon and oxygen. White dwarves are a hundred thousand times denser than diamond. Unless they’re part of a binary star system, where two stars orbit each other, they slowly fade in brightness over billions of years and eventually disappear from sight.
T CrB is a binary star system – it’s made up of a red giant and a white dwarf, which orbit each other every 228 days at about half the distance between Earth and the Sun. The red giant is nearing the end of its life, so it has expanded dramatically, and it’s feeding material into a rotating disk of matter called an accretion disk, which surrounds the white dwarf.
Matter from the accretion disk, which is made mostly of hydrogen, spirals in and slowly accumulates on the surface of the white dwarf. Over time, this blanket of hydrogen becomes thicker and denser, until its temperature exceeds 18 million degrees Fahrenheit (10 million degrees Celsius).
A nova is a runaway thermonuclear reaction similar to the detonation of a hydrogen bomb. Once the accretion disk gets hot enough, a nova occurs where the hydrogen ignites, gets blown outward and emits bright light.
When will it occur?
Astronomers know of 10 recurrent novae – stars that have undergone nova explosions more than once. T CrB is the most famous of these. It erupts on average every 80 years.
Because T CrB is 2,630 light-years from Earth, it takes light 2,630 years to travel the distance from T CrB to Earth. The nova we will see later this year occurred over 2,000 years ago, but its light will be just reaching us later this year.
The accretion of hydrogen on the surface of the white dwarf is like sand in an 80-year hourglass. Each time a nova occurs and the hydrogen ignites, the white dwarf itself is unaffected, but the surface of the white dwarf is wiped clean of hydrogen. Soon after, hydrogen begins accreting on the surface of the white dwarf again: The hourglass flips, and the 80-year countdown to the next nova begins anew.
Careful observations during its past two novae in 1866 and 1946 showed that T CrB became slightly brighter about 10 years before the nova was visible from Earth. Then, it briefly dimmed. Although scientists aren’t sure what causes these brightness changes, this pattern has repeated, with a brightening in 2015 and a dimming in March 2023.
Based on these observations, scientists predict the nova will be visible to us sometime in 2024.
How bright will it be?
Astronomers use a magnitude system first devised by Hipparchus of Nicaea more than 2,100 years ago to classify the brightness of stars. In this system, a difference of 5 in magnitude signifies a change by a factor of 100 in brightness. The smaller the magnitude, the brighter the star.
In dark skies, the human eye can see stars as dim as magnitude 6. Ordinarily, the visible light we receive from T CrB comes entirely from its red giant, a magnitude 10 star barely visible with binoculars.
During the nova event, the white dwarf’s exploding hydrogen envelope will brighten to a magnitude 2 or 3. It will briefly become the brightest star in its home constellation, Corona Borealis. This maximum brightness will last only several hours, and T CrB will fade from visibility with the naked eye in a matter of days.
Where to look
Corona Borealis is not a prominent constellation. It’s nestled above Bootes and to the west of Ursa Major, home to the Big Dipper, in northern skies.
To locate the constellation, look due west and find Arcturus, the brightest star in that region of the sky. Then look about halfway between the horizon and zenith – the point directly above you – at 10 p.m. local time in North America.
Corona Borealis is approximately 20 degrees above Arcturus. That’s about the span of one hand, from the tip of the thumb to the tip of the pinky, at arm’s length. At its brightest, T CrB will be brighter than all the stars in Corona Borealis, but not as bright as Arcturus. https://www.youtube.com/embed/4FWiaWlMGLg?wmode=transparent&start=0 To find Corona Borealis, locate Arcturus, and then look about a handspan above.
You can also use an interactive star chart such as Stellarium, or one of the many apps available for smartphones, to locate the constellation. Familiarizing yourself with the stars in this region of the sky before the nova occurs will help identify the new star once T CrB brightens.
Although T CrB is too far from Earth for this event to rival the supernova of 1054, it is nevertheless an opportunity to observe a rare astronomical event with your own eyes. For many of us, this will be a once-in-a-lifetime event.
For children, however, this event could ignite a passion in astronomy. Eighty years in the future, they may look forward to observing it once again.
Vahe Peroomian, Professor of Physics and Astronomy, USC Dornsife College of Letters, Arts and Sciences
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
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Science
Jets from powerful black holes can point astronomers toward where − and where not − to look for life in the universe
David Garofalo, Kennesaw State University
One of the most powerful objects in the universe is a radio quasar – a spinning black hole spraying out highly energetic particles. Come too close to one, and you’d get sucked in by its gravitational pull, or burn up from the intense heat surrounding it. But ironically, studying black holes and their jets can give researchers insight into where potentially habitable worlds might be in the universe.
As an astrophysicist, I’ve spent two decades modeling how black holes spin, how that creates jets, and how they affect the environment of space around them.
What are black holes?
Black holes are massive, astrophysical objects that use gravity to pull surrounding objects into them. Active black holes have a pancake-shaped structure around them called an accretion disk, which contains hot, electrically charged gas.
The plasma that makes up the accretion disk comes from farther out in the galaxy. When two galaxies collide and merge, gas is funneled into the central region of that merger. Some of that gas ends up getting close to the newly merged black hole and forms the accretion disk.
There is one supermassive black hole at the heart of every massive galaxy.
Black holes and their disks can rotate, and when they do, they drag space and time with them – a concept that’s mind-boggling and very hard to grasp conceptually. But black holes are important to study because they produce enormous amounts of energy that can influence galaxies.
How energetic a black hole is depends on different factors, such as the mass of the black hole, whether it rotates rapidly, and whether lots of material falls onto it. Mergers fuel the most energetic black holes, but not all black holes are fed by gas from a merger. In spiral galaxies, for example, less gas tends to fall into the center, and the central black hole tends to have less energy.
One of the ways they generate energy is through what scientists call “jets” of highly energetic particles. A black hole can pull in magnetic fields and energetic particles surrounding it, and then as the black hole rotates, the magnetic fields twist into a jet that sprays out highly energetic particles.
Magnetic fields twist around the black hole as it rotates to store energy – kind of like when you pull and twist a rubber band. When you release the rubber band, it snaps forward. Similarly, the magnetic fields release their energy by producing these jets.
These jets can speed up or suppress the formation of stars in a galaxy, depending on how the energy is released into the black hole’s host galaxy.
Rotating black holes
Some black holes, however, rotate in a different direction than the accretion disk around them. This phenomenon is called counterrotation, and some studies my colleagues and I have conducted suggest that it’s a key feature governing the behavior of one of the most powerful kinds of objects in the universe: the radio quasar.
Radio quasars are the subclass of black holes that produce the most powerful energy and jets.
You can imagine the black hole as a rotating sphere, and the accretion disk as a disk with a hole in the center. The black hole sits in that center hole and rotates one way, while the accretion disk rotates the other way.
This counterrotation forces the black hole to spin down and eventually up again in the other direction, called corotation. Imagine a basketball that spins one way, but you keep tapping it to rotate in the other. The tapping will spin the basketball down. If you continue to tap in the opposite direction, it will eventually spin up and rotate in the other direction. The accretion disk does the same thing.
Since the jets tap into the black hole’s rotational energy, they are powerful only when the black hole is spinning rapidly. The change from counterrotation to corotation takes at least 100 million years. Many initially counterrotating black holes take billions of years to become rapidly spinning corotating black holes.
So, these black holes would produce powerful jets both early and later in their lifetimes, with an interlude in the middle where the jets are either weak or nonexistent.
When the black hole spins in counterrotation with respect to its accretion disk, that motion produces strong jets that push molecules in the surrounding gas close together, which leads to the formation of stars.
But later, in corotation, the jet tilts. This tilt makes it so that the jet impinges directly on the gas, heating it up and inhibiting star formation. In addition to that, the jet also sprays X-rays across the galaxy. Cosmic X-rays are bad for life because they can harm organic tissue.
For life to thrive, it most likely needs a planet with a habitable ecosystem, and clouds of hot gas saturated with X-rays don’t contain such planets. So, astronomers can instead look for galaxies without a tilted jet coming from its black hole. This idea is key to understanding where intelligence could potentially have emerged and matured in the universe.
Black holes as a guide
By early 2022, I had built a black hole model to use as a guide. It could point out environments with the right kind of black holes to produce the greatest number of planets without spraying them with X-rays. Life in such environments could emerge to its full potential. https://www.youtube.com/embed/b7mTVX9IE0s?wmode=transparent&start=0 Looking at black holes and their role in star formation could help scientists predict when and where life was most likely to form.
Where are such conditions present? The answer is low-density environments where galaxies had merged about 11 billion years ago.
These environments had black holes whose powerful jets enhanced the rate of star formation, but they never experienced a bout of tilted jets in corotation. In short, my model suggested that theoretically, the most advanced extraterrestrial civilization would have likely emerged on the cosmic scene far away and billions of years ago.
David Garofalo, Professor of Physics, Kennesaw State University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
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The Knowledge
The Mystical Glow of the Night Sky: Exploring Zodiacal Light
Zodiacal light, seen before sunrise, is sunlight scattering off interplanetary dust in the zodiacal cloud. It represents a cosmic connection, best viewed in dark, clear locations during specific times of the year.
Have you ever looked up at the night sky and noticed a faint glow, gracefully extending from the horizon in a triangular shape? This enchanting phenomenon is known as zodiacal light, often referred to as “false dawn” when it’s visible just before sunrise. While it may seem like a mere trick of the light, the zodiacal light holds a fascinating story about the universe surrounding our planet.
The Science Behind Zodiacal Light
Zodiacal light is the result of sunlight scattering off interplanetary dust, creating a delicate illumination in the night sky. This dust resides in a thick, pancake-shaped cloud known as the zodiacal cloud, which orbits in the ecliptic plane of our Solar System. Ranging from 10 to 300 micrometers in size, these tiny particles have masses that can span from one nanogram to several micrograms. Together, they contribute to what we see as a soft glow, complementing the natural light of a moonless night.
Interestingly, zodiacal light can be seen most effectively in dark locations, far away from the interference of city lights or moonlight. When conditions are perfect—a clear night with minimal light pollution—this soft glow stretches from the direction of the Sun, gracefully illuminating the darker parts of the sky. It’s most prominent in the western sky during spring after sunset and in the eastern sky during autumn before dawn.
The Origins of Cosmic Dust
The source of the dust that creates zodiacal light has long been a subject of exploration and debate. Initially thought to originate from active comet tails or collisions among asteroids, recent research suggests that a significant portion of the dust comes from the gradual fragmentation of dormant comets, specifically those in the Jupiter-family category.
When comets break apart, they send tiny fragments scattering through space. As these particles eventually disintegrate further due to collisions and space weathering, they continue to replenish the zodiacal dust cloud. This dynamic relationship ensures that our view of zodiacal light is not just a fleeting moment, but a persistent feature of our cosmic environment.
Viewing Zodiacal Light: Tips and Tricks
To catch a glimpse of this celestial beauty, timing and location are crucial. For those in mid-latitude regions, the ideal times to observe zodiacal light are during the evenings in spring and mornings in autumn. Choose a spot far from city lights, under a clear and moonless sky. As twilight fades, lean back, breathe in the fresh evening air, and let your eyes adjust to the darkness.
The sight will often reveal a column of light that appears brighter near the horizon and tilts at an angle parallel to the ecliptic. Often mistaken for a glimpse of the Milky Way, zodiacal light offers a serene reminder of the intricate cosmos we inhabit.
The Connection to Gegenschein
Zodiacal light isn’t the only celestial phenomenon related to interplanetary dust. There’s also the gegenschein, or “counterglow,” which is a faint oval glow seen directly opposite the Sun. This unique aspect of zodiacal light and gegenschein adds depth to our understanding of celestial phenomena and invites us to ponder our place in the universe.
A Cosmic Invitation
Zodiacal light is not just a backdrop for the stars; it represents a beautiful, cosmic connection between our planet and the infinity beyond. It serves as a gentle reminder of the fleeting moments in nature—moments that encourage us to pause, look up, and marvel at the intricate dance of light and dust that swirls around us.
So next time you find yourself under a dark sky, take a moment to seek out this enchanting glow. The zodiacal light is waiting, inviting you to experience the magic of our universe. Happy stargazing!
For more information visit these links:
Wikipedia: https://en.wikipedia.org/wiki/Zodiacal_light
Earth-Sky: https://earthsky.org/astronomy-essentials/zodiacal-light-false-dusk-how-to-see-explanation/
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
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astronomy
A Celestial Spectacle: Witness the Rare Planetary Parade on February 28
On February 28, 2025, a rare planetary parade will showcase all seven planets aligning in the night sky. This remarkable event won’t occur again until 2040, making it unmissable.
Planetary Parade
Astronomy enthusiasts and casual stargazers alike have something extraordinary to look forward to at the end of February. For one brief moment, on the evening of February 28, 2025, all seven planets—Mars, Jupiter, Uranus, Venus, Neptune, Mercury, and Saturn—will align in the night sky, creating a captivating planetary parade. This remarkable event marks the last time such an alignment will be visible until 2040, making it an occasion not to be missed.
What to Expect
The planetary parade will unfold shortly after sunset, with each planet showcasing its brilliance against the backdrop of the evening sky. While most of these celestial bodies will shine brighter than even the brightest stars, Uranus and Neptune will likely require binoculars or a telescope for a better view.
Currently, six of the planets are already aligned, but stargazers will have to wait until February 28 for Mercury to make its debut just above the horizon. Dr. Christopher Barnes, a senior lecturer at the University of Derby, explains the visibility details: “Mars will appear in the east, Jupiter and Uranus in the southeast, and Venus, Neptune, and Saturn in the west.”
Viewing Tips
For those wishing to experience this cosmic event, the best time to observe will be just after sunset when the stars begin to appear. Dr. Barnes suggests that even people in urban areas, where light pollution is often an issue, will be able to see most of the planets. However, seeking a location away from city lights will enhance the viewing experience.
The Benefits of Stargazing
Beyond the thrilling visual spectacle, taking time to gaze upon the stars and planets offers numerous benefits for one’s mental and emotional well-being. Dr. Barnes points out that stargazing encourages mindfulness, allowing individuals to detach from the stresses of daily life. “Engaging with the night sky fosters a sense of peace, restoration, and perspective,” he says.
Future Events
After February 28, the next opportunity to see a planetary alignment of five or more planets will occur in late October 2028 and again in February 2034. However, another seven-planet alignment will not be witnessed for another 15 years, making this February a particularly special occasion.
To cater to those unable to view the parade due to unfavorable weather or light pollution, several observatories will provide live streams of the event. This means everyone can partake in this astral celebration from the comfort of their homes.
As we approach February 28, it’s time to mark your calendars for this rare planetary parade. Whether you grab your telescope, plan a trip to a dark-sky location, or tune in to a live stream, don’t miss your chance to witness this extraordinary alignment of the planets, a spectacle that will be remembered long after it fades from view. Prepare to look up and enjoy the wonders of our solar system!
Resources:
Who doesn’t love a parade, especially a planet parade? How and when to see up to 7 planets
Planetary Parade will soon be visible in the evening sky
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
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