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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Space and Tech
NEOWISE, the NASA mission that cataloged objects around Earth for over a decade, has come to an end
Toshi Hirabayashi, Georgia Institute of Technology and Yaeji Kim, University of Maryland
The NASA project NEOWISE, which has given astronomers a detailed view of near-Earth objects – some of which could strike the Earth – ended its mission and burned on reentering the atmosphere after over a decade.
On a clear night, the sky is full of bright objects – from stars, large planets and galaxies to tiny asteroids flying near Earth. These asteroids are commonly known as near-Earth objects, and they come in a wide variety of sizes. Some are tens of kilometers across or larger, while others are only tens of meters or smaller.
On occasion, near-Earth objects smash into Earth at a high speed – roughly 10 miles per second (16 kilometers per second) or faster. That’s about 15 times as fast as a rifle’s muzzle speed. An impact at that speed can easily damage the planet’s surface and anything on it.
Impacts from large near-Earth objects are generally rare over a typical human lifetime. But they’re more frequent on a geological timescale of millions to billions of years. The best example may be a 6-mile-wide (10-kilometer-wide) asteroid that crashed into Earth, killed the dinosaurs and created Chicxulub crater about 65 million years ago.
Smaller impacts are very common on Earth, as there are more small near-Earth objects. An international community effort called planetary defense protects humans from these space intruders by cataloging and monitoring as many near-Earth objects as possible, including those closely approaching Earth. Researchers call the near-Earth objects that could collide with the surface potentially hazardous objects.
NASA began its NEOWISE mission in December 2013. This mission’s primary focus was to use the space telescope from the Wide-field Infrared Survey Explorer to closely detect and characterize near-Earth objects such as asteroids and comets.
NEOWISE contributed to planetary defense efforts with its research to catalog near-Earth objects. Over the past decade, it helped planetary defenders like us and our colleagues study near-Earth objects.
Detecting near-Earth objects
NEOWISE was a game-changing mission, as it revolutionized how to survey near-Earth objects.
The NEOWISE mission continued to use the spacecraft from NASA’s WISE mission, which ran from late 2009 to 2011 and conducted an all-sky infrared survey to detect not only near-Earth objects but also distant objects such as galaxies.
The spacecraft orbited Earth from north to south, passing over the poles, and it was in a Sun-synchronous orbit, where it could see the Sun in the same direction over time. This position allowed it to scan all of the sky efficiently.
The spacecraft could survey astronomical and planetary objects by detecting the signatures they emitted in the mid-infrared range.
Humans’ eyes can sense visible light, which is electromagnetic radiation between 400 and 700 nanometers. When we look at stars in the sky with the naked eye, we see their visible light components.
However, mid-infrared light contains waves between 3 and 30 micrometers and is invisible to human eyes.
When heated, an object stores that heat as thermal energy. Unless the object is thermally insulated, it releases that energy continuously as electromagnetic energy, in the mid-infrared range.
This process, known as thermal emission, happens to near-Earth objects after the Sun heats them up. The smaller an asteroid, the fainter its thermal emission. The NEOWISE spacecraft could sense thermal emissions from near-Earth objects at a high level of sensitivity – meaning it could detect small asteroids.
But asteroids aren’t the only objects that emit heat. The spacecraft’s sensors could pick up heat emissions from other sources too – including the spacecraft itself.
To make sure heat from the spacecraft wasn’t hindering the search, the WISE/NEOWISE spacecraft was designed so that it could actively cool itself using then-state-of-the-art solid hydrogen cryogenic cooling systems.
Operation phases
Since the spacecraft’s equipment needed to be very sensitive to detect faraway objects for WISE, it used solid hydrogen, which is extremely cold, to cool itself down and avoid any noise that could mess with the instruments’ sensitivity. Eventually the coolant ran out, but not until WISE had successfully completed its science goals.
During the cryogenic phase when it was actively cooling itself, the spacecraft operated at a temperature of about -447 degrees Fahrenheit (-266 degrees Celsius), slightly higher than the universe’s temperature, which is about -454 degrees Fahrenheit (-270 degrees Celsius).
The cryogenic phase lasted from 2009 to 2011, until the spacecraft went into hibernation in 2011.
Following the hibernation period, NASA decided to reactivate the WISE spacecraft under the NEOWISE mission, with a more specialized focus on detecting near-Earth objects, which was still feasible even without the cryogenic cooling.
During this reactivation phase, the detectors didn’t need to be quite as sensitive, nor the spacecraft kept as cold as it was during the cryogenic cooling phase, since near-Earth objects are closer than WISE’s faraway targets.
The consequence of losing the active cooling was that two long-wave detectors out of the four on board became so hot that they could no longer function, limiting the craft’s capability.
Nevertheless, NEOWISE used its two operational detectors to continuously monitor both previously and newly detected near-Earth objects in detail.
NEOWISE’s legacy
As of February 2024, NEOWISE had taken more than 1.5 million infrared measurements of about 44,000 different objects in the solar system. These included about 1,600 discoveries of near-Earth objects. NEOWISE also provided detailed size estimates for more than 1,800 near-Earth objects.
Despite the mission’s contributions to science and planetary defense, it was decommissioned in August 2024. The spacecraft eventually started to fall toward Earth’s surface, until it reentered Earth’s atmosphere and burned up on Nov. 1, 2024.
NEOWISE’s contributions to hunting near-Earth objects gave scientists much deeper insights into the asteroids around Earth. It also gave scientists a better idea of what challenges they’ll need to overcome to detect faint objects.
So, did NEOWISE find all the near-Earth objects? The answer is no. Most scientists still believe that there are far more near-Earth objects out there that still need to be identified, particularly smaller ones.
To carry on NEOWISE’s legacy, NASA is planning a mission called NEO Surveyor. NEO Surveyor will be a next-generation space telescope that can study small near-Earth asteroids in more detail, mainly to contribute to NASA’s planetary defense efforts. It will identify hundreds of thousands of near-Earth objects that are as small as about 33 feet (10 meters) across. The spacecraft’s launch is scheduled for 2027.
Toshi Hirabayashi, Associate Professor of Aerospace Engineering, Georgia Institute of Technology and Yaeji Kim, Postdoctoral Associate in Astronomy, University of Maryland
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 exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to illuminate 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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As we gaze up at the night sky, pondering the vastness of the universe, an intriguing event is set to unfold: a football field-sized asteroid is making its way past Earth tomorrow. Named 2006 WB, this celestial traveler is estimated by NASA’s Jet Propulsion Laboratory (JPL) to be about 310 feet across, although its size could range anywhere from 240 to 525 feet. For perspective, a football field measures approximately 360 feet in width, making this asteroid a formidable presence as it skims by our planet.
Enjoy this post in TikTok: https://www.tiktok.com/t/ZTYhPEJhb/
Approaching Asteroid
At a distance of 554,000 miles—roughly twice the distance to the Moon—2006 WB will pass by us at a speed of about 4.2 km/s, or approximately 9,400 mph. This velocity is several times faster than a bullet fired from a rifle, which can travel up to around 2,700 mph. While 554,000 miles may sound distant, it is remarkably close on a solar system scale, especially when compared to our neighboring planet Venus, which can be about 24 million miles away at its closest approach.
In addition to 2006 WB, there are four other asteroids making their own close passes in the coming days. Today, two bus-sized asteroids, 2024 WF2 and 2024 WJ3, will soar past Earth at distances of 1,780,000 miles and 2,780,000 miles, respectively. Following them, the plane-sized 2009 WB105 will come within 3,600,000 miles, and on Tuesday, another bus-sized asteroid, 2024 WD3, will pass at around 1,080,000 miles.
Jay Tate, director of the United Kingdom’s Spaceguard Centre observatory, highlights that asteroids are frequently zipping past Earth, often without much public awareness. 2006 WB falls into the category of Near-Earth Objects (NEOs), defined as objects that come within 30 million miles of our planet. NEOs are monitored closely, with over 34,000 identified in our solar system, and the JPL’s Center for Near-Earth Object Studies (CNEOS) actively tracking at least 2,300 potentially hazardous asteroids (PHAs).
While the odds of a large asteroid impacting Earth are exceedingly low, the consequences of such an event could be catastrophic. Svetla Ben-Itzhak, an assistant professor of space and international relations at Johns Hopkins University, warns that a cosmic body of 460 feet in diameter could obliterate an entire city and wreak regional havoc. In contrast, larger objects exceeding 1 kilometer in diameter could have far-reaching global implications, potentially leading to mass extinction.
Fortunately, the asteroids currently making their approach, including 2006 WB, do not fall within the category of potentially hazardous objects due to their size and the distances they will maintain from our planet. As we continue to advance our understanding of these celestial bodies, the importance of tracking and monitoring NEOs remains paramount for the safety of humanity.
As we prepare for the close encounter with 2006 WB, let us appreciate the wonders of our universe and the ongoing efforts of scientists and astronomers dedicated to keeping watch over our cosmic neighborhood. Stay tuned for more updates as we witness the majestic dance of these asteroids in the sky above.
Related link:
https://www.newsweek.com/asteroid-near-earth-object-approaching-football-field-space-nasa-1990996
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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In a remarkable demonstration of both the unpredictability of space and the extraordinary capabilities of modern astronomical detection, a small asteroid, designated 2024 UQ, recently made headlines after it struck Earth just hours after being identified. This event, which took place on October 22, 2024, marks the third “imminent impactor” recorded this year, highlighting the continual and often daunting reality of near-Earth objects (NEOs).
Discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii, a network of four telescopes dedicated to scanning the night sky for potential collision threats, 2024 UQ was small—measuring only about 3 feet (1 meter) in diameter. While news of an asteroid making contact with Earth can evoke concern, there was no cause for alarm in this instance. The diminutive size of the asteroid meant that it posed very little threat to anything on the ground. In fact, it burned up in the atmosphere over the Pacific Ocean near California, leaving no trace or damage.
However, the swift timeline of events raises critical questions about the effectiveness of our current monitoring systems. The impact occurred just two hours after the initial detection, which meant that by the time data was transmitted to the impact monitoring systems operated by the European Space Agency’s Near-Earth Object Coordination Center, the impact had already taken place. According to their November 2024 newsletter, the ATLAS survey had successfully obtained images identifying the asteroid on a collision trajectory, but due to its position near the edge of two adjacent observational fields, it was not recognized as a significant threat until it was too late.
This incident serves as a reminder of the complexities involved in tracking and predicting the paths of NEOs. While advancements in technology have undoubtedly improved our ability to detect these celestial objects, the circumstances surrounding 2024 UQ showcase the potential for oversights in our monitoring capabilities. Despite this event being minor in scale, it emphasizes the importance of continued investment in space surveillance systems, as well as international collaboration in tracking potential hazards lurking in the vast expanse of space.
As we look forward, this close encounter reaffirms the need for vigilance in our exploration and observation of the cosmos. Each NEO presents an opportunity for learning and growth in our understanding of near-Earth dynamics. While 2024 UQ may have come and gone without incident, it certainly sparks curiosity about what lies ahead in our ongoing quest to safeguard our planet from the skies.
Reference Links:
Asteroid Terrestrial-impact Last Alert System (ATLAS): https://fallingstar.com/
The Danger from Asteroid Impact: https://fallingstar.com/danger.php
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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