Light pollution ruins dark skies. It’s a scourge that ground-based observatories have to deal with in one form or another. Scientists used a small observatory in Japan to measure what changed when a nearby town improved its lighting practices. They also noted the challenges it still faces.
Bisei Town lies in a semi-rural area in the southwestern part of Okayama Prefecture in Japan. It’s a designated dark sky place and the locals are adamant about keeping their view of the stars. However, they still have to contend with light pollution from other cities in the region. The town itself has several astronomical observation posts, including the Bisei Astronomical Observatory. That facility sports a 101-cm telescope, along with smaller instruments, and is open to the public for sky viewing year-round.
The town enacted light pollution ordinances in 1989, making it the first local government in Japan to pass such a law. Several years ago, the town and observatory, along with other partners, worked with Panasonic to create a dark sky-friendly region. As part of the effort, the town replaced all its public lighting with LEDs that have a color temperature of 3000K or less. As a result, Bisei was certified by DarkSky International (formerly the International Dark-Sky Association) as “DarkSky Approved.” However, there are still some very bright, higher-temperature LEDs still in use, particularly in neighboring towns, where the populations are a half-million or more. Their light continues to create problems.
What does Light do to Dark Skies?
In general, light pollution is a growing global problem. It dims the sky, obstructs the view, and makes life more difficult for astronomers. The most obvious effect of light pollution anywhere is its ability to wipe out the view of dim and distant objects. For visible-light observers, that means they can’t detect faraway galaxies or measure variations in variable stars (for example). Astronomers who want to take spectra of specific objects often find their work “polluted” by such things as light from mercury-vapor lamps and other sources.
Urban sprawl and accompanying light pollution is an issue for both astronomers and fireflies. This view shows the light dome from the city of Duluth, Minn. 20 miles north of town. It erases the dark skies. Credit: Bob King
Light pollution affects more than the night sky, however. Study after study shows that it affects human health and safety. Ironically, one of the reasons given for increased lighting in many places is “safety”. However, aiming lights willy-nilly to provide a safe place often results in light trespass. It also creates an unintended effect: bright lights aimed directly at people’s eyes often blind them to dangers hidden in shadows, or to cars and pedestrians on brightly lit streets. In addition, light pollution has definite effects on other forms of life, from migrating birds to ocean populations.
A short video showing how lighting can actually provide the opposite of safety. Courtesy: DarkSky.org.
In recent decades, organizations such as DarkSky International, the American Astronomical Society, and the International Astronomical Union have been joined by architects, safety officials, and others to work on solutions to light pollution. For some places, that works very well and dark skies are returning while maintaining required lighting for safety. In other places, there’s still a lot of work to be done. The recent rise in the use of LEDs for lighting poses some of the same problems that incandescent lighting does. Astronomers and others continue to work on recommendations for the wise use of such lighting to mitigate the problems of light pollution.
Are there Dark Skies Over Bisei?
Japanese astronomers Ryosuke Itoh and Syota Maeno decided to monitor how the light pollution ordinances in Bisei Town have affected viewing at the Bisei Observatory. The town has replaced all of the fluorescent lights with LED lamps, which they hoped would reduce sky brightness in the nearby region. However, light pollution from these and lights farther away is still scattered by the atmosphere, which can result in a perceptible sky glow.
Sky brightness is one way of determining the effects of light pollution. It can be measured in several ways. One is to photograph the entire sky with an all-sky lens-equipped camera. That gives you a wide-angle view. Another way is to use a CCD camera attached to a telescope to get a good view of the entire sky. Finally, you can use a specially equipped sky meter that gives a photometric value to sky brightness. Itoh and Maeno used this third method to measure the skies over the Bisei Observatory. They also used sky spectra dating between 2006 to 2023 to see if the changes in lighting affected the data.
Sky spectra from BAO from 2006 to 2023. Different colors represent different years. Spectra of LEDs and fluorescent lamps taken with the same instruments are shown for comparison (bottom). Courtesy Itoh, et al.
What they found with their all-sky measurements and data analysis is something of a mixed bag. Bisei Town itself now has an observed sky brightness on the Bortle Scale of class 4. That corresponds roughly to a rural/suburban transition zone. In part, the shift to lower color-temperature LEDs in place of bright incandescent lamps did reduce some light pollution in town. However, Itoh and Maeno observed a very definite spectral line around 4500 A that they call a “blue hump”. It comes from the bright white, higher-temperature LEDs still in use in nearby towns, but they couldn’t directly identify all the sources specifically.
Future Work
In a paper they are submitting for publication, the two scientists conclude that while Bisei Town’s skies are not outstandingly dark, there is some improvement since the lighting changes were made. However, the night sky is still affected by light pollution from nearby areas, and more work needs to be done in those regions to mitigate the problem.
Most importantly, they note how important it is to separate the distinct origins of light pollution in any given area. While Bisei Town may well have improved its local environment, it still has to deal with scatted light from large metropolitan areas. Identifying those specific light pollution sources will be a big step towards helping those municipalities find ways to reduce the light pollution problems of their smaller rural neighbors.
A recent study accepted to The Astrophysical Journal uses computer models to investigate why the exoplanet, TRAPPIST-1c, could not possess a thick carbon dioxide (CO2) atmosphere despite it receiving the same amount of solar radiation from its parent star as the planet Venus receives from our Sun, with the latter having a very thick carbon dioxide atmosphere. This study comes after a June 2023 study published in Nature used data from NASA’s James Webb Space Telescope (JWST) to ascertain that TRAPPIST-1c does not possess a carbon dioxide atmosphere. Both studies come as the TRAPPIST-1 system, which is located approximately 41 light-years from Earth and orbits its star in just 2.4 days, has received a lot of attention from the scientific community in the last few years due to the number of confirmed exoplanets within the system and their potential for astrobiology purposes.
Artist illustration of TRAPPIST-1c with TRAPPIST-1b in the background. (Credit: NASA, ESA, CSA, Joseph Olmsted (STScI))
Light curve data of TRAPPIST-1c obtained by JWST as part of the June 2023 study, which contributed to this most recent study. (Credit: NASA, ESA, CSA, Joseph Olmsted (STScI))
“The TRAPPIST-1 system is special because it hosts seven approximately Earth-sized planets that exist in orbital locations interior to, within, and outside of the habitable zone, where liquid water may exist,” Katie Teixeria, who is a Graduate Research Assistant in the Department of Astronomy at The University of Texas at Austin and lead author of the study, tells Universe Today. “Since TRAPPIST-1 is an M dwarf star (unlike the Sun, which is a G type star), we are uncertain whether its planets can retain atmospheres, which is a prerequisite for habitability. By searching for atmospheres in the TRAPPIST-1 system, we get the first clues as to whether M dwarf systems, which make up about 70% of stars in our galaxy, are conducive to life.”
For the study, the researchers used a series of computer models to simulate the evolution of TRAPPIST-1c’s atmosphere, specifically pertaining to how much of the planet’s atmosphere was lost over time from the parent star’s solar radiation, also known as stellar (solar) wind stripping. In the end, the results indicated that TRAPPIST-1c potentially experienced a removal of approximately 16 bars of CO2 gas, which the researchers note is less than the current amount of CO2 on Earth or Venus.
Video discussing the findings of TRAPPIST-1c obtained by JWST in June 2023.
Therefore, the researchers concluded two possible scenarios for explaining the lack of CO2 loss during TRAPPIST-1c’s lifetime: either the planet initially formed with low amounts of volatiles, which often include carbon dioxide, nitrogen, water, and hydrogen, and are found on both Earth and Venus in respective large quantities; or TRAPPIST-1c experienced substantial amounts of stellar wind stripping during its early history.
“The major takeaway from this study is that long-term stellar wind stripping in the TRAPPIST system is not strong enough to remove a large CO2 atmosphere from TRAPPIST-1c, and, therefore, TRAPPIST-1c has likely been carbon-deficient for most of its lifetime,” Teixeria tells Universe Today.
2017 video discussing the initial discovery of the TRAPPIST-1 system.
In addition to investigating stellar wind stripping on TRAPPIST-1c, the researchers also used these same computer models to investigate how the other six planets within the TRAPPIST-1 system were affected by stellar wind stripping and if they could keep their atmospheres over long timescales. These planets, which are currently hypothesized to be Earth-sized and rocky worlds, include TRAPPIST-1b, TRAPPIST-1d, TRAPPIST-1e, TRAPPIST-1f, TRAPPIST-1g, and TRAPPIST-1h, with TRAPPIST-1b orbiting inside of TRAPPIST-1c and e, f, and g residing within the star’s HZ.
What makes the TRAPPIST-1 system unique is the extremely compact distances of the planets to each other, as all seven orbit well within the orbit of Mercury, making the investigation into potential stellar wind stripping even more enticing. However, despite their compact orbits, the researchers made an intriguing discovery using their computer models.
Credit: NASA/JPL-Caltech
Teixeria tells Universe Today, “We predict that the more distant TRAPPIST-1 planets may retain atmospheres because the atmospheric mass-loss due to stellar wind decreases with the square of distance from the star, and the runaway greenhouse effect is unlikely to occur on these distant, colder planets. This means that water and other molecules are likely to stay closer to the surface rather than evaporate away from the planet.”
Going forward, the researchers note that future JWST observations will allow them to gain a better understanding of the makeup and sizes of the atmospheres for all the TRAPPIST-1 planets.
What new discoveries will researchers make about the TRAPPIST-1 system and their planetary atmospheres in the coming years and decades? Only time will tell, and this is why we science!
Life, as we all know, is based on chemistry. Prebiotic chemical building blocks existed on our planet for a long time before life arose. Astrobiology and cosmochemistry focus on the formation of those building blocks. They also look at the role each played in creating all the life forms we know today.
For a long time, cosmo-chemists have known that organic molecules called polycyclic aromatic hydrocarbons (PAHs) are quite plentiful in the Universe. Scientists consider them plausible prebiotic building blocks that likely played an important role in the formation of life on Earth. What’s not as well understood is their origin story. For a long time, scientists suspected that they formed in regions where temperatures get to around 1000 K. That would supply energy to promote chemical activity to create PAHs, such as in star-forming molecular clouds or circumstellar disks. It’s also possible they form as part of the processing of carbon-rich dust grains by nearby energy sources (such as stars).
However, based on recent studies of an asteroid and meteorite, it turns out that some PAHs formed in cold regions of space, too. In those regions, the temperature does not get much higher than 100 K. That finding opens up new pathways for understanding life’s chemical journey on other planets and celestial bodies.
Understanding These Organic Molecules
According to Professor Kliti Grice, a researcher at the Western Australia Organic and Isotope Geochemistry Centre at Curtin University, understanding these materials is a big step. “PAHs are organic compounds made up of carbon and hydrogen that are common on Earth but are also found in celestial bodies like asteroids and meteorites,” said Grice.
They’re spread throughout the interstellar medium and detected in galaxies across the Universe. Generally, they’re used as a tracer of cold molecular gas, which is where stars—and planets—begin their formation journey.
An image of an interstellar nebula with some polycyclic aromatic hydrocarbon (PAH) molecular structures superimposed. These organic molecules exist throughout the Universe. Courtesy: NASA.
As such, scientists want to trace their path from space to Earth and compare space-based PAHs to Earth-based ones. That’s because PAHs are a very likely precursor to the kinds of materials that eventually lead to the formation of life. That makes their presence on other celestial bodies intriguing as scientists work to understand the formation and evolution of life.
Beyond Earth, PAHs account for about 30 percent of all carbon found in regions around stars, in molecular clouds, and on planets (and other bodies). On Earth, many PAHs exist in coal deposits and oil reservoirs. Plants burning (as in forest fires) also produce these compounds. They work their way into the soil and eventually end up in plants (among other things).
Organic Molecules and Rocky Bodies
Grice is part of an international research team that focused on pieces of asteroid Ryugu and the famous Murchison meteorite to figure out where their PAHs formed. The team started with an unusual chemistry project: burning plants. That’s because plants contain PAHs that form here on Earth. “We performed controlled burn experiments on Australian plants,” said Grice, “which were isotopically compared to PAHs from fragments of the Ryugu asteroid that were returned to Earth by a Japanese spacecraft in 2020, and the Murchison meteorite that landed in Australia in 1969. The bonds between light and heavy carbon isotopes in the PAHs were analyzed to reveal the temperature at which they were formed.”
The Murchison Meteorite, which fell to Earth in 1969. It contains organic molecules. Courtesy Basilicofresco, CC BY-SA 3.0
Using high-tech methods to study Ryugu and Murchison, the team found two sources of PAHs with slightly different characteristics. “The smaller ones likely formed in cold outer space, while bigger ones probably formed in warmer environments, like near a star or inside a celestial body,” according to Grice.
Ryugu is particularly interesting since it formed early in the Solar System’s history. A critical analysis of its chemistry found several PAHs. The team also detected organosulfides (compounds with sulfur). These all likely formed in very cold interstellar clouds. That means they predate the formation of the Solar System, making bits of Ryugu older than the Sun and planets.
PAHs on the Pathway of Life
Why are scientists interested in PAHs? Their role as precursor compounds for life is intriguing. The fact that they can exist out in space opens up avenues of research into life beyond Earth. In addition, their presence gives new insight into the bodies that contain them.
Research team member Dr. Alex Holman said that studying the isotopic composition of PAHs found in celestial bodies offers a glimpse of their formation conditions. “This research gives us valuable insights into how organic compounds form beyond Earth and where they come from in space,” Dr Holman said. Ultimately, in the search for life elsewhere in the Universe, understanding the chemical pathways it takes through different formation environments will be important information.
Looking to the future, NASA is investigating several technologies that will allow it to accomplish some bold objectives. This includes returning to the Moon, creating the infrastructure that will let us stay there, sending the first crewed mission to Mars, exploring the outer Solar System, and more. This is particularly true of propulsion technologies beyond conventional chemical rockets and engines. One promising technology is the Rotating Detonation Engine (RDE), which relies on one or more detonations that continuously travel around an annular channel.
In a recent hot fire test at NASA’s Marshall Space Flight Center in Huntsville, Alabama, the agency achieved a new benchmark in developing RDE technology. On September 27th, engineers successfully tested a 3D-printed rotating detonation rocket engine (RDRE) for 251 seconds, producing more than 2,630 kg (5,800 lbs) of thrust. This sustained burn meets several mission requirements, such as deep-space burns and landing operations. NASA recently shared the footage of the RDRE hot fire test (see below) as it burned continuously on a test stand at NASA Marshall for over four minutes.
While RDEs have been developed and tested for many years, the technology has garnered much attention since NASA began researching it for its “Moon to Mars” mission architecture. Theoretically, the engine technology is more efficient than conventional propulsion and similar methods that rely on controlled detonations. The first hot fire test with the RDRE was performed at Marshall in the summer of 2022 in partnership with advanced propulsion developer In Space LLC and Purdue University in Lafayette, Indiana.
During that test, the RDRE fired for nearly a minute and produced more than 1815 kg (4,000 lbs) of thrust. According to Thomas Teasley, who leads the RDRE test effort at NASA Marshall, the primary goal of the latest test is to understand better how they can scale the combustor to support different engine systems and maximize the variety of missions they could be used for. This ranges from landers and upper-stage engines to supersonic retropropulsion – a deceleration technique that could land heavy payloads and crewed missions on Mars. As Teasley said in a recent NASA press release:
“The RDRE enables a huge leap in design efficiency. It demonstrates we are closer to making lightweight propulsion systems that will allow us to send more mass and payload further into deep space, a critical component to NASA’s Moon to Mars vision.”
Meanwhile, engineers at NASA’s Glenn Research Center and Houston-based Venus Aerospace are working with NASA Marshall to identify ways to scale the technology for larger mission profiles.
If we could travel far beyond our galaxy, and look back upon the Milky Way, it would be a glorious sight. Luminous spirals stretching from a central core, with dust and nebulae scattered along the spiral edges. When you think about a galaxy, you probably imagine a spiral galaxy like the Milky Way, but spirals make up only about 60% of the galaxies we see. That’s because spiral galaxies only form when smaller galaxies collide and merge over time. Or so we thought, as a new study suggests that isn’t the case.
The standard model of galaxies is that they evolve over time. Galaxies formed from vast clouds of primordial hydrogen and helium, and so likely had a fairly amorphous structure at the beginning. Given the density of the early Universe, galactic collisions and mergers were common, which gave galaxies their rotations and caused them to form disks and spirals. All of this takes time, so we would expect spiral galaxies to be fairly common in the local Universe, but rare in the early Universe.
This new work used data from the Cosmic Evolution Early Release Science Survey (CEERS), which was gathered by the James Webb Space Telescope. The team identified 873 galaxies greater than 10 billion solar masses, with redshifts between z = 0.5 and z = 4. Galaxies at this redshift are between 5 billion and 12 billion years old, so they span the range of early galaxies to modern ones.
The fraction of spiral galaxies as a function of redshift. Credit: Kuhn, et al
Of these galaxies, 216 were classified as spirals. The authors were careful to note that some may be merging galaxies that were misclassified, but even then 108 of the galaxies were unanimously classified as spirals by evaluators. When the team arranged them by redshift, they found that while the fraction of spirals decreased as you went further into the past, the fraction of spirals at redshifts above z = 3 was much higher than expected. When the team calibrated observations, they found about a fifth of galaxies at z = 3 are spiral galaxies. These very early galaxies would have had to become spirals less than two billion years after the Big Bang, meaning that there would have been little time for mergers and collisions to be the cause.
In other words, many galaxies evolved into disk-shaped spirals quite early in the Universe. So while collisions and mergers do play a role in the formation of spiral galaxies, there are likely other factors that come into play. At the moment it isn’t clear what those factors are. With future data from JWST, the team hopes to determine just how these early galaxies evolve, and why spiral galaxies have been around for so long.
Like many that grew up watching the skies, I have been captivated by the planets. Mars is no exception, with its striking red colour, polar caps and mysterious dark features. Many of the surface features have been driven by ancient volcanic activity but whether any geological activity moulds the terrain today is still subject to scientific debate. A recent study however has revealed that Mars is surprisingly active..even today!
Mars is the fourth planet from the Sun and has captivated our imagination for centuries. It’s often called the red planet due to the amount of iron oxide in the fine powdery, dusty surface material. The atmosphere is thin and tenuous and is believed to be unable to support life. Numerous probes have visited Mars to shape our current understanding but this new view is quite removed from the view during the days of Schiaparelli in the 19th Century. The poor quality telescopes of the day led to equally poor quality observations that erroneously recorded a surface criss-crossed with canals from an unknown alien civilization.
Until recently, it has also been thought that Mars was volcanically inactive but a recent study by a team led by Joana Voigt from the Arizona’s Lunar and Planetary Laboratory have shone new light on the story. The team combined data from ground penetrating radar and spacecraft images to develop a new model of Martian volcanism.
The use of the ground penetrating radar allowed the team to penetrate as deep as 140 meters below the surface and construct a 3D model of the lava flow in Elysium Planitia and use it to identify over 40 volcanic events with the most recent depositing at least 1,600 cubic kilometers of molten lava into the plain. Although the team are keen to stress that they have not observed any volcanic activity but believe that Mars may be far more active now than previously thought.
The study explored a vast, featureless plain on the Martian surface (which is known to be one of the youngest volcanic regions) and found far more volcanic activity than expected. They found significant quantities of lava that had been erupted from cracks and fissures spanning timescales as recent as one million years – geologically that’s just a few days ago.
Adding to the conclusion of a more active Mars than before is the number of quakes detected by NASA’s InSight lander in recent years. Evidence also points to a number of significant floods in Elysium Planitia and that has implications for the possibility of Mars ever being capable of supporting life. Not just floods but evidence of ‘geyser’ like hydrothermal vents all of which help to support a model of Mars that is far from dormant.
Our Milky Way bristles with giant molecular clouds birthing stars. Based on what we see here, astronomers assume that the process of star creation also goes on similarly in other galaxies. It makes sense since their stars have to form somehow. Now, thanks to JWST, astronomers have spotted baby stellar objects in a galaxy 2.7 million light-years away. That’s millions of light-years more distant than any previous observations of newly forming stars have reached.
The targets of JWST’s observations are “young stellar objects” (YSOs) in the Triangulum Galaxy (M33). Astronomers used the telescope’s mid-infrared imager (MIRI) to study one section of one of M33’s spiral arms in the hunt for YSOs. They found 793 of these baby stars, hidden inside massive clouds of gas and dust. That’s an important discovery, signaling that the processes of star birth we know so well in our galaxy occur as we expect them to in others.
About Young Stellar Objects
To put this discovery into some kind of context, let’s take a look at young stellar objects in a bit more detail. Generally speaking, these are simply stars in the earliest phases of their evolution. Starbirth begins when materials in a giant molecular cloud start to “clump together” gravitationally. The densest part of the clump gets denser, temperatures rise, and eventually, it starts to glow. Young stellar objects can be protostars still sweeping up mass from their giant molecular clouds. They aren’t quite stars yet—that is, they haven’t ignited fusion in their cores. That won’t happen for maybe half a billion years (more or less, depending on mass).
This image from Hubble Space Telescope, reveals a newly forming star within the Chamaeleon cloud in the Milky Way. This young star is throwing off narrow streams of gas from its poles — creating this ethereal object known as HH 909A. These structures are very common within star-forming regions like the Orion Nebula, or the Chameleon I molecular cloud.
Once the infall of gas onto an infant stellar core finishes the object becomes a pre-main-sequence stellar object. It’s still not officially a star. That happens when fusion ignites inside the star. Then it becomes a main-sequence star. Generally, it has cleared much of its birth cloud away and that makes it easier to observe.
Detecting Newly Forming Stars
Stars in in the earliest stages of formation are hard to observe even in our galaxy. For one thing, their birth clouds hide these infant stars. That makes it very hard to detect them in visible light. But, once they’re warm enough to glow, they emit infrared radiation. Given the right instruments, astronomers can easily detect that light. Infrared light is a primary tool astronomers use to search for areas where stars are just starting to form.
As they “grow up”, young stellar objects often emit jets of material. Those jets stand out in radio emissions, which can also be detected fairly easily. These baby stars also blow off material in outflows of material called bipolar flows. Astronomers detect these by looking for evidence of hot molecular hydrogen, or warm carbon monoxide molecules—again, in infrared wavelengths. Generally, these bipolar flows emanate from the very youngest objects less than 10,000 years old.
NASA’s James Webb Space Telescope’s high-resolution, near-infrared look at Herbig-Haro 211 reveals exquisite detail of the outflow of a newly forming young star, an infantile analog of our Sun. Image Credit: ESA/Webb, NASA, CSA, Tom Ray (Dublin)
Many young stars have circumstellar disks around them. These are part of the cloud that formed the star and continue to feed material into it. Eventually, this disk becomes the site of planetary formation, which is why astronomers often refer to them as “protoplanetary disks” or “proplyds”. These disks get observed in visible and infrared light by a variety of ground-based and space-based observatories.
All of these manifestations of star birth exist in our galaxy, particularly in the spiral arms, and astronomers have cataloged many of them. One of the best-known examples is the Orion Nebula. It hosts a number of these stellar infants, complete with protoplanetary disks, jets, and bipolar outflows. One particular object, called YSO 244-440, is part of the Orion Nebula Cluster, a grouping of very young stars. This stellar infant is still hidden in the circumstellar disk that gave it birth. Earlier in 2023, astronomers using the Very Large Telescope in Chile announced they’d observed a jet emanating from this object.
Young stellar objects with circumstellar disk, as seen in the Orion Nebula by Hubble Space Telescope. These newly forming stars may one day also have planetary systems around them.
In addition, astronomers used the Spitzer Space Telescope to observe these objects in the Large Magellanic Cloud, a satellite galaxy to the Milky Way. They’ve spotted at least a thousand YSO candidates in the Spitzer data, allowing them to trace the process of star birth outside our Milky Way.
Finding Newly Forming Stars in Other Galaxies
Astronomers want to understand the process of star formation in other galaxies because each one has a unique chemical environment and evolutionary history. Star formation helps fill in the story of galaxy evolution. That’s why it’s so important to look for YSOs in other galaxies.
Until now, looking for infant stars beyond our immediate galactic neighborhood has been nearly impossible. Spotting them requires very high-resolution imaging and infrared detection capabilities to discern these baby stars from their birth clouds. As happens in the Milky Way, the cloud surrounding the young stars absorb their visible light emissions. Also, if you have a number of them in one cloud, distinguishing one from another can be impossible at great distances. Telescopes such as Spitzer, Herschel, and ground-based observatories don’t have the high-resolution capability to detect all YSOs beyond the Large Magellanic Cloud.
This is where JWST comes in handy. It has high-resolution capability and is infrared-sensitive, which allows astronomers to study star-forming regions at greater distances. That’s why a team of observers used the telescope to look at the Triangulum Galaxy. It’s very similar to the Large Magellanic Cloud in terms of how many stars it makes, its metallicity, and its size. However, unlike the LMC, M33 has puffy spiral arms that are home to star birth regions in giant molecular clouds. So, it made a perfect target.
The team used the MIRI instrument to look at a 5.5-kiloparsec-sized section of M33’s southern spiral arms. They used previously made HST observations to identify likely sites of YSOs in the arm. Then they focused JWST on those sites. The result is a whopping catalog of nearly 800 individual candidate YSOs that they then analyzed.
A four-color image showing the MIRI data from JWST and HST data from the PHATTER survey. It shows the region of M33 where nearly 800 YSOs lie. Courtesy Peltonen, et al.
Analyzing the YSOs in the Triangulum Galaxy
After sorting the observations and classifying what they found, the astronomers came to some interesting conclusions about star formation in M33. They found that the most massive giant molecular clouds there host a great many young stellar object candidates. The numbers are about similar to what’s seen in similar clouds in the Milky Way. The spiral arm they studied seems to have a very efficient star-formation mechanism, which isn’t necessarily correlated with the mass of the giant molecular clouds there. They’re still trying to figure out why the spiral arm is such a star-formation engine.
It’s possible that even with JWST, we aren’t seeing into the earliest phases of star formation in that section of the Triangulum galaxy spiral arm. It’s also likely that M33’s spiral arms (which are described as “flocculent”) are different in several ways from the spiral arms of the Milky Way (for example). Flocculence could be caused by multiple episodes of star formation that affect the structure of the gas and dust clouds inside. Our own galaxy’s spiral arms are quite well-defined and certainly less flocculent than M33’s. That could point to an evolutionary change that takes place as a galaxy continues its star-forming activities. The astronomers also suggest that the region between spiral arms that they studied in M33 isn’t as efficient when it comes to star production.
Since this is a “first look” at star formation in a distant galaxy, astronomers will be using those observations to model what they think is happening in M33. Eventually, they should be able to use what they learn to make some very accurate estimates of just how much star formation is happening in the region they studied. Finally, they should be able to extrapolate that star formation rate to other arms in M33. That should give them much-needed insight into that galaxy’s evolutionary state and history.
The full, weird story of the quantum world is much too large for a single article, but the period from 1905, when Einstein first published his solution to the photoelectric puzzle, to the 1960’s, when a complete, well-tested, rigorous, and insanely complicated quantum theory of the subatomic world finally emerged, is quite the story.
This quantum theory would come to provide, in its own way, its own complete and total revision of our understanding of light. In the quantum picture of the subatomic world, what we call the electromagnetic force is really the product of countless microscopic interactions, the work of indivisible photons, who interact in mysterious ways. As in, literally mysterious. The quantum framework provides no picture as to how subatomic interactions actually proceed. Rather, it merely gives us a mathematical toolset for calculating predictions. And so while we can only answer the question of how photons actually work with a beleaguered shrug, we are at least equipped with some predictive power, which helps assuage the pain of quantum incomprehensibility.
Doing the business of physics – that is, using mathematical models to make predictions to validate against experiment – is rather hard in quantum mechanics. And that’s because of the simple fact that quantum rules are not normal rules, and that in the subatomic realm all bets are off.
Interactions and processes at the subatomic level are not ruled by the predictability and reliability of macroscopic processes. In the macroscopic world, everything makes sense (largely because we’ve evolved to make sense of the world we live in). I can toss a ball enough times to a child that their brain can quickly pick up on the reliable pattern: the ball leaves my hand, the ball follows an arcing path, the ball moves forward and eventually falls to the ground. Sure, there are variations based on speed and angle and wind, but the basic gist of a tossed ball is the same, every single time.
Not so in the quantum world, where perfect prediction is impossible and reliable statements are lacking. At subatomic scales, probabilities rule the day – it’s impossible to say exactly what any given particle will do at any given moment. And this absence of predictability and reliability at first troubled, and then disgusted, Einstein, who would eventually leave the quantum world behind with nothing more than a regretful shake of his head at the misguided work of his colleagues. And so he continued his labors, attempting to find a unified approach to joining the two known forces of nature, electromagnetism and gravity, with an emphatically not quantum framework.
When two new forces were first proposed in the 1930’s to explain the deep workings of atomic nuclei – the strong and weak nuclear forces, respectively – this did not deter Einstein. Once electromagnetism and gravity were successfully united, it would not take much additional effort to work in new forces of nature. Meanwhile, his quantum-leaning contemporaries took to the new forces with gusto, eventually folding them into the quantum worldview and framework.
By the end of Einstein’s life, quantum mechanics could describe three forces of nature, while gravity stood alone, his general theory of relativity a monument to his intellect and creativity.
As NASA continues to ramp up efforts for its Artemis program, which has the goal of landing the first woman and person of color on the lunar surface, two NASA astronauts recently conducted training with a replica of SpaceX’s Starship human landing system (HLS), albeit on a much smaller scale. Given that Starship is 50 meters (160 feet) tall, and the crew quarters are located near the top of Starship, the HLS will need an elevator with a basket to transport crew and supplies from the crew quarters down to the surface. The purpose of this training is to familiarize astronauts with all aspects of this system, including elevator and gate controls and latches, along with how the astronauts perform these tasks in their bulky astronaut suits, which both astronauts wore during the training.
The two NASA astronauts who participated in the recent training are Nicole Mann and Doug “Wheels” Wheelock. NASA Astronaut Mann is a Colonel in the United States Marine Corps who was selected as a NASA astronaut in the 2013 NASA Group 21. Her spaceflight experience includes 157 days in space as part of Expedition 68 onboard the International Space Station (ISS) and being launched aboard the SpaceX Crew-5 mission. NASA Astronaut Wheelock is a Colonel in the United States Army who was selected as a NASA astronaut in the 1998 NASA Group. His spaceflight experience includes 178 days in space as part of STS-120 and later as part of Expedition 24/25 on the ISS and being launched aboard the Soyuz TMA-19.
As noted, Starship is 50 meters (160 feet) tall and 9 meters (30 feet) in diameter and capable of landing 100 tons (99,790 kilograms/220,000 pounds) on the lunar surface, which is in stark contrast to the Apollo lunar module that landed 12 men on the lunar surface during the Apollo program, which was only 5.5 meters (17.9 feet) tall and approximately 4.3 meters (14 feet) in diameter and a mass of 15,103 kilograms (33,296 pounds) with fuel.
Ironically, the original plan for landing astronauts on the Moon during the Apollo program was known as direct ascent that involved a single, large vehicle with a payload of 74,000 kilograms (163,000 pounds) landing on the lunar surface. While NASA was in favor of using the direct ascent method in early 1961 since spacecraft rendezvous and docking had not been performed in Earth orbit yet, this was later scrapped in favor of the lunar orbit rendezvous (LOR) mission mode that was advocated by NASA aerospace engineer, John Houbolt, who estimated this would significantly reduce the weight involved in such a landing approach. LOR not only successfully landed six Apollo missions on the Moon, but it was also responsible for saving the Apollo 13 crew when one of their oxygen tanks ruptured and the crew was able to use the lunar module as a lifeboat as they flew around the Moon and came back to Earth.
As NASA astronauts train for using the Starship HLS elevator someday, Starship has already conducted two flight tests—Ship 24 in April 2023 and Ship 25 in November 2023, respectively. While both flights ended in failure, Ship 25 officially passed the Karman Line, which is the traditional boundary of outer space. A third Starship test flight is currently scheduled to occur sometime in the first quarter of 2024, which also comes as the crewed Artemis II mission is gearing up for their 10-day mission orbiting the Moon in November 2024 and Artemis III currently scheduled to land astronauts near the lunar south pole sometime in 2025.
How will Starship HLS help future Artemis astronauts on the lunar surface in the next few years? Only time will tell, and this is why we science!
Life appeared on Earth through a series of lucky coincidences, and that luck started with our Moon. None of the other planets of the inner solar system have significant moons. Space is lonely around Mercury and Venus. Mars does have two small moons, Phobos and Deimos (Fear and Despair, befitting companions for the God of War), but those are simply captured asteroids, lassoed in the not-too-distant past and doomed to eventually come close enough to their unloving parent to be torn to shreds by gravitational forces.
In fact, no other planet in the solar system – or any exoplanet known orbiting other stars – has a moon quite like the Moon. With the exception of Pluto and its companion Charon, no other planet has a satellite with the relative mass of Luna. The giant worlds like Jupiter and Saturn have some moons large enough to be planets in their own right, but they are insignificant next to the massive bulk of their parents. The Moon is roughly 1% the mass of the Earth, a percentage unheard of in the galaxy.
And, as is the nature of nature, we found ourselves with our satellite through the chance encounter of a violent collision. Billions of years ago, when our solar system was but a churning mass of gas and dust swirling around a fitful young star, the planets began to coalesce. But before they could become planets, they were mere planetesimals, agglomerations of rock and ice, dozens of them swarming in the chaos of those early days.
In the orbit of what would one day become the Earth, we were not alone. At some point, due to some accident of trajectory and conceit of momentum, a planetesimal the size of Mars struck us. The details of the collision and its aftermath are muddied; with no time machine we can only rely on computer simulations of the impact. But this much is clear: the cosmic accident vaporized part – and possibly the whole – of the Earth and its impactor, creating a ring of superheated plasma that looked more like a rage-filled donut than a proto-world.
But with time the fury ceased; the plasma cooled. The ring coalesced back into the shape of a sphere, but now with an orbiting companion. The traces of the impactor are almost lost to us, the evidence of its existence only slim. The Earth contains more heavy metals in its core than it should for a planet its size – a contribution from the interloper. And the Moon itself, when sampled to measure the composition of its fundamental elements, reveals itself to be made of the exact same mixture as the Earth. A common origin then, not an object formed elsewhere and captured by our gravity.
And we’re lucky to have that faithful companion. Day to day, the Moon doesn’t largely affect the Earth. It raises and lowers the tides in its month-long orbit, sharing the duty with the gravitational pull of the Sun itself. Some creatures, like dung beetles, use the polarized light of the Moon to guide their way back home after a night of collecting. But otherwise our satellite does nothing more than give us something beautiful to look it – there’s nothing quite like the cool blue light cast over freshly fallen snow in quiet winter nights.
But over the long haul, when we zoom our perspective out over billions of years, the Earth wouldn’t be the same without our sole friend. Our planet spins about its axis, but that spin is tilted with respect to the movement of the Earth in orbit around the Sun by 23 and a half degrees. This tilt gives us our seasons, with half our year spent with the northern pole facing the Sun, and the other half trading places with the southern pole.
Our planet could have had any orientation it wished. The other planets have lesser and greater tilts, with Uranus tipped completely over on its side and Venus rotating backwards. And there’s nothing to keep that tilt fixed over cosmic time. Our planet was born spinning, but the internal arrangements of its core, mantle, and crust, along with the ever-present gravitational machinations of Jupiter, can cause the Earth to wobble, shifting its tilt ever so slightly.
With every shift in the tilt, the seasons would radically change. Instead of regular, predictable changes year after year, we would experience ages with endless summers, or ages with violent but short winters, or anything in between. The rhythm of the seasons provides a pulse for life, which has the freedom to grow and evolve without trying to overcome great climactic shifts caused by a changing axis.
Luna acts as a great gravitational counterweight, stabilizing the motion of the Earth. By providing a source of gravity external to our planet, the Earth’s interior is free to shift and reconfigure as it pleases – the Moon steadies our hand and keeps us upright.
Astronomy 2024 features the final total solar eclipse for the CONUS until 2044, and much more.
It’s finally time. On April 8th, 2024, the umbral shadow of the Moon crosses the United States for the second time in less than seven years. It’s a big deal, for sure. But there’s lots more in store for astronomy 2024. Here’s our annualUniverse Today rundown for top skywatching events to watch for in astronomy 2024, coming to a sky near you.
Astronomy 2024: The Year in Brief
The turn of the calendar sees us just over three months out from the April 8th total solar eclipse across North America. Many late eclipse chasers are now presented with a choice: do I head towards the better prospects for clear skies in Mexico or Texas, or take my chances with the dicey springtime skies of the U.S. northeast or the Canadian Maritimes?
Top 12 Events: Astronomy 2024
Astronomy is always a paradox of knowns and unknowns. Eclipses and occultations are surefire bets in a clockwork Universe, while clear skies and whether the next touted ‘great comet’ or meteor outburst will perform are less certain. Here’s our quick rundown of the ‘best of the best’ skywatching events for 2024:
-The April 8th total solar eclipse across North America
-The Eta Aquariid meteor shower on May 6th, with a ZHR=50
-Mercury passes 7’ from Jupiter on June 4th
-The September 18th partial lunar eclipse for the Americas, Europe and Africa
-The October 2nd annular solar eclipse for the southern tip of South America
-The Moon occults Spica eight times and Antares fourteen times in 2024
-Solar activity ramps up ahead of the peak of Solar Cycle 25
-The Moon heads towards a Major Lunar Standstill in January 2025
-Comet C/2023 A3 Tsuchinshan-ATLAS may be bright towards the end of 2024
-A Leonid meteor outburst in November 2024?
Catching the total solar eclipse in 2017. Credit: Dave Dickinson
The Sun, Seasons and Solar Cycle in 2024
Expect the Sun to be busy in 2024 in terms of space weather and sunspots, as we head towards the peak of the solar cycle 25 in 2025. 2024 had an average sunspot number of around 120 and no spotless days, the first year since 2015 where this was the case. In fact, solar activity in 2023-2024 is climaxing well ahead of expectations, leading to a stronger than expected solar maximum in 2024. This means more sunspots, more wild space weather, and more aurorae for folks watching from mid- to high- northern latitudes.
The astronomical seasons for the northern hemisphere in 2024 kick off on:
Spring (northward) equinox: March 20th
Summer (northward) solstice: June 20th
Fall (southward) equinox: September 22nd
Winter (southward) solstice: December 21st
Of course, things are reversed south of the equator. Aurorae tend to pick up around the equinox due to a phenomenon known as the Russell-McPherron Effect and so does GEOSat flare season, as satellites way out in geosynchronous/geostationary orbit brighten into naked eye visibility, then wink out when they hit the Earth’s shadow.
The solstice tends to see spans where the International Space Station enters reaches full illumination, favoring the northern hemisphere in June and the southern hemisphere in December.
In 2024, the Earth reaches perihelion on January 2nd, and aphelion July 5th.
Transits through the field of view for the Solar Heliospheric Observatory (SOHO’s) LASCO C3 and C2 imagers for 2024. Credit: Worachate Bloonplod.
The Moon in 2024
The path of the Moon continues its trek towards the Major Lunar Standstill in early 2025, riding extra high versus the ecliptic and the horizon in the winter season, and low in the summer.
The Moon also reaches its closest perigee for 2024 on March 10th at 356,893 kilometers distant, and is at its farthest apogee on October 2nd at 406,516 kilometers distant.
We also have a ‘Black Moon’ on December 30th, with the second New Moon in a month with two. February 24th is the ‘Minimoon’ or smallest apparent Moon for the year, and October 17th is the Supermoon or largest Full Moon of 2024.
The Moon also occults (passes in front of) several bright stars and planets in its passage through the sky. The Moon occults Antares 14 times in 2024, and Spica 8 times:
Antares Events
(note: ‘+/- denotes waxing/waning phase for the Moon, along with the percent illuminated).
-January 8th for western North America (-11% Moon)
-February 5th for southeast Asia (-24% Moon)
-March 3rd for Central America (-51% Moon)
-March 30th for the central Pacific (-77% Moon)
-April 26th for the Middle East and east Africa (-93% Moon)
-May 24th for northern South America (-99% Moon)
-June 20th for the central Pacific (+70% Moon)
-July 17th for South Africa (+84% Moon)
-August 14th for the South Pacific (+70% Moon)
-September 10th for western Australia (+45% Moon)
-October 7th for the South Atlantic (+21% Moon)
-November 4th for the southeast Pacific (+10% Moon)
-December 1st for South Africa (+1% Moon)
-December 28th for the central Pacific (-6% Moon)
The Moon occults Spica on July 14th. Credit: Occult 4.1.2.
Spica Events:
-June 16th for Russia (+73% Moon)
-July 14th for North America (+58% Moon)
-August 10th for southeast Asia (+32% Moon)
-September 6th for East Africa (+12% Moon)
-October 3rd for Hawaii (in the daytime, +1% Moon)
-November 27th for North America (-12% Moon)
-December 24th for southeast Asia (-26% Moon)
The Moon occults Saturn on September 17th. Credit: Occult 4.1.2.
Planetary occultations: next, there are 15 lunar versus planetary occultations in 2024, involving 4 planets:
-Mercury (March 11th) by the +3% Moon, for the South Pacific
-Venus (April 7th) (daytime) by the -2% Moon, for eastern North America
-Venus (September 5th) by the +6% Moon for Antarctica
-Mars (May 5th) by the -8% Moon for Madagascar
-Mars (December 18th) by the ~87% Moon for the Arctic
Saturn Occultation Events:
-April 6th by the -7% Moon for Antarctica
-May 3rd by the -26% Moon for the southern Indian Ocean
-May 31st by the -39% Moon for southern South America
-June 27th by the -64% Moon for northern New Zealand
-July 24th by the -86% Moon for southeast Asia
-August 21st by the -95% Moon for northern South America and northwest Africa
-September 17th by the +99% Moon for western North America
-October 14th by the +89% Moon for India and eastern Africa
-November 11th by the +77% Moon for Central America
-December 8th by the +51% Moon for the western Pacific
The path of the April 8th total solar eclipse across North America. Credit: Michael Zeiler
Eclipses in 2024
Of course, the Great North American Eclipse on April 8th, 2024 dominates the year. But 2024 also features other eclipses as well spanning two eclipse seasons, including:
-March 25th: an 87% penumbral lunar eclipse, favoring the Americas.
-April 8th: A total solar eclipse, (maximum totality: 4 minutes and 28 seconds) spanning North America. This eclipse ‘could’ feature a rare treat, with (naked eye?) comet 12P/Pons-Brooks nearby, just 25 degrees east of the Sun.
-September 18th: A 9% partial lunar eclipse favoring the Americas, Europe and Africa.
-October 2nd: An annular eclipse with a maximum annularity of 7 minutes, 25 seconds favoring the southern tip of South America.
4 eclipses (2 lunar and 2 solar) is the minimum number that a calendar year can contain.
The path of the October 2nd, 2024 annular solar eclipse. NASA/GSFC/A.T. Sinclair
The Inner Planets in 2024
The two inner planets Mercury and Venus never stray far from the Sun. In early 2024 Venus lingers in the dawn, but does not reach greatest elongation in 2024. Instead, Venus reaches inferior conjunction on the solar farside opposite to the Earth on June 4th, transitioning from the dawn to the dusk sky.
Mercury reaches greatest elongation 7 times in 2024, an extra one versus its normal six:
-24 degrees west at dawn (January 12th)
-19 degrees east at dusk (March 24th)
-26 degrees west at dawn (May 9th)
-27 degrees east at dusk (July 22nd)
-18 degrees west at dawn (September 5th)
-23 degrees east at dusk (November 16th)
-22 degrees west at dawn (December 25th)
-Venus also occults the +6.4 magnitude star HIP 86060 for India on January 18th, and the +4.7 magnitude star HIP 92111 on (February 1st) for Brazil.
-Mercury meets M44 on July 6th (with asteroid 4 Vesta nearby!), 24 degrees from the Sun.
Venus meets M44 on July 18th, 11 degrees from the Sun.
The Outer Planets in 2024
Saturn’s ring angle in 2024 is 2 to 5 degrees wide, as they head towards edge on in March 23rd, 2024. Meanwhile, Jupiter’s outermost moon Callisto continues to ‘miss’ Jupiter, though that’ll change as the orbital plane of the Galilean moons head towards edge-on once again in 2026.
Saturn rings: from wide open, to approaching edge-on in 2024. Credit: Shahrin Ahmad.
Oppositions and the best season to observe the outer planets in 2024 include:
-Pluto (June 23rd)
-Saturn (September 8th)
-Neptune (September 21st)
-Uranus (November 17th)
-Jupiter (December 7th)
The top planet versus planet conjunction for 2024 is Mercury versus Jupiter on June 4th 7’ apart and 12 degrees west of the Sun at dawn.
Mercury meets Jupiter at dawn on June 4th. Credit: Stellarium.
The top bright star versus asteroid occultation for 2024 occurs on June 29th, when asteroid 2819 Ensor occults the +3.2 magnitude star Phi Sagittarii for north Asia.
The top star versus planet conjunction for 2024 is Mercury versus Regulus on September 9th 30’ apart, 17 degrees west of the Sun at dawn.
Astronomy 2024: Meteor Showers
There are 112 meteor showers known and recognized by the International Astronomical Union (IAU), about a dozen of which are major annual favorites. Of course, showers are always best when the pesky light-polluting Moon is near New and out of the way. In 2024, the best showers versus the Moon are:
-Eta Aquariids (May 6th) -1% Moon, ZHR~50
-Daytime Arietids (June 7th) +4% Moon ZHR~30
-Delta Aquariids (July 30th) -18% Moon ZHR~30
-Taurids (October 10th) +45% Moon ZHR~10
-Andromedids (December 10th) +5% Moon ZHR~20
Is a Leonid outburst due for November 14th 2024? The Earth may encounter the 1633 trail for source comet 55P/Tempel-Tuttle… the same stream that caused the 2001 outburst.
Comet 12P versus the bright star Vega. Credit: Dan Bartlett.
Comets to Watch For in 2024
We’re certainly due for the next great comet of the century. Though there’s nothing amazing to see in the sky in terms of comets (yet), that could all swiftly change with the discovery of a bright new comet inbound. As of writing this in late December 2023, these are the following comets expected to break binocular visibility:
-12P/Pons-Brooks reaches magnitude +3.9 at perihelion on April 21st in the constellation Taurus, 21 degrees east on the Sun.
-13P/Olbers reaches magnitude +7.5 at perihelion on July 1st in the constellation Lynx, 21 degrees east of the Sun.
-144P/Kushida reaches perihelion on January 26th at magnitude +7.9 in the constellation Taurus, 126 degrees east of the Sun.
-C/2021 S3 PanSTARRS reaches perihelion on February 15th at magnitude +7.4 in the constellation Pegasus, 23 degrees east of the Sun.
-Comet C/2023 A3 Tsuchinshan-ATLAS reaches perihelion on September 28th at magnitude +2.5 in the constellation Hercules, 83 degrees east of the Sun.
Comet Tsuchinshan-ATLAS at dawn in late September. Credit: Starry Night.
Weirdness and More:
Looking farther out afield, a few double stars on our ‘orbits with spans with short enough to live through’ reach maximum separation in 2023-2025:
-70 Ophiuchus reaches a maximum separation of 6.7”;
-Delta Equulei reaches a maximum separation of 0.3”; and
-The ‘Pup’ of the Dog Star Sirius B reaches its maximum apparent separation of 11.5 arc seconds on its 50-year orbit. True story: I ‘finally’ got to cross the Pup off my visual observing life list in 2023, courtesy of Richard Drumm and his access to the 26-inch refractor at the Charlottesville Virginia McCormick Observatory.
Also, 2050.00 celestial coordinates come into vogue in 2025 versus 2000.00, as we’ll officially be closer to 2050 than 2000… it’s strange to think, we’ve been using 2000.00 (and occasionally, 1950.00) for most of our lives.
Awaiting totality in 2017. Credit: Dave Dickinson.
Astronomy 2024…and a Teaser for 2025
…and as always, there’s more to come. 2025 sees the peak of Solar Cycle 25, the Moon at Major Lunar Standstill, Saturn’s rings edge on, Mars at opposition, two total lunar and two partial solar eclipses and more.
Don’t miss all of these events and more in Astronomy 2024!
