Jupiter’s clouds aren’t what we thought they were. Planetary atmosphere experts have studied them for many years, uncovering new and puzzling mysteries. Recently, several researchers banded together to solve a long-standing mystery about those clouds. It turns out they aren’t made of ammonia ice, which is what everyone has thought for years. Instead, they seem to be largely a mix of smog and ammonium hydrosulfide. That compound forms in the atmosphere as hydrogen sulfide gas passes through ammonia.
Most of us are familiar with the Jovian clouds and know that ammonia and water are involved in their formation. There’s precipitation, meaning that ammonia and other substances “rain out.” Then, they evaporate. Most of the clouds we do see are thought to be mainly ammonia ice, contaminated with other materials that lend color to the clouds. Ammonia is an important “tracer” of activity in Jupiter’s atmosphere and scientists have studied its presence for years. Most of those measurements come from spacecraft instruments and large ground-based telescopes outfitted with special filters and spectroscopes. Even those observations, however, are limited when it comes to determining their positions in the atmosphere. Also, temporal coverage is limited.
Getting observation time to track the presence of ammonia, and there are only so many spacecraft to go around. Plus, the methods for analyzing the observations are complex and time-consuming. What if there was a quick and cost-effective way to get continual observations of the Jovian clouds? Could smaller telescopes used by amateur astronomers be effective enough to chart variations in the amounts of ammonia in and above Jupiter’s clouds over time? If so, that would fill in a huge gap in Jupiter atmospheric observations.
Measuring Those CloudsThe saga of the Jovian clouds began when Dr. Steven Hill, a space weather forecasting expert, tried a fresh approach and made backyard observations of the gas giant’s clouds in 2020-2021 and 2022-2023. He was able to compare images that show absorption in the atmosphere due to ammonia and methane gases. He also determined variations in the amount of ammonia in and above the cloud tops.
With time on big observatory scopes at such a premium, Hill used a 0.28-meter Celestron Schmidt-Cassegrain telescope, outfitted with a ZWO ASI120MM CMOS camera. He used a 647-nm ammonia band filter first. Later on he applied a 619-nm methane band filter. The idea was to detect individual ammonia abundance features. “I always like to push my observations to see what physical measurements I can make with modest, commercial equipment,” said Hill. “The hope is that I can find new ways for amateurs to make useful contributions to professional work. But I certainly did not expect an outcome as productive as this project has been!”
Applying Hill’s Approach to Jupiter’s CloudsIt turns out Hill’s technique is easier and less expensive than the more complex observational and statistical methods scientists use to map clouds. It can be used in professional research to zero in on specific regions of the atmosphere. The approach also gives citizen scientists with backyard-type telescopes a way to track ammonia and cloud-top pressure variations across features in Jupiter’s atmosphere. That includes Jupiter’s cloud bands, its fast-moving small storms, and even the larger features such as the Great Red Spot.
Planetary atmosphere expert Professor Patrick Irwin at the University of Oxford in England, who co-wrote a paper with Hill about the observations, emphasized the advantage of doing such observations. “I am astonished that such a simple method is able to probe so deep in the atmosphere and demonstrate so clearly that the main clouds cannot be pure ammonia ice,” he said. “These results show that an innovative amateur using a modern camera and special filters can open a new window on Jupiter’s atmosphere and contribute to understanding the nature of Jupiter’s long-mysterious clouds and how the atmosphere circulates.”
Insights into Jupiter’s CloudsHill’s initial results showed that the clouds he studied lay in a region of Jupiter’s warm atmosphere that doesn’t allow ammonia ice to exist. In their follow-up study, Irwin and his colleagues applied Hill’s method to observations using the Multi Unit Spectroscopic Explorer on the Very Large Telescope in Chile. Doing spectroscopy allows scientists to measure the visible light fingerprints of the gases in the Jovian atmosphere and chart the distribution of ammonia and the height of its clouds. They also simulated how light interacts with those gases and clouds using a computer model.
Projected variations of ammonia abundance in Jupiter’s clouds, as well as cloud-top pressure near the Great Red Spot and the North Equatorial Dark features. These were made following Hill’s methodology. Courtesy Irwin, et al./JGR.
It turns out that the Jovian clouds observed through Hill’s backyard telescope had to be much deeper than previously thought. They lie in an atmospheric region with higher pressures and higher temperatures. That means the region is too warm to allow ammonia to condense. Chemical reactions created by sunlight’s effect on the gases are very active in Jupiter’s atmosphere. In small regions, where convection (heat transport from one region to another) is especially strong, the updrafts may be fast enough to form fresh ammonia ice. Such regions do exist and have been spotted by spacecraft over the years.
Irwin’s team suggests that when moist, ammonia-rich air gets raised upwards, ammonia gets destroyed. It could also be mixed with photochemical products faster than ammonia ice can form. That means the main cloud deck may actually be composed of ammonium hydrosulphide mixed with photochemical, smoggy products. That’s what produces the red and brown colors we see in Jupiter images. And, this method also works for observations of ammonia clouds in Saturn’s atmosphere. Further work should help determine if the same photochemical processes exist there.
For More InformationCitizen Science Reveals Insight into Jupiter
Clouds and Ammonia in the Atmospheres of Jupiter and Saturn Determined From a Band-Depth Analysis of VLT/MUSE Observations
Spatial Variations of Jovian Tropospheric Ammonia via Ground-Based Imaging
The post Jupiter’s Clouds Contain Smoggy Ammonium Hydrosulphide, Not Ammonia Ice appeared first on Universe Today.
There is a gravitational monster at the heart of our galaxy. Known as Sagittarius A*, it is a supermassive black hole with a mass of more than four million Suns. Long-term observations of the stars closely orbiting Sag A* place it at about 4.3 solar masses, give or take 100,000 or so. Observations of light near its horizon by the Event Horizon Telescope pin the mass down to 4.297 solar masses, give or take about 10,000. Those results are astoundingly precise given how difficult the mass is to measure, but suppose we could determine the mass of our galaxy’s black hole to within a single solar mass. That might be possible with gravitational wave astronomy.
Gravitational wave astronomy is still in its infancy. Presently, our gravitational wave observatories are only sensitive enough to detect the mergers of stellar-mass black holes and neutron stars within the Milky Way. We aren’t able to detect the mergers of supermassive black holes, nor the gravitational waves when a star is consumed by a supermassive black hole. But in the not-too-distant future, we will have space-based gravitational observatories such as LISA. They will be orders of magnitude more sensitive than what we currently have. And as a recent study shows, these new observatories should be sensitive enough to give us ultra-precise measurements of a black hole’s mass and rotation.
The idea behind this work is to focus on brown dwarfs. These objects straddle the mass range between planets and stars. Too large to be a planet, but too small to ignite core fusion like a star. Brown dwarfs have masses between 13 and 78 Jupiters and tend to be roughly the size of our Jovian neighbor. They aren’t quite as common as red dwarf stars, but should be fairly common within the center of our galaxy. That means some brown dwarfs should approach very close to Sag A*. Some of them will surely be gravitationally trapped by the black hole, slowly spiraling ever closer to its event horizon and oblivion. These are the ones the article focuses upon.
The gravitational chirp of a black hole merger. Credit: LIGOEven the largest brown dwarfs have less than a hundredth the mass of the Sun. They are like specks of dust compared to Sag A*. This means the gravitational dance between a brown dwarf and black hole is an example of an extremely large mass-ratio inspiral (XMRI). The gravitational waves produced by this dance would be small perturbations of the black hole, and as such would be critically dependent on the precise mass and spin of the black hole.
To show just how precise those measurements might be, the team looked at the estimated statistics for brown dwarfs near Sag A* as well as the strength of their gravitational signals. They found that within a typical range of mass and orbital eccentricity, an observatory such as LISA should be able to observe about 20 inspiraling brown dwarfs. This would allow us to determine the mass of Sag A* to better than one part in a million and its spin to one part in 10,000. Those estimates are at the best-case end of what is likely, but it shows that as gravitational wave astronomy improves, we are going to make some outstanding observations.
Reference: Vázquez-Aceves, Verónica, Yiren Lin, and Alejandro Torres-Orjuela. “SgrA* spin and mass estimates through the detection of multiple extremely large mass-ratio inspirals.” arXiv preprint arXiv:2412.20738 (2024).
The post Here's How We Could Measure the Mass of SgrA* to Within One Solar Mass appeared first on Universe Today.
Regulars at this site will surely know of Robert Lang, physicist and origami master (art website here) whom I met a while back at the Kent Presents meetings. We became friendly and thereafter he contributed both wildlife photos and origami photos to this website (see all his posts here).
I was scheduled to meet Robert and his wife Diane today after the meetings and get a tour of their home and studio (she’s an author), thereafter then sallying forth to dinner. I hadn’t seen Robert in years, and had never met Diane, so I was looking forward to visiting their digs and to seeing some of the famous origami.
The problem was that their home and studio were in Altadena, California, near Los Angeles, so you can guess what I’m going to say next.
The home and studio are no more, taken down by wildfire. But I’ll let Robert tell the tale. His words, printed with permission, are indented below, and are supplemented with narrated videos (there are even subtitles). This is the story of a family who lived through the fire but lost everything—except for the most important things: their lives and their animals.
Note that they actually lost two houses, as they had just bought another down the street.
Late Tuesday afternoon, we heard about the Eaton Fire, which started over in Eaton Canyon, about 2 miles to our east and several ridges over. The initial reports were that the wind was driving the fire to the east (away from us), so we were hopeful. At about 6:30 pm, though, my neighbor texted the neighborhood group that he saw a glow over the ridge to our east, and I headed up to my studio to see. By 7:30 pm I saw the fire crest that ridge and we received the “evacuate NOW” notice, so I threw as much as I could grab into my car and headed down, while my wife did the same from our home (with the dogs, tortoises, snake, and tarantula that live with us).
We spent the next few hours driving and parking to try to watch things from a distance. Surprisingly, the evacuation zone ended just to the west of our neighborhood, so after a while, I started making my way to the edge of the zone, staying out of the way of the many emergency vehicles, and presently found a spot from which I could walk to the edge of the canyon that separated me from my studio. From there, I could see the studio; I could also see that the entire multi-thousand-foot mountainside above it was in sheets of flame. The wind was blasting through the canyons, driving 50-foot plumes of flame and embers horizontally. About 1:30 am, I saw a flare-up right at the studio, and within about 10 minutes, it was engulfed. I also realized about that time that the fire would likely take down the telephone poles (and thus, potentially live wires) along my route, so I beat a hasty retreat to my car, and before long, the authorities announced that our area was now evacuation zone. We drove down the hill to Pasadena, found a quiet neighborhood out of the smoke (and, we hoped, the path of the fire), and spent a fitful rest of the night in our cars, awaiting what the morning would bring.
In the morning, my wife stayed with the animals and I drove up the hill to see what became of our house. Major roads were blocked off, but I wove through the neighborhoods, dodging still-burning homes (though the worst was past), downed wires, downed trees, and random debris, until I could get up to my neighborhood. It was a zone of total devastation: nearly all homes burned–and definitely mine. (Actually, both of ours; we had just moved down the street, so both our old house–just moved out of–and the new house–just moved into–were leveled.) I made my way up to my studio at the top of the hill, passing street after street of nothing but smoldering ruins. When I made it up, I found something incredible: the row of houses below my studio had entirely survived! I texted their owners the good news. I could see, though, that my studio had not; I parked (debris blocked my driveway), walked up, and surveyed the destruction, took a few videos and pictures for records, then high-tailed it down the hill.
Right now, the estimates are that 7000 structures were damaged or destroyed. It looks like about 2/3 of Altadena is gone. There’s a lot of snark on the internets about the rich people/celebrities/influencers in Pacific Palisades losing their houses. I haven’t seen similar snark about Altadena, which is a mixed-class, mixed-race community. There are turn-of-the-century buildings, craftsman houses, bungalows, tiny starter homes, and yes, a few mansions left over from the days when it was the summer playground of the rich. My wife grew up here; her father built their house himself in the 40s after clearing the orange groves from the parcel he bought. On the main drag downtown, the local hardware store was where you ran into your neighbors; Fox’s Restaurant had been a local landmark since 1955. All that is gone.
Ironically, I had recently returned from a business trip to Dresden, Germany, which was (famously) fire-bombed and leveled in WWII. They rebuilt. So will we. But it will be a long road to recovery.
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Here a Cal Fire map of fire damage. The damaged area covers about 2/3 of Altadena. My home and studio is in the top middle of the burned civilized area, just to the left of the vertical black bar on the map.
This map is an understatement; I know some of the areas shown in gray actually burned.
Here are a few of the videos Robert posted on his YouTube site:
Panorama of the fire from the studio:
View of the mountains from the house:
Views of the destroyed house:
Views of the destroyed studio:
From Robert:
Here’s one more image for you: house-by-house fire damage. I’ve annotated where my places were. Not much left of the neighborhood.
[The key to above]: red=burned, black = OK, amber=damaged, green=“affected” (whatever that means).
Distance-wise, the studio and the houses are about a half mile apart by road, less by walking (there’s a trail up the canyon). An easy walk, except for the elevation gain (studio is about 200’ higher in elevation), so I usually drove.Click to enlarge: Arrows: studio is at the top, the old house at lower center, and the new house at lower right. I’m struck by the patchy locations of the houses that survived.
As you can tell from the narration, Robert appears remarkably calm about this, as he was in his email to me about the destruction, which was headed “change of plans.” I would be wailing with grief! But Robert and I do have one thing in common: a compulsion to document. His is with words and videos, mine involves in putting them on this site.
Best of luck, Robert and Diane, and of course we’re all sorry for your loss.
Meanwhile, in Dobrzyn, Hili is the boss cat, of course:
A: Hili, you are not helping me when you lie here.
Hili: I’m supervising. Find somebody else to help you.
Ja: Hili, nie pomagasz mi jak tu leżysz.
Hili: Ja nadzoruję, do pomagania znajdź sobie innych.