This image shows Neptune observed with the MUSE instrument at ESO’s Very Large Telescope. At each pixel within Neptune, MUSE splits the incoming light into its constituent colors or wavelengths. This is similar to obtaining images at thousands of different wavelengths all at once, which provides a wealth of valuable information to astronomers. This image combines all colors captured by MUSE into a “natural” view of Neptune, where a dark spot can be seen to the upper-right. Credit: ESO/P. Irwin et al.
Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers have observed a large dark spot in Neptune’s atmosphere, with an unexpected smaller bright spot adjacent to it. This is the first time a dark spot on the planet has ever been observed with a telescope on Earth. These occasional features in the blue background of Neptune’s atmosphere are a mystery to astronomers, and the new results provide further clues as to their nature and origin.
Large spots are common features in the atmospheres of giant planets, the most famous being Jupiter’s Great Red Spot. On Neptune, a dark spot was first discovered by NASA’s Voyager 2 in 1989, before disappearing a few years later. “Since the first discovery of a dark spot, I’ve always wondered what these short-lived and elusive dark features are,” says Patrick Irwin, Professor at the University of Oxford in the UK and lead investigator of the study published today in Nature Astronomy.
Irwin and his team used data from ESO’s VLT to rule out the possibility that dark spots are caused by a ‘clearing’ in the clouds. The new observations indicate instead that dark spots are likely the result of air particles darkening in a layer below the main visible haze layer, as ices and hazes mix in Neptune’s atmosphere.
Coming to this conclusion was no easy feat because dark spots are not permanent features of Neptune’s atmosphere and astronomers had never before been able to study them in sufficient detail. The opportunity came after the NASA/ESA Hubble Space Telescope discovered several dark spots in Neptune’s atmosphere, including one in the planet’s northern hemisphere first noticed in 2018. Irwin and his team immediately got to work studying it from the ground — with an instrument that is ideally suited to these challenging observations.
Using the VLT’s Multi Unit Spectroscopic Explorer (MUSE), the researchers were able to split reflected sunlight from Neptune and its spot into its component colors, or wavelengths, and obtain a 3D spectrum [1]. This meant they could study the spot in more detail than was possible before. “I’m absolutely thrilled to have been able to not only make the first detection of a dark spot from the ground, but also record for the very first time a reflection spectrum of such a feature,” says Irwin.
Since different wavelengths probe different depths in Neptune’s atmosphere, having a spectrum enabled astronomers to better determine the height at which the dark spot sits in the planet’s atmosphere. The spectrum also provided information on the chemical composition of the different layers of the atmosphere, which gave the team clues as to why the spot appeared dark.
The observations also offered up a surprise result. “In the process we discovered a rare deep bright cloud type that had never been identified before, even from space,” says study co-author Michael Wong, a researcher at the University of California, Berkeley, USA. This rare cloud type appeared as a bright spot right beside the larger main dark spot, the VLT data showing that the new ‘deep bright cloud’ was at the same level in the atmosphere as the main dark spot. This means it is a completely new type of feature compared to the small “companion” clouds of high-altitude methane ice that have been previously observed.
With the help of ESO’s VLT, it is now possible for astronomers to study features like these spots from Earth. “This is an astounding increase in humanity’s ability to observe the cosmos. At first, we could only detect these spots by sending a spacecraft there, like Voyager. Then we gained the ability to make them out remotely with Hubble. Finally, technology has advanced to enable this from the ground,” concludes Wong, before adding, jokingly: “This could put me out of work as a Hubble observer!”
We Saw It! The skies, recovered to blue and sunshine from overnight rain and clouds giving us hope and a spring in our step. As the hour of eclipse approached, so did a generally thin milky layer of clouds. The eclipse was not spoiled, however, and we enjoyed a wonderful view. We sincerely hope you were able to experience the “2024 Great American Eclipse” as well.
The Sun during totality, exposed to show prominences looping from the solar surface. Prominences were seen in several locations along the limb but the one seen here, near the bottom of the disk, was easily seen with the unaided eye. Photo by James Guilford.
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Eclipse Watching in Medina, Ohio
April skies are notoriously changeable here in Northeast Ohio where we are otherwise in an excellent location for viewing the April 8, 2024 total solar eclipse. In fact, the chances of a clear sky here are only about 37 percent. Ugh! Dedicated eclipse chasers will mostly head to the southwestern U.S. for better chances at clear skies. For those of us not traveling, let’s hope for clear skies here on the Big Day because a total solar eclipse is more than just an awesome sight, it’s an experience! Let’s be prepared.
An Updated List of Resources Appears Near The End of This Article
Time and Eclipses Wait for No One
Moon’s shadow will be clipping across Ohio at about 2,100 miles per hour, so the peak period of the eclipse — totality — is fleeting. Medina will experience about 3 minutes and 28 seconds of totality, which is pretty good. If we were in the central line of the path of totality, which passes right through Lorain, we would have 3 minutes and 53 seconds of glorious viewing. Here, courtesy of the U.S. Naval Observatory, are local times for critical points of the eclipse:
Timing in Medina, Ohio (Eastern Daylight Time)
Partial Eclipse Begins — 1:58:38
Totality Begins — 3:13:23
Maximum Eclipse — 3:15:06
Totality Ends — 3:15:51
Partial Eclipse Ends — 4:28:38
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Sights and Experiences
The eclipse will begin when Moon starts its passage across the solar disk. When viewed through protective filters, a tiny nick will be missing from Sun’s limb. That nick will gradually grow as the partial eclipse phase progresses. Viewed through “eclipse glasses” or other specialty solar filters, Sun will transition from a full disk to, eventually, a slim crescent. Our surroundings will not become dark as night but the light will take on an eerie softness as Sun fades. If, heaven forbid, skies are cloudy, it will be very dark in the path of totality … very dark indeed.
Sunspots may be visible. Dark markings of various sizes and shapes may be seen on the solar disk during the partial phases of the eclipse. Sun is in the most active phase of its regular cycle during which sunspots are common. If they are large enough, sunspots can be seen using eclipse glasses but are best observed through telescopes equipped with solar filters.
The air may feel cooler, birds and other animals may begin evening behaviors. Street lights and other automatic lighting may activate.
Just before totality begins, two interesting effects will be seen, caused by Moon: Baily’s beads are dots of sunlight that will dance along the edge of the blackened moon. The diamond ring effect is a singular burst of sunlight that, combined with the light ring of the now-eclipsed sun, is reminiscent of a shining diamond. Both effects are caused by sunlight shining through the mountainous terrain on Moon’s horizon as it moves into position in front of Sun.
Look around as these things are happening, and watch for shadow bands — dim waves of dark and light that will ripple across the ground immediately before and after totality. The bands are a memorable experience but often missed because most attention will be on the sky above!
During totality — and only during totality — eclipse glasses and solar filters are not needed. In fact, the eclipse will be too dim to be seen through the protective devices. Looking around where they are standing, watchers will notice that it is not as dark as night but something odd is to be seen. Overhead, where the brilliant afternoon sun should be shining, it’s dark but for the glorious total eclipse. Along the distant horizon, there is sunlight — it’s coming from areas outside of Moon’s shadow, away from the path of totality.
Marvel at Sun’s corona as it radiates from the dark circle of moon-covered-sun. It’s a sight not soon forgotten! During totality look for a star-like light to the southwest of the eclipse — it’s planet Venus! To the upper left of Sun’s position is planet Jupiter.
The interesting effects and partial eclipse phases will take place in reverse order as totality ends. Put those eclipse glasses and filters back on immediately — even the crescent Sun is powerful enough to damage unprotected eyes — and don’t forget to turn unprotected cameras away from Sun!
So What’s Happening?
A total solar eclipse occurs when Moon passes between Sun and Earth, causing Moon’s shadow to be cast on Earth’s surface. Moon is at the right distance from Earth that, when it does pass in front of Sun, the fit is nearly perfect, blocking direct sunlight from reaching the surface within its shadow. An annular eclipse happens when Moon’s orbit carries it a bit too far from Earth to cover the solar disk, producing a “ring of fire” — sunlight in a halo around the dark Moon. Most of the time, Moon’s orbit carries it into positions where its shadow “misses” Earth, so there’s no eclipse.
When the moon passes directly between the sun and Earth, a solar eclipse takes place. (NEVER look at the sun during any type of solar eclipse! Looking at the sun is dangerous. It can damage your eyes.) Image Credit: NASA
As mentioned earlier, when totality is reached, Sun’s brilliant light is completely blocked as viewed from within Moon’s shadow. That shielding from brilliant sunlight allows the solar corona to be seen. The corona is a hazy glow surrounding the darkened Sun and is the outermost region of the Sun’s atmosphere, consisting of plasma (hot ionized gas). The corona continually varies in size and shape as it is affected by the Sun’s magnetic field so its appearance differs eclipse-to-eclipse and is of great interest to those who study our nearest star — it also makes totality a unique and awe-inspiring sight.
Eclipse Viewing Safety
Don’t risk your vision! Even when Sun is “mostly” covered by Moon before and after the total eclipse, sunlight will be strong enough to cause permanent eye damage. Sunglasses and other makeshift items are not enough. To look at the sun, use only certified “eclipse glasses” — filters — so you can safely view Sun before and after totality. Here’s a link to sources: https://eclipse.aas.org/eye-safety/viewers-filters — More Information Below
Medina, Ohio Area Resources
Branches of Medina County (Ohio) District Library were distributing eclipse glasses free of charge, one per family, as supplies allow, at the time of this writing. Glasses are easy to share amongst family members, looking one at a time at the partly-eclipsed sun. In fact, it is best for adults to watch children who are using eclipse glasses to make certain they’re wearing them correctly and that can’t be done if the adult is wearing eclipse glasses at the same time — they’re too dark!Library Eclipse Programs
The Medina County Fair Board will be renting out Solar Eclipse Camping sites for campers and motorhomes beginning Friday April 5 thru Tuesday April 9. There will be electric hook-up and restrooms and showers on site. Call (330) 723-9633 or email medinafair@gmail.com to reserve a space. Looking for a place to just park your vehicle to watch the eclipse? You can rent a parking spot for $20 (cash only) at the Community Center parking lot.
Useful Mobile Apps via the AAS
Here you’ll find some of the best eclipse-related apps and software available, as judged by members of the American Astronomical Society (AAS) Solar Eclipse Task Force: https://eclipse.aas.org/resources/apps-software
Solar Eclipse Timer App
Want more precision and audio/voice prompts at critical points of the event? Then this app’s for you! (Included in the AAS list) There are versions for iOS and Android and a small charge to update to the 2024 version ($1.99 for iOS) but it’s worth it if you want a sophisticated digital assistant — be sure and install and update in advance for your observing location! https://www.solareclipsetimer.com/
A Word About “Eclipse Glasses“
Purchase and use only ISO filters and eclipse glasses certified for direct viewing of the sun. This is your vision, and that of your loved ones, we’re talking about here! Sunglasses, smoked glass, Compact Discs, photographic negatives, and other items are not safe for looking directly at Sun! Safe, inexpensive eclipse glasses and filter cards are widely available for this eclipse so should be bought in advance and stored safely away. Read and follow instructions that should be printed on eclipse glass frames. Check the “lenses” for damage such as tears or pinholes and throw the glasses away if any defects are found. The glasses can be kept and used after the event but should be examined before use every time. Remember, too, these often colorfully-framed eclipse glasses may be appealing to children BUT THEY ARE NOT TOYS — they are all that stand between the user and permanent eye damage so do not allow kids to play with them. For more on this subject, see:https://eclipse.aas.org/eye-safety/iso-certification
If you’re using old eclipse glasses, make sure the lenses aren’t scratched or damaged. Check out this video from NASA on how to make sure your glasses are good to go: youtube.com/
A Sirius 7.5-foot observatory configured in the same way as our on-order structure. The base, however, is expected to be much larger. Photo via the manufactuerer
We started the month of August out by {finally} placing our order for a Sirius 7.5-foot observatory. The fiberglass structure will arrive in kit form, to be assembled on-site. We should be able to do most of the work ourselves but may need to hire muscle to lift the dome into place! In the meantime, I’m looking to contract with a landscaper to prepare the build site. We’ve something unique in mind — a hardscape patio, of sorts, that will form a base for the observatory. If and when the observatory eventually needs to be removed, the remaining base will be a paver-style patio with the telescope’s pier foundation serving as mounting point for a fire feature or table! We think it’s pretty clever. We also think it will be expensive. We’ll see what we can actually do!
An electrician works on the conduit run from the house to the shed. The metal conduit runs through a trench dug for that purpose.
UPDATE: On July 31 we received the approved Building Permit which gives us the go-ahead on the project. The observatory kit — it’s delivered as a ready-to-assemble set of parts — will be ordered ASAP. The purchase had to wait until the permit was issued since the purchase price is not refundable and what would have happened if the city said no???
Last week we had professional electricians run power to the shed where a warm room / control room will be set up for the observatory. For burial of the metal conduit, they dug a much wider trench than I expected and I’ll be cleaning up the earthen scar this coming week. I’ll be framing out a space within the shed for the actual control room which will be wired for electrical service.
The Building Permit Application was filed with the city last Friday — surely unique in the history of this town — so we’ll see how it goes! If the permit is approved, we’ll launch into acquisition of the observatory and preparation of the site for the structure. If the permit is denied, I’ll probably set up an open-air pier for the telescopes and run them from the control room. I expect they’ll approve it — you ought to see what people put in their back yards!
The conduit, before burial, and the shed. The end of the building with the window will be partitioned for use as the warm room / control room. The solar panel on the rooftop currently supplies weather station equipment and is, surprisingly, barely adequate to the task.
I hauled out the 1970s vintage Celestron C90 telephoto lens this morning, attached my AstroZap Baader film solar filter, and my Canon EOS 7D to quickly image Sun. I’m hoping to be able to use the compact mirror lens for quick shots such as this and for images of the Moon; trials have thus far met with mixed results. It’s a cool old lens but not as good as other gear in my current collection. The setup was mounted on a simple photographic tripod and, astro-folk will note, Sun’s orientation here is cockeyed. Once the observatory is set up and a mounted telescope put into use, we expect to see improved resolution/magnification, and won’t have to struggle with gear too heavy for the tripod! There’s a smattering of sunspots to be seen in this image along with a few other, more subtle features in the solar photosphere. Clouds rolled in soon after this image was made.
Stella-Luna Observatory 