Category: astronomy

Readers’ wildlife photos

July 2, 2026 • 8:30 am

Send in your photos if you got ’em, please!

Today’s photos continue the series taken by reader Ephraim Heller in Namibia. His captions and IDs are indented, and you can enlarge the photos by clicking on them.

Today I continue my series on a May-June 2026 visit to Namibia. I’m organizing the posts by habitat, in the order of our visits, so that you get a sense of the ecosystems. Today’s post features Damaraland, a 48,000 km² region in the northwest of the country.

Damaraland is not a formal administrative region, but a geographic and cultural designation. It is a jumble of granite kopjes, basalt plateaus, flat-topped mountains, broad gravel plains, and eroded canyon systems. Like much of Namibia, it is desert. Here is an aerial view, taken from the window of a small airplane:

Life is sparse here. A handful of ephemeral rivers cross Damaraland, cutting westward from the interior highlands to the Skeleton Coast along the Atlantic Ocean. These rivers flow above ground for only a few days per year following significant inland rainfall, but each bed sits atop an alluvial aquifer that retains water from flood events for months to years. This subsurface water sustains a few trees, shrubs, and animals along the riverbeds. Here’s another aerial view showing the path of an ephemeral river:

By far the coolest critter I found was the longleg armoured corncricket (Acanthoplus longipes), which has superpowers. It is a large, flightless katydid brandishing big, spiny legs and a heavily armored (American spelling) pronotum. When attacked, individuals autohaemorrhage, shooting a jet of toxic hemolymph from the leg joints toward attackers. I wish I had a superpower like that:

Naturally, any creature with such a magnificent superpower fluoresces under UV light:

Frankly, the rest of this post is anticlimactic. What could possibly beat a longleg armoured corncricket? Not a pretty brush jewel beetle (Julodis humeralis):

A Namib rock agama (Agama planiceps) doesn’t beat a longleg armoured corncricket, not even when it is chowing down on a bug:

One night I went on a walk to see what would fluoresce under my UV light. I found this gecko. Sure, fluorescence is cool and I wish I could do it, but does this gecko autohaemorrhage? No, it does not. The folks at iNaturalist couldn’t identify it – apparently one needs the visible spectrum to make a positive ID:

This is tentatively identified as an orange lesser-thicktail scorpion (Uroplectes planimanus), another critter with the minor UV-fluorescence superpower. Interestingly, researchers do not know why scorpions evolved fluorescence.

Now for the birds. Sadly, they have no superpowers at all. Our lodge had a water feature that was the only surface water for miles around. I spent hours watching the birds bathe and drink.

A violet-backed starling (Cinnyricinclus leucogaster). The color is produced not by pigment but by thin-film interference: stacks of hollow melanosomes in the feather barbules refract light at specific wavelengths. The male can modulate its apparent coloration through posture:

A black-fronted bulbul (Pycnonotus nigricans):

A Namaqua dove (Oena capensis):

A red-headed finch (Amadina erythrocephala):

The southern masked weaver (Ploceus velatus). Egg color varies among females, allegedly as a defense against brood parasitism by the Diederik cuckoo. Because the cuckoo cannot know egg color before entering the nest, color polymorphism in the weaver population raises the probability of parasite detection and egg ejection. Not a superpower, but cool nonetheless. I just like the bokeh in this photo:

Finally, the requisite Namibian desert night sky photos:

Reader’s wildlife photos

June 23, 2026 • 8:15 am

Why is this feature like lox and a schmear? A: Because it’s on a roll. (Sort of.) I now have a total of four sets of photos in the queue, one of which I’ll post today. But please send your good photos, and a warm handshake to those who have done so.  I hope people realize that readers who send in good add a unique feature for this website: high-quality and delightful pictures of nature. Do compliment the photographer if you like their photos.

Today we have pictures from Ephraim Heller, documenting his recent trip to Namibia. (More will be coming.) Ephraim’s captions are indented, and you can enlarge his photos by clicking on them.

Today I begin a series on a May-June 2026 visit to Namibia. I’m organizing the posts by habitat, in the order of our visits, so that you get a sense of the ecosystems.

The Namib Desert is the oldest desert on earth, with conditions that have persisted for 55 – 80 million years. At ~80,950 square km (31,250 sq mi), it is far and away the largest desert I have visited. It stretches ~2,000 km (1,200 mi) along southwest Africa’s Atlantic coast, including the entire length of Namibia. There is essentially no rain at all near the coast (2 mm/year average), but in places there is coastal fog that is the primary source of water for the desert plants. The stable climate over millions of years has resulted in high endemism. Of the ~3,500 documented species in the Namib, more than 1,000 are endemics.1-2. On the drive from the capital, Windhoek, visitors pass through Solitaire. It consists of a fuel station, a bakery and café, a general store, a small lodge, and a yard decorated with old vehicles. The nearest real town is hundreds of kilometers distant. When vehicles broke down, cars and trucks were simply left. Some of the collection includes American classics from the mid-twentieth century:

While having lunch at a picnic table in Solitaire, I observed several yellow mongooses (Cynictis penicillata) playing. Technically, Solitaire is semi-desert, so there are a few shrubs for the mongoose. They often share burrow systems with the local ground squirrels (Xerus inauris), which confused me as I tried to decide if I was seeing mongooses or ground squirrels. This is a mongoose:

Our destination in the Namib desert was Sossusvlei, where the sand dunes are among the highest in the world. “Dune 7” dune, the tallest, is 388 m (1,273 ft) in height. Vlei is the Afrikaans word for “marsh,” while sossus is Nama for “no return” or “dead end”.  The area is the drainage basin for the ephemeral Tsauchab river. The Namib Sand Sea, of which the Sossusvlei dune field is a part, is a UNESCO World Heritage Site. The dunes began forming around five million years ago. Sand from the Orange River was carried west into the Atlantic, swept north by the Benguela Current, then driven back inland by the prevailing south-southwest winds. Over millions of years the sand accumulated into a dune field ~32,000 sq km (12,400 sq mi) in extent. The sand is iron-oxide coated quartz, and younger sand near the base of dunes is paler while older sand higher up is a deeper reddish-orange, due to greater oxidation. The colors in these photos are real, and not simply me going wild with the saturation slider in my photo editing software. For scale, note the full-grown trees at the base of the dune in the first photo.

About a kilometer walk across the sand lies a small clay pan named Deadvlei (meaning “dead marsh”) where reside camelthorn trees (Vachellia erioloba) that have been dead for 600 – 900 years. There has been no water here since the fourteenth century! The combination of extreme dryness and intense heat inhibits microbial activity so thoroughly that the wood is preserved.

Gemsbok (Oryx gazella) and springbok (Antidorcas marsupialis) antelope are the primary large mammals of the Namib. Gemsbok can survive for extended periods without drinking free-standing water, meeting their requirements through vegetation. Here is a gemsbok in its habitat:

Here is a herd of springbok in their environment:

Toktokkie beetles (Onymacris unguicularis) are a group of darkling beetles with over 200 species in Namibia, and 20 in the Namib desert. We saw them throughout Namibia. I don’t know the species of this individual, but some species engage in fog-harvesting: when Atlantic fog rolls in, beetles climb to the crests of dunes and orient head-downward, body inclined away from the wind. Water condenses on the elytra, runs along ridges on the beetle’s back, and reaches the mouthparts. A beetle can take in water equivalent to ~40% of its body mass from a single fog event.

The garden locust or tree locust (Acanthacris ruficornis), is widespread across sub-Saharan Africa. Tt is technically a grasshopper:

Namaqua doves (Oena capensis) are ubiquitous, but I think they are pretty. They are the smallest doves on the African continent:

The Kalahari tree skink (Trachylepis spilogaster). I had no idea that some skinks are arboreal:

The extreme dryness and very low population density of Namibia make it one of the prime sites for astronomical observatories and night sky photographers:

Readers’ wildlife photos

August 26, 2025 • 8:25 am

Today’s photos come from Wyoming and photographer Ephraim Heller. His IDs and captions are indented, and you can enlarge his photo by clicking on them:

My wife and I just returned from a few days of horseback riding and relaxation at a dude ranch near Dubois, Wyoming (pronounced “Du-boiz” with the accent on the first syllable) in the Absaroka Mountains. Dubois’ 82513 ZIP Code includes 1,537 square miles and has a total population of 1,549: a population density of about 1 person per square mile, making it ideal for astrophotography. Butch Cassidy (Robert LeRoy Parker) owned and managed a ranch on the outskirts of Dubois, beginning in 1890.

The Dollar Lake fire began during our stay. First reported on Thursday, August 21 the fire had expanded to 8,660 acres with 0% contained by the following day. The fire grew rapidly due to extremely dry conditions, a heavy load of fuel, and high winds. The forests in this area have a particularly high fuel load due to large stands of beetle-killed lodgepole pines.

Here’s the view south from the ranch toward the galactic center of the Milky Way on the night of Tuesday, August 19:

Here’s the view south from a nearby spot on the night on Friday, August 22:

And here are a few photos of our companions at the ranch, Equus ferus caballus. This one-eyed fellow was very friendly:

Other miscellaneous photos:

Guest post: does atmospheric chemistry suggest there’s life on another planet?

May 30, 2025 • 10:00 am

Today we have a guest post from reader Coel Hellier, who does this kind of stuff for a living. His text deals with the recent kerfuffle about whether a nearby planet shows an atmospheric gas indicative of life.  I particularly like the details about how scientists go about analyzing a question like this. His text is indented, and he’s added the illustrations.

Is the dimethyl sulphide in the atmosphere of exoplanet K2-18b real?

Everyone is interested in whether there is life on other planets. Thus the recent claim of a detection of a biomarker molecule in the atmosphere of an exoplanet has attracted both widespread attention and some skepticism from other scientists.

The claim is that planet K2-18b, 124 light years from Earth, shows evidence of dimethyl sulfide (DMS), a molecule that on Earth arises from biological activity. Below is an account of the claim; I try to include more science than the does mainstream media, but do so largely with pictures in the hope that the non-expert can follow the argument.

Transiting exoplanets such as K2-18b are discovered owing to the periodic dips they cause in the light of the host star:

And here is the lightcurve of K2-18b, as observed by the James Webb Space Telescope, showing the transit that led to the claim of DMS by Madhusudhan et al.:

If we know the size of the star (deduced from knowing the type of star from its spectrum), the fraction of light that is blocked then tells you the size of the planet.

But we also need to know its mass. One gets that from measuring how much the host star is tugged around by the planet’s gravity, and that is obtained from the Doppler shift of the star’s light.

The black wiggly line in the plot below is the periodic motion of the star caused by the orbiting planet. Quantifying this is made harder by lots of additional variation in the measurements (blue points with error bars), which is the result of magnetic activity on the star (“star spots”). But nevertheless, if one phases all the data on the planet’s orbital period (lower panel), then one can measure the planet’s mass (plot by Ryan Cloutier et al):

So now we have the mass and the size of the planet (and we also know its surface temperature since we know how far it is from its star, and thus how much heating it gets).  Combining that with some understanding of proto-planetary disks and planet formation. we can thus dervise models of the internal composition and structure of the planet.

The problem is that multiple different internal structures can add up to the same overall mass and radius. One has flexibility to invoke a heavy core (iron, nickel), a rocky mantle (silicates), perhaps a layer of ice (methane?), perhaps a liquid ocean (water?), and also an atmosphere.

This “degeneracy” is why Nikku Madhusudhan can argue that K2-18b is a “hycean” planet (hydrogen atmosphere over a liquid-water ocean) while others argue that it is instead a mini-Neptune, or that it has an ocean of molten magma.

But one can hope to get more information from the detection of molecules in the planet’s atmosphere, a task that is one of the main design goals of the James Webb Space Telescope [JWST]. The basic idea is straightforward: During transit, some of the starlight will shine through the thin smear of atmosphere surrounding the planet, and the different molecules absorb different wavelengths of light in a pattern characteristic of that molecule (figure by ESA):

So one observes the star both during the transit and out of transit, and then subtracts the two, and the result is a spectrum of the planet’s atmosphere.

If the planet is a large gas giant with a fluffy, extended atmosphere and is orbiting a bright star (so that a lot of photons pass through the atmosphere), the results can be readily convincing. For example, here is a spectrum of exoplanet WASP-39b with features from different molecules labelled (figure by Tonmoy Deka et al):

[I include a plot of WASP-39b partly because I was part of the discovery team for the Wide Angle Search for Planets survey, but also because it is pretty amazing that we can now obtain a spectrum like that of the atmosphere of an exoplanet that is 700 light-years away, even while the planet itself is so small and dim and distant that we cannot even see it.]

The problem with K2-18b is that the star is vastly fainter and the planet much smaller than WASP-39b. This is at the limit of what even the $10-billion JWST can do.

When you’re subtracting two very-similar spectra (the in- and out-of-transit spectra)  to look for a rather small signal, any “instrumental systematics” matter a lot. Here is the same spectrum of K2-18b, as processed by several different “data reduction pipelines”, and as you can see the differences between them (effectively, the limits of how well we understand the data processing) are similar in size to the signal (plot by Rafael Luque et al):

The next problem is that there are a lot of different molecules that one could potentially invoke (with the constraint of making the atmospheric chemistry self-consistent). For example, here are the expected spectral features from eight different possible molecules (figure by Madhusudhan):

To finally get to the point, I show is the crucial figure below. Nikku Madhusudhan and colleagues argue — based on an understanding of planet formation, and on arguments that planets like K2-18b are hycean worlds [with a liquid water ocean under a hydrogen-rich atmosphere], and from considerations of atmospheric chemistry, in addition to careful processing and modelling of the spectrum itself — that the JWST spectrum of K2-18b is best interpreted as follows (the blue line is the model, the red error bars are the data):

This interpretation involves large contributions from DMS (dimethyl sulphide) and also DMDS (dimethyl disulphide) — the plot below shows the different contributions separated — and if so that would be notable, since on Earth those compounds are products of biological activity—mainly from algae.

In contrast, Jake Taylor analysed the same spectrum and argues that he can fit it adequately with a straight line, and that the spectral features are not statistically significant. Others point out that the fitted model contains roughly as many free parameters as data points. Meanwhile, a team led by Rafael Luque reports that they can fit the spectrum without invoking DMS or DMDS, and suggest that observations of another 25 transits of K2-18b would be needed to properly settle the matter.

There are several distinct questions here: Are the details of the data processing sufficiently understood? (perhaps, but not certainly); are the relevant spectral features statistically significant? (that’s borderline);  and, if the features are indeed real, are they properly interpreted as DMS? (theorists can usually think of alternative possibilities). Perhaps a fourth question is whether there are abiotic mechanisms for producing DMS.

This is science at the cutting edge (and Madhusudhan has been among those emphasizing the lack of certainty, though the doubts have not always been in news stories), and so the only real answer to these questions is that things are currently unclear. This is a fast-moving area of astrophysics and we’ll know a lot more in a few years.

Readers’ wildlife photos

April 12, 2025 • 8:15 am

I remind you once again to send in your photographs as there’s always a need. Thanks!

Today we have some pictures taken by James Blilie and his son Jamie. The captions are indented, and you can enlarge the photos by clicking on them.

Here is a set of photos from our local area.  We live in far southern Washington state in Klickitat County.  These photos are from Klickitat and Skamania Counties.

A mostly full moon photographed on February 8, 2025:

Two views of Mount Adams from the front porch on our new (2024) home.  Both are taken at sunset.  One is a black and white closeup.  The other also shows our local gang of Black-tailed deer (Odocoileus hemionus columbianus).  Mount Adams is about 20 miles directly north of our house:

The next shot shows left to right:  Mount Adams, Mount Rainier, and the Goat Rocks Wilderness from the top of a local ridge.  I took this on March 1, 2025:  It was 60°F (16°C) and sunny, unusual for the first of March!  The view is well worth the work on this hike:

The next bunch of photos were taken at the Wind River Arboretum in Skamania County, definitely on the wet (west) side of the Cascade Range.

A cross-section of the purportedly largest Douglas Fir (Pseudotsuga menziesii) found in Washington state and the placard that accompanies it.  The section was taken at 60-feet (18m) above the ground and the tree was determined to be 393-feet (120m) tall:

[JAC: I can’t help pointing out the superfluous apostrophe in the park sign below.]

Western Red Cedar (Thuja plicata):  Foliage and a (small) example tree:

Two shots by our son Jamie of Bird’s Nest Fungus (Nidulariaceae spp.):

Last year’s Bracken Fern (Pteridium aquilinum), also taken by Jamie:

Views of Sword Ferns (Polystichum munitum), also taken by Jamie:

Equipment:

Mine:

Olympus OM-D E-M5 camera (micro-4/3, crop factor = 2.0)
LUMIX G X Vario, 12-35MM, f/2.8 ASPH lens
LUMIX 35-100mm  f/2.8 G Vario lens
LUMIX G Vario 7-14mm  f/4.0 ASPH lens
LUMIX G Vario 100-300mm F/4.0-5.6 MEGA O.I.S. lens

Jamie’s:

Nikon D5600 (crop factor = 1.5)
Nikkor AF-P DX 18-55mm f/3.5-5.6 G VR lens
Sigma 150-600mm f/5.0-6.3 DG OS HSM lens

Readers’ wildlife photos

February 14, 2025 • 8:15 am

Please send in your wildlife photos! Do I have to beg? Very well, then, I’m begging.

Today we have some photos by ecologist Susan Harrison: mostly birds but two mammals and one astronomy picture. Her captions are indented, and you can enlarge the photos by clicking on them.

More miscellany of early 2025

It’s been a turbulent time at work and a slow time for birdwatching, so it’s challenging to come up any wildlife photos, let alone ones with a theme.   But here are a few more random sights from around Davis, California in January – early February 2025.

Overwintering Snow Geese (Anser caerulescens):

American Beaver (Castor canadensis) in the local stream:

Mountain Bluebird (Sialis curricucoides), an uncommon overwintering bird around here, hunting crickets in a plowed field:

Merlin (Falco columbarius), distinguished from the similar-sized American Kestrel by having a white eyebrow instead of a black mustache (as birders call the vertical facial stripe):

American Kestrel (Falco sparverius) for comparison:

Miniature goats (Capra hircus), seemingly puzzled that the human is looking up into trees rather than bringing them carrots:

Horned Larks (Eremophila alpestris), which always look to me like they’re searching for someone’s lost keys:

American Avocets (Recurvirostra americana), in which females have more upcurved bills than males, possibly giving them different feeding niches:

Killdeer (Charadrius vociferus), inexorably drawn to stony surfaces like gravel roads and railroad beds:

Cinnamon Teal (Spatula cyanoptera) pairing up, Northern Shoveler (Spatula clypeata), and a rear-end view of a Northern Pintail (Anas acuta):

Mixed ducks flying away, as they are—sadly but for good reason—very shy of humans:

Savannah Sparrow (Passerculus sandwichensis), a drab little bird with not much to fear from a human:

And finally, though I’m no celestial photographer, the Moon being approached by Mars:

Māori complain because Starlink satellites disturb their rituals and may make celestial navigation of canoes harder

February 10, 2025 • 9:30 am

Well, I’ll treat you to one more item about indigenous knowledge in New Zealand, this time when it clashes with modern science! It turns out that the Māori are beefing about there being too many satellites in the sky, and beefing for two reasons. First, this raises the possibility that the night sky might be changed, making it lighter, and that might make celestial navigation more difficult. Not that the Māori rely on that any more (actually, their Polynesian and SE Asian ancestors developed it), but their historical practice from hundreds of years ago might be made more difficult.

Second, the satellites are somehow said to interfere with a Māori ritual in which the steam from cooked food is allowed to float up toward the stars. (The ritual arose to give thanks for a good harvest.)  It is not clear to me how satellites would interfere with that, so you’ll have to ask the Māori.

Click below to read the excerpt from Stuff, a New Zealand news site:

Here’s the beefing about the ceremony (I’ve added translations):

A Māori scientist has warned our skies could become clogged with up to 100,000 satellites in the next five years – threatening thousands of years of Māori knowledge in the process.

The pollution could get so bad that stars seen by Māori ancestors would no longer be visible to the naked eye.

Elon Musk’s Starlink satellites have already interfered with a tuku wairua [food/steam] ceremony during Matariki, when whānau [members of a family group] who have died are released to the stars; while satellite proliferation threatens traditional waka hourua navigation [celestial navigation using double-hulled canoes].

Scientist, and Indigenous astronomy expert Te Kahuratai Moko-Painting is part of Sustainable Space – a group seeking to save Earth’s lower orbit, under 2000km, from uncontrolled development.

Moko-Painting often shows up in similar items, for he’s quite a vociferous activist.

Moko-Painting said about 15,000 satellites have been sent into space since the 1950s – about 7000 of those are still functional, and about 10,000 are still in space.

“Between 2022 when these estimates were made, and 2030, it’s estimated that we’ll have between 60,000 to 100,000 satellites in orbit.”

He said the about-3000 Starlink satellites in orbit were “already causing issues”.

. . . He got involved in the issue after the first Matariki public holiday in 2022, when he joined his wife’s whānau at Waahi Pā in Huntly for the hautapu (feeding the stars with an offering of kai [food].

“And just as we were doing our tuku wairua, just as we were sending on those who had passed on from that year, we had 21 Starlink satellites cutting through, right past the path of Matariki [the Pleiades star cluster.”

Apparently people thought that this was the stars’ response to the ceremony, and was propitious, but Moko-Painting—who admits that Starlink is important in communicating with rural communities—still has a beef:

“And those who knew would just say ‘no, that’s actually this man who loves the technology for launching satellites but makes them far too bright’ … and he does them in this line in an eye-catching kind of way, and that’s completely unregulated.”

I doubt that people will stop launching satellites because it somehow interferes with this ceremony. But wait! There’s more! As I said, there’s a possibility that too many satellites may interfere with celestial navigation, which only a few Māori still practice. But this is only a hypothesis, and hasn’t been shown, mainly because only a few stalwarts still use celestial navigation, and only as a way to keep alive that ancestral skill:

Even in the middle of the Pacific Ocean on a waka hourua, double-hulled waka used for voyaging, the night sky is 10% brighter than it used to be, Moko-Painting said. “So one could argue that 10% of what our tūpuna could see with their eyes while navigating is no longer visible to us.”

Master navigator Jack Thatcher has travelled tens of thousands of kilometres on waka hourua, as a guiding light that keeps his crews alive.

The Pacific covers a third of the planet. Thatcher’s journeys – using only stars, ocean swells and birds as guides – include a 3200km trip from Aotearoa to Rarotonga, which is only 67km wide.

. . . Having 100,000 satellites in orbit might be good for “pinpoint accuracy” all around the world, but those who rely on the stars for guidance won’t know which is a satellite and which isn’t.

“They’ll obliterate most of the patterns that we all depend on to help us find our way.”

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He said the satellites were already being discussed in the voyaging community. Light pollution wasn’t the only problem – “eventually they’ll be rubbish”, Thatcher said.

“We’re entering that zone of global extinction, because we’ve polluted our planet, now we want to pollute our heavens.”

While the technology might be used instead to navigate the oceans, “that’s not the point”, he said.

“Indigenous knowledge is something that is a self-determination thing.”

It’s not clear to me, though, that if the night sky is 10% brighter than before, this would somehow efface or even impede celestial navigation. They give no evidence, but some want to kvetch about it anyway, because it apparently erases the achievements of the Māori’s ancestors (not the Māori themselves):

Māori know who they are because of their ancestors’ achievements. “And now you’re going to take that all away from us.”

The first waka [canoe] in this country used navigation knowledge that ancestors accrued over millennia, Thatcher said – travelling from Southeast Asia to Aotearoa almost 6000 years later.

Essentially, he said, if you can no longer navigate the oceans through the stars “it becomes book knowledge only”.

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“Indigenous identity helps people to be who they are and enables them to be proud of who they are, because of their ancestral knowledge that they still hold on to.”

The whole idea of keeping indigenous knowledge alive was that “we’re not dependent on any technology”.

So Moko-Painting has joined a group of scientists calling for holding back on launching satellites.  The article ends abruptly:

SpaceX, which operates Starlink, did not reply to queries at time of publication.

The problem with all this is that these two problems haven’t been demonstrated. The navigation impediment is a theoretical possibility and won’t be known until people like Thatcher try it.  Since they can still do it successfully, even with all those satellites up there, I think this is not a serious concern. As for the satellites interfering with the smoke rising to the stars, that is pure superstition and doesn’t command concern from any rational person.