This beautiful, scary demonstration of nature's power happened in Porthcawl, a town on the south coast of Wales. At the end of Porthcawl Pier stands a white lighthouse built in 1860 — but here it is hidden behind the waves! It was the last coal and gas powered lighthouse in the United Kingdom.
Luhman 16 is a pair of brown dwarfs orbiting each other just 7 light years from us. The smaller one, Luhman 16B, is half covered by huge clouds. These clouds are hot — 1200 °C — so they're probably made of sand, iron or salts. Some of them have been seen to disappear! Why? Maybe 'rain' is carrying this stuff further down into the star, where it melts.
So, we're learning more about something cool: the L/T transition.
Brown dwarfs can't fuse ordinary hydrogen, but a lot of them fuse the isotope of hydrogen called deuterium that people use in H-bombs — at least until this runs out. The atmosphere of a hot brown dwarf is similar to that of a sunspot: it contains molecular hydrogen, carbon monoxide and water vapor. This is called a type M brown dwarf.
But as they run out of fuel, they cool down. The cooler type L brown dwarfs have clouds! But the even cooler type T brown dwarfs do not. Why not?
This is the mystery we may be starting to understand: the clouds may rain down, with material moving deeper into the star! Luhman 16B is right near the L/T transition. Its big brother Luhman 16A is type L.
Finally, as brown dwarfs cool below 300 °C, astronomers expect that ice clouds start to form: first water ice, and eventually ammonia ice. These are the type Y brown dwarfs. Wouldn't that be neat to see? A star with icy clouds!
The smallest brown dwarfs are 13 times the mass of Jupiter. Smaller than that, and they can't fuse deuterium.
There's been a lot of news articles about brown dwarfs in the last few days, but I think you should read the heroic astronomy bloggers who covered this story over a year ago. Like Caroline Morley:
She doesn't like how people call brown dwarfs "failed stars". I agree! It's like calling a horse a "failed giraffe".
For more, try:
The palms here are native to the area: Washingtonia filifera, the desert fan palm. They're different than the palm trees you see along city streets in Los Angeles. They grow around oases and streams in the deserts of southern California and western Arizona. I've often seen them in Indian Canyons near Palm Springs... but this was the first time I visited this other oasis.
Around here, the Cahuilla and related tribes used the leaves of fan palms to make sandals, thatch roofs, and baskets. The fruit was eaten raw, cooked, or ground into flour for cakes. The stems were used to make cooking utensils. And standing under these palms near an oasis, it's cool even on a ferociously hot day! It's definitely the place to be.
It's fun to imagine the world of the Cahuilla, where these oases would be hugely desirable places to live, and centers of activity.
The Thousand Palms Oasis Preserve is a privately owned park that lets you in for free. It's part of the Coachella Valley Preserve System, which was set up to protect a rare species of lizard that roams the dunes around here: the Coachella Valley fringe-toed lizard Uma inornata. But a lot of other things live in this area: the desert is not deserted!
Tomorrow we go to Erlangen, a completely different place in a completely different climate.
One of my favorite parts of Mars is Vastitas Borealis, the vast plains in the north. They're full of dunes, many covered with carbon dioxide frost, some of which do mysterious things in the spring. Here we see some crescent-shaped dunes called barchans. They're about 750 meters long. They slowly move along as wind blows sand up the shallow slope and it rolls down the steep slope. The white stuff is mostly CO2 frost, with a little water ice.
This photo is from the HiRISE project — the High Resolution Image Science Experiment. They write:
The purpose of this observation is to image dunes where substantial "gullies" formed in the previous Mars winter. These features likely formed due to carbon dioxide defrosting or the weight causing the surface to slump.The gullies at this site are particularly large, which is intriguing, suggesting that this site be monitored to see if stages of gully formation or details of activity can be observed.
Here's what they said about a similar photo taken in the previous winter:
Geologists would classify these dunes as "sand-starved" because the ground between the dunes has almost no sand. This ground shows a pattern of cracks that is typical of icy permafrost that undergoes seasonal expansion and contraction. It is also possible that this subsurface ice exists inside the dunes. If so, the dunes are not currently moving, being "stabilized" by this ice.This idea is supported by the observation that there are small landslide gullies being cut into the dunes, something not seen if the dunes are rejuvenated as they move in the wind. However, to test this idea this area has been repeatedly imaged by multiple cameras on different spacecraft. With meticulous care it will be eventually possible to determine just how much the dunes have moved or changed over the past several years.
I knew Newton did alchemy. But I hadn't known Galileo did astrology! Alchemy and astrology weren't disreputable back then, so it's not really surprising. But not many people talk about it - perhaps because Galileo is considered a founder of modern science, and now scientists think astrology doesn't make sense.
Here's the main evidence:
The Inquisition first went after Galileo in 1604, on the charge of making astrological predictions that denied free will. Astrology was okay, but fatalistic predictions were not.
He was accused of haver ragionato che le stelle, i pianeti at gl'influssi celesti necessitino - having reasoned that the stars, planets and celestial influences were able to determine the course of events. He was acquitted.
The Moon is very debilitated and in a sign which obeys. She is dominated by family relationships. Saturn signifies submission and severe customs which gives her a sad demeanour, but Jupiter is very well with Mercury, and well-aspected corrects this. She is patient and happy to work very hard. She likes to be alone, does not talk too much, eats little with a strong will but she is not always in condition and may not fulfil her promise.
We have astrological charts that Galileo drew up for himself.
We have about 20 other astrological charts drawn up by Galileo, including one for the Venetian aristocrat Giovanni Sagredo, who later became a character in Galileo's famous dialogue. We have a letter from Sagredo to Galileo requested a chart reading for a colleague.
But I heard the story first from Darrel Rutkin, here in Erlangen at the Internationales Kolleg für Geisteswissenschaftliche Forschung where my wife is working. Unfortunately his paper seems hard to get online:
The story of how scientists rejected astrology is interesting and complex. We shouldn't pretend scientists knew all along that it was wrong, by some sort of 'common sense'. Science is not the same as common sense: it takes real work.
For a quick introduction to this story, try:
Before scientists threw out astrology, they tried to understand, explain or reform it. Here's a tiny snippet:
Francis Bacon proposed a serious reform of astrology in the De augmentis scientiarum of 1623, a Latin enlargement and reworking of his Advancement of Learning (1605), written during the forced retirement that followed his impeachment as Lord High Chancellor. Bacon began by identifying the many superstitions and lies that needed to be removed from its domain, including the individual planetary rule of each hour of the day and the astrological figure constructed for precise points of time. Reviewing the four principal divisions of astrological practice — revolutions, nativities, elections, and interrogations — he argued that the last three had little if any foundation, whereas he described revolutions as much more sound, though nonetheless in need of attention.
I didn't know these four kinds of astrology:
Building on Ptolemy's distinction, Albertus Magnus described the four types of astrological praxis in his Speculum astronomiae (Mirror of the Science of the Stars, ca. 1260s): 'Revolutions' were concerned with large-scale changes, primarily in the weather but also in state affairs. This was the major feature of the annual prognostications found in almanacs and elsewhere [....] 'Nativities', on the other hand, involved the astrological configuration at a person's birth. 'Interrogations' entertained questions on matters of concern, including personal, medical, and business affairs. Finally, 'elections' determined the most propitious moment to begin an enterprise or perform an activity, such as crowning.
The famous chemist (and alchemist!) Robert Boyle was also involved:
Bacon's vision of a reformed astrology was further developed by the English natural philosopher and alchemist Robert Boyle (1627-1691), one of the founders of the Royal Society of London. In his "Suspicions about some Hidden Qualities of the Air" (1674), Boyle adapted Bacon's position, declaring that the luminaries, planets, and fixed stars likely emit subtle but corporeal emanations beyond light and heat, which reach to our air. Developing this idea in the appendix, "Of Celestial and Aerial Magnets", Boyle suggested experiments to test apparently good magnets by varying the air in which they were located according to different times, temperatures, and aspects of the planets. In this way, the different natures of the air could be discovered along with possible correspondences between the terrestrial and celestial realms.
© 2014 John Baez
baez@math.removethis.ucr.andthis.edu