You are here

News Feeds

Astronomers Only Knew of a Single Binary Cepheid System. Now They Just Found Nine More

Universe Today Feed - Thu, 03/28/2024 - 9:24am

Measuring the distance to far away objects in space can be tricky. We don’t even know the precise distance to even our closest neighbors in the Universe – the Small and Large Magellanic Clouds. But, we’re starting to get to the tools to measure it. One type of tool is a Cepheid Variable – a type of star that varies its luminosity in a well-defined pattern. However, we don’t know much about their physical properties, making utilizing them as distance markers harder. Finding their physical properties would be easier if there were any Cepheid binaries that we could study, but astronomers have only found one pair so far. Until a recent paper from researchers from Europe, the US, and Chile shows measurements of 9 additional binary Cepheid systems – enough that we can start understanding the statistics of these useful distance markers.

Like traditional stars, binary Cepheid systems result when two stars orbit around each other. In this case, both of those stars must be Cepheids – meaning they are massive compared to our Sun and much brighter. In addition, their luminosity must vary in a repeatable pattern so that we can track it consistently.

All of those features can vary a lot if two stars change in luminosity but at different rates and phases around each other. It’s difficult to parse out which star is waxing, which is waning, and which direction they are moving in, both compared to us and each other. Long periods of observation are required to fix some of those variables, and that is precisely what the new paper describes.

The researchers looked at nine sets of Cepheids that were believed to be binary systems but hadn’t yet been confirmed due to the difficulty of separating the two stars from each other. They pulled data from the Optical Gravitational Lensing Experiment (OGLE) database, a variable star observation project run by the University of Warsaw for over 30 years. In so doing, they could confirm, for the first time, that each of these suspected binaries contained two separate stars.

Those nine binary systems were located in the Small and Large Magellanic Cloud and the Milky Way. One located in the Milky Way is by far the closest, at only 11 kiloparsecs (about 3000 light-years) away. The researchers also had good luck because of the length of orbital periods of the binaries they studied – most were over five years, and a shorter observational data set might not have caught them. 

Understanding how these systems exist and where they are is just the first step. Using them for more helpful science is the next. The most obvious way to do so is to increase our understanding of Cepheids. Despite being one of the most commonly used distance markers in the Universe, we know surprisingly little about how they form, what they’re made of, or their life cycle. Closely studying a binary system, where the stars interact, could help shed light (figuratively in this sense) on some of those properties.

Calibrated Period-luminosity Relationship for Cepheids
Credit – NASA

As the authors point out in their paper, this is part of a long-term ongoing project – they were also part of the team that confirmed the original Cepheid binary system back in 2014. OGLE continues to collect more data, as are other sky surveys, and there are likely more Cepheid binaries out there. Every new discovery will help improve our statistical understanding of these critical distance markers – we just need to take the time to find them first.

Learn More:
Pilecki et al. – Cepheids with giant companions II. – Spectroscopic confirmation of nine new double-lined binary systems composed of two Cepheids
UT – What are Cepheid Variables?
UT – Polaris is the Closest, Brightest Cepheid Variable. Very Recently, Something Changed.
UT – Astronomers Rule Out One Explanation for the Hubble Tension

Lead Image:
RS Puppis , one of the brightest known Cepheid variable stars in the Milky Way galaxy
Credit – NASA, ESA, and the Hubble Heritage Team

The post Astronomers Only Knew of a Single Binary Cepheid System. Now They Just Found Nine More appeared first on Universe Today.

Categories: Science

What is the difference in volume between a human sperm and egg?

Why Evolution is True Feed - Thu, 03/28/2024 - 9:23am

Luana and I have been trying to get an accurate figure for the difference in VOLUME between a human sperm and egg, which of course reflects a difference in metabolic investment in making them.  I’m talking now about cytoplasmic volume, not length, as the disparity in length isn’t that relevant (in some flies, the sperm are longer than the fly!).

The figure bandied about is a volume difference of ten million, but I don’t believe that. All these figures trace back to one assertion on a Northwestern University site, but the paper it cites doesn’t give any such figure (or any figure).  Everybody quotes that figure, but it seems way too large for me. However, it might be accurate.

So, I’m crowdsourcing the answer. I have no prize here except for approbation (and I’ll put the winner and correct answer below).

Question: What is the difference in cytoplasmic volume between a human sperm and a human egg?  A reference to a respectable source must be included.

Thank you!

Categories: Science

Japan’s SLIM moon lander surprisingly survived a second lunar night

New Scientist Feed - Thu, 03/28/2024 - 9:13am
The Smart Lander for Investigating Moon spacecraft has sent back images after surviving its second lunar night – generally these periods are so cold they destroy spacecraft electronics
Categories: Science

Artificial intelligence boosts super-resolution microscopy

Computers and Math from Science Daily Feed - Thu, 03/28/2024 - 8:10am
Generative artificial intelligence (AI) might be best known from text or image-creating applications like ChatGPT or Stable Diffusion. But its usefulness beyond that is being shown in more and more different scientific fields.
Categories: Science

Artificial intelligence boosts super-resolution microscopy

Matter and energy from Science Daily Feed - Thu, 03/28/2024 - 8:10am
Generative artificial intelligence (AI) might be best known from text or image-creating applications like ChatGPT or Stable Diffusion. But its usefulness beyond that is being shown in more and more different scientific fields.
Categories: Science

Can metalens be commercialized at a fraction of the cost?

Matter and energy from Science Daily Feed - Thu, 03/28/2024 - 8:10am
Researchers suggests a groundbreaking strategy to expedite the commercialization of metalens technology.
Categories: Science

Unlocking supernova stardust secrets

Space and time from Science Daily Feed - Thu, 03/28/2024 - 8:10am
New research has discovered a rare dust particle trapped in an ancient extra-terrestrial meteorite that was formed by a star other than our sun.
Categories: Science

ALMA finds new molecular signposts in starburst galaxy

Space and time from Science Daily Feed - Thu, 03/28/2024 - 8:10am
The ALMA radio telescope has detected more than 100 molecular species, including many indicative of different star formation and evolution processes, in a galaxy where stars are forming much more actively than in the Milky Way. This is far more molecules than were found in previous studies. Now the team will try to apply this knowledge to other galaxies.
Categories: Science

Study unlocks the power of visible light for sustainable chemistry

Matter and energy from Science Daily Feed - Thu, 03/28/2024 - 8:10am
A breakthrough in sustainable molecular transformations has been announced. Chemists have developed an important way to harness the power of visible light to drive chemical processes with greater efficiencies, offering a greener alternative to traditional methods.
Categories: Science

Nuclear fusion, lithium and the tokamak: Adding just enough fuel to the fire

Matter and energy from Science Daily Feed - Thu, 03/28/2024 - 8:09am
Building upon recent findings showing the promise of coating the inner surface of the vessel containing a fusion plasma in liquid lithium, researchers have determined the maximum density of uncharged particles at the edge of a plasma before certain instabilities become unpredictable. The research includes observations, numerical simulations and analysis from their experiments inside a fusion plasma vessel called the Lithium Tokamak Experiment-Beta (LTX- ). This is the first time such a level has been established for LTX- , and knowing it is a big step in their mission to prove lithium is the ideal choice for an inner-wall coating in a tokamak because it guides them toward the best practices for fueling their plasmas.
Categories: Science

Revolutionary biomimetic olfactory chips to enable advanced gas sensing and odor detection

Matter and energy from Science Daily Feed - Thu, 03/28/2024 - 8:05am
A research team has addressed the long-standing challenge of creating artificial olfactory sensors with arrays of diverse high-performance gas sensors. Their newly developed biomimetic olfactory chips (BOC) are able to integrate nanotube sensor arrays on nanoporous substrates with up to 10,000 individually addressable gas sensors per chip, a configuration that is similar to how olfaction works for humans and other animals.
Categories: Science

Revolutionary biomimetic olfactory chips to enable advanced gas sensing and odor detection

Computers and Math from Science Daily Feed - Thu, 03/28/2024 - 8:05am
A research team has addressed the long-standing challenge of creating artificial olfactory sensors with arrays of diverse high-performance gas sensors. Their newly developed biomimetic olfactory chips (BOC) are able to integrate nanotube sensor arrays on nanoporous substrates with up to 10,000 individually addressable gas sensors per chip, a configuration that is similar to how olfaction works for humans and other animals.
Categories: Science

Could bone marrow transplants transmit Alzheimer's disease?

New Scientist Feed - Thu, 03/28/2024 - 8:00am
The mainstream view is that Alzheimer's starts in the brain, but researchers were able to transfer the condition in mice by injections of bone marrow
Categories: Science

Now the ideologues are going after the nucleus as the CEO of a cell factory, a view supposedly supporting hierarchies and the patriarchy

Why Evolution is True Feed - Thu, 03/28/2024 - 7:45am

There’s more DNA-dissing is going on, this time in a piece in Aeon arguing that it is bad for society and for biology to think of the cell as an assembly line of molecules controlled by a “boss” in the nucleus. The cell, after all, is more socialistic!

Author Charudatta Navare, whose short bio is given below after his name, advances his thesis that the cell is NOT an entity “controlled” from the top down by the capitalistic nucleus, as if the cell were a “factory” with its sweating workers—the contents of the cell—lashed by the whip of the nuclear DNA.  To Navare, that’s simply an invidious capitalistic/patriarchal/classist metaphor. Instead, the “workers”, including everything in the cytoplasm like the ribosomes, mitochondria, vacuoles, vesicles, endoplasmic reticulum, and ribosomes, are independent entities with their own heredity, all cooperating in a genial manner to make the cell function smoothly. As Navare asserts, “the nucleus is only a tiny subset of the hereditary material.” The cell, it seems, is more like a collective farm than a car factory.

The message, which Navare repeats at length, is THE CELL IS NOT A HIERARCHY.  The motivation for the misguided view that the Big Boss Nucleus controls the workers is, consciously or not, to read into nature the  hierarchy of modern patriarchal society. To Navare, the hierarchical view of the cell not only buttresses a maladaptively structured society, but, most of all damages biology by distorting our understanding.

Navare’s big mistake is this: the nucleus, which contains the genes, really is the boss. Even the mitochondria, which replicate themselves and contain their own genes, interact intimately with the nucleus to perform a number of functions. (The mitochondria, as you may know, are derived from original endosymbiotic bacteria that have, though evolution, been integrated into the cell as an essential organelle. Chloroplasts, essential for photosynthesis, have a similar origin and interact with the nuclear in the same way.) But both of these organelles can function only with the help of nuclear genes. And they’re the sole exception to the notion that prganismal DNA is the recipe for the cell and the organism.

The rest of the organelles in the cytoplasm, then, ultimately derive from genes, as does the spatial organization of the egg that helps set off development. This is not to say that random factors, like chemical concentration in different parts of the egg, can influence development, but at bottom, yes, everything in the cell save the mitochondria and chloroplasts ultimately come from the DNA in the nucleus. Without the Nuclear Boss, the workers lose their jobs and the factory goes kaput.  Figuring out how this all evolved, of course, is a difficult issue. But evolve it did, via changes in the DNA.

Click below to read the article in Aeon:

Here’s the thesis (Navare’s words are indenteed):

In short, the textbooks paint a picture of a cellular ‘assembly line’ where genes issue instructions for the manufacture of proteins that do the work of the body from day to day. This textbook description of the cell matches, almost word for word, a social institution. The picture of the cytoplasm and its organelles performing the work of ‘manufacturing’, ‘packaging’ and ‘shipping’ molecules according to ‘instructions’ from the genes eerily evokes the social hierarchy of executives ordering the manual labour of toiling masses. The only problem is that the cell is not a ‘factory’. It does not have a ‘control centre’. As the feminist scholar Emily Martin observes, the assumption of centralised control distorts our understanding of the cell.

A wealth of research in biology suggests that ‘control’ and ‘information’ are not restricted at the ‘top’ bu

t present throughout the cell. The cellular organelles do not just form a linear ‘assembly line’ but interact with each other in complex ways. Nor is the cell obsessed with the economically significant work of ‘manufacturing’ that the metaphor of ‘factory’ would have us believe. Instead, much of the work that the cell does can be thought of as maintaining itself and taking ‘care’ of other cells.

Why, then, do the standard textbooks continue to portray the cell as a hierarchy? Why do they invoke a centralised authority to explain how each cell functions? And why is the imagery so industrially loaded?

It’s capitalism and the patriarchy, Jack! But in fact, the textbooks make DNA the boss because it is the boss. But wait, I’m getting ahead of myself:

All of this coded information in the cytoplasm leads us to ask: why do modern textbooks, which are supposed to present the standard, well-accepted knowledge of the day, continue to portray the cell as hierarchical in structure? Why do science journalists continue to refer to the codes and programs of genes in the nucleus when discussing how life develops and evolves?

believe that the hold of the centralised view comes from how it resonates with the human social order. The nucleus providing instructions and the cytoplasm performing the labour of ‘nurturing’ sounds ‘natural’ and even ‘obvious’ in a patriarchal society. The central nucleus ordering its ‘underling’ cytoplasm to actually carry out tasks sounds obvious in a class-stratified society.

. . .The reason we find centralised functioning everywhere is not necessarily because it is everywhere. It just appears to be everywhere because of the lens through which we view the world. When scientific narratives, using all the authority of science, project the social hierarchy onto nature, they can reinforce the same hierarchy as ‘natural’. The centralised model from cells to animal social groups suggests that everything in nature is centralised, and that centralisation works. The ‘truth’ about nature is influenced by our values, and this ‘truth’ can then play a role in doubling down and reinforcing the same social values in the world.

. . . I believe that the hold of the centralised view comes from how it resonates with the human social order. The nucleus providing instructions and the cytoplasm performing the labour of ‘nurturing’ sounds ‘natural’ and even ‘obvious’ in a patriarchal society. The central nucleus ordering its ‘underling’ cytoplasm to actually carry out tasks sounds obvious in a class-stratified society.

And this metaphor, says Navare, damages our understanding of biology. I can’t think of how, since scientists have been beavering away at understanding the cell, and I haven’t sees them impeded by a bad metaphor. Perhaps they have, but I can’t think of one example.  Navare keeps saying that the view is an impediment, but gives no examples of how.  Here are more of his lucubrations:

How science conceptualises the cell also gives us insight into how we think of scientific objectivity. We often think that, when values interfere with science, the quest for truth and accuracy is put at risk. Scientists are supposed to leave their values and beliefs outside their labs. However, research in feminist science studies suggests otherwise. One does not necessarily need to be free of values to do good science, but denying their influence undermines the quality of scientific work. Instead of denial, reflecting on values and biases would help researchers steer clear of the pitfalls. Self-reflection can help scientists identify how their values are shaping their science, and think of better experimental designs that could ‘catch’ their assumptions before they compromise results.

. . .But the trouble with doubling down on this kind of metaphor as a stand-in for science is that assumptions about how a cell ought to function prevent us from understanding how the cell really functions. What is more, when science projects social hierarchies onto the cell, it also reinforces the notion that social hierarchies are ‘natural’.

In fact, Navare says that there are other metaphors that could serve equally well:

. . .Unfortunately, the centralised and hierarchical metaphor, so pervasive in textbooks, is often the only one for the internal workings of the cell.

One alternative metaphor for the cell nucleus, I tentatively suggest, could be a ‘collaborative notebook’. The cell keeps this notebook, and all the cell’s components use it to keep track of their activities and help maintain the cell. The cell ‘writes’ in the notebook, writes in the ‘margins’ and ‘refers’ to its own notes. Cellular organelles sense each other’s needs and take ‘care’ of each other. While the ‘factory’ metaphor attributes control and information to the nucleus, the ‘nucleus as a collaborative notebook’ shows agency on the part of the cell. While the factory metaphor makes the cell seem obsessed with ‘production’, alternative metaphors can highlight the mutual aid among the cellular components and the labour of maintaining the cell.

Try as I might, I fail to see how the Notebook Metaphor is more helpful than the “factory”metaphor, but of course it fits right into the Kropotkin-esque tendency to see mutual helpfulness (one could also see it reflectiong socialism). But truth be told, I’m not that enamored of the factory metaphor, either. All I care about is how the cell works, and you can’t do that without appreciating the overweening effects of genes whose action produces almost everything in the cell, influences how the organism develops, and is, in the end, the result of the selection among genes. Every adaptive aspect of development, including cell structure and function, depends on adaptive changes in the DNA put in place by natural selection (this holds also for how the mitochondria and cytoplasm interact with nuclear DNA).

Here’s how Navare minimizes the effects of genes.

The nucleus, of course, does make some hereditary contribution, and we understand it in great detail. But the nucleus is only a tiny subset of the hereditary material. If we don’t even search for hereditary information in the egg cell – if we never describe that information as hereditary – we will keep propagating the idea that biological inheritance is restricted to the nucleus alone. Now I’m not sure what he means by “hereditary material.” Yes, the mitochondria and cytoplasm do replicate themselves by fission (and duplication of their DNAz0, but none of the other organelles are self-replicating, or “hereditary” in that sense. The organelles and cytoplasmic constituents, like vacuoles and ribosomes, are made by recipes written in the DNA (ribosomes, for example, the site of protein synthesis,m are largely made of RNA sent out from the nucleus). Without the DNA coding for proteins, we have no enzymatic pathways, no means of constructing organelles, and no way of building up the constituents of a cell.

Now this is not to say that the construction of a cell or an embryo doesn’t require anything other DNA, but it does require the products of DNA. For example, how does a fertilized egg know which end is going to be the head end and which the tail? And given that, what about the back from front? (Once these are determined, of course, left versus right has already been specified.) It is because the mother’s DNA makes RNAs that are distributed asymmetrically in the egg, and those differential distributions of RNA, via the proteins they make, are what starts the anterior-posterior and dorso-ventral axes from forming. Now these RNAs are moved through the egg cell by microtubules, part of the “cytoskeleton”, so the microtubules must also be there in the egg. But ultimately, it’s the DNA that contains the recipe for these microtubules—and of course the axis-forming RNA.

And all of this has evolved by natural selection causing the differential proliferation—of genes.  In the end, everything save some parts of the mitochondria and chloroplasts, is the product of evolution, and that means of changes in DNA.  In both evolution and development, it’s DNA all the way down. Even the response of an organism to its environment, like cats growing longer hair in the winter, is an evolved response based on changes in genes in the DNA. The environment is the cue, but the response lies in the genome.

One more example of gene-dissing:

We are told that the genes contain blueprints to make proteins. However, genes do not contain all the information needed to make proteins. They only specify a one-dimensional protein chain; the three-dimensional structure that the proteins take, which is vital for their function, is determined by the cellular environment as well. Further, the way proteins behave also varies with where they are in the cytoplasm. The genetic ‘information’, on its own, is nowhere near enough for the cell to function.

No the proteins largely fold on their own once they are made. But does Navare not realize that the information that makes the linear structure of a protein into a three-dimensional structure rests largely already in the linear arrangement of amino acids, which creates the linear structure of a protein? Once that’s made, the proteins largely fold spontaneously into the appropriate three-dimensional structure, which is of course crucial for enzymes to work and proteins like hemoglobin to function. But without the correct linear structure, specified by the DNA, the right spontaneous folding won’t happen. So again the DNA is largely the boss, and has evolved to produce proteins that fold up the right way. The DNA is even more bossy because sometimes proteins are helped in their folding, or retain their folding, through their interaction with enzymes. What are enzymes? Proteins made by DNA.  Again, it’s DNA all the way down.

That aside, Navare manages to get in a timely word for how DEI can help our understanding as well:

Science is undoubtedly a human endeavour. The feminist philosopher Donna Haraway describes science as a conversation between partial perspectives that each individual gets from the vantage point of their position. As Just’s science shows, people with different life experiences might have different perspectives and may ask different questions. [JAC: E. E. Just, one of the only well known black scientists working in the early 20th century, made notable contributions to understanding the cell.] Admittedly, the connections between scientists’ backgrounds and their work are not always so direct. But the social position of scientists can still serve as one of the factors that influence their work. We often say science is self-correcting. We think that science changes its views when new information comes to light. But this new information doesn’t emerge from a vacuum. It doesn’t emerge only from new techniques. It is also generated when diversity and representation are important in their own right from the perspective of equity, diverse perspectives would benefit science most of all. Objectivity is not an individual burden but a collective one. While diversity and representation are important in their own right from the perspective of equity, diverse perspectives would benefit science most of all. Objectivity is not an individual burden but a collective one.

And clearly class has conditioned our view of the cell as well:

Historically, the majority of scientists have been male, upper class, and belonging to the dominant castes and races. It is possible that the social position of scientists helped them relate to the notion of a nucleus that continues discharging instructions while taking for granted the knowledge and skills required in actually doing the work. The Nobel laureate David Baltimore described genes as the ‘executive suite’ and the cytoplasm as the ‘factory floor’. The executive suite appears more valuable and deserving of more remuneration, while the toiling masses on the factory floor are thought to be merely executing the instructions, undervaluing the wealth of explicit and tacit knowledge and skill.

Poor Baltimore, bamboozled by a view of the cell. I guess it was all the dosh that comes with a Nobel Prize that has warped his viewpoint.

There’s a feminist point of view, too, one that presumably sees the cell as more cooperative than a patriarchy would make us think:

Science is often described as objective and value-free, but philosophers of science have pointed out that values can guide the questions that scientists ask, the hypotheses they make, and the way they interpret their results. The field of feminist science studies, in particular, has called into question the sole role of the nucleus where heredity is concerned.

. . . . How science conceptualises the cell also gives us insight into how we think of scientific objectivity. We often think that, when values interfere with science, the quest for truth and accuracy is put at risk. Scientists are supposed to leave their values and beliefs outside their labs. However, research in feminist science studies suggests otherwise.

There are no references for either of these statements.  My own view is that we need to draw scientists from throughout society (giving everyone equal opportunities to suceed), but concentrating on merit, which also includes the ability to “think outside the box”. That said, with one exception I haven’t seen fruitful sex-, class- or race-specific ways of approaching biology. The one exception my feeling that women evolutionists helped us concentrate more on female preference as opposed to male traits in sexual selection.

Finally, Navare issues a dire warning of the dangers inherent in a metaphor that, in the end, is only a metaphor. (Bolding is mine.)

If we are unable to conceive of the cell, the basic unit of organisms like ours, without coercive hierarchies, we will never fully appreciate the complexity of nature. If we fail to imagine society without a centralised authority, we will find it difficult to understand or empower the oppressed. Unless we reflect on our assumptions, our science will be loaded with so many landmines it may never unravel all the mysteries of life.

In the end, Navare manages to connect the “factory” view of the cell with oppression in society.  We can only free workers from their chains if we free our view of the cell as having a DNA Boss. This, of course, is music to the ears of “progressives”.

Sorry, I can’t agree. If you can find one example of how our understanding of life has been impeded by the “factory” metaphor—which after all isn’t something that biologists hold in their heads as a controlling mantra while they do research—do let me know.

Categories: Science

Mathematicians are bitterly divided over a controversial proof

New Scientist Feed - Thu, 03/28/2024 - 6:00am
An attempt to settle a decade-long argument over a controversial proof by mathematician Shinichi Mochizuki has seen a war of words on both sides, with Mochizuki dubbing the latest effort as akin to a "hallucination" produced by ChatGPT
Categories: Science

AI for prescription drug information: Not yet useful for health care – but it’s coming

Science-based Medicine Feed - Thu, 03/28/2024 - 6:00am

ChatGPT may not replace a health care professional's assessment yet, but its capabilities are growing.

The post AI for prescription drug information: Not yet useful for health care – but it’s coming first appeared on Science-Based Medicine.
Categories: Science

Chair for gamers boosts player performance and prevents muscular aches

New Scientist Feed - Thu, 03/28/2024 - 5:00am
Gamers seemed to be more comfortable after playing in a specialist gaming chair compared with a standard office chair
Categories: Science

Mars may have captured and split a comet to create its two moons

New Scientist Feed - Thu, 03/28/2024 - 1:00am
How the Red Planet acquired its two moons, Phobos and Deimos, is unknown – they could have formed after something collided with the planet, or started out as asteroids – but now there is a hint of a cometary origin
Categories: Science

Early galaxy seen by JWST contains giant young stars and supernovae

New Scientist Feed - Wed, 03/27/2024 - 11:00pm
The light signature from GLASS-z12, one of the most distant galaxies we have ever seen, suggests some of its stars have already exploded as supernovae
Categories: Science

DART Changed the Shape of Asteroid Dimorphos, not Just its Orbit

Universe Today Feed - Wed, 03/27/2024 - 8:50pm

On September 26th, 2022, NASA’s Double Asteroid Redirection Test (DART) collided with the asteroid Dimorphos, a moonlet that orbits the larger asteroid Didymos. The purpose of this test was to evaluate a potential strategy for planetary defense. The demonstration showed that a kinetic impactor could alter the orbit of an asteroid that could potentially impact Earth someday – aka. Potentially Hazardous Asteroid (PHA). According to a new NASA-led study, the DART mission’s impact not only altered the orbit of the asteroid but also its shape!

The study was led by Shantanu P. Naidu, a navigation engineer with NASA’s Jet Propulsion Laboratory (JPL) at Caltech. He was joined by researchers from the Lowell Observatory, Northern Arizona University (NAU), the University of Colorado Boulder (UCB), the Astronomical Institute of the Academy of Sciences of the Czech Republic, and Johns Hopkins University (JHU). Their paper, “Orbital and Physical Characterization of Asteroid Dimorphos Following the DART Impact,” appeared on March 19th in the Planetary Science Journal.

The Didymos double asteroid system consists of an 851-meter-wide (2792 ft) primary orbited by the comparatively small Dimorphos. The latter was selected as the target for DART because any changes in its orbit caused by the impact would be comparatively easy to measure using ground-based telescopes. Before DART impacted with the moonlet, it was an oblate spheroid measuring 170 meters (560 feet) in diameter with virtually no craters. Before impact, the moonlet orbited Didymos with a period of 11 hours and 55 minutes.

Artist’s impression of the DART mission impacting the moonlet Dimorphos. Credit: ESA

Before the encounter, NASA indicated that a 73-second change in Dimorphos’ orbital period was the minimum requirement for success. Early data showed DART surpassed this minimum benchmark by more than 25 times. As Naidu said in a NASA press release, the impact also altered the moonlet’s shape:

“When DART made impact, things got very interesting. Dimorphos’ orbit is no longer circular: Its orbital period is now 33 minutes and 15 seconds shorter. And the entire shape of the asteroid has changed, from a relatively symmetrical object to a ‘triaxial ellipsoid’ – something more like an oblong watermelon.”

Naidu and his team combined three data sources with their computer models to determine what happened to the asteroid after impact. The first was the images DART took of Dimorphos right before impact, which were sent back to Earth via NASA’s Deep Space Network (DSN). These images allowed the team to gauge the dimensions of Didymos and Dimorphos and measure the distance between them. The second source was the Goldstone Solar System Radar (GSSR), part of the DNS network located in California responsible for investigating Solar System objects.

The GSSR was one of several ground-based instruments that precisely measured the position and velocity of Dimorphos relative to Didymos after impact – which indicated how the mission greatly exceeded expectations. The third source was provided by ground-based telescopes worldwide that measured changes in the amount of life reflected (aka. light curves) of both asteroids. Much like how astronomers monitor stars for periodic dips (which could indicate a transiting planet), dips in Didymos’ luminosity are attributable to Dimorphos passing in front of it.

Artist’s impression of the ESA’s Hera mission rendezvousing with Dimorphos. Credit: NASA

By comparing these light curves from before and after impact, the team learned how DART altered Dimorphos’ motion. Based on these data sources and their models, the team calculated how its orbital period evolved and found that it was now slightly eccentric. Said Steve Chesley, a senior research scientist at JPL and a co-author on the study:

“We used the timing of this precise series of light-curve dips to deduce the shape of the orbit, and because our models were so sensitive, we could also figure out the shape of the asteroid. Before impact, the times of the events occurred regularly, showing a circular orbit. After impact, there were very slight timing differences, showing something was askew. We never expected to get this kind of accuracy.”

According to their results, DART’s impact reduced the average distance between the two asteroids to roughly 1,152 meters (3,780 feet) – closer by about 37 meters (120 feet). It also shortened Dimorphos’ orbital period to 11 hours, 22 minutes, and 3 seconds – a change of 33 minutes and 15 seconds. These results are consistent with other independent studies based on the same data. They will be further tested by the ESA’s Hera mission, scheduled to launch in October 2024, when it makes a flyby of the double-asteroid and conducts a detailed survey.

Further Reading: NASA

The post DART Changed the Shape of Asteroid Dimorphos, not Just its Orbit appeared first on Universe Today.

Categories: Science

Pages

Subscribe to The Jefferson Center  aggregator