Category Archives: Astronomy

There's a chance a rare meteor "storm" will occur Thursday night, and eastern Canada might be able to catch it.

Meteor storms can be defined as a substantially higher-than-normal outbursts of meteors entering our atmosphere, and occur when Earth sweeps through a dense cloud of leftover cometary debris.

These events can produce several hundred meteors per hour. In 1833, a storm associated with the Leonid meteor shower produced 13,000 meteors per hour at its peak.

While the annual alphaMonocerotids is forecast to produce an outburst this year, it is not expected to be anywhere close to that rare 1833 event. But it will still be something to see if the weather co-operates.

"We might see a meteor, and then a few seconds another meteor, and then two more meteors,"said Peter Brown, professor and Canada research chair at Western University's department of physics and astronomy.

However, there are a few things that make this potential outburst unpredictable, particularly for us here in Canada.

One is that the radiant, or the area from which the meteors appear to originate the constellation Monoceros, which is where the shower gets its name will be low in the south, to the lower left of the very familiar constellation Orion.

The other is that, unlike with many meteor showers, it's not known whichcomet is responsible for this one,which makes it more difficult to understand where much of the debris is and how spread out it is.

As well, there's the good old Canadian fall weather: it's typically cloudy this time of year.

And finally, it's how brief the shower will be: the peak is between just 15 and 20 minutes.

"Hollywood always has this view of meteor showers as these things that happen in 20 minutesand it's all over," Brown said. "And every other meteor shower is not like that except this one and that's rare."

The potential storm is making headlines due to the prediction by astronomers and meteor expertsPeter Jenniskens and Esko Lyytinen,recently published on the site Meteor News, thatthere's the potential for this year's shower to produce between 100 meteors an hour and upwards of 1,000 an hour.

To put that in perspective, two of the year's best meteor showers the Perseids in August and the Geminids in December can produce, at their peak, about 100 to 150 meteors per hour in a dark-sky location.

The alpha Monocerotids, however, which occur at this time of year, typically only produce just a few an hour.

The last outburst, in 1995, produced roughly 400 an hour.

Jenniskens and Lyytinen made the forecast for the burstbecause the geometry the location of Earth, the location of the debris field is believed to beroughly the same as it was in 1995.

However, because there are a lot of unknowns, some astronomers believe the outburst will produce far fewerthantheir prediction.

"This year is the best geometry encounter since 1995," Brown said."The problem is the exact encounter geometry depends on really knowing the orbit of the meteoroidsas well, and we don't know them that precisely. So within that uncertainty, it could be that we just glance the trail or miss it in which case nothing happens towe plow right through the middle."

If Earth does plow right through it, that means we'll get an intense shower for 15 or 20 minutes, perhaps seeing five or six meteors every minute.

"Even if everything works out well, you'd see in 30 minutes to 40 minutes as many meteors as you'd see during the peak of the Perseids when the radiant is right overhead," Brown said. "It'll be obvious that something is going on."

But even in the best-case scenario, with aperfectly clear sky, there's still that narrow window.

And even then, the entire country won't be privy to the show.

Anyone west of roughly Saskatoonwon't be able to see it.

The peak will begin at roughly 4:50 a.m. UTCFriday, whichwill be:11:50 p.m. Eastern Time and 10:50 p.m. Central Time on Thursday; and12:50 a.m. Atlanticand 1:20 a.m. Newfoundland Time on Friday.

If you're clouded out, you can always try watching online (providing there areclear skies). The Virtual Telescope Project will attempt to catch the outburst and cover it live.

If we do indeed see any, these meteors are fast-moving, andthere could be "grazers" meteors that come in at a shallow angle. These meteors are going through more atmosphere, producing long tails before finally burning up entirely.

Whether or not it puts on a show, astronomers will be able to learn more about this strange annual meteor shower.

It wasn't until the 1950s that astronomers began to realize this was an annual meteor shower. Andit wasn't until 1995 that it became clear the comet responsible was unknown, and highly unusual in its orbit.

But for the general public, it's yet another reminder that there's a lot going on in our solar system and that it's not always so predictable.

"It's neat. I think people should go out and take a look," Brown said. "You never know."

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Astronomers believe we could be in for a rare meteor storm - CBC.ca

The researchers created simulations to show that this was possible and described their results in the journal Physical Review Letters.

On July 29, 2017, gravitational wave detectors spotted the heaviest black hole merger yet, dubbed GW170729. One of the black holes in the merger was likely more than 50 times the mass of the Sun. Black holes that are created when a dying star collapses shouldnt be this big, so astronomers think something else was probably at play. Maybe that black hole was the result of a previous merger itself.

One place where a black hole might swallow multiple other singularities is in an environment thats dense with stars. Globular star clusters, for example, pack lots of stars and the black holes they sometimes form into a relatively tight space. There, a black hole might meet and combine with other black holes multiple times.

The new paper describes another kind of environment where black holes might merge more than once. Disks of material that swirl around supermassive black holes, the papers authors propose, might shepherd smaller black holes within them into similar tracks. As in the star clusters, there black holes might eventually converge on multiple occasions.

The researchers created simulations of these orbiting black holes and found that a series of mergers would create black holes that are 50 or more solar masses, like the more massive black hole in the merger GW170729.

The mergers from black holes orbiting a supermassive black hole would probably have rotation characteristics distinct from other merger scenarios. As gravitational wave detectors spot more black hole mergers, their data might be a way to tell whether these oddly large black holes are really createdthis way.

So far, scientists have identified 10 confirmed mergers of black hole pairs. But there have been many more gravitational wave detections that are black hole merger candidates, which scientists are working to confirm.

Whatever questions were asking, were going to have a much, much better handle on answering them within a very short time period, said Imre Bartos, an astronomer at the University of Florida, Gainesville, and one of the authors of the new paper. Its super exciting.

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Huge black holes might have merging baby black holes around them - Astronomy Magazine

Observing the transit of an inner planet requires a telescope with a solar filter that allows viewing the sun without eye damage. The transit appears as a small black dot that slowly moves across the face of the sun. It isnt visible without magnifying the suns image.

The transit of Mercury is a bit like what happens in a solar eclipse. Instead of the moon coming between Earth and the sun, which can entirely block the suns light, Mercury is much farther away, so it blocks only a small fraction (less than half a percent) of the sun. But even though its only a small black dot, its clearly visible with the right telescope.

The historical importance of the transit of Mercury goes back to the 1600s, when Johannes Kepler, famous for his planetary orbital laws, was the first astronomer to predict it. Back then, there was still public controversy about the model of Copernicus, where planets go around the sun, and the older view that the sun orbited Earth. The transit of Mercury was first observed in 1631 by French astronomer Pierre Gassendi, and was irrefutable evidence that Copernicus was right.

In 1677, Edmund Halley, for whom Halleys comet is named, realized that he could use the transit of Mercury to find the distance to the sun. He did that by measuring the time of the start and finish of Mercurys shadow as it went across the sun, and then used the mathematical technique of parallax to calculate the distance. This was a tour-de-force calculation for its time.

Today, the transit of Mercury is more of a curiosity than a groundbreaking scientific event. However, an interesting application of this technique has been applied to look for planets around other stars. The NASA space telescope Kepler made very careful measurements of the brightness of stars, and found periodic times when the brightness dipped by about 1%. Thats expected to happen when an exoplanet orbits the star and comes between that star and the view from Earth. Thousands of exoplanets have been discovered using the method.

The transit of planets can be used as a great teaching moment for amateur astronomers, either young or old. Its one thing to learn about the planetary orbits in a textbook, but another entirely to see a planets shadow move across the sun in real time.

Kenneth Hicks is a professor of physics and astronomy at Ohio University in Athens.

hicks@ohio.edu

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Astronomy: There are lessons to be learned from transit of Mercury across sun - The Columbus Dispatch

Innermost planet Mercury puts on its best morning display of the year for Northern Hemisphere observers from late November to early December. Skywatchers in the British Isles should find a location offering an unobstructed view of the southeast horizon about 45minutes before sunrise to get the best views. This looping animation shows the changing configuration of Mercury, Mars and Virgos brightest star, Spica, from 18November through 3December at dawn. Note the span of a fist at arms length (about 10) for scale, but the Moons apparent size on 24 and 25November has been enlarged for clarity. AN animation by Ade Ashford.Mercurys transit of the Sun on 11November is still fresh in the memory, but it doesnt take long for the innermost planets orbital motion to carry it far enough west of the Sun to be visible low above the southeastern horizon in dawn twilight. Mercury attains its greatest westerly elongation of 20degrees on the UK morning of 28November. In fact, for Northern Hemisphere observers, the remainder of the month into early December offers Mercurys best morning viewing prospects for the entire year.

Any opportunity to get a glimpse of this elusive and fast-moving planet is well worth getting up a little earlier for, particularly when as now you get a chance to see Mars nearby at the same time. As with any observation made in the eastern sky during dawn twilight, timing is everything: you need to view late enough that Mercury gets a chance to rise high enough above the horizon murk, but not so late that impending sunrise makes the sky too bright to see it. (Never look anywhere near the Sun after it has risen.)

Observers in the British Isles need to find a location that offers an unobscured view of the southeast horizon about three-quarters of an hour before sunrise between now and the first week of December. Our interactive online Almanac gives you the time of sunrise for your nearest town or city, so just subtract 45minutes from that.The slim crescent of the 27-day-old waning Moon lies slightly less than 4degrees above magnitude +1.7 Mars at UK dawn on Sunday, 24November 2019, hence the pair will fit in the same field of view of 10 and lower magnification binoculars. On this morning, the Red Planet sits midway between magnitude -0.2 Mercury and first-magnitude star Spica in Virgo. Note that the Moons apparent size has been enlarged for clarity in this illustration. AN graphic by Ade Ashford.Mercury is located in the constellation of Libra for the period illustrated in the animation at the top of the page. The planet lies about 9degrees (almost the span of a fist held at arms length) above the southeast horizon at the optimal viewing time between 23November and the beginning of December. The Red Planet sits midway between Mercury and the first-magnitude star Spica, the brightest in the constellation of Virgo, at UK dawn on 24November.

Magnitude +1.7 Mars remains in Virgo until the morning of 1December when it crosses the constellation border to join Mercury in Libra. Mercury brightens more than fourfold from magnitude +1 to -0.6 during the 18November to 3December observing window. If clear, dont miss the binocular highlights of 24 and 25November at dawn when the old waning crescent Moon lies 4 above Mars and 3 to the lower left of Mercury, respectively.

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See Mercury at its best meet Mars in the dawn sky - Astronomy Now Online

The Institute for Astronomy helped people gathered at Waialae Beach Park to observe the event. PC: University of Hawaii

The planet Mercury did its best Icarus impression last week, and students from the University of Hawai traveled to the Big Island for a chance to witness it.

University of Hawaii astronomers joined many observers around the world in tracking the transit of Mercury on Monday, Nov. 11. A transit is when a planet passes in front of a star. Mercury and Venus are the only two planets that can be observed from Earth in transit.

About 30 UH Mnoa students flew to Hawaii Island to view the event at the Subaru Telescope as part of a group of around 200 people to use solar telescopes.

UH Mnoas Institute for Astronomy held a viewing party at Waialae Beach Park for more than 100 people.

Mercury takes just 88 days to circle the Sun. It passes between the Sun and Earth frequently but usually out of view.

The transit of Mercury will not be seen from Earth again until November 2032, and not from Hawaii until 2049. The next transit of Venus will not be visible from Earth until 2117.

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Astronomy in Transit - Big Island Now

China made history earlier this year when its Chang'e-4 lander became the first spacecraft to land on the far side of the moon. During the two-week lunar days, the lander and its small rover, Yutu 2, beam images and other data to an orbiter for relay back to Earth. Together theyve furnished planetary scientists with unprecedented access to the backside of our Janus-faced neighbor. But not everyone was thrilled that China crossed into this new lunar frontier, and few have been more vocal about their concerns than the scientists involved in the search for extraterrestrial intelligence.

Last month, the SETI permanent committee of the International Astronautical Association hosted its second round of negotiations about the lunar farside in Washington, DC. The exploration of the moon might seem like an issue outside the purview of this group of professional alien hunters, but the far side of the moon is the most radio quiet place in the inner solar system and they want to keep it that way in case ET calls. Indeed, they argue that the fate of the lunar farside may determine whether we ever detect a signal from an extraterrestrial intelligence.

At the moment, SETI is not doomed, but it might be doomed in the next 50 years and thats being optimistic, says Claudio Maccone, an astrophysicist and the chair of the IAA SETI committee. We must insist on this topic while there is still time to do something.

On Earth, radio astronomers must contend with interference from television broadcasts, cell phone signals, satellites, and the atmosphere as they scan the cosmos for faint signals from primordial stars, organic molecules, or intelligent life. This makes the lunar farside an attractive site for future radio telescopes because the moon blocks all the radio signals from Earth. Its like the difference between stargazing in New York City and stargazing in the middle of the desertin the city light pollution obscures almost all of the good stuff.

As a hedge against the unchecked proliferation of radio frequency interference, a radio astronomer named Jean Heidmann made the case for a SETI radio base on the far side of the moon back in the mid-90s. Even before cell phones became common, Heidmann realized that radio interference could eventually become so bad that searching for aliens with radio telescopes would be impossible on Earth. Moving radio observatories to the moon wouldnt require turning the entire lunar farside into a radio quiet zone, but it would guarantee that at least some portions of the moon are preserved for radio astronomy and the hunt for extraterrestrial intelligence.

Here on Earth, governments could create more radio quiet zones like the kind around the National Radio Astronomy Observatory in Green Bank, West Virginia, but even then we might miss a message from ET. The Earths atmosphere starts to block out radio frequencies as you move away from a relatively narrow frequency band called the microwave window, so unless ET happens to be transmitting on one of those frequencies wed struggle to hear it. But the lunar atmosphere is virtually nonexistent, which means radio astronomers would have access to frequencies above and below Earths microwave window. And, given the moons low gravity environment, astronomers would also be able to build massive radio telescopes that dwarf those found on Earth.

After Heidmanns death in 2000, Maccone took up the cause of preserving the lunar farside for radio astronomy. He has written several papers on the subject and even gave a presentation to the United Nations, but until recently his pleas have fallen on deaf ears. The reason, Maccone says, is that the issue lacked any urgency. Most national space agencies had neither the funding nor the will to launch a mission to the far side of the moon and billionaires were still struggling just to get a rocket to orbit.

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Alien Hunters Need the Far Side of the Moon to Stay Quiet - WIRED

Solidity is a function of magnification. We know that anything we experience as solid is actually a structure of atoms packed closely enough that to our eyes they appear to be a single solid thing. If we were small enough, we'd see the spaces between them; if we were even smaller, those spaces might seem vast. Likewise, in 1989 Margaret Geller and John Huchra, analyzing redraft survey data, discovered the immense "Great Wall," a "sheet" formed from galaxies many light years apart. That first large-scale structure is 500 million light-years long, 200 million light years wide, and with a thickness of 15 million light years.

Other gigantic large-scale structures been discovered since sheets, filaments, and knots, with bubble-like voids intersperse among them. They appear to be connected by clouds and filaments of hydrogen gas and dark matter. Though the bodies that comprise the structures are not gravitationally bound to each other the distances between them are too great evidence is piling up that they are linked by something.

Recent observations indicate that galaxies far, far apart are somehow synchronously moving. Something appears to be binding large-scale structures, many light years apart, together after all. Is the currently accepted view of the universe as various clumps of material simply expanding outward from the Big Bang and gravitationally pulling on each other wrong?

The existence and mechanics of large-scale structures are a tantalizing puzzle with obviously major implications for our understanding of the universe. As Noam Libeskind, of the Leibniz-Institut for Astrophysics (AIP) in Germany tells VICE, "That's actually the reason why everybody is always studying these large-scale structures. It's a way of probing and constraining the laws of gravity and the nature of matter, dark matter, dark energy, and the universe."

The identification and study of large-scale structures is a product of analyzing and modeling simulations of redshift survey for specific regions of the sky that visually reveal these immense structures.

The large-scale structures revealed in one segment of sky

Image source: National Center for Supercomputer Applications by Andrey Kravtsov (The University of Chicago) and Anatoly Klypin (New Mexico State University). Visualizations by Andrey Kravtsov.

Several pieces of research are causing interest in these large-scale structures to heat up. The most mind-blowingly distant synchronized motion was reported in 2014, when the rotation axes of 19 super-massive black holes at the centers of quasars out of 100 quasars studied were found to be in alignment, billions of light years apart. According to the study's lead author, astronomer Damien Hutsemkers of the University of Lige in Belgium, "Galaxy spin axes are known to align with large-scale structures such as cosmic filaments but this occurs on smaller scales. However, there is currently no explanation why the axes of quasars are aligned with the axis of the large group in which they are embedded."

The first word of the research paper's title, "Spooky Alignment of Quasars Across Billions of Light-years," invokes cosmic-scale quantum entanglement as a possible explanation.

Image source: orin/Shutterstock/Big Think

Astronomer Joon Hyeop Lee of the Korea Astronomy and Space Institute is the lead author of "Mysterious Coherence in Several-megaparsec Scales between Galaxy Rotation and Neighbor Motion," published in October of this year in Astrophysical Journal. Comparing data from two catalogs of redshift survey data the Calar Alto Legacy Integral Field Area (CALIFA) and NASA-Sloan Atlas (NSA) catalogs the researchers' analysis of 445 galaxies revealed, surprisingly, that galaxies six meparsecs, or 20 million light years, apart were moving in the same way. Those observed, for example, a galaxy moving toward the Earth was mirrored by other distant galaxies moving in the same direction.

"This discovery is quite new and unexpected," according to Lee, "I have never seen any previous report of observations or any prediction from numerical simulations, exactly related to this phenomenon."

Since the galaxies are too distant for their gravitational fields to be influencing each other, Lee poses another explanation: That the linked galaxies are both embedded within the same, large-scale structure.

Image source: sripfoto/Shutterstock/Big Think

Another puzzle suggesting the influence of large-scale structures has become clear over recent years. It's been observed that galaxies surrounding our own Milky Way are weirdly arranged in a single, flat plane. Big-Bang thinking would suggest that they should be circling us at all different sorts of angles. Obviously, for adherents of that way of viewing the galaxy known as the CDM model this at the very least a troubling anomaly.

The hope that it was an anomaly weakened with the discovery of the same thing occurring around the Andromeda galaxy, and then again around Centaurus A in 2015. By the time "A whirling plane of satellite galaxies around Centaurus A challenges cold dark matter cosmology" was published in 2018, the phenomenon was starting to seem quite common, and possibly universal. The idea that the satellite galaxies might part of a large-scale structure had become even worthier of serious consideration.

As more astronomers embrace the notion of large-scale structures and related research accelerates, we can only hope that these perplexingly oddball movements and associations are eventually made clear. Certainly, imagining a vast arrangement of utterly gigantic structures in which galaxies are embedded paints a very different picture of the universe, and one that makes one wonder if these structures are themselves embedded in something even larger. In this mid-boggling case, we are indeed small enough to see only the space between objects in this case galaxies. We've been no more aware of them than whatever it is that may be living between our own atoms.

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Is the universe controlled by gigantic structures? - Big Think

Astronomers have confirmed the first example of a galaxy cluster where large numbers of stars are being born at its core. Using data from NASA space telescopes and a National Science Foundation radio observatory, researchers have gathered new details about how the most massive black holes in the universe affect their host galaxies.

Galaxy clusters are the largest structures in the cosmos that are held together by gravity, consisting of hundreds or thousands of galaxies embedded in hot gas, as well as invisibledark matter. The largest supermassive black holes known are in galaxies at the centers of these clusters.

For decades, astronomers have looked for galaxy clusters containing rich nurseries of stars in their central galaxies. Instead, they found powerful, giant black holes pumping out energy through jets of high-energy particles and keeping the gas too warm to form many stars.

Now, scientists have compelling evidence for a galaxy cluster where stars are forming at a furious rate, apparently linked to a less effective black hole in its center. In this unique cluster, the jets from the central black hole instead appear to be aiding in the formation of stars. Researchers used new data from NASAs Chandra X-ray Observatory and Hubble Space Telescope, and the NSFs Karl Jansky Very Large Array (VLA) to build on previous observations of this cluster.

This is a phenomenon that astronomers had been trying to find for a long time, said Michael McDonald, astronomer at the Massachusetts Institute of Technology (MIT), who led the study. This cluster demonstrates that, in some instances, the energetic output from a black hole can actually enhance cooling, leading to dramatic consequences.

The black hole is in the center of a galaxy cluster called the Phoenix Cluster, located about 5.8 billion light years from Earth in the Phoenix Constellation. The large galaxy hosting the black hole is surrounded by hot gas with temperatures of millions of degrees. The mass of this gas, equivalent to trillions of Suns, is several times greater than the combined mass of all the galaxies in the cluster.

This hot gas loses energy as it glows in X-rays, which should cause it to cool until it can form large numbers of stars. However, in all other observed galaxy clusters, bursts of energy driven by such a black hole keep most of the hot gas from cooling, preventing widespread star birth.

Imagine running an air conditioner in your house on a hot day, but then starting a wood fire. Your living room cant properly cool down until you put out the fire, said co-author Brian McNamara of the University of Waterloo in Canada. Similarly, when a black holes heating ability is turned off in a galaxy cluster, the gas can then cool.

Evidence for rapid star formation in the Phoenix Cluster was previously reported in 2012 by a team led by McDonald. But deeper observations were required to learn details about the central black holes role in the rebirth of stars in the central galaxy, and how that might change in the future.

By combining long observations in X-ray, optical, and radio light, the researchers gained a ten-fold improvement in the data quality compared to previous observations. The new Chandra data reveal that hot gas is cooling nearly at the rate expected in the absence of energy injected by a black hole. The new Hubble data show that about 10 billion solar masses of cool gas are located along filaments leading towards the black hole, and young stars are forming from this cool gas at a rate of about 500 solar masses per year. By comparison, stars are forming in the Milky Way galaxy at a rate of about one solar mass per year.

The VLA radio data reveal jets blasting out from the vicinity of the central black hole. These jets likely inflated bubbles in the hot gas that are detected in the Chandra data. Both the jets and bubbles are evidence of past rapid growth of the black hole. Early in this growth, the black hole may have been undersized, compared to the mass of its host galaxy, which would allow rapid cooling to go unchecked.

In the past, outbursts from the undersized black hole may have simply been too weak to heat its surroundings, allowing hot gas to start cooling, said co-author Matthew Bayliss, who was a researcher at MIT during this study, but has recently joined the faculty at the University of Cincinnati. But as the black hole has grown more massive and more powerful, its influence has been increasing.

The cooling can continue when the gas is carried away from the center of the cluster by the black holes outbursts. At a greater distance from the heating influence of the black hole, the gas cools faster than it can fall back towards the center of the cluster. This scenario explains the observation that cool gas is located around the borders of the cavities, based on a comparison of the Chandra and Hubble data.

Eventually the outburst will generate enough turbulence, sound waves and shock waves (similar to the sonic booms produced by supersonic aircraft) to provide sources of heat and prevent further cooling. This will continue until the outburst ceases and the build-up of cool gas can recommence. The whole cycle may then repeat.

These results show that the black hole has temporarily been assisting in the formation of stars, but when it strengthens its effects will start to mimic those of black holes in other clusters, stifling more star birth, said co-author Mark Voit of Michigan State University in East Lansing, Michigan.

The lack of similar objects shows that clusters and their enormous black holes pass through the rapid star formation phase relatively quickly.

A paper describing these results was published in a recent issue of The Astrophysical Journal, and a preprint isavailable online.

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts. The NASA Hubble Space Telescope is a project of international cooperation between NASA and ESA. AURAs Space Telescope Science Institute in Baltimore, Maryland conducts Hubble science operations. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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Previous A Weakened Black Hole Allows Its Galaxy To Awaken - HubbleSite

A new study, published in the journal Icarus, shows that Naiad and Thalassa, two innermost moons of Neptune, are locked in an unusual type of orbital resonance.

The odd orbits of Neptunes inner moons Naiad and Thalassa enable them to avoid each other as they race around the giant planet. Image credit: Brozovi et al, doi: 10.1016/j.icarus.2019.113462.

Far from the pull of the Sun, giant planets are the dominant sources of gravity, and collectively, they boast dozens upon dozens of moons.

Some of those moons formed alongside their planets and never went anywhere; others were captured later, then locked into orbits dictated by their planets. Some orbit in the opposite direction their planets rotate; others swap orbits with each other as if to avoid collision.

The Neptune system consists of seven regular inner moons, Triton, Nereid, and five irregular outer moons.

Inner moons Naiad and Thalassa were discovered by NASAs Voyager 2 spacecraft during the 1989 flyby of Neptune.

They are about 60 miles (100 km) in length and are true partners, orbiting only about 1,150 miles (1,850 km) apart.

But they never get that close to each other; Naiads orbit is tilted and perfectly timed. Every time it passes the slower-moving Thalassa, the two are about 2,200 miles (3,540 km) apart.

In this perpetual choreography, Naiad swirls around Neptune every seven hours, while Thalassa, on the outside track, takes seven and a half hours.

An observer sitting on Thalassa would see Naiad in an orbit that varies wildly in a zigzag pattern, passing by twice from above and then twice from below.

This up, up, down, down pattern repeats every time Naiad gains four laps on Thalassa. Although the dance may appear odd, it keeps the orbits stable.

Dr. Marina Brozovi, a researcher at NASAs Jet Propulsion Laboratory, and colleagues discovered the unusual orbital pattern using analysis of observations by the NASA/ESA Hubble Space Telescope.

We refer to this repeating pattern as a resonance. There are many different types of dances that planets, moons and asteroids can follow, but this one has never been seen before, Dr. Brozovi said.

So how did Naiad and Thalassa end up together but apart? Its thought that the original satellite system was disrupted when Neptune captured its giant moon, Triton, and that these inner moons and rings formed from the leftover debris.

We suspect that Naiad was kicked into its tilted orbit by an earlier interaction with one of Neptunes other inner moons, Dr. Brozovi said.

Only later, after its orbital tilt was established, could Naiad settle into this unusual resonance with Thalassa.

The study also provides the first hint about the internal composition of Neptunes inner moons.

The scientists used the Hubble observations to compute their mass and, thus, their densities which were close to that of water ice.

We are always excited to find these co-dependencies between moons, said Dr. Mark Showalter, a planetary astronomer at the SETI Institute.

Naiad and Thalassa have probably been locked together in this configuration for a very long time, because it makes their orbits more stable. They maintain the peace by never getting too close.

_____

Marina Brozovi et al. 2020. Orbits and resonances of the regular moons of Neptune. Icarus 338: 113462; doi: 10.1016/j.icarus.2019.113462

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Neptune's Moons Naiad and Thalassa Perform 'Dance of Avoidance' | Astronomy - Sci-News.com

For the past quarter-century, Eric Wilcots has been one of the University of WisconsinMadisons most prominent astronomers.

I love the sense of discovery, he says. We get to discover things. As a scientist I was fascinated by how the universe works: to be able to see things and understand things that other people have not seen, to be able to see them in a different way, to be able to ask really big blue-sky science questions like, How do galaxies change over time? Thats just compelling and fascinating to understand how the universe works and how this planet that we live on got to be here. Its fascinating.

Although astronomy has been his lifes passion, Wilcots is currently providing the leadership for the College of Letters & Science, the largest college at the UW. He has served as the Mary C. Jacoby professor of astronomy, deputy dean, and associate dean for research. On August 5, he became the colleges interim dean when predecessor John Karl Scholz was appointed as the universitys next provost.

We do lots of really good things here, so its an exciting opportunity for me, Wilcots says.

Wilcots has been an important role model and mentor for younger people of color interested in the STEM (science, technology, engineering, and math) fields, which have historically lacked the diversity of the general population.

I think that its so important, Wilcots says. We live in a world in this day and age where we can think of science as driving a lot of what we do. A lot of problems that we wrestle with need to be addressed via science. Yet the scientific community writ large is not tapping the talent that it can. So diversifying the STEM discipline is more than just embracing diversity. Its recognizing that we are shorting ourselves if we are not tapping all of the talent across all populations. To the extent that I can be a role model and to the extent that theres a kid out there who sees someone doing science that kind of looks like me thats wonderful. Im humbled by that.

Wilcots first became fascinated by astronomy as a little boy in Philadelphia.

I got a telescope for Christmas when I was eight or nine, and thats what piqued my interest in astronomy, Wilcots says. I remember watching theVoyager 1[probe] flying by Jupiter for about a week, and there were all these fantastic images coming back from Jupiter. The people looked like they were having fun. I remember thinking, I want to do that! Whatever that was, I wanted to be a part of it.

Wilcots spent a couple of years working at the Franklin Institute Science Museum in Philadelphia, one of Americas most celebrated museums.

The observatory was my favorite place to be in that building, Wilcots remembers.

Wilcots went on to earn his bachelors degree in astrophysics at Princeton University in 1987 and a PhD in astronomy from the University of Washington in 1992. From 1992 to 1995, he was a Karl Jansky Postdoctoral Fellow at the National Radio Astronomy Observatory in Socorro, New Mexico, before coming to UWMadison.

I came here in 95. The intellectual curiosity that I see is invigorating. I love that kind of environment, Wilcots says. We have fantastic students who come through who are remarkable and inspiring in their own way. We have students who could have gone [to college] anywhere, and they decided to come here. Wisconsin is a great place to be.

Wilcotss research interests focus on understanding the evolution of galaxies and galaxy groups, primarily through observations of radio wavelengths, and he loves sharing the process of discovery with UW students.

Ive had a fantastic set of graduate students over the years and an equally fantastic group of undergraduates that Ive worked with. To be able to have a student come in who is unfamiliar with the discipline but then come out of that process with that sense of discovery themselves, thats pretty cool, he says. Working with students is a fun part of the job. I would not want to be an astronomer and not want to work with students.

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"I Love the Sense of Discovery." Dr. Eric Wilcots Stays Focused on Science as he Ascends Academic Ladder - madison365.com