Monthly Archives: March 2020

Astronomers have discovered a bizarre exoplanet that rains iron at night. The daytime side of this world, dubbed WASP-76 b, isnt any less hellish, either. Temperatures can reach up to 4,300 degrees Fahrenheit (2,400 degrees Celsius) hot enough to vaporize metal.

One could say that this planet gets rainy in the evening, except it rains iron, University of Geneva astronomer David Ehrenreich, who led the new study, said in a press release.

WASP-76 b is slightly smaller than Jupiter and sits some 640 light-years from Earth in the constellation Pisces. Its horrifying weather is caused by its truly extreme orbit. Gas giant worlds like WASP-76 b are called hot Jupiters because they orbit uncomfortably close to their home stars in this case, nearly 10 times closer than Mercury is to our Sun.

That proximity leaves WASP-76 b tidally locked to its star, with one side permanently baking in light and the other stuck in eternal darkness.

WASP-76 bs daytime side gets hit with thousands of times more radiation than Earth receives from the Sun. And this scorching radiation vaporizes iron on the dayside. Winds driven by extreme temperature differences then push the metal around the planet to the nighttime hemisphere. There, drastically cooler temperatures let the iron condense into drops and fall as a strange rain.

Surprisingly, however, we dont see iron vapor on the other side of the planet in the morning, University of Geneva researcher Christophe Lovis said in a media release. The conclusion is that the iron has condensed during the night. In other words, it rains iron on the night side of this extreme exoplanet.

Its the first time astronomers have detected this kind of day-to-night chemical difference on a hot Jupiter like WASP-76 b.

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Astronomers find an exoplanet where iron rains from the sky - Astronomy Magazine

The four fundamental forces

Physics textbooks teach that there are four fundamental forces of nature: gravity, electromagnetism, and the strong and weak nuclear forces.

Were quite familiar with the first two forces. Gravity pins us to Earth and pulls us around the sun, while electromagnetism keeps the lights on. The other two forces are less obvious to us because they govern interactions at the tiniest scales. The strong force binds matter together, while the weak nuclear force describes the radioactive decay of atoms.

Each of these forces is carried by a kind of subatomic particle that physicists call a boson. For example, photons are the force particle in electromagnetism. Gluons carry the strong nuclear force. W and Z bosons are responsible for the weak nuclear force. Theres even a hypothetical boson for gravity called the graviton, though scientists havent proven its existence.

However, if you ask many theoretical physicists, theyll probably tell you we havent discovered all the forces of nature yet. Others are likely out there, just waiting to be discovered.For example, some suspect that discovering dark matter may reveal a weak new force.

And thats where the Hungarian group comes in. Without getting too lost in the details, the group shot protons at a thin sample of lithium-7, which then radioactively decayed into beryllium-8. As expected, this created pairs of positrons and electrons. However, the detectors also picked up excess decay signals that suggested the existence of a potential new and extremely weak particle. If it exists, the particle would weigh in at about 1/50 the mass of a proton. And because of its properties, it would be a boson a force-carrying particle.

But history is littered with reasons to be skeptical of new additions. In recent decades, other groups have also claimed to have found a fifth force, only to have their claims quietly fade away. Around the year 2000, one group proposed a new force, called quintessence, to explain the then-recent discovery of dark energy. In the 1980s, a group of physicists at MIT said theyd found a fifth force, dubbed hypercharge, that served as a kind of anti-gravity. Yet here we are with textbooks still teaching the same four fundamental forces we had decades ago.

That means the most likely explanation for the unexplained new signal is that theres something off with the Hungarian detectors setup. However, no one is disputing the data. The findings were peer-reviewed and published in the journal Physical Review Letters the same journal that published the discovery of gravitational waves. Even ideas in prestigious journals can sometimes be explained away as systematic error, but thats the way science works.

People are paying attention to see whether this is really a nuclear physics effect or whether its something systematic, Alves says. Its important to repeat those experiments ... to be able to test whether this is real or if its an artifact of the way theyre doing the experiment.

Quest to confirm

And thats precisely what her group hopes to do. Together with a small team, shes proposing to repeat the Hungarian experiment using equipment that already exists at Los Alamos. The national lab has been a leader in nuclear physics since the creation of the atomic bomb. And today, thousands of top physicists still work there on problems ranging from safeguarding and studying our nations nuclear arsenal, to pioneering quantum computers and observing pulsars.

As it turns out, they also have a detector nearly identical to the one used by the Hungarian team.

When you add all that together, Alves believes Los Alamos has exactly the right combination of facilities and expertise to repeat the experiment. Thats why her group quietly worked on their proposal for the last six months, and recently submitted a funding request for review. To gain approval, it will have to win out in an annual competition alongside other projects at the national lab.

In recent years, several other groups likewise have suggested theyll look for this force. But at the moment, Alves believes they're the main group in the U.S. working to confirm or refute the finding. If they cant gain approval, it may be years before a university or other group can secure both the funds and expertise to repeat the experiment with the same sort of parameters the Hungarians used.

As with all extraordinary claims, this potentially paradigm-shifting discovery will require extraordinary evidence before people accept it. So we may have to wait a while before we know whether the X17 particle and its potential fifth force will revolutionize physics, or take its place atop the dustbin of debunked and discarded discoveries.

Original post:

The fifth force: Is there another fundamental force of nature? - Astronomy Magazine

Friday, March 6A waxing Moon hangs out in Cancer the Crab all night. About 18 to its west is yellowish Pollux in Gemini, and nearly 4 farther is the whiter-hued Castor. The latter appears to the naked eye as a magnitude 1.6 star, but it is actually a six-star system. The two brightest stars, Castor A and B, can be separated with a small telescope.A third component, the dimmer Castor C, lies about 1.2' away.

Saturday, March 7Night owls can take a gander at one of the best globular clusters visible in the Northern Hemisphere. Messier 13, also known as the Hercules Cluster, rises above the horizon with its namesake constellation about 9 P.M. local time but is well poised for clearer viewing by midnight and into the early hours of the morning. This cluster of ancient stars circling our galaxy contains more than 100,000 members that combine to create its magnitude 5.8 glow.

Sunday, March 8Venus and Uranus lie just over 2 apart in the evening sky. You can use Venus to easily find the ice giant by using binoculars or a telescope to locate a pair of 7th-magnitude stars about 1.2 to the lower left of Venus. Travel twice that distance in the same direction to reach brighter Uranus, glowing at magnitude 5.9.

Neptune is in conjunction with the Sun at 8 A.M. EDT. However, its position means it is lost from view in the bright glare of our star. It will make its way back to visibility by the end of next month.

For most of the United States and Canada, daylight saving time begins at 2 A.M. local time this morning. Set your clocks ahead one hour.

Monday, March 9Venus passes 2 north of Uranus this morning at 11 A.M. EDT. The inferior planet will continue to move noticeably through Aries as March progresses, while the more distant ice giant moves only about 1 eastward during the month.

Mercury is stationary at 4 A.M. EDT. From here, it will move toward its greatest western elongation, which it will reach on the 23rd.

The Full Moon occurs at 1:48 P.M. EDT. This evening, our satellite rises in Virgo as the Sun is setting and will set in the morning around dawn. Full Moon is an excellent time to easily observe Luna with or without additional optical assistance; keep in mind that the Moon will appear especially bright through binoculars or a telescope. The Full Moon also washes out much of the sky, making this time best for observing planets and brighter stars, but poor for deep-sky objects such as galaxies and nebulae.

Tuesday, March 10The Moon reaches perigee, its closest point to Earth in its orbit, at 2:30 A.M. EDT. At that time, it will sit 221,905 miles (357,121 kilometers) from our planet.

When the Full Moon occurs at perigee, it is sometimes called a supermoon by the media. Although this is an evocative name, the Full Moon will only appear about 7 percent larger than average, which is difficult if not impossible for observers to discern.

Excerpt from:

The Sky This Week from March 6 to 13 - Astronomy Magazine

Hold on, a quick aside. When you say the word billion on the show, I feel like you think for a moment before you pronounce it. Were you careful in how you said the word billion, not to sound too much like Carl Sagan?

[laughs] You know, you can't step into a Sagan slot and not be conscious of the number billion. There were a couple of times I would punch it up a notch, almost as an homage, but otherwise not. I do remember a couple of times when I didn't think the editors would use those cuts where I went high on the intonation scale.

Sorry, back to our conversation. Many people who think about the future of humanity imagine us someday merging with computers. Does that seem credible to you?

No, not really. And I know I'm an outlier here. It doesn't feel credible because, you know, I have in my palm access to the internet. So you're saying, "Oh, now I'm going to wire that with a USB connection into my brainstem." How fast access am I going to want? Is it not fast enough to pull this phone out of my pocket? For me, the fact that it is right with me every day I leave the house, that doesn't leave me wanting this thing to be surgically connectedto get silicon surgically connected to my physiology.You dont crave more speed, more connection to information?

Heres a related analogy. Air transportation, in its early decades, was about how fast can you fly to your destination, how to minimize the time you're on an airplane. So planes got faster and faster. We got to jets instead of propellers, and then we got the supersonic transport. Then things started pulling back. Why? Well we had the 747. Planes got larger, they had better food, they had more leg room. The seats were more comfortable. Today we have the internet on your flight, we have any movie you'd ever want to watch, we have music.

The idea that speed was so important that we would want it at all costs gave way to a different idea: I am comfortable in this environment, and in fact I can even catch up on things. I can binge on shows I didn't have time to watch at home. You can come off the plane in a better place than you were before you entered it. And so no one is trying to make planes faster today. In fact, they're slower than before. The typical speeds are 500 to 550 miles per hour, whereas when I was growing up, the speeds were 600 to 650 miles per hour.

So to say we're going to become one with artificial intelligence because we want the speed, I just don't see that happening.

A lot of people also dream that computer technology will bring us immortality. Thats a possible world they long for: We will upload our brains, and then we'll never die.

Well, I would ask, if you upload your brain, how do you know that's still you? I don't think we understand consciousness enough to assert that. We can say that's your knowledge. That thing, that entity has all the same knowledge that you have, but is that you? I don't know.

We know that an identical twin has identical DNA to you yet they are not you. You don't have their thoughts and they don't have your thoughts. So this notion of uploading your consciousnessI'm not going to pay close attention to it until we have a secure understanding of what consciousness is in the first place.

That's a whole other mysterious world, the mental world that is still barely being explored.

Right. Its a frontier perhaps as vast as the universe itself.

Excerpt from:

Get ready to explore the "Cosmos" with Neil deGrasse Tyson - Astronomy Magazine

Are we alone in the Universe? The expert opinion on that, it turns out, is surprisingly consistent.

Is there other life in the Universe? I would say: probably, Daniel Zucker, Associate Professor of astronomy at Macquarie University, tells astrophysics student and The Conversations editorial intern Antonio Tarquinio on todays podcast episode.

I think that we will discover life outside of Earth in my lifetime. If not that, then in your lifetime, says his fellow Macquarie University colleague, Professor Orsola De Marco.

And Lee Spitler, a Senior Lecturer and astronomy researcher at the same institution, was similarly optimistic: I think theres a high likelihood that we are not alone in the Universe.

The big question, however, is what that life might look like.

Read more: The Dish in Parkes is scanning the southern Milky Way, searching for alien signals

Were also hearing from Danny C Price, project scientist for the Breakthrough Listen project scanning the southern skies for unusual patterns, on what the search for alien intelligence looks like in real life - and what its yielded so far.

Read more: 'The size, the grandeur, the peacefulness of being in the dark': what it's like to study space at Siding Spring Observatory

Everything you need to know about how to listen to a podcast is here.

Additional audio credits

Kindergarten by Unkle Ho, from Elefant Traks.

Lucky Stars by Podington Bear, from Free Music Archive

Illumination by Kai Engel, from Free Music Archive

Podcast episode recorded and edited by Antonio Tarquinio.

Shutterstock

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We asked astronomers: are we alone in the Universe? The answer was surprisingly consistent - The Conversation AU

Get your friends together for Friends trivia this Tuesday

Think you have the unagi to participate in Friends Trivia at Reginellis Pizzeria Tuesday, March 10? Well, get your gang of one to six people together as you compete for Reginellis gift cards. And as always, the best team name wins a free pitcher of NOLA Blonde. Could you be any more excited? If so, be sure to share plenty of food while youre at it, too, because we all know Joey doesnt share food!

Reginellis Pizzeria (Goodwood) is at 684 Jefferson Highway.

Head over to Bin 77 Bistro & SideBar as the restaurant features Single Vineyard wines of the Hartford Court Family Winery on Tuesday, March 10. Besides two flights of white and red wine, there will also be plenty of chef and sommelier boards, starting at 7 p.m., which will include various cheeses, charcuteries and cooked proteins to go with the wines.

To make a reservation, call Bin 77 at 763-2288.

Bin 77 Bistro & SideBar is at 10111 Perkins Rowe, Ste. 160.

Curious about whether or not Experiment 626 and Chewbacca could exist, and what their lives might be like? You and your kids can find out as Astronomy on Tap celebrates its second anniversary Wednesday, March 11. LSU grad student Rachel Malacek will talk about the possible adventures of Stitch (from Lilo and Stitch), and fellow grad student Aaron Ryan will discuss the life of Chewbacca.

There will be plenty of games, raffles, glow sticks and spaced-themed drinks for everyone, too.

The Varsity Theatre is at 3353 Highland Road.

Need to wine down? Join Rouj Creole Wednesday, March 11, as the new restaurant hosts another wine dinner. You can enjoy the chefs four-course meal, included with a Duckhorn wine pairing, 6:30-9:30 p.m.

To make a reservation, call Rouj at 614-2400.

Rouj Creole is at 7601 Bluebonnet Blvd., Ste 100.

Join Red Stick Spice Co. as its team teaches you how to demystify pantry staples with Middle Eastern foods Thursday, March 12. You can look forward to tahini cookies, roasted eggplant, pomegranate molasses and more, 6-8 p.m.

This class is available for those 16 and older. Tickets are available here.

Red Stick Spice Company is at 660 Jefferson Highway.

Read the original here:

Dine Roundup: Wine dinners, Astronomy on Tap and more in Baton Rouge this week - 225 Baton Rouge

On Friday, 6th March 2020, at the Women Development Center Calabar, the Learnspace Foundation, a non-governmental organization registered under the Corporate Affairs Commission (CAC) of Nigeria, hosted the 1st Space Science and Astronomy competition in Cross River State in Nigeria, the theme being: The benefits of space science and astronomy education in Nigeria. The competition was open to students in secondary schools in Calabar.

The President of the Foundation Nelly-Helen Ebruka explained that the Foundation is dedicated to promoting and increasing knowledge and interest in Space through space education in Africa. The Foundation also aims to create opportunities for African students to take an active part in the Space industry.

A trustee of the Foundation Ms Anne Agi while speaking to Space in Africa, noted that the aim of the competition is to promote the interest, involvement and knowledge of space science and astronomy among students by providing a fair and competitive environment for learning, interacting and the understanding of space science and astronomy. She added that the competition further encourages the development of space science as well as strengthen the inclusion of Science, Technology, Engineering and Maths (STEM) in the curriculum of academic institutions.

A total of ten schools in Calabar were in attendance at the Competition, however, nine schools participated in the competition. These schools were: Lourdes Academy, Berith Academy, Hillcrest High School, St. Patricks College, Christian High School, Government Secondary School Akim, Federal Airport Authority of Nigeria Secondary School, Hope Waddell Training Institute and Margaret Ekpo Secondary school.

Participating schools partook in a quiz, poetry and public speaking competition. The quiz segment was open to a total of three participants from each school with Lourdes Academy emerging as the winners, St. Patricks College was the 1st runners up and Hillcrest secondary school placed as the 2nd runners up. These positions were not only determined by their participation in the quiz but also by the cumulative scores obtained during the public speaking portion of the competition.

The poetry competition entitled If I Could Walk On The Moon, was open to only female students, with each school entitled to one participant. All participating schools submitted their written poems and the too 3 were selected to compete orally. The poem presentations, were judged by Mr Augustine Ushie, a co-trustee and founder of the foundation, along with a panel of judges. Miss Agan Grace Ripeh from Lourdes Academy was recognized as the winner; Miss Precious Ali from Federal Airport Authority of Nigeria Secondary School secured the 1st runner up position, while Miss Rosseta Tegan from Christian High School placed as 2nd runner up.

The Competition prizes included plaques, participation certificates, writing materials and cash prizes; the Coaches, Institutions and all participating students were also presented with certificates of participation by a representative of the Director of Schools, Ministry of Education, Cross River State.

The Competition also hosted a lecture segment on the theme of the Competition: The benefits of space science and astronomy education in Nigeria. Papers were presented by Mrs Iroka Chidinma Joy, the Chief Engineer, Engineering and Space Systems Division of the National Space Research and Development Agency (NASRDA) and by Ms Anne Agi.

The Competition was a huge success and the spirit of enthusiasm exhibited by the team and all volunteers was infectious. When Space in Africa spoke to a few of the trustees and volunteers, they expressed delight at being a part of history. Mr Timothy Ogar, head of the Quiz Faculty, stated that he was impressed by the students as it was clear that they studied for the Competition and were knowledgeable on space history and surrounding affairs. He maintained that it was obvious that the aim of the competition had been achieved.

President of the Foundation, Ms Nelly-Helen Ebruka assured that the Competition will be held annually as the Foundation believes that Space education is essential to the development of the society. She sincerely thanked the Foundations team of volunteers.

Following this event, Space in Africa spoke to Ms Nelly-Helen Ebruka, the Founding President, to learn more about the Foundation.

LSF is a non-governmental and non-profit organization registered under the Corporate Affairs Commission Of Nigeria with interest in Space science and Astronomy Education across Africa for the benefit of the community and desired growth of Africa.

It was established in November 2019 after the Team representing Africa at the Manfred Lachs Competition returned from the competition in Washington D.C. Members of the Team came together and agreed to form a Foundation committed to training future leaders all around Nigeria and Africa to become global players in the space industry and to make a positive impact in the society.

The originating members of the team behind its establishment include Nelly-Helen Ebruka-President/Trustee/Co-Founder; Anne Agi, Esq-Trustee/Co-Founder; Augustine Ushie-Trustee/Co-Founder; And Engr. Etim Offiong -Trustee/Co-Founder.Other members of the Board of Trustees include Thankgod Egbe, Joshua Faleti, Timothy Ogar and Abraham Eni.

Our first goal is to become a pan-African organization dedicated to increasing space exploration, innovation and technology on the continent through space science and astronomy education. Secondly to develop an enabling environment for the advancement of STEM and space education and industry in Africa.

The international womens day was recently celebrated globally and it was a period to reflect on the remarkable achievements of women who dared, who gave, who lived for others. In my opinion, young women in STEAM should dedicate more time and energy in developing themselves professionally and personally. The goal should be excellence and nothing short of it. I understand that certain stereotypes about women still exist, in this age however, gender becomes irrelevant if you create the value and make the impact the world needs.

With regards to their prospective activities, the Foundation is open to partnerships, collaborations and sponsorship. With their level of enthusiasm and engagement, support from major stakeholders and players in the space industry and the general community would stimulate an interest in space education not only in Nigeria but the entire continent. Such initiatives have a direct bearing on the human capital development of the future African Space industry and the work of the LearnSpace Foundation is highly commended.

Excerpt from:

LearnSpace Foundation Holds Maiden Space Science And Astronomy Competition In Nigeria - Space in Africa

Observations of the star Betelgeuse taken by the ESOs Very Large Telescope in January and December ... [+] 2019, which show the stars substantial dimming.

Astronomers expect Betelgeuse to explode as a supernova within the next 100,000 years, when its core collapses. However, evidence is mounting that the stars dimming, which began in October, isnt necessarily a sign of an imminent explosion.

A new paperaccepted to Astrophysical Journal Letters and published on the preprint site arXiv entitled Betelgeuse Just Isn't That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse by Emily Levesque, a UW associate professor of astronomy, andPhilip Massey, an astronomer with Lowell Observatory, suggests that Betelgeuse isnt dimming because its about to explode.

Its just dusty.

Astronomers have been on alert since late in 2019 when Betelgeusefound in the constellation of Orionbegan to visibly dim, eventually dropping to around 40% of its usual brightness before slightly brightening in recent weeks.

Could it be about to explode as a massive supernova?

Probably not. Levesque and Massey made optical spectrophotometry observations of Betelgeuse on February 14, 2020 at Lowell Observatory in Flagstaff, Arizona, to calculate the average surface temperature of the red supergiant star. Their results indicate that Betelgeuse is significantly warmer than expected if the recent dimming were caused by a cooling of the stars surface.

This evidence suggests that Betelgeuse has probably sloughed off some material from its outer layers, something that is common with red supergiant stars. We see this all the time in red supergiants, and its a normal part of their life cycle, said Levesque. Red supergiants will occasionally shed material from their surfaces, which will condense around the star as dust. As it cools and dissipates, the dust grains will absorb some of the light heading toward us and block our view.

The first direct image of a star other than our sun, taken with the Hubble Space Telescope. ... [+] Betelgeuse is an enormous star in the constellation Orion. This ultraviolet image shows a bright spot on the star that is 2000 degrees centigrade hotter than the rest of the surface. The picture on the right shows the constellation Orion, with Betelgeuse marked by a yellow cross. The star's size relative to the earth's orbit is also shown. (Photo by CORBIS/Corbis via Getty Images)

How do you take a stars temperature?

The astronomers calculated Betelgeuses temperature by looking at the spectrum of light emanating from it. Emily and I had been in contact about Betelgeuse, and we both agreed that the obvious thing to do was to get a spectrum, said Massey. I already had observing time scheduled on the 4.3-meter Lowell Discovery Telescope, and I knew if I played around for a bit I would be able to get a good spectrum despite Betelgeuse still being one of the brightest stars in the sky.

They looked for the telltale signs of light that had been absorbed by titanium oxide, which forms in the upper layers of large, relatively cool stars like Betelgeuse. By their calculations, Betelgeuses average surface temperature on February 14 was about 3,325 Celsius/6,017 Fahrenheit.

Thats only 50-100 Celsius cooler than calculated in 2004.

Orion rising behind the iconic Hoodoos on Highway 10 east of Drumheller, Alberta, near East Coulee, ... [+] on a moonless January night, with illumination by starlight and by a nearby yardlight providing some shadows and warmer illumination. Clouds are beginning to move in and are providing the natural star glows. (Photo by: Alan Dyer /VW PICS/Universal Images Group via Getty Images)

Orion rising behind the iconic Hoodoos on Highway 10 east of Drumheller, Alberta, near East Coulee, ... [+] on a moonless January night, with illumination by starlight and by a nearby yardlight providing some shadows and warmer illumination. Clouds are beginning to move in and are providing the natural star glows. (Photo by: Alan Dyer /VW PICS/Universal Images Group via Getty Images)

So, not much has changedand dimming should be ruled-out. A comparison with our 2004 spectrum showed immediately that the temperature hadnt changed significantly, said Massey. We knew the answer had to be dust. The theory is that newly formed dust is absorbing some of Betelgeuses light. The other possibility is that huge convection cells within Betelgeuse had drawn hot material up to its surface, where it had cooled before falling back into the interior. A simple way to tell between these possibilities is to determine the effective surface temperature of Betelgeuse, said Massey.

However, if youre hoping to see Betelgeuse go supernova and shine brightly day and night for weeks or months, keep looking. Red supergiants are very dynamic stars, said Levesque. The more we can learn about their normal behaviortemperature fluctuations, dust, convection cellsthe better we can understand them and recognize when something truly unique, like a supernova, might happen.

Wishing you clear skies and wide eyes.

Link:

Now Whats Going On With Betelgeuse? The Future Supernova Just Isnt That Cool, Say Astronomers - Forbes

Now, it seems that every time scientists make a new discovery about Mars, the conversation quickly shifts to: When are we going to go there and see for ourselves? With the upcoming Mars 2020 mission, scientists are finally taking the first steps toward exploring the Red Planet in person.

Planned for launch between July 17 and August 5, Mars 2020 will embark on a roughly seven-month journey to the Red Planet, arriving February 18, 2021. And once engineers confirm its landed safe and sound, Mars 2020 will set to work achieving its four main objectives.

Theres plenty of overlap between Mars 2020s goals and those of previous rovers, but Mars 2020 still has a unique agenda. Namely, Mars 2020 will seek signs of past life by searching for sites that were once habitable; hunt for evidence of ancient microbes at those sites by studying rocks known to preserve life; collect and store rock cores for a future sample return mission; and help scientists prepare for the hurdles human explorers will face on Mars, partly by testing a method for pulling oxygen out of thin air.

But first, the newly named rover has to get to the Red Planet.

View post:

The rover formally known as Mars 2020 - Astronomy Magazine

Neutron stars are the remains of massive stars after they go supernova; while the outer layers of the star explode outward creating fireworks literally on a cosmic scale, the core of the star collapses, becoming incredibly compressed. If the core has enough mass it'll become a black hole, but if it's shy of that limit itll become an ultra-dense ball made up mostly of neutrons.

The stats for neutron stars are sobering. They have a mass of up to over twice the Sun, but the density of an atomic nucleus: Over 100 trillion grams per cubic centimeter. That's hard to grasp, but think of it this way: If you compressed every single car in the United States into neutron-star-stuff, youd get a cube 1 centimeter on a side. The size of a sugar cube, or a six-sided die. All of humanity compressed into such a state would be less than twice that width.

Neutron stars have a surface gravity hundreds of billions times Earth's, and magnetic fields even stronger. A neutron star half the galaxy away from us had a seismic event on it that physically affected us here on Earth, 50,000 light years distant.

Everything about neutron stars is terrifying. But for all that, we're still not exactly sure how big they are.

I mean, we have a rough idea, but the exact number is difficult to determine. They're too small to see directly, so we have to infer their size from other observations, and those are plagued with uncertainties. Their size also depends on their mass. But using observations of X-rays and other emission from neutron stars, astronomers have found they have a diameter of 2030 kilometers. That's tiny, for such a huge mass! But it's also an irritatingly large range. Can we do better?

Yes! A group of scientists have approached the problem in a different way, and have been able to narrow down the size of these fierce but wee beasts: They found that, for a neutron star with a mass of 1.4 times the Sun (about average for such things), it will have a diameter of 22.0 kilometers (with an uncertainty of +0.9/-0.6 km). They find their calculation is a factor of two more accurate than any others done before.

That's small. Like, really small. I'd consider 22 km a short bike ride, though to be fair doing it on a neutron star would be difficult.

So how did they get this number? The physics they employed is actually fiendishly complicated, but what they did in effect was solve a neutron star's equation of state the physical equations that relate characteristics of an object like pressure, volume, and temperature to get what the conditions would be like for a model neutron star with the mass fixed at 1.4 times that of the Sun.

They then used those results and compared them against observations of an event from 2017: A merger of two neutron stars that resulted in a colossal explosion called a kilonova. This event, called GW170817, was a huge watershed moment for astronomy, because the colliding neutron stars emitted powerful gravitational waves, literally shaking the fabric of the Universe. This was our first alert to the event, but then a large fraction of telescopes on and above the Earth aimed at the part of the sky where the merger was found to be, and saw the explosion itself, the kilonova. It was the first time an event was seen emitting electromagnetic energy (that is, light) that was first seen in gravitational waves.

It also put a lot of constraints on the neutron stars that collided. For example, after they merged they emitted light in a specific way, and it turns out that was inconsistent with the merged remnant having enough mass to collapse directly into a black hole. That happens around 2.4 times the Sun's mass, so we know the two stars together had less mass then that. Conversely, the light was inconsistent with the remnant being a neutron star well below that limit, too. It looks like a "hypermassive" neutron star was formed near that limit, lasted for a very short time, and then collapsed into a black hole.

All of this data was fodder for the scientists calculating the neutron star size. By comparing their models with the data from GW170817, they were able to greatly reduce the range of sizes that made sense, zeroing in on the 22 km diameter.

This size has interesting implications. For example, one thing the gravitational wave scientists are hoping to see is the merger of a black hole and a neutron star. This will definitely be detectable, but the question is will it emit any light that more traditional telescopes can see? That happens when material from the neutron star gets ejected during the merger, generating a lot of light.

The scientists in this new work ran the numbers, and found that for a neutron star of 1.4 solar masses and 22 km diameter, any black hole bigger than about 3.4 times the mass of the Sun would not eject any material! That's a very low mass for a black hole, and it's very unlikely we'd see any that low mass, especially one with a neutron star it can eat. So they predict this event will only be seen in gravitational waves and not light. On the other hand, thats only for non-spinning black holes, and in reality most will have a rapid spin; it's unclear what would happen there, but I imagine a lot of folks will be running their models again to see what they can predict.

Having the size of a neutron star means being able to better understand what happens as they spin, as their ridiculously powerful magnetic fields affect material around them, how they accrete new material, and what happens near the mass limit between a neutron star and a black hole. Even better, as the LIGO/Virgo gravitational wave observatory folks fine-tune their equipment they expect their sensitivity to increase, allowing better observations of neutron star mergers, which can then be used to tighten the size constraints even more.

I've been fascinated by neutron stars my whole life, and to be honest that's the correct attitude. They're leftovers from supernovae; they collide and make gold, platinum, barium, and strontium; they are the powerhouse behind pulsars; they can generate mind-crushing blasts of energy; and are the densest objects you can still consider to be in the Universe (the physical object inside a black hole's event horizon is forever beyond our reach). I mean, c'mon. They're amazing.

And that about sizes them up.

Continued here:

How big is a neutron star? - SYFY WIRE