Category Archives: Astronomy

Combining various observational data of neutron-star collisions with nuclear physics calculations, an international team of scientists, including University of Minnesota Twin Cities researchers, has made a breakthrough in discovering the mysteries of what is inside neutron starsformed when certain types of stars die in supernova explosions. Studying this dense matter gives new insight into measuring the expansion rate of our Universe.

Their results are published in the journal Science, a premier peer-reviewed academic journal of the American Association for the Advancement of Science.

In modern astrophysics, scientists combine different types of signals from space, in particular light, cosmic particles, and gravitational waves, to answer fundamental questions of cosmic history. This method of multi-messenger astronomy is a rapidly growing field. The cosmic messengers in the electromagnetic spectrum of light include gamma rays, ultraviolet, visible, infrared, and radio. Cosmic particles can be electrons, protons, neutrinos, complex atomic nuclei, and more. Finally, gravitational waves are tiny ripples in the fabric of space-time itself generated by accelerated masses such as neutron stars or black holes, which emerge from dying stars after the end of their lives.

Colliding neutron stars produce most of the heavy elements in the periodic table, and they allow for measuring the expansion rate of our Universe. By studying colliding neutron stars, astronomers can depict the properties of matter at very high densities, exceeding the density inside atomic nucleimatter for which a single teaspoon of material would weigh an inconceivable several million tons. Black holes are the only thing denser, but they have so fully escaped the bounds of normal physics that they are not matter anymore.

To unravel the mysteries of the underlying physical processes during neutron star collisions, researchers from the United States, Germany, the Netherlands, Sweden, and France incorporated observations of neutron-star collisions with these signals both across the full electromagnetic spectrum and in gravitational waves.

This work constitutes the most extensive analysis to date of the famous gravitational wave named GW170817 discovered in 2017. With contributions from nuclear physics, gravitational-wave astrophysics, optical and gamma-ray astronomy, we address two fundamental problems in physics todaythe expansion rate of the Universe and equation of state of neutron stars, said Michael Coughlin, a University of Minnesota Twin Cities physics and astronomy assistant professor and co-author of the study. Coughlin led the optical data analysis and generation of the surrogate kilonova models.

The research team developed an interdisciplinary framework combining the observations with theoretical nuclear physics calculations to extract astrophysical information on these systems and matter under extreme conditions.

With our method, we were able to constrain the size of a typical neutron star to be about 12 kilometers (a neutron star is an object with the size of a single city), but with a mass several hundred thousand times the mass of the Earth, said Tim Dietrich, a professor oftheoretical astrophysics at the University of Potsdam in Germany.

Further, the team used the extracted astrophysical information to determine the Hubble constant, a fundamental constant that describes the expansion of the Universe.

In the last few years, the scientific community tried to resolve tension among different determinations of the expansion rate of our Universe, said Ingo Tews, staff scientist at Los Alamos National Laboratory and co-author of the study. Our new framework allowed us to re-measure the Hubble constant, and the final results show a mild preference for the previous Cosmic Microwave Background measurement.Starting from theoretical input that describes the nuclear matter in the core of neutron stars, the researchers analyzed astronomical data in a multi-step procedure.

We included neutron-star mass measurements through radio observations, the observation of a rapidly spinning neutron star, and observations of neutron star mergers via gravitational waves and electromagnetic signatures, Dietrich explains. For the latter, we scanned the entire frequency spectrum ranging from the radio band to gamma-rays.

The developed framework is general and can easily be extended to detect more multi-messenger signals in the coming years, he said.

To read the research paper entitled Multi-messenger constraints on the neutron-star equation of state and the Hubble constant, visit the Science website.

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Colliding stars reveal fundamental properties of matter and space-time - UMN News

In the coming nights, Thacher explains, two of the brightest objects in the skySaturn and Jupiterare getting closer and closer and closer together.

On Monday, Dec. 21, the night of the winter solstice, the two planets will be closer together than they have been in 800 years, forming a single, bright object that some are referring to as a Christmas star.

It should be an amazing sight! Thacher exclaims.

The Smith College senior laboratory instructor, who has written dozens of articles introducing young people to scientific concepts, is the author of a new book, Sky Gazing, published this fall by Storey Publishing.

Building on her book, Thacher offers these tips for viewing the once-in-a-lifetime December 21 Saturn/Jupiter conjunction:

Illustration by NASA/JPL-Caltech

But dont stop watching after Monday! Thacher adds.

In the nights after December 21, these two planets will still appear very bright, and well be able to watch them moving apart from each other before they disappear behind the Sun in mid-January. (Stars are constantthey stay in one position relative to each other, even as they rise and set, Thacher notes. But its cool to be able to see planetslike Saturn and Jupitermove around among the stars.)

And in January, star gazers will be able to see the Orion constellationwhich is easily recognizable, and very brightand use it to find five nearby constellations: Canis Major, Canis Minor, Gemini, Auriga, and Taurus.

Thacherwho fell in love with astronomy because of two great teachershopes that Mondays celestial spectacle might help introduce young peopleand adults, tooto the joys available in the stars and planets, and the other wonders of the night sky. And thats the goal of her book, too.

I want to make astronomy as accessible as possible to as many people as possible, she explains. Star gazing is easy, she says. All you need is your eyes.

Thachers book aims to make astronomy super accessible. Written for children in fourth through ninth gradesbut accessible to younger and older readers, toothe book has six chapters, and each chapter is about a different type of object: the Moon, the Sun, planets, stars, constellations..

The book also offers information on how to observe special celestial eventscomets, eclipses and meteor showers.

In addition to laying out when and what to look for, Sky Gazing also offers information about how to see thingswhich really isnt hard. Astronomy is easy; you dont even need a telescope, Thacher explains. All you have to do is go outside and look up. And youll see astronomy all around you.

Astronomy is easy to fall in love with, Thacher explains, because its a science of extremes. We deal with things that are really big, she laughs, and really old. Really far. There are billions of stars in the galaxy, billions of galaxies in the universe.Astronomy is really big and excitingthats why kids get interested in it.

And astronomy is a gateway science, Thacher adds: Once someone becomes interested in the stars, they become interested in the sciences that make up astronomyphysics, chemistry, math and more.

Really, all that has to happen, Thacher says, is that kids learn about astronomy, and theyll look up at the sky more often. And then they discover that they love the stars, and they love science!

The world needs more scientists, she adds. So looking up at the stars is a really good thing.

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Exploring the Wonders of the Night Sky - Smith College Grcourt Gate

Suddenly, Venus was one of the most enticing targets in the search for life beyond Earth, and in those first moments, other scientists in the field were unusually excited about the research and its implications.

But in the months since the big announcement, the enthusiasm has dissipated. Other scientists have raised doubts about the research. The original team has revised its findings. The science community is dividedenough that one rebuttal paper had the authors invite the researchers who originally identified the phosphine to consider retracting their study altogether. In scientific literature, that counts as quite a salty attack, enough to make other researchers wince. (The researchers later removed that wording and apologized.)

Read: Why Venus is the best planet

The controversial part of this discovery was supposed to be the suggestion that life could exist in Venuss clouds. Aliens, though, are not the subject of the current debate. Scientists are sparring over something more basic: the detection of the gas itself.

Is there phosphine in Venuss atmosphere, or isnt there? To a nonscientific observer, the question might seem straightforward enough. Why would determining this simple fact be complicated?

The shortest answer is that astronomy is hard. The work requires scientists to draw big conclusions about faraway places based on tiny signals imprinted on the light that reaches Earth. Telescope observations dont produce handy readouts that say Yes phosphine or No phosphine. The scientists behind the discovery had to apply mathematical equations to extract those little signals from noisy data and then try to interpret them based on their current knowledge of another planet, which itself isnt very robust. The momentous detection showed up in a simple plot of squiggly linesor it didnt, depending on whom you ask. Astronomy is full of disagreements like this one, but these squiggles provide the basis for nearly everything we know about the planets, stars, and galaxies beyond our own.

Venus was the first planet human beings ever explored with spacecraft. Starting in the 1960s, a series of Soviet missions revealed a furnace of a world, with a thick, cloudy atmosphere that keeps the surface so hot that lead would melt on it like ice on Earth. In the same era, astronomers Carl Sagan and Harold Morowitz suggested that, although Venusian ground was inhospitable to life, its atmosphere might not be. Perhaps the inhabitants of an early Venus, once as habitable and balmy as Earth, had escaped into the skies when the planet became unbearably sweltering.

Decades later, Jane Greaves, an astronomer at Cardiff University, directed a telescope at our next-door neighbor. Greaves had come across research that suggested astronomers looking for extraterrestrial life should consider checking for phosphine on exoplanets, since any alien astronomers looking back at us could likely spot signs of the same gas on Earth. She decided to test the idea on Venus. I wasnt really expecting that wed detect anything, Greaves told me in September.

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Astronomers Are Now Obsessed With a Particular Gas on Venus - The Atlantic

GN-z11, a young but moderately massive galaxy located in the constellation of Ursa Major, is estimated to date from when the Universe was only 420 million years old, or 3% of its current age.

This image shows GN-z11, a luminous star-forming galaxy at z=10.957. Image credit: NASA / ESA / P. Oesch, Yale University / G. Brammer, STScI / P. van Dokkum, Yale University / G. Illingworth, University of California, Santa Cruz.

From previous studies, GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light years, said co-lead author Dr. Nobunari Kashikawa, an astronomer in the Department of Astronomy at the University of Tokyo and the Optical and Infrared Astronomy Division at the National Astronomical Observatory of Japan.

But measuring and verifying such a distance is not an easy task.

In their new study, Dr. Kashikawa and colleagues aimed to measure the redshift of GN-z11.

Certain chemical signatures, called emission lines, imprint distinct patterns in the light from distant objects, they explained.

By measuring how stretched these telltale signatures are, we can deduce how far the light must have traveled, thus giving away the distance from the target galaxy.

We looked at ultraviolet light specifically, as that is the area of the electromagnetic spectrum we expected to find the redshifted chemical signatures, Dr. Kashikawa added.

The NASA/ESA Hubble Space Telescope detected the signature multiple times in the spectrum of GN-z11.

However, even Hubble cannot resolve ultraviolet emission lines to the degree we needed.

Using near-infrared spectroscopic observations from the MOSFIRE spectrograph on the Keck I telescope at the W.M. Keck Observatory in Hawaii, the researchers found the redshift of GN-z11 to be z=10.957.

MOSFIRE captured the emission lines from GN-z11 in detail, which allowed us to make a much better estimation on its distance than was possible from previous data, they said.

The results were published in the journal Nature Astronomy.

_____

L. Jiang et al. Evidence for GN-z11 as a luminous galaxy at redshift 10.957. Nat Astron, published online December 14, 2020; doi: 10.1038/s41550-020-01275-y

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GN-z11 Confirmed as Farthest Galaxy Ever Observed | Astronomy - Sci-News.com

(Upper) The arrow points to the most distant galaxy in the universe. (Lower) Carbon emission lines observed in infrared. When it left the galaxy, the signal was ultraviolet light in the region of 0.2 micrometers, but it was redshifted and stretched to over 10 times that to about 2.28 micrometers. Credit: Kashikawa et al.

A team of astronomers used the Keck I telescope to measure the distance to an ancient galaxy. They deduced the target galaxy GN-z11 is not only the oldest galaxy but also the most distant. Its so distant it defines the very boundary of the observable universe itself. The team hopes this study can shed light on a period of cosmological history when the universe was only a few hundred million years old.

Weve all asked ourselves the big questions at times: How big is the universe? or How and when did galaxies form? Astronomers take these questions very seriously, and use fantastic tools that push the boundaries of technology to try and answer them. Professor Nobunari Kashikawa from the Department of Astronomy at the University of Tokyo is driven by his curiosity about galaxies. In particular, he sought the most distant one we can observe in order to find out how and when it came to be.

From previous studies, the galaxy GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light years, or 134 nonillion kilometers (thats 134 followed by 30 zeros), said Kashikawa. But measuring and verifying such a distance is not an easy task.

Kashikawa and his team measured whats known as the redshift of GN-z11; this refers to the way light stretches out, becomes redder, the farther it travels. Certain chemical signatures, called emission lines, imprint distinct patterns in the light from distant objects. By measuring how stretched these telltale signatures are, astronomers can deduce how far the light must have traveled, thus giving away the distance from the target galaxy.

We looked at ultraviolet light specifically, as that is the area of the electromagnetic spectrum we expected to find the redshifted chemical signatures, said Kashikawa. The Hubble Space Telescope detected the signature multiple times in the spectrum of GN-z11. However, even the Hubble cannot resolve ultraviolet emission lines to the degree we needed. So we turned to a more up-to-date ground-based spectrograph, an instrument to measure emission lines, called MOSFIRE, which is mounted to the Keck I telescope in Hawaii.

The MOSFIRE captured the emission lines from GN-z11 in detail, which allowed the team to make a much better estimation on its distance than was possible from previous data. When working with distances at these scales, it is not sensible to use our familiar units of kilometers or even multiples of them; instead, astronomers use a value known as the redshift number denoted by z. Kashikawa and his team improved the accuracy of the galaxys z value by a factor of 100. If subsequent observations can confirm this, then the astronomers can confidently say GN-z11 is the farthest galaxy ever detected in the universe.

Reference: Evidence for GN-z11 as a luminous galaxy at redshift 10.957 by Linhua Jiang, Nobunari Kashikawa, Shu Wang, Gregory Walth, Luis C. Ho, Zheng Cai, Eiichi Egami, Xiaohui Fan, Kei Ito, Yongming Liang, Daniel Schaerer and Daniel P. Stark, 14 December 2020, Nature Astronomy.DOI: 10.1038/s41550-020-01275-y

Funding: National Science Foundation of China (11721303, 11890693, 11991052), the National Key R&D Program of China (2016YFA0400702, 2016YFA0400703) and the Chinese Academy of Sciences (CAS) through a China-Chile Joint Research Fund (1503) administered by the CAS South America Center for Astronomy, JSPS grant(15H03645).

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Astronomers Locate the Oldest and Most Distant Galaxy in the Universe Defines the Very Boundary of the Observable Universe - SciTechDaily

With the current health crisis hitting most aspects of people's lives, many have turned to new hobbies that suit social distancing and staying at home.

Stargazing and amateur astronomy are two activities to benefit from people's enforced isolation, with lockdowns across the globe leading to an increase in people observing the night skies and a rise in sales of astronomical instruments.

But despite the attraction of these activities, some people have found the use of traditional telescopes hard work, especially those who are new to amateur astronomy. It's a problem that a young French company is trying to tackle.

SEE: Guide to Becoming a Digital Transformation Champion (TechRepublic Premium)

Vaonis, a Montpellier-based startupfounded in 2016 and specializing in the production of astronomical instruments, recently launched its newest device, Vespera. It's a cross between a smart telescope and a camera and is expected to cost about $1,500.

In October, the company launched a 30-day pre-order campaign and managed to attract $2.5m in worldwide billing, making Vespera the most-funded project in the category of space exploration and the most-funded tech or hardware project in France.

Vespera's app lets an astronomer control the telescope from their smartphone to select and home in on the celestial object they want to observe. The telescope will then point at the object and track it.

Vaonis says apart from the device's automatic pointing and tracking system, it also employs intelligent and powerful image processing with autofocus. Vespera calibrates itself using its owner's phone GPS and the company's star-recognition technology.

During the quarantine, the French company saw the number of orders, uses, and shared photos created using its devices more than double. Aiming to shake up the field, Vaonis has also teamed up with former NASA astronauts Scott Kelly and Terry Virts, utilizing their experience and expertise.

According to Virts, smart telescopes like Vespera, are there to bring astronomy closer to almost everybody.

"I've owned multiple telescopes over my life, including reflectors and refractors. I've always enjoyed them, and the thrill of seeing objects in the night sky" Virts tells ZDNet.

"But frankly it is too much work to drag a typical six-inch or eight-inch or even 12-inch telescope outside at night, align it, and attach astrophotography devices. Most telescopes are never used."

Now, by having this technology at hand, observers can spot deep sky objects in just minutes, Virts explains.

"It makes it possible to see amazing deep-sky objects that are thousands or sometimes millions of light years away. Observations like that are simply not possible with conventional telescopes without a significant amount of expertise, time, and heavy and expensive equipment."

It took Vaonis nine months to complete the project, which is the company's second product. The technology behind the device combines optics, electronics and high-precision mechanics.

For the new product, the company was able to exploit much of the work that had gone into its first project, an observation device called Stellina.

"A lot of the work required to get Stellina out the door wasn't feature specific, but involved things like camera integration, mobile app communication and deployment, firmware management, user interface design, bug tracking," the company said.

"Having that foundation means we can spend more time optimizing performance and testing features."

Now, it reckons its products can also lead to a new generation of astronomical technology for observing deep space.

"It can inspire a whole new generation of instruments to observe the universe. It's not only to observe it's to capture, share, and learn, all in one product." Cyril Dupuy, founder and CEO of Vaonis, tells ZDNet.

"Regarding the rest of the industry, it's too early to say but it will certainly encourage other companies to create products with a better user experience than the traditional telescope."

SEE: Digital transformation: The new rules for getting projects done

In addition to being the smallest smart telescope in the world, the device is also the only instrument to offer sky observers a shared and interactive experience around the stars, while respecting the precautions of use imposed by COVID-19, thanks to the way it allows remote observation on screen, the company adds.

According to James Sweitzer, a Kickstarter supporter of the project, the use of such devices will help more people understand the fascination of deep space.

"As a lifelong astronomer and planetarium developer, I'm interested in their use for education," he says.

"But I firmly believe their most important impact will be to lift the veil on the deep universe and bring joy and wonder to many people. They are like admission to the infinite planetarium."

Using the app, you can select the object you want to observe, and Vespera will point and track it.

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These new smart telescopes aim to open up stargazing and astronomy to all - ZDNet

Since time immemorial, humans have been fascinated by the night sky.

Our relationship with it was forever changed in the early 1600s, when Galileo Galilei raised a small hand-held telescope to the sky and became the first person to see Jupiters moons and Saturns rings.

Optical telescopes today range from pocket telescopes just a few inches long, to the colossal Thirty Meter Telescope being built in Hawaii (which will weigh more than 1,400 tonnes).

There are even bigger arrays of telescopes that observe in radio wavelengths, such as the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope.

Read more: We've mapped a million previously undiscovered galaxies beyond the Milky Way. Take the virtual tour here.

These large telescopes used for research dont have a typical eyepiece. Rather, they use highly specialised computer-connected sensors that record signals from the sky.

The good news, however, is there are plenty of telescopes in more manageable sizes which you can use at home to observe moons, gas giant rings and maybe even deep sky objects such as nebulae or the Andromeda galaxy.

But before buying a home telescope, there are some points to consider. Who will be using it (other than you)? What do you want to observe? And just as important, how much are you willing to spend?

Optical telescopes are designed to capture light emitted by stars and reflected by planets and moons. You can think of them as light-collecting buckets. The bigger they are, the more light theyll catch.

This light then has to be focused to form an image. There are two types of optical telescopes available on the market today: reflectors and refractors. Reflectors use mirrors to bend incoming light; refractors use lenses.

Of the two options, reflectors are relatively cheaper. A few hundred dollars will buy you an instrument much larger than the refractor Galileo used. But bigger also means heavier and harder to transport.

Refractors are smaller, easier to transport and produce sharp images but theyre more expensive, with a 100mm diameter telescope costing about A$500.

The larger the primary glass lens (where the light enters) of a refractor, the longer the whole telescope must be to focus the light rays. At the same time, the larger a lens, the harder it is to make. So theres a limit to how big refractors can be.

Although refractors and reflectors are the two classic telescope designs, today there are many types of hybrid telescopes that combine elements of both.

Dobsonian reflector telescopes are often recommended as a great first telescope for budding astronomers. They can be set up in as little as 20 minutes.

Dobsonians have very simple mounts called Altitude-Azimuthal mounts, which are moved by hand to a target of choice. They move in the up-and-down (altitude) and left-to-right (azimuthal) directions.

To get the most from your telescope, youll need accessories. Youd probably want some different-sized eyepieces to change the telescopes magnification. Also, anti-glare and anti-light pollution filters are highly recommended if you live in a residential area.

The simplicity of Dobsonians makes them great for observing our Moon and other planets in the Solar system. A good size to start with is a 6" (150mm) Dobsonian. On average, this will set you back about A$500.

At-home astrophotography can be done with either type of optical telescope but requires more specialised equipment. For deep-sky photos, the more you spend, the better your results will be.

Youll need a telescope with very good optics and a computerised GoTo equatorial mount.

These motor-powered mounts take into account Earths rotation and can automatically point you to a selected object. This feature is very popular, so most major brands sell telescopes with it built in.

Youll also need an external power source and accessories including a DSLR camera, camera adaptor, timer shutters and filters (depending on the type of astrophotography you want to do). Once youre set up, your camera can capture the night sky.

There are many processing techniques you can use after to help you get incredible compositions, as well as dedicated online forums for advice.

Amateur astronomers do much more than just take beautiful photos. They also help professionals. Over the decades, citizen scientists have discovered a plethora of comets and asteroids.

Now theyre helping with larger projects, too. One example is Galaxy Zoo, a crowdsourced project that asks volunteers to sort thousands of galaxies into different groups based on appearance.

There have been more than 60 scientific papers published as a result of these volunteering efforts. In 2017, some viewers of the ABCs Stargazing Live program discovered a five-planet system orbiting a star. It became the subject of a paper on which they were credited as authors.

For anyone considering astronomy as a hobby, a good start would be to visit your local astronomical society. There are now more than 30 across Australia.

Society members are passionate about astronomy, often own a wide range of equipment and hold regular meetings for people with all levels of experience.

Read more: SpaceX's Starlink satellites are about to ruin stargazing for everyone

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The best gift in the galaxy: an astronomers guide to buying a home telescope - The Conversation AU

After 20 years and four previous phases, the Sloan Digital Sky SurveysPhase V(SDSS V) is ready to give Yale astronomers a new look at the wonders of the cosmos.

The surveys mission is ambitious: It aims to create a detailed, three-dimensional map of the universe, using a 2.5-meter, wide-angle optical telescope located at the Apache Point Observatory in New Mexico.

Previous SDSS surveys have mapped one-third of the sky.SDSS datahave been used in more than 7,700 peer-reviewed, scientific papers, offering insights into the chemical makeup of the Milky Way and the structure of distant galaxies. It has also helped produce multi-color imaging for hundreds of millions of stars, and gleaned information about 100,000 asteroids and other objects within Earths solar system. The fifth iteration of the survey will add more information about each object observed.

Yale is a full participating member of the SDSS collaboration, which includes dozens of research institutions around the world. Yale astrophysicists have used SDSS data to contribute groundbreaking research on black holes, quasars, galaxy formation, and other cosmological phenomena. For example, Yale researchers identified the first changing-look quasar, discovered dwarf galaxies that contain massive black holes, and helped find a rare group of galaxies called the Green Peas.

Meg Urry, Yales Israel Munson Professor of Physics and Astronomy, who served on the advisory committee for both SDSS-III and SDSS-IV, spoke to YaleNews about SDSSs latest phase and its potential use by Yale researchers.

How long has Yale been involved in SDSS?

Yale was a partner in SDSS-III, which ran from 2008 to 2014, and SDSS-IV, which ran from 2014 to 2020. These are large efforts to take enormous amounts of data covering a large fraction of the sky, with increasingly sophisticated instrumentation. Each survey consists of a few sub-projects, each with its own instruments, and a dedicated telescope in New Mexico. Starting with SDSS-IV, we also have a telescope in the southern hemisphere, at Las Campanas Observatory in Chile.

Yale is a full institutional partner in SDSS. What does that entail?

It means that any student, postdoc, or faculty member has open access to all the data. All data become public eventually but institutional partners like Yale have an inside track to the early science, by virtue of having contributed to the cost of the survey.

What are some of the new experiments that Yale researchers plan to use?

Some of us includingPriyamvada Natarajan,Paolo Coppi, and myself are interested in the Black Hole Mapper experiment, which will obtain spectra of all the X-ray sources from the eROSITA satellite, which was launched just over a year ago. This will greatly increase our understanding of the growth of the most massive, most distant black holes. In particular, Priya Natarajan plans to address the critical question of the origin of the first black holes, and I personally am excited about finalizing our census of black hole growth across the past approximately 12 billion years.

Other faculty, includingMarla Geha,Bob Zinn, andJeff Kenney, and their research groups will be involved in the Local Volume Mapper, which will explore the local group of galaxies.Sarbani Basu,Hector Arce, andCharles Bailynare among the faculty interested in the Milky Way Mapper, which, as its name suggests, is an exploration of more than 4 million stars through the Milky Way and local group.

Are students also able to use SDSS data?

These massive data sets are suitable for big science such as my groups work on modeling the growth of black holes over the past 12 billion years as well as more focused student projects. Any undergraduate can download some data and learn something new, something that has never been studied before. It is a very powerful laboratory for astrophysics.

Has the COVID-19 pandemic had an effect on how SDSS-V is taking shape?

The COVID pandemic has indeed affected SDSS. It has affected every facet of the operations by restricting travel to the sites for installing new instruments and limiting working conditions at the two observatories. The health of people working at the telescopes is paramount. It is hoped that we can still get the full survey, but each night the observatories are closed is a night we are not taking data.

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Sloan survey gives Yale astronomers an eye in the sky - Yale News

Back in March of 2016, NASA/ESA'sHubble Space Telescopespotted the most distant heavenly object ever seen in the great universalvoid:an extremely remote galaxy silently spinning beyond the constellation Ursa Major, some 13.4 billion light-years away.

Officially catalogued asGN-z11, this ancient galactic raritywas captured in the same form as when itexisted nearly420 million years followingthe Big Bang, making it one of the first galaxies formed afterthat cataclysmic event.

Now a new study presentedby astronomers at the University of Tokyo and Peking University hasaccurately measured the redshift of GN-z11.In a new paper published in Nature Astronomy, researchersconfirmedthat this far-off galaxy is indeedthe furthestobservable object witnessedby mankind.

From previous studies,GN-z11seems to be the farthest detectable galaxy from us, at 13.4 billion light years, explainedco-lead authorDr. Nobunari Kashikawa,Department of Astronomy at the University of Tokyo. But measuring and verifying such a distance is not an easy task.

A key toolfor astrophysicists, redshift is a shift toward longer wavelengths inspectral lines emitted by distant galaxies and celestial objects. It'sthe result of the universe expanding,andsubsequently theobject moving away from the Earth.

According to the research paper, the team targeted chemical signatures known as emission lineswhich imprint uniquepatterns in the light streaming in from distant objectsfor their calculations.

By measuring how stretched these telltale signatures are, we can deduce how far the light must have traveled, thus giving away the distance from the target galaxy," Kashikawa added. We looked at ultraviolet light specifically, as that is the area of the electromagnetic spectrum we expected to find the redshifted chemical signatures."

While the originaldata collected by Hubblerecordedthe signature numeroustimes in the spectrum of GN-z11, scientists still required more precisedetails of these ultraviolet emission lines to lock in the record-breaking find.

By employingnear-infrared spectroscopic observations usingtheMOSFIRE spectrograph installed on theKeck I telescopeat the W.M. Keck Observatory in Hawaii, Kashikawa and his colleagues discovered that GN-z11's redshift was officially determined to bez=10.957.

MOSFIRE captured the emission lines from GN-z11 in detail, which allowed us to make a much better estimation on its distance than was possible from previous data, Kashikawa and his crew noted.

In addtional news generated from this remote galaxy, a team led byLinhua Jiang ofPeking University in Beijing, Chinawasrecently using the Keck Observatory in Hawaii to study GN-z11. Theyobserveda massive explosion emanating from the faint celestial location.The galaxy appearedhundredof times brighter for just under 3 minutes, and was likely caused by an intense gamma-ray burst when one of its stars exploded in a brilliant supernova.

If verified, this would go down asthe oldest gamma-ray burst ever spotted, something not normally observed in galaxies born in the fledgling universe.

"This is because gamma-ray bursts should be extremely rare," saidJiang.The probability to detect a gamma-ray burst [in a particular galaxy] is near to zero, he says. If you observed a galaxy for a million years, youd probably find [only] a few gamma-ray bursts. Thats why its so surprising.

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It's official! Astronomers confirm GN-z11 is the most distant galaxy ever seen - SYFY WIRE

I love a good coincidence, and this story has two. One is pedestrian, the other cosmic.

It starts with me pondering Gaia data. Gaia is a European Space Agency observatory that is revolutionizing astronomy. Its mission is to accurately map the positions, colors, distances, and motions of over a billion stars yes, a billion, about 1% of all the stars in our galaxy and create a massive database of the results, essentially a 3D map of the Milky Way galaxy.

Such surveys are incredibly useful. New objects can be found this way, like stellar streams. Sometimes hidden objects reveal themselves in the data. The shape of the galaxy can be found, as well as the distances to star clusters, the remains of cannibalized galaxies, and, importantly, the distances to some stars that are used to calibrate our distance scales to other galaxies, and from there the Universe.

And, sometimes, they can solve age-old mysteries. For example, the star Albireo is a close double star, but are the two stars physically related? Astronomers argued for a long time, but Gaia data easily showed that nope, they're not related, at two very different distances but just coincidentally aligned in the sky.

Which brings us to M73.

This is purportedly a small, loose cluster of stars in the constellation of Aquarius. The M in its name means it was catalogued by the famous French astronomer Charles Messier, who was a comet hunter in the late 18th and early 19th centuries. As he scanned the sky looking for these objects, he kept stumbling on fuzzy things that were easily mistaken for comets, and he got irritated enough by them that he listed them in his now-famous Messier Catalog, so that others might not be fooled.

Thing is, those are some of the brightest and best-known objects in the sky now. The Orion Nebula, the Andromeda galaxy, the Pleiades... all of these and 100 more sport M numbers.

And then there's M73. This is the object in question:

I know, right? Not much there. The cluster is composed of the four bright stars in the center, and the three slightly dimmer ones below. To Messier, in his small telescope, they looked a bit fuzzy so he listed them, claiming he saw nebulosity around them, what we now think of as clouds of gas and dust. Many clusters are still embedded in the material they were born from (see the aforementioned Pleiades), so fair enough.

Decades later, John Herschel was making his own, much larger catalog, called the General Catalogue of Nebulae and Clusters of Stars, and noted that M73 was listed by Messier. To him they just looked like stars (he notes it looks "very poor" and lists it as "Cl??" meaning "cluster??"). Years later, when John Lewis Emil Dreyer compiled the extensive (and still used) New General Catalog,he listed M73 in his catalog as NGC 6994, and while he copied Herschel's comments he took the question marks away, so it's listed as just "Cl, eP, vlC, no neb.": cluster, extremely poor, very little compressed, no nebulosity"*.

And that's the thing. Ever since then over a century ago! astronomers have argued over this collection of 7 stars. Is it a cluster or not?

It's a fair question. Clusters usually have dozens or hundreds of stars, but as they age stars get ejected, and at some point you're going to have just a few stars hanging out together. Is M73 one of those?

Two papers came out by professional astronomers at almost the same time tackling this issue. Although using different telescopes, they both looked at the colors of the stars if plotted a certain way, that can be used to determine if stars belong in a cluster or not. And guess what? Go ahead, guess!

Yup. In one paper a researcher concluded the stars were not in a cluster, and in the other, they concluded they were. Hurray.

So which is it?

About a year later, another team of astronomers took spectra of the stars, breaking their light up into individual colors, in order to look for a Doppler shift which determines if the stars are moving toward or away from us, and how rapidly. If the stars are physically in a cluster, they should all have roughly the same velocities.

And... they don't. One, for example, is moving toward us at 53 kilometers per second, while another is moving away at 35 km/sec. The others are scattered all over the place in between those two values.

It's pretty clear, then, they're not in a cluster together.

But, maaaaaybe they recently underwent some big scattering event, sending them every which way. That's hugely unlikely, but it would be nice to know for sure.

... and that brings us back to Gaia. It measures the distances to stars via parallax, and is very accurate for stars like this. The conclusion?

Nope. The stars are at all different distances, ranging from about 1,000 to 3,000 light years (although one has a distance of 45,000 light years, which is far enough that Gaia has a harder time measuring parallax, so the distance is a bit uncertain). A cluster of stars is usually just a few dozen light years across at most, so these stars are clearly physically unassociated with each other.

Their apparent closeness in the sky is therefore a coincidence, an illusion. It's like seeing a bug on your window apparently next to a distant mountain. The Universe is tricksy that way.

In other words: M73 is not a cluster. Never was, never will be.

So that's the cosmic coincidence. What's the pedestrian one?

As I said, I've written about Gaia data debunking some astronomical objects like Albireo. As an amateur astronomer of many decades, I've done my share of scratching my head over M73 (though honestly I've always leaned toward it being an outcome of chance). So I've had a note to write about this for a couple of years, but just never got around to it.

Then out of the blue I got an email from reader Dean Lewis. He asked me if I had seen the Deep Sky Videos series, created by professional astronomers, that goes over (nearly) every object in Messier's catalog.

I hadn't, as it turns out, despite it being done by people like Dr. Becky Smethurst, a noted and wonderful science communicator. And amazingly the second coincidence the video he watched that made him want to contact me was on M73!

Well! That pushed me to finally write up this little tale. And Dr. Smethurst had some info in her video I was unaware of, and used as reference material in the article you're reading now, matter of fact. She did a great job, so give it a watch:

Lovely. I like how she talks about confirmation bias, and even how astronomers can be fooled, even when looking at almost essentially the same data. One reason we have so many rules in science when publishing is to avoid bias in our interpretation of data. It doesn't always work, but in the end here we are. We now know M73 is not a cluster, and we've learned hopefully to be a little more careful.

Gaia has been an amazing tool for this. And it's nowhere near finished, either. A new data release is scheduled for December 2020, and will have 1.5 billion stars in it. What new treasures are buried in the observations?

And what treasures do we hold now that it will show to be fool's gold? With open eyes and open minds, I guess we'll find out.

* Correction: I originally made some errors in this part of the article, saying William Herschel made the NGC; I conflated a couple of things there. William was John's father, and while he and his wife Caroline made a catalog, the NGC came later. My thanks to Larry Faltz, editor of Sky WAAtch,for pointing this out to me!

Read more:

The star cluster that wasn't: How did M73 fool generations of astronomers? - SYFY WIRE