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Improving View...

Posted by Reginald L. Goodwin on April 23, 2020 at 5:00am

View of the Alpha Centauri system. The bright binary star Alpha Centauri AB lies at the upper left. The much fainter red dwarf star Proxima Centauri is barely discernible towards the lower right of the picture. Credit: Digitized Sky Survey 2; Acknowledgement: Davide De Martin and Mahdi Zamani

Topics: Astronomy, Astrophysics, Exoplanets, Space Exploration

Little is more enticing than the prospect of seeing alien worlds around other stars—and perhaps one day even closely studying their atmosphere and mapping their surface. Such observations are exceedingly difficult, of course. Although more than 4,000 exoplanets are now known, the vast majority of them are too distant and dim for our best telescopes to discern against the glare of their host star. Exoplanets near our solar system provide easier imaging opportunities, however. And no worlds are nearer to us than those thought to orbit the cool, faint red dwarf Proxima Centauri—the closest star to our sun at 4.2 light-years away.

In 2016 astronomers discovered the first known planet in this system: the roughly Earth-sized Proxima b. But because of its star-hugging 11-day orbit around Proxima Centauri, Proxima b is a poor candidate for imaging. Proxima c, by contrast, offers much better chances. Announced in 2019, based on somewhat circumstantial evidence, the planet remains unconfirmed. If real, it is estimated to be several times more massive than Earth—a so-called super Earth or mini Neptune—and to orbit Proxima Centauri at about 1.5 times the span between Earth and the sun. Its size and distance from its star make the world a tempting target for current and near-future exoplanet-imaging projects. Now, in a new preprint paper accepted for publication in the journal Astronomy & Astrophysics, some astronomers say they might—just might— have managed to see Proxima c for the first time.

“This planet is extremely interesting because Proxima is a star very close to the sun,” says Raffaele Gratton of the Astronomical Observatory of Padova in Italy, who is the study’s lead author. “The idea was that since this planet is [far] from the star, it is possible that it can be observed in direct imaging. We found a reasonable candidate that looks like we have really detected the planet.”

Astronomers May Have Captured the First Ever Image of Nearby Exoplanet Proxima C
Jonathan O'Callaghan, Scientific American

Pioneer...

Posted by Reginald L. Goodwin on April 20, 2020 at 5:00am

Burbidge, pictured with her husband and research partner, Geoffrey, was appointed to numerous leadership positions previously held only by men. | W.W. Girdner/Caltech Archives

Topics: Astronomy, Astrophysics, Diversity, Diversity in Science, Women in Science

Margaret Burbidge, a past president of the American Association for the Advancement of Science who overcame gender discrimination on the way to becoming one of the most influential astrophysicists of her time, died on April 5 at her home in San Francisco. She was 100.

In 1957, Burbidge was the lead author of a study detailing the chemical processes by which elements heavier than lithium, including the carbon and oxygen that drive life on Earth, are created inside stars. The origins of such elements were previously unknown, and the research paper is the foundation of current understanding of what astronomers now call stellar nucleosynthesis.

Later in her career, Burbidge was appointed to numerous leadership positions previously held only by men and helped develop the Faint Object Spectrograph, one of the original scientific instruments aboard NASA’s Hubble Space Telescope. The FOS team provided the first strong, observational evidence for the existence of a supermassive black hole in the core of another galaxy.

Eleanor Margaret Peachey was born in Davenport, England, on August 12, 1919. Her father was a chemistry lecturer in nearby Manchester, and her mother had been one of his students.

When Peachey was two, the family moved to London, where cloudy skies often prevented starlight from reaching the city.

“The first time I consciously remember really noticing the stars was the summer that I was four, and we were going on a night crossing to France for summer vacation,” Burbidge said in a 1978 interview with the American Institute of Physics. “These twinkling lights became another fascination to me.”

Aware of her interest in the stars, Peachey’s grandfather gave her books by English astronomer James Jeans for her 12th and 13th birthdays. By the age of 19, she had graduated with honors from University College London, where she studied astronomy, physics and mathematics. In 1943, she earned her Ph.D. from UCL.

After receiving her doctorate in the midst of World War II, Peachey continued to use the telescope at the UCL Observatory, sometimes with bombs exploding in the city around her. Hoping to work with better equipment and clearer skies, she applied for a fellowship that would have placed her at the Mount Wilson Observatory outside of Los Angeles.

“The turn-down letter simply pointed out that Carnegie Fellowships were available only for men,” Burbidge wrote in a 1994 memoir. “A guiding operational principle in my life was activated: If frustrated in one’s endeavor by a stone wall or any kind of blockage, one must find a way around — another route towards one’s goal. This is advice I have given to many women facing similar situations.”

In 1948, Peachey married Geoffrey Burbidge, a UCL graduate student in physics who soon switched fields to collaborate with his wife on her astronomy research. When Geoff applied for the same Carnegie Fellowship, he was accepted, and Margaret took a position at the California Institute of Technology in Pasadena. When they needed to use the Mount Wilson telescope, the couple would arrive with Margaret posing as her husband’s assistant.

In Memoriam:
Margaret Burbidge, Pioneering Astronomer and Advocate for Women in Science
Adam D. Cohen, American Association for the Advancement of Science

Missing Link...

Posted by Reginald L. Goodwin on April 6, 2020 at 12:00pm

A cosmic homicide in action, with a wayward star being shredded by the intense gravitational pull of a black hole that contains tens of thousands of solar masses in an artist's impression obtained by Reuters April 2, 2020. NASA-ESA/D. Player/Handout via REUTERS.

Topics: Astrophysics, Black Holes, Cosmology, General Relativity, Hubble

Using data from the Hubble Space Telescope and two X-ray observatories, the researchers determined that this black hole is more than 50,000 times the mass of our sun and located 740 million light years from Earth in a dwarf galaxy, one containing far fewer stars than our Milky Way.

Black holes are extraordinarily dense objects possessing gravitational pulls so powerful that not even light can escape.

This is one of the few “intermediate-mass” black holes ever identified, being far smaller than the supermassive black holes that reside at the center of large galaxies but far larger than so-called stellar-mass black holes formed by the collapse of massive individual stars.

“We confirmed that an object that we discovered originally back in 2010 is indeed an intermediate-mass black hole that ripped apart and swallowed a passing star,” said University of Toulouse astrophysicist Natalie Webb, a co-author of the study published this week in Astrophysical Journal Letters.

Astronomers spot 'missing link' black hole - not too big and not too small
Will Dunham, Reuters Science

TNOs and Planet Nine...

Posted by Reginald L. Goodwin on April 1, 2020 at 5:00am

Over the past decade or so, astronomers have discovered a number of far-flung objects that all have very similar perihelia, meaning they make their closest approaches to the Sun at about the same location in space. One leading theory that attempts to explain the clustering is that a massive and unseen world known as Planet Nine hiding in the outer solar system.

Fauxtoez/WikiMedia Commons

Topics: Astronomy, Astrophysics, Exoplanets, Space Exploration

Note: Not an April 1st joke. With the COVID-19 crisis, I literally had to peruse some sites that DIDN'T talk about what we're all living through. It's been rough, thinking about how and when this all ends. I'll try to get my sea legs back to blogging about science. Bear with me. I'm human.

Astronomers have discovered 139 new minor planets orbiting the Sun beyond Neptune by searching through data from the Dark Energy Survey. The new method for spotting small worlds is expected to reveal many thousands of distant objects in coming years — meaning these first hundred or so are likely just the tip of the iceberg.

Taken together, the newfound distant objects, as well as those to come, could resolve one of the most fascinating questions of modern astronomy: Is there a massive and mysterious world called Planet Nine lurking in the outskirts of our solar system?

Neptune orbits the Sun at a distance of about 30 astronomical units (AU; where 1 AU is the Earth-Sun distance). Beyond Neptune lies the Kuiper Belt — a comet-rich band of frozen, rocky objects (including Pluto) that holds dozens to hundreds of times more mass than the asteroid belt. Both within the Kuiper Belt and past its outer edge at 50 AU orbit distant bodies called trans-Neptunian objects (TNOs). Currently, we know of nearly 3,000 TNOs in the solar system, but estimates put the total number closer to 100,000.

As more and more TNOs have been discovered over the years, some astronomers — including Konstantin Batygin and Mike Brown of Caltech — have noticed a small subset of these objects have peculiar orbits. They seem to bunch up in unexpected ways, as if an unseen object is herding these so-called extreme TNOs (eTNOs) into specific orbits. Batygin and Brown — in addition to other groups, like that led by Scott Sheppard of the Carnegie Institution for Science — think these bizarrely orbiting eTNOs point to the existence of a massive, distant world called Planet Nine.

Hypothesized to be five to 15 times the mass of Earth and to orbit some 400 AU (or farther) from the Sun, the proposed Planet Nine would have enough of a gravitational pull that it could orchestrate the orbits of the eTNOs, causing them to cluster together as they make their closest approaches to the Sun.

The problem is that the evidence for Planet Nine is so far indirect and sparse. There could be something else that explains the clumped orbits, or perhaps researchers stumbled on a few objects that just happen to have similar orbits. Discovering more TNOs, particularly beyond the Kuiper Belt, will allow astronomers to find more clues that could point to the location of the proposed Planet Nine — or deny its existence altogether. Of the 139 newly discovered minor planets found in this study, seven are eTNOs, which is a significant addition to a list that numbered around a dozen just a few months ago.

Astronomers find 139 new minor planets in the outer solar system
Erica Naone, Astronomy

Primordial Black Holes...

Posted by Reginald L. Goodwin on January 15, 2020 at 5:00am

Snapshot from the central region of a numerical simulation of two merging neutron stars. It shows the stars stretched out by tidal forces just before their collision. Credit: CoRe/Jena FSU

Topics: Astronomy, Astrophysics, Black Holes, Einstein, General Relativity

In the nearly five years since their first direct detection, gravitational waves have become one of the hottest topics in astronomy. With facilities such as the Laser Interferometer Gravitational-Wave Observatory (LIGO), researchers have mostly used these ripples in spacetime to study the inner workings of merging black holes, but LIGO has also detected gravitational waves from other sorts of celestial crashes, such as the collisions of ultradense stellar remnants called neutron stars. Sometimes, however, LIGO serves up gravitational waves that leave astronomers scratching their heads—as was the case for GW190425, an event detected last April that was recently attributed to a neutron star merger.

The trouble is that LIGO’s data suggest this neutron star pair was substantially overweight—collectively, some 3.4 times the mass of the sun, which is half a solar mass heavier than the most massive neutron star binaries ever seen. “It is the heaviest known by a pretty wide margin,” says Chad Hanna, an astrophysicist at Pennsylvania State University who hunts gravitational waves.

Did Astronomers Just Discover Black Holes from the Big Bang? Nola Taylor Redd, Scientific American

Through the Looking-Glass...

Posted by Reginald L. Goodwin on January 9, 2020 at 5:00am

An animation shows the random appearance of fast radio bursts (FRBs) across the sky.
(Image: © NRAO Outreach/T. Jarrett (IPAC/Caltech); B. Saxton, NRAO/AUI/NSF)

Topics: Astronomy, Astrophysics, Radio Astronomy, Research, Space Exploration

“Curiouser and curiouser!” Cried Alice (she was so much surprised, that for the moment she quite forgot how to speak good English).”

― Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass

HONOLULU — Mysterious ultra-fast pinpricks of radio energy keep lighting up the night sky and nobody knows why. A newly discovered example of this transient phenomenon has been traced to its place of origin — a nearby spiral galaxy — but it's only made things murkier for astronomers.

The problem concerns a class of blink-and-you'll-miss-them heavenly events known as fast radio bursts (FRBs). In a few thousandths of a second, these explosions produce as much energy as the sun does in nearly a century. Researchers have only known about FRBs since 2007, and they still don't have a compelling explanation regarding their sources.

"The big question is what can produce an FRB," Kenzie Nimmo, a doctoral student at the University of Amsterdam in the Netherlands, said during a news briefing on Monday (Jan. 6) here at the 235th meeting of the American Astronomical Society in Honolulu, Hawaii.

FRB 180916.J0158+65, as the object is known, is a repeating FRB discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) observatory, a radio telescope near Okanagan Falls in British Columbia that Nimmo called "the world's best FRB-finding machine."

Follow-up observations by a network of telescopes in Europe allowed the research team to produce a high-resolution image of the FRB's location. This location turned out to be a medium-sized spiral galaxy like our Milky Way that is surprisingly nearby, only 500 million light-years away, making it the closest-known FRB to date. The results were published yesterday (Jan. 6) in the journal Nature.

Origin of Deep-Space Radio Flash Discovered, and It's Unlike Anything Astronomers Have Ever Seen
Adam Mann, Live Science

#P4TC links:

FRBs...December 7, 2015
Fast Radio Bursts and Missing Matter...February 25, 2016
ET, FRBs and Light Sails...March 13, 2017

Astronomy's Top Ten 2019...

Posted by Reginald L. Goodwin on January 2, 2020 at 5:00am

Exoplanet K2-18 b orbits a red dwarf star and has an extended atmosphere containing at least some water vapor, as seen in this artist's concept. The system also contains another exoplanet sitting closer to the star, but it lies inside of the star's habitable zone

Topics: Astronomy, Astrophysics, Black Holes, Exoplanets, Hubble

Astronomers have finally uncovered water vapor in the atmosphere of a super-Earth exoplanet orbiting within the habitable zone of its star. The find means that liquid water could also exist on the rocky world's surface, potentially even forming a global ocean.

The discovery, made with NASA's Hubble Space Telescope, serves as the first detection of water vapor in the atmosphere of such a planet. And because the planet, dubbed K2-18 b, likely sports a temperature similar to Earth, the newfound water vapor makes the world one of the most promising candidates for follow-up studies with next-generation space telescopes.

"This is the only planet right now that we know outside the solar system that has the correct temperature to support water, it has an atmosphere, and it has water in it, making this planet the best candidate for habitability that we know right now," lead author Angelos Tsiaras, an astronomer at University College London, said in a press conference.

Researchers created this enhanced view of Enceladus’ south polar region by combining Cassini images taken through infrared, green, and ultraviolet filters. The tiger stripe fractures, the source of the plumes venting gas and dust into space, are prominently visible at center.
NASA/JPL-Caltech/SSI/Lunar and Planetary Institute/Paul Schenk (LPI, Houston)

“In the old time Pallas [Athena] heaved on high Sicily, and on huge Enceladus dashed down the isle, which burns with the burning yet of that immortal giant, as he breathes fire underground.”

— Quintus Smyrnaeus, The Fall of Troy

Saturn’s sixth-largest moon, Enceladus has a diameter of only 310 miles (500 kilometers), and a mass less than 1/50,000 that of Earth. When it comes to places to look for life, however, Enceladus is at the top of the list, and it’s right in our cosmic backyard.

A bit ignored at first

English astronomer William Herschel discovered Enceladus in 1789, but it remained an enigma until the Cassini mission began orbiting Saturn in 2004. Prior to Cassini, Enceladus was a bit ignored. We didn’t know liquid water could exist that far out in the solar system, so why would anyone be that interested in another boring, dead ball of ice?

That all changed one year later, when Cassini’s magnetometer (think: fancy compass) detected something strange in Saturn’s magnetic field near Enceladus. This suggested the moon was active. Subsequent passes by Enceladus revealed four massive fissures — dubbed “tiger stripes” — in a hot spot centered on the south pole. And emanating from those cracks was a massive plume of water vapor and ice grains. Enceladus lost its label of being a dead relic of a bygone era and leaped to center stage as a dynamic world with a subsurface ocean.

Astronomy's 10 most popular space stories of 2019, Staff

Mapping Titan...

Posted by Reginald L. Goodwin on November 19, 2019 at 5:00am

These infrared views of Titan peer through the gloom
NASA/JPL-Caltech/Stéphane Le Mouélic, University of Nantes, Virginia Pasek, University of Arizona

Topics: Astrophysics, Cassini, Exoplanets, Moon, Space Exploration

Slowly but surely, the surface of Saturn’s strange moon Titan is being revealed. Researchers have made the first map of the geology of Titan’s entire surface, and it will eventually help us figure out what the climate is like there.

Titan’s atmosphere is full of a thick, orange haze that blocks visible light from reaching the surface, making it difficult for spacecraft to take pictures. NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017, took radar and infrared data of Titan’s surface, giving researchers a hint of the terrain below.

Rosaly Lopes at NASA’s Jet Propulsion Laboratory in California and her colleagues assembled those observations and placed each area, or unit, into one of six categories: lakes, craters, dunes, plains, hummocky terrain – meaning hills and mountains – and labyrinth, which looks like heavily eroded plateaus. They then made a map of where each of those terrains exists on Titan’s surface.

We have the first full map of the weird surface features of Titan
Leah Crane, New Scientist

The Slingshot Effect...

Posted by Reginald L. Goodwin on November 14, 2019 at 5:00am

An artist’s illustration of a spacecraft’s escape trajectory (bright white line) from our solar system into interstellar space. Credit: Mike Yukovlev Johns Hopkins Applied Physics Laboratory - Link 2 below

Topics: Astrophysics, Interstellar Travel, NASA, Spaceflight, Star Trek

Yes, an actual slingshot effect does exist.

As much a fan as I am of the Trek, this isn't it.

When a spacecraft in orbit about a primary body comes close to a moon that is orbiting the same primary body, there is an exchange of orbital energy and angular momentum between the spacecraft and the moon. The total orbital energy remains constant, so if the spacecraft gains orbital energy then the moon's orbital energy decreases. Orbital period, which is the time required to complete one orbit about the primary body, is proportional to orbital energy. Therefore, as the spacecraft's orbital period increases (the slingshot effect), the moon's orbital period decreases.

But because the spacecraft is much, much smaller than the moon, the effect on the spacecraft's orbit is much greater than on the moon's orbit. For example, the Cassini spacecraft weighs about 3,000 kilograms, whereas Titan, the largest of Saturn's moons, weighs about 1023 kilograms. The effect on Cassini is thus about 20 orders of magnitude greater than the effect on Titan is. [1]

*****

It would begin in the early 2030s, with a launch of a roughly half-ton nuclear-powered spacecraft on the world’s largest rocket, designed to go farther and faster than any human-made object has ever gone before. The probe would pass by Jupiter and perhaps later dive perilously close to the sun, in both cases to siphon a fraction of each object’s momentum, picking up speed to supercharge its escape. Then, with the sun and the major planets rapidly receding behind it, the craft would emerge from the haze of primordial dust that surrounds our star system, allowing it an unfiltered glimpse of the feeble all-sky glow from countless far-off galaxies. Forging ahead, it could fly by one or more of the icy, unexplored worlds now known to exist past Pluto. And gazing back, it could seek out the pale blue dot of Earth, looking for hints of our planet’s life that could be seen from nearby stars.

All this would be but a prelude, however, to what McNutt and other mission planners pitch as the probe’s core scientific purpose. About a decade after launch, it would pierce the heliosphere—a cocoonlike region around our solar system created by “winds” of particles flowing from our sun—to reach and study the cosmic rays and clouds of plasma that make up the “interstellar medium” that fills the dark spaces between the stars. Continuing its cruise, by the 2080s it could conceivably have traveled as far as 1,000 astronomical units (AU), or Earth-sun distances, from the solar system, achieving its primary objective at last: an unprecedented bird’s-eye view of the heliosphere that could revolutionize our understanding of our place in the cosmos. [2]

1. How does the slingshot effect (or gravity assist) work to change the orbit of a spacecraft? Scientific American, July 11, 2005
Jeremy B. Jones, Cassini Navigation Team Chief at NASA's Jet Propulsion Laboratory
2. Proposed Interstellar Mission Reaches for the Stars, One Generation at a Time
Scientific American, Lee Billings, November 2019

TEPCE...

Posted by Reginald L. Goodwin on November 5, 2019 at 5:00am

Image source: Futurism/Dan Robitzski

Topics: Astrophysics, Instrumentation, Space, Space Junk

A massive cloud of space junk—containing more than 23,000 pieces larger than 10 centimeters across—is currently zooming around Earth with an average speed of about 36,000 kilometers per hour. And as companies such as SpaceX and OneWeb plan to launch tens of thousands of new satellites over the next few years, this hazardous clutter will likely pose an increasing threat to space missions and astronauts. One possible solution may be an electrodynamic tether, a device that could help prevent future satellites from becoming abandoned wrecks. The U.S. Naval Research Laboratory plans to test this technology in the next few weeks.

In early November the Tether Electrodynamic Propulsion CubeSat Experiment (TEPCE), already in orbit, is set to make its move under the watchful gaze of telescopes on the Hawaiian island of Maui. The Earth-bound control team is waiting for an ideal 10-minute period at dawn or dusk, when the dim sunlight will offer the best possible view of the shoe box-size spacecraft involved. Once the crew triggers the process, TEPCE should separate into two identical minisatellites joined by a kilometer-long tether as thick as several strands of dental floss. If deployment goes smoothly, the mission can observe how the tether interacts with Earth’s magnetic field in the ionosphere (where much of the space junk orbits) to change the satellites’ velocity and orbit; the results could possibly enable future spacecraft to move around while orbiting Earth—without having to carry unwieldy chemical propellant.

“In other words, it is the sailing ship of space,” says Enrico Lorenzini, a professor of energy management engineering at the University of Padova in Italy, who is not involved in the TEPCE mission. But instead of wind, the electrodynamic tether technology moves thanks to the physical laws that govern electric and magnetic fields. A tether in Earth’s ionosphere—an upper atmospheric layer filled with charged particles such as free electrons and positive ions—can collect electrons at one end and emit them at the other, generating an electric current through itself. The electrified tether’s interactions with Earth’s magnetic field produce an impetus known as the Lorentz force, which pushes on the tether in a perpendicular direction.

Kilometer-Long Space Tether Tests Fuel-Free Propulsion
Jeremy Hsu, Scientific American

Galactic Armageddon...

Posted by Reginald L. Goodwin on October 24, 2019 at 5:00am

The planet, called WASP-12b, is so close to its sunlike star that it is superheated to nearly 2,800 degrees Fahrenheit and stretched into a football shape by enormous tidal forces. The atmosphere has ballooned to nearly three times Jupiter's radius and is spilling material onto the star. The planet is 40 percent more massive than Jupiter.

Topics: Astronomy, Astrophysics, Exoplanets, White Dwarfs

Some rocky exoplanets bear a striking resemblance to Earth, according to Alexandra Doyle, Edward Young and colleagues at the University of California at Los Angeles. The team used the properties of light coming from six white-dwarf stars to calculate how much oxygen, iron and other elements were present in planets that once orbited the stars. Their observations suggest that these planets – which were consumed by their stars long ago – have the same geophysical and geochemical properties as Earth. While astronomers are able to observe rocky exoplanets, working out what they are made of is difficult and this research provides important clues regarding the composition of these Earth-like objects.

White dwarfs are the ancient remnants of stars that had masses less than about 10 Suns. This means that most stars in the Milky Way will eventually become white dwarfs – including the Sun. Many white dwarfs would have had planets, which would have been consumed by the stars at some point in their stellar evolution. The atmosphere of a white dwarf is expected to comprise only the lightest elements – hydrogen and helium – so the presence of heavier substances in the stellar atmosphere such as magnesium, iron and oxygen means that the star has probably ingested rocky planets or asteroids.

Doomed exoplanets were much like Earth, Hamish Johnston, Physics World

The Gravity of the Matter...

Posted by Reginald L. Goodwin on July 30, 2019 at 5:00am

Testing Einstein: conceptual image showing S0-2 (the blue and green object) as it made its closest approach to the supermassive black hole at the center of the Milky Way. The huge gravitational field of the black hole is illustrated by the distorted grid in space–time. (Courtesy: Nicolle R Fuller/National Science Foundation)

Topics: Astrophysics, Black Holes, Cosmology, Einstein, General Relativity

A key aspect of Einstein’s general theory of relativity has passed its most rigorous test so far. An international team led by Tuan Do and Andrea Ghez at the University of California, Los Angeles confirmed the Einstein equivalence principle (EEP) by analyzing the redshift of light from the star S0-2 at its closest approach to Sagittarius A* – the supermassive black hole at the center of the Milky Way. The study combined over 20 years of existing spectroscopic and astrometric measurements of S0-2 with the team’s own observations.

Since Einstein first proposed his general theory of relativity in 1915, the idea has stood up to intense experimental scrutiny by explaining the behaviors of gravitational fields in the solar system, the dynamics of binary pulsars, and gravitational waves emitted by mergers of black holes.

In 2018, the GRAVITY collaboration carried out a particularly rigorous test – observing S0-2 at its closest approach to Sagittarius A* in its 16-year orbit.

As expected, the GRAVITY astronomers observed a characteristic relativistic redshift in light from S0-2. This redshift is a lengthening of the wavelength of the light and arises from both the motion of the star (the Doppler effect) and the EEP. The latter is a consequence of general relativity and predicts a redshift in light from a source that is in a gravitational field such as that of a supermassive black hole.

Einstein’s general theory of relativity tested by star orbiting a black hole
Sam Jarman, Physics World

There Be Monsters...

Posted by Reginald L. Goodwin on June 6, 2019 at 7:20am

Two views of galaxy Markarian 1216. The red image on the left shows X-ray observations conducted by NASA's Chandra X-Ray Observatory, and the yellowish image on the right is composed of optical observations taken by the Hubble Space Telescope. The brighter colors at the center of the Chandra image represent the increased density of hot gas in the galaxy's core.

Topics: Astronomy, Astrophysics, Cosmology, Dark Matter

X-ray observations of a peculiar galaxy deep within the constellation Hydra (the Sea Serpent) have revealed more dark matter at its core than expected.

The galaxy is almost as old as the universe itself, representatives from NASA's Chandra X-Ray Observatory said in a statement published Monday (June 3). This celestial body, Markarian 1216, went through a different evolution than typical galaxies and is home to stars that are within 10% of the age of the universe.

To study the dark matter within this compact, elliptically shaped galaxy about 295 million light- years from Earth, researchers conducted new observations with the Chandra spacecraft. Markarian 1216 is packed with more dark matter in its core than researchers expected, according to their findings published June 1.

Ancient Galaxy in the 'Sea Serpent' Has More Dark Matter Than Expected, Doris Elin Salazar, Space,com

Twin Paradox...

Posted by Reginald L. Goodwin on May 21, 2019 at 5:00am

Retired astronaut Mark Kelly (left) cracks a slight smile while posing with his identical twin brother, astronaut Scott Kelly (right). As part of NASA's Twins Study, Scott took a long trip to space, while Mark remained on Earth. Researchers then monitored how their bodies reacted to their differing environments. NASA

Topics: Astronaut, Astrophysics, Genetics, NASA, Spaceflight

Brothers compete. So in 2016, when astronaut Scott Kelly returned to Earth after spending a year in space, it must have really annoyed his identical twin brother — retired astronaut Mark Kelly — that Scott was two inches taller than when he left. However, Scott's temporary increase in height was not the only thing that changed during his trip.

As part of NASA's Twins Study, while Scott was in space, Mark went about his daily life on Earth. Over the course of the year-long mission, researchers tracked changes in both brothers' biological markers to pinpoint any variances. Because the twins share the same genetic code, researchers reasoned that any observed differences could tentatively — though not definitively — be linked to Scott's time aboard the International Space Station (ISS). This allowed them to take advantage of a unique opportunity and explore how an extended stay in space may impact the human body.

Based on their results, which were published this week in the journal Science, spaceflight can definitely trigger changes in the human body. But the vast majority of these changes disappear within just a few short months of returning to Earth.

Most notably, the researchers found that living in a microgravity environment can: damage DNA; impact the way thousands of individual genes are expressed; increase the length of telomeres (the shielding caps that protect the ends of our chromosomes); thicken artery walls; modify the microbiome; and increase inflammation — just to name a few.

"This is the dawn of human genomics in space," said Andrew Feinberg, a distinguished professor at Johns Hopkins University and one of the lead investigators for the Twins Study, in a press release. "We developed the methods for doing these types of human genomic studies, and we should be doing more research to draw conclusions about what happens to humans in space."

NASA's Twins Study: Spaceflight changes the human body, but only temporarily
Jake Parks, Astronomy

Our Shrinking Moon...

Posted by Reginald L. Goodwin on May 20, 2019 at 5:00am

New surface features of the Moon have been discovered in a region called Mare Frigoris, outlined here in teal. NASA
Image: New Republic

Topics: Astrophysics, Geophysics, Moon, NASA, Planetary Science

The Moon is shrinking as its interior cools, getting more than about 150 feet (50 meters) skinnier over the last several hundred million years. Just as a grape wrinkles as it shrinks down to a raisin, the Moon gets wrinkles as it shrinks. Unlike the flexible skin on a grape, the Moon’s surface crust is brittle, so it breaks as the Moon shrinks, forming “thrust faults” where one section of crust is pushed up over a neighboring part.

“Our analysis gives the first evidence that these faults are still active and likely producing moonquakes today as the Moon continues to gradually cool and shrink,” said Thomas Watters, senior scientist in the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum in Washington. “Some of these quakes can be fairly strong, around five on the Richter scale.”

Watters is lead author of a study that analyzed data from four seismometers placed on the Moon by the Apollo astronauts using an algorithm, or mathematical program, developed to pinpoint quake locations detected by a sparse seismic network. The algorithm gave a better estimate of moonquake locations. Seismometers are instruments that measure the shaking produced by quakes, recording the arrival time and strength of various quake waves to get a location estimate, called an epicenter. The study was published May 13 in Nature Geoscience.

Shrinking Moon May Be Generating Moonquakes, NASA

Remnants...

Posted by Reginald L. Goodwin on April 22, 2019 at 5:00am

An artist's impression of the planetesimal orbiting on a 2-hour period within the gaseous disc around SDSS J1228+1040 (by Mark Garlick).

Topics: Astronomy, Astrophysics, Exoplanets, Spectrograph, White Dwarfs

When the hydrogen fuel that keeps a star like our sun burning brightly is exhausted, the star expands into a red giant before collapsing into a hot, dense white dwarf. Although the stellar swelling engulfs nearby planets, theoretical models suggest that some planets and planetary cores up to hundreds of kilometers in diameter can survive the star’s death and fall into closer orbit. But identifying solid bodies around a dim stellar core is difficult. Now Christopher Manser (University of Warwick) and colleagues have used a new spectroscopic method to identify a planetesimal orbiting a white dwarf 400 light-years from our solar system.

Astronomers have discovered most exoplanets—including an asteroid-like body orbiting a white dwarf—via the transit method, identifying periodic dimming as an object passes in front of its host star. But the method requires a lucky geometry of the planetary system’s orbital plane relative to Earth. Manser and his team instead turned to short-cadence optical spectroscopy using data from the 10.4 m Gran Telescopio Canarias in Spain. They focused on one of just a few white dwarfs that, based on metal emission lines in the stellar and disk spectra, are suspected to be surrounded by disks of gas and dust. Minute-by-minute observations over several nights in 2017 and 2018 let the researchers deconstruct the light emanating from the disk and determine how much variation had occurred over a year.

A glimpse of a planetary system’s final stages, Rachel Berkowitz, Physics Today

Event Horizon...

Posted by Reginald L. Goodwin on April 11, 2019 at 5:00am

Scientists have obtained the first-ever image of a black hole — at center of the galaxy M87. Credit: Event Horizon Telescope collaboration et al.

Topics: Astrophysics, Black Holes, Cosmology, Einstein

(Yesterday) At six simultaneous press conferences around the globe, astronomers on Wednesday announced they had accomplished the seemingly impossible: taking a picture of a black hole, a cosmic monster so voracious that light itself cannot escape its clutches.

This historic feat, performed by the Event Horizon Telescope (EHT)—a planet-spanning network of radio observatories—required more than a decade of effort. The project’s name refers to a black hole’s most defining characteristic, an “event horizon” set by the object’s mass and spin beyond which no infalling material, including light, can ever return.

“We have taken the first picture of a black hole,” the EHT project’s director, Sheperd Doeleman, said in a news release. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”

The image unveils the shadowy face of a 6.5-billion-solar-mass supermassive black hole at the core of Messier 87 (M87), a large galaxy some 55 million light-years from Earth in the Virgo galaxy cluster. Such objects are a reflection of Einstein’s theory of general relativity, which predicts that only so much material can be squeezed into any given volume before the overwhelming force of its accumulated gravity causes a collapse—a warp in the fabric of spacetime that swallows itself. Left behind is an almost featureless nothingness that, for lack of better terms, scientists simply call a black hole.

"Gargantua," special effects from the movie, Interstellar, 2014 (Kip Thorne et al guessed right):

Image Source: HDQ Walls dot com

At Last, a Black Hole’s Image Revealed, Lee Billings, Scientific American

Lumpy Neutron Stars...

Posted by Reginald L. Goodwin on April 9, 2019 at 5:00am

An artist’s rendition of a neutron star. Credit: Kevin Gill Flickr (CC by 2.0)

Topics: Astronomy, Astrophysics, Einstein, Gravitational Waves, Neutron Stars

Gravitational waves—the ghostly ripples in spacetime first predicted by Einstein and finally detected a century later by advanced observatories—have sparked a revolution in astrophysics, revealing the otherwise-hidden details of merging black holes and neutron stars. Now, scientists have used these waves to open another new window on the universe, providing new constraints on neutron stars' exact shapes. The result will aid researchers in their ongoing quest to understand the inner workings of these exotic objects.

So far, 11 gravitational-wave events have been detected by the LIGO (Laser Interferometer Gravitational-Wave Observatory) interferometers in Washington and Louisiana and the Virgo gravitational-wave observatory in Italy. Of these events, 10 came from mergers of binary black holes, and one from the merger of two neutron stars. In all cases, the form of the waves matched the predictions of Einstein's theory of general relativity.

For the binary black hole events, the passing waves lasted less than a second; for the merging neutron stars, the emissions occurred for about 100 seconds. But such rapid pulses aren't the only types of gravitational waves that could be streaming through the universe. In particular, solitary neutron stars might be emitting detectable gravitational waves as they spin—signals that could reveal important new details of the stars' topography and internal composition.

Gravitational Observatories Hunt for Lumpy Neutron Stars
David Appell, Scientific American

Sagittarius A...

Posted by Reginald L. Goodwin on April 4, 2019 at 5:00am

Getty Images

Topics: Astronomy, Astrophysics, Black Holes, Cosmology, Einstein

They've captured our imaginations for decades, but we've never actually photographed a black hole before – until now.

Next Wednesday, at several press briefings around the world, scientists will apparently unveil humanity's first-ever photo of a black hole, the European Space Agency said in a statement. Specifically, the photo will be of "Sagittarius A," the supermassive black hole that's at the center of our Milky Way galaxy.

But aren't black holes, well, black, and thus invisible, so none of our telescopes can "see" them? Yes – therefore the image we're likely to see will be of the "event horizon," the edge of the black hole where light can't escape. [1]

*****

Next week, a collection of countries around the world are going to make a big announcement, and no one is sure exactly what it’s going to be. However, there are some possibilities, and the most exciting one is that they are about to reveal the first-ever photograph of the event horizon of a black hole.

Taking a photo of a black hole is not an easy task. Not only are black holes famous for not letting any light escape, even the nearest known black holes are very far away. The specific black hole astronomers wanted to photograph, Sagittarius A*, lies at the center of our galaxy 25,000 light-years away.

The international Event Horizon Telescope project announced its plan to photograph Sagittarius A* back in 2017, and they enlisted some of the world’s biggest telescopes to help out. The researchers used half a dozen radio telescopes, including the ALMA telescope in Chile and the James Clerk Maxwell telescope in Hawaii, to stare at Sagittarius A* over the past two years.

And while a picture of the black hole itself is impossible, the EHT astronomers were really aiming at the next best thing: the event horizon, the border of the black hole beyond which not even light can escape. At the event horizon, gravity is so strong that light will orbit the black hole like planets orbit stars, and our telescopes should be able to pick that up. [2]

1. 'Something no human has seen before': The first-ever photograph of a black hole will likely be unveiled next week, Doyle Rice, USA Today
2. We Might Be About to See the First Ever Photo of a Black Hole, Avery Thomson, Popular Mechanics

astrophysics (79)

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