Showing posts with label Space. Show all posts
Showing posts with label Space. Show all posts

Saturday, September 25, 2021

NASA Releases Interactive Graphic Novel “First Woman”

 


NASA released its first digital, interactive graphic novel on Saturday in celebration of National Comic Book Day. “First Woman: NASA’s Promise for Humanity” imagines the story of Callie Rodriguez, the first woman to explore the Moon.

While Callie’s story is fictional, the first woman and the first person of color will walk on the Moon, achieving these historic milestones as part of NASA’s Artemis missions. Through this graphic novel, NASA aims to inspire the next generation of explorers – the Artemis Generation.

Download, read, and interact with “First Woman” or listen to the audio version exclusively on NASA’s SoundCloud.

“The story of Callie captures how passion, dedication, and perseverance allow us to turn our dreams into reality,” said NASA Deputy Administrator Pam Melroy. “Callie, much like myself, grew her skills, seized learning opportunities, and overcame challenges to become a NASA astronaut. Her diversity is reflected in our own astronaut corps today – it's important we can see ourselves as the explorers among the stars.”

The 40-page comic book highlights NASA technologies for traveling to, landing on, and exploring the Moon. The digital format comes to life, letting readers engage and interact through augmented reality elements using the First Woman website or their mobile devices.

Readers can download the First Woman application for Android or iOS to explore life-sized environments and 3D objects, including NASA’s Orion spacecraft and the lunar surface. Additional content includes videos, games, challenges to earn collector badges, and ways to virtually participate in NASA missions.

“We crafted this graphic novel and digital ecosystem to share NASA’s work in a different and exciting way,” said Derek Wang, director of communications for the Space Technology Mission Directorate at the agency’s Headquarters in Washington. “We set out to make the content both engaging and accessible. From space fans of all ages to hardworking educators looking for new ways to get students excited about STEM, we hope that there is something for everyone to enjoy.”

NASA plans to release a Spanish version of the first issue of the comic book, “From Dream to Reality,” on the website in the future.

Source/Credit: NASA

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Monday, September 6, 2021

Hubble Discovers Hydrogen-Burning White Dwarfs Enjoying Slow Ageing

To investigate the physics underpinning white dwarf evolution, astronomers compared cooling white dwarfs in two massive collections of stars: the globular clusters M3 and M13. These two clusters share many physical properties such as age and metallicity but the populations of stars which will eventually give rise to white dwarfs are different. This makes M3 and M13 together a perfect natural laboratory in which to test how different populations of white dwarfs cool.
Image credit: ESA/Hubble & NASA, G. Piotto et al.

Could dying stars hold the secret to looking younger? New evidence from the NASA/ESA Hubble Space Telescope suggests that white dwarfs could continue to burn hydrogen in the final stages of their lives, causing them to appear more youthful than they actually are. This discovery could have consequences for how astronomers measure the ages of star clusters.

The prevalent view of white dwarfs as inert, slowly cooling stars has been challenged by observations from the NASA/ESA Hubble Space Telescope. An international group of astronomers have discovered the first evidence that white dwarfs can slow down their rate of ageing by burning hydrogen on their surface.

“We have found the first observational evidence that white dwarfs can still undergo stable thermonuclear activity,” explained Jianxing Chen of the Alma Mater Studiorum Università di Bologna and the Italian National Institute for Astrophysics, who led this research. “This was quite a surprise, as it is at odds with what is commonly believed.”

White dwarfs are the slowly cooling stars which have cast off their outer layers during the last stages of their lives. They are common objects in the cosmos; roughly 98% of all the stars in the Universe will ultimately end up as white dwarfs, including our own Sun [1]. Studying these cooling stages helps astronomers understand not only white dwarfs, but also their earlier stages as well.

To investigate the physics underpinning white dwarf evolution, astronomers compared cooling white dwarfs in two massive collections of stars: the globular clusters M3 and M13 [2]. These two clusters share many physical properties such as age and metallicity [3] but the populations of stars which will eventually give rise to white dwarfs are different. In particular, the overall colour of stars at an evolutionary stage known as the Horizontal Branch are bluer in M13, indicating a population of hotter stars. This makes M3 and M13 together a perfect natural laboratory in which to test how different populations of white dwarfs cool.

“The superb quality of our Hubble observations provided us with a full view of the stellar populations of the two globular clusters,” continued Chen. “This allowed us to really contrast how stars evolve in M3 and M13.”

Using Hubble’s Wide Field Camera 3 the team observed M3 and M13 at near-ultraviolet wavelengths, allowing them to compare more than 700 white dwarfs in the two clusters. They found that M3 contains standard white dwarfs which are simply cooling stellar cores. M13, on the other hand, contains two populations of white dwarfs: standard white dwarfs and those which have managed to hold on to an outer envelope of hydrogen, allowing them to burn for longer and hence cool more slowly.

Comparing their results with computer simulations of stellar evolution in M13, the researchers were able to show that roughly 70% of the white dwarfs in M13 are burning hydrogen on their surfaces, slowing down the rate at which they are cooling. 

This discovery could have consequences for how astronomers measure the ages of stars in the Milky Way. The evolution of white dwarfs has previously been modelled as a predictable cooling process. This relatively straightforward relationship between age and temperature has led astronomers to use the white dwarf cooling rate as a natural clock to determine the ages of star clusters, particularly globular and open clusters. However, white dwarfs burning hydrogen could cause these age estimates to be inaccurate by as much as 1 billion years.

“Our discovery challenges the definition of white dwarfs as we consider a new perspective on the way in which stars get old,” added Francesco Ferraro of the Alma Mater Studiorum Università di Bologna and the Italian National Institute for Astrophysics, who coordinated the study. “We are now investigating other clusters similar to M13 to further constrain the conditions which drive stars to maintain the thin hydrogen envelope which allows them to age slowly”. 

Notes

[1] The Sun is only 4.6 billion years through its roughly 10-billion-year lifetime. Once it exhausts hydrogen in its core, the Sun will swell into a red giant, engulfing the inner planets and searing the Earth’s surface. It will then throw off its outer layers, and the exposed core of the Sun will be left as a slowly cooling white dwarf. This stellar ember will be incredibly dense, packing a large fraction of the mass of the Sun into a roughly Earth-sized sphere.

[2] M3 contains roughly half a million stars and lies in the constellation Canes Venatici. M13 — occasionally known as the Great Globular Cluster in Hercules — contains slightly fewer stars, only several hundred thousand. White dwarfs are often used to estimate the ages of globular clusters, and so a significant amount of Hubble time has been dedicated to exploring white dwarfs in old and densely populated globular clusters. Hubble directly observed white dwarfs in globular star clusters for the first time in 2006.

[3] Astronomers use the word “metallicity” to describe the proportion of a star which is composed of elements other than hydrogen and helium. The vast majority of matter in the Universe is either hydrogen or helium — to take the Sun as an example, 74.9% of its mass is hydrogen, 23.8% is helium, and the remaining 1.3% is a mixture of all the other elements, which astronomers refer to as “metals”

Source/Credit: ESA/Hubble

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Thursday, September 2, 2021

A Black Hole Triggers a Premature Supernova

 

Dillon Dong, with a 27-meter radio dish at
Caltech's Owens Valley Radio Observatory in the background.
In 2017, a particularly luminous and unusual source of radio waves was discovered in data taken by the Very Large Array (VLA) Sky Survey, a project that scans the night sky in radio wavelengths. Now, led by Caltech graduate student Dillon Dong (MS '18), a team of astronomers has established that the bright radio flare was caused by a black hole or neutron star crashing into its companion star in a never-before-seen process.

"Massive stars usually explode as supernovae when they run out of nuclear fuel," says Gregg Hallinan, professor of astronomy at Caltech. "But in this case, an invading black hole or neutron star has prematurely triggered its companion star to explode." This is the first time a merger-triggered supernova has ever been confirmed.

Bright Flares in the Night Sky

Hallinan and his team look for so-called radio transients—short-lived sources of radio waves that flare
brightly and burn out quickly like a match lit in a dark room. Radio transients are an excellent way to identify unusual astronomical events, such as massive stars that explode and blast out energetic jets or the mergers of neutron stars.

As Dong sifted through the VLA's massive dataset, he singled out an extremely luminous source of radio waves from the VLA survey called VT 1210+4956. This source is tied for the brightest radio transient ever associated with a supernova.

Dong determined that the bright radio energy was originally a star surrounded by a thick and dense shell of gas. This gas shell had been cast off the star a few hundred years before the present day. VT 1210+4956, the radio transient, occurred when the star finally exploded in a supernova and the material ejected from the explosion interacted with the gas shell. Yet, the gas shell itself, and the timescale on which it was cast off from the star, were unusual, so Dong suspected that there might be more to the story of this explosion.

Two Unusual Events

Following Dong's discovery, Caltech graduate student Anna Ho (PhD '20) suggested that this radio transient be compared with a different catalog of brief bright events in the X-ray spectrum. Some of these X-ray events were so short-lived that they were only present in the sky for a few seconds of Earth time. By examining this other catalog, Dong discovered a source of X-rays that originated from the same spot in the sky as VT 1210+4956. Through careful analysis, Dong established that the X-rays and the radio waves were likely coming from the same event.

Gregg Hallinan

"The X-ray transient was an unusual event—it signaled that a relativistic jet was launched at the time of the explosion," says Dong. "And the luminous radio glow indicated that the material from that explosion later crashed into a massive torus of dense gas that had been ejected from the star centuries earlier. These two events have never been associated with each other, and on their own they're very rare."

A Mystery Solved

So, what happened? After careful modeling, the team determined the most likely explanation—an event that involved some of the same cosmic players that are known to generate gravitational waves.

They speculated that a leftover compact remnant of a star that had previously exploded—that is, a black hole or a neutron star—had been closely orbiting around a star. Over time, the black hole had begun siphoning away the atmosphere of its companion star and ejecting it into space, forming the torus of gas. This process dragged the two objects ever closer until the black hole plunged into the star, causing the star to collapse and explode as a supernova.

The X-rays were produced by a jet launched from the core of the star at the moment of its collapse. The radio waves, by contrast, were produced years later as the exploding star reached the torus of gas that had been ejected by the inspiraling compact object.

Astronomers know that a massive star and a companion compact object can form what is called a stable orbit, in which the two bodies gradually spiral closer and closer over an extremely long period of time. This process forms a binary system that is stable for millions to billions of years but that will eventually collide and emit the kind of gravitational waves that were discovered by LIGO in 2015 and 2017.

However, in the case of VT 1210+4956, the two objects instead collided immediately and catastrophically, producing the blasts of X-rays and radio waves observed. Although collisions such as this have been predicted theoretically, VT 1210+4956 provides the first concrete evidence that it happens.

Serendipitous Surveying

The VLA Sky Survey produces enormous amounts of data about radio signals from the night sky, but sifting through that data to discover a bright and interesting event such as VT 1210+4956 is like finding a needle in a haystack. Finding this particular needle, Dong says, was, in a way, serendipitous.

"We had ideas of what we might find in the VLA survey, but we were open to the possibility of finding things we didn't expect," explains Dong. "We created the conditions to discover something interesting by conducting loosely constrained, open-minded searches of large data sets and then taking into account all of the contextual clues we could assemble about the objects that we found. During this process you find yourself pulled in different directions by different explanations, and you simply let nature tell you what's out there."

The paper is titled "A transient radio source consistent with a merger-triggered core collapse supernova." Dillon Dong is the first author. In addition to Hallinan and Ho, additional co-authors are Ehud Nakar, Andrew Hughes, Kenta Hotokezaka, Steve Myers (PhD '90), Kishalay De (MS '18, PHD '21), Kunal Mooley (PhD '15), Vikram Ravi, Assaf Horesh, Mansi Kasliwal (MS '07, PhD '11), and Shri Kulkarni. Funding was provided by the National Science Foundation, the United States–Israel Binational Science Foundation, the I-Core Program of the Planning and Budgeting Committee and the Israel Science Foundation, Canada's Natural Sciences and Engineering Research Council, the Miller Institute for Basic Research in Science at the UC Berkeley, the Japan Society for the Promotion of Science Early-Career Scientists Program, the National Radio Astronomy Observatory, and the Heising-Simons Foundation.

A paper about the findings will appear in the journal Science on September 3.

Source/Credit: California Institute of Technology / Lori Dajose

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Sunday, August 29, 2021

Will it be safe for humans to fly to Mars?

 

Credit: NASA
Sending human travelers to Mars would require scientists and engineers to overcome a range of technological and safety obstacles. One of them is the grave risk posed by particle radiation from the sun, distant stars and galaxies.

Answering two key questions would go a long way toward overcoming that hurdle: Would particle radiation pose too grave a threat to human life throughout a round trip to the red planet? And, could the very timing of a mission to Mars help shield astronauts and the spacecraft from the radiation?

In a new article published in the peer-reviewed journal Space Weather, an international team of space scientists, including researchers from UCLA, answers those two questions with a “no” and a “yes.”

That is, humans should be able to safely travel to and from Mars, provided that the spacecraft has sufficient shielding and the round trip is shorter than approximately four years. And the timing of a human mission to Mars would indeed make a difference: The scientists determined that the best time for a flight to leave Earth would be when solar activity is at its peak, known as the solar maximum.

The scientists’ calculations demonstrate that it would be possible to shield a Mars-bound spacecraft from energetic particles from the sun because, during solar maximum, the most dangerous and energetic particles from distant galaxies are deflected by the enhanced solar activity.

A trip of that length would be conceivable. The average flight to Mars takes about nine months, so depending on the timing of launch and available fuel, it is plausible that a human mission could reach the planet and return to Earth in less than two years, according to Yuri Shprits, a UCLA research geophysicist and co-author of the paper.

“This study shows that while space radiation imposes strict limitations on how heavy the spacecraft can be and the time of launch, and it presents technological difficulties for human missions to Mars, such a mission is viable,” said Shprits, who also is head of space physics and space weather at GFZ Research Centre for Geosciences in Potsdam, Germany.

The researchers recommend a mission not longer than four years because a longer journey would expose astronauts to a dangerously high amount of radiation during the round trip — even assuming they went when it was relatively safer than at other times. They also report that the main danger to such a flight would be particles from outside of our solar system.

Shprits and colleagues from UCLA, MIT, Moscow’s Skolkovo Institute of Science and Technology and GFZ Potsdam combined geophysical models of particle radiation for a solar cycle with models for how radiation would affect both human passengers — including its varying effects on different bodily organs — and a spacecraft. The modeling determined that having a spacecraft’s shell built out of a relatively thick material could help protect astronauts from radiation, but that if the shielding is too thick, it could actually increase the amount of secondary radiation to which they are exposed.

The two main types of hazardous radiation in space are solar energetic particles and galactic cosmic rays; the intensity of each depends on solar activity. Galactic cosmic ray activity is lowest within the six to 12 months after the peak of solar activity, while solar energetic particles’ intensity is greatest during solar maximum, Shprits said.

Source / Credit: UCLA

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