The most recent issue of Free Astronomy Magazine (September-October 2020) is available for your reading and downloading pleasure at www.astropublishing.com.
September-October 2020 includes a selected survey of astronomical content of local and cosmological interest from NASA/ESA, ESO, ALMA, as well as two feature articles from our fearless leader/editor Michele Ferrara. The feature articles in this issue discuss:
“Betelgeuse – 100 years of uncertainties” – this article was 100 years in the making, but found itself updated with as-of-August scientific reporting in the final 100 hours before going to print (well, 150). The previous (pre-August) analyses were believed to be an adequate explanation, then the new reports indicate that that previous explanation did not, by itself, explain everything observed by us all since late last year.
“In the mind of ET” – Continuing a multi-issue exobiology thread, this next article is a very interest perspective on the state of the search for extraterrestrial intelligence (and not just SETI), based on the recent NASA award of Adam Frank (and collaborators) at the University of Rochester.
For those wanting a quick look at what the issue has to offer, the Table of Contents is reproduced below.
Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in March, 2016.
By Dr. Ethan Siegel
Imagine a world very different from our own: permanently shrouded in clouds, where the sky was never seen. Never had anyone see the Sun, the Moon, the stars or planets, until one night, a single bright object shone through. Imagine that you saw not only a bright point of light against a dark backdrop of sky, but that you could see a banded structure, a ringed system around it and perhaps even a bright satellite: a moon. That’s the magnitude of what LIGO (the Laser Interferometer Gravitational-wave Observatory) saw, when it directly detected gravitational waves for the first time.
An unavoidable prediction of Einstein’sGeneral Relativity, gravitational waves emerge whenever a mass gets accelerated. For most systems — like Earth orbiting the Sun — the waves are so weak that it would take many times the age of the Universe to notice. But when very massive objects orbit at very short distances, the orbits decay noticeably and rapidly, producing potentially observable gravitational waves. Systems such as the binary pulsar PSR B1913+16 [the subtlety here is that binary pulsars may contain a single neutron star, so it’s best to be specific], where two neutron stars orbit one another at very short distances, had previously shown this phenomenon of orbital decay, but gravitational waves had never been directly detected until now.
When a gravitational wave passes through an objects, it simultaneously stretches and compresses space along mutually perpendicular directions: first horizontally, then vertically, in an oscillating fashion. The LIGO detectors work by splitting a laser beam into perpendicular “arms,” letting the beams reflect back and forth in each arm hundreds of times (for an effective path lengths of hundreds of km), and then recombining them at a photodetector. The interference pattern seen there will shift, predictably, if gravitational waves pass through and change the effective path lengths of the arms. Over a span of 20 milliseconds on September 14, 2015, both LIGO detectors (in Louisiana and Washington) saw identical stretching-and-compressing patterns. From that tiny amount of data, scientists were able to conclude that two black holes, of 36 and 29 solar masses apiece, merged together, emitting 5% of their total mass into gravitational wave energy, via Einstein’s E = mc2.
During that event, more energy was emitted in gravitational waves than by all the stars in the observable Universe combined. The entire Earth was compressed by less than the width of a proton during this event, yet thanks to LIGO’s incredible precision, we were able to detect it. At least a handful of these events are expected every year. In the future, different observatories, such as NANOGrav (which uses radiotelescopes to the delay caused by gravitational waves on pulsar radiation) and the space mission LISA will detect gravitational waves from supermassive black holes and many other sources. We’ve just seen our first event using a new type of astronomy, and can now test black holes and gravity like never before.
Caption: Observation of Gravitational Waves from a Binary Black Hole Merger B. P. Abbott et al., (LIGO Scientific Collaboration and Virgo Collaboration), Physical Review Letters 116, 061102 (2016). This figure shows the data (top panels) at the Washington and Louisiana LIGO stations, the predicted signal from Einstein’s theory (middle panels), and the inferred signals (bottom panels). The signals matched perfectly in both detectors. Click for a larger view.
About NASA Space Place
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The NASA News service provides up-to-date announcements of NASA policy, news events, and space science. A recent selection of space science articles are provided below, including direct links to the full announcements. Those interested in receiving these news announcements directly from NASA can subscribe to their service by sending an email to:
When NASA launches its next mission on the journey to Mars – a stationary lander in 2016 – the flight will include two CubeSats. This will be the first time CubeSats have flown in deep space. If this flyby demonstration is successful, the technology will provide NASA the ability to quickly transmit status information about the main spacecraft after it lands on Mars.
The twin communications-relay CubeSats, being built by NASA’s Jet Propulsion Laboratory (JPL), Pasadena, California, constitute a technology demonstration called Mars Cube One (MarCO). CubeSats are a class of spacecraft based on a standardized small size and modular use of off-the-shelf technologies. Many have been made by university students, and dozens have been launched into Earth orbit using extra payload mass available on launches of larger spacecraft.
The basic CubeSat unit is a box roughly 4 inches (10 centimeters) square. Larger CubeSats are multiples of that unit. MarCO’s design is a six-unit CubeSat – about the size of a briefcase — with a stowed size of about 14.4 inches (36.6 centimeters) by 9.5 inches (24.3 centimeters) by 4.6 inches (11.8 centimeters).
NASA and the United Nations Office for Outer Space Affairs (UNOOSA) have launched a global photography competition to highlight how the vantage point of space helps us better understand our home planet, improve lives, and safeguard our future by aiding sustainable development on Earth.
To highlight the role of space-based science and technologies and their applications on Earth, NASA and UNOOSA are inviting the public to submit photos depicting why space matters to us all in our daily lives. To participate, post a picture and description on Instagram using the hashtag #whyspacematters and tagging @UNOOSA.
NASA astronaut Scott Kelly, who is three months into a one-year mission aboard the International Space Station, will announce the winning photo each month by posting it from his Instagram account @StationCDRKelly.
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For more information about the International Space Station and its crews and research, visit: www.nasa.gov/station
All Systems Go For NASA’s Mission To Jupiter Moon Europa
Beyond Earth, Jupiter’s moon Europa is considered one of the most promising places in the solar system to search for signs of present-day life, and a new NASA mission to explore this potential is moving forward from concept review to development.
NASA’s mission concept — to conduct a detailed survey of Europa and investigate its habitability — has successfully completed its first major review by the agency and now is entering the development phase known as formulation.
“Today we’re taking an exciting step from concept to mission, in our quest to find signs of life beyond Earth,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “Observations of Europa have provided us with tantalizing clues over the last two decades, and the time has come to seek answers to one of humanity’s most profound questions.”
NASA’s Galileo mission to Jupiter in the late 1990s produced strong evidence that Europa, about the size of Earth’s moon, has an ocean beneath its frozen crust. If proven to exist, this global ocean could hold more than twice as much water as Earth. With abundant salt water, a rocky sea floor, and the energy and chemistry provided by tidal heating, Europa may have the ingredients needed to support simple organisms.
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For more information about NASA’s mission to Europa, visit: www.nasa.gov/europa
Veteran NASA Spacecraft Nears 60,000th Lap Around Mars, No Pit Stops
NASA’s Mars Odyssey spacecraft will reach a major milestone June 23, when it completes its 60,000th orbit since arriving at the Red Planet in 2001.
Named after the bestselling novel “2001: A Space Odyssey” by Arthur C. Clarke, Odyssey began orbiting Mars almost 14 years ago, on Oct. 23, 2001. On Dec. 15, 2010, it became the longest-operating spacecraft ever sent to Mars, and continues to hold that record today.
Odyssey, which discovered widespread water ice just beneath the surface of the Red Planet, is still going strong today, serving as a key communications relay for NASA’s Mars rovers and making continued contributions to planetary science.
Astronomers using NASA’s Chandra X-ray Observatory have discovered the largest and brightest set of rings from X-ray light echoes ever observed. These extraordinary rings, produced by an intense flare from a neutron star, provide astronomers a rare chance to determine how far across the Milky Way galaxy the star is from Earth.
The rings appear as circles around Circinus X-1, a double star system in the plane of our galaxy containing a neutron star, the dense remnant of a massive star pulverized in a supernova explosion. The neutron star is in orbit with another massive star, and is shrouded by thick clouds of interstellar gas and dust. Circinus X-1 is also the source of a surprisingly powerful jet of high-energy particles.
“It’s really hard to get accurate distance measurements in astronomy and we only have a handful of methods,” said Sebastian Heinz of the University of Wisconsin in Madison, who led the study. “But just as bats use sonar to triangulate their location, we can use the X-rays from Circinus X-1 to figure out exactly where it is.”
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For more Chandra images, multimedia and related materials, visit: www.nasa.gov/chandra
For an interactive image, podcast, and video about these findings, visit: chandra.si.edu
The AAVSO Writer’s Bureau, hosted by the American Association of Variable Star Observers (www.aavso.org), is a selective aggregator of high-quality science content for the amateur astronomer. Several astronomy bloggers, science writers, and official astronomy publishers and organizations provide articles free-of-charge for redistribution through the AAVSO-WB. The five most recent Writer’s Bureau posts are presented below with direct links to the full articles on the author’s own website. CNYO thanks the authors and the AAVSO for making these articles available for free to all astronomy groups!
Will This New Technology Transform Astronomy?
By Monica Young, Sky & Telescope
Back in my former life, I was an X-ray astronomer. While optical astronomy charged ahead with camera technology that benefitted from commercial investment (hello, smartphones), the X-ray detectors I worked with were of a more “homebrew” variety (really good homebrew).
If I point an X-ray telescope at, say, a distant quasar for a few hours, I might get a few hundred photons if I’m lucky. Compare that with an optical image, where the same quasar might emit millions of photons. As a professor of mine once joked, X-rays are so few and far between, they should have names: “Look, there go Peter, Jill, and Harry.”
When Bruce Banner gets angry, he gets big and green and strong and well, vengeful. The Hulk is the stuff of comic book legend and as Mark Ruffalo recently showed us in The Avengers, Banner’s/Hulk’s personality can transform on a dime.
Turns out rapid transformations are the case in astronomy, too! Scientists found a peculiar neutron star that can change from radio pulsar, to X-ray pulsar, back and forth. In the Hulk’s case, a big dose of gamma rays likely fuelled his ability to transform. This star’s superpowers, however, likely come from a companion star.
Fomalhaut itself is a regular A-class star, twice the size of the Sun, accompanied by a smaller, K-class companion. The system made headlines in 2008 when astronomers discovered the controversial exoplanet candidate Fomalhaut b. Even after the dust mostly settled, the planet’s highly elliptical orbit remained unexplained.
It’s unclear whether the planet’s orbit is aligned with the far-out debris disk that rings the young star. And stranger still, the debris disk itself is off-kilter, its center offset from Fomalhaut A by 15 times the Earth-Sun distance.
Taking pictures of astronomical objects is a lot like collecting rainwater in buckets. Photons from your target are the rain, and your telescope is the bucket. The bigger the bucket, the more rain you collect. You get more water if you leave the bucket out longer, too.
So astronomers like to use big telescopes and long exposure times to get faint detail in their cosmic portraits. However, there’s a third option: Use more than one bucket.
When you look through a telescope at a star glowing red, you might ponder: is it skinny or fat?
Although so-called red dwarfs and red giants have the same temperature, the distinction between them is profound. Red dwarfs are half the mass of the Sun or smaller. A red giant can be many times the mass of the Sun. It’s also about to die — low on energy, it’s bloated to as much as 1,500 times the radius of the Sun.
Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in June, 2013.
By Dr. Martin C. Weisskopf
The idea for the Chandra X-Ray Observatory was born only one year after Riccardo Giacconi discovered the first celestial X-ray source other than the Sun. In 1962, he used a sounding rocket to place the experiment above the atmosphere for a few minutes. The sounding rocket was necessary because the atmosphere blocks X-rays. If you want to look at X-ray emissions from objects like stars, galaxies, and clusters of galaxies, your instrument must get above the atmosphere.
Giacconi’s idea was to launch a large diameter (about 1 meter) telescope to bring X-rays to a focus. He wanted to investigate the hazy glow of X-rays that could be seen from all directions throughout the sounding rocket flight. He wanted to find out whether this glow was, in fact, made up of many point-like objects. That is, was the glow actually from millions of X-ray sources in the Universe. Except for the brightest sources from nearby neighbors, the rocket instrument could not distinguish objects within the glow.
Giacconi’s vision and the promise and importance of X-ray astronomy was borne out by many sounding rocket flights and, later satellite experiments, all of which provided years-, as opposed to minutes-, worth of data.
By 1980, we knew that X-ray sources exist within all classes of astronomical objects. In many cases, this discovery was completely unexpected. For example, that first source turned out to be a very small star in a binary system with a more normal star. The vast amount of energy needed to produce the X-rays was provided by gravity, which, because of the small star’s mass (about equal to the Sun’s) and compactness (about 10 km in diameter) would accelerate particles transferred from the normal star to X-ray emitting energies. In 1962, who knew such compact stars (in this case a neutron star) even existed, much less this energy transfer mechanism?
X-ray astronomy grew in importance to the fields of astronomy and astrophysics. The National Academy of Sciences, as part of its “Decadal Survey” released in 1981, recommended as its number one priority for large missions an X-ray observatory along the lines that Giacconi outlined in 1963. This observatory was eventually realized as the Chandra X-Ray Observatory, which launched in 1999.
The Chandra Project is built around a high-resolution X-ray telescope capable of sharply focusing X-rays onto two different X-ray-sensitive cameras. The focusing ability is of the caliber such that one could resolve an X-ray emitting dime at a distance of about 5 kilometers!
The building of this major scientific observatory has many stories.
Caption: Composite image of DEM L50, a so-called superbubble found in the Large Magellanic Cloud. X-ray data from Chandra is pink, while optical data is red, green, and blue. Superbubbles are created by winds from massive stars and the shock waves produced when the stars explode as supernovas.
Dr. Weisskopf is project scientist for NASA’s Chandra X-ray Observatory. This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
The goal of the NASA Space Place is “to inform, inspire, and involve children in the excitement of science, technology, and space exploration.” More information is available at their website: http://spaceplace.nasa.gov/
