It is probably a safe bet that even as children, Universe Today readers gazed at the night sky with awe and wonder. Did you wish upon the first star light, star bright in the sky? Cultures across time have spun tales around constellations – images projected on the night’s expanse based on our perceptions. As science and technology progressed we realized the vast depths of space are truly full of wonder. There’s an incredible array of amazing things to be discovered, researched and understood.
The images within the chapters are well appointed. For example, at the beginning of the book during a journey from prehistory-1600 you’ll find a fantastic Library of Congress image of the Great Bear constellation, joined by the British Library’s ancient Chinese Star Map, that dates back to the 600’s A.D. This reviewer will definitely be trying some of the activities explained among the chapters such as “Make a 3-D Starscape” found on page 32. This craft project demonstrates the artificial grouping we’ve given our constellations and shows that they are actually comprised of stars great distances from each other and us.
Perhaps the best review of this book comes from my 8 year old daughter. For the past week, she has been reading this book in the car while travelling to school. A recent morning’s question from the back seat was “What’s a pulsar?” She’s excited to try all of the activities; first up will be making a radio picture found on page 82 or turning a friend into a pulsar by spinning them in a chair with two flashlights on page 89. In addition to her “two thumbs” up eagerness to read this every morning, she simply stated “I love this book.”
I extend a thank you to the author for creating a fun, educational STEM source that attracted not only the attention of my science oriented 14 year old boy, but also my daughter, who is as equally bright, capable and curious about the world around her.
OK, it’s a bad gag, I know. But the movie Man of Steel isn’t the only thing that’s “super” about June this year. The closest full Moon of 2013 occurs on June 23, when it will be 356,991 kilometres from Earth, within 600 kilometres of its closest possible approach. When the Moon is closest to Earth in its orbit, it also appears just a bit larger in the sky. But that’s if you’re really paying attention, however!
Some claims circulating on the Internet tend to exaggerate how large the Moon will actually appear. And as for the assertions that the Moon will look bright purple or blue on June 23, that’s just not true. As seems to happen every year, the term “supermoon” has once again reared its (ugly?) head across ye ole Internet. Hey, it’s a teachable moment, a good time to look at where the term came from, and examine the wonderful and wacky motion of our Moon.
I’ll let you in on a small secret. Most astronomers, both of the professional and backyard variety, dislike the informal term “supermoon”. It arose in astrology circles over the past few decades, and like the term “Blue Moon” seems to have found new life on the Internet. A better term from the annuals of astronomy for the near-coincidence of the closest approach of the Full Moon would be Perigee Full Moon. And if you really want to be archaic, Proxigean Moon is also acceptable.
On June 23, 2013, the Moon will be full at 7:32 AM EDT/ 11:32 UT, only 20 minutes after it reaches perigee, or its closest point to Earth in its orbit.
You can see the change in apparent size of the Moon (along with a rocking motion of the Moon known as nutation and libration) in this video from the Goddard Space Flight Center’s Scientific Visualization Studio. You can also see full animations for Moon phases and libration for 2013 from the northern hemisphere and southern hemisphere.
And all perigees are not created equal, either. Remember, a Full Moon is an instant in time when the Moon’s longitude along the ecliptic is equal to 180 degrees. Thus, the Full Moon rises (unless you’re reading this from high polar latitudes!) opposite as the Sun sets. Perigee also oscillates over a value of just over 2 Earth radii (14,000 km) from 356,400 to 370,400 km. And while that seems like a lot, remember that the average distance to the Moon is about 60 earth radii, or 385,000 km distant.
Astronomers yearn for kryptonite for the supermoon. The Moon passes nearly as close every 27.55 days, which is the time that it takes to go from one perigee to another, known as an anomalistic month. This is not quite two days shorter than the more familiar synodic month of 29.53 days, the amount of time it takes the Moon to return to similar phase (i.e. New to New, Full to Full, etc).
This offset may not sound like much, but 2 days can add up. Thus, in six months time, we’ll have perigee near New phase and the smallest apogee Full Moon of the year, falling in 2013 on December 19th. Think of the synodic and anomalistic periods like a set of interlocking waves, cycling and syncing every 6-7 months.
You can even see this effect looking a table of supermoons for the next decade;
Super Moons for the Remainder of the Decade 2013-2020.
Year
Date
Perigee Time
Perigee Distance
Time from Full
Notes
2013
June 23
11:11UT
356,989km
< 1 hour
2013
July 21
20:28UT
358,401km
-21 hours
2014
July 13
8:28UT
358,285km
+21 hours
2014
August 10
17:44UT
356,896km
< 1 hour
2014
September 8
3:30UT
358,387km
-22 hours
2015
August 30
15:25UT
358,288km
+20 hours
2015
September 28
1:47UT
356,876km
-1 hour
Eclipse
2015
October 26
13:00UT
358,463km
-23 hours
2016
October 16
23:37UT
357,859km
+19 hours
Farthest
2016
November 14
11:24UT
356,511km
-2 hours
Closest
2017
December 4
8:43UT
357,495km
+16 hours
2018
January 1
21:56UT
356,565km
-4 hours
2019
January 21
19:59UT
357,344km
+14 hours
Eclipse
2019
February 19
9:07UT
356,761km
-6 hours
2020
March 10
6:34UT
357,122km
+12 hours
2020
April 7
18:10UT
356,908km
-8 hours
Sources: The fourmilab Lunar Perigee & Apogee Calculator & NASA’s Eclipse Website 2011-2020.Note: For the sake of this discussion, a supermoon is defined here as a Full Moon occurring within 24 hours of perigee. Other (often arbitrary) definitions exist!
Note that the supermoon slowly slides through our modern Gregorian calendar by roughly a month a year.
In fact, the line of apsides (an imaginary line drawn bisecting the Moon’s orbit from perigee to apogee) completes one revolution every 8.85 years. Thus, in 2022, the supermoon will once again occur in the June-July timeframe.
To understand why this is, we have to look at another unique feature of the Moon’s orbit. Unlike most satellites, the Moon’s orbit isn’t fixed in relation to its primaries’ (in this case the Earth’s) equator. Earth rotational pole is tilted 23.4 degrees in relation to the plane of its orbit (known as the ecliptic), and the Moon’s orbit is set at an inclination of 5.1 degrees relative to the ecliptic. In this sense, the Earth-Moon system behaves like a binary planet, revolving around a fixed barycenter.
The two points where the Moon’s path intersects the ecliptic are known as the ascending and descending nodes. These move around the ecliptic as well, lining up (known as a syzygy) during two seasons a year to cause lunar and solar eclipses.
The complex motion of the Moon, depicting the movement of the nodes versus the average movement of the line of apsides. (Credit: Geologician, Homunculus 2. Wikimedia Commons graphic under a Creative Common Attribution 3.0 Unported license).
But our friend the line of apsides is being dragged backwards relative to the motion of the nodes, largely by the influence of our Sun. Not only does this cause the supermoons to shift through the calendar, but the Moon can also ride ‘high’ with a declination of around +/-28 degrees relative to the celestial equator once every 19 years, as happened in 2006 and will occur again in 2025.
Falling only two days after the solstice, this month’s supermoon is also near where the Sun will be in December and thus will also be the most southerly Full Moon of 2013. Visually, the Full Moon only varies 14% in apparent diameter from 34.1’ (perigee) to 29.3’ (apogee).
Can you see the difference? A side by side comparison of the perigee and apogee Moon. (Credit: Inconstant Moon).
A fun experiment is to photograph the perigee Moon this month and then take an image with the same setup six months later when the Full Moon is near apogee. Another feat of visual athletics would be to attempt to visually judge the Full Moons throughout a given year. Which one do you think is largest & smallest? Can you discern the difference with the naked eye? Of course, you’d also have to somehow manage to insulate yourself from all the supermoon hype!
A comparison of the rising Moon (left) & the Full Moon high in the sky… as you can see, atmospheric refraction actually tends to “shrink” the apparent size of a rising Moon! (Credit & Copyright: Richard Fleet (@dewbow) The Moon Illusion).
Many folks also fall prey to the rising “Moon Illusion.” The Moon isn’t visually any bigger on the horizon than overhead. In fact, you’re about one Earth radii closer to the Moon when it’s at the zenith than on the horizon. This phenomenon is a psychological variant of the Ponzo illusion.
The supermoon of March 19, 2011 (right), compared to an average moon of December 20, 2010 (left). Note the size difference. Image Credit: Marco Langbroek, the Netherlands, via Wikimedia Commons.
Here are some of the things that even a supermoon can’t do, but we’ve actually heard claims for:
– Be physically larger. You’re just seeing the regular-sized Moon, a tiny bit closer.
– Cause Earthquakes. Yes, we can expect higher-than-normal Proxigean ocean tides, and there are measurable land tides that are influenced by the Moon, but no discernible link between the Moon and earthquakes exists. And yes, we know of the 2003 Taiwanese study that suggested a weak statistical correlation. And predicting an Earthquake after it has occurred, (as happened after the 2011 New Zealand quake) isn’t really forecasting, but a skeptical fallacy known as retrofitting.
– Influence human behavior. Well, maybe the 2013 Full Moon will make some deep sky imagers pack it in on Sunday night. Lunar lore is full of such anecdotes as more babies are born on Full Moon nights, crime increases, etc. This is an example the gambler’s fallacy, a matter of counting the hits but not the misses. There’s even an old wives tale that pregnancy can be induced by sleeping in the light of a Full Moon. Yes, we too can think of more likely explanations…
– Spark a zombie apocalypse. Any would-be zombies sighted (Rob Zombie included) during the supermoon are merely coincidental.
Do get out and enjoy the extra illumination provided by this and any other Full Moon, super or otherwise. Also, be thankful that we’ve got a large nearby satellite to give our species a great lesson in celestial mechanics 101!
A 360° horizon panorama taken from southern Alberta on June 5, 2013, showing the Milky Way, a low aurora to the north, perpetual twilight glow to the north (left of centre) and bands of green airglow across the sky, and the ATV-4 Albert Einstein heading to the International Space Station. Credit and copyright: Alan Dyer.
Yep, you really want to click on this image to see the larger version on Flickr. Wow — what a view!!
This is a 360° horizon pan, seen by Alan Dyer — who has an aptly named website, The Amazing Sky. This is a view seen from southern Alberta on June 5, 2013, and there is a lot going on in this image. Alan described it on Flickr: “There’s the Milky Way arching across the sky on the right, a low aurora to the north, perpetual twilight glow to the north (left of center) and bands of green airglow across the sky. Left of the house and also left of the main area of Milky Way are horizon glows from urban light pollution. A satellite, the ESA Einstein ATV going to the ISS, is at left of frame.”
I get extremely excited if I can see *one* of those things in a night, and here Alan has captured all at once — superb!
But wait, there’s more!
On June 10, Alan was able to take a timelapse of the Northern Lights and some noctilucent clouds, and it is gorgeous. See below:
Alan said on his website, “This was certainly one of the best NLC displays I’d seen and my best shot at capturing them.”
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
Thirty-six of the stars in this open star cluster, NGC 3766, are a variable star never seen before. Observations were made with the European Southern Observatory's La Silla Observatory. Credit: ESO
A new kind of variable star — 36 of that type, in fact — has been found in a single star cluster. Astronomers don’t even have a name for the star type yet, but feel free to leave some suggestions in the comments!
For now, however, astronomers are wondering what the implications are for our understanding of the stellar interiors.
“The very existence of this new class of variable stars is a challenge to astrophysicists,” stated Sophie Saesen, an astronomer at Geneva Observatory who participated in the research.
“Current theoretical models predict that their light is not supposed to vary periodically at all, so our current efforts are focused on finding out more about the behaviour of this strange new type of star.”
The head-scratching began when astronomers used a European Southern Observatory telescope to gaze at the “Pearl Cluster” (NGC 3766), an open star cluster about 5,800 light years from Earth.
Over seven years of observations with the Leonhard Euler Telescope (taking periodic measurements of brightness), astronomers spotted 36 stars with variable periods of between 2 and 20 hours.
The four-foot (1.2-meter) Leonhard Euler Telescope at the European Southern Observatory. Credit: M. Tewes/ESO
Variable stars have been known for centuries, and many of them are tracked by amateur organizations such as the American Association of Variable Observers. As best as astronomers can figure, the stars become brighter and dimmer due to changes on the inside — stellar vibrations or “quakes” studied under a field called asteroseismology.
A special type of variable stars, called Cepheid variables, can provide accurate measurements of distance since they have an established ratio between luminosity and the period of their variability.
Studying various types of variable stars has provided some insights.
“Asteroseismology of ß Cep[hei] stars, for example, has opened the doors in the past decade to study their interior rotation and convective core,” the astronomers stated in a paper on the research.
The variations in brightness can be interpreted as vibrations, or oscillations within the stars, using a technique called asteroseismology. The oscillations reveal information about the internal structure of the stars, in much the same way that seismologists use earthquakes to probe the Earth’s interior. Credit: Kepler Astroseismology team.
Despite the well-known nature of variable stars, few of them have been studied in open clusters such as NGC 3766.
The reason is it takes a lot of telescope time to take a look at the star — sometimes, years. And time with telescopes is both expensive and precious, making it difficult to allocate the time required.
“Stellar clusters are ideal environments to study stellar variability because some basic properties and the evolutionary status of individual star members can be derived from the properties of the cluster,” the astronomers stated.
“It, however, requires extensive monitoring on an as-long-as-possible time base line. This requirement may explain why not many clusters have been studied for their variability content so far, compared to the number of known and characterized clusters.”
These particular stars in NGC 3766, however, were puzzling.
“The stars are somewhat hotter and brighter than the Sun, but otherwise apparently unremarkable,” ESO stated, yet they had variations of about 0.1% of each star’s normal brightness.
Cepheid Variable Star. Credit: Hubble Space Telescope
It’s possible, but not proven yet, that perhaps the stars’ spin has something to do with the brightness.
Some of the observed objects whip around at speeds so fast that some material might be punted away from the star and into space, the astronomers wrote in a press release.
“In those conditions, the fast spin will have an important impact on their internal properties, but we are not able yet to adequately model their light variations,” stated Nami Mowlavi, another Geneva Observatory astronomer who led the paper.
Also, astronomers haven’t named this class of stars yet. Do you have any ideas? For more information and to generate suggestions, you can read the paper here in Astronomy & Astrophysics. Then you can leave your thoughts in the comments.
Jacinta studies distant galaxies like those shown in this image from the Hubble Space Telescope, using the new 'stacking' technique to gather information only available through radio telescope observations. Credit: NASA, STScI, and ESA.
Very similar to stacking astronomy images to achieve a better picture, researchers from the International Centre for Radio Astronomy Research (ICRAR) are employing new methods which will give us a clearer look at the history of the Universe. Through data taken with the next generation of radio telescopes like the Square Kilometer Array (SKA), scientists like Jacinta Delhaize can “stack” galactic signals en masse to study one of their most important properties… how much hydrogen gas is present.
Probing the cosmos with a telescope is virtually using a time machine. Astronomers are able to look back at the Universe as it appeared billions of years ago. By comparing the present with the past, they are able to chart its history. We can see how things have changed over the ages and speculate about the origin and future of the vastness of space and all its many wonders.
“Distant, younger, galaxies look very different to nearby galaxies, which means that they’ve changed, or evolved, over time,” said Delhaize. “The challenge is to try and figure out what physical properties within the galaxy have changed, and how and why this has happened.”
According to Delhaize a vital clue to solving the riddle lay in hydrogen gas. By understanding how much of it that galaxies contained will help us map their history.
“Hydrogen is the building block of the Universe, it’s what stars form from and what keeps a galaxy ‘alive’,” said Delhaize.
“Galaxies in the past formed stars at a much faster rate than galaxies now. We think that past galaxies had more hydrogen, and that might be why their star formation rate is higher.”
Jacinta Delhaize with CSIRO’s Parkes Radio Telescope during one of her data collecting trips. Credit: Anita Redfern Photography.When it comes to distant galaxies, they don’t give up their information easily. Even so, it was a task that Delhaize and her supervisors were determined to observe. The faint radio signals of hydrogen gas were nearly impossible to detect, but the new stacking method allowed the team to collect enough data for her research. By combining the weak signals of thousands of galaxies, Delhaize then “stacked” them to create a stronger, averaged signal,
“What we are trying to achieve with stacking is sort of like detecting a faint whisper in a room full of people shouting,” said Delhaize. “When you combine together thousands of whispers, you get a shout that you can hear above a noisy room, just like combining the radio light from thousands of galaxies to detect them above the background.”
However, it wasn’t a slow process. The researchers engaged CSIRO’s Parkes Radio Telescope for 87 hours and surveyed a large region of galactic landscape. Their work collected signals from hydrogen over a vast amount of space and stretched back over two billion years in time.
“The Parkes telescope views a big section of the sky at once, so it was quick to survey the large field we chose for our study,” said ICRAR Deputy Director and Jacinta’s supervisor, Professor Lister Staveley-Smith.
As Delhaize explains, observing such a massive volume of space means more accurate calculations of the average amount of hydrogen gas present in particular galaxies at a certain distance from Earth. These readings correspond to a given period in the history of the Universe. With this data, simulations can be created to depict the Universe’s evolution and give us a better understanding of how galaxies formed and evolved with time. What’s even more spectacular is that next generation telescopes like the international Square Kilometre Array (SKA) and CSIRO’s Australian SKA Pathfinder (ASKAP) will be able to observe even larger volumes of the Universe with higher resolution.
“That makes them fast, accurate and perfect for studying the distant Universe. We can use the stacking technique to get every last piece of valuable information out of their observations,” said Delhaize. “Bring on ASKAP and the SKA!”.
The Jamesburg Earth Station radio dish in Carmel, California will be used to send the Lone Signal messages to space. Image via Lone Signal.
Although scientists have been listening for years to search for indications of other sentient life in the Universe, just a few efforts have been made by humans to purposefully send out messages to the cosmos. Called METI (Messaging to Extraterrestrial Intelligence) or Active SETI (Search for Extraterrestrial Intelligence), these messages have so far been just one-time bursts of info – or “pulses in time” said Dr. Jacob Haqq-Misra.
Haqq-Misra is leading a team of scientists and entrepreneurs who are launching a new initiative called “Lone Signal” which will send the first continuous mass “hailing messages” out into space, starting later this month. They’ll be specifically targeting one star system, Gliese 526, which has been identified as a potentially habitable solar system.
And yes, the general public can participate.
“From the start we wanted to be an experiment where anyone on Earth could participate,” said Haqq-Misra during a press event on June 11, 2013, announcing the project.
“Our scientific goals are to discover sentient beings outside of our solar system,” said Lone Star co-founder Pierre Fabre, also speaking at the event. “But an important part of this project is to get people to look beyond themselves and their differences by thinking about what they would say to a different civilization. Lone Signal will allow people to do that.”
Lone Signal will be using the recommissioned radio dish at the Jamesburg Earth Station in Carmel, California, one of the dishes used to carry the Apollo Moon landings live to the world.
Timelapse of the Jamesburg Earth Station
Lone Signal will be sending two signals: one is a continuous wave (CW) signal, a hailing message that sends a slow binary broadcast to provide basic information about Earth and our Solar System using an encoding system created by astrophysicist and planetary scientist Michael W. Busch. The binary code is based on mathematical “first principles” which reflect established laws that, theoretically, are relatively constant throughout the universe; things like gravity and the structure of the hydrogen atom, etc.
“This hailing message is a language we think could be used to instigate communication,” said Haqq-Misra, “and is the most advanced binary coding currently in use.”
The second signal, embedded in the first signal, will be messages from the people of Earth.
Strength of various signals from Earth. Graph courtesy of Dr. Haqq-Misra.
Since Gliese 526 is 17.6 light years from Earth, the messages will be beamed to the coordinates of where the star will be in 17.6 years from now. Even though no planets have been found yet in this system, the Lone Signal team said they are confident planets exist there since missions like Kepler and Corot have found that most stars host multiple planets.
The Lone Signal team is allowing anyone with access to the internet to send the equivalent of one free text message or Twitter message — a 144-character text-based message — into space. The team said they want to have messages sent from people all around the world to provide messages that are “representative of humanity.”
Anything additional, like more messages, images, etc., will cost money, but those funds will help support the project.
“In effect we are doing our own Kickstarter and doing the crowdfunding on our own,” said Lone Signal CEO Jamie King. “Long Signal would not be possible without crowd sourcing support, which will be used for maintaining the millions of dollars in equipment, powering the dish, running the web portal and other critical tech that makes the project possible.”
If you want to be part of the project and be a “beamer” you can currently sign up at the Lone Signal website –which currently doesn’t have much information. But on June 18th their public site will go live and ‘beamers will be able to submit messages as well as:
• Share Beams / Track Beams – Once signed in, users can see how far their beam has traveled from Earth as well as share it with the beaming community.
• Dedicate Beams – Parents, friends and loved ones can dedicate a beam to others.
• Explore – The Explore section gives beamers current data on the Lone Signal beam, who is sending messages, from where on Earth, overall stats, etc.
• Blog / Twitter – Via their blog and Twitter, the Lone Signal science team and other contributors will be posting opinion articles on associated topics of interest as well as sharing the latest science news and updates.
One you submit your “beam” you’ll be able to “echo” it on your Facebook and Twitter accounts.
After a user sends their initial free message, Lone Signal will be offering paid credit packages for purchase that allow users to transmit and share longer messages as well as images using credits in the following USD price structure:
• $0.99 buys 4 credits.
• $4.99 buys 40 credits.
• $19.99 buys 400 credits.
• $99.99 buys 4000 credits.
Following the initial free message, each subsequent text-based message costs 1 credit. Image-based messages cost 3 credits.
The team said that each message will be sent as an individual packet of information and won’t be bunched with other messages.
While some scientists have indicated that sending messages out into space might pose a hazard by attracting unwanted attention from potentially aggressive extraterrestrial civilizations, Haqq-Misra thinks the benefits outweigh the potential hazards. In fact, he and his team have written a paper about the concept.
“We want to inspire passion for the space sciences in people young and old, encourage citizens of Earth to think about their role in the Universe, and inspire the next generation of scientists and astronauts,” said Lone Signal chief marketing officer Ernesto Qualizza. “We’re really excited to find out what people will want to say, and the science of METI allows people to do this – to think about more than their own backyard.”
Example of an orbital 'selfie' that Planetary Resources' ARKYD telescope could provide to anyone who donates to their new Kickstarter campaign. Credit: Planetary Resources.
A crowdfunded telescope — best known for offering “space selfies” for backers as an incentive to send money — is now considering a search for alien planets.
Planetary Resources Inc. (the proposed asteroid miners) announced a new “stretch goal” for its asteroid-hunting Arkyd-100 telescope.
If the company can raise $2 million — double its original goal — it promises to equip the Arkyd telescope to look at star systems for exoplanets. The project is still short the $1 million required to receive any money, but the target appears to be close enough now to give Planetary Resources confidence that more funds will come for new initiatives.
Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
Because Kepler needs at least three reaction wheels to point towards targets, its future is uncertain. Some planet searching is still possible with ground-based observatories, however.
“With NASA’s recent equipment failure on the Kepler telescope (RIP, Kepler!), our search for extrasolar planets nearly came to a grinding halt. If we can meet our stretch goal, we can resume some of this progress by enhancing the Arkyd,” Arkyd organizers stated on their Kickstarter campaign website.
“We’re partnering with exoplanet researchers at MIT [the Massachusetts Institute of Technology] to equip citizen scientists like YOU with the tools to join a search that’s captivated us for generations.”
Arkyd would use two methods to hunt down planets:
– Transiting, or seeing the dip in a star’s brightness when a planet passes in front of it;
– Gravitational microlensing, or finding planets by measuring how the gravity of the star (and its planets) distorts light from stars and galaxies behind.
With 19 days to go, Arkyd is at about $857,000 of its preliminary $1 million goal that it must reach to receive any money.
If it can raise $1.3 million, Planetary Resources proposes to build a ground station at an undisclosed “educational partner” that would double the download speed of data from the orbiting observatory.
The project has more than 9,500 backers. Two more stretch goals will be revealed if Arkyd receives 11,000 backers and 15,000 backers, Planetary Resources stated.
The globular cluster NGC 6388. Blue stragglers may clearly be seen around the edges. More are hidden within the central core. Credit: ESO
A unique and enigmatic variety of stars known as blue stragglers appear to defy the normal stellar aging process. Discovered in globular clusters, they appear much younger than the rest of the stellar population. Since their discovery in 1953, astronomers have been asking the question: how do these stars regain their youth?
For years, two theories have persisted. The first theory suggests that two stars collide, forming a single more massive star. The second theory proposes that blue stragglers emerge from binary pairs. As the more massive star evolves and expands, it blows material onto the smaller star. In both theories, the star grows steadily more massive and bluer – it regains its youth.
But now, a surprising finding may lend credence to the second theory. Astronomers at the Nicolaus Copernicus Astronomical Center in Poland recently observed a blue straggler caught in the midst of forming!
The binary system that was studied, known as M55-V60, is located within the globular cluster M55. Dr. Michal Rozyczka, one of the research scientists on the project, told Universe Today, “The system is a showcase example of a blue straggler formed via the theoretically predicted peaceful mass exchange between its components.”
The team used both photometric (the overall light from the system) and spectroscopic (the light spread out into a range of wavelengths) observations. The photometric data revealed the light curve – the change in brightness due to one star passing in front of the other – of the system. This provided evidence that the astronomers were looking at a binary system.
From the spectroscopic data, shifts in wavelength reveal the velocity (along the line of sight) of a source. The research team noted that the system’s center of mass was moving with respect to the binary system. This will occur in a semi-detached binary system, where mass transfers from one star to the other. As it does this, the center of mass will follow the mass-transfer.
From both photometric and spectroscopic observations (which covered more than 10 years!) the team was able to verify that this object is not only a binary, but a semi-detached binary, residing at the edge of M55.
An artist’s conception of how a blue straggler may form from a binary system. Credit: NASA/ESA
“The system is semi-detached with the less massive (secondary) component filling its Roche lobe,” explained Dr. Rozyczka. “The secondary has a tearlike shape, with the tip of the tear directed toward the more massive primary. A stream of gas flows out of the tip along a curved path and hits the primary.”
How do we know that it is in fact a blue straggler? The simple answer is that the secondary star, with is gaining mass, appears bluer than normal. This blue straggler is clearly in the process of forming. It is the second observation of such a formation, with the first being V228 in the globular cluster: 47 Tuc.
This research verifies that semi-detached binaries are a viable formation mechanism for blue stragglers. The binary was discovered by happenstance, in a project aimed at determining accurate ages and distances of nearby clusters. It’s certainly a surprising result from the survey.
The results will be published in Acta Astronomica, a peer-reviewed scientific journal located in Poland (preprint available here).
Several types of downhill flow features have been observed on Mars. This image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter is an example of a type called "linear gullies." Image credit: NASA/JPL-Caltech/Univ. of Arizona
Extreme sports taking on place on Mars? How about snowboarding – or actually sandboarding –down Martian dunes on a cushion of carbon dioxide? Sounds fun, and this might be happening already – sans the humanoid snowboarders, however.
Scientists have been wondering what caused unusual hillside grooves on Mars, called linear gullies. New research and test runs down sand dunes here on Earth has shown that these gullies may be formed by chunks of frozen carbon dioxide sliding down some Martian sand dunes on cushions of gas. They are plowing furrows as they slide, and creating open pits at the bottom of the run.
And these are not the Martian Sand Skimmers of Martian Chronicles fame. Just chunks of dry ice going for a joy ride.
“I have always dreamed of going to Mars,” said Serina Diniega, a planetary scientist at NASA’s Jet Propulsion Laboratory and lead author of a report published online by the journal Icarus. “Now I dream of snowboarding down a Martian sand dune on a block of dry ice.”
In images from the Mars Reconnaissance Orbiter’s HiRISE (High Resolution Imaging Science Experiment) camera the linear gullies seem to all have relatively constant width — up to a few yards, or meters, across — with raised banks or levees along the sides. Unlike gullies caused by water flows on Earth and possibly on Mars, they do not have aprons of debris at the downhill end of the gully. Instead, many have pits at the downhill end.
“In debris flows, you have water carrying sediment downhill, and the material eroded from the top is carried to the bottom and deposited as a fan-shaped apron,” said Diniega. “In the linear gullies, you’re not transporting material. You’re carving out a groove, pushing material to the sides.”
HiRISE images show the sand dunes with linear gullies covered by carbon-dioxide frost during the Martian winter. The location of the linear gullies is on dunes that spend the Martian winter covered by carbon-dioxide frost. By comparing before-and-after images from different seasons, researchers determined that the grooves are formed during early spring. Some images have even caught bright objects in the gullies.
Diniega and her team theorize the bright objects are pieces of dry ice that have broken away from points higher on the slope. According to the new hypothesis, the pits could result from the blocks of dry ice completely sublimating away into carbon-dioxide gas after they have stopped traveling.
“Linear gullies don’t look like gullies on Earth or other gullies on Mars, and this process wouldn’t happen on Earth,” said Diniega. “You don’t get blocks of dry ice on Earth unless you go buy them.”
Co-author on the paper Candice Hansen, of the Planetary Science Institute suspected that dry ice might be involved in forming these linear gullies, so like any good planetary scientist she bought some slabs of dry ice at a supermarket and slid them down sand dunes.
And voilà, similar looking linear gullies with the gaseous carbon dioxide from the thawing ice maintaining a lubricating layer under the slab. As the chunk slide down the dune, it also pushed sand aside into small levees. Handsen said the slabs glided down even low-angle slopes, not much pushing required.
Of course, the team said, the outdoor tests did not simulate Martian temperature and pressure, but calculations indicate the dry ice would act similarly in early Martian spring where the linear gullies form. Although water ice, too, can sublimate directly to gas under some Martian conditions, it would stay frozen at the temperatures at which these gullies form, the researchers calculate.
“MRO is showing that Mars is a very active planet,” Hansen said. “Some of the processes we see on Mars are like processes on Earth, but this one is in the category of uniquely Martian.”
Hansen also noted the process could be unique to the linear gullies etched on Martian sand dunes.
“There are a variety of different types of features on Mars that sometimes get lumped together as ‘gullies,’ but they are formed by different processes,” she said. “Just because this dry-ice hypothesis looks like a good explanation for one type doesn’t mean it applies to others.”
Harrumph. Dry ice having fun on Mars fun without us.
The Sculptor galaxy is seen in a new light, in this composite image from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Southern Observatory in Chile. Image credit: NASA/JPL-Caltech/JHU
The Chandra X-ray Observatory has been keeping an eye on a black hole actively munching away on gas at the middle of the nearby Sculptor galaxy. Now, with the added eyes of the Nuclear Spectroscopic Telescope Array (NuSTAR), which sees higher-energy X-ray light, the observatories have found the black hole has fallen asleep, even amid rampant star-formation going on around it.
“Our results imply that the black hole went dormant in the past 10 years,” said Bret Lehmer of the Johns Hopkins University, Baltimore, and NASA’s Goddard Space Flight Center. “Periodic observations with both Chandra and NuSTAR should tell us unambiguously if the black hole wakes up again. If this happens in the next few years, we hope to be watching.”
Lehmer is lead author of a new study detailing the findings in the Astrophysical Journal.
The now-latent black hole is about 5 million times the mass of our Sun. The Sculptor galaxy (NGC 253) is a so-called starburst galaxy, which is actively giving birth to new stars. At just 13 million light-years away, it is one of the closest starbursts galaxies to us.
Why did the black hole go dormant?
“Black holes feed off surrounding accretion disks of material. When they run out of this fuel, they go dormant,” said co-author Ann Hornschemeier of Goddard. “NGC 253 is somewhat unusual because the giant black hole is asleep in the midst of tremendous star-forming activity all around it.”
“Black hole growth and star formation often go hand-in-hand in distant galaxies,” added Daniel Stern, a co-author and NuSTAR project scientist at the Jet Propulsion Laborator. “It’s a bit surprising as to what’s going on here, but we’ve got two powerful complementary X-ray telescopes on the case.”
Chandra first observed signs of what appeared to be a feeding supermassive black hole at the heart of the Sculptor galaxy in 2003. Then, in September and November of 2012, Chandra and NuSTAR observed the same region simultaneously. NuSTAR, which launched in June of 2012, detected focused, high-energy X-ray light from the region, allowing the researchers to say conclusively that the black hole is not accreting material.
There are two possibilities: either the black hole has in fact gone dormant, or another possibility is that the black hole was not actually awake 10 years ago, and Chandra observed a different source of X-rays. Future observations with both telescopes may solve the puzzle.
The combination of coordinated Chandra and NuSTAR observations is extremely powerful for answering questions like this,” said Lou Kaluzienski, NuSTAR Program Scientist at NASA Headquarters in Washington. “Now, we can get all sides of the story.”
NuSTAR launched into space in June of 2012.
If and when the Sculptor’s slumbering giant does wake up in the next few years amidst all the commotion, NuSTAR and Chandra will monitor the situation. The team plans to check back on the system periodically.
