Posted on by Bob King

Tiangong 1 Falls, Blue Moon Rises and Mars Takes Aim At Saturn

Bob King
A couple watches the Moon rise from the icy shore of Lake Superior in Duluth earlier this month on March 1. Credit: Bob King

I apologize for the end-of-the-world title, but everything in it is true. And the world will still be here after it’s all done. On Friday (March 31) at 7:36 a.m. Central Time, the Moon will be full for the second time this month, which makes it a Blue Moon according to popular usage. Enjoy it. What with January’s Blue Moon and now this, we’ve chewed through all our Blue Moons till Halloween 2020.

I look forward to every full moon. Watching a moonrise, we get to see all manner of amazing atmospheric distortions play across the squat, orange disk. Once the sky’s dark, its outpouring of light makes walking at night a pleasure.

When a full moon occurs in spring, it hurries south down the ecliptic, the imaginary circle in the sky defining Earth’s orbit around the Sun. For northern hemisphere skywatchers, this southward sprint delays its rising by more an hour each night, forcing a quick departure from the evening sky. And that means blessed darkness for hunting down favorite galaxies and star clusters.


Tiangong 1 and a reentry simulation

As the Moon rolls along, the hapless Chinese space station Tiangong 1 hurtles toward Earth. Drag caused by friction with the upper atmosphere continues to shrink the spacecraft’s orbit, bringing it closer and closer to inevitable breakup and incineration. Since the Chinese National Space Administration (CNSA) lost touch with Tiangong 1 in March 2016, mission control can no longer power thrusters to de-orbit it at chosen time over a safe location like the ocean. The 9.3-ton (8,500 kg) station will burn up somewhere anywhere over a vast swath of the planet between latitudes 43°N and 43°S. Included within this zone are the southern half of Europe, the southern two-thirds of the U.S., India, Australia and much of Africa and South America.

Not until the day of or even hours before will have a clear idea of when and where the station will meet its fate. According to the latest update from the Aerospace Corp., which monitors falling spacecraft, reentry is expected on Easter Sunday (April 1) at 10:30 UT / 5:30 a.m. Central Time plus or minus 16 hours. This morning (March 29), the space station is circling Earth at about 118 miles (190 km) altitude. The lowest a satelllite can still make a complete orbit of the planet is about 62 miles (100 km). Below that, break-up begins.

A high definition TV camera on an aircraft took this photo of the cargo ship ATV-1 reentering the atmosphere in September 2008. Tiangong 1 is about the same size and will likely shatter and burn in similar fashion. Credit: ESA/NASA

For up-to-the-minute updates on when to expect Tiangong 1’s orbit to decay and the machine to plunge to Earth, check out Joseph Remis’ Twitter page. Most of the space station is expected to burn up on reentry, but larger chunks might survive all the way to the ground. Since much more of the Earth’s surface is water these remnants will likely end up in the drink … but you never know. If Tiangong-1 does come down over a populated area, observers on the ground will witness a spectacular, manmade fireball day or night.

Mars (right) and Saturn pair up in Sagittarius this morning, March 29 at dawn seen from Duluth, Minn. The two planets were 2.2° apart. Details: 35mm lens, f/2.8, 13 second exposure at ISO 800. Credit: Bob King

On the quieter side but nearly as eye-catching, Mars will overtake Saturn in the coming week, passing just 1° south of the ringed planet in a thrilling dawn conjunction on April 2. If the weather forecast doesn’t look promising that morning, the two planets will remain within 2° of each other now through April 6th, providing plenty of opportunities for a look.

You can easily tell them apart by color: Mars is distinctly red-orange and Saturn looks creamy white. Both are bright at around magnitude 0 though Mars is now a hair brighter by two-tenths of a magnitude. Will you be able to see the difference?

Mars passes close to Saturn on Monday, April 2. Look low in the southeastern sky shortly before and at dawn. Try getting a picture of the lovely couple by setting up your camera on a tripod and doing a series of time exposures from 5-30 seconds at f/3.5 and ISO 800. No fancy telephoto equipment is needed: a 35-55mm lens is perfect. Created with Stellarium

In most telescopes at low magnification both planets will comfortably fit in the same field of view. Saturn’s rings are tilted nearly wide open and quite beautiful. Mars appears gibbous and though still rather small, it’s brightening rapidly and drawing closer in time for its closest approach to Earth since 2003. Wishing you clear skies!

Posted on by Matt Williams

Try to Contain Your Surprise. James Webb is Getting Delayed to 2020

Illustration of NASA's James Webb Space Telescope. Credits: NASA
Illustration of NASA's James Webb Space Telescope. Credits: NASA

Once it deploys, the James Webb Space Telescope (JWST) will be the most powerful and technically complex space telescope ever deployed. Using its powerful suite of infrared-optimized instruments, this telescope will be able to study the earliest stars and galaxies in the Universe, extra-solar planets around nearby stars, and the planets, moons and asteroids of our Solar System.

Unfortunately, due to its complexity and the need for more testing, the launch of the JWST has been subject to multiple delays. And as of this morning, NASA announced that the launch JWST has been delayed yet again. According to a statement issued by the agency, the launch window for the JWST is now targeted for sometime around May 2020.

The decision came after an independent assessment by the project’s Standing Review Board (SRB) of the remaining tasks, all of which are part of the final stage of integration and testing before the JWST launches. These tasks consist of integrating the combined optics and science instruments onto the spacecraft element, then testing them to ensure that they will deploy properly and work once they are in space.

The Space Telescope for Air, Road, and Sea (STTARS) is a custom-designed container that holds the James Webb’s Optical Telescope and Integrated Science (OTIS) instrument module. In this image its being unloaded from a U.S. military C-5 Charlie aircraft at Los Angeles International Airport (LAX) on Feb. 2, 2018. Image: NASA/Chris Gunn

This assessment came on the heels of a report issued by the Government Accountability Office (GAO) in February that expressed concerns over further delays and cost overruns. These concerns were based on the fact that it is typically in the final phase when problems are found and schedules revised, and that only 1.5 months of schedule reserved remained (at the time) until the end of the telescope’s launch window – which was scheduled for 2019.

But as acting NASA Administrator Robert Lightfoot stressed, the JWST is still a go:

“Webb is the highest priority project for the agency’s Science Mission Directorate, and the largest international space science project in U.S. history. All the observatory’s flight hardware is now complete, however, the issues brought to light with the spacecraft element are prompting us to take the necessary steps to refocus our efforts on the completion of this ambitious and complex observatory.”

NASA also announced that it is establishing an external Independent Review Board (IRB) chaired by Thomas Young – a highly-respected NASA and industry veteran who has a long history of chairing advisory committees and analyzing organizational and technical issues. The IRB findings, along with the SRB data, will be considered by NASA to set a more specific launch date, and will be presented to Congress this summer.

In the meantime, NASA and the European Space Agency (ESA) will be setting a new launch readiness date for the Ariane 5 rocket that will bring the JWST into space. Once a launch date is set, NASA will also be providing a cost estimate that may exceed the $8 billion budget cap established by Congress in 2011. This too is in keeping with the GAO’s report, which predicted cost overruns.

The Space Telescope Transporter for Air, Road and Sea (STTARS) being opened at Northrop Grumman on March 8th, 2018, to reveal the combined optics and science instruments of NASA’s James Webb Space Telescope. Credits: NASA/Chris Gunn

For those who have been following the JWST’s development, this news should come as no surprise. Due to its complexity and the need for extensive testing, the launch of the JWST has been delayed several times in recent years. In addition, the final phase consists of some of the most challenging work, where the 6.5-meter telescope and science payload element are being joined with the spacecraft element to complete the observatory.

In addition, the science team also needs to ensure that the observatory can be folded up to fit inside the Ariane 5 rocket that will launch it into space. They also need to ensure that it will unfold again once it reaches space, deploying its sunshield, mirrors and primary mirror. Beyond that, there are also the technical challenges of building a complex observatory that was created here on Earth, but designed to operate in space.

Not only does all of this represent a very technically-challenging feet, it is the first time that any space telescope has had to perform it. Already, the JWST has completed an extensive range of tests to ensure that it will reach its orbit roughly 1.6 million km (1 million mi) from Earth. And while delays can be discouraging, they also increase the likelihood of mission success.

As Thomas Zurbuchen, the associate administrator for NASA’s Science Mission Directorate, stated:

“Considering the investment NASA and our international partners have made, we want to proceed systematically through these last tests, with the additional time necessary, to be ready for a May 2020 launch.”

The combined optics and science instruments of NASA’s James Webb Space Telescope being removed from the Space Telescope Transporter for Air, Road and Sea (STTARS) at the Northrop Grumman company headquarters on March 8th, 2018. Credits: NASA/Chris Gunn

The next step in testing will take several months, and will consist of the spacecraft element undergoing tests to simulate the vibrational, acoustic and thermal environments it will experience during its launch and operations. Once complete, the project engineers will integrate and test the fully assembled observatory and verify that all its components work together properly.

And then (fingers crossed!) this ambitious telescope will finally be ready to take to space and start collecting light. In so doing, scientists from all around the world hope to shed new light on some of the most fundamental questions of science – namely, how did the Universe evolve, is their life in our Solar System beyond Earth, are their habitable worlds beyond our Solar System, and are there other civilizations out there?

Bottom line, NASA remains committed to deploying the James Webb Space Telescope. So even if the answers to these questions are delayed a little, they are still coming!

Further Reading: NASA

Posted on by Matt Williams

NASA’s Curiosity Rover Enjoys its 2000th Day on Mars

This mosaic taken by NASA's Mars Curiosity rover looks uphill at Mount Sharp, which Curiosity has been climbing since 2014. Highlighted in white is an area with clay-bearing rocks that scientists are eager to explore; it could shed additional light on the role of water in creating Mount Sharp. Credit: NASA/JPL-Caltech/MSSS

Since it landed on Mars in 2012, the Curiosity rover has made some rather startling scientific discoveries. These include the discovery of methane and organic molecules, evidence of how it lost its ancient atmosphere, and confirming that Mars once had flowing water and lakes on its surface. In addition, the rover has passed a number of impressive milestones along the way.

In fact, back in January of 2018, the rover had spent a total of 2,000 Earth days on Mars. And as of March 22nd, 2018, NASA’s Mars Curiosity rover had reached its two-thousandth Martian day (Sol) on the Red Planet! To mark the occasion, NASA released a mosaic photo that previews what the rover will be investigating next (hint: it could shed further light on whether or not Mars was habitable in the past).

The image (shown at top and below) was assembled from dozens of images taken by Curiosity‘s Mast Camera (Mastcam) on Sol 1931 (back in January). To the right, looming in the background, is Mount Sharp, the central peak in the Gale Crater (where Curiosity landed back in 2012). Since September of 2014, the rover has been climbing this feature and collecting drill samples to get a better understanding of Mars’ geological history.

Image of the mosaic taken by NASA’s Mars Curiosity rover in January of 2018 (Sol 1931). Click to enlarge. Credit: NASA/JPL-Caltech/MSSS

In the center of the image is the rover’s next destination and scientific target. This area, which scientists have been studying from orbit, is rich in clay minerals, which indicates that water once existed there. In the past, the Curiosity rover found evidence of clay minerals on the floor of the Gale Crater. This confirmed that the crater was a lake bed between 3.3 and 3.8 billion years ago.

Mount Sharp, meanwhile, is believed to have formed from sedimentary material that was deposited over a period of about 2 billion years. By examining patches of clay minerals that extend up the mountain’s side, scientists hope to gain insight into the history of Mars since then. These include how long water may have persisted on its surface and how the planet made the transition to the cold and desiccated place it is today.

The Curiosity science team is eager to analyze rock samples pulled from the clay-bearing rocks seen in the center of the image, and not just because of the results they could provide. Recently, the science team developed a new drilling technique to compensate for the failure of a faulty motor (which allows the drill to extend and retract). When the rover begins to drill again, it will be the first time since December 2016.

All told, the rover has spent a total of about 2055 Earth days (5 years and 230 days), which means Curiosity now ranks third behind the Opportunity (5170 days; 5031 sols) and the Spirit rovers (2269 days; 2208 sols) in terms of total time spent on Mars. Since it arrived on Mars in 2012, Curiosity has also traveled a total distance of 18.7 km (11.6 mi) and studied more than 180 meters (600 feet) vertical feet of rock.

But above all, Curiosity‘s greatest achievement has been the discovery that Mars once had all the necessary conditions and chemical ingredients to support microbial life. Based on their findings, Curiosity‘s international science team has concluded that habitable conditions must have lasted for at least millions of years before Mars’ atmosphere was stripped away.

Finding the evidence of this, and how the transition occurred, will not only advance our understanding of the history of Mars, but of the Solar System itself. It also might provide clues as to how Mars could be made into a warmer, wetter environment again someday!

Further Reading: NASA

Posted on by Matt Williams

Wow, Elon Musk Just Deleted the Facebook Pages for SpaceX and Tesla

And Liftoff for Falcon Heavy. Credit: SpaceX
And Liftoff for Falcon Heavy. Credit: SpaceX

About a week ago, it was revealed that the roughly 50 million Facebook profiles were harvested by Cambridge Analytica. This private data firm, which worked with Donald Trump’s election team and the Brexit campaign, reportedly used this data build a software program that could predict and influence voter choices. Since that time, Facebook stock has taken a serious hit, investigations have been mounted, and CEO Mark Zuckerberg himself has come under fire.

In addition, this revelation has led many Facebook users to reconsider their privacy settings or cancel their accounts. One such person is Elon Musk. In a move that could prove rather harmful for the social media giant, Musk recently responded to the news by deleting the official Facebook pages for Tesla and SpaceX. And in a rather ironic twist, the announcement came via another social media giant – Elon Musk’s twitter account.

It all began after Musk responded to a tweet posted by Brian Acton, the famed programmer and entrepreneur who co-founded WhatsApp and is the founder of Signal (an encrypted communications app). In what was clearly an act of jest, he responded to Acton’s statement (“It is time”) and use of the trending hashtag (#deletefacebook), by inquiring “What’s Facebook?”

Naturally, no one was buying it, given that SpaceX and Facebook – and their respective CEOs) – have a rather colorful history of business relations. These include the failed launch that took place in September of 2016, where a Falcon 9 carrying a Israeli telecommunications satellite (which would have also been used by Facebook) exploded on the launch pad.

In response to the news, Zuckerberg posted a statement on Facebook that placed the blame for the failed launch squarely on Musk’s company:

“As I’m here in Africa, I’m deeply disappointed to hear that SpaceX’s launch failure destroyed our satellite that would have provided connectivity to so many entrepreneurs and everyone else across the continent.”

This old grudge was also raised on Twitter amidst the discussion about Facebook’s data breach, with a user reminding everyone about the incident. Musk brushed this aside, tweeting, “Yeah, my fault for being an idiot. We did give them a free launch to make up for it and I think they had some insurance.”

This led to a challenge being issued to Musk, where users wrote him and urged him to delete his company’s accounts. In what was arguably an attempt to keep the joke going, Musk responded by indicating that he didn’t know these accounts existed. He did, however, also promise to remove the accounts forthwith.

And it appears that Musk was true to his word. While SpaceX and Tesla still have Facebook pages and show up in searches, the official accounts appear to be gone. Musk chose to maintain the company’s official Instagram account though, and used the opportunity to once again stress that he had little use for Facebook:

“Instagram’s probably ok imo, so long as it stays fairly independent. I don’t use FB & never have, so don’t think I’m some kind of martyr or my companies are taking a huge blow. Also, we don’t advertise or pay for endorsements, so … don’t care.”

Well, martyr or not, Musk appears to have put his money where his mouth is. And of course, his twitter feed is still going strong and there is no indication he plans on turning that off anytime soon! And whether this was intended as as slight to Zuckerberg or a sincere expression of indifference, it is likely that Musk’s move could prompt more users to delete their accounts.

But of course, the social media giant will survive. And given Zuckerberg‘s and Musk‘s competing visions to provide global broadband internet access using satellites, its a certainty that the two entrepreneurs are not done with each other!

Further Reading: Futurism, Twitter

Posted on by Bob King

NASA’s Parker Solar Probe Will Touch the Sun — So Can You

Credit: NASA
NASA’s Parker Solar Probe will launch this summer and study both the solar wind and unanswered questions about the Sun’s sizzling corona. Credit: NASA

How would you like to take an all-expenses-paid trip to the Sun? NASA is inviting people around the world to submit their names to be placed on a microchip aboard the Parker Solar Probe mission that will launch this summer. As the spacecraft dips into the blazing hot solar corona your name will go along for the ride. To sign up, submit your name and e-mail. After a confirming e-mail, your digital “seat” will be booked. You can even print off a spiffy ticket. Submissions will be accepted until April 27, so come on down!

Step right up! Head over before April 27 to put a little (intense) sunshine in your life. Click the image to go there. Credit: NASA

The Parker Solar Probe is the size of a small car and named for Prof. Eugene Parker, a 90-year-old American astrophysicist who in 1958 discovered the solar wind. It’s the first time that NASA has named a spacecraft after a living person. The Parker probe will launch between July 31 and August 19 but not immediately head for the Sun. Instead it will make a beeline for Venus for the first of seven flybys. Each gravity assist will slow the craft down and reshape its orbit (see below), so it later can pass extremely close to the Sun. The first flyby is slated for late September.

When heading to faraway places, NASA typically will fly by a planet to increase the spacecraft’s speed by robbing energy from its orbital motion. But a probe can also approach a planet on a different trajectory to slow itself down or reconfigure its orbit.

The spacecraft will swing well within the orbit of Mercury and more than seven times closer than any spacecraft has come to the Sun before. When closest at just 3.9 million miles (6.3 million km), it will pass through the Sun’s outer atmosphere called the corona and be subjected to temperatures around 2,500°F (1,377°C). The primary science goals for the mission are to trace how energy and heat move through the solar corona and to explore what accelerates the solar wind as well as solar energetic particles.

The Parker Solar Probe will use seven Venus flybys over nearly seven years to gradually shrink its orbit around the Sun, coming as close as 3.7 million miles (5.9 million km), well within the orbit of Mercury. Closest approaches (called perihelia) will happen in late December 2024 and the first half of 2025 before the mission ends. Credit: NASA

The vagaries of the solar wind, a steady flow of particles that “blows” from the Sun’s corona at more than million miles an hour, can touch Earth in beautiful ways as when it energizes the aurora borealis. But it can also damage spacecraft electronics and poorly protected power grids on the ground. That’s why scientists want to know more about how the corona works, in particular why it’s so much hotter than the surface of the Sun — temperatures there are several million degrees.

During the probe’s closest approach, the Sun’s apparent diameter will span 14° of sky. Compare that to the ½° Sun we see from Earth. Can you imagine how hot the Sun’s rays would be if it were this large from Earth? Life as we know it would be over. Wikipedia / CC BY-SA 3.0

As you can imagine, it gets really, really hot near the Sun, so you’ve got to take special precautions. To perform its mission, the spacecraft and instruments will be protected from the Sun’s heat by a 4.5-inch-thick carbon-composite shield, which will keep the four instrument suites designed to study magnetic fields, plasma and energetic particles, and take pictures of the solar wind, all at room temperature.

Similar to how the Juno probe makes close passes over Jupiter’s radiation-fraught polar regions and then loops back out to safer ground, the Parker probe will make 24 orbits around the Sun, spending a relatively short amount of face to face time with our star. At closest approach, the spacecraft will be tearing along at about 430,000 mph, fast enough to get from Washington, D.C., to Tokyo in under a minute, and will temporarily become the fastest manmade object. The current speed record is held by Helios-B when it swung around the Sun at 156,600 mph (70 km/sec) on April 17, 1976.

A composite of the August 21, 2017 total solar eclipse showing the Sun’s spectacular corona. Astronomers still are sure why it’s so much hotter than the 10,000°F solar surface (photosphere). Theories include a microflares or magnetic waves that travel up from deep inside the Sun. Credit and copyright: Alan Dyer / amazingsky.com

Many of you saw last August’s total solar eclipse and marveled at the beauty of the corona, that luminous spider web of light around Moon’s blackened disk. When closest to the Sun at perihelion the Parker probe will fly to within 9 solar radii (4.5 solar diameters) of its surface. That’s just about where the edge of the furthest visual extent of the corona merged with the blue sky that fine day, and that’s where Parker will be!

Posted on by Matt Williams

That Interstellar Asteroid ‘Oumuamua Probably Came From a Binary Star System

Artist’s impression of the first interstellar asteroid/comet, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) telescope in Hawaii announced the first-ever detection of an interstellar asteroid – I/2017 U1 (aka. ‘Oumuamua). Since that time, no effort has been spared to study this object before it leaves our Solar System. These include listening to it for signs of communications, determining its true nature and shape, and determining where it came from.

In fact, the question of this interstellar object’s origins has been mystery since it was first discovered. While astronomers are sure that it came from the direction of Vega and some details have been learned about its past, where it originated from remains unknown. But according to a new study by a team of astronomers from the University of Toronto, Scarborough, ‘Oumuamua may have originally come from a binary star system.

The study, titled “Ejection of rocky and icy material from binary star systems: Implications for the origin and composition of 1I/‘Oumuamua “, recently appeared in the Monthly Notices of the Royal Astronomical Society. The study was led by Alan P. Jackson, a research fellow at the Center for Planetary Sciences (CPS) at the University of Scarborough, and included members from both the CPS and the Canadian Institute for Theoretical Astrophysics (CITA).

Oumuamua as it appeared using the William Herschel Telescope on the night of October 29. Credit: Queen’s University Belfast/William Herschel Telescope

For the sake of their study, Jackson and his co-authors considered how in single star systems (like our own), asteroids do not get ejected very often. For the most part, it is comets that become interstellar objects, mainly because they orbit the Sun at a greater distance and are less tightly bound by its gravity. And while ‘Oumuamua was initially mistaken for a comet, follow-up observations by the European Southern Observatory (ESO) indicated that it is  likely an asteroid.

With the help of other astronomers, it soon became apparent that ‘Oumuamua was likely an oddly-shaped rocky object that measured about 400 meters (1312 ft) long and was tube-shaped. These findings were rather surprising to astronomers. As Jackson explained in a recent Royal Astronomical Society press release:

“It’s really odd that the first object we would see from outside our system would be an asteroid, because a comet would be a lot easier to spot and the Solar System ejects many more comets than asteroids.”

As such, Jackson and his team hypothesized that interstellar objects like ‘Oumuamau are more likely to be ejected from a binary system. To test this theory, they constructed a population synthesis model that considered just how common binary star systems are in the Galaxy. They also conducted 2000 N-body simulations to see just how efficient such systems would be at ejecting objects like ‘Oumuamua.

Diagram showing the orbit of the interstellar asteroid ‘Oumuamua as it passes through the Solar System. Credit: ESO/K. Meech et al.

What they found was that binary stars are produced at a rate of about 30% by number and 41% by mass, and that rocky objects like ‘Oumuamua are far more likely to be ejected from binary than single star systems. Based on ‘Oumuamua’s rocky composition, they also determined that the asteroid was likely ejected from the inner part of its solar system (i.e. inside the “Ice Line”) while the system was still in the process of formation.

Lastly, they determined that rocky objects are ejected from binary systems in comparable numbers to icy objects. This is based on the fact that the presence of a companion star would mean that more material would become unstable due to stellar encounters. In the end, this material would be more likely to be ejected rather than accreted to form planets, or take up residence in the outer reaches of the star system.

While there are still many unanswered questions about ‘Oumuamua, it remains the first interstellar asteroid that scientists have ever known. As such, its continued study can tell us a great deal about what lies beyond our Solar System. As Jackson put it:

“The same way we use comets to better understand planet formation in our own Solar System, maybe this curious object can tell us more about how planets form in other systems.”

The team’s findings were also the subject of a presentation that took place at the 49th Lunar and Planetary Science Conference, which took place this week at The Woodlands, Texas.

Further Reading: Royal Astronomical Society, MNRAS

Posted on by Evan Gough

70,000 Years Ago a Nearby Star Messed With the Orbits Of Comets and Asteroids in our Solar System

70,000 years ago, Scholz's star, a red dwarf, came as close as 1 light-year to our Solar System. It could have perturbed the Oort Cloud. At that time, Neanderthals were still around. Image: Credit: José A. Peñas/SINC
70,000 years ago, Scholz's star, a red dwarf, came as close as 1 light year to our Solar System. At that time, neanderthals were still around. Image: Credit: José A. Peñas/SINC

70,000 years ago, our keen-eyed ancestors may have noticed something in the sky: a red dwarf star that came as close as 1 light year to our Sun. They would’ve missed the red dwarf’s small, dim companion—a brown dwarf—and in any case they would’ve quickly returned to their hunting and gathering. But that star’s visit to our Solar System had an impact astronomers can still see today.

The star in question is called Scholz’s star, after astronomer Ralf-Dieter Scholz, the man who discovered it in 2013. A new study published in the Monthly Notices of the Royal Astronomical Society by astronomers at the Complutense University of Madrid, and at the University of Cambridge, shows the impact Scholz’s star had. Though the star is now almost 20 light years away, its close approach to our Sun changed the orbits of some comets and asteroids in our Solar System.

When it came to our Solar System 70,000 years ago, Scholz’s star entered the Oort Cloud. The Oort Cloud is a reservoir of mostly-icy objects that spans the range from about 0.8 to 3.2 light years from the Sun. Its visit to the Oort Cloud was first explained in a paper in 2015. This new paper follows up on that work, and shows what impact the visit had.

“Using numerical simulations, we have calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come.” – Carlos de la Fuente Marcos, Complutense University of Madrid.

In this new paper, the astronomers studied almost 340 objects in our Solar System with hyperbolic orbits, which are V-shaped rather than elliptical. Their conclusion is that a significant number of these objects had their trajectories shaped by the visit from Scholz’s star. “Using numerical simulations, we have calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come,” explains Carlos de la Fuente Marcos, a co-author of the study now published in Monthly Notices of the Royal Astronomical Society. They found that there’s a cluster of these objects in the direction of the Gemini Constellation.

A comparison of the Solar System and its Oort Cloud. 70,000 years ago, Scholz’s Star and companion passed along the outer boundaries of our Solar System (Credit: NASA, Michael Osadciw/University of Rochester)

“In principle,” he adds, “one would expect those positions to be evenly distributed in the sky, particularly if these objects come from the Oort cloud. However, what we find is very different—a statistically significant accumulation of radiants. The pronounced over-density appears projected in the direction of the constellation of Gemini, which fits the close encounter with Scholz’s star.”

There are four ways that objects like those in the study can gain hyperbolic orbits. They might be interstellar, like the asteroid Oumuamua, meaning they gained those orbits from some cause outside our Solar System. Or, they could be natives of our Solar System, originally bound to an elliptical orbit, but cast into a hyperbolic orbit by a close encounter with one of the planets, or the Sun. For objects originally from the Oort Cloud, they could start on a hyperbolic orbit because of interactions with the galactic disc. Finally, again for objects from the Oort Cloud, they could be cast into a hyperbolic orbit by interactions with a passing star. In this study, the passing star is Scholz’s star.

In this image the blue is a hyperbolic orbit while the green is a parabolic orbit. Image: By ScottAlanHill [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
The timing of Scholz’s star’s visit to the Oort Cloud and our Solar System strongly coincides with the data in this study. It’s very unlikely to be coincidental. “It could be a coincidence, but it is unlikely that both location and time are compatible,” says De la Fuente Marcos. In fact, De la Fuente Marcos points out that their simulations suggest that Scholz’s star approached even closer than the 0.6 light-years pointed out in the 2015 study.

The one potentially weak area of this study is pointed out by the authors themselves. As they say in their summary, “…due to their unique nature, the orbital solutions of hyperbolic minor bodies are based on relatively brief arcs of observation and this fact has an impact on their reliability. Out of 339 objects in the sample, 232 have reported uncertainties and 212 have eccentricity with statistical significance.” Translated, it means that some of the computed orbits of individual objects may have errors. But the team expects the overall conclusions of their study to be correct.

The study of minor objects with hyperbolic orbits has heated up since the interstellar asteroid Oumuamua made its visit. This new study successfully connects one population of hyperbolic objects with a pre-historic visit to our Solar System by another star. The team behind the study expects that follow up studies will confirm their results.

Posted on by Matt Williams

Researchers Create the Most Detailed Simulation of the Universe Ever Made

Composite which combines gas temperature (as the color) and shock mach number (as the brightness). Red indicates 10 million Kelvin gas at the centers of massive galaxy clusters, while bright structures show diffuse gas from the intergalactic medium shock heating at the boundary between cosmic voids and filaments. Credit: Illustris Team

Since time immemorial, philosophers and scholars have sought to determine how existence began. With the birth of modern astronomy, this tradition has continued and given rise to the field known as cosmology. And with the help of supercomputing, scientists are able to conduct simulations that show how the first stars and galaxies formed in our Universe and evolved over the course of billions of years.

Until recently, the most extensive and complete study was the “Illustrus” simulation, which looked at the process of galaxy formation over the course of the past 13 billion years. Seeking to break their own record, the same team recently began conducting a simulation known as “Illustris, The Next Generation,” or “IllustrisTNG”. The first round of these findings were recently released, and several more are expected to follow.

These findings appeared in three articles recently published in the Monthly Notices of the Royal Astronomical Society. The Illustris team consists of researchers from the Heidelberg Institute for Theoretical Studies, the Max-Planck Institutes for Astrophysics and for Astronomy, the Massachusetts Institute of Technology, Harvard University, and the Center for Computational Astrophysics in New York.

This illustration shows the evolution of the Universe, from the Big Bang on the left, to modern times on the right. Image: NASA

Using the Hazel Hen supercomputer at the High-Performance Computing Center Stuttgart (HLRS) – one of the three world-class German supercomputing facilities that comprise the Gauss Centre for Supercomputing (GCS) – the team conducted a simulation that will help to verify and expand on existing experimental knowledge about the earliest stages of the Universe – i.e. what happened from 300,000 years after the Big Bang to the present day.

To create this simulation, the team combined equations (such as the Theory of General Relativity) and data from modern observations into a massive computational cube that represented a large cross-section of the Universe. For some processes, such as star formation and the growth of black holes, the researchers were forced to rely on assumptions based on observations. They then employed numerical models to set this simulated Universe in motion.

Compared to their previous simulation, IllustrisTNG consisted of 3 different universes at three different resolutions – the largest of which measured 1 billion light years (300 megaparsecs) across. In addition, the research team included more precise accounting for magnetic fields, thus improving accuracy. In total, the simulation used 24,000 cores on the Hazel Hen supercomputer for a total of 35 million core hours.

As Prof. Dr. Volker Springel, professor and researcher at the Heidelberg Institute for Theoretical Studies and principal investigator on the project, explained in a Gauss Center press release:

“Magnetic fields are interesting for a variety of reasons. The magnetic pressure exerted on cosmic gas can occasionally be equal to thermal (temperature) pressure, meaning that if you neglect this, you will miss these effects and ultimately compromise your results.”

Illustris simulation overview poster. Shows the large scale dark matter and gas density fields in projection (top/bottom). Credit: Illustris Project

Another major difference was the inclusion of updated black hole physics based on recent observation campaigns. This includes evidence that demonstrates a correlation between supermassive black holes (SMBHs) and galactic evolution. In essence, SMBHs are known to send out a tremendous amount of energy in the form of radiation and particle jets, which can have an arresting effect on star formation in a galaxy.

While the researchers were certainly aware of this process during the first simulation, they did not factor in how it can arrest star formation completely. By including updated data on both magnetic fields and black hole physics in the simulation, the team saw a greater correlation between the data and observations. They are therefore more confident with the results and believe it represents the most accurate simulation to date.

But as Dr. Dylan Nelson – a physicist with the Max Planck Institute of Astronomy and an llustricTNG member – explained, future simulations are likely to be even more accurate, assuming advances in supercomputers continue:

“Increased memory and processing resources in next-generation systems will allow us to simulate large volumes of the universe with higher resolution. Large volumes are important for cosmology, understanding the large-scale structure of the universe, and making firm predictions for the next generation of large observational projects. High resolution is important for improving our physical models of the processes going on inside of individual galaxies in our simulation.”

Gas density (left) and magnetic field strength (right) centered on the most massive galaxy cluster. Credit: Illustris Team

This latest simulation was also made possible thanks to extensive support provided by the GCS staff, who assisted the research team with matters related to their coding. It was also the result of a massive collaborative effort that brought together researchers from around the world and paired them with the resources they needed. Last, but not least, it shows how increased collaboration between applied research and theoretical research lead to better results.

Looking ahead, the team hopes that the results of this latest simulation proves to be even more useful than the last. The original Illustris data release gained over 2,000 registered users and resulted in the publication of 130 scientific studies. Given that this one is more accurate and up-to-date, the team expects that it will find more users and result in even more groundbreaking research.

Who knows? Perhaps someday, we may create a simulation that captures the formation and evolution of our Universe with complete accuracy. In the meantime, be sure to enjoy this video of the first Illustris Simulation, courtesy of team member and MIT physicist Mark Vogelsberger:

Further Reading: GCS, Illustrus

Posted on by Matt Williams

TRAPPIST-1 Planets Might Actually Have Too Much Water to be Habitable

Artist's impression of rocky exoplanets orbiting Gliese 832, a red dwarf star just 16 light-years from Earth. Credit: ESO/M. Kornmesser/N. Risinger (skysurvey.org).

In February of 2017, the world was astounded to learn that astronomers – using data from the TRAPPIST telescope in Chile and the Spitzer Space Telescope – had identified a system of seven rocky exoplanets in the TRAPPIST-1 system. As if this wasn’t encouraging enough for exoplanet-enthusiasts, it was also indicated that three of the seven planets orbited within the stars’ circumstellar habitable zone (aka. “Goldilocks Zone”).

Since that time, this system has been the focus of considerable research and follow-up surveys to determine whether or not any of its planets could be habitable. Intrinsic to these studies has been the question whether or not the planets have liquid water on their surfaces. But according to a new study by a team of American astronomers, the TRAPPIST planets may actually have too much water to support life.

Continue reading “TRAPPIST-1 Planets Might Actually Have Too Much Water to be Habitable”

Posted on by Matt Williams

Astronomers Figure Out How to use Gravitational Lensing to Measure the Mass of White Dwarfs

The technique of gravitational lensing relies on the presence of a large cluster of matter between the observer and the object to magnify light coming from that object. Credit: NASA

For the sake of studying the most distant objects in the Universe, astronomers often rely on a technique known as Gravitational Lensing. Based on the principles of Einstein’s Theory of General Relativity, this technique involves relying on a large distribution of matter (such as a galaxy cluster or star) to magnify the light coming from a distant object, thereby making it appear brighter and larger.

However, in recent years, astronomers have found other uses for this technique as well. For instance, a team of scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) recently determined that Gravitational Lensing could also be used to determine the mass of white dwarf stars. This discovery could lead to a new era in astronomy where the mass of fainter objects can be determined.

The study which details their findings, titled “Predicting gravitational lensing by stellar remnants” appeared in the Monthly Noticed of the Royal Astronomical Society. The study was led by Alexander J. Harding of the CfA and included Rosanne Di Stefano, and Claire Baker (also from the CfA), as well as members from the University of Southampton, Georgia State University, the University of Nigeria, and Cornell University.

A Hubble image of the white dwarf star PM I12506+4110E (the bright object, seen in black in this negative print) and its field which includes two distant stars PM12-MLC1&2. Credit: Harding et al./NASA/HST

To put it simply, determining the mass of an astronomical object is one the greatest challenges for astronomers. Until now, the most successful method relied on binary systems because the orbital parameters of these systems depend on the masses of the two objects. Unfortunately, objects that are at the end states of stellar evolution – like black holes, neutron stars or white dwarfs – are often too faint or isolated to be detectable.

This is unfortunate, since these objects are responsible for a lot of dramatic astronomical events. These include the accretion of material, the emission of energetic radiation, gravitational waves, gamma-ray bursts, or supernovae. Many of these events are still a mystery to astronomers or the study of them is still in its infancy – i.e. gravitational waves. As they state in their study:

“Gravitational lensing provides an alternative approach to mass measurement. It has the advantage of only relying on the light from a background source, and can therefore be employed even for dark lenses. In fact, since light from the lens can interfere with the detection of lensing effects, compact objects are ideal lenses.”

As they go on to state, of the 18,000 lensing events that have been detected to date, roughly 10 to 15% are believed to have been caused by compact objects. However, scientists are unable to tell which of the detected events were due to compact lenses. For the sake of their study then, the team sought to circumvent this problem by identifying local compact objects and predicting when they might produce a lensing event so they could be studied.

Animation showing the white dwarf star Stein 2051B as it passes in front of a distant background star. Credit: NASA

“By focusing on pre-selected compact objects in the near vicinity of the Sun, we ensure that the lensing event will be caused by a white dwarf, neutron star, or black hole,” they state. “Furthermore, the distance and proper motion of the lens can be accurately measured prior to the event, or else afterwards. Armed with this information, the lensing light curve allows one to accurately measure the mass of the lens.”

In the end, the team determined that lensing events could be predicted from thousands of local objects. These include 250 neutron stars, 5 black holes, and roughly 35,000 white dwarfs. Neutron stars and black holes present a challenge since the known populations are too small and their proper motions and/or distances are not generally known.

But in the case of white dwarfs, the authors anticipate that they will provide for many lensing opportunities in the future. Based on the general motions of the white dwarfs across the sky, they obtained a statistical estimate that about 30-50 lensing events will take place per decade that could be spotted by the Hubble Space Telescope, the ESA’s Gaia mission, or NASA’s James Webb Space Telescope (JWST). As they state in their conclusions:

“We find that the detection of lensing events due to white dwarfs can certainly be observed during the next decade by both Gaia and HST. Photometric events will occur, but to detect them will require observations of the positions of hundreds to thousands of far-flung white dwarfs. As we learn the positions, distances to, and proper motions of larger numbers of white dwarfs through the completion of surveys such as Gaia and through ongoing and new wide-field surveys, the situation will continue to improve.”

The future of astronomy does indeed seem bright. Between improvements in technology, methodology, and the deployment of next-generation space and ground-based telescopes, there is no shortage of opportunities to see and learn more.

Further Reading: CfA, MNRAS