Posted on by Matt Williams

Astronomers Measure the Mass of a White Dwarf, and Prove Einstein was Right… Again

Hubble image showing the white dwarf star Stein 2051B and the smaller star below it appear to be close neighbors. Credit: NASA/ESA/K. Sahu (STScI)

It’s been over a century since Einstein firs proposed his Theory of General Relativity, his groundbreaking proposal for how gravity worked on large scales throughout the cosmos. And yet, after all that time, experiments are still being conducted that show that Einstein’s field equations were right on the money. And in some cases, old experiments are finding new uses, helping astronomers to unlock other astronomical mysteries.

Case in point: using the Hubble Space Telescope, NASA astronomers have repeated a century-old test of General Relativity to determine the mass of a white dwarf star. In the past, this test was used to determine how it deflects light from a background star. In this case, it was used to provide new insights into theories about the structure and composition of the burned-out remnants of a star.

White dwarfs are what become of a star after it has exited the Main Sequence of its lifespan after exhausting their nuclear fuel. This is followed by the star expelling most of its outer material, usually through a massive explosion (aka. a supernova). What is left behind is a small and extreme dense (second only to a neutron star) which exerts an incredible gravitational force.

Illustration revealing how the gravity of a white dwarf star warps space and bends the light of a distant star behind it. Credits: NASA, ESA, and A. Feild (STScI)

This attribute is what makes white dwarfs a good means for testing General Relativity. By measuring how much they deflect the light from a background star, astronomers are able to see the effect gravity has on the curvature of spacetime. This is precisely similar to what British astronomer Sir Arthur Eddington did in 1919, when he led an expedition to determine how much the Sun’s gravity deflected the light of a background star during a solar eclipse.

Known as gravitational microlensing, this same experiment was repeated by the NASA team. Using the Hubble Space Telescope, they observed Stein 2051B – a white dwarf located just 17 light-years from Earth – on seven different occasions during a two-year period. During this period, it passed in front of a background star located about 5000 light-years distant, which produced a visible deviation in the path of the star’s light.

The resulting deviation was incredibly small – only 2 milliarseconds from its actual position – and was only discernible thanks to the optical resolution of Hubble’s Wide Field Camera 3 (WFC3). Such a deviation would have been impossible to detect using instruments that predate Hubble. And more importantly, the results were consistent with what Einstein predicted a century ago.

As Kailash Sahu, an astronomer at the Space Telescope Science Institute (STScI) and the lead researcher on the project, explained in a NASA press release, this method is also an effective way to test a star’s mass. “This microlensing method is a very independent and direct way to determine the mass of a star,” he said. “It’s like placing the star on a scale: the deflection is analogous to the movement of the needle on the scale.”

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

The deflection measurement yielded highly-accurate results concerning the mass of the white dwarf star – roughly 68 percent of the Sun’s mass (aka. 0.68 Solar masses) – which was also consistent with theoretical predictions. This is highly significant, in that it opens the door to a new and interesting method for determining the mass of distant stars that do not have companions.

In the past, astronomers have typically determined the mass of stars by observing binary pairs and calculating their orbital motions. Much in the same way that radial velocity measurements are used by astronomers to determine if a planet has a system of exoplanets, measuring the influence two stars have on each other is used to determine how much mass each possesses.

This was how astronomers determined the mass of the Sirius star system, which is located about 8.6 light years from Earth. This binary star system consists of a white supergiant (Sirius A) and a white dwarf companion (Sirius B) which orbit each other with a radial velocity of 5.5 km/s. These measurements helped astronomers determine that Sirius A has a mass of about 2.02 Solar masses while Sirius B weighs in at 0.978 Solar masses.

And while Stein 2051B has a companion (a bright red dwarf), astronomers cannot accurately measure its mass because the stars are too far apart – at least 8 billion km (5 billion mi). Hence, this method could be used in the future wherever companion stars are unavailable or too distant. The Hubble observations also helped the team to independently verify the theory that a white dwarf’s radius can be determined by its mass.

Artist’s impression of the binary pair made up by a white dwarf star in orbit around Sirius (a white supergiant). Credit: NASA, ESA and G. Bacon (STScI)

This theory was first proposed by Subrahmanyan Chandrasekhar in 1935, the Indian-American astronomer whose theoretical work on the evolution of stars (and black holes) earned him the Nobel Prize for Physics in 1983. They could also help astronomers to learn more about the internal composition of white dwarfs. But even with an instrument as sophisticated as the WFC3, obtaining these measurements was not without its share of difficulties.

As Jay Anderson, an astronomer with the STScI who led the analysis to precisely measure the positions of stars in the Hubble images, explained:

“Stein 2051B appears 400 times brighter than the distant background star. So measuring the extremely small deflection is like trying to see a firefly move next to a light bulb. The movement of the insect is very small, and the glow of the light bulb makes it difficult to see the insect moving.”

Dr. Sahu presented his team’s findings yesterday (June 7th) at the American Astronomical Society meeting in Austin, Texas. The team’s result will also appear in the journal Science on June 9th. And in the future, the researchers plan to use Hubble to conduct a similar microlensing study on Proxima Centauri, our solar system’s closest stellar neighbor and home to the closest exoplanet to Earth (Proxima b).

It is important to note that this is by no means the only modern experiment that has validated Einstein’s theories. In recent years, General Relativity has been confirmed through observations of rapidly spinning pulsars, 3D simulations of cosmic evolution, and (most importantly) the discovery of gravitational waves. Even in death, Einstein is still making valued contributions to astrophysics!

Further Reading: NASA

Posted on by Evan Gough

At the Largest Scales, Our Milky Way Galaxy is in the Middle of Nowhere

The Millenium Simulation created this image of the large-scale structure of the Universe, showing filaments and voids within the cosmic structure. According to a new study from the University of Wisconsin, our Milky Way is situated in a huge void in the cosmic structure. The Millennium Simulation is a project of the Max Planck Supercomputing Center in Germany. Image: Millennium Simulation Project
Image of the large-scale structure of the Universe, showing filaments and voids within the cosmic structure. Credit: Millennium Simulation Project

Ever since Galileo pointed his telescope at Jupiter and saw moons in orbit around that planet, we began to realize we don’t occupy a central, important place in the Universe. In 2013, a study showed that we may be further out in the boondocks than we imagined. Now, a new study confirms it: we live in a void in the filamental structure of the Universe, a void that is bigger than we thought.

In 2013, a study by University of Wisconsin–Madison astronomer Amy Barger and her student Ryan Keenan showed that our Milky Way galaxy is situated in a large void in the cosmic structure. The void contains far fewer galaxies, stars, and planets than we thought. Now, a new study from University of Wisconsin student Ben Hoscheit confirms it, and at the same time eases some of the tension between different measurements of the Hubble Constant.

The void has a name; it’s called the KBC void for Keenan, Barger and the University of Hawaii’s Lennox Cowie. With a radius of about 1 billion light years, the KBC void is seven times larger than the average void, and it is the largest void we know of.

The large-scale structure of the Universe consists of filaments and clusters of normal matter separated by voids, where there is very little matter. It’s been described as “Swiss cheese-like.” The filaments themselves are made up of galaxy clusters and super-clusters, which are themselves made up of stars, gas, dust and planets. Finding out that we live in a void is interesting on its own, but its the implications it has for Hubble’s Constant that are even more interesting.

Hubble’s Constant is the rate at which objects move away from each other due to the expansion of the Universe. Dr. Brian Cox explains it in this short video.

The problem with Hubble’s Constant, is that you get a different result depending on how you measure it. Obviously, this is a problem. “No matter what technique you use, you should get the same value for the expansion rate of the universe today,” explains Ben Hoscheit, the Wisconsin student who presented his analysis of the KBC void on June 6th at a meeting of the American Astronomical Society. “Fortunately, living in a void helps resolve this tension.”

There are a couple ways of measuring the expansion rate of the Universe, known as Hubble’s Constant. One way is to use what are known as “standard candles.” Supernovae are used as standard candles because their luminosity is so well-understood. By measuring their luminosity, we can determine how far away the galaxy they reside in is.

Another way is by measuring the CMB, the Cosmic Microwave Background. The CMB is the left over energy imprint from the Big Bang, and studying it tells us the state of expansion in the Universe.

This is a map of the observable Universe from the Sloan Digital Sky Survey. Orange areas show higher density of galaxy clusters and filaments. Image: Sloan Digital Sky Survey.
This is a map of the observable Universe from the Sloan Digital Sky Survey. Orange areas show higher density of galaxy clusters and filaments. Image: Sloan Digital Sky Survey.

The two methods can be compared. The standard candle approach measures more local distances, while the CMB approach measures large-scale distances. So how does living in a void help resolve the two?

Measurements from inside a void will be affected by the much larger amount of matter outside the void. The gravitational pull of all that matter will affect the measurements taken with the standard candle method. But that same matter, and its gravitational pull, will have no effect on the CMB method of measurement.

“One always wants to find consistency, or else there is a problem somewhere that needs to be resolved.” – Amy Barger, University of Hawaii, Dept. of Physics and Astronomy

Hoscheit’s new analysis, according to Barger, the author of the 2013 study, shows that Keenan’s first estimations of the KBC void, which is shaped like a sphere with a shell of increasing thickness made up of galaxies, stars and other matter, are not ruled out by other observational constraints.

“It is often really hard to find consistent solutions between many different observations,” says Barger, an observational cosmologist who also holds an affiliate graduate appointment at the University of Hawaii’s Department of Physics and Astronomy. “What Ben has shown is that the density profile that Keenan measured is consistent with cosmological observables. One always wants to find consistency, or else there is a problem somewhere that needs to be resolved.”

Posted on by Matt Williams

We’re One Step Closer to Knowing Why There’s More Matter Than Antimatter in the Universe

Credit: Univeristy of Tokyo

The Standard Model of particle physics has been the predominant means of explaining what the basic building blocks of matter are and how they interact for decades. First proposed in the 1970s, the model claims that for every particle created, there is an anti-particle. As such, an enduring mystery posed by this model is why the Universe can exist if it is theoretically made up of equal parts of matter and antimatter.

This seeming disparity, known as the charge-parity (CP) violation, has been the subject of experiments for many years. But so far, no definitive demonstration has been made for this violation, or how so much matter can exist in the Universe without its counterpart. But thanks to new findings released by the international Tokai-to-Kamioka (T2K) collaboration, we may be one step closer to understanding why this disparity exists.

First observed in 1964, CP violation proposes that under certain conditions, the laws of charge-symmetry and parity-symmetry (aka. CP-symmetry) do not apply. These laws state that the physics governing a particle should be the same if it were interchanged with its antiparticle, while its spatial coordinates would be inverted. From this observation, one of the greatest cosmological mysteries emerged.

If the laws governing matter and antimatter are the same, then why is it that the Universe is so matter-dominated? Alternately, if matter and antimatter are fundamentally different, then how does this accord with our notions of symmetry? Answering these questions is not only important as far as our predominant cosmological theories go, they are also intrinsic to understanding how the weak interactions that govern particles work.

Established in June of 2011, the international T2K collaboration is the first experiment in the world dedicated to answering this mystery by studying neutrino and anti-neutrino oscillations. The experiment begins with high-intensity beams of muon neutrinos (or muon anti-neutrinos) being generated at the Japan Proton Accelerator Research Complex (J-PARC), which are then fired towards the Super-Kamiokande detector 295 km away.

This detector is currently one of the world’s largest and most sophisticated, dedicated to the detection and study of solar and atmospheric neutrinos. As neutrinos travel between the two facilities, they change “flavor” – going from muon neutrinos or anti-neutrinos to electron neutrinos or anti-neutrinos. In monitoring these neutrino and anti-neutrino beams, the experiment watches for different rates of oscillation.

This difference in oscillation would show that there is an imbalance between particles and antiparticles, and thus provide the first definitive evidence of CP violation for the first time. It would also indicate that there are physics beyond the Standard Model that scientists have yet to probe. This past April, the first data set produced by T2K was released, which provided some telling results.

The detected pattern of an electron neutrino candidate event observed by Super-Kamiokande. Credit: Kavli IMPU

As Mark Hartz, a T2K collaborator and the Kavli IPMU Project Assistant Professor, said in a recent press release:

“While the data sets are still too small to make a conclusive statement, we have seen a weak preference for large CP violation and we are excited to continue to collect data and make a more sensitive search for CP violation.”

These results, which were recently published in the Physical Review Letters, include all data runs from between January 2010 to May 2016. In total, this data comprised 7.482 x 1020 protons (in neutrino mode), which yielded 32 electron neutrino and 135 muon neutrino events, and 7.471×1020 protons (in antineutrino mode), which yielded 4 electron anti-neutrino and 66 muon neutrino events.

In other words, the first batch of data has provided some evidence for CP violation, and with a confidence interval of 90%. But this is just the beginning, and the experiment is expected to run for another ten years before wrapping up. “If we are lucky and the CP violation effect is large, we may expect 3 sigma evidence, or about 99.7% confidence level, for CP violation by 2026,” said Hartz.

If the experiment proves successful, physicists may finally be able to answer how it is that the early Universe didn’t annihilate itself. It is also likely help to reveal aspects of the Universe that particle physicists are anxious to get into! For it here that the answers to the deepest secrets of the Universe, like how all of its fundamental forces fit together, are likely to be found.

Further Reading: Kavli IMPU, Physical Review Letters

Posted on by Nancy Atkinson

Amazing Video: Watch SpaceX’s Dragon in Flight, as Seen From the Ground

A screenshot of video by Thierry Legault of the Dragon capsule and associated objects just 20 minutes after launch on June 3, 2017. Credit and copyright: Thierry Legault, used by permission.

Always on the lookout for interesting events in the skies, astrophotographer Thierry Legault has captured an incredible video of SpaceX’s Dragon capsule traveling through space just 20 minutes after it launched from Kennedy Space Center on June 3, 2017.

“You can see the Dragon, the second stage of the Falcon 9 rocket, and solar panel covers,” Legault told Universe Today via email, “plus a nice surprise I discovered during processing: several fast ejections of material, certainly thrusters firing!”

Legault captured at least 6 ejections of material during the passage over his location in Tours, France. The three brightest are highlighted at the end of this video. He used a Sony Alpha 7S with a 200mm lens.

So, what you’re seeing is the Dragon traveling through the background of stars. Legault hand-tracked the Dragon, so even though it appears as stationary (with a few bumps here and there) and objects are zooming past, the capsule is in fact moving at close to 17,500 mph (28,000 km/h). This was taken a just few minutes after the capsule separated from the Falcon nine upper stage and jettisoned the covers on the solar panels, so all the individual bright ‘dots’ seen here were still near each other, moving together in Earth orbit.

This Dragon is now docked at the International Space Station, as the launch was the CRS-11 (11 of 12 planned Commercial Resupply Services for SpaceX.) This was the first time that a Dragon spacecraft was reused, and it brought supplies and science experiments to the ISS. As SpaceX has now done several times, the first stage booster landed back at KSC. This was also the 100th launch from historic pad 39A. Read more about the launch and mission here.

This isn’t the first time Legault has captured the Dragon in flight; he also shot footage of Dragon on its way to the ISS in April of 2014. Recently, he also was able to take multiple images of the ISS passing in front of the Moon:

Lunar transit of the ISS
Expedition 50 with French astronaut Thomas Pesquet on February 4, 2017. Filmed with Celestron C14 EdgeHD and Sony Alpha 7S from Rouen, France (Pesquet’s birth city). Credit and copyright: Thierry Legault. Used by permission.

Thanks to Thierry for sharing his footage and images with Universe Today. Keep track of his amazing work at his website.

Posted on by Matt Williams

Even Calm Red Dwarf Stars Blast Their Planets with Mini-Flares, Destroying their Habitability

Artist's impression of a flaring red dwarf star, orbited by an exoplanet. Credit: NASA, ESA, and G. Bacon (STScI)

Thanks to some rather profound discoveries, red dwarf stars (aka. M-type stars) have been a popular target for exoplanet hunters lately. While small, cool, and relatively dim compared to our Sun, red dwarf star systems are where many of the most recent and promising exoplanet finds have been made. These include Proxima b, the seven rocky planets orbiting TRAPPIST-1, and the super-Earth discovered around LHS 1140b.

Unfortunately, red dwarf stars pose a bit of a problem when it comes to habitability. In addition to being variable in terms of the light they put out, they also known for being unstable. According to a new study by a team of scientists – which was presented the this week at the annual meeting of the American Astronomical Society – red dwarfs also experience mini-flares that could have a cumulative effect, thus rendering their orbiting planets uninhabitable.

For the sake of their study, titled “gPhoton: The GALEX Photon Data Archive“, the team relied on the ten years of ultraviolet observations made by the Galaxy Evolution Explorer (GALEX) spacecraft. During its mission, which ran from 2003 to 2013, GALEX monitored stars to detect rapid increases in brightness – i.e. signs of solar flare activity. These flares emit radiation across many wavelengths, but a significant amount is released in the UV band.

Artist’s impression of the GALEX mission, which monitors ultraviolet throughout the Universe. Credit: NASA/JPL-Caltech

Though not originally intended for exoplanet hunting, GALEX’s data proved very useful since red dwarfs are usually relatively dim in the ultraviolet band (a trait which makes flares particularly noticeable). Using this data, the team was able to measure events that were less intense than many previously detected flares. This was important, since red dwarf flares are known to be greater in frequency, but weaker in intensity.

It was also important from a habitability standpoint, since it is possible that frequent flaring could add up over time to create an inhospitable environment on orbiting planets. If planets like Proxima b are subject to radiation from smaller (but more frequent) flares, could there be a cumulative effect that could ultimately prevent life from emerging over time?

Such is the question that the team sought to address. To do this, they sorted through the ten years of GALEX data, which is held at the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute (STScI). Led by Chase Million of Million Concepts at State College in Pennsylvania, their efforts led to the creation of gPhoton – a 130 terabyte database with millisecond-timing resolution.

This database was then examined with custom software developed by Million and Clara Brasseur of the STScI, which enabled them to analyze the UV data at the photon level. As Million indicated, the results were quite interesting. “We have found dwarf star flares in the whole range that we expected GALEX to be sensitive to,” he said, “from itty bitty baby flares that last a few seconds, to monster flares that make a star hundreds of times brighter for a few minutes.”

While many of the flares that GALEX noticed were similar in strength to those generated by our Sun, the dynamics of red dwarf star systems are quite different. Since they are cooler and less bright, rocky planets need to orbit closer to red dwarfs in order to be warm enough to maintain liquid water on their surfaces (i.e. be habitable). This proximity means that they would be subject to more of the energy produced by these flares.

Such flares would be capable of stripping away a planet’s atmosphere, and could also prevent life from arising on the surface. And over time, smaller flares could poison an environment, making it impossible for organic life to thrive. At present, team members Brasseur and Rachel Osten (also from the STScI) are examining other stars observed by GALEX and also Kepler to look for similar flares.

The team expects to find examples of hundreds of thousands of these flares, which could help shed additional light on just what effect they could have on planetary habitability in red dwarf star systems. But for the time being, the case for red dwarf habitability appears to have been weakened. And once again, it has to do with the instability and radiation produced by these cool customers.

In the future, next-generation missions like the James Webb Space Telescope (which is scheduled to launch in 2018) are expected to reveal vital information on the atmospheres of nearby exoplanets. Most of these reside in red dwarf star systems, where questions about their composition and ability to support life are waiting to be resolved. In addition, the mission can also expected to shed light on these planet’s ability to retain atmospheres.

Artist’s impression of the view from the most distant exoplanet discovered around the red dwarf star TRAPPIST-1. Credit: ESO/M. Kornmesser.

On the plus side, this study has shown that archival data from missions that are no longer in operation can still be incredibly useful. As Don Neill, a research scientist at Caltech and a member of the GALEX collaboration, explained:

“These results show the value of a survey mission like GALEX, which was instigated to study the evolution of galaxies across cosmic time and is now having an impact on the study of nearby habitable planets. We did not anticipate that GALEX would be used for exoplanets when the mission was designed.”

These results were presented in a press conference at the American Astronomical Society, which will be taking place from June 4th to June 8th in Austin, Texas.

Further Reading: HubbleSite, The Astrophysical Journal

Posted on by Matt Williams

Cancer Risk for a Human Mars Mission Just Got a Lot Worse

A new study from UNLV indicates that the health risks for astronauts exploring Mars could be twice as bad as previously thought. Credit: NASA/Pat Rawlings, SAIC

Astronauts hoping to take part in a crewed mission to Mars might want to pack some additional rad tablets! Long before NASA announced their proposal for a “Journey to Mars“, which envisions putting boots on the Red Planet by the 2030s, mission planners have been aware that one of the greatest risks for such a mission has to do with the threat posed by cosmic and solar radiation.

But according to a new study from the University of Nevada, Las Vegas, this threat is even worse than previously thought. Using a predictive model, this study indicates that astronauts that are the surface of Mars for extended periods of time could experience cell damage from cosmic rays, and that this damage will extend to other healthy cells – effectively doubling the risk of cancer!

The study, which was led by UNLV scientist Dr. Francis Cucinotta, was published in the May issue of Scientific Reports – under the title of “Non-Targeted Effects Models Predict Significantly Higher Mars Mission Cancer Risk than Targeted Effects Models“. Building on conventional models that predict that DNA damage caused by radiation leads to cancer, their model looked at how such damage could spread throughout the body.

At one time, Mars had a magnetic field similar to Earth, which prevented its atmosphere from being stripped away. Credit: NASA

Galactic cosmic rays (GCRs) are one of the greatest hazards posed by space exploration. These particles, which originate from beyond our Solar System, are basically atomic nuclei that have been stripped of their surrounding electrons, thanks to their high-speed journey through space. In the cases of iron and titanium atoms, these have been known to cause heavy damage to cells because of their very high rates of ionization.

Here on Earth, we are protected from these rays and other sources of radiation thanks to our protective magnetosphere. But with missions that would take astronauts well beyond Earth, they become a much greater threat. And given the long-term nature of a mission to Mars, mitigation procedures and shielding are being investigated quite thoroughly. As Cucinotta explained in a UNLV press statement:

“Exploring Mars will require missions of 900 days or longer and includes more than one year in deep space where exposures to all energies of galactic cosmic ray heavy ions are unavoidable. Current levels of radiation shielding would, at best, modestly decrease the exposure risks.”

Previous studies have indicated that the effects of prolonged exposure to cosmic rays include cancer, central nervous system effects, cataracts, circulatory diseases and acute radiation syndromes. However, until now, the damage these rays cause was thought to be confined to those cells that they actually traverse – which was based on models that deal with the targeted effects of radiation. 

Artist’s impression of astronauts exploring the surface of Mars. Credit: NASA/JSC/Pat Rawlings, SAIC

For the sake of their study, Dr. Cucinotta and Dr. Eliedonna Cacao (a Chemical Engineer at UNLV) consulted the mouse Harderian gland tumor experiment. This is the only extensive data-set to date that deals with the non-targeted effects (NTEs) of radiation for a variety of particles. Using this model, they tracked the effects of chronic exposure to GCRs, and determined that the risks would be twice as high as those predicted by targeted effects models.

“Galactic cosmic ray exposure can devastate a cell’s nucleus and cause mutations that can result in cancers,” Cucinotta explained. “We learned the damaged cells send signals to the surrounding, unaffected cells and likely modify the tissues’ microenvironments. Those signals seem to inspire the healthy cells to mutate, thereby causing additional tumors or cancers.”

Naturally, any indication that there could be an elevated risk calls for additional research. As Cucinotta and Cacao indicated in their study, “The scarcity of data with animal models for tissues that dominate human radiation cancer risk, including lung, colon, breast, liver, and stomach, suggest that studies of NTEs in other tissues are urgently needed prior to long-term space missions outside the protection of the Earth’s geomagnetic sphere.”

These studies will of course need to happen before any long-term space missions are mounted beyond Earth’s magnetosphere. In addition, the findings also raise undeniable ethical issues, such as whether or not these risks could (or should) be waived by space agencies and astronauts. If in fact we cannot mitigate or protect against the hazards associated with long-term missions, is it even right to ask or allow astronauts to take part in them?

In the meantime, NASA may want to have another look at the mission components for the Journey to Mars, and maybe contemplate adding an additional layer or two of lead shielding. Better to be prepared for the worst, right?

Further Reading: UNLV, Nature

Posted on by David Dickinson

Summer Astronomy, Minimoon & Saturn Opposition 2017

Saturn from June 1st. Image credit and copyright: Peter on the Universe Today Flickr forum.
Saturn on June 1st, nearing opposition. Image credit and copyright: Peter on the Universe Today Flickr forum

Summertime astronomy leaves observers with the perennial question: when to observe? Here in Florida, for example, true astronomical darkness does not occur until 10 PM; folks further north face an even more dire situation. In Alaska, the game in late July became “on what date can you first spot a bright planet/star? around midnight.

And evening summer thunder showers don’t help. Our solution is to get up early (4 AM or so) when the roiling atmosphere has settled down a bit.

But there’s one reason to stay up late, as the planet Saturn reaches opposition next week on June 15th and crosses into the evening sky.

Southern hemisphere observers have it best this year, as the ringed planet loiters in southern declinations for the next few years. In fact, Saturn won’t pop up over the celestial equator again until April, 2026. You’ll still be able to see Saturn from mid-northern latitudes, looking low to the south.

First, a brief rundown of the planets this summer. Mars is currently on the far side of the Sun and headed towards solar conjunction of July 26th. Meanwhile, Mercury is headed towards greatest eastern (dusk) elongation on June 21st. Early AM viewers, can follow Venus, which has just passed greatest elongation west of the Sun on June 3rd, just last week. Finally, Jupiter joins Saturn in the dusk sky, high to the south at sunset and headed towards quadrature 90 degrees east of the Sun on July 6th.

Looking eastward on the evening of June 9th. Credit: Stellarium.

There’s another astronomical curiosity afoot this coming weekend: the MiniMoon for 2017. This is the Full Moon nearest to lunar apogee, a sort of antithesis of the over-hyped “SuperMoon.” Lunar apogee occurs on Thursday, June 8th and the Full Moon occurs just 14 hours after.

2017 sees Saturn traveling from the dreaded “13th constellation” of zodiac Ophiuchus the Serpent Bearer into Sagittarius. This also means that Saturn is headed towards bottoming out near 23 degrees southern declination next year in late 2018. Saturn truly lives up to its “father time” namesake, marking up its slow 29 year passage once around the zodiac. This struck home to us a few years back when Saturn passed Spica in the constellation Virgo, right back where I first started observing the planet as a teenager three decades before.

The path of Saturn through the last half of 2017. Credit: Starry Night Education Software.

The rings are also at their widest tilt in 2017, making for an extra photogenic view. 27 degrees wide as seen from our Earthly vantage point is as wide as Saturn’s ring system ever gets. Saturn isn’t really “tipping” back and forth as much as it’s orbiting the Sun and dipping one hemisphere towards us, and then another. In 2017, it’s the planet’s northern hemisphere time to shine.

Saturn: the changing view. Image credit and copyright: Andrew Symes (@failedprotostar)

Here’s the last/next cycle rundown:

-Rings wide open: (southern pole of Saturn tipped earthward): 2003

–Rings edge on: 2009

–Rings wide open: (northern pole of Saturn tipped earthward): 2017

-Rings edge on: 2025

-Rings wide open: (southern pole of Saturn tipped earthward): 2032

Even a small 60 mm refractor and a low power eyepiece will reveal the most glorious facet of Saturn: its glorious rings. Galileo first saw this confounding view in 1610, and sketched Saturn as a curious double-handled world. In 1655 Christaan Huygens first correctly deduced that Saturn’s rings are a flat plane, fully disconnected from the planet itself.

Crank up the magnification a bit, and the large Cassini Gap in the rings and the shadow play of the rings and the planet becomes apparent. This gives the view an amazing 3-D effect unparalleled in observational astronomy. The shadow cast by the bulk of the planet disappears behind it during opposition, then slowly starts to reemerge to one side after. Other things to watch for include the retro-reflector Seeliger Effect ( also known as opposition surge) as the planet brightens near opposition. And can you spy the bulk of the planet through the Cassini gap?

The moons of Saturn. Image credit and copyright: John Chumack

Hunting for Saturn’s moons is also a fun challenge. Saturn has more moons visible to a backyard telescope than any other planet. Titan is easiest, as the +8 magnitude moon orbits Saturn once every 16 days. In a small to medium-sized (8-inch) telescope, six moons are readily visible: Enceladus, Mimas, Rhea, Dione, Iapetus and Tethys. Large light bucket scopes 10” and larger might just also tease out the two faint +15th magnitude moons Hyperion and Phoebe.

Saturn
Cassini looks back across Saturn’s rings. NASA/Cassini/JPL-Caltech/Space Science Institute

There’s also something else special about Saturn in 2017 in the world of space flight: the venerable Cassini mission comes to an end this September. Hard to believe, this mission soon won’t be with us. Launched in 1997, Cassini arrived at Saturn in in July 2004, and has since provided us with an amazing decade plus of science. The internet and science writing online has grown up with Cassini, and it’ll be a sad moment to see it go.

All thoughts to ponder, as you check out Saturn at the eyepiece this summer.

Posted on by Fraser Cain

How Do We Know the Universe is Flat? Discovering the Topology of the Universe

Does This Look Flat?
Does This Look Flat?


Whenever we talk about the expanding Universe, everyone wants to know how this is going to end. Sure, they say, the fact that most of the galaxies we can see are speeding away from us in all directions is really interesting. Sure, they say, the Big Bang makes sense, in that everything was closer together billions of years ago.

But how does it end? Does this go on forever? Do galaxies eventually slow down, come to a stop, and then hurtle back together in a Big Crunch? Will we get a non-stop cycle of Big Bangs, forever and ever?

Illustration of the Big Bang Theory
The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com

We’ve done a bunch of articles on many different aspects of this question, and the current conclusion astronomers have reached is that because the Universe is flat, it’s never going to collapse in on itself and start another Big Bang.

But wait, what does it mean to say that the Universe is “flat”? Why is that important, and how do we even know?

Before we can get started talking about the flatness of the Universe, we need to talk about flatness in general. What does it mean to say that something is flat?

If you’re in a square room and walk around the corners, you’ll return to your starting point having made 4 90-degree turns. You can say that your room is flat. This is Euclidian geometry.

Earth, seen from space, above the Pacific Ocean. Credit: NASA

But if you make the same journey on the surface of the Earth. Start at the equator, make a 90-degree turn, walk up to the North Pole, make another 90-degree turn, return to the equator, another 90-degree turn and return to your starting point.

In one situation, you made 4 turns to return to your starting point, in another situation it only took 3. That’s because the topology of the surface you were walking on decided what happens when you take a 90-degree turn.

You can imagine an even more extreme example, where you’re walking around inside a crater, and it takes more than 4 turns to return to your starting point.

Another analogy, of course, is the idea of parallel lines. If you fire off two parallel lines at the North pole, they move away from each other, following the topology of the Earth and then come back together.

Got that? Great.

Omega Centauri. Credits: NASA, ESA and the Hubble SM4 ERO Team

Now, what about the Universe itself? You can imagine that same analogy. Imaging flying out into space on a rocket for billions of light-years, performing 90-degree maneuvers and returning to your starting point.

You can’t do it in 3, or 5, you need 4, which means that the topology of the Universe is flat. Which is totally intuitive, right? I mean, that would be your assumption.

But astronomers were skeptical and needed to know for certain, and so, they set out to test this assumption.

In order to prove the flatness of the Universe, you would need to travel a long way. And astronomers use the largest possible observation they can make. The Cosmic Microwave Background Radiation, the afterglow of the Big Bang, visible in all directions as a red-shifted, fading moment when the Universe became transparent about 380,000 years after the Big Bang.

Cosmic Microwave Background Radiation. Image credit: NASA
Cosmic Microwave Background Radiation. Image credit: NASA

When this radiation was released, the entire Universe was approximately 2,700 C. This was the moment when it was cool enough for photons were finally free to roam across the Universe. The expansion of the Universe stretched these photons out over their 13.8 billion year journey, shifting them down into the microwave spectrum, just 2.7 degrees above absolute zero.

With the most sensitive space-based telescopes they have available, astronomers are able to detect tiny variations in the temperature of this background radiation.

And here’s the part that blows my mind every time I think about it. These tiny temperature variations correspond to the largest scale structures of the observable Universe. A region that was a fraction of a degree warmer become a vast galaxy cluster, hundreds of millions of light-years across.

Having a non-flat universe would cause distortions between what we saw in the CMBR compared to the current universe. Credit: NASA / WMAP Science Team

The Cosmic Microwave Background Radiation just gives and gives, and when it comes to figuring out the topology of the Universe, it has the answer we need. If the Universe was curved in any way, these temperature variations would appear distorted compared to the actual size that we see these structures today.

But they’re not. To best of its ability, ESA’s Planck space telescope, can’t detect any distortion at all. The Universe is flat.

Illustration of the ESA Planck Telescope in Earth orbit (Credit: ESA)

Well, that’s not exactly true. According to the best measurements astronomers have ever been able to make, the curvature of the Universe falls within a range of error bars that indicates it’s flat. Future observations by some super Planck telescope could show a slight curvature, but for now, the best measurements out there say… flat.

We say that the Universe is flat, and this means that parallel lines will always remain parallel. 90-degree turns behave as true 90-degree turns, and everything makes sense.

But what are the implications for the entire Universe? What does this tell us?

Unfortunately, the biggest thing is what it doesn’t tell us. We still don’t know if the Universe is finite or infinite. If we could measure its curvature, we could know that we’re in a finite Universe, and get a sense of what its actual true size is, out beyond the observable Universe we can measure.

The observable – or inferrable universe. This may just be a small component of the whole ball game.

We know that the volume of the Universe is at least 100 times more than we can observe. At least. If the flatness error bars get brought down, the minimum size of the Universe goes up.

And remember, an infinite Universe is still on the table.

Another thing this does, is that it actually causes a problem for the original Big Bang theory, requiring the development of a theory like inflation.

Since the Universe is flat now, it must have been flat in the past, when the Universe was an incredibly dense singularity. And for it to maintain this level of flatness over 13.8 billion years of expansion, in kind of amazing.

In fact, astronomers estimate that the Universe must have been flat to 1 part within 1×10^57 parts.

Which seems like an insane coincidence. The development of inflation, however, solves this, by expanding the Universe an incomprehensible amount moments after the Big Bang. Pre and post inflation Universes can have vastly different levels of curvature.

In the olden days, cosmologists used to say that the flatness of the Universe had implications for its future. If the Universe was curved where you could complete a full journey with less than 4 turns, that meant it was closed and destined to collapse in on itself.

And it was more than 4 turns, it was open and destined to expand forever.

New results from NASA’s Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia confirm that dark energy (represented by purple grid) is a smooth, uniform force that now dominates over the effects of gravity (green grid). Image credit: NASA/JPL-Caltech

Well, that doesn’t really matter any more. In 1998, the astronomers discovered dark energy, which is this mysterious force accelerating the expansion of the Universe. Whether the Universe is open, closed or flat, it’s going to keep on expanding. In fact, that expansion is going to accelerate, forever.

I hope this gives you a little more understanding of what cosmologists mean when they say that the Universe is flat. And how do we know it’s flat? Very precise measurements in the Cosmic Microwave Background Radiation.

Is there anything that all pervasive relic of the early Universe can’t do?

Posted on by Ken Kremer

Reused SpaceX Dragon Supply Ship Arrives Space Station, Cygnus Departs, Falcon 9 Launch & Landing: Photos/Videos

The SpaceX Dragon CRS-11 is seen seconds away from its capture with the Canadarm2 robotic arm on June 5, 2017. Credit: NASA TV
The SpaceX Dragon CRS-11 is seen seconds away from its capture with the Canadarm2 robotic arm on June 5, 2017. Credit: NASA TV

KENNEDY SPACE CENTER, FL – The first ever reused Dragon supply ship successfully arrived at the International Space Station (ISS) two days after a thunderous liftoff from NASA’s Kennedy Space Center atop a SpaceX Falcon 9 rocket on Saturday, June 3. The first stage booster made a magnificent return to the Cape and erect ground landing some 8 minutes after liftoff.

Meanwhile the already berthed Orbital ATK Cygnus OA-7 supply ship departed the station on Sunday, June 4 after ground controllers detached it and maneuvered it into position for departure.

The commercial Dragon cargo freighter carrying nearly 3 tons of science and supplies for the multinational crew on the CRS-11 resupply mission reached the space stations vicinity Monday morning, June 5, after a two day orbital chase starting from the Kennedy Space Center and a flawless series of carefully choreographed thruster firings culminated in rendezvous.

Liftoff of the SpaceX Falcon 9 rocket carrying the unmanned Dragon cargo freighter from seaside Launch Complex 39A at KSC in Florida took place during an instantaneous launch window at 5:07 p.m. EDT Saturday, June 3, following a 48 hour delay due to a stormy weather scrub at the Florida Space Coast on Thursday, June 1.

The stunning Falcon 9 launch and landing events were captured by journalists and tourists gathered from around the globe to witness history in the making with their own eyeballs.

The Falcon 9 blastoff also counts as the 100th flight from KSC’s historic pad 39A which previously launched NASA’s Apollo astronauts on lunar landing missions and space shuttles for 3 decades

Check out the expanding gallery of eyepopping photos and videos from several space journalist colleagues and friends and myself – for views you won’t see elsewhere.

Click back as the gallery grows !

1st Reused SpaceX Dragon cargo craft lifts off from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. June 3, 2017 on CRS-11 mission carrying 3 tons of research equipment, cargo and supplies to the International Space Station. Credit: Ken Kremer/kenkremer.com

By 8:30 a.m. Monday morning ground controllers had maneuvered Dragon to within 250 meters of the station and the imaginary keep out sphere around the orbiting complex.

Engineers carefully assessed the health of the Dragon and its systems to insure its ability to slowly and safely move in closer for capture by the crew.

When Dragon reached a distance of 11 meters, it was grappled by Expedition 52 astronauts Peggy Whitson and Jack Fischer using the 57.7 foot long (17.6 meter long) Canadian-built robotic arm Monday morning at 9:52 a.m. EDT, a few minutes ahead of schedule.

“Capture complete,” radioed Whitson as Dragon was captured at its grapple pin by the grappling snares at the terminus of the Canadarm2 robotic arm.

Dragon’s capture took place as the ISS was orbiting 250 miles over the South Atlantic Ocean as it was nearing the East coast of Argentina.

“Complete complete. Go for capture configuration,” replied Houston Mission control.

The newly arrived SpaceX Dragon CRS-11 resupply ship is installed to the Harmony module on June 5, 2017. The Progress 66 cargo craft is docked to the Pirs docking compartment and the Soyuz MS-04 crew vehicle is docked to the Poisk module. Credit: NASA

“We want to thank the entire team on the ground that made this possible, both in Hawthorne and in Houston. Really around the whole world, from support in Canada for this wonderful robotic arm, Kennedy Space Center’s launch support, to countless organizations which prepared the experiments and cargo,” Fischer radioed in response.

“These people have supplied us with a vast amount of science and supplies, really fuel for the engine of innovation we get to call home, the International Space Station. We have a new generation of vehicles now, led by commercial partners like SpaceX, as they build the infrastructure that will carry us into the future of exploration.”

“It’s also the first second mission to the ISS which was previously here as CRS-4. The last returned visitor was space shuttle Atlantis on the STS-135 mission,” Fischer said.

A little over two hours after it was captured by Expedition 52 Flight Engineers Jack Fischer and Peggy Whitson, ground teams maneuvered the unpiloted SpaceX Dragon cargo craft for attachment to the Earth-facing port of the station’s Harmony module.

“Ground controllers at Mission Control, Houston reported that Dragon was bolted into place at 12:07 p.m. EDT as the station flew 258 statute miles over central Kazakhstan,” NASA reported.

The berthing of Dragon to Harmony was not broadcast live on NASA TV.

1st Reused SpaceX Dragon cargo craft lifts off from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. June 3, 2017 on CRS-11 mission carrying 3 tons of research equipment, cargo and supplies to the International Space Station. Credit: Ken Kremer/kenkremer.com

Dragon CRS-11 marks SpaceX’s eleventh contracted commercial resupply services (CRS) mission to the International Space Station for NASA since 2012.

Check out these exquisite videos from a wide variety of vantage points including remote cameras at the pad and Cape Canaveral media viewing site – including an A/V compilation of sonic booms from the propulsive ground landing.

Video Caption: CRS-11 Launch from KSC Pad 39A with the first re-used Dragon capsule. SpaceX Falcon 9 launch of the CRS-11 mission to take supplies, equipment and experiments to the ISS, followed by the first stage landing at LZ-1 on the Cape Canaveral Air Force Station. Credit: Jeff Seibert

Video Caption: SpaceX Falcon 9/Dragon CRS 11 Launch 3 June 2017. Launch of SpaceX Falcon 9 on June 3, 2017 from pad 39A at the Kennedy Space Center, FL carrying 1st recycled Dragon supply ship bound for the International Space Station on the CRS-11 mission loaded with 3 tons of science and supplies – as seen in this remote video taken at the pad under cloudy afternoon skies. Credit: Ken Kremer/kenkremer.com

Video Caption: Sonic booms from the return of the CRS-11 booster to LZ-1 on June 3, 2017. Triple sonic booms signal the return of the Falcon 9 first stage to LZ-1 after launching the CRS-11 Dragon spacecraft to the ISS. Credit: Jeff Seibert

The gumdrop shaped 20-foot high, 12-foot-diameter Dragon is carrying almost 5,970 pounds of science experiments and research instruments, crew supplies, food water, clothing, hardware, gear and spare parts to the million pound orbiting laboratory complex.

SpaceX Falcon 9 booster deploys quartet of landing legs moments before precision propulsive ground touchdown at Landing Zone 1 on Canaveral Air Force Station barely nine minutes after liftoff from Launch Complex 39A on 3 June 2017 from the Kennedy Space Center in Florida on the Dragon CRS-11 resupply mission to the International Space Station for NASA. Credit: Ken Kremer/Kenkremer.com

The CRS-11 cargo ship will support over 62 of the 250 active research investigations and experiments being conducted by Expedition 52 and 53 crew members.

The flight delivered investigations and facilities that study neutron stars, osteoporosis, solar panels, tools for Earth-observation, and more.

40 new micestonauts are also aboard inside the rodent research habitat for a first of its kind osteoporosis science study – that seeks to stem the loss of bone density afflicting millions of people on Earth and astronauts crews in space by testing an experimental drug called NELL-1. The therapy will also examine whether bone can be regenerated for the first time. No drug exists for bone regeneration.

The unpressurized trunk of the Dragon spacecraft also transported 3 payloads for science and technology experiments and demonstrations.

The truck payloads include the Roll-Out Solar Array (ROSA) solar panels, the Multiple User System for Earth Sensing (MUSES) facility which hosts Earth-viewing instruments and tools for Earth-observation and equipment to study neutron stars with the Neutron Star Interior Composition Explorer (NICER) payload.

NICER is the first ever space mission to study the rapidly spinning neutron stars – the densest objects in the universe. The launch coincidentally comes nearly 50 years after they were discovered by British astrophysicist Jocelyn Bell.

A second objective of NICER involves the first space test attempting to use pulsars as navigation beacons through technology called Station Explorer for X-Ray Timing and Navigation (SEXTANT).

Blastoff of 1st recycled SpaceX Falcon 9 rocket from Launch Complex 39A at the Kennedy Space Center on June 3, 2017 delivering Dragon CRS-11 resupply mission to the International Space Station (ISS) for NASA. Credit: Ken Kremer/kenkremer.com

NASA decided to use the SpaceX weather related launch delay to move up the departure of the “SS John Glenn” Cygnus cargo ship by over a month since it was already fully loaded and had completed its mission to deliver approximately 7,600 pounds of supplies and science experiments to the orbiting laboratory and its Expedition 51 and 52 crew members for Orbital ATK’s seventh NASA-contracted commercial resupply mission called OA-7.

Named after legendary Mercury and shuttle astronaut John Glenn – 1st American to orbit the Earth – the supply ship had spent 44 days at the station.

The “SS John Glenn” will now remain in orbit a week to conduct the third SAFFIRE fire experiment as well as deploy four small Nanoracks satellites before Orbital ATK flight controllers send commands June 11 to deorbit the spacecraft for its destructive reentry into the Earth’s atmosphere over the Pacific Ocean.

The Orbital ATK Cygnus cargo craft, with its prominent Ultra Flex solar arrays, is pictured moments after being released from the International Space Station on June 4, 2017 . Credit: NASA TV

Watch for Ken’s onsite CRS-11 mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

……….

SpaceX Falcon 9 aloft carrying 1st reused Dragon on CRS-11 resupply flight to the International Space Station on June 3, 2017 from Launch Complex 39A at the Kennedy Space Center. Credit: Ken Kremer/kenkremer.com
Blastoff of SpaceX Falcon 9 with reused Dragon CRS-11 cargo craft from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. on June 3, 2017. Credit: Julian Leek
Descent of SpaceX Falcon 9 1st stage towards Landing Zone-1 at Cape Canaveral after Jun 3, 2017 launch from pad 39A at the Kennedy Space Center. Credit: Julian Leek
Recycled SpaceX Dragon CRS-11 cargo craft lifted off from Launch Complex 39A at NASA’s Kennedy Space Center in Florida at 5:07 p.m. June 3, 2017 carrying 3 tons of research equipment, cargo and supplies to Earth orbit and the International Space Station. Credit: Ken Kremer/kenkremer.com
3 June 2017 launch of SpaceX Falcon 9 on CRS-11 mission to the ISS – as seen from Port Orange, FL. Credit: Gerald DaBose
Landing of SpaceX Falcon 9 1st stage following launch of Dragon CRS-11 cargo craft from Launch Complex 39A at NASA’s Kennedy Space Center in Florida on June 3, 2017 to the ISS. Credit: Jean Wright
SpaceX Falcon 9 rocket goes erect to launch position atop Launch Complex 39A at the Kennedy Space Center on 1 Jun 2017 as seen the morning before later afternoon launch from inside from the pad perimeter. Liftoff of the CRS-11 resupply mission to the International Space Station (ISS) slated for 1 June 2017. Credit: Ken Kremer/Kenkremer.com
Up close view of SpaceX Dragon CRS-11 resupply vessel atop Falcon 9 rocket and delivering 3 tons of science and supplies to the International Space Station (ISS) for NASA. Liftoff slated for 1 June 2017. Credit: Ken Kremer/Kenkremer.com
Posted on by Matt Williams

We Finally Know why the Boomerang Nebula is Colder than Space Itself

Scientists may now know why the Boomerang Nebula, the coldest object in the known Universe. Credit: NASA/ESA/The Hubble Heritage Team (STScI/AURA)

The Boomerang Nebula, a proto-planetary nebula that was created by a dying red giant star (located about 5000 light years from Earth), has been a compelling mystery for astronomers since 1995. It was at this time, thanks to a team using the now-decommissioned 15-meter Swedish-ESO Submillimetre Telescope (SESTI) in Chile, that this nebula came to be known as the coldest object in the known Universe.

And now, over 20 years later, we may know why. According to a team of astronomers who used the Atacama Large Millimeter/submillimeter Array (ALMA) – located in the Atacama desert in northern Chile – the answer may involve a small companion star plunging into the red giant. This process could have ejected most of the larger star’s matter, creating an ultra-cold outflow of gas and dust in the process.

The team’s findings appeared in a paper titled “The Coldest Place in the Universe: Probing the Ultra-cold Outflow and Dusty Disk in the Boomerang Nebula“, which appeared recently in the Astrophysical Journal. Led by Raghvendra Sahai, an astronomer at NASA’s Jet Propulsion Laboratory, they argue that the rapid expansion of this gas is what has caused it to become so cold.

Composite image of the Boomerang Nebula, with ALMA observations (orange) showing the e hourglass-shaped outflow on top of an image from the Hubble Space Telescope (blue). Credit: ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble; NRAO/AUI/NSF

Originally discovered in 1980 by a team of astronomers using the Anglo-Australian telescope at the Siding Spring Observatory, the mystery of this nebula became apparent when astronomers noted that it appeared to be absorbing the light of the Cosmic Microwave Background (CMB). This background radiation, which is the energy leftover from the Big Bang, provides the natural background temperature of space – 2.725 K (–270.4 °C; -454.7 °F).

For the Boomerang Nebula to absorb that radiation, it had to be even colder than the CMB. Subsequent observations revealed that this was in fact the case, as the nebula has a temperature of less than half a degree K (-272.5 °C; -458.5 °F). The reason for this, according to the recent study, has to do with the gas cloud that extends from the central star to a distance of 21,000 AU (21 thousands times the distance between Earth and the Sun).

The gas cloud – which is the result of a jet that is being fired by the central star – is expanding at a rate that is about 10 times faster than what a single star could produce on its own. After conducting measurements with ALMA that revealed regions of the outflow that were never before seen (out to a distance of about 120,000 AUs), the team concluded that this is what is driving temperatures to levels lower than that of background radiation

They further argue that this was the result of the central star having collided with a binary companion in the past, and were even able to deduce what the primary was like before this took place. The primary, they claim, was a Red Giant Branch (RGB) or early-RGB star – i.e. a star in the final phase of its life cycle – whose expansion caused its binary companion to be pulled in by its gravity.

ALMA image of the Boomerang Nebula, showing its massive outflowCredit: ALMA (ESO/NAOJ/NRAO), R. Sahai

The companion star would have eventually merged with its core, which caused the outflow of gas to begin. As Raghvendra Sahai explained in a NRAO press release:

“These new data show us that most of the stellar envelope from the massive red giant star has been blasted out into space at speeds far beyond the capabilities of a single, red giant star. The only way to eject so much mass and at such extreme speeds is from the gravitational energy of two interacting stars, which would explain the puzzling properties of the ultra-cold outflow.”

These findings were made possible thanks to the ALMA’s ability to provide precise measurements on the extent, age, mass and kinetic energy of the nebula. Also, in addition to measuring the rate of outflow, they gathered that it has been taking place for around 1050 to 1925 years. The findings also indicate that the Boomerang Nebula’s days as the coldest object in the known Universe may be numbered.

Looking forward, the red giant star in the center is expected to continue the process of becoming a planetary nebula – where stars shed their outer layers to form an expanding shell of gas. In this respect, it is expected to shrink and get hotter, which will warm up the nebula around it and make it brighter.

As Lars-Åke Nyman, an astronomer at the Joint ALMA Observatory in Santiago, Chile, and co-author on the paper,  said:

“We see this remarkable object at a very special, very short-lived period of its life. It’s possible these super cosmic freezers are quite common in the universe, but they can only maintain such extreme temperatures for a relatively short time.”

These findings could also provide new insights into another cosmological mystery, which is how giant stars and their companions behave. When the larger star in these systems exists its main-sequence phase, it may consume its smaller companion and similarly become a “cosmic freezer”. Herein lies the value of objects like the Boomerang Nebula, which challenges conventional ideas about the interactions of binary systems.

It also demonstrates the value of next-generations instruments like ALMA. Given their superior optical capabilities and ability to obtain more high-resolution information, they can show us some never-before-seen things about our Universe, which can only challenge our preconceived notions of what is possible out there.

Further Reading: NRAO