Stellar Evolution Archives

October 31, 2013December 23, 2015 by Elizabeth Howell

What Are The Odds Of Spotting A Milky Way Supernova From Earth?

Artist illustration of supernova. Credit: NASA

An exploding star in our home galaxy might be visible to Earth in the next 50 years, astronomers say in a new calculation of the odds of a nearby supernova.

This explosion would be too faint to prove a hazard to Earthlings, and in fact it may not even be visible with the naked eye in the starry sky. Its heat signature, however, would be seen in the right kind of camera as long as we could swing a telescope there fast enough.

“For [researchers], this study suggests that they have a solid chance of doing something that’s never been done before: detect a supernova fast enough to witness what happens at the very beginning of a star’s demise,” wrote Ohio State University in a press release about the research, which was led by university astronomer researcher Scott Adams.

Fishing Boats Meet the Milky Way on the Isle of Wight (south of England) on May 16, 2013. Credit and copyright: Chad Powell.

The challenge with observing a supernova in our own galaxy is the presence of cosmic dust that can sometimes obscure supernovae and other phenomena from our view. However, infrared light is not as badly affected by this and may be able to see something through the obscurity.

To jump on the supernova as it is happening, the scientists propose having a network in place to send out neutrino alerts when these particles, which would arrive at Earth first after an explosion, are detected on Earth. The key is to figure out the difference between neutrinos from space and neutrinos from other sources, such as nuclear reactors, the sun or even spurious glitches.

A University of Tokyo group led the building of a model of a new kind of neutrino detector, a model that is now operating underground in Japan. Called EGADS (Evaluating Gadolinium’s Action on Detector Systems), the water in the system would be “spiked” with a bit of gadolinium, which would reportedly assist with neutrino detections from outside of Earth.

The supernova that produced the Crab Nebula was detected by naked-eye observers around the world in 1054 A.D. This composite image uses data from NASA’s Great Observatories, Chandra, Hubble, and Spitzer, to show that a superdense neutron star is energizing the expanding Nebula by spewing out magnetic fields and a blizzard of extremely high-energy particles. The Chandra X-ray image is shown in light blue, the Hubble Space Telescope optical images are in green and dark blue, and the Spitzer Space Telescope’s infrared image is in red. The size of the X-ray image is smaller than the others because ultrahigh-energy X-ray emitting electrons radiate away their energy more quickly than the lower-energy electrons emitting optical and infrared light. The neutron star is the bright white dot in the center of the image. — The supernova that produced the Crab Nebula was detected by naked-eye observers around the world in 1054 A.D. This composite image uses data from NASA’s Great Observatories, Chandra, Hubble, and Spitzer, to show that a superdense neutron star is energizing the expanding Nebula by spewing out magnetic fields and a blizzard of extremely high-energy particles.

“When a neutrino from a Milky Way supernova enters the tank, it can collide with the water molecules and release energy, along with some neutrons,” Ohio State added. “Gadolinium has a great affinity for neutrons, and will absorb them and then re-emit energy of its own. The result would be one detection signal followed by another a tiny fraction of a second later—a “heartbeat” signal inside the tank for each detected neutrino.”

But what about a naked-eye supernova? The researchers say the probability of that is just 20% to 50% in the next century, with southern hemisphere residents having a better chance since more of the galaxy is visible there. The last instance of this happening, by the way, was in 1604.

The research paper is available now on prepublishing site Arxiv and will soon be published in the Astrophysical Journal.

Source: Ohio State University

Correction: This article has been changed to remove a reference to Ohio State University in the EGADS collaboration.

October 26, 2013December 23, 2015 by Tammy Plotner

ALMA Warms Up the View of the Coldest Place In the Universe

Where is the coldest place in the Universe? Right now, astronomers consider the “Boomerang Nebula” to have the honors. Located about 5,000 light-years away in the constellation Centaurus, this pre-planetary nebula carries a temperature of about one Kelvin – or a brisk, minus 458 degrees Fahrenheit. That makes it even colder than the natural background temperature of space! What makes it more frigid than the elusive afterglow of the Big Bang? Astronomers are employing the powers of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to tell us more about its chilly properties and unusual shape.

The “Boomerang” is different all the way around. It is not yet a planetary nebula. The fueling light source – the central star – just isn’t hot enough yet to emit the massive amounts of ultra-violet radiation which lights up the structure. Right now it is illuminated by starlight shining off its surrounding dust grains. When it was first observed in optical light by our terrestrial telescopes, the nebula appeared to be shifted to one side and that’s how it got its fanciful name. Subsequent observations with the Hubble Space Telescope revealed an hour-glass structure. Now, enter ALMA. With these new observations, we can see the Hubble images only show part of what’s happening and the dual lobes seen in the older data were probably only a “trick of the light” as presented by optical wavelengths.

“This ultra-cold object is extremely intriguing and we’re learning much more about its true nature with ALMA,” said Raghvendra Sahai, a researcher and principal scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of a paper published in the Astrophysical Journal. “What seemed like a double lobe, or ‘boomerang’ shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space.”

So what is going on out there that makes the Boomerang such a cool customer? It’s the outflow, baby. The central star is expanding at a frenzied pace and it is lowering its own temperature in the process. A prime example of this is an air conditioner. It uses expanding gas to create a colder core and as the breeze blows over it – or in this case, the expanding shell – the environment around it is cooled. Astronomers were able to determine just how cool the gas in the nebula is by noting how it absorbed the constant of the cosmic microwave background radiation: a perfect 2.8 degrees Kelvin (minus 455 degrees Fahrenheit).

“When astronomers looked at this object in 2003 with Hubble, they saw a very classic ‘hourglass’ shape,” commented Sahai. “Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant.”

However, the single-dish millimeter wavelength telescopes didn’t see things the same as Hubble. Rather than a skinny waist, they found a fuller figure – a “nearly spherical outflow of material”. According to the news release, ALMA’s unprecedented resolution permitted researchers to determine why there was such a difference in overall appearance. The dual-lobe structure was evident when they focused on the distribution of carbon monoxide molecules as seen at millimeter wavelengths, but only toward the inside of the nebula. The outside was a different story, though. ALMA revealed a stretched, cold gas cloud that was relatively rounded. What’s more, the researchers also pinpointed a thick corridor of millimeter-sized dust grains enveloping the progenitor star – the reason the outer cloud took on the appearance of a bowtie in visible light! These dust grains shielded a portion of the star’s light, allowing just a glimpse in optical wavelengths coming from opposite ends of the cloud.

“This is important for the understanding of how stars die and become planetary nebulae,” said Sahai. “Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star.”

There’s even more to these new findings. Even though the perimeter of the nebula is beginning to warm up, it’s still just a bit colder than the cosmic microwave background. What could be responsible? Just ask Einstein. He called it the “photoelectric effect”.

Original Story Source: NRAO News Release.

October 15, 2013December 23, 2015 by Elizabeth Howell

Future Supernova Is Surrounded By Hydrogen Clouds

A "super star cluster", Westerlund 1, which is about 16,000 light-years from Earth. It can be found in the southern constellation of Ara. The picture was taken from the European Southern Observatory's VLT Survey Telescope. Credit: ESO/VPHAS+ Survey/N. Wright

The faint green glow you see in that picture is not an early harbringer of Hallowe’en spooks. It’s hydrogen gas clouds found recently nearby W26, a future supernova in the star cluster Westerlund 1.

The European Southern Observatory’s VLT Survey Telescope in Chile spotted the hydrogen in the cluster, which has hundreds of huge stars that are only believed to be a few million years old. (Our solar system, by comparison, is about 4.5 billion years old.)

“Such glowing clouds around massive stars are very rare, and are even rarer around a red supergiant— this is the first ionised nebula discovered around such a star,” the European Southern Observatory stated.

“W26 itself would be too cool to make the gas glow; the astronomers speculate that the source of the ionizing radiation may be either hot blue stars elsewhere in the cluster, or possibly a fainter, but much hotter, companion star to W26.”

Funny enough, the nebula that surrounds the red supergiant is similar to the one surrounding SN1987A, a star that exploded as a fairly bright supernova in 1987. “Studying objects like this new nebula around W26 will help astronomers to understand the mass loss processes around these massive stars, which eventually lead to their explosive demise,” ESO added.

Source: European Southern Observatory

September 16, 2013December 23, 2015 by Tammy Plotner

Endings and Beginnings – Magnetic Jets Shape Stellar Transformation

A jet of energetic particles (shown in magenta) is shaping the environment around the star IRAS 15445-5449. Infrared light from dusty material which the jet has already shaped into a symmetric form is shown in green. The star itself is hidden by dust in its environment. Credit: E. Lagadec/ESO/A. Pérez Sánchez)

The incredible visual appearance of planetary nebulae are some of the most studied and observed of deep space objects. However, these enigmatic clouds of gas have defied explanation as to their shapes and astronomers are seeking answers. Thanks to a new discovery made by an international team of scientists from Sweden, Germany and Austria, we have now observed a jet of high-energy particles in the process of being ejected from an expiring star.

When a sun-like star reaches the end of its life, it begins to shed itself of its outer layers. These layers blossom into space at speeds of a few kilometers per second, forming a variety of shapes and sizes – yet we know little about what causes their ultimate appearance. Now astronomers are taking a close look at a rather normal star that has reached the end of its life and is beginning to form a planetary nebula. Cataloged as IRAS 15445-5449, this stellar study resides 230,000 light years away in the constellation of Triangulum Australe (the Southern Triangle). Through the use of the CSIRO Australia Telescope Compact Array, a compliment of six 22-meter radio telescopes in New South Wales, Australia, researchers have found what may be the answer to this mystery… high-speed magnetic jets.

“In our data we found the clear signature of a narrow and extremely energetic jet of a type which has never been seen before in an old, Sun-like star,” says Andrés Pérez Sánchez, graduate student in astronomy at Bonn University, who led the study.

How does a radio telescope aid researchers in an optical study? In this case the radio waves emitted by the dying star are compatible with the trademark high-energy particles they are expected to produce. These “spouts” of particles travel at nearly the speed of light and coincident jets are also known to emanate from other astronomical objects that range from newborn stars to supermassive black holes.

“What we’re seeing is a powerful jet of particles spiraling through a strong magnetic field,” says Wouter Vlemmings, astronomer at Onsala Space Observatory, Chalmers. “Its brightness indicates that it’s in the process of creating a symmetric nebula around the star.”

Will these high-energy particles contained within the jet eventually craft the planetary nebula into an ethereal beauty? According to the astronomers, the current state of IRAS 15445-5449 is probably a short-lived phenomenon and nothing more than an intense and dramatic phase in its life… One we’re lucky to have observed.

“The radio signal from the jet varies in a way that means that it may only last a few decades. Over the course of just a few hundred years the jet can determine how the nebula will look when it finally gets lit up by the star,” says team member Jessica Chapman, astronomer at CSIRO in Sydney, Australia.

Will our Sun also follow suit? Right now the answer is unclear. There may be more to this radio picture than meets the ear. However, rest assured that this new information is being heard and might well become the target of additional radio studies. Considering the life of a planetary nebula is generally expected to last few tens of thousands of years, this is a unique opportunity for astronomers to observe what might be a transient occurrence.

“The star may have an unseen companion – another star or large planet — that helps create the jet. With the help of other front-line radio telescopes, like ALMA, and future facilities like the Square Kilometre Array (SKA), we’ll be able to find out just which stars create jets like this one, and how they do it,” says Andrés Pérez Sánchez.

Original Story Source: Royal Astronomical Society News Release.

August 28, 2013December 23, 2015 by Elizabeth Howell

Double Vision: Scientists Spot An Elder ‘Twin’ To the Sun

The life-cycle of a Sun-like star from protostar (left side) to red giant (near the right side) to white dwarf (far right). Credit: ESO/M. Kornmesser

If you want a picture of how you’ll look in 30 years, youngsters are told, look at your parents. The same principle is true of astronomy, where scientists compare similar stars in different age groups to see how they progress.

We have a special interest in learning how the Sun will look in a few billion years because, you know, it’s the main source of energy and life on Earth. Newly discovered HIP 102152 could give us some clues. The star is four billion years older than the sun, but so close in composition that researchers consider it almost like a twin.

Telescopes have only been around for a few centuries, making it hard to project what happens during the billions upon billions of years for a star’s lifetime. We have about 400 years of observations on the sun, for example, which is a minute fraction of its 4.6 billion-year-old lifespan so far.

The Sun in H-Alpha, on 01-07-2013, using a Lunt Solar LS60Scope/LS50 Hydrogen Alpha Solar filter. Credit: John Chumack — Today, we take telescopic observations of the Sun for granted, but the technology only became available about 400 years ago. This picture shows the Sun in H-Alpha, on 01-07-2013, using a Lunt Solar LS60Scope/LS50 Hydrogen Alpha Solar filter. Credit: John Chumack

“It is very hard to study the history and future evolution of our star, but we can do this by hunting for rare stars that are almost exactly like our own, but at different stages of their lives,” stated the European Southern Observatory.

ESO’s Very Large Telescope — guided by a team led by the University of Sao Paulo’s Jorge Melendez — examined HIP 102152 with a spectrograph that broke up the light into various colors, revealing properties such as chemical composition. Around the same time, they scrutinized 18 Scorpii, also considered to be a twin but one that is younger than the sun (2.9 billion years old)

So what can we predict about the Sun’s future? One thing puzzling scientists has been the amount of lithium in our closest stellar companion. Although the Big Bang (the beginning of the universe) created hydrogen, helium and lithium, only the first two elements are abundant in the Sun.

HIP 102152, it turns out, also has low levels of lithium. Why isn’t clear yet, ESO notes, although “several processes have been proposed to transport lithium from the surface of a star into its deeper layers, where it is then destroyed.” Previous observations of young Sun-like stars also show higher levels of lithium, implying something changes between youth and middle age.

The elder twin to our Sun may host another discovery: there could be Earth-sized planets circling the star. Chemical properties of HIP 102152 show that it has few elements that you see in meteorites and rocky planets, implying the elements are “locked up” in bodies close to the star. “This is a strong hint that HIP 102152 may host terrestrial rocky planets,” ESO stated.

Better yet, separate observations showed that there are no giant planets close to the star — leaving room for Earth-sized planets to flourish.

The research is available in a recent edition of Astrophysical Letters.

Source: European Southern Observatory

August 22, 2013December 30, 2015 by Tammy Plotner

Flicker… A Bright New Method of Measuring Stellar Surface Gravity

A simple, yet elegant method of measuring the surface gravity of a star has just been discovered. These computations are important because they reveal stellar physical properties and evolutionary state – and that’s not all. The technique works equally well for estimating the size of hundreds of exoplanets. Developed by a team of astronomers and headed by Vanderbilt Professor of Physics and Astronomy, Keivan Stassun, this new technique measures a star’s “flicker”. Continue reading “Flicker… A Bright New Method of Measuring Stellar Surface Gravity”

July 10, 2013December 23, 2015 by Jason Major

ALMA Spots a Nascent Stellar Monster

ALMA/Spitzer image of a monster star in the process of forming

Even though it comprises over 99% of the mass of the Solar System (with Jupiter taking up most of the rest) our Sun is, in terms of the entire Milky Way, a fairly average star. There are lots of less massive stars than the Sun out there in the galaxy, as well as some real stellar monsters… and based on new observations from the Atacama Large Millimeter/submillimeter Array, there’s about to be one more.

Early science observations with ALMA have provided astronomers with the best view yet of a monster star in the process of forming within a dark cloud of dust and gas. Located 11,000 light-years away, Spitzer Dark Cloud 335.579-0.292 is a stellar womb containing over 500 times the mass of the Sun — and it’s still growing. Inside this cloud is an embryonic star hungrily feeding on inwardly-flowing material, and when it’s born it’s expected to be at least 100 times the mass of our Sun… a true stellar monster.

The location of SDC 335.579-0.292 in the southern constellation of Norma (ESO, IAU and Sky & Telescope)

The star-forming region is the largest ever found in our galaxy.

“The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud,” said Nicolas Peretto of CEA/AIM Paris-Saclay, France, and Cardiff University, UK. “We wanted to see how monster stars form and grow, and we certainly achieved our aim! One of the sources we have found is an absolute giant — the largest protostellar core ever spotted in the Milky Way.”

Watch: What’s the Biggest Star in the Universe?

SDC 335.579-0.292 had already been identified with NASA’s Spitzer and ESA’s Herschel space telescopes, but it took the unique sensitivity of ALMA to observe in detail both the amount of dust present and the motion of the gas within the dark cloud, revealing the massive embryonic star inside.

“Not only are these stars rare, but their birth is extremely rapid and their childhood is short, so finding such a massive object so early in its evolution is a spectacular result.”

– Team member Gary Fuller, University of Manchester, UK

The image above, a combination of data acquired by both Spitzer and ALMA (see below for separate images) shows tendrils of infalling material flowing toward a bright center where the huge protostar is located. These observations show how such massive stars form — through a steady collapse of the entire cloud, rather than through fragmented clustering.

SDC 335.579-0.292 seen in different wavelengths of light.

“Even though we already believed that the region was a good candidate for being a massive star-forming cloud, we were not expecting to find such a massive embryonic star at its center,” said Peretto. “This object is expected to form a star that is up to 100 times more massive than the Sun. Only about one in ten thousand of all the stars in the Milky Way reach that kind of mass!”

(Although, with at least 200 billion stars in the galaxy, that means there are still 20 million such giants roaming around out there!)

What Happens When Stars Collide? In This Case, A Newly Observed Kind of Pulsating Star

Artist's impression of the eclipsing, pulsating binary star J0247-25. (Credit: Keele University)

It sure would be interesting to watch two stars run into each other — from a safe distance, of course. One can imagine there would be quite the titanic battle going on between their competing gravitational forces, throwing off gas and matter as they collide.

They also leave behind interesting echoes, at least according to new research. A European team looked at the leftovers of one collision and found a type of pulsating star that has never been seen before.

It’s common for stars to form in groups or to be paired up, since they form from immense gas clouds. Sometimes, a red giant star in a binary system gets so big that it will bump into a companion star orbiting nearby. This crash could shave 90% of the red giant star’s mass off, but astronomers are still trying to get their heads around what happens.

Eclipsing Binaries — Artists impression of a binary star system (courtesy NASA)

“Only a few stars that have recently emerged from a stellar collision are known, so it has been difficult to study the connection between stellar collisions and the various exotic stellar systems they produce,” Keele University, which led the research, stated.

Researchers who made the find were actually on the hunt for alien planets. They turned up what is called an “eclipsing” binary system, meaning that one of the stars passes in front of the other from the perspective of Earth.

The scientists then used a high-speed camera on the Very Large Telescope in Chile called ULTRACAM. The camera is capable of taking up to 500 pictures a second to track fast-moving astronomical events.

Observations revealed that “the remnant of the stripped red giant is a new type of pulsating star,” Keele stated.

The Very Large Telescope (VLT) at ESO's Cerro Paranal observing site in the Atacama Desert of Chile, consisting of four Unit Telescopes with main mirrors 8.2-m in diameter and four movable 1.8-m diameter Auxiliary Telescopes. The telescopes can work together, in groups of two or three, to form a giant interferometer, allowing astronomers to see details up to 25 times finer than with the individual telescopes. Credit: Iztok Boncina/ESO — The Very Large Telescope (VLT) at ESO’s Cerro Paranal observing site in the Atacama Desert of Chile, consisting of four Unit Telescopes with main mirrors 8.2-m in diameter and four movable 1.8-m diameter Auxiliary Telescopes. The telescopes can work together, in groups of two or three, to form a giant interferometer, allowing astronomers to see details up to 25 times finer than with the individual telescopes. Credit: Iztok Boncina/ESO

“We have been able to find out a lot about these stars, such as how much they weigh, because they are in a binary system,” stated Pierre Maxted, an astrophysicist at Keele.

“This will really help us to interpret the pulsation signal and so figure out how these stars survived the collision and what will become of them over the next few billion years.”

The next step for the researchers will be to calculate when the star will begin cooling down and become a white dwarf, which is what is left behind after a star runs out of fuel to burn.

Check out more details of the find in Nature.

Source: Keele University

June 11, 2013December 23, 2015 by Shannon Hall

A Rare Opportunity to Watch a Blue Straggler Forming

The globular cluster NGC 6388. Blue stragglers may clearly be seen around the edges. More are hidden within the central core. Credit: ESO

A unique and enigmatic variety of stars known as blue stragglers appear to defy the normal stellar aging process. Discovered in globular clusters, they appear much younger than the rest of the stellar population. Since their discovery in 1953, astronomers have been asking the question: how do these stars regain their youth?

For years, two theories have persisted. The first theory suggests that two stars collide, forming a single more massive star. The second theory proposes that blue stragglers emerge from binary pairs. As the more massive star evolves and expands, it blows material onto the smaller star. In both theories, the star grows steadily more massive and bluer – it regains its youth.

But now, a surprising finding may lend credence to the second theory. Astronomers at the Nicolaus Copernicus Astronomical Center in Poland recently observed a blue straggler caught in the midst of forming!

The binary system that was studied, known as M55-V60, is located within the globular cluster M55. Dr. Michal Rozyczka, one of the research scientists on the project, told Universe Today, “The system is a showcase example of a blue straggler formed via the theoretically predicted peaceful mass exchange between its components.”

The team used both photometric (the overall light from the system) and spectroscopic (the light spread out into a range of wavelengths) observations. The photometric data revealed the light curve – the change in brightness due to one star passing in front of the other – of the system. This provided evidence that the astronomers were looking at a binary system.

From the spectroscopic data, shifts in wavelength reveal the velocity (along the line of sight) of a source. The research team noted that the system’s center of mass was moving with respect to the binary system. This will occur in a semi-detached binary system, where mass transfers from one star to the other. As it does this, the center of mass will follow the mass-transfer.

From both photometric and spectroscopic observations (which covered more than 10 years!) the team was able to verify that this object is not only a binary, but a semi-detached binary, residing at the edge of M55.

An artist's conception of how a blue straggler may form from a binary system. Credit:NASA/ESA — An artist’s conception of how a blue straggler may form from a binary system. Credit: NASA/ESA

“The system is semi-detached with the less massive (secondary) component filling its Roche lobe,” explained Dr. Rozyczka. “The secondary has a tearlike shape, with the tip of the tear directed toward the more massive primary. A stream of gas flows out of the tip along a curved path and hits the primary.”

How do we know that it is in fact a blue straggler? The simple answer is that the secondary star, with is gaining mass, appears bluer than normal. This blue straggler is clearly in the process of forming. It is the second observation of such a formation, with the first being V228 in the globular cluster: 47 Tuc.

This research verifies that semi-detached binaries are a viable formation mechanism for blue stragglers. The binary was discovered by happenstance, in a project aimed at determining accurate ages and distances of nearby clusters. It’s certainly a surprising result from the survey.

The results will be published in Acta Astronomica, a peer-reviewed scientific journal located in Poland (preprint available here).

May 29, 2013April 26, 2016 by Elizabeth Howell

Why Are Dying Stars in 47 Tucanae Cooling Off So Slowly?

The Hubble Space Telescope is going to be used to settle an argument. It’s a conflict between computer models and what astronomers are seeing in a group of stars in 47 Tucanae.

White dwarfs — the dying embers of stars who have burnt off all their fuel — are cooling off slower than expected in this southern globular cluster, according to previous observations with the telescope’s Wide Field Camera and Advanced Camera for Surveys.

Puzzled astronomers are now going to widen that search in 47 Tucanae (which initially focused on a few hundred objects) to 5,000 white dwarfs. They do have some theories as to what might be happening, though.

White dwarfs, stated lead astronomer Ryan Goldsbury from the University of British Columbia, have several factors that chip in to the cooling rate:

The Hubble Space Telescope. Image credit: NASA, tweaked by D. Majaess.

– High-energy particle production from the white dwarfs;

– What their cores are made up of;

– What their atmospheres are made up of;

– Processes that bring energy from the core to the surface.

Somewhere, somehow, perhaps one of those factors is off.

This kind of thing is common in science, as astronomers create these programs according to the best educated guesses they can make with respect to the data in front of them. When the two sides don’t jive, they do more observations to refine the model.

“The cause of this difference is not yet understood, but it is clear that there is a discrepancy between the data and the models,” stated the Canadian Astronomical Society (CASCA) and the University of British Columbia in a press release.

Since the white dwarfs are in a cluster that presumably formed from the same cloud of gas, it allows astronomers to look at a group of stars at a similar distance and to determine the distribution of masses of stars within the cluster.

“Because all of the white dwarfs in their study come from a single well-studied star cluster, both of these bits of information can be independently determined,” the release added.

You can read the entire article on the previous Hubble research on 47 Tucanae at the Astrophysical Journal.

Today’s announcement took place during the annual meeting of CASCA, which is held this year in Vancouver.

Source: CASCA/UBC