Posted on by Nancy Atkinson

Astronomers Uncover a Crime of Galactic Proportions

As the Milky Way rises over the horizon at the European Southern Observatory, its companion galaxies also come into view. Credit: ESO/Y. Beletsky

A previously undetected heist of stars was uncovered by astronomers who were actually looking for why an unexpected amount of microlensing events were being seen around the outskirts of the Milky Way. Instead, they found the Large Magellanic Cloud (LMC) had been stealing stars from its neighbor, the Small Magellanic Cloud (SMC), leaving behind a trail of stars. Although the crime was likely committed hundreds of milllions of years ago during a collision between the two galaxies, the new information is helping astronomers to understand the history of these two galaxies that are in our neighborhood.

“You could say we discovered a crime of galactic proportions,” said Avi Loeb of the Harvard-Smithsonian Center for Astrophysics.

The Large Magellanic Cloud almost got away with it, if it wasn’t for those meddling astronomers….

Astronomers were originally monitoring the LMC to hunt for the reason for the unexpected microlensing events. Their initial hypothesis was that massive compact halo objects, or MACHOs were causing the effect, where a nearby object passes in front of a more distant star. The gravity of the closer object bends light from the star like a lens, magnifying it and causing it to brighten. The MACHOs were thought to be faint objects, roughly the mass of a star, but not much is known about them. Several surveys looked for MACHOs in order to find out if they could be a major component of dark matter – the unseen stuff that holds galaxies together.

In order for MACHOs to make up dark matter, they must be so faint that they can’t be directly detected. So, the team of astronomers hoped to see MACHOs within the Milky Way by lensing distant LMC stars.

“We originally set out to understand the evolution of the interacting LMC and SMC galaxies,” said lead author of a new paper on the results, Gurtina Besla of Columbia University. “We were surprised that, in addition, we could rule out the idea that dark matter is contained in MACHOs.”

“Instead of MACHOs, a trail of stars removed from the SMC is responsible for the microlensing events,” said Loeb.

Only a fast-moving population of stars could yield the observed rate and durations of the microlensing events. The best way to get such a stellar population is a galactic collision, which appears to have occurred in the LMC-SMC system.

“By reconstructing the scene, we found that the LMC and SMC collided violently hundreds of millions of years ago. That’s when the LMC stripped out the lensed stars,” said Loeb.

Their research also supports recent findings suggesting that both Magellanic Clouds are on their first pass by the Milky Way.

However, this isn’t a closed case. The evidence for the trail of lensed stars is persuasive, but they haven’t been directly observed yet. A number of teams are searching for the signatures of these stars within a bridge of gas that connects the Magellanic Clouds.

The simulation results will be published in the Monthly Notices of the Royal Astronomical Society.

Read the team’s paper: The Origin of the Microlensing Events Observed Towards the LMC and the Stellar Counterpart of the Magellanic Stream

Source: CfA

Posted on by John Williams

Blowing a Super-duper Celestial Bubble

Image credit: X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL, Optical: ESO/WFI/2.2-m. Zoom by John Williams/TerraZoom using Zoomify

When NASA combines images from different telescopes, they create dazzling scenes of celestial wonder and in the process we learn a few more things. Behold this wonder of combined light, known as LHA 120-N 44, or N 44 for short. Zoom into the scene using the toolbar at the bottom of the image. Click the farthest button on the right of the toolbar to see this wonder in full-screen. (Hint: press the “Esc” key to get back to work)

Continue reading “Blowing a Super-duper Celestial Bubble”

Posted on by Nancy Atkinson

Special New Panorama Celebrates Hubble’s 22nd Anniversary

A mosaic view of 30 Doradus, assembled from Hubble Space Telescope photos, Credit: NASA, ESA, ESO,

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Happy birthday to the Hubble Space Telescope! On April 24, 1990, HST was launched into low Earth orbit. Now, nearly 22 years later, Hubble is still producing incredible, stunning images of the farthest reaches of the Universe. For this year’s anniversary, the Hubble team took a special panoramic view of 30 Doradus, a raucous stellar breeding ground, located in the heart of the Tarantula nebula. The image comprises one of the largest mosaics ever assembled from Hubble photos and consists of observations taken by Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, combined with observations from the European Southern Observatory’s MPG/ESO 2.2-metre telescope that trace the location of glowing hydrogen and oxygen.

The Tarantula nebula is 170,000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way. No known star-forming region in our galaxy is as large or as prolific as 30 Doradus.

The stars in this image add up to a total mass millions of times bigger than that of our Sun. The image is roughly 650 light-years across and contains some rambunctious stars, from one of the fastest rotating stars to the speediest and most massive runaway star.

The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the stars’ birth and evolution. Many small galaxies have more spectacular starbursts, but the Large Magellanic Cloud’s 30 Doradus is one of the only star-forming regions that astronomers can study in detail. The star-birthing frenzy in 30 Doradus may be partly fueled by its close proximity to its companion galaxy, the Small Magellanic Cloud.

The image reveals the stages of star birth, from embryonic stars a few thousand years old still wrapped in dark cocoons of dust and gas to behemoths that die young in supernova explosions. 30 Doradus is a star-forming factory, churning out stars at a furious pace over millions of years. The Hubble image shows star clusters of various ages, from about 2 million to about 25 million years old.

The image was made from 30 separate fields, 15 from each camera. Hubble made the observations in October 2011. Both cameras were making observations at the same time.

Take an interactive tour of the Tarantula Nebula at the HubbleSite

Source: ESA’s Hubble website

Posted on by Tammy Plotner

We Are Stardust… We Are Cold Then

This new image shows the Large Magellanic Cloud galaxy in infrared light as seen by the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions, and NASA's Spitzer Space Telescope. Image credit: ESA/NASA/JPL-Caltech/STScI

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When we think of stars, we might think of their building blocks as white hot… But that’s not particularly the case.The very “stuff” that creates a sun is cold dust and in this combined image produced by the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions; and NASA’s Spitzer Space Telescope, we’re taking an even more incredible look into the environment which forms stars. This new image peers into the dusty arena of both the Large and Small Magellanic Clouds – just two of our galactic neighbors.

Through the infra-red eyes of the Herschel-Spitzer observation, the Large Magellanic Cloud would almost appear to look like a gigantic fireball. Here light-years long bands of dust permeate the galaxy with blazing fields of star formation seen in the center, center-left and top right (the brightest center-left region is called 30 Doradus, or the Tarantula Nebula. The Small Magellanic Cloud is much more disturbed looking. Here we see a huge filament of dust to the left – known as the galaxy’s “wing” – and, to the right, a deep bar of star formation.

This new image shows the Small Magellanic Cloud galaxy in infrared light from the Herschel Space Observatory a European Space Agency-led mission with important NASA contributions, and NASA's Spitzer Space Telescope. Image credit: ESA/NASA/JPL-Caltech/STScI

What makes these images very unique is that they are indicators of temperature within the Magellanic Clouds. The cool, red areas are where star formation has ceased or is at its earliest stages. Warm areas are indicative of new stars blooming to life and heating the dust around them. “Coolest areas and objects appear in red, corresponding to infrared light taken up by Herschel’s Spectral and Photometric Imaging Receiver at 250 microns, or millionths of a meter. Herschel’s Photodetector Array Camera and Spectrometer fills out the mid-temperature bands, shown in green, at 100 and 160 microns.” says the research team. “The warmest spots appear in blue, courtesy of 24- and 70-micron data from Spitzer.”

Both the LMC and SMC are the two largest satellite galaxies of the Milky Way and are cataloged as dwarf galaxies. While they are large in their own right, this pair contains fewer essential star-forming elements such as hydrogen and helium – slowing the rate of star growth. Although star formation is generally considered to have reached its apex some 10 billion years ago, some galaxies were left with less basic materials than others.

“Studying these galaxies offers us the best opportunity to study star formation outside of the Milky Way,” said Margaret Meixner, an astronomer at the Space Telescope Science Institute, Baltimore, Md., and principal investigator for the mapping project. “Star formation affects the evolution of galaxies, so we hope understanding the story of these stars will answer questions about galactic life cycles.”

Original Story Source: NASA/Herschel News.

Posted on by Tammy Plotner

Incredible Spinning Star Rotates At A Million Miles Per Hour!

This is an artist's concept of the fastest rotating star found to date. The massive, bright young star, called VFTS 102, rotates at a million miles per hour, or 100 times faster than our Sun does. Centrifugal forces from this dizzying spin rate have flattened the star into an oblate shape and spun off a disk of hot plasma, seen edge on in this view from a hypothetical planet. The star may have "spun up" by accreting material from a binary companion star. The rapidly evolving companion later exploded as a supernova. The whirling star lies 160,000 light-years away in the Large Magellanic Cloud, a satellite galaxy of our Milky Way. Credit: NASA, ESA, and G. Bacon (STScI)

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Located in the Large Magellanic Cloud, a star named VFTS 102 is spinning its heart out… Literally. Rotating at a mind-numbing speed of a million miles per hour (1.6 million kph), this hot blue giant has reached the edge where centrifugal forces could tear it apart. It’s the fastest ever recorded – 300 times faster than our Sun – and may have been split off from a double star system during a violent explosion.

Thanks to ESO’s Very Large Telescope at the Paranal Observatory in Chile, an international team of astronomers studying the heaviest and brightest stars in the Tarantula Nebula made quite a discovery – a huge blue star 25 times the mass of the Sun and about one hundred thousand times brighter was cruising through space at a speed which drew their attention.

“The remarkable rotation speed and the unusual motion compared to the surrounding stars led us to wonder if this star had an unusual early life. We were suspicious.” explains Philip Dufton (Queen’s University Belfast, Northern Ireland, UK), lead author of the paper presenting the results.

ESO's Very Large Telescope has picked up the fastest rotating star found so far. This massive bright young star lies in our neighbouring galaxy, the Large Magellanic Cloud, about 160 000 light-years from Earth. Astronomers think that it may have had a violent past and has been ejected from a double star system by its exploding companion. Credit: ESO

What they’ve discovered could possibly be a “runaway star” – one that began life as a binary, but may have been ejected during a supernova event. Further evidence which supports their theory also exists: the presence of a pulsar and a supernova remnant nearby. But what made this crazy star spin so fast? It’s possible that if the two stars were very close that streaming gases could have started the incredible rotation. Then the more massive of the pair blew its stack – expelling the star into space. So what would be left? It’s elementary, Watson… A supernova remnant, a pulsar and a runaway!

Even though this is a rather tidy conclusion, there’s always room for doubt. As Dufton concludes, “This is a compelling story because it explains each of the unusual features that we’ve seen. This star is certainly showing us unexpected sides of the short but dramatic lives of the heaviest stars.”

Original Story Source: HubbleSite News Release and ESO News Release. For Further Reading: he VLT-FLAMES Tarantula Survey I. Introduction and observational overview.

Posted on by Tammy Plotner

NGC 1846 – Hubble Reveals Peculiar Life And Death Of A Stellar Population

NASA's Hubble Finds Stellar Life and Death in a Globular Cluster - Credit: HST/NASA

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About 160,000 light years away in the direction of southern constellation Doradus, sits a globular cluster. It’s not a new target for the Hubble Space Telescope, but it has had a lot to say for itself over the last twelve years. It’s actually part of the Large Magellanic Cloud, but it’s no ordinary ball of stars. When it comes to age, this particular region is mighty complex…

In a 34 minute exposure taken almost a half dozen years ago, the Hubble snapped both life and death combined in an area where all stars were once assumed to be the same age. Globular clusters, as we know, are spherical collections of stars bound by gravity which orbit the halo of many galaxies. At one time, astronomers assumed their member stars were all the same age – forming into their own groups at around the same time the parent galaxy formed. But now, evidence points toward these balls of stars as having their own agenda – and may have evolved independently over the course of several hundreds of million years. What’s more, we’re beginning to learn that globular cluster formation may differ from galaxy to galaxy, too. Why? Chances are they may have encountered additional molecular clouds during their travels which may have triggered another round of star formation.

“An increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations.” says Giampaolo Piotto of the University of Padova, Italy. “These multiple populations manifest themselves in a split of different evolutionary sequences as observed in the cluster color-magnitude diagrams. Multiple stellar populations have been identified in Galactic and Magellanic Cloud clusters.”

However, it’s not the individual stars which make this Hubble image such a curiosity, it’s the revelation of a planetary nebula. This means a huge disparity in the member star’s ages…. one of up to 300 million years. Is it possible that the shell and remains of this dead star is a line-of-sight phenomenon, or is it truly a cluster member?

“We report on Hubble Space Telescope/ACS photometry of the rich intermediate-age star cluster NGC 1846 in the Large Magellanic Cloud, which clearly reveals the presence of a double main-sequence turn-off in this object. Despite this, the main-sequence, subgiant branch and red giant branch are all narrow and well defined, and the red clump is compact.” says A. D. Mackey and P. Broby Nielsen. ” We examine the spatial distribution of turn-off stars and demonstrate that all belong to NGC 1846 rather than to any field star population. In addition, the spatial distributions of the two sets of turn-off stars may exhibit different central concentrations and some asymmetries. By fitting isochrones, we show that the properties of the colour–magnitude diagram can be explained if there are two stellar populations of equivalent metal abundance in NGC 1846, differing in age by around 300 million years.”

So what’s wrong with the picture? Apparently nothing. The findings have been studied and studied again for errors and even “contamination” by field stars in relation to NGC1846’s main sequence turn off. It’s simply a bit of a cosmic riddle just waiting for an explanation.

“We propose that the observed properties of NGC 1846 can be explained if this object originated via the tidal capture of two star clusters formed separately in a star cluster group in a single giant molecular cloud.” concludes Mackey and Nielson. “This scenario accounts naturally for the age difference and uniform metallicity of the two member populations, as well as the differences in their spatial distributions.”

Original Story Source: NASA’s Hubble Finds Stellar Life and Death in a Globular Cluster. For Further Reading: A double main-sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud, Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. I. NGC 1846 and its Wide Main-Sequence Turnoff and Multiple stellar populations in three rich Large Magellanic Cloud star clusters.

Posted on by Nancy Atkinson

Colorful Cluster of Stars Competes with the Tarantula Nebula

The star cluster NGC 2100 in the Large Magellanic Cloud. Credit: ESO

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Who can shine the brightest in the Large Magellanic Cloud? A brilliant cluster of stars, open cluster NGC 2100 shines brightly, competing with the nearby Tarantula Nebula for bragging rights in this image from ESO’s New Technology Telescope (NTT).

Observers perhaps often overlook NGC 2100 because of its close proximity to the impressive Tarantula. The glowing gas of the Tarantula Nebula even tries to steal the limelight in this image — the bright colors here are from the nebula’s outer regions, and is lit up by the hot young stars that lie within the nebula itself.

But back to the star cluster — this brilliant star cluster is around 15 million years old, and located in the Large Magellanic Cloud, a nearby satellite galaxy of the Milky Way. An open cluster has stars that are relatively loosely bound by gravity. These clusters have a lifespan measured in tens or hundreds of millions of years, as they eventually disperse through gravitational interaction with other bodies.

This new picture was created from exposures through several different color filters.The stars are shown in their natural colors, while light from glowing ionized hydrogen (shown here in red) and oxygen (shown in blue) is overlaid.

See more info at the ESO website.

Posted on by Nancy Atkinson

Hubble Captures Beautiful Baby Stars

Hubble view of the huge star formation region N11 in the Large Magellanic Cloud. Credit: NASA, ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain).

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Within the Large Magellenic Cloud is one of the most active star forming regions in our nearby Universe. This new Hubble image highlights N11 – also known as the Bean Nebula — a beautiful region of energetic star formation. The billowing pink clouds that look like cotton candy and bright bubbles of glowing gasses and are telltale signs that stars are being created. Click the image for a larger, hi-res version.

Beans, bubbles and candy aren’t the only terrestrial shapes to be found in this spectacular image from the Hubble Space Telescope.

If you zoom into upper left (click this link for a zoom video) you’ll find a rose: The Rose Nebula LHA 120-N 11A. Its rose-like petals of gas and dust are illuminated from within, thanks to the radiation from the massive hot stars at its centre. N11A is relatively compact and dense and is the site of the most recent burst of star development in the region.

If you live in the southern hemisphere, both the Large Magellanic Cloud and its small companion, the Small Magellanic Cloud, are easily seen with the unaided eye. That’s a sight I would someday love to see!

For more videos and images of this region, see this ESA Hubble page.

Posted on by Nancy Atkinson

Incredible New Hubble Image is Full of Stars!

This is a Hubble image of the star cluster R136 at the heart of the Tarantula Nebula. It's a starburst region that's home to several extremely massive stars, including R136a1, which is almost 200 times more massive than the Sun. Image Credit: By NASA, ESA, F. Paresce (INAF-IASF, Bologna, Italy), R. O'Connell (University of Virginia, Charlottesville), and the Wide Field Camera 3 Science Oversight Committee

A brand new Hubble image from Wide Field Camera 3 shows the most detailed view of the largest stellar nursery in our local galactic neighborhood. The massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way. There is no known star-forming region in our galaxy as large or as prolific as 30 Doradus. Many of the diamond-like icy blue stars are among the most massive stars known. Several of them are over 100 times more massive than our Sun. In a few million years, this region should provide an incredible show: that’s when these hefty stars are destined to pop off like a string of firecrackers, as supernovas.

The image, taken in ultraviolet, visible, and red light by Hubble’s Wide Field Camera 3, spans about 100 light-years. The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the birth and evolution of stars in the universe. The Hubble observations were taken Oct. 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen.

Ground-based version of the Doradus Constellation. Credit: A. Fujii
Ground-based version of the Doradus Constellation. Credit: A. Fujii

The LMC is located 170,000 light-years away and is a member of the Local Group of Galaxies, which also includes the Milky Way.

Click here for larger (and eye-popping!) versions of this image.

You can also “zoom” in and out of this image here on the “Starry Critters” website.
Source: HubbleSite