Astronomy Archives

January 29, 2012December 24, 2015 by Amy Shira Teitel

NASA’s New Eyes in the Sky

An artist's concept of NuSTAR in space. Image credit: NASA/JPL-Caltech/Orbital

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On March 14, NASA will launch the Nuclear Spectroscopic Telescope Array or NuSTAR. This is the first time a telescope will focus on high energy X-rays, effectively opening up the sky for more sensitive study. The telescope will target black holes, supernova explosions, and will study the most extreme active galaxies. NuSTAR’s use of high-energy X-rays have an added bonus: it will be able to capture and compose the most detailed images ever taken in this end of the electromagnetic spectrum.

NuSTAR’s eyes are two Wolter-I optic units; once in orbit each will ‘look’ at the same patch of sky. The Wolter-I mirror works by reflecting an X-ray twice, once off of an upper mirror shaped like a parabola and again off a lower mirror shaped like a hyperbola. The mirrors are nearly parallel to the direction of the incoming X-ray, reflecting most of the X-ray instead of absorbing it, but the slight angle allows for a very small collection area per surface. To get a full picture, mirrors of varying size are nested together.

Technicians work on NuSTAR this month at the Orbital Science Corporation in Dulles, Virginia. Image credit: NASA/JPL-Caltech/Orbital

Each of NuSTAR’s eyes, each unit, are made of 133 concentric shells of mirrors shaped from flexible glass like that found in laptop computer screens. This is an improvement over past missions like Chandra and XMM-Newton that both used high density materials such as Platinum, Iridium and Gold as mirror coatings. These materials achieve great reflectivity for low energy X-rays but can’t capture high energy X-rays.

Like human eyes, NuSTAR’s optical units are co-aligned to give the telescope a wider field of view and enable the capture of more sensitive images. These images will be made into detailed composites by scientists on the ground.

Also like human eyes, NuSTAR’s optical units need to be distanced from one another since X-ray telescopes require long focal lengths. In other words, the optics must be separated by several meters from the detectors. NuSTAR does this with a 33 foot (10 metre) long mast or boom between units.

Previous X-ray missions have accommodated these long focal lengths by launching fully deployed observatories on large rockets. NuSTAR won’t. It has a unique deployable mast that will extend once the payload is in orbit. This allows for a launch on the small Pegasus rocket. Undeployed, the telescope measures just 2 metres in length and one metre in diameter.

During its two-year primary mission, NuSTAR will map the celestial sky focussing on black holes, supernova remnants, and particle jets traveling near the speed of light. It will also look at the Sun. Observations of microflares could explain the temperature of the Sun’s corona. It will also search the Sun for evidence of a hypothesized dark matter particle to test a theory about dark matter.

NuSTAR's mast. Image credit: NASA/JPL-Caltech/Orbital

“NuSTAR will provide an unprecedented capability to discover and study some of the most exotic objects in the universe, from the corpses of exploded stars in the Milky Way to supermassive black holes residing in the hearts of distant galaxies,” said Lou Kaluzienski, NuSTAR program scientist at NASA Headquarters in Washington.

The telescope shipped from the Orbital Sciences Corporation in Dulles, Virginia to Vandenberg Air Force Base in California on January 27. There, it will be mated to its Pegasus launch vehicle on February 17. It will launch from underneath the L-1011 “Stargazer” aircraft on March 14 after taking off near the equator from Kwajalein Atoll in the Pacific.

Source: NASA

A Pegasus rocket launches from underneath a L-1011 "Stargazer" aircraft, just like NuSTAR will do in March. Image credit: NASA/JPL-Caltech/Orbital

January 28, 2012December 24, 2015 by Steve Nerlich

Journal Club – Transit of Venus

Today's Journal Club is about a new addition to the Standard Model of fundamental particles.

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According to Wikipedia, a journal club is a group of individuals who meet regularly to critically evaluate recent articles in scientific literature. Being Universe Today if we occasionally stray into critically evaluating each other’s critical evaluations, that’s OK too. And of course, the first rule of Journal Club is… don’t talk about Journal Club.

So, without further ado – today’s journal article under the microscope is about the 2012 transit of Venus.

Today’s article:
Sigismondi Solar diameter with 2012 Venus transit.

The 2012 transit of Venus will proceed for nearly 7 hours over 5 and 6 June (UTC). It’s not likely that we are going to squeeze a huge amount of ground-breaking science out of this event, which was closely monitored by 21st century technology the last time it happened in 2004. But Sigismondi argues that a more exacting observation of this transit should enable us to clean up some of the historical data from previous transits by kind of reverse-engineering some of the inherent inaccuracies that plagued earlier measurements.

The point of such an exercise may become clear by considering a claim made back in 1979 that the Sun was shrinking – based on an analysis of 120 years of Greenwich Observatory solar measurement data. Apparently this finding has since been hijacked to support a young Earth hypothesis – as in if the Sun is shrinking so fast, then how can it possibly be billions or even millions of years old and yada, yada.

Shapiro was able to quickly counter the shrinking data finding in a 1980 publication (in Science), demonstrating that transits of Mercury data, going back to 1736, indicated that the solar diameter had remained constant to within 0.3 arcseconds. This was then followed up by Parkinson et al, also in a 1980 publication (in Nature), demonstrating that changes in the Greenwich solar data correlated closely with changes in instrumentation, atmospheric conditions and in the people taking the measurements (and thanks to Matt Tiscareno for this story).

Anyhow, Sigismondi outlines how the solar diameter can be measured from the transit of Venus’ outline when it contacts each edge of the Sun – and then discusses a method whereby the ‘notorious’ black drop effect can be eliminated. The black drop effect involves the black shape of Venus seemingly to elongate as it approaches the edge of the Sun – which had confounded all measurements taken prior to 2004.

Transits of Venus generally happen in pairs separated by 8 years, with either 105.5 or 121.5 years separating the last of the pair and the first of the next. Apparently Kepler was the first person to predict a transit of Venus in 1631 – but he failed to predict that it would not be visible from Europe. So it fell to Jeremiah Horrocks and William Crabtree to make the first scientific observation of a transit 8 years later in December 1639. The next two were in June 1761 and June 1769, the latter famously observed from Tahiti by Lieutenant James T Cook (OK, kidding about the T) and then there were two more in December 1874 and December 1882.

Then another 121.5 years passed until June 2004 – now to be followed by this year’s June 2012 transit, being the 7th ever scientifically recorded transit. And BTW here’s an original drawing by James Cook of the June 1769 transit, showing the black drop effect.

So… comments? Is it OK to get a little bit excited about ‘just another’ transit of Venus – since it’s only the 7th we have ever recorded data about? Did you know that the plural of ephemeris (the position of something in the sky) is ephemerides? Want to suggest an article for the next edition of Journal Club?

January 21, 2012December 24, 2015 by Steve Nerlich

Journal Club – When White Dwarfs Collide

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So, without further ado – today’s scheduled-for-demolition journal article is about the ongoing problem of figuring out what events precede a Type 1a supernova.

Today’s article:
Dan et al How the merger of two white dwarfs depends on their mass ratio: orbital stability and detonations at contact.

There is growing interest about the nature of the events that precede Type 1a supernovae. We are confident that the progenitor stars of Type 1a supernovae are white dwarfs – but these stars have generally very long lives, making it difficult to identify stars that are potentially on the brink of exploding.

We are also confident that something happens to cause a white dwarf to accumulate extra mass until it reached its Chandrasekhar limit (around 1.4 solar masses, depending on the star’s spin).

For a long time, it had been assumed that a Type 1a supernova probably arose from a binary star system with a white dwarf and another star that had just evolved into a red giant, its outer layers swelling out into the gravitational influence of the white dwarf star, This new material was accreted onto the white dwarf until it hit its Chandrasekhar limit – and then kabloowie.

However, the white-dwarf-red-giant-binary hypothesis is currently falling out of favour. It has always had the problem that any Type 1 supernovae has, by definition, almost no hydrogen absorption lines in its light spectrum – which makes sense for a Type 1a supernovae arising from a hydrogen-expended white dwarf – but then what happened to the new material supposedly donated by a red giant partner (which should have been mostly hydrogen)?

Also, the recently discovered Type 1a SN2011fe was observed just as its explosion was commencing, allowing constraints to be placed on the nature of its progenitor system. Apparently there is no way the system could have included something as big as a red giant and so the next most likely cause is the merging (or collision) of two white dwarfs.

Other modelling research has also concluded that the two white dwarf merger scenario maybe statistically more likely to take place than the red giant accretion scenario – since the latter requires a lot of Goldilocks parameters (where everything has to be just right for a Type 1a to eventuate).

This latest paper expands the possible scenarios under which a two white dwarf merger could produce a Type 1a supernovae – and finds a surprising number of variations with respect to mass, chemistry and the orbital proximities of each star. Of course, it is just modelling but it does challenge the current assertion at the relevant Wikipedia entry that white dwarf mergers are a second possible, but much less likely, mechanism for Type 1a supernovae formation.

So – comments? Anyone want to defend the old red-giant-white-dwarf scenario? Does computer modelling count as a form of evidence? Want to suggest an article for the next edition of Journal Club?

January 19, 2012December 24, 2015 by Ray Sanders

Citizen Science: GLOBE at Night

[/caption]Are you a fan of Citizen Science? Do you enjoy participating in projects that help researchers and possibly the environment?

GLOBE at Night is one such program! By taking naked-eye observations of the night sky in your area, you can help a world-wide effort to track the effects of light pollution.

Here’s all the info you need in order to participate in GLOBE at Night during 2012.

For starters, what is GLOBE at Night?

The GLOBE at Night program is an international citizen-science campaign designed to raise public awareness of the impact of light pollution on our night skies. GLOBE at Night aims to raise awareness by inviting citizen-scientists to measure their night sky brightness and submit their observations to a website from a computer or smart phone.

Light pollution not only threatens our “right to starlight”, but also affects energy consumption, wildlife and health. For the past six years, the GLOBE at Night campaign has been involving people in 115 countries.

Participating in GLOBE at Night requires only five easy steps:

1) Find your latitude and longitude.

2) Find Orion, Leo or Crux by going outside more than an hour after sunset (about 8-10pm local time).

3) Match your nighttime sky to one of the provided magnitude charts.

4) Report your observation.

5) Compare your observation to thousands around the world.

GaN_postcard2012.pdf-page2 — Map of 2011 GLOBE at Night participation. Image Credit: GLOBE at Night / NOAO

You can also use the new web application data submission process. The GLOBE at Night website is easy to use, comprehensive and holds an abundance of background information. The database is usable for comparisons with a variety of other databases, like how light pollution affects the foraging habits of bats.

If you’d like to learn more about GLOBE at Night, visit: http://www.globeatnight.org/ , or the 365 Days of Astronomy Podcast: GLOBE at Night Kickoff: Seeing the Light.

January 19, 2012December 24, 2015 by VirtualAstro

British TV Audience Discovers Potential New Planet

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A public “mass participation” push initiated on a UK television program to find planets beyond our Solar System has had an immediate result! On Monday, January 16, 2012 “BBC Stargazing LIVE” began its first of three nights of television programs live from Jodrell Bank Observatory in the UK. The series was hosted by Professor Brian Cox, comedian Dara O’Briain along with a number of other well known TV personalities, astronomers and scientists. There was even a guest appearance via satellite link from Captain Gene Cernan, the last man on the Moon.

As well as the main TV program, there were numerous local events across the UK and the viewers could “mass participate” in activities such as looking for extra solar planets with the citizen science project, Planethunters.org.

The website hosts data gathered by NASA’s Kepler space telescope, and asks volunteers to sift the information for anything unusual that might have been missed in a computer search. People are especially adept at seeing things that computers do not and the BBC Stargazing Live event was a golden opportunity to get many people looking. During the event, over a million classifications were made and 34 candidate planets found on the website in 48 hours.

On the last show of the series on Wednesday 18th January it was announced, that in particular, one planet candidate looks extremely promising, as it has been identified multiple times by PlanetHunter participants.

The planet is circling the star SPH10066540 and is described as being similar in size to Neptune, circles its parent every 90 days and is about a similar distance from its parent star as Mercury is from our Sun. It could be described as a hot Neptune.

Chris Holmes from Peterborough UK and Lee Threapleton also from the UK found the planet by searching through time-lapsed images of stars looking for the periodic dips in brightness that result every time a planet passes in front of (transits) one of those stars.

_57971375_q41_candidate_marked.002 — Credit: planethunters.org

A transit has to be observed several times before a planet will be confirmed. For the orange dwarf star SPH10066540, five such events have now been seen in the Kepler data making it a strong candidate for an extra solar planet.

“There’s more work to be done to confirm whether these candidates are true planets,” wrote the PlanetHunters team on their blog, “in particular, we need to talk to our friends on the Kepler team – but we’re on our way.”

The NASA Kepler space telescope, launched in 2009, has been searching a part of space thought to have many stars similar to our own Sun.

You can try and find a new planet too by visiting planethunters.org it is incredibly simple and easy to do and requires no previous knowledge of astronomy.

How many more planets will be discovered?

January 19, 2012December 24, 2015 by Nancy Atkinson

A New Look at the Helix Nebula — a Giant “Eye” in Space

This comparison shows a new view of the Helix Nebula acquired with the VISTA telescope in infrared light (left) and the more familiar view in visible light from the MPG/ESO 2.2-metre telescope (right). The infrared vision of VISTA reveals strands of cold nebular gas that are mostly obscured in visible light images of the Helix. Credit: ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit

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Who is looking at who here? A brand new image of the Helix Nebula (breathlessly called the “Eye of God” in viral email messages) was taken by ESO’s VISTA telescope, at the Paranal Observatory in Chile. In infrared light — compared previous images of the Helix Nebula taken in visible light — the “eye” appears to have put on a colored contact lens, changing the color from blue to brown. What infrared really reveals are strands of cold gases within the nebula, as well as highlighting a rich background of stars and galaxies.

The Helix Nebula is a planetary nebula, and is located in the constellation Aquarius, about 700 light-years away from Earth. This strange object formed when a star like the Sun was in the final stages of its life. In fact, our own Sun might look like this one day, several billion years from now.

eso1205a — ESO’s VISTA telescope, at the Paranal Observatory in Chile, has captured a striking new image of the Helix Nebula. Credit: ESO/VISTA/J. Emerson.

The Helix Nebula is a huge cavern of glowing gases. The main ring of the Helix is about two light-years across, roughly half the distance between the Sun and the nearest star. However, material from the nebula spreads out from the star to at least four light-years. This is particularly clear in this infrared view since red molecular gas can be seen across much of the image.

At its center is a dying star which has ejected masses of dust and gas to form tentacle-like filaments stretching toward an outer rim composed of the same material. Unable to hold onto its outer layers, the hot central star is slowly shedding shells of gas that became the nebula. It is evolving to become a white dwarf star and appears as the tiny blue dot seen at the center of the image.

The VISTA telescope also reveals fine structure in the nebula’s rings. The infrared light picks out how the cooler, molecular gas is arranged. The material clumps into filaments that radiate out from the center and the whole view resembles a celestial firework display – or a giant eye.

Source: ESO

January 16, 2012December 24, 2015 by VirtualAstro

Why Does Sirius Twinkle?

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At this time of year, after dark we in the northern hemisphere are able to see the mighty constellation of Orion rise high in the sky with a very bright companion in a nearby constellation: Sirius – The Dog Star.

Sirius is the brightest star in the sky and can easily be found in the faint constellation of Canis Major to the left and below Orion. Its name comes from ancient Greek meaning “glowing” or “scorcher.”

Sirius (α CMa) is the alpha star in this trusty hound and is roughly 8.5 light years away from Earth, making it one of the closest stars to us. It has a tiny companion star making it a binary system composed of “Sirius A” the main component (which is a white main sequence star) and “Sirius B,” a white dwarf star. As seen with the naked eye, Sirius can be seen to twinkle many different colours low in the winter evening sky.

So why does Sirius twinkle?

It’s not just Sirius that twinkles; all stars twinkle. Light travels many light years from stars and right at the end of its journey, it hits Earth’s atmosphere, which consists of nitrogen, oxygen and other gasses.

Earth’s atmosphere is constantly swirling around, and wind and air currents etc distort light travelling through it. This causes the light to slightly bend or shimmer and the light from distant stars twinkle. An extreme, more down-to-Earth example of this would be heat rising off of a road or a desert causing objects behind it to distort, shimmer and change colour.

Sirius appears to twinkle or shimmer more than other stars for some very simple reasons. It is very bright, which can amplify atmospheric effects and it is also very low down in the atmosphere for those in the northern hemisphere. We are actually looking at it through a very dense part of the atmosphere which can be turbulent and contain many different particles and dust. The lower towards the horizon an observer is looking, the thicker the atmosphere. The higher an observer is looking, the thinner the atmosphere. This is also the cause of colourful sunrise and sunsets.

(Addition due to the questions in the comment section: planets don’t usually twinkle because they are closer and therefore bigger — they are disks of light instead of faraway points of light. The larger disks of light usually aren’t distorted; however if you are looking through especially turbulent areas of our atmosphere, and even sometimes when looking at planets that are low in the thicker parts of the atmosphere, they will twinkle. Phil Plait, the Bad Astronomer explains it very well on his website.)

This optical illusion is a big pain for astronomers and some very large telescopes such as those in Chile and Hawaii use special equipment and techniques to reduce the effects of the atmosphere.

One of most famous telescope of them all, the Hubble Space Telescope doesn’t get affected at all by our atmosphere as it is in space, making the light from stars crystal clear.

Twinkle, twinkle little star, now we know what you are (and why you are twinkling!)

January 16, 2012April 26, 2016 by Paul Scott Anderson

Citizen Scientist Project Finds Thousands of ‘Star Bubbles’

A prominent star bubble. Credit: NASA / The Milky Way Project / Zooniverse

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Remember when you were a kid and blowing bubbles was such great fun? Well, stars kind of do that too. The “bubbles” are partial or complete rings of dust and gas that occur around young stars in active star-forming regions, known as stellar nurseries. So far, over 5,000 bubbles have been found, but there are many more out there awaiting discovery. Now there is a project that you can take part in yourself, to help find more of these intriguing objects.

The Milky Way Project, part of Zooniverse, has been cataloguing these cosmic bubbles thanks to assistance from the public, or “citizen scientists” – anyone can help by examining images from the Spitzer Space Telescope, specifically the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) and the Multiband Imaging Photometer for Spitzer Galactic Plane Survey (MIPSGAL).

They have been seen before, but now the task is to find as many as possible in the newer, high-resolution images from Spitzer. A previous catalogue of star bubbles in 2007 listed 269 of them. Four other researchers had found about 600 of them in 2006. Now they are being found by the thousands. As of now, the new catalogue lists 5,106 bubbles, after looking at almost half a million images so far. As it turns out, humans are more skilled at identifying them in the images than a computer algorithm would be. People are better at pattern recognition and then making a judgment based on the data as to what actually is a bubble and what isn’t.

The bubbles form around hot, young massive stars where it is thought that the intense light being emitted causes a shock wave, blowing out a space, or bubble, in the surrounding gas and dust.

Eli Bressert, of the European Southern Observatory and Milky Way Project team member, stated that our galaxy “is basically like champagne, there are so many bubbles.” He adds, “We thought we were going to be able to answer a lot of questions, but it’s going to be bringing us way more questions than answers right now. This is really starting something new in astronomy that we haven’t been able to do.”

There are currently about 35,000 volunteers in the project; if you would like to take part, you can go to The Milky Way Project for more information.

January 16, 2012December 24, 2015 by Ray Sanders

Does Starburst Activity Starve Galaxies of Gas?

The Southern Cross, the Milky Way, and the Large Magellanic Cloud shine above the Atacama Large Millimeter/submillimeter Array (ALMA) as it observes on a clear night sky during its Early Science phase. Image credit: C. Padilla, NRAO/AUI/NSF

[/caption]Using the partially constructed ALMA observatory, a group of astronomers have found new evidence that helps explain how young, star-forming galaxies end up as ‘red and dead’ elliptical galaxies.

According to current galactic evolution theories, mergers of spiral galaxies are thought to explain why nearby elliptical galaxies have few young stars. Merging galaxies direct gas and dust into starburts, which are regions of rapid star formation, as well as into the central supermassive black hole at the core of the merging galaxies. As matter is piled onto a black hole, powerful jets erupt, and the region becomes a brightly shining quasar. Eventually the powerful jets emanating from the central black hole push away any potentially star-forming gas, which causes the starbursts to cease.

Astronomers have, until recently, been unable to detect enough mergers at the “jet” stage to make a definite link between the outflows and the end of starburst activity. During early science observations in 2011, ALMA became the first telescope to confirm almost two dozen galaxies at the critical, yet brief stage of galaxy evolution.

“Despite ALMA’s great sensitiviy to detecting starbursts, we saw nothing, or next to nothing – which is exactly what we hoped it would see,” said Dr. Carol Lonsdale (NRAO). Lonsdale presented the findings at the American Astronomical Society’s meeting in Austin, Texas on behalf of an international team of astronomers.

ALMA was set to look for the signature of dust warmed by star-forming regions. Half of Lonsdale’s two dozen galaxies were not visible in ALMA’s observations, and the other half very dim.

“ALMA’s results reveal to us that there is little-to-no starbursting going on in these young, active galaxies. The galaxy evolution model says this is thanks to their central black holes whose jets are starving them of star-forming gas,” Lonsdale said. “On its first run out of the gate, ALMA confirmed a critical phase in the timeline of galaxy evolution.”

HopkinsMerger — Infographic showing the sequence of events that model a typical galaxy becoming a so-called "red and dead" elliptical. Lonsdale and her team found a large population of galaxies, right in the middle of this sequence, between steps d and e. Image Credit: Hopkins, et al., NOAO/AURA/NSF.

After the star-forming gas is blown away, merging galaxies no longer form new stars. Once the massive, bright, blue, and short-lived stars die out, the redder, longer-lived, lower mass stars begin to dominate the population, leading to a gas-starved galaxy taking on a redder hue. To support the gas-starvation theory, astronomers needed to observe the process at work, specifically in merging galaxies with high power jets where quasars can be found.

Lonsdale added, “The missing phase had to be among quasars that could be seen brightly in infrared and radio wavelengths — mergers young enough to have their cores still swaddled in infrared-bright dust, but old enough that their black holes were well fed and producing jets observable in the radio.”

The team’s hunt for the specific type of quasars began with NASA’s Wide-field Infrared Survey Explorer (WISE) spacecraft. The WISE data consists of millions of objects in its all-sky survey of the Universe. Lonsdale led WISE’s quasar survey team that picked out the brightest, reddest objects this infrared telescope had mapped.

ALMAQSOs — Selected images from among the twenty-three quasars observed with ALMA so far in its hunt for candidate starving galaxies. Image Credit: C. Lonsdale, NRAO/AUI/NSF; ALMA (NRAO/ESO/NAOJ)

Lonsdale and her team compared the WISE data against the NRAO’s VLA Sky Survey of 1.8 million radio objects. The team then used results common to both sets of data to determine the best targets for their starburst search with ALMA. Since ALMA uses longer infrared wavelengths than WISE, Lonsdale’s team was able to make the distinction between dust warmed by starburst activity and dust heated by material falling onto the central black hole.

There are 26 more WISE quasars for ALMA to survey before Lonsdale and her team publish their results. In the meantime, Lonsdale and her team will observe these galaxies with the newly re-named Karl G. Jansky Very Large Array (VLA).

“ALMA revealed to us this rare stage of galaxy starvation, and now we want to use the VLA to focus on delineating the outflows that robbed these galaxies of their fuel,” Lonsdale said. “Together, the two most sensitive radio telescope arrays in the world will help us truly understand the fate of spiral galaxies like our own Milky Way.”

If you’d like to learn more about the Atacama Large Millimeter/Submillimeter Array (ALMA), visit: https://almascience.nrao.edu/about-alma/alma-site

Source: NRAO Press Release

January 15, 2012December 24, 2015 by Jon Voisey

“Proplyd-like” Objects Discovered in Cygnus OB2

Hubble image of a Proplyd-like object in Cygnus OB2. Credit: Z. Levay and L. Frattare, STScI

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The well known Orion Nebula is perhaps the most well known star forming regions in the sky. The four massive stars known as the trapezium illuminate the massive cloud of gas and dust busily forming into new stars providing astronomers a stunning vista to explore stellar formation and young systems. In the region are numerous “protoplanetary disks” or proplyds for short which are regions of dense gas around a newly formed star. Such disks are common around young stars and have recently been discovered in an even more massive, but less well known star forming region within our own galaxy: Cygnus OB2.

Ten times more massive than its more famous counterpart in Orion, Cygnus OB2 is a star forming region that is a portion of a larger collection of gas known as Cygnus X. The OB2 region is notable because, like the Orion nebula, it contains several exceptionally massive stars including OB2-12 which is one of the most massive and luminous stars within our own galaxy. In total the region has more than 65 O class stars, the most massive category in astronomers classification system. Yet for as bright as these stars are, Cygnus OB2 is not a popular target for amateur astronomers due to its position behind a dark obscuring cloud which blocks the majority of visible light.

But like many objects obscured in this manner, infrared and radio telescopes have been used to pierce the veil and study the region. The new study, led by Nicholas Wright at the Harvard-Smithsonian Center for Astrophysics, combines infrared and visual observations from the Hubble Space telescope. The observations revealed 10 objects similar in appearance to the Orion proplyds. The objects had long tails being blown away from the central mass due to the strong stellar winds from the central cluster similar to how proplyds in Orion point away from the trapezium. On the closer end, the objects were brightly ionized.

Yet despite the similarities, the objects may not be true proplyds. Instead, they may be regions known as “evaporating gaseous globules” or EGGs for short. The key difference between the two is whether or not a star has formed. EGGs are overdense regions within a larger nebula. Their size and density makes them resistant to the ionization and stripping that blows away the rest of the nebula. Because the interior regions are shielded from these dispersive forces, the center may collapse to form a star which is the requirement for a proplyd. So which are these?

In general, the newly discovered objects are far larger than those typically found in Orion. While Orion proplyds are nearly symmetric across an axis directed towards the central cluster, the OB2 objects have twisted tails with complex shapes. The objects are 18-113 thousand AU (1 AU = the distance between the Earth and Sun = 93 million miles = 150 million km) across making them significantly larger than the Orion proplyds and even larger than the largest known proplyds in NGC 6303.

Yet as different as they are, the current theoretical understanding of how proplyds work doesn’t put them beyond the plausible range. In particular, the size for a true proplyd is limited by how much stripping it feels from the central stars. Since these objects are further away from OB2-12 and the other massive stars than the Orion proplyds are from the trapezium, they should feel less dispersive forces and should be able to grow as large as is seen. Attempting to pierce the thick dust the objects contain and discover if central stars were present, the team examined the objects in the infrared and radio. Of the ten objects, seven had strong candidates central stellar sources.

Still, the stark differences make conclusively identifying the objects as either EGGs or proplyds difficult. Instead, the authors suggest that these objects may be the first discovery of an inbetween stage: old, highly evolved EGGs which have nearly formed stars making them more akin to young proplyds. If further evidence supports this, this finding would help fill in the scant observational details surrounding stellar formation. This would allow astronomers to more thoroughly test theories which are also tied to the understanding of how planetary systems form.