Jon Voisey, Author at Universe Today

October 9, 2011December 24, 2015 by Jon Voisey

Abuse From Other Universes – A Second Opinion

Concentric circles interpreted as bruises from collisions with alternate universes. Image Credit: Feeney et al.

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At the end of last year, there was a flurry of activity from astronomers Gurzadyan and Penrose that considered the evidence of alternate universes or the existence of a universe prior to the Big Bang and suggested that such evidence may be imprinted on the cosmic microwave background as bruises of concentric circles. Quickly, this was followed by an announcement claiming to find just such circles. Of course, with an announcement this big, the statistical significance would need to be confirmed. A recent paper in the October issue of the Astrophysical Journal provides a second opinion.

The review was conducted by Amir Hajian at the Canadian Institute for Theoretical Astrophysics. To conduct the study, Hajian selected a large number of circles, similar to the ones reported in the previous studies and asked what the probability was that, randomly, the “edge” of the circles would contain hot-spots, similar to the ones predicted. These were then compared to the bruises reported by the other teams by examining their “variance” which is how much the points on the perimeter were spread around the average temperature.

Hajian notes that, with the resolution considered it would be possible to consider some 5 million circles. The results of his comparison demonstrated that it would be expected that some 0.3% of those should have features similar to the ones reported previously. With so many possibilities, this would imply that some 15,000 potential circles could be flagged as candidates for these cosmic bruises. Even the “best” candidate proposed in the Gurzadyan and Penrose study should still exist statistically.

As such, Hajian concludes that the features Gurzadyan and Penrose reported were not statistically anomalous. Hajian does not comment directly on Feeney et al.’s detection, but given theirs were constructed in a similar manner, it should be expected that they are similarly statistically insignificant. It would appear that if the fingerprints of other universes are embedded in the sky, they have been lost in the noise.

October 7, 2011December 24, 2015 by Jon Voisey

What Would Earth Look Like from a Distant Star?

The "pale blue dot" of Earth captured by Voyager 1 in Feb. 1990 (NASA/JPL)

As the number of discovered extrasolar planets grows, astronomers begin looking at the next step: finding rocky Earth-like planets. In addition, astronomers would ideally like to block out the parent star and detect some of the reflected glow from the planet’s atmosphere in an attempt to characterize the chemical makeup. But what would an “Earth-like” planet’s reflected light look like? To answer this, a new paper explores what Earth should have looked like at various points in our planet’s history.

Currently, astronomers have a good understanding on how our planet reflects light. Even before satellites were launched that could observe this directly, we could see the reflected light from our home on the moon, an effect known as “Earthshine”. The amount of light reflected depends on what’s on the surface.

The paper considers five different types of reflecting materials. Water and vegetation tend to be strong absorbers of light at visible and ultraviolet wavelengths whereas ice and deserts are highly reflective. The amount of cloud cover, which also reflects a good deal of light, is the fifth.

With the modern Earth, our planet currently reflects about 32% of all incoming light. This changes by a few percent depending on the season, depending mostly on the amount of cloud cover.

This new study also analyzes what the amount of reflected light should have been for Earth, known as its albedo, during four other historical periods: the Late Cretaceous (90 million years ago), the Late Triassic (230 My ago), the Mississippian (340 My ago), and the Late Cambrian (500 My ago).

Using simulations based on the various surface features, the team from the Instituto de Astrofísica de Canarias owned by Spain, the team reconstructed the expected amount of cloud cover for these various epochs to consider their contributions to the overall albedo.

In general, the historical periods had strikingly similar amounts of reflectiveness due to “similar ocean-land-vegitation distribution” as well as similar distributions of continents between hemispheres and most deserts in low latitudes. The exception to this, was the Late Cambrian. While the average was only slightly higher, this period varied depending on which portion of the Earth was viewed.

At that time, the original supercontinent, Pangea was in the process of breaking up. They were still clustered and almost exclusively in the southern hemisphere. The sea levels were also significantly higher meaning a larger portion of land was submerged, covered by the non-reflective water. Lastly, most of the life was still concentrated in the oceans. Since it had not yet advanced to land, it is expected that the surface was mostly rocky desert terrain which would have high reflectivity. During the times when the breaking up supercontinent was facing an observer, the albedo would jump to as much as 37% only to sink to 32% when it rotated from view.

The team suggests that such a variation may allow astronomers to determine the rotation rates of planets in the future. In an ideal situation, it may even give clues to the geographical arrangement of continents.

October 3, 2011December 24, 2015 by Jon Voisey

High Precision Study of Exoplanet WASP 10b

SuperWasp Cameras. Credit: SuperWASP project & David Anderson

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Originally discovered by the Wide Angle Search for exoPlanets (WASP) survey in 2008, the eclipsing exoplanet WASP 10b has been reluctant to allow its properties to be pinned down. While its mass has been pinned down by two independent groups to right around 3 times the mass of Jupiter, the radius and thus, the overall density which gives hints at the composition, has been harder to determine. Groups have also reported oddities in the timing of the eclipses that may hint at the presence of another planets whose gravitational tug is changing the orbit of 10b. A new study attempts to answer these questions with high precision observations from the Spanish 2.2 meter Calar Alto Observatory.

The new study, led by astronomers from Nicolaus Copernicus University in Poland, is the first of WASP 10b to take into account the effects of star spots. Since the host star is a K-dwarf such spots should be common. When such spots are present, the planet can eclipse them as well, making the overall brightness increase temporarily. This apparent change in the brightness of the star makes small changes in how astronomers would determine the overall brightness of the star. This brightness is used to determine the properties of the star, such as its radius, which also factor into determining the radius of the planet. As such, these spots should be taken into account for the most accurate understanding possible.

The team observed four transits of the planet in late 2010. In that time, star spots were present for three of the four transits. With the spots subtracted out, the team agreed with previous estimates of mass, but found an even lower value for the radius than either of the previous studies. Their value was only a few percent wider than Jupiter despite being three times as massive. While this doesn’t make WASP 10b most dense planet known, it does rank among the top contenders.

These results have implications for how planets may form in general. Since WASP 10 is estimated to be a relatively young star, it would imply that the major planet formed a rocky core early on and that it wasn’t deposited later through collisions. The team estimates that it would require a total mass for the core of roughly 300-400 times the mass of Earth.

When the team added their new data to previous studies of the system, they found that the timing of the transits have continued to change and these changes could not be the product of other effects, such as star spots on the limb of the star altering the shape of the light curve. As such, they note that “this finding supports a scenario in which the second planet perturbs the orbital motion of WASP 10b.”

September 26, 2011December 24, 2015 by Jon Voisey

A Magnified Supernova

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Supernovae are among astronomers most important tools for exploring the history of the universe. Their frequency allows us to examine how active star formation was, how heavy elements have developed, and the distance to galaxies across vast distances. Yet even these titanic explosions are only so bright, and there’s an effective limit on how far we can detect them with the current generation of telescopes. However, this limit can be extended with a little help from gravity.

One of the consequences of Einstein’s theory of general relativity is that massive objects can distort space, allowing them to act as a lens. While first postulated in 1924, and proposed for galaxies by Fritz Zwicky in 1937, the effect wasn’t observed until 1979 when a distant quasar, an energetic core of a distant galaxy, was split in two by the gravitational disturbances of an intervening cluster of galaxies.

While lensing can distort images, it also provides the possibility that it may magnify a distant object, increasing the amount of light we receive. This would allow astronomers to probe even more distant regions with supernovae as their tool. But in doing so, astronomers must look for these events in a different manner than most supernova searches. These searches are generally limited to the visible portion of the spectrum, the portion we see with our eyes, but due to the expansion of the universe, the light from these objects is stretched into the near-infrared portion of the spectrum where few surveys to search for supernovae exist.

But one team, led by Rahman Amanullah at Stockholm University in Sweden, has conducted a survey using the Very Large Telescope array in Chile, to search for supernovae lensed by the massive galaxy cluster Abell 1689. This cluster is well known as a source of gravitationally lensed objects, making visible some galaxies that formed shortly after the Big Bang.

In 2009, the team discovered one supernova that was magnified by this cluster that originated 5-6 billion lightyears away. In a new paper, the team reveals details about an even more distant supernova, nearly 10 billion lightyears distant. This event was magnified by a factor of 4 from the effects of the foreground cluster. From the distribution of energy in different portions of the spectrum, the team concludes that the supernova was an implosion of a massive star leading to a core-collapse type of supernova. The distance of this event puts it among the most distant supernovae yet observed. Others at this distance have required extensive time using the Hubble telescope or other large telescopes.

September 26, 2011December 24, 2015 by Jon Voisey

Homeless Supernovae

NGC 1058. Image credit: Bob Ferguson and Richard Desruisseau/Adam Block/NOAO/AURA/NSF

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In a post earlier this month, we looked at a team of astronomers searching for stars that were on ejected from their birthplaces in clusters. These stars could receive the needed kick from a gravitational swing by the core of the cluster to achieve a velocity of a few tens of km/sec. But a similar mechanism can function in the cores of galaxies giving stars a speed of roughly 1,000 km/sec, enough to leave their parent galaxies. a new study asks whether we have ever witnessed any of these stellar cast offs explode as supernovae.

The team, led by Peter-Christian Zinn at Ruhr University in Bochum, Germany, searched through roughly 6,000 supernovae listed in the Sternbarg Astronomical Institute Supernova Catalog, for which no host galaxy was apparent, yet weren’t too distant from any known galaxy. The latter criteria was added because, even at the high velocities, stars still couldn’t get too far before they reached the end of their fuses. The team imposed a rough inner cut off of around 10 kiloparsecs (roughly 1/3 of the width of the disk of the Milky Way). They expected stars should be at least this distance from the cores of the parent galaxy.

The initial list contained five candidate stars, dating back as far as 1969. The first step the team used to determine if the supernova was truly in a galaxy or not, was to take long exposure images of the immediate area, to draw out potential low surface brightness hosts. The team also used archival data in the far ultraviolet as well as the x-ray spectrum to determine whether or not the nearby galaxies from which the supernovae could potentially be ejected had an extended disk, invisible in the visible portion of the spectrum that would have allowed the progenitor star to form in the outskirts of the galaxy. These wavelengths are tracers of ongoing star formation which are sites in which high mass stars that would lead to core-collapse supernovae, would likely be found.

The oldest candidate, SN 1969L, was located near the flocculent spiral NGC 1058. While the deep exposures did not show a host galaxy, the x-ray and UV images both showed some extended structure of the parent galaxy at the distance of the supernova. This led to the conclusion that this supernova, while far removed from its host galaxy, was still gravitationally tied to it.

With the second candidate, SN 1970L, the team again failed to find any faint host galaxy. However, the supernova was situated between two galaxies, NGC 2968 and a faint elliptical, NGC 2970. A 1994 study had revealed a faint bridge of matter connecting the two, implying that they had had an interaction in the past. This interaction would likely have pulled off gas and stars, of which SN 1970L could have been one.

SN 1997C was the third candidate and also lacked a discernible host galaxy, even with long exposures. This one also did not have an indication of an extended disk of which the supernova could have been part. Given the characteristics of the supernova, the team estimated that it had an original mass of 15 times that of the Sun. Given its projected distance and the lifetime of such stars, the team noted that this would correspond to a velocity of some 3,000 km/sec, which is several times the speed of the highest confirmed hypervelocity star. As such, the team expected that this star would have to be ejected in a similar manner to SN 1970L, using an interaction between galaxies. Given that the host galaxy is known to be one in a small cluster and the disk shows some signs of perturbation, they suggested this was likely.

The fourth candidate, SN 2005nc, the team selected because there was no nearby galaxy they could assign as a possible parent. They suggested this was due to an extremely distant host galaxy, too faint to resolve with previous studies. The basis for this assertion was that the supernova came with a gamma ray burst that indicated an origin some 5-6 billion light years distant. Due to the associated GRB, the Hubble telescope swung in to take a look. These archival pictures failed to reveal any objects that could readily be identified as host galaxies leaving the team to presume the host was simply too far away to resolve.

The last candidate was SN 2006bx located near the galaxy UGC 5434. This supernova did not appear to be in a faint background galaxy and did not have hints of being formed in an extended disk. The estimated velocity from the projected distance was ~850 km/sec which placed it in the realm of plausible speeds for stars ejected by gravitational assists from the supermassive black hole at the center of galaxies.

September 22, 2011December 24, 2015 by Jon Voisey

Globular Clusters on a Plane

Smaller satellite galaxies caught by a spiral galaxy are distorted into elongated structures consisting of stars, which are known as tidal streams, as shown in this artist's impression. Credit: Jon Lomberg

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Globular clusters are generally some of the oldest structures in our galaxy. Many of the most famous ones formed around the same time as our galaxy, some 13 billion years ago. However, some are distinctly younger. While many classification schemes are used, one breaks globular clusters into three groups: an old halo group which includes the oldest of the clusters, those in the disk and bulge of the galaxy which tend to have higher metallicity, and a younger population of halo clusters. The latter of these provides a bit of a problem since the galaxy should have settled into a disk by the time they formed, depriving them of the necessary materials to form in the first place. But a new study suggests a solution that’s not of this galaxy.

The new study looked at the distribution of these younger clusters around our Milky Way. Of the three classifications for globular clusters discussed, the young halo clusters are scattered well beyond the range of the other populations. The young halo extends to as much as 120 kiloparsecs (400 thousand light years) while the old halo clusters tend to lie within 30 kiloparsecs (100 thousand light years). Additionally, the young clusters don’t appear to be rotating with the disk of the galaxy whereas the old halo slowly orbits in the same direction as the disk.

In looking more carefully at the positions of these satellites, the team, led by Stefan Keller at the Australian National University, found that the younger population tends to lie in a wide plane that is tilted from the rotational axis of our galaxy by a mere 8°.

This plane is strikingly similar to another recognized grouping of objects: Many of the known dwarf galaxies lie in a nearly identical plane, known as the Plane of Satellites (PoS). This finding suggests that this population of globular clusters is a relic of cannibalized galaxies. Even more interesting is that, while these objects are younger than the distinctly “old” population, there is still a large variation in their ages. This implies that this plane wasn’t created by the accretion of one, or even a few minor galaxies, but a consistent feeding of small galaxies onto the Milky Way for much of the history of the universe, and all from the same direction. Studies of the distribution of satellites around our nearest major neighbor, M31, the Andromeda galaxy, has turned up a similar preferred plane, tilted some 59° from its disk.

One explanation for this is that this is a preferred direction that traces invisible filaments of dark matter. While dark matter distributions are difficult to predict, models haven’t accounted for such strong filamentary structure on such small scales. Rather, in the neighborhood of our galaxy, the overall distribution is described as an oblate spheroid. One of the reasons astronomers believe our own dark matter halo is so nicely shaped is the way it is affecting the Sagittarius dwarf galaxy which is slowly being accreted onto our own. If the dark matter were more wispy, it should be stretched out in different manners.

Another possibility the authors consider is that the objects were created in a preferred plane “from the break up of a large progenitor at early times”. In other words, the filament could be a fossil of larger structure before our galaxy formed along which these dwarf galaxies formed and from which these galaxies could have been slowly accreting over the history of the galaxy.

September 15, 2011December 24, 2015 by Jon Voisey

Help! My Stars are Leaking!

A fast-moving star, Alpha Camelopardalis, creates a stunning bow shock in this new image from WISE. Credit: NASA/JPL-Caltech/WISE Team

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Star clusters are wonderful test beds for theories of stellar formation and evolution. One of the key roles they play is to help astronomers understand the distribution of stellar masses as stars form (in other words, how many high mass stars versus intermediate and low mass stars), known as the Initial Mass Function (IMF). One of the problems is that this is constantly evolving away from the initial distribution as stars die or are ejected from the cluster. As such, understanding these mechanisms is essential for astronomers looking to backtrack from the current population to the IMF.

To assist in this goal, astronomers led by Vasilii Gvaramadze at the University of Bonn in Germany are engaged in a study to search young clusters for stars in the process of being ejected.

In the first of two studies released by the team so far, they studied the cluster associated with the famous Eagle Nebula. This nebula is well known due to the famous “Pillars of Creation” image taken by the aging Hubble Space Telescope which shows towers of dense gas currently undergoing star formation.

Two main methods exist for discovering stars on the lam from their birthplace. The first is to examine stars individually and analyze their motion in the plane of the sky (proper motion) along with their motion towards or away from us (radial velocity) to determine if a given star has sufficient velocity to escape the cluster. While this method can be reliable, it suffers because the clusters are so far away, even though the stars could be moving at hundreds of kilometers per second, it takes long periods of time to detect it.

Instead, the astronomers in these studies search for runaway stars by the effects they have on the local environment. Since young clusters contain large amounts of gas and dust, stars plowing through it will create bow shocks, similar to those a boat makes in the ocean. Taking advantage of this, the team searched the Eagle Nebula cluster for signs of bow shocks from these stars. Searching images from several studies, the team found three such bow shocks. The same method was used in a second study, this time analyzing a lesser known cluster and nebula in Scorpius, NGC 6357. This survey turned up seven bow shocks of stars escaping the region.

In both studies, the team analyzed the spectral types of the stars which would indicate their mass. Simulations of nebulae suggested that the majority of ejected stars are given their initial kick as they have a close pass to the center of a cluster where the density is the highest. Studies of clusters have shown that their centers are often dominated by massive O and B spectral type stars which would mean that such stars would be preferentially ejected. These two studies have helped to confirm that prediction as all of the stars discovered to have bow shocks were massive stars in this range.

While this method is able to find runaway stars, the authors note that it is an incomplete survey. Some stars may have sufficient velocity to escape, but still fall under the local sound speed in the nebula which would prevent them from creating a bow shock. As such, calculations have predicted that roughly 20% of escaping stars should create detectable bow shocks.

Understanding this mechanism is important because it is expected to play the dominant role in the evolution of the mass distribution of clusters early in their life. An alternative method of ejection involves stars in a binary orbit. If one star becomes a supernova, the sudden mass loss suddenly decreases the gravitational force holding the second star in orbit, allowing it to fly away. However, this method requires that a cluster at least be old enough for stars to have evolved to the point they explode as supernova, delaying this mechanism’s importance until at least that point and allowing the gravitational sling-shot effects to dominate early on.

September 5, 2011April 26, 2016 by Jon Voisey

Where’s the Debris for Transiting Planets?

For many exoplanet systems that have been discovered by the radial velocity method, astronomers have found excess emission in the infrared portion of the spectrum. This has generally been interpreted as remnants of a disk or collection of objects similar to our own Kupier belt, a ring of icy bodies beyond the orbit of Pluto. But as Kepler and other exoplanet finding missions rake in the candidates though transits of the parent star, astronomers began noticing something unusual: None of the exoplanet systems discovered through this method were known to have debris disks. Was this an odd selection effect, perhaps induced by the fact that transiting planets often orbit close to their parent stars, making them more likely to pass along the line of sight which could in turn, betray different formation scenarios? Or were astronomers simply not looking hard enough? A recent paper by astronomers at the Astrophysikalisches Institut in Germany attempts to answer that question.

In order to do so, the team compared the (at the time) 93 known transiting exoplanets to stars for which archival data was available through infrared missions such has IRAS, ISO, AKARI, and WISE. The team then searched the data looking for a previously unrecognized bump in the emission in the infrared. Many of the stars they searched were faint, due to distance, so most of the IR telescopes did not have images with sufficient depth to draw much in the way of conclusions. Between IRAS, ISO, Spitzer, and AKARI, the team was only able to examine three stars, and all of those came from Spitzer observations.

The most plentiful return came from the WISE telescope which had 53 entries that overlapped with known transiting systems, one of which was excluded due to image defects. From these 52 candidates, the team found four that may have contained excess emission. To follow up, the team added observations from other observatories that lied in the near infrared (the 2MASS survey) and the visual portion of the spectrum. This allowed them to build a more complete picture of the brightness of the stars at various wavelengths which would make the excess stand out even more. While all four systems deviated from an ideal blackbody in the portion of the spectrum expected for a debris disk, only two of them, TrES-2, and XO-5, did so in a manner that did so in a statistically significant manner.

While this study shows that debris disks are possible around transiting stars, it was only able to confirm their presence in two stars out of 52, or just under 4% of their sample. But how does that compare to systems discovered by other methods? One of the studies cited in the paper used a similar method of comparing archival data from IR observatories to known exoplanet system discovered by other methods in 2009. In this study, the team found debris disks around 10 of the 150 planet-bearing stars, which is roughly 7%. Due to the low return rate on both of these studies, the inherent uncertainty puts these two figures within a plausible range of one another, but certainly, more studies will be in order in the future. They will help astronomers determine just what difference exists, if any, as well as giving more insight into how planetary system form and evolve.

August 22, 2011December 24, 2015 by Jon Voisey

Five Awesome Things You (Probably) Didn’t Know Asteroseismology Could Do

The variations in brightness can be interpreted as vibrations, or oscillations within the stars, using a technique called asteroseismology. The oscillations reveal information about the internal structure of the stars, in much the same way that seismologists use earthquakes to probe the Earth's interior. Credit: Kepler Astroseismology team.

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Asteroseismology is a relatively new field in astronomy. This branch uses sound waves in stars to explore their nature in the same way seismologists on Earth have used waves induced by tectonic activity to probe the interior of our planet. These waves aren’t heard directly, but as they strike the surface they can cause it to undulate, shifting the spectral lines this way and that, or compress the outer layers causing them to brighten and fade which can be detected with photometry. By studying these variations, astronomers have begun peering into stars. This much is generally known, but some of the specific tricks aren’t often brought up when discussing the topic. So here’s five things you can do with asteroseismology you may not have known about!

1. Determine the Age of a Star

From high school science you should know sound will travel through a medium at a characteristic speed for a given temperature and pressure. This information tells you something about the chemical composition of the star. This is a fantastic thing since astronomers can then check that against predictions made by stellar models. But astronomers can also take that one step further. Since the core of a star slowly converts hydrogen to helium over its lifetime, that composition will change. How much it has changed from its original composition towards the point where there’s no longer enough hydrogen to support fusion, tells you how far through the main sequence lifetime a star is. Since we know the age of the solar system very well from meteorites, astronomers have calibrated this technique and begun using it on other stars like α Centauri. Spectroscopically, this star is expected to be nearly identical to the Sun; it has very similar spectral type and chemical composition. Yet a 2005 study using this technique pinned α Cen as 6.7 ± 0.5 billion years which is about one and a half billion years older than the Sun. Obviously, this still has a rather large uncertainty to it (nearly 10%), but the technique is still new and will certainly be refined in the future.

And if that wasn’t cool enough by itself, astronomers are now beginning to use this technique on stars with known planets to get a better understanding of the planets! This can be important in many cases since planets will initially glow more brightly in younger systems since they still retain heat from their formation and this amount of extra light could confuse astronomers on just how might light is being reflected leading to inaccurate estimates of other properties like size or reflectivity.

2. Determine Internal Rotation

Cover of a Book on the Solar Tachocline showing abrupt transition discovered by helioseismology

We already know that stars rotation is a bit funny. They rotate faster at their equator than at their poles, a phenomenon known as differential rotation. But stars are also expected to have differences in rotation as you get deeper. For stars like the Sun, this effect is related to a difference in energy transport mechanisms: radiative, where energy is conducted by a flow of photons in the deep interior, to convective, where energy is carried by bulk flow of matter, creating the boiling motion we see on the surface. At this boundary, the physical parameters of the system change and the material will flow differentially. This boundary is known as the tachocline. Within the Sun, we’ve known it’s there, but using asteroseismology (which, when used on the Sun is known as helioseismology), astronomers actually pinned it down. It’s 72% the way out from the core.

3. Find Planets

Until very recently, the most reliable way to find planets has been to look for the spectroscopic wiggle as the planets tug the star around. This technique sounds very straightforward, and it can be, unless the star has a lot of wiggle of its own due to the effects that make asteroseismology possible. Those effects can easily be much larger than those created by planets. So if you want to find planets lost in the forest of noise, you’d best understand the effects caused by the pulsating stellar surface. After astronomers cancelled out those effects on V391 Pegasi, they discovered a planet. And what a weird one it was. This planet is orbiting a sub-dwarf star, which is the helium core of a post-main sequence star which has ejected its hydrogen envelope. Of course, this occurs during the red giant phase when the star should have swollen up to engulf the gas giant planet in orbit. But apparently the planet survived, or somehow came along later.

4. Find Buried Sunspots

Turning to recent news, helioseismology recently found some sunspots. This wouldn’t be a big deal. Anyone with a properly filtered telescope can find them. Except these ones were buried some 60,000 km beneath the Sun’s surface. By using the seismic data, astronomers found an overdense region beneath the surface. This region was caused, just as sunspots are, by a tangle in the magnetic field keeping the material in place. As it rose to the surface, it became a sunspot. Here’s the vid:

5. Make “Music”

Because many of the events that create the soundwaves in stars are periodic, they are rhythmic in nature. This has prompted many explorations into using these naturally created beats to make music. A direct example is this one which simply assigns tones to the modes of pulsation. The site also notes that the beat created by one of the stars, has been used as a base for club music in Belgium. This has also been done for longer “symphonies” by Zoltan Kollath.

August 10, 2011December 24, 2015 by Jon Voisey

The Hidden Galaxy in the Zone of Avoidance

The Fornax dwarf galaxy is one of our Milky Way’s neighbouring dwarf galaxies and a good example of what an early dwarf galaxy might have been like. This image was composed from data from the Digitized Sky Survey 2. Credit: ESO

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There are some places astronomers dare not tread. One of the prime places is beyond the disk of our own galaxy where the numerous stars and clouds of dust along the line of sight make observations messy to say the least. This obscured portion of the sky is known as the Zone of Avoidance. But despite the challenges, one team of astronomers has searched through it and found a previously undiscovered galaxy lurking not too far from our own.

To discover this galaxy, the team, lead by graduate student Travis McIntyre at the University of New Mexico, used the gigantic Arecibo radio telescope. This telescope is adept at finding emission at the 21 centimeter wavelength emitted by cool, atomic hydrogen. This long wavelength is relatively immune to the diminishing effects of gas and dust within our galaxy.

After the initial discovery, the team followed up with further observation using the Expanded Very Large Array, which also operates in the radio, as well as the 0.9 meter Southeastern Association for Research in Astronomy telescope, which is an optical telescope, in hopes of peering through some of the muck.

While the galaxy was easily recovered in the second radio search, and the optical images showed a faint clump, the centers of the two did not appear to line up. The visual and radio components seemed not to overlap almost at all. A portion of the reason for this is that the team was unable to image the faint galaxy out to its full extent before the contamination from our own galaxy overwhelmed the signal. As such, the two likely overlap more than is indicated by the study, but this would still indicate that the distribution of hydrogen gas within it is severely lopsided.

Another possibility is that the object detected isn’t really a galaxy at all and is a coincidence of an alignment between a high velocity cloud and an independent cluster of stars. However, such clouds of gas tend to travel in packs and no others are known in the area, making this possibility unlikely.

If the object is a galaxy, it is likely a blue dwarf galaxy with some 10 million solar masses. The team expects that, while the galaxy is relatively nearby, this galaxy is not likely to bea member of the local group because, were it that close, it would be unprecedentedly small. As such, they applied Hubble’s Law to give a rough distance of 22 million light years but caution that at such distances, there is a large velocity dispersion and this estimate may be unreliable.

Searching for galaxies like this one in the Zone of Avoidance are important to astronomers because the mass of such undiscovered galaxies may help to resolve the unexpected “discrepancy between the cosmic microwave background dipole and what is expected from gravitational acceleration imparted on the Local Group by matter in the local universe.”