Posted on by Steve Nerlich

Astronomy Without A Telescope – Orphan Supernovae?

Supernova G292.0+1.8. Like most supernovae it detonated within a host galaxy - in fact ours. Credit: Chandra.

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For some years now astronomers have been scratching their heads over the appearance of supernovae that detonate out in the middle of nowhere – rather than within a host galaxy.

Various hypotheses have been proposed, notably that they might be hypervelocity stars – which are stars flung out of their host galaxy due to an unfortunate coincidence of gravitational interactions. It’s thought that such interactions may accelerate those stars up to a velocity of more than 100 kilometers a second – that is, more than the escape velocity of your average galaxy.

But Zinn et al suggest a more mundane suggestion for their particular orphan supernovae of interest, which is SN 2009z. They propose that it is in a galaxy, it’s just a galaxy that is very difficult to see.

They propose the supernova actually detonated within a low surface brightness galaxy, N271. From the images they have produced, this seems a reasonable claim – it’s just that low surface brightness galaxies (or LSBs) aren’t meant to have supernovae.

Left frame: Sloan Digital Sky Survey image showing the location of the Type IIB supernovae SN 2009z. Right frame: Close-up of the rectangular area taken by the New Technology Telescope (ESO), showing the location of SN 2009z at the cross marks. It seems closely associated with the small galaxy N271, even though such a galaxy is not usually thought capable of supporting massive star formation. Credit: Zinn et al.

Since galaxies can appear as extended objects, rather than as point-like stars, we refer to them as having ‘surface brightness’ – which can vary across the object’s apparent surface. LSB’s are generally isolated field galaxies, rather than being grouped in amongst dense galaxy clusters. They are most often dwarf galaxies as well, but at least one spiral LSB has been identified.

The dimness of LSB galaxies is suggestive of them having almost no active star formation – either being too old, with no free hydrogen remaining for new star formation – or just not dense enough for much star formation to ever have taken off.

But here you have supernova SN 2009z that was most likely was contained within LSB galaxy N271. And SN 2009z was a Type II supernova – a massive and short-lived star that underwent core collapse. Indeed, it was a Type IIb with only a small shell of hydrogen when it detonated. Type IIb supernovae are probably massive stars which lose most, but not all, of their hydrogen shell through having it stripped off by a companion star in a binary system.

This all seems quite unusual behaviour for a galaxy that does not support active star formation. Zinn et al propose that LSB galaxies must go through short bursts of active star formation followed by long quiescent phases of almost no activity. This then suggests that the progenitor star of supernova SN 2009z was formed in the previous starburst period, before N271 quietened down again.

Of course, none of this need suggest that hypervelocity stars don’t exist – indeed several have been discovered since the first confirmed finding in 2005. All those known are associated with the Milky Way, since finding a single isolated hypervelocity star ejected by a distant galaxy is probably beyond the detection of our current technology – unless of course they go supernovae.

But given what we know so far:
• a hypervelocity star arises from a binary system’s unfortunate interaction with a galaxy’s central supermassive black hole;
• one binary member is captured, the other flung violently outwards at escape velocity.
• but, massive stars that go supernovae only have a main sequence life span of the order of millions of years;
• so, even at more than 100 kilometers a second, it’s unlikely that any are going to make it across the many light years distance from the center of a galaxy to its outer boundary before they detonate.

Putting all this together… orphan supernovae? Busted (well, unless we find one anyway).

Further reading: Zinn et al. Supernovae without host galaxies? The low surface brightness host of SN 2009Z.

Posted on by Tammy Plotner

Keck Observatory Locates Two Clouds Of Pristine Gas From The Beginning of Time

Credit: Simulation by Ceverino, Dekel & Primack

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Is there any place in space which hasn’t been affected by time? The answer is yes. Thanks to some very awesome research, the W. M. Keck Observatory and a team of scientists have recently located two clumps of primordial gas which may very well have had its origin within minutes of the Big Bang.

How do we know these gas clouds are so special? In this case, they are simply too disseminated to enable stellar birth and contain no heavy metals which would support it. These diaphanous regions are pure hydrogen and helium… along with a heavier isotope, deuterium. This combination could mean the two billion year old regions are pure – never involved in the star-forming process. An exciting discovery? You bet. The clouds could have possibly survived in an unchanged state – giving us a look at what may have occurred at the dawn of time.

“Despite decades of effort to find anything metal-free in the universe, Nature has previously set a limit to enrichment at no less than one-thousandth that found in the Sun,” said astronomer J. Xavier Prochaska of the University of California Observatories-Lick Observatory, U.C. Santa Cruz. “These clouds are at least 10 times lower than that limit and are the most pristine gas discovered in our universe.”

Prochaska is part of the Keck team and has coauthored a paper reporting on the discovery with Michele Fumagalli of the U.C. Santa Cruz and John O’Meara of Saint Michael’s College in Vermont. “We’ve searched carefully for oxygen, carbon, nitrogen and silicon – the things that are found on Earth and the Sun in abundance,” Fumagalli said. “We don’t find a trace of anything other than hydrogen and deuterium.”

According to the Keck Observatory news release exactly how they can detect dark, cold, diffuse gas about 12 billion light-years away is a story in itself.

“In this case we actually have to do a bit of a trick,” Prochaska explained. “We study the gas in silhouette.” A more distant quasar provides the light for this. The quasar light shines though the gas and the elements in the gas absorb very specific wavelengths of light, which can only be found by splitting the light into very detailed spectra to reveal the dark lines of missing light.

In other words, said Fumagalli, “All of the analysis is on the light we didn’t get.” The clouds absorb only a small fraction of the quasar light that makes it to Earth. “But the signatures of hydrogen absorption are obvious, so there’s no doubt there’s a lot of gas there.”

While some folks might not get excited over the location of immaculate gases, astronomers think differently. This revelation supports their theories of what may have occurred within moments after the Big Bang and what formed at the time of nucleosynthesis. It’s a look back at when hydrogen, helium, lithium and boron originated.

The two pristine gas clouds found by astronomers could sit in one of the filamentary regions visible around galaxies in this image, which are from computer simulations. Credit: Simulation by Ceverino, Dekel & Primack

“That theory has been very well tested at Keck as regards to hydrogen and its isotope deuterium,” said O’Meara. “One of the conundrums of that previous work, however, is that the gas also showed at least trace amounts of oxygen and carbon. The clouds that we have discovered are the first to match the full predictions of BBN.”

What’s more, Keck’s two 10-meter optical/infrared telescopes have shown us what the early universe may have been like. This is the very first time that science has been able to peer into regions where no metals have influenced the environment and no stars have formed.

“What excites me about this discovery is that there is an almost a range of 1,000,000 in the metallicity in gases at that time in the universe,” said Fumagalli. In other words, there were places like our Solar system – where metals are very abundant – and there were also places very unlike today, where metals were still virtually non-existent and the gases were unchanged since almost the beginning of time.”

Original Story Source: Keck Observatory News Release. For Further Reading: Detection of Pristine Gas Two Billion Years After the Big Bang.

Posted on by Jon Voisey

Rare Pallasite Meteorite Found in Missouri

Dr. Randy Korotev at Washington University with the Conception Junction meteorite.
Dr. Randy Korotev at Washington University with the Conception Junction meteorite.

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Meteorite hunter Karl Aston finds meteorites not by digging in the ground, but by placing ads in local newspapers. He asked people who found unusual rocks to contact him. Most responses were bum leads, but in 2009 Aston heard from a farmer in the northwestern Missouri of Conception Junction, who found something interesting: An unusually heavy stone buried in a hillside. The overall size was similar to that of a basketball and had a mass of 17 kilograms (37 pounds). Its rusty exterior hid its true nature. When the farmer had sawed off one end, olive-green crystals embedded in a shining metal shone forth. It was one of the rarest types of meteorites, a pallasite, of which only 61 samples are currently known. Recently, scientists at Washington University in St. Louis have gotten involved in an attempt to discover the meteorite’s history.

Pallasites and other meteorites are relics of the formation of the solar system. The most commonly accepted story for their formation is that they represent a boundary region inside larger asteroids where the heat from formation melted the iron and nickel metal which sunk to the core. The lighter crystals would float, and near this transition, there would be some mixing which, when broken apart due to later impacts, would form the pallasites. These asteroids formed in the asteroid belt between Mars and Jupiter and similar layers would likely be found in larger asteroids still present as well as in planets like the Earth. An alternative theory is that the materials formed independently and were mixed more recently due to large impacts.

The rusting fusion crust on the outside of the Conception Junction meteorite disguises it as just another rock, but one glimpse of the interior gives the game away. The olive-green crystals set in lustrous metal are unique to pallasites. Image credit: Dave Gheesling
The rusting fusion crust on the outside of the Conception Junction meteorite disguises it as just another rock, but one glimpse of the interior gives the game away. The olive-green crystals set in lustrous metal are unique to pallasites. Image credit: Dave Gheesling

Within the United States, 20 pallasite meteorites have been discovered. The majority of them belong to a single family of “main group” pallasites due to a similar chemical composition of their olivine crystals. When compared to other samples, the Conception Junction meteorite was unique. Because of this, the sample was given a unique designation this past August, named after the location of discovery. Before the Meteoritical Society recognizes a designation, it is required that a museum or other institutional collection houses a “type specimen” which will make the material available for scholarly research. As such a portion of the sample will be housed at UCLA where the chemical analysis on the metal was performed (the olivine was examined at Washington University).

The rarity of pallasite meteorites makes them uncommonly valuable. Some slices of the Conception Junction meteorite are still available for sale or trade, but don’t expect it to be an impulse buy. While more common stony meteorites sell for a few dollars per gram, pallasite meteorites sell for a few hundred dollars per gram. The overall price is also determined by the condition (some are unstable in Earth’s atmosphere) and whether or not it has a unique history. Meteorites for which the fall was observed are especially prized.

Wondering if the discovered meteorite was part of a larger body, Aston and other meteorite collectors including Robert Ward and Dave Gheesling conducted an extensive search of the region. They looked for 16 months in concentric circles centered on the original discovery location, but did not find any other specimens.

Posted on by Ray Sanders

Was a Fifth Giant Planet Expelled from Our Solar System?

Artist’s impression of a fifth giant planet being ejected from the solar system. Image credit: Southwest Research Institute

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Earth’s place in the “Goldilocks” zone of our solar system may be the result of the expulsion of a fifth giant planet from our solar system during its first 600 million years, according to a recent journal publication.

“We have all sorts of clues about the early evolution of the solar system,” said author Dr. David Nesvorny of the Southwest Research Institute. “They come from the analysis of the trans-Neptunian population of small bodies known as the Kuiper Belt, and from the lunar cratering record.”

Nesvorny and his team used the clues they had to build computer simulations of the early solar system and test their theories. What resulted was an early solar system model that has quite a different configuration than today, and a jumbling of planets that may have given Earth the “preferred” spot for life to evolve.


Researchers interpret the clues as evidence that the orbits of Jupiter, Saturn, Uranus and Neptune were affected by a dynamical instability when our solar system was only about half a billion years old. This instability is believed to have helped increase the distance between the giant planets, along with scattering smaller bodies. The scattering of small bodies pushed objects both inward, and outward with some objects ending up in the Kuiper Belt and others impacting the terrestrial planets and the Moon. Jupiter is believed to have scattered objects outward as it moved in towards the sun.

One problem with this interpretation is that slow changes to Jupiter’s orbit would most likely add too much momentum to the orbits of the terrestrial planets. The additional momentum would have possibly caused a collision of Earth with Venus or Mars.

“Colleagues suggested a clever way around this problem,” said Nesvorny. “They proposed that Jupiter’s orbit quickly changed when Jupiter scattered off of Uranus or Neptune during the dynamical instability in the outer solar system.”

Basically if Jupiter’s early migration “jumps,” the orbital coupling between the terrestrial planets and Jupiter is weaker, and less harmful to the inner solar system.

Animation showing the evolution of the planetary system from 20 million years before the ejection to 30 million years after. Five initial planets are shown by red circles, small bodies are in green.
After the fifth planet is ejected, the remaining four planets stabilize after a while, and looks like the outer solar system in the end, with giant planets at 5, 10, 20 and 30 astronomical units.
Click image to view animation. Image Credit: Southwest Research Institute

Nesvorny and his team performed thousands of computer simulations that attempted to model the early solar system in an effort to test the “jumping-Jupiter” theory. Nesvorny found that Jupiter did in fact jump due to gravitational interactions from Uranus or Neptune, but when Jupiter jumped, either Uranus or Neptune were expelled from the solar system. “Something was clearly wrong,” he said.

Based on his early results, Nesvorny added a fifth giant planet, similar to Uranus or Neptune to his simulations. Once he ran the reconfigured simulations, everything fell into place. The simulation showed the fifth planet ejected from the solar system by Jupiter, with four giant planets remaining, and the inner, terrestrial planets untouched.

Nesvorny concluded with, “The possibility that the solar system had more than four giant planets initially, and ejected some, appears to be conceivable in view of the recent discovery of a large number of free-floating planets in interstellar space, indicating the planet ejection process could be a common occurrence.”

If you’d like to read Nesvorny’s full paper, you can access it at: http://arxiv.org/pdf/1109.2949v1

Source: Southwest Research Institute Press Release

Posted on by Ken Kremer

Russians Race against Time to Save Ambitious Phobos-Grunt Mars Probe from Earthly Demise

Russian graphic shows the planned Earth departure trajectory (at right) and two engine burns that failed to ignite from the Fregat upper stage following the launch of the Phobos-Grunt spacecraft from Baikonur Cosmodrome on Nov. 9 at 00:16am Moscow time. Illustration at left shows Phobos-Grunt spacecraft folded for flight inside the payload fairing. Credit: Roscosmos.

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Teams of Russian engineers are in a race against time to save the ambitious and unprecedented Phobos-Grunt sample return mission from crashing back to Earth following the post launch failure of the upper stage rocket firings essential to propel the probe onward to destination Mars and scooping up dirt and dust from the tiny moon Phobos.

Roscomos, the Russian Federal Space Agency says they have perhaps two weeks to salvage the spacecraft – now stuck in Earth orbit – before its batteries run out and its orbit would naturally decay leading to an ignominious and uncontrollable reentry and earthly demise. Vladimir Popovkin, head of Roscosmos Chief had initially indicated a survival time limited to only 2 days in a briefing to Russian media.

“I give them a good chance — better than even — of recovering the mission and making the Mars insertion burn in a day or two, said James Oberg, a renowned expert on Russian and US spaceflight in commentary to Universe Today.

But Oberg also told me that having such problems so early in the mission was not a good sign. It all depends on whether the root cause is related to a simple software patch or serious hardware difficulties.

Following yesterday’s eerie midnight blastoff of Phobos-Grunt at 00:16 a.m. Moscow time atop an upgraded Zenit- 2SB booster and the apparently flawless performance of the first and second stages, the situation turned decidedly negative some 5 hours later when the pre-planned ignition burns of the Fregat upper stage failed to ignite twice.

Blastoff of Phobos-Grunt spacecraft atop Zenit-2 rocket from Baikonur Cosmodrome on Nov. 9. Credit: Roscosmos

The 13,000 kg Phobos-Grunt (which means Phobos-Soil) spacecraft was to embark on an 11 month interplanetary cruise and arrive in the vicinity of Mars around October 2012, along with a piggybacked mini-satellite from China named Yinghuo-1, the nation’s first ever probe to orbit the Red Planet, and the Phobos-LIFE experiment from the Planetary Society.

“It has been a tough night for us because we could not detect the spacecraft [after the separation],” Vladimir Popovkin said according to the Ria Novosti Russian news agency. “Now we know its coordinates and we found out that the [probe’s] engine failed to start.”

“It is a complex trajectory, and the on-board computers could have simply failed to send a “switch on” command to the engine,” Popovkin added.

Fortunately, the engine ignition malfunction was one of the anticipated failure scenarios and a corrective action plan already exists for it – but only if it can be implemented to save the $163 million mission and Russian hopes to revive their long dormant interplanetary forays.

“But it’s an old old superstition that when leaving your house for a long voyage, if you trip on the door step, you better just lay down your suitcases and go back inside,” Oberg said.

“Seriously, on a mission so complex and innovative as this one is, with so much stuff that has to be done RIGHT the first time they’ve ever tried it, having this kind of error — even if it’s only a coding mishap — right at the start, is NOT a good omen about the quality of work on preparing the later steps,” Oberg warned.

The goal of the complicated and first of its-kind 3 year round trip mission is to deploy a lander to the surface of Phobos, grab up to 200 grams of pristine regolith and rocks, and then take off and sail back to Earth with the precious samples for analysis by the most scientifically advanced instruments available to humankind. Watch the detailed mission animation in my article here.

Russia’s historic Phobos-Grunt sample return mission to Mars and Phobos will retrieve 200 grams of soil from the surface of Martian moon Phobos and fly the samples back to Earth by August 2014. Credit: Roscosmos

Another serious problem was a lengthy gap in tracking coverage and thus two way communications with the spacecraft which minimized and seriously delayed Russian controller’s ability to diagnose and correct the malfunction.

Roscosmos stated today that after two communications sessions all necessary parameters of the spacecrafts motion have been determined and they hoped to regain contact sometime Wednesday afternoon through a ground station at Baikonur and upload new software to orient the vehicle and commands for an engine firing at some point soon. Luckily the hydrazine filled propellant tank had not been jettisoned – or all would be lost.

It appears that the earliest day the Fregat engines can be fired is sometime Thursday. The Fregat would also journey all the way to Mars and conduct the critical braking maneuver to insert Phobos-Grunt and Yinghuo-1 into separate Mars orbits.

The engine ignition failure has left Phobos-Grunt stuck in an elliptical orbit ranging from about 207 by 347 kilometers and inclined 51 degrees. The engine firings would have placed the ship into a higher altitude elliptical orbit of 250 by 4150 km and then cruising to Mars.

The Russianspaceweb website reported that “the editor of this web site received a message from the director of Moscow-based Space Research Institute, IKI, Lev Zeleny, informing that tracking facilities of the US military provided significant help in establishing exact orbital parameters of the Phobos-Grunt spacecraft. This data was to be used during the previous night to send commands to the spacecraft as it was passing within range of ground control stations. Zeleny reassured that the mission team still had had “few days for reprogramming before the end of the Mars accessibility window for 2011.”

Alexey Kuznetsov, Head of the Roskosmos Press Office told me previously that, “The Phobos-Grunt launch window extends until November 25.” So theoretically, there is still some time to propel Phobos-Grunt to Mars but there are also many unknowns.

Labeled Schematic of Phobos-Grunt and Yinghou-1 (YH-1) orbiter. Main propulsion is the Fregat upper stage that failed to ignite twice following flawless liftoff on Nov. 9. Credit: Roskosmos

Further details will be reported as they emerge.

Meanwhile, NASA’s car sized Curiosity Mars Science Laboratory (MSL) Rover is posied atop an Atlas V rocket at her Florida launch pad awaiting a Nov. 25 liftoff.

Read Ken’s continuing features about Phobos-Grunt here:
Russia’s Bold Sample Return Mission to Mars and Phobos Blasts Off
Russian Mars Moon Sample Probe Poised to Soar atop Upgraded Rocket – VideoAwesome Action Animation Depicts Russia’s Bold Robot Retriever to Mars moon Phobos
Phobos-Grunt and Yinghuo-1 Encapsulated for Voyage to Mars and Phobos
Phobos and Jupiter Conjunction in 3 D and Amazing Animation – Blastoff to Martian Moon near
Russia Fuels Phobos-Grunt and sets Mars Launch for November 9
Phobos-Grunt and Yinghou-1 Arrive at Baikonur Launch Site to tight Mars Deadline
Phobos-Grunt: The Mission Poster
Daring Russian Sample Return mission to Martian Moon Phobos aims for November Liftoff

Posted on by Ken Kremer

Russia’s Bold Sample Return Mission to Mars and Phobos Blasts Off

Russia’s historic Phobos-Grunt sample return mission to Mars and Phobos blasts off atop a Zenit-2SB rocket from the Baikonur Cosmodrome, Kazakhstan on November 9, 2011 at 00:16 a.m. Moscow time (Nov. 8, 3:16 p.m. EST) from Launch Pad 45. Credit: Roscosmos/Spaceflight Now

Russia has successfully launched the Phobos-Grunt sample return mission to Mars aiming to return a soil sample from Phobos, the first time in history such a bold and complicated feat has been attempted.

The ambitious mission lifted off just past midnight at 00:16 Moscow time atop an upgraded version of the Zenit-2 rocket from the Baikonur Cosmodrome in Kazakhstan.

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Phobos-Grunt is now in a parking orbit around Earth and further burns are required by the modified Fregat upper stage by 8:20 p.m. tonight to put the probe of course for Earth departure and an interplanetary cruise to the Red Planet. Watch for updates later.

The liftoff of the $163 million robotic spacecraft marks Russia’s first attempt to conduct an interplanetary mission in some 15 years since the launch failure of the Mars 96 probe back in 1996. Phobos-Grunt translates as Phobos-Soil.

Russia’s historic Phobos-Grunt sample return mission to Mars and Phobos liftoff off on top of a Zenit-2SB rocket from the Baikonur Cosmodrome, Kazakhstan on November 9, 2011 at 00:16 a.m. Moscow time (Nov. 8, 3:16 p.m. EST) from Launch Pad 45. Credit: Roscosmos

The mission goal is to deploy a lander to Phobos and bring back up to 200 grams of pristine regolith and rocks from the surface of Phobos.

Also along for the ride is China’s first Mars mission named Yinghuo-1 (which means means Firefly-1) which will be jettisoned into Mars orbit as Phobos-Grunt inserts into a different orbit about Mars. Additionally, the Planetary Society’s Phobos LIFE biomodule is also on board.

The 12,000 kg Phobos-Grunt spacecraft should arrive in the vicinity of Mars around October 2012 after an 11 month interplanetary cruise. Following several months of orbital science investigations of Mars and its two moons and searching for a safe landing site, Phobos-Grunt will attempt history’s first ever touchdown on Phobos in February 2013. It will conduct a comprehensive analysis of Phobos surface and gather up to 200 grams of soil and rocks with a pair of robotic arms and a scoop device.

The samples will be transferred by a long tube onto the return vehicle mounted atop the lander. By March 2013 the ascent vehicle will take off for the trip back back to Earth.

Phobos-Grunt is equipped with a 50 kg array of 20 sophisticated science instruments including lasers, spectrometers, cameras and a microscope provided by an international team of scientists and science institutions from across Europe and Asia.

The entire voyage will last just under 3 years with the capsule plummeting through the Earth’s atmosphere in August 2014. These would represent the first macroscopic samples returned from another body in the solar system since Russia’s Luna 24 returned soil from the Moon back in 1976.

Posted on by Nancy Atkinson

Hoping to See Asteroid 2005 YU55? There’s an App for That!

Starmap is an astronomy/planetarium app for the iPhone and iPad. A companion app, called Spacemap is an extended orrery that lets you view the phases, motions, and positions of items in the Universe all from your iPad. If you’re hoping to track down Asteroid 2005 YU55 as it comes close to Earth on Nov. 8, you might want to check out both Starmap and Starmap. You can see this asteroid in both apps, but Spacemap is the only application available in the iTunes store that displays 2005 YU55’s orbit in 3D animation.

UPDATE: The contest is now closed and the winners have been notified.

Want to win a copy of either Starmap or Spacemap? Universe Today has a two copies of each to give away to the first four readers to answer this question correctly: What year was the last time an asteroid as big as 2005 YU55 passed by Earth?

Answer in the comment section, and indicate which app you’d like. We have two of each to give away. First four commenters to answer correctly wins. Make sure your contact info on Disqus is correct, as that is you’ll be contacted.

Continue reading “Hoping to See Asteroid 2005 YU55? There’s an App for That!”

Posted on by Tammy Plotner

Andromeda Dwarf Galaxies Help Unravel The Mysteries Of Dark Matter

The circled cluster of stars is the dwarf galaxy Andromeda 29, which University of Michigan astronomers have discovered. The bright star within the circle is a foreground star within our own Milky Way galaxy. This image was obtained with the Gemini Multi-Object Spectrograph at the Gemini North telescope in Hawaii. Credit: Gemini Observstory/AURA/Eric Bell

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Yep. It’s that time of year again. Time to enjoy the Andromeda Galaxy at almost every observing opportunity. But now, rather than just look at the nearest spiral to the Milky Way and sneaking a peak at satellites M32 and M110, we can think about something more when we peer M31’s way. There are two newly discovered dwarf galaxies that appear to be companions of Andromeda!

Eric Bell, an associate professor in astronomy, and Colin Slater, an astronomy Ph.D. student, found Andromeda 28 and Andromeda 29 by utilizing the Sloan Digital Sky Survey and a recently developed star counting technique. To back up their observations, the team employed data from the Gemini North Telescope in Hawaii. Located at 1.1 million and 600,000 light-years respectively, Andromeda XXVIII and Andromeda XXIX have the distinction of being the two furthest satellite galaxies ever detected away from the host – M31. Can they be spotted with amateur equipment? Not hardly. This pair comes in about 100,000 fainter than Andromeda itself and can barely be discerned with some of the world’s largest telescopes. They’re so faint, they haven’t even been classified yet.

“With presently available imaging we are unable to determine whether there is ongoing or recent star formation, which prevents us from classifying it as a dwarf spheroidal or a dwarf irregular.” explains Bell.

The dwarf galaxy Andromeda 29, which University of Michigan astronomers have discovered, is clustered toward the middle of this image, obtained with the Gemini North telescope in Hawaii. Credit: Gemini Observstory/AURA/Eric Bell

In their work – published in a recent edition of the edition of the Astrophysical Journal Letters – the team of Bell and Slater explains how they were searching for dwarf galaxies around Andromeda to help them understand how physical matter relates to theoretical dark matter. While we can’t see it, hear it, touch it or smell it, we know it’s there because of its gravitational influence. And when it comes to gravity, many astronomers are convinced that dark matter plays a role in organizing galaxy structure.

“These faint, dwarf, relatively nearby galaxies are a real battleground in trying to understand how dark matter acts at small scales,” Bell said. “The stakes are high.”

Right now, current consensus has all galaxies embedded in surrounding dark matter… and each “bed” of dark matter should have a galaxy. Considering the volume of the Universe, these predictions are pretty much spot on – if we take only large galaxies into account.

“But it seems to break down when we get to smaller galaxies,” Slater said. “The models predict far more dark matter halos than we observe galaxies. We don’t know if it’s because we’re not seeing all of the galaxies or because our predictions are wrong.”

“The exciting answer,” Bell said, “would be that there just aren’t that many dark matter halos.” Bell said. “This is part of the grand effort to test that paradigm.”

Right or wrong… pondering dark matter and dwarf galaxies while observing Andromeda will add a whole new dimension to your observations!

For Further Reading: Andromeda XXVIII: A Dwarf Galaxy more than 350 kpc from Andromeda and Andromeda XXIX: A New Dwarf Spheroidal Galaxy 200 kpc from Andromeda.

Posted on by Jon Voisey

Forget Exoplanets. Let’s Talk Exomoons

An artist impression of an exomoon orbiting an exoplanet, could the exoplanet's wobble help astronomers? (Andy McLatchie)

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It wasn’t that long ago that astronomers began discovering the first planets around other stars. But as the field of exoplanetary astronomy explodes, astronomers have begun looking to the future and considering the possibility of detecting moons around these planets. Surprisingly, the potential for doing so may not be that far off.

Before exploring how we might detect satellites of distant planets, astronomers must first attempt to get an understanding of what they may be looking for. Fortunately, this question ties in well with the rapidly developing understanding of how solar systems form.

In general, there are three mechanisms by which planets may obtain satellites. The simplest is for them to simply form together from a single accretion disk. Another is that a massive impact may knock material off of a planet which forms into a satellite as astronomers believe happened with our own Moon. Some estimates have indicated that such impacts should be frequent and as many as 1 in 12 Earth like planets may have formed moons in this way. Lastly, a satellite may be a captured asteroid or comet as is likely for many of the moons of Jupiter and Saturn.

Each of these cases produces a different range of masses. Captured bodies are likely to be the smallest and therefor are unlikely to be detectable in the near future. Impact generated moons are expected to only be able to form bodies with 4% of the total mass of the planet and as such, are rather limited as well. The largest moons are thought to form in the disks around forming Jupiter like planets. These are the most likely to be detectable.

The first method by which astronomers may detect such moons is by the changes they would make in the wobble of the star that has been used to detect many extrasolar planets to date. Astronomers have already studied how a pair of binary stars may affect a binary star system may have on a third star it orbits. If the binary star is swapped out for a planet and a moon it turns out that the easiest systems to detect are massive moons that are distant from the planet, but close to the parent star. However, except in extreme cases, the amount of wobble that the pair could induce in the star is so small that it would be swamped by the convective motion of the star’s surface, making detection through this method nearly impossible.

Astronomers have begun detecting large numbers of exoplanets by transits, where the planet causes minor eclipses. Could astronomers also detect the presence of moons this way? In this case, the limit on detection would again be based on the size of the moon. Currently, the Kepler satellite is expected to detect planets similar in mass to Earth. If moons exist around a super-Jovian planet that are also similar in size to Earth, they too should be detected. However, forming moons this large is difficult. The largest moon in the solar system in Ganymede which is 40% of the diameter of Earth, putting it modestly below current detection thresholds, but potentially in reach of future exoplanet missions.

However, direct detection of the eclipses caused by transits isn’t the only way transits could be used to discover exomoons. In the past few years, astronomers have begun using the wobble of other planets on the ones they had already discovered to infer the existence of other planets in the system in the same way the gravitational tug of Neptune on Uranus allowed astronomers to predict Neptune’s existence before it was discovered. A sufficiently massive moon could cause detectable variations in when the transit of the planet would begin and end. Astronomers have already used this technique to place limits on the mass of potential moons around exoplanets HD 209458 and OGLE-TR-113b at 3 and 7 Earth masses respectively.

The first discovered exoplanet was discovered around a pulsar. The tug of this planet caused variation of the regular pulsation of the pulsar’s beat. Pulsars often beat hundreds to thousands of times per second and as such, are extremely sensitive indicators of the presence of planets. The pulsar PSR B1257+12 is known to harbor one planet that is a mere 0.04% the mass of Earth, which is well below the mass threshold of many moons. As such, variations in these systems, caused by moons would be potentially detectable with current technology. Astronomers have already used it to search for moons around the planet orbiting PSR B1620-26 and ruled out moons more than 12% the mass of Jupiter within half an Astronomical Unit (the distance between the Earth and Sun or 93 million miles) of the planet.

The last method by which astronomers have detected planets that could potentially be used for exomoons is direct observation. Since direct imaging of exoplanets has only become realized in the past few years, this option is likely still a ways off, but future missions like the Terrestrial Planet Finder Coronagraph may put it into the realm of possibility. Even if the moon is not fully resolved, the offset of the center of the dot of the pair may be detectable with current instruments.

Overall, if the explosion of knowledge on planetary systems continues, astronomers should be capable of detecting exomoons within the near future. The possibility already exists for some cases, like pulsar planets, but due to their rarity, the statistical likelihood of finding a planet with a sufficiently large moon is low. But as equipment continues to improve, making detection thresholds lower for various methods, the first exomoons should come into view. Undoubtedly, the first ones will be large. This will beg the question of what sorts of surfaces and potentially atmospheres they may have. In turn, this would inspire more questions about what life may exist.

Source:
The Detectability of Moons of Extra-Solar Planets – Karen M. Lewis

Posted on by Tammy Plotner

Hubble Telescope Directly Observes Quasar Accretion Disc Surrounding Black Hole

A team of scientists has used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc — a brightly glowing disc of matter that is slowly being sucked into its galaxy’s central black hole. Their study makes use of a novel technique that uses gravitational lensing to give an immense boost to the power of the telescope. The incredible precision of the method has allowed astronomers to directly measure the disc’s size and plot the temperature across different parts of the disc. Image credit: NASA, ESA, J.A. Munoz (University of Valencia)

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Thanks to the magic of the NASA/ESA Hubble Space Telescope, a team of international astronomers have made an incredible observation – a quasar accretion disc surrounding a black hole. By employing a technique known as gravitation lensing, the researchers have been able to get an accurate size measurement and spectral data. While you might not think this exciting at first, know that this type of observation is akin to spotting individual grains of sand on the Moon!

Of course, we know we can’t see a black hole – but we’ve learned a lot about them with time. One of their properties is a bright, visible phenomenon called a quasar. These glowing discs of matter are engaged in orbit around the black hole, much like a coil on an electric stove. As energy is applied, the “coil” heats up and unleashes bright radiation.

“A quasar accretion disc has a typical size of a few light-days, or around 100 billion kilometres across, but they lie billions of light-years away. This means their apparent size when viewed from Earth is so small that we will probably never have a telescope powerful enough to see their structure directly,” explains Jose Munoz, the lead scientist in this study.

Because of the diminutive size of the quasar, most of our understanding of how they work has been based on theory… but great minds have found a way to directly observe their effects. By employing the gravity of stars in an intervening galaxy like a scanning microscope, astronomers have been able to observe the quasar’s light as the stars move. While most of these types of features would be too small to see, the gravitation lensing effect ramps up the strength of the quasar’s light and allows study of the spectra as it cruises across the accretion disc.

This diagram shows how Hubble is able to observe a quasar, a glowing disc of matter around a distant black hole, even though the black hole would ordinarily be too far away to see clearly. Credit: NASA and ESA

By observing a group of gravitationally lensed quasars, the team was able to paint a vivid color portrait of the activity. They were able to pick out small changes between single images and spectral shifts over a period of time. What causes these kaleidoscopic variances? For the most part, it’s the different properties in the gases and dust of the lensing galaxies. Because they travel at different angles to the quasar’s light, scientists were even able to distinguish extinction laws at work.

But there was something special about one of the quasars. Says the Hubble Team, “There were clear signs that stars in the intervening galaxy were passing through the path of the light from the quasar. Just as the gravitational effect due to the whole intervening galaxy can bend and amplify the quasar’s light, so can that of the stars within the intervening galaxy subtly bend and amplify the light from different parts of the accretion disc as they pass through the path of the quasar’s light.”

By documenting these color changes, the team could build a profile of the accretion disc. Unlike our Earthly electric stove coil which glows red as it heats up, the accretion disc of a black hole turns blue as it gets closer to the event horizon. By measuring the blue hue, the team was able to measure the disc diameter and the various tints gave them an indicator of distances from its center. In this case, they found that the disc is between four and eleven light-days across (approximately 100 to 300 billion kilometres). Of course, these are only rough estimates, but considering just how far away we’re looking at such a small object gives these types of observations great potential for future studies… and even improvements on accuracy.

“This result is very relevant because it implies we are now able to obtain observational data on the structure of these systems, rather than relying on theory alone,” says Munoz. “Quasars’ physical properties are not yet well understood. This new ability to obtain observational measurements is therefore opening a new window to help understand the nature of these objects.”

Original Story Source: ESA/Hubble News Release. For Further Reading: A Study of Gravitational Lens Chromaticity With the Hubble Space Telescope.