Posted on by Nancy Atkinson

NASA Looks at Fission Reactors for Power on the Moon

Artist concept of a fission surface power system on the surface of the moon. Credit: NASA

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When astronauts return to the moon for long duration missions, they will need reliable sources of power. Solar energy will be plentiful for the 14 Earth-day- long lunar daytime, but what about the equally as long lunar night? NASA engineers are exploring the possibility of nuclear fission to provide the necessary power. If you’re having visions of a Three Mile Island nuclear reactor on the moon, put your fears to rest. A nuclear reactor used in space is much different than Earth-based systems, says Lee Mason of the NASA Glenn Research Center, who is the principal investigator for testing a fission powered system for the moon. There are no large concrete cooling towers, and the reactor is about the size of an office trash can. Of course, it won’t produce as much energy as the big reactors on Earth, but it should be more than adequate for the projected power needs of a lunar outpost.

“Our goal is to build a technology demonstration unit with all the major components of a fission surface power system and conduct non-nuclear, integrated system testing in a ground-based space simulation facility,” said Mason. “Our long-term goal is to demonstrate technical readiness early in the next decade, when NASA is expected to decide on the type of power system to be used on the lunar surface.”

A fission surface power system on the moon has the potential to generate a steady 40 kilowatts of electric power, enough for about eight houses on Earth. It works by splitting uranium atoms in a reactor to generate heat that then is converted into electric power. The fission surface power system can produce large amounts of power in harsh environments, like those on the surface of the moon or Mars, because it does not rely on sunlight. The primary components of fission surface power systems are a heat source, power conversion, heat rejection and power conditioning, and distribution.

Glenn recently contracted for the design and analysis of two different types of advanced power conversion units as an early step in the development of a full system-level technology demonstration. These power conversion units are necessary to process the heat produced by the nuclear reactor and efficiently convert it to electrical power.

Two different companies have designed concepts that can produce a total of 12 kilowatts of power. One uses piston engines and the other a high speed turbine coupled with a rotary alternator.

“Development and testing of the power conversion unit will be a key factor in demonstrating the readiness of fission surface power technology and provide NASA with viable and cost-effective options for nuclear power on the moon and Mars,” said Don Palac, manager of Glenn’s Fission Surface Power Project.

A contractor will be selected after a year of design and analysis. Testing of the non-nuclear system is expected to take place in 2012 or 2013 to verify the performance and safety of the systems and determine if these systems can easily be used on the moon, or even on Mars.

Source: NASA

Posted on by Tammy Plotner

Australian Telescope Leads the World In Astronomy Research

The AAT - Photograph courtesy of Chris McCowage

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While the Anglo-Australian Telescope is far from being the world’s largest, or even located in the world’s best observing site, it’s still the world’s most productive in terms of astronomy research. According to recently released productivity ratings, the number of scientific papers resulting from observations made with the AAOmega fibre-fed optical spectrograph, SPIRAL Integral Field Unit, IRIS2, University College London Echelle Spectrograph (UCLES), or Ultra High Resolution Facility (UHRF) made the AAT the number one ranked 4-metre-class telescope in the world for more than two years between 2001 and 2003. But what’s going on today is even more important…

When we think of research telescopes, some of the world’s top rated are the Hubble Space Telescope (located in Earth orbit), Keck (more than twice the AAT’s size) in Hawaii, the Very Large Telescope (VLT, which comprises four telescopes twice the size of the AAT) in Chile, the Sloan Digital Sky Survey and the 2MASS telescope. So where does that leave the humble Anglo-Australian? Try number five. “The AAT has a remarkable track record of scientific productivity and impact,” says Prof. Matthew Colless, Director of the Anglo-Australian Observatory. “This is an extraordinary achievement.”

When the Anglo-Australian Observatory opened for business in the early 1970’s, the 4 meter telescope was the standard by which all others were judged. Since that time, research telescope aperture has more than doubled and while the AAT can’t compete in some respects, it has advantages that give it an edge for research. While it isn’t Mauna Kea, Australia still offers up some of the best skies to study our Galaxy and other nearby galaxies and the ability to undertake long-term observations and programs that just won’t work with other observatories. Add to that some very unique instrumentation such as Echidna – a fibre positioner for FMOS, UKidna – A multi-fibre positioner for the UKST, OZPOZ – a fibre positioner for ESO and part of FLAMES, DAZLE – The Dark Age z (redshift) Lyman-alpha Explorer, MOMFOS – Multi-Object Multi-Fibre Optical Spectrograph, ODC – Optical Detector Controllers and AAOmega – next generation optical spectrograph for the AAT and you have a recipe for research. This explains why demand for the telescope remains strong, with 2.5 times as many applications for telescope time as can actually be handled. “The AAO believes that the AAT can maintain this high level of productivity and impact for another decade.” says Prof. Colless.

Over a period of time, the the AAO has produced some of the most inspiring astronomy images ever seen – those taken by David Malin. These are the most extraordinary wide-field astrophotographs made with professional telescopes anywhere and every effort has been made to capture the true colours of distant stars, galaxies and nebulae using innovative photographic techniques and CCD detectors. The images have detailed captions and the full NGC 2000.0 catalogue entry. Galaxy images also carry NASA/IPAC Extragalactic Database (NED) data links. They are a standard of astronomers everywhere. But, progress hasn’t stopped. The AAT’s prime focus has recently been upgraded to accommodate a new generation of highly sensitive CCD detectors. The first colour images made with the new facility are now available, currently only in digital form. Most of the photographic images have recently been digitally re-mastered from the original 3-colour separations. This has allowed the AAO to create new, high resolution versions of many existing images and some new pictures that could not be made photographically.

Just this year a “uniquely ambitious, far-sighted” project won an Australian and UK astronomy team the first Group Achievement Award from the UK’s Royal Astronomical Society. Led by Professor Matthew Colless (Anglo-Australian Observatory) in Australia and Professor John Peacock (University of Edinburgh) in the UK, the thirty-three-member team spent ten years mapping the distribution in space of 220,000 galaxies using the 3.9-m Anglo-Australian Telescope (AAT) in New South Wales — a project called the 2-degree Field Galaxy Redshift Survey (2dFGRS). “The scale of this project made it ground-breaking,” said Matthew Colless. “For the first time we were able to map the positions of a huge number of galaxies and see the subtle effects that reveal the different types of matter in the universe.”

What was needed was for the area of sky surveyed to be much bigger than, rather than the same size as, the “walls” and “strings” of galaxies being detected. Almost ten times larger than any previous survey, the 2dFGRS was the first study to meet this crucial condition. The survey measured patterns in the distribution of galaxies, on scales from 100 million to 1 billion light-years. Two wedge-shaped pieces of sky were surveyed, so when the galaxies within them were mapped out, the result looked like a bow-tie cut from a sponge: a network of voids and dense regions. The size of the 2dF Galaxy Redshift Survey was made possible only by technological advances developed at the Anglo-Australian Observatory (AAO). The 2dF spectrograph used robotic technology to place optical fibres onto the telescope’s focal plane, where each fibre could collect the light from a single galaxy. By using up to 400 optical fibres, this system allowed the light from up to 400 galaxies to be captured simultaneously.

And the AAT is ensuring that it doesn’t fall behind the times with future technological advancement either….

“We are currently investing $4 million in refurbishing the telescope to ensure that it can operate reliably and efficiently for another ten years, and more than $6 million in a major new instrument, the 400-fibre HERMES high-resolution Spectrograph,” says Prof. Colless. “The primary science drivers for HERMES are ‘Galactic archaeology’ surveys to uncover the formation history of the Milky Way,’ he adds. ‘Extragalactic surveys using the AAOmega instrument and galactic surveys using HERMES will be the flagship science carried out on the AAT over the next 5-10 years. AAOmega and HERMES, and other upgrades to existing instruments, will provide astronomers with powerful tools that will enable them to do competitive, high-impact research using the AAT throughout the coming decade.”

Original Source: SpaceInfo.com

Posted on by Fraser Cain

Announcing Asteroid 158092 Frasercain

Asteroid Frasercain

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Well, I’ve just been accepted into an elite club of people with astronomical objects named after them. And no, my Mom didn’t name a star after me. The asteroid hunting team of David Healy and Jeff Medkeff have collectively discovered 487 asteroids, and designated 62 of them. You might already recognize some of asteroid names: Philplait, Paulmyers, Rebeccawatson, and Derekcolanduno.

At the end of August I received an email from David Healy notifying me that I was a new member of the asteroid club.

Asteroid 158092 Frasercain was officially designated on August 21, 2008. You can see the full list of named asteroids here – scroll down to see Frasercain. And you can see its current position in the Solar System here.

Those of you who know Jeff Medkeff will know the sad part of this story. Jeff, aka “The Blue Collar Scientist”, passed away on August 3rd from complications with liver cancer – he was 39. I’ve got to be honest and tell you that I didn’t know Jeff. We clearly ran in similar circles, but it wasn’t until Phil, Pamela and other people in the space blogging community informed me of his death that I found and read through his blog; I really wish I’d found it earlier.

If you haven’t already, please visit the Blue Collar Scientist blog. And you can read a very moving blog entry fulfilling Jeff’s last request.

So to Jeff and David, thank you very much for this incredible honour – I promise this won’t go to my head… much.

Posted on by Nancy Atkinson

Test Your Astronomical Knowledge With This Week’s “WITU” Challenge

It’s Wednesday, so that means its time for another “Where In The Universe” (WITU) challenge to test your visual knowledge of the cosmos. This one might be relatively easy, but I’m feeling generous today. Guess what this image is, and give yourself extra points if you can guess which spacecraft is responsible for the image. As always, don’t peek below before you make your guess. Comments on how you did are welcome.

Ready? Go!

This is the Eskimo Nebula (NGC 2392), so named because it resembles a person’s head surrounded by a parka hood. But its also known as the Clownface Nebula. In 2000, the Hubble Space Telescope produced this image. NGC 2392 lies about 3000 light-years away and is visible with a small telescope, found in the constellation of Gemini.

The gas clouds in this nebula are unusual and complex, and aren’t fully understood. Its a planetary nebula, and the gas seen above composed the outer layers of a Sun-like star only 10,000 years ago. The inner filaments visible above are being ejected by strong wind of particles from the central star. The outer disk contains unusual light-year long orange filaments.

How’d you do?

Posted on by Nancy Atkinson

Star Endured Unique Explosion That Didn’t Destroy

Eta Carinae Credit: Gemini Observatory artwork by Lynette Cook

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There’s ‘smoked but didn’t inhale,’ ‘promised but didn’t deliver,’ and now there’s ‘exploded but didn’t destroy.’ Eta Carinae, the galaxy’s biggest, brightest and perhaps most studied star after the sun, appears to be driven by an entirely new type of stellar explosion that is fainter than a typical supernova and does not destroy the star. Astronomer Nathan Smith proposes that Eta Carinae’s historic 1843 explosion was, in fact, an outburst that produced a fast blast wave similar to, but less energetic than, a real supernova. This well-documented event in our own Milky Way Galaxy is probably related to a class of faint stellar explosions in other galaxies recognized in recent years by telescopes searching for extragalactic supernovae.

“There is a class of stellar explosions going off in other galaxies for which we still don’t know the cause, but Eta Carinae is the prototype,” said Smith, a UC Berkeley postdoctoral fellow.

Eta Carinae (η Car) is a massive, hot, variable star visible only from the Southern Hemisphere, and is located about 7,500 light years from Earth in a young region of star birth called the Carina Nebula. In 1843, observers saw Eta Car brighten immensely. Visible now is the resulting cloud of gas and dust, known as the Homunculus nebula, wafting away from the star. A faint shell of debris from an earlier explosion is also visible, probably dating from around 1,000 years ago.

But these shells of gas and dust are moving relatively slowly at 650 kilometers per second (1.5 million miles per hour) compared to the blast shell of a regular supernova.

Presumably blown off by the star’s fierce wind, the shells of gas and dust are moving slowly – at speeds of 650 kilometers per second (1.5 million miles per hour) or less – compared to the blast shell of a supernova. But new observations by Smith show filaments of gas moving five times faster than the debris from the Homonuculus, which would equal speeds of materials accelerated fast blast wave of a supernova explosion.

The fast speeds in this blast wave could roughly double earlier estimates of the energy released in the 1843 eruption of Eta Carinae, an event that Smith argues was not just a gentle surface eruption driven by the stellar wind, but an actual explosion deep in the star that sent debris hurtling into interstellar space. In fact, the fast-moving blast wave is now colliding with the slow-moving cloud from the 1,000-year-old eruption and generating X-rays that have been observed by the orbiting Chandra Observatory.

“These observations force us to modify our interpretation of what happened in the 1843 eruption,” he said. “Rather than a steady wind blowing off the outer layers, it seems to have been an explosion that started deep inside the star and blasted off its outer layers. It takes a new mechanism to cause explosions like this.”

If Smith’s interpretation is correct, supermassive stars like Eta Carinae may blow off large amounts of mass in periodic explosions as they approach the end of their lives before a final, cataclysmic supernova blows the star to smithereens and leaves behind a black hole.

“Looking at other galaxies, astronomers have seen stars like Eta Carinae that get brighter, but not quite as bright as a real supernova,” he said. “We don’t know what they are. It’s an enduring mystery as to what can brighten a star that much without destroying it completely.”

Source: EurekAlert

Posted on by Astronomy Cast

Podcast: The Strong and Weak Nuclear Forces

Nuclear reactor
Nuclear reactor

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After a quick Dragon*Con break, we’re back to our tour through the fundamental forces of the Universe. We’ve covered gravity and electromagnetism, and now we’re moving onto the strong and weak nuclear forces. We didn’t think they’d really need to be separate episodes, so we’re putting them together. And then we’ll cap the whole series with the quest for the theory of everything.

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

The Strong and Weak Nuclear Forces show notes.

Posted on by Fraser Cain

Large Hadron Collider Worst Case Scenario

The Large Hadron Collider (LHC). Credit: CERN

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I apologize that Universe Today has been a little slow over the last couple of days. That’s because my webserver is completely bogged down with Google searchers worried that the world is going to end thanks to the Large Hadron Collider.

Don’t worry, it’s not. In fact, the twin proton beams fired for the first time today. Since you’re reading this, the Universe wasn’t torn apart.

But let’s just say that the Large Hadron Collider does create a microscopic black hole? What then… are we doomed? Nope. Ethan Seigel over at Starts With a Bang has done the calculations to figure out how massive a black hole would be created, and how much of the Earth it would consume if it fell down into the planet. He also calculates how long it should last before evaporating away. There you go, you can use these calculations to help your panicked friends realize there’s no need to worry about microscopic black holes.

Check out Ethan’s post, I won’t give away his final numbers.

And in a strange twist of irony, Google has changed today’s logo to celebrate the Large Hadron Collider. At least, that’s what I’m seeing here in Canada.

Google's LHC logo
Google's LHC logo

Posted on by Nancy Atkinson

Blinding Gamma Ray Burst Was Directed at Earth

Artists depiction of GRB 080319B Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones

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On March 19, 2008 at 2:13 am EDT, NASA’s Swift satellite detected an explosion from the constellation Bootes, and sent an alert to ground-based telescopes. At the same moment, the Russian KONUS instrument on NASA’s Wind satellite and a robotic wide-field optical camera called “Pi of the Sky” in Chile captured the first visible light from this incredibly bright and powerful gamma ray burst. Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes. For a few moments, the GRB had a million times the luminosity of the entire Milky Way Galaxy. It briefly crested at a magnitude of 5.3 on the astronomical brightness scale. Incredibly, the dying star was 7.5 billion light-years away. Astronomers say the reason this gamma ray burst was so bright was that it was aimed almost directly at Earth.

Observations of the event, formally named GRB 080319B, are giving astronomers the most detailed portrait of a GRB ever recorded. “You have to have the satellites in orbit and the rapid response telescopes on Earth in order take complete advantage this rare kind of event,” said David Burrows, head of the Swift X-ray telescope team, at today’s press conference detailing the GRB.

Judith Racusin of Penn State University and a team of 92 coauthors report on observations across the spectrum that began 30 minutes before the explosion and followed its afterglow for months. The team concludes the burst’s extraordinary brightness arose from an unusual two component jet that shot material directly toward Earth at 99.99995 percent the speed of light.

Telescopes around the world already were studying the afterglow of another burst when GRB 080319B exploded just 10 degrees away.

Immediately after the blast, Swift’s UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded. Racusin initially thought something was wrong. Within minutes, however, as reports from other observers arrived, it was clear this was a special event. A head-on burst directed towards Earth only occurs by chance only about once a decade, so GRB 080319B is a rare catch.

Gamma-ray bursts are the universe’s most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star’s core collapses, it creates a black hole or neutron star that, through processes not fully understood, drive powerful gas jets outward. These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.


The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider. “A normal signature is different from what we saw in this burst,” said Racusin . “In this object, we see two signatures of jets with two different properties.”

“Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time,” says team member Stefano Covino. “We happened to view this monster down the barrel of the very narrow and energetic jet.”

These unique beacons of light were observed only 8 minutes after the trigger, and are the brightest bursts ever detected. Additional study of this event can also help provide more information on relativity and cosmology.

Burrows said if a similar event happened at our own galaxy, we would be in considerable trouble. “It’s been postulated that a nearby gamma ray burst directed at earth could affect our atmosphere, causing something like a nuclear winter. We are fortunate in that we don’t believe there are any stars in our galas that will produce a gamma ray burst.”

NASA, NASA News Audio

Posted on by Tammy Plotner

The Dragon Slayer – NGC 5985, NGC 5982, NGC 5981 by Ken Crawford

Draco Trio - By Ken Crawford

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There are wonderful tales which surround the circumpolar Draco constellation. According to Greek legend, Draco represents the dragon killed by Cadmus before founding the city of Thebes – or perhaps it represented the dragon which guarded the golden fleece and was eventually killed by Jason and his famous Argonauts. To the Romans, it was simply a creature killed by Minerva and tossed into the sky as stars to be remembered. The Egyptians called it Tawaret. But the most famous of all representations of Draco was one of the twelve labors that Hercules had to overcome. Many of us will never see the jewels that hide within the boundaries of this sprawling constellation, but thanks to the Herculean efforts of Ken Crawford – we can share in its mysteries…

To deep sky observers, the group of NGC 5985, NGC 5982 and NGC 5981 is commonly known as the “Draco Trio”. Two barred spirals at different angles and a face on elliptical all in the same field of view is a rare sight and makes for a beautiful celestial portrait. The beautiful spiral is NGC 5985. The proper designation for the elliptical galaxy is NGC 5982. The catalog number for the edge-on is NGC 5981. While these galaxies span huge amounts of light years apart, they share telescopic space at RA: 15h 38m 40s Dec: +59°21’22” as a center and share photons in the eyepiece at around 25 arc minutes. While the Draco group is far too small to be considered its own galaxy cluster and has never been classified as a compact group, oddly enough all three are around 100 million light years away from the Sol System.

I did mention there were mysteries here, didn’t I? Then let’s explore them…

Take a closer look at the grand spiral, NGC 5985. It’s a Seyfert. According to research done by Simões Lopes (et al) it may also harbor a wonderful black hole right in there with its active galactic nucleus. “This result demonstrates a strong correlation between the presence of circumnuclear dust and accretion onto the central, supermassive black hole in elliptical and lenticular galaxies. Current estimates suggest the dust settling or destruction time is on order of 108 yr, and therefore the presence of dust in ~50% of early-type galaxies requires frequent replenishment and similarly frequent fueling of their central supermassive black holes. The observed dust could be internally produced (via stellar winds) or externally accreted, although there are observational challenges for both of these scenarios. Our analysis also reveals that approximately one-third of the early-type galaxies without circumnuclear dust have nuclear stellar disks. These nuclear stellar disks may provide a preferred kinematic axis to externally accreted material, and this material may in turn form new stars in these disks. The observed incidence of nuclear stellar disks and circumnuclear dust suggests that episodic replenishment of nuclear stellar disks occurs and is approximately concurrent with the fueling of the central AGN.”

But that’s not all, because there’s a quasar there, too. According to a 2001 study done by one of my heroes – Halton Arp and David Russell; “The distribution on the sky of clusters of galaxies shows significant association with relatively nearby, large, active galaxies. The pattern is that of clusters paired equidistant across a central galaxy with the apparent magnitudes and redshifts of their constituent galaxies being closely matched. The clusters and the galaxies in them tend to be strong X-ray and radio emitters, and their redshifts occur at preferred redshift values. The central, low-redshift galaxies often show evidence of ejection in the direction of these higher redshift clusters. In all these respects the clusters resemble closely quasars which have been increasingly shown for the last 34 years to be similarly associated with active parent galaxies. New, especially significant pairings of quasars are presented here, which are, at the same time, associated with Abell clusters of galaxies. It is argued here that, empirically, the quasars are ejected from active galaxies. They evolve to lower redshift with time, forming stars, and fragmenting at the end of their development into clusters of low-luminosity galaxies. The cluster galaxies can be at the same distance as their lower redshift parents because they still retain a component of their earlier, quasar intrinsic redshift.”

Now, let’s take a look at the quiet little elliptical – NGC 5982. Just this year it was studied by Del Burgo (et al) for its dust shell. According to the report: “Shells in Ellipticals are peculiar faint sharp edged features that are thought to be formed by galaxy mergers. We use Spitzer data in the wavelength range from 3.6 to 160 μm and HST/ACS optical data. After subtracting the galaxy models, residual images are used to identify the shells. We detect for the first time shells from mid-infrared data. The very different distributions of dust, warm gas and HI gas together with the presence of shells and a kinematically decoupled core suggest a minor merger in NGC 5982.”

Ah, ha! So, it’s always the quiet ones that get ya’, huh? Then it might interest you to know that NGC 5982 may also contain its own black hole, a peculiar population of stars, a low luminosity active galactic nucleus and may have even been a product of a black hole merger! What more, new globular clusters may have formed during these interactions without the benefits of gaseous materials. Simply too cool…

Now… How about the wild looking edge-on, NGC 5981? Science loves to examine what it just can’t quite see and in the case of this highly inclined spiral, we’ve found out that the stellar disc just might be cut off – or foreshortened. According to a 2007 work done by Florido (et al); “This is the first work reporting observations of the truncation of a stellar disc, in both the optical and the NIR spectral ranges. No galaxy has been observed at both wavelengths with the required depth. The optical radial profiles of spiral galaxy discs seem to suggest a double exponential behaviour, whilst NIR profiles seem to show a real truncation. NGC 6504 has a real truncation in both the optical and the NIR radial profiles. A double exponential does not fit the observed optical profile. The truncation radius is larger in the V band than in the NIR by ~10 arcsec, about 3 kpc (equivalent to about 10%).”

But, just because its equipment is a little shorter than most, does that mean it doesn’t produce as many stars? Not hardly. It just means its peanut-shaped central bulge may be embedded in a dark halo. Thanks to the work of Joop Schaye who also took a look at NGC 5981, we know a little more about these properties. “We study global star formation thresholds in the outer parts of galaxies by investigating the stability of disk galaxies embedded in dark halos. The disks are self-gravitating, contain metals and dust, and are exposed to UV radiation. We find that the critical surface density for the existence of a cold interstellar phase depends only weakly on the parameters of the model and coincides with the empirically derived surface density threshold for star formation. Furthermore, it is shown that the drop in the thermal velocity dispersion associated with the transition from the warm to the cold gas phase triggers gravitational instability on a wide range of scales. The presence of strong turbulence does not undermine this conclusion if the disk is self-gravitating. Models based on the hypothesis that the onset of thermal instability determines the star formation threshold in the outer parts of galaxies can reproduce many observations, including the threshold radii, the column densities, and the sizes of stellar disks as a function of disk scale length and mass.”

While we’ll never see the Draco Trio in the telescope eyepiece as well as what this incredible image by Ken Crawford presents, we welcome the Dragon Slayer for the opportunity it gives us to take a closer look at another cosmic mystery. Is the Draco Group really a galaxy group? Perhaps. According to independent research papers done by both Giuricin and Garcia, this small group of friends collectively known as the NGC 5866 Group (because it’s the brightest) is located to the northwest of both the M101 Group and its companion galaxies which makes it proximity. Also nearby is the M51 Group, home to the Whirlpool Galaxy, the Sunflower Galaxy, and several others. The distances to these three groups was gathered by studying their individual members and science has found they are similar – and perhaps part of a much larger, more loose association than we’ve yet discovered.

But we’re learning…

Many thanks to AORAIA member Ken Crawford for the use of the spectacular image and the awesome research challenge it posed! My gratitude for the inspiration and the learning challenge…

Posted on by Nancy Atkinson

Oops, TW Hydrae b Isn’t a Planet; Just a Sunspot

Artists depiction of what the TW Hydrae system might have looked like. Credit: Max Planck Institute

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You gotta love this about science; someone is always checking your work. Early this year a new exoplanet discovery was announced: TW Hydrae b, a huge planet about ten times as massive as Jupiter. Astronomers thought the planet was in a super-tight orbit around its host star (TW Hydrae), circling in only 3.56 days at a distance of about 6 million kilometers, which is about 4 percent of the distance from the Sun to the Earth. However, another group of astronomers decided to analyze some new optical and infrared data to confirm the radial velocity signal of the planet. Something didn’t seem right, so they ran a few more tests and computer models and determined what they were seeing wasn’t a planet. It was a big sunspot. “Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54 deg can reproduce the reported RV variations,” the astronomers reported in their paper. The rest of the astronomical world must agree with the new determination, as TW Hydrae b has now been dropped from the Planet Quest New Worlds Atlas (a fun site to peruse.) But nature doesn’t like a void, — and astronomers have been working hard in the planet-search department, — so, three new extra solar planets have been discovered and added to the atlas, for a current planet count of 309.

GJ 832 b is about half the size mass of Jupiter and orbits 3.4 AU from its tiny host star. The star is a yellow, sun-like G star, about 16 light years from Earth. It was found with the Anglo-Australian Telescope. Astronomers say it has the largest angular distance from its star among radial velocity detected exoplanets, which makes it a potentially interesting target for future direct detection.

HD 205739 b was also just announced:. This exoplanet is 1.37 times the size mass of Jupiter, and orbits about .9 AU from its star, a blue to white star, which is 1.22x the size of the sun, and 294 light years from Earth. It has an eccentric orbit, and astronomers believe there may be an additional planet in this system, because of how the planet orbits.

Another planet found by the same astronomical team is HD 154672 b. This is a biggie, at about five times the size mass of Jupiter, but only about .6 AU distant from its star, which is just about sun-size, and about 213 light years from Earth. The planet has an orbital period of 163.9 days.

These last two planets were found using the N2K Doppler planet search program with the Magellan telescopes.

Sources: arXiv (here, here and here) and Twitter, PlanetQuest