Posted on by Nicholos Wethington

Rosetta Uncovers a Thick, Dusty Blanket on Lutetia

An image taken by the Rosetta spacecraft on its closest approach to 21-Lutetia in July. Recent analysis of the data shows a thick, dusty blanket coating the asteroid. Image Credit:ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

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If you think that asteroids are boring, unchanging rocks floating in space waiting only to crop up in bad science fiction films, think again. Images and data that are being returned from various asteroid flybys – such as those by the Rosetta spacecraft and Hayabusa sample return mission – show that asteroids are dynamic, changing miniature worlds unto themselves.

During the recent flyby of the asteroid 21-Lutetia in July, the ESA’s Rosetta spacecraft took an amazing amount of data. After combing through all of this data over the past few months, astronomers have calculated that the asteroid is covered in a 2000-foot (600 meter)-thick blanket of rocks and dust called regolith. This dust is not unlike the outer layer of the Earth’s Moon, consisting of pulverized material that has accumulated over billions of years.

Rosetta is on a course to meet up with the comet 67P/Churyumov-Gerasimenko in 2014, but the spacecraft is no stranger to asteroid visits – on September 6th, 2008, Rosetta made its closest approach of the asteroid 2867-Steins. During this brief visit, Rosetta came within 500 miles (800km) of the small, diamond-shaped asteroid. Among the discoveries made were a chain of impact craters that were likely caused by the collision with a meteoroid stream, or the impact with another small body.

It then approached 21-Lutetia on July 10th of 2010, monitoring the asteroid with 17 instruments on board the spacecraft.

Rosetta took a number of images of the flyby, as well as examining the asteroid with electromagnetic detectors that covered the gamut from the UV to radio waves. Here’s a short animation showing the flyby:

Dr. Rita Schulz from the ESA Research and Scientific Support Department in the Netherlands presented this new information about 21-Lutetia’s regolith today at the Division for Planetary Sciences meeting in Pasadena, CA. She said that the regolith on the asteroid has been determined to be about 2000 feet (600 meters) thick, and that it resembles the regolith on the Moon. Images from the flyby reveal landslides, boulders, ridges, and other kinds of different geologic (or asterologic?) features.

21-Lutetia was determined by the July flyby to have a large, bowl-shaped impact crater on its surface, as well as an abundance of smaller craters. The thick covering of dust “softens” the sharper edges of impact craters in many of the images taken. Whether or not most asteroids of this size are covered in a similar blanket of material remains to be seen.

Boulders can be seen in this close-up image of 21-Lutetia, as taken by Rosetta during the July flyby. Image Credit: mage credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

In understanding more about asteroids and comets, astronomers are better able to hone their model of how our Solar System formed. By studying the composition and frequency of impacts of various asteroids, they can improve their data of just how things have changed since the primordial Solar System.

You can bet your boulders that Rosetta isn’t the only spacecraft to be making multiple rendezvous missions with the smaller denizens of our Solar System. Close flybys, impacts and landings on asteroids and comets are becoming almost commonplace for spacecraft.

There’s the Deep Impact mission, which slammed a huge copper weight into the comet Tempel 1, and has since been renamed EPOXI and is set to approach the comet Hartley 2. The upcoming approach of Vesta and Ceres by the Dawn mission is very much anticipated, and of course the recent success of the Hayabusa asteroid explorer has been a terrific tale of just how much we stand to learn from the trail of small celestial cairns that lead into our past.

Source: ESA, DPS Press Release

Posted on by Nicholos Wethington

5 Reasons to Attend Your Nearest Star Party

A daytime shot of the Star Field for the 2010 Iowa Star Party held at Whiterock Observatory. 36 participants showed up to take in the incredibly dark skies. Image Credit: Andrew Sorenson

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If you’ve been wanting to get out to view the skies at night from your back yard – or maybe a darker location – but don’t know your way around the skies or have access to a telescope or binoculars, attending a star party may be just what you need to do. I recently attended the 8th annual Iowa Star Party under the dark skies of Coon Rapids, Iowa.

It was an extraordinary experience to meet other amateur astronomers, look at (and through) their telescopes, and in general to be surrounded by a bunch of other people keenly interested in astronomy. Here’s a brief synopsis of what my experience at the star party was like, followed by reasons to seek out a dark-sky gathering near you and a few links to large star parties around the world.

The star party ran from Thursday, September 2nd through Sunday the 5th. In attendance over the weekend were 36 participants and their families, most from Iowa but a few from Minnesota, Nebraska and Illinois. It’s no Astrofest, but it was a good showing for Iowa!

The Iowa Star Party is located at the Whiterock Conservancy, an non-profit land-trust that is gracious enough to host the party every year, and has named the field in which the ‘scopes are located the Star Field. The site was chosen by former Ames Area Amateur Astronomers member Dave Oesper because it is the least populated place with the lowest amount of light pollution in central Iowa. The Ames club, of which I am a member, did much of the organizing for the event. All three nights were perfectly clear with good seeing, and though it was really windy during the daytime, it tended to calm down towards the evening.

I was not personally able to attend the first evening, but it was reportedly cold and clear, and the few that did show up for the kickoff were treated to dark, clear skies and little wind. Friday was the public night, where anyone from anywhere was invited to come look through a scope and attend a talk about the history of astronomy and some general information about viewing by local amateur astronomer Drew Sorenson.

The talk ended in a “debate” about refractors vs. reflectors that turned out to be a surprise, unplanned marshmallow fight. Yeah, we threw marshmallows at each other – with gusto I might add. A 60mm homemade refractor was then raffled off as a door prize.

175 members of the public showed up for a short presentation and a long night of good viewing on Friday at the Iowa Star Party. Facing the camera at the table are Emily Babbin of Whitrock Conservancy, center, and Al Johnson, Vice President of the AAAA, right. Image Credit: Andrew Sorenson

In all, 175 people showed up for what turned out to be a spectacular night under some of the darkest skies I’ve seen. Members of the public were treated to a spectacular view of the Milky Way, as well as views of Jupiter, M13, Mizar, Albirio, and countless other objects through the eyepieces of about 20 telescopes.

Saturday night, the last evening of the star party, there was a banquet followed by a talk by Dr. Charles Nelson, Drake University Assistant Professor of Astronomy. Dr. Nelson gave a talk about quasars, which included a brief history of their discovery and the techniques we use to study and analyze them today, with a heavy emphasis on spectroscopy. After the talk, everyone headed out to the Star Field to spend the rest of the dark night observing.

Objects that my club viewed included the Veil Nebula (which was stunningly large and wispy through my club’s 24″ telescope), Herschel’s Garnet, the Whirlpool Galaxy, the Andromeda Galaxy, M31, M22 and Jupiter and Uranus. Other participants viewed the quasar Markarian 205, in keeping with the quasar-themed lecture.

We concluded Sunday with a breakfast, during which I made countless pancakes faster than I’ve ever made pancakes before. Staying up all night staring at the stars makes one hungry!

This is just a small taste of my own individual experience, but all of this fun and more could be had by you! Here are a few reasons to seek out your own star party:

– You might will learn something – No matter how much time you spend at a ‘scope, meeting with other amateur astronomers will give you ideas and techniques and knowledge that you couldn’t even dream of discovering on your own. Plus, it’s fun to share an interest in any subject with other human beings, face to face.

– You’ll see more than you would at home – Larger star parties are inherently located in areas with very dark skies, meaning that there will be so much more to see than you could at home. Even smaller star parties near towns tend to avoid locations that are polluted by city lights. Plus, there will likely be people there with huge telescopes that are more than willing to show you all that a large light bucket has to offer.
– You can share your knowledge of the skies – A star party is a great chance to show off your knowledge of the skies to other amateurs, as well as members of the public if there is a public viewing night.

– You will meet other astronomers –  Sure, amateur astronomy can be a lonely hobby, spending hours outside in the dark when everyone else is asleep. But at a star party, you’ll get the chance to share your passion for the skies with other astronomers, look through their telescopes and show them your own. You’re not alone!

-You’ll have fun – Even if you have a passing interest in astronomy and/or don’t own a telescope or binoculars, looking through a telescope is just plain cool, and getting to know your way around the skies is always a treat. And if it clouds over, chances are that someone will bring old episodes of Star Trek to watch!

If you’re interested in finding your nearest star party, here are a few resources to take a look at.

In the United States, The Astronomical League compiles a list of upcoming star parties and astronomy-related events on their website and in their print newsletter, The Reflector.

For our Australian readers, The Astronomical Society of New South Wales Incorporated hosts their own annual star party, and has a link to other events in the region here.

In Canada, The Royal Astronomical Society of Canada has a list (and nifty map) that includes many of the star parties throughout the country.

As for the U.K., The British Astronomical Association has a list of affiliated societies in the United Kingdom, and the European Astrofest is held annually in London.

Of course, this only covers our readership located in the predominantly English-speaking regions of the Earth, so if you have a favorite event near you, feel free to link to it in the comments. Also share your favorite memory of a star party in the comments section, if you feel moved to do so.

As amateur astronomers are wont to say, “Clear Skies!”

Posted on by Nicholos Wethington

NASA to Send a Probe Into the Sun

An artist's impression of the Solar Probe Plus satellite, which will fly into the corona of the Sun to get an unprecedented look at how our Sun works. Image Credit: NASA

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NASA recently announced its choices for the experiments to fly aboard the Solar Probe Plus spacecraft, which is slated to launch no later than 2018. This spacecraft will perform the unprecedented task of flying into the Sun’s atmosphere – or corona – to take measurements of the plasma, magnetic fields and dust that surround our nearest star. It will be the first human-made satellite to approach the Sun at such a close proximity.

The previous record-holder for a spacecraft that approached the Sun was Helios 2, which came within 27 million miles (43.5 million kilometers) of the Sun in 1976. Solar Probe Plus will shatter that record, flying to 3.7 million miles (5.9 million kilometers) of the Sun’s surface at its closest approach. In flying so close to the Sun, the spacecraft will be able to get amazingly detailed data on the structure of the atmosphere that surrounds the Sun.

As you can imagine, it gets a little toasty as one gets that close to the Sun. Solar Probe Plus will utilize a special heat shield made of an 8-foot (2.4 m), 4.5 inch (11 cm)-thick special carbon-composite foam plate that will protect the craft from temperatures of up to 2600 degrees Fahrenheit (1400 degrees Celsius) and intense solar radiation. The heat shield is a modified version of that which was used in the MESSENGER mission to Mercury.

NASA has chosen five science projects out of the thirteen that were proposed since 2009. The selected proposals are, according to the press release:

— Solar Wind Electrons Alphas and Protons Investigation: principal investigator, Justin C. Kasper, Smithsonian Astrophysical Observatory in Cambridge, Mass. This investigation will specifically count the most abundant particles in the solar wind — electrons, protons and helium ions — and measure their properties. The investigation also is designed to catch some of the particles in a special cup for direct analysis.
— Wide-field Imager: principal investigator, Russell Howard, Naval Research Laboratory in Washington. This telescope will make 3-D images of the sun’s corona, or atmosphere. The experiment actually will see the solar wind and provide 3-D images of clouds and shocks as they approach and pass the spacecraft. This investigation complements instruments on the spacecraft providing direct measurements by imaging the plasma the other instruments sample.
— Fields Experiment: principal investigator, Stuart Bale, University of California Space Sciences Laboratory in Berkeley, Calif. This investigation will make direct measurements of electric and magnetic fields, radio emissions, and shock waves that course through the sun’s atmospheric plasma. The experiment also serves as a giant dust detector, registering voltage signatures when specks of space dust hit the spacecraft’s antenna.
— Integrated Science Investigation of the Sun:principal investigator, David McComas of the Southwest Research Institute in San Antonio. This investigation consists of two instruments that will take an inventory of elements in the sun’s atmosphere using a mass spectrometer to weigh and sort ions in the vicinity of the spacecraft.
— Heliospheric Origins with Solar Probe Plus: principal investigator, Marco Velli of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Velli is the mission’s observatory scientist, responsible for serving as a senior scientist on the science working group. He will provide an independent assessment of scientific performance and act as a community advocate for the mission.

Two important questions that the mission hopes to answer is the perplexing mystery of why the Sun’s atmosphere is hotter than its surface, and the mechanism for the solar wind that emanates from the Sun into the Solar System. The spacecraft will have a front-row seat to watch the solar wind speed up from subsonic to supersonic speed.

Because of the conservation of momentum, it takes a lot of slowing down to send a spacecraft towards the Sun. The Earth and objects on the Earth are traveling around the Sun at an average of 30 kilometers per second (67,000 miles per hour). So, to slow the spacecraft down enough to get it close to the Sun, it will have to fly around Venus seven times! This is the opposite of a gravity assist, or “slingshot”, in which a satellite gains energy by flying by a planet. In the case of Solar Probe Plus, as well as that of MESSENGER, multiple flybys of Venus imparts some of the craft’s energy to Venus, thereby slowing down the spacecraft.

The Solar Probe Plus mission is part of NASA’s “Living With a Star Program”, of which the Solar Dynamics Observatory is also a mission. This program is designed to study the impact our Sun has on the space environment of the Solar System, and acquire data to better equip future space missions.

Source: NASA press release, APL mission site

Posted on by Nicholos Wethington

The Sun’s Conveyor Belt May Lengthen Solar Cycles

The conveyor belt of the Sun - a large flow of plasma that circulates under the surface - may be responsible for the duration of solar cycles. Image Credit: Science@NASA

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The Sun seems to finally be waking up in earnest from the long slumber of the past cycle. Solar cycles tend to last on average about 11 years, but the last cycle – solar cycle 23 – was 12.5 years long. The cause of the most recent lull in the Sun’s activity is somewhat enigmatic, but it may be explained by the “conveyor belt” of plasma that circulates in the Sun’s chromosphere and photosophere. Just how far this conveyor belt of plasma extends underneath the Sun may heavily influence the duration of solar cycles.

In a recent paper published in Geophysical Research Letters, Dr. Mausumi Dikpati of the High Altitude Observatory National Center for Atmospheric Research in Boulder, Colorado and her team modeled data from the Mount Wilson Observatory for the duration of the last solar cycle. When they analyzed and modeled surface Doppler measurements of the flow of plasma currents that course underneath the surface of the Sun, they discovered that the flow extended all the way to the poles.

This is in contrast to data from previous, average-length solar cycles, in which the meridional plasma flow – or the Sun’s conveyor belt – flowed only to about 60 degrees latitude. This flow is not unlike thermohaline circulation here on Earth, in which the ocean transports heat around the globe.

Dr. Dikpati said in an email interview, “This is the first time that the Sun’s conveyor-belt has been measured accurately enough for two consecutive cycles (cycles 22 spanning approximately 1986-1996.5 and cycle 23 spanning 1996.5-2009). From these data we now know that cycle 22 had a shorter conveyor-belt reaching only to 60-degree latitude, while cycle 23 had a long conveyor-belt extending all the way to the pole.”

The cycles of the Sun are intricately linked to the magnetic field permeating our nearest star. Gigantic loops of the magnetic field of the Sun are what cause sunspots, and as the contours of the magnetic field change over the cycle of the Sun, more or fewer sunspots are seen, as well as solar flares and other activity. There is always a lack of sunspots between the cycles, but the minimum at the end of cycle 23 was unusually long.

The conveyor belt of plasma flowing in the chromosphere and photosphere essentially drags along with it the magnetic flux of the Sun. Because the extent of the conveyor belt reached a higher latitude, it took the magnetic flux longer to return to the equator, resulting in the delay of sunspots marking the onset of cycle 24.

Dr. Dikpati and her team determined that it wasn’t the speed of the flow of plasma conveyor belt that lengthened the solar cycle, but the extent into higher latitudes, and slower return to the equator. Though the speed of the conveyor belt was a bit higher than usual over the past five years, it also stretched much further than during a normal cycle.

Dr. Dikpati said of using data from previous solar cycles to better refine their model of the conveyor belt:

From the same data source (Mount Wilson data from Roger Ulrich) there is evidence of a short conveyor-belt in cycles 19, 20 and 21 also. All these cycles had periods (10.5 years) like cycle 22. Back beyond that we are hoping that others in the community will search for evidence of the latitudinal extent of the conveyor-belt in even earlier cycles. In fact, theory of the conveyor-belt in high-latitudes indicates that a shorter conveyor belt should be more common in the Sun, rather this long conveyor belt in cycle 23 may be the exception. There is already evidence from Mount Wilson data that, at the start of cycle 24, the conveyor-belt is shortening again, suggesting that cycle 24 is going to be more like cycles 19 – 22 in length.

By getting a better model of the interplay between the plasma flow and the Sun’s magnetic field, solar scientists may be able to better predict and explain the length of future and past solar cycles.

Dr. Dikpati said, “The conveyor belt also governs the memory of the Sun about its past magnetic features. This is an important ingredient for building prediction models for solar cycles.”

Source: Geophysical Research Letters, email interview with Dr. Mausumi Dikpati

Posted on by Nicholos Wethington

Telescope’s Laser Pointer Clarifies Blurry Skies

The new laser adaptive optics system in action. At Mount Hopkins in Arizona, a bundle of five lasers is shot into the atmosphere to improve the imaging of the 6.3-meter MMT telescope. Image Credit: Thomas Stalcup

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While it’s handy for us humans (and all of the other life on our planet for that matter), the atmosphere is almost universally cursed among astronomers. It’s great for breathing, but when it comes to astronomical observations of faint objects, all the atmosphere tends to do is muck up the view. In the past 20 years, development of adaptive optics – essentially telescopes that change the shape of their mirrors to improve their imaging capability – has dramatically improved what we can see in space from the Earth.

With a new technique involving lasers (Yes! Lasers!), the images capable with an adaptive optics telescope could be nearly as crisp as those from the Hubble Space Telescope over a wide field of view. A team of University of Arizona astronomers led by Michael Hart has developed a technique that helps calibrate the surface of the telescope very precisely, which leads to very, very clear images of objects that would normally be very blurry.

Laser adaptive optics in telescopes are a relatively new development in getting better image quality out of ground-based telescopes. While it’s nice to be able to use space-based telescopes like the Hubble and the forthcoming James Webb Space Telescope, they are certainly expensive to launch and maintain. On top of that, there are a lot of astronomers competing for very little time on these telescopes. Telescopes like the Very Large Telescope in Chile, and the Keck Telescope in Hawaii both already use laser adaptive optics to improve imaging.

Initially, adaptive optics focused in on a brighter star near the area of the sky that the telescope was observing, and actuators in the back of the mirror were moved very rapidly by a computer to cancel out atmospheric distortions. This system is limited, however, to areas of the sky that contain such an object.

Laser adaptive optics are more flexible in their usability – the technique involves using a single laser to excite molecules in the atmosphere to glow, and then using this as a “guide star” to calibrate the mirror to correct for distortions caused by turbulence in the atmosphere. A computer analyzes the incoming light from the artificial guide star, and can determine just how the atmosphere is behaving, changing the surface of the mirror to compensate.

In using a single laser, the adaptive optics can only compensate for turbulence in a very limited field of view. The new technique, pioneered at the 6.5-m MMT telescope in Arizona, uses not just one laser but five green lasers to produce five separate guide stars over a wider field of view, 2 arc minutes. The angular resolution is less than that of the single laser variety – for comparison, the Keck or VLT can produce images with a 30-60 milli-arcsecond resolution, but being able to see better over a wider field of view has many advantages.

In the image on the left, the cluster M3 appears blurry with the laser adaptive optics system turned off. Things are much clearer using the system, and individual stars in the cluster become visible, as can be seen in the image on the right. Image Credit: Michael Hart

The ability to take the spectra of older galaxies, which are very faint, is possible using this technique. By taking their spectra, scientists are better able to understand the composition and structure of objects in space. Using the new technique, taking the spectra of galaxies that are 10 billion years old – and thus have a very high red shift – should be possible from the ground.

Supermassive clusters of stars would also be more easily scrutinized using the technique, as images taken in a single pointing of the telescope on different nights would allow astronomers to understand just which stars are part of the cluster and which are not gravitationally bound.

The results of the team’s efforts was published in the Astrophysical Journal in 2009, and the original paper is available here on Arxiv.

Source: Eurekalert, Arxiv paper

Posted on by Nicholos Wethington

Most Massive Star Discovered: Over 300 Suns at Birth!

Zooming in on a giant: the Tarantula Nebula in the visible light on the left, a zoomed-in image of the location of R 136 in the center panel, and the R 136 cluster in the lower right of the last panel. Image Credit:ESO/P. Crowther/C.J. Evans

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Often, writing about astronomy tends to mirror the job of those writing for the Guinness Book of World Records – just when you think a record is practically unbeatable, somebody else appears to show up the previous record-holder. This is surely the case with the stellar heavyweight (er, “heavymass”) R 136a1, which has been shown by data taken using the European Southern Observatory’s Very Large Telescope and the Hubble Space Telescope to tip the stellar scales at 265 times the mass of our Sun. What’s even more impressive is that R 136a1 has lost mass over the course of its lifetime, and likely was about 320 solar masses at birth. That deserves a “Yikes!”

R 136a1 lies in a cluster of young, massive stars with hot surface temperatures that is located inside the Tarantula Nebula. The Tarantula Nebula is nested inside the Large Magellanic Cloud, one of the Milky Way’s closest galactic neighbors, 165,000 light-years away. The cluster is called RMC 136a (or more commonly referred to as R136), and in addition to the whopper that is R 136a1, there are three other stars with masses at birth in the 150 solar mass range.

Extremely massive stars like R 136a1 were previously thought to be unable to form, posing a challenge to stellar physicists as to just how this behemoth came about. It’s possible that it formed by itself in the relatively dense gas and dust of the R136 cluster, or that multiple smaller stars merged to create the larger star at some point early on in its lifetime.

If breaking the mass record weren’t enough, R136a1 also happens to be the most luminous star ever discovered, with an output of energy that is over 10 million times that of the Sun. If you want to learn more about how astronomers determine the mass and luminosity of stars, here is an excellent and thorough introduction to the subject.

To validate the models used in determining the mass and luminosity of the stars in R136, the team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, used the VLT to examine NGC 3603, a closer stellar nursery. NGC 3603 is only 22,000 light years away, and two of the stars in that cluster are in a binary system, which allowed the team to measure their masses.

A comparison of the smallest stars (red dwarfs), Sun-like stars, blue dwarfs, and the most massive star ever discovered, R 136a1. Image Credit: ESO/M. Kornmesser

We are lucky to have observed this extremely massive star, as the rule for the most massive stars is, “Live fast, die young.” The more massive a star is, the faster it churns through the fuel that powers its increased luminosity. Our Sun, which has a medium amount of mass in relation to the two extremes, will last for around for about 10 billion years. Smaller, red dwarf stars can last trillions of years, while large stars on the scale of R 136a1 only glimmer in all of their brilliance for millions of years.

What will happen to R 136a1 at the end of its life? Stars with a mass of over 150 Suns ultimately explode in a light show of staggering proportions generated by what’s called a pair-instability supernova. For more on this phenomenon, check out this article from Universe Today from last year.

Source: ESO press release

A nod and a snarky wink to Genevieve Valentine

Posted on by Nicholos Wethington

First Quasar Gravitational Lens Discovered (w/video)

The quasi-stellar object SDSS J0013+1523 has been shown to warp the light of a background galaxy around it, producing a magnified double-image from our perspective on Earth. Image Credit: Courbin, Meylan, Djorgovski, et al., EPFL/Caltech/WMKO

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Gravitation lensing – a phenomenon that falls out of Einstein’s theory of general relativity – has been observed numerous times, making for some fantastic images of rings, arcs and crosses composed of massive galaxies light years away. As the light from a background object is bent by gravity around a foreground object, multiple, magnified images of the background object are produced from our vantage point.

For the first time, a quasar (quasi-stellar object) has been shown to gravitationally lens a galaxy behind it. About a hundred instances of gravitational lenses that consist of a foreground galaxy and a background quasar have been found, but this is the very first time where the opposite is the case; that is, a quasar bending the light from a background galaxy around it to create a multiple image of that galaxy.

Quasars are thought to be the result of a supermassive black hole at the center of a galaxy attempting to swallow up all of the matter that surrounds it. As the matter bunches up when it gets closer to the black hole, it heats up due to friction and begins to emit light across the electromagnetic spectrum. The light from a quasar can outshine an entire galaxy of stars, making it difficult to separate the light from a background galaxy from the overwhelming glare of the quasar itself.

To make this initial detection (there are surely many to follow), astronomers from the EPFL’s Laboratory of Astrophysics in cooperation with Caltech used data from the Sloan Digital Sky Survey (SDSS). They analyzed 22,298 quasars from the SDSS Data Release 7 catalog, and looked for images that had a strongly redshifted emission spectra. According to the paper announcing the results, “In these spectra, we look for emission lines redshifted beyond the redshift of the [quasar].”

In other words, a quasar that is lensing a galaxy in the background will exhibit a higher redshift than one that is not lensing a background galaxy, since the light from the galaxy and the quasar are combined in the SDSS data. So, quasars that had an expected redshift were thrown out, and a statistical analysis of quasars with emission lines that might mimic a gravitational lens eliminated many more of the objects. This left about 14 objects of the 22,298 analyzed as potential candidates. Of these 14, the team selected one to perform follow-up observations on, named SDSS J0013+1523.

SDSS J0013+1523 lies about 1.6 billion light years away, and is lensing a galaxy that is about 7.5 billion light years away from Earth. Using the Keck II telescope, they were able to confirm that SDSS J0013+1523 was indeed lensing the light from a galaxy located behind it. Hubble images of the discovery are in the works.

Here’s a video produced by the EPFL describing the results.

What is significant about this discovery – besides the novel aspect of a quasar acting as a lens – is that it will allow researchers to better refine their understanding of quasars. When light is bent around an object, it bends because of gravity, and gravity is a result of mass. So, something that is very massive will act as a stronger lens than something that is tiny, and the mass of the object doing all of the lensing work – in this case, the foreground quasar – can be determined.

Their results were published in a letter to Astronomy & Astrophysics on July 16th. The original paper is available for your perusal here.

Source: Eurekalert here and here, Arxiv paper here

Posted on by Nicholos Wethington

Andromeda’s Unstable Black Hole

The Andromeda galaxy as seen in optical light, and Chandra's X-ray vision of the changing supermassive black hole in Andromeda's heart. Image Credit: X-Ray NASA/CXC/SAO/Li et al.), Optical (DSS)

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The Andromeda galaxy, the closest spiral galaxy to our own Milky Way, has a supermassive blackhole at the center of it much like other galaxies. Because of its proximity to us, Andromeda – or M31 – is an excellent place to study just how the supermassive black holes in the centers of galaxies consume material to grow, and interact gravitationally with the surrounding material.

Over the course of the last ten years, NASA’s Chandra X-Ray observatory has monitored closely the supermassive black hole at Andromeda’s heart. This long-term data set gives astronomers a very nuanced picture of just how these monstrous black holes change over time. Zhiyuan Li of the Harvard-Smithsonian Center for Astrophysics (CfA) presented results of this decade-long observation of the black hole at the 216th American Astronomical Society meeting in Miami, Florida this week.

From 1999 to 2006, M31 was relatively quiet and dim. In January of 2006, though, the black hole in the center of Andromeda suddenly brightened by over 100 times, and has remained 10 times as bright since. This suggests that the black hole swallowed something massive, but the details of the outburst in 2006 remain unclear.

The black hole in M31, located in the Andromeda constellation, likely continues to feed off of the stellar winds of a nearby star or the material in a large gas cloud that is falling into the black hole. As material is consumed, it drives the productions of X-rays in a relativistic jet streaming out from the black hole, which are then picked up by Chandra’s X-ray eyes.

The black hole in M31 is 10 to 100,000 times dimmer than expected, given that it has a large reservoir of gas surrounding it.

“The black holes in both Andromeda and the Milky Way are incredibly feeble. These two ‘anti-quasars’ provide special laboratories for us to study some of the dimmest type of accretion even seen onto a supermassive black hole,” Li said.

Accretion of matter into supermassive black holes is important to study because the evolution of galaxies is influenced by this process, Li said. The gravitational interplay of the black hole with the surrounding material in a galaxy, as well as the energy released when such supermassive black holes consume material in their surrounding accretion disks, change the structure of the galaxy as it forms. A better understanding of just how these supermassive black holes act in the later stages of spiral galaxy life may give clues as to what astronomers can expect to see in other galaxies.

M31 is readily seen with the naked eye in the constellation Andromeda, and is breathtaking to see through a telescope or binoculars. You won’t be able to see the black hole at its center, however! For more information on observing Andromeda, see our Guide to Space article on M31.

Source: Eurekalert

Posted on by Nicholos Wethington

Black Hole in M87 Wanders using Jetpack

Hubble Space Telescope Images of M87. At right, a large scale image taken with the Wide-Field/Planetary Camera-2 from 1998. The zoom-in images on the left are of the central portion of M87. HST-1 is a knot in the jet from the SMBH. (NASA and the Hubble Heritage Team (STScI/AURA), J. A. Biretta, W. B. Sparks, F. D. Macchetto, E. S. Perlman)

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The elliptical galaxy M87 is known for a jet of radiation that is streaming from the supermassive black hole (SMBH) that the galaxy houses. This jet, which is visible through large-aperture telescopes, may have functioned as a black hole ‘jetpack’, moving the SMBH from the center of mass of the galaxy – where most SMBHs are thought to reside.

Observations taken with the Hubble Space Telescope by a collaboration of astronomy researchers at Rochester Institute of Technology, Florida Institute of Technology and University of Sussex in the United Kingdom show the SMBH in M87 to be displaced from the center of the galaxy by as much as 7 parsecs (22.82 light years). This contradicts the long-held theory that supermassive black holes reside at the center of the galaxies they inhabit, and may give astronomers one way to trace the history of galaxies that have grown through merging.

What caused M87’s SMBH to wander off so far from the center of the galaxy? The most likely cause is a merger between two smaller supermassive black holes sometime in the past. This merger could have created gravitational waves that gave the engorged black hole a swift kick. Elliptical galaxies like M87 are thought to become the size they are through the merger of smaller galaxies.

Another theory is that the jet of radiation that sprays out of the SMBH has pushed with enough energy to essentially propel the black hole away from the center of M87. Okay, so it’s not really a ‘black hole jetpack’, but you have to admit that the combination of black holes – which are cool – and jetpacks, also cool, is too good to pass up. The motion of the SMBH happens to be in the opposite direction of the jet that we can see streaming from the object. For this scenario to be true, however, the jet would have to have been much more energetic millions of years ago, the researchers concluded.

There also does exist evidence for another jet of material that is streaming out of the other side of the SMBH, which would cancel the pushing motion of the jet that we can see, making the merger scenario much more likely. If the two jets were asymmetric to a high degree, however, this scenario still may be the case. More information on the structure and history of the jets would better clarify the cause of the black hole’s displacement.

This study of M87 is part of a wider project aimed at constraining the placement of supermassive black holes, also known as Active Galactic Nuclei or quasars, in their home galaxies. David Axon, dean of mathematical and physical sciences at Sussex, said in a press release, “In current galaxy formation scenarios galaxies are thought to be assembled by a process of merging. We should therefore expect that binary black holes and post coalescence recoiling black holes, like that in M87, are very common in the cosmos.”

The displacement of such black holes would be apparent in archived Hubble Space Telescope images, and the researchers that discovered this phenomenon in M87 used the HST archives to pinpoint the location of the SMBH. Further analysis of these archives could yield many, many more ‘wandering’ black holes.

These findings were presented on May 25th at the American Astronomical Society meeting in Miami, Florida. The team of researchers that collaborated on the finding include Daniel Batcheldor and Eric Perlman of the Florida Institute of Technology, Andrew Robinson and David Merritt of the Rochester Institute of Technology and David Axon of the University of Sussex. Their results were accepted for publication in Astrophysical Journal Letters, and the original paper, A Displaced Supermassive Black Hole in M87, is available on Arxiv right here.

Source: Eurekalert, Arxiv, Eric Perlman’s website

Posted on by Nicholos Wethington

Newly-Discovered Stellar Nurseries in the Milky Way

The Orion Nebula, one of the most brilliant star-forming regions in our galaxy. Other, newly-discovered regions like the Orion Nebula could help astronomers determing the chemical composition of our galaxy. Image Credit: APOD/Hubble Space Telescope

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Our Milky Way churns out about seven new stars per year on average. More massive stars are formed in what’s called H II regions, so-named because the gas present in these stellar nurseries is ionized by the radiation of the young, massive stars forming there. Recently-discovered regions in the Milky Way that are nurseries for massive stars may hold important clues as to the chemical composition and structural makeup of our galaxy.

Thomas Bania, of Boston University, said in an NRAO press release, “We can clearly relate the locations of these star-forming sites to the overall structure of the Galaxy. Further studies will allow us to better understand the process of star formation and to compare the chemical composition of such sites at widely different distances from the Galaxy’s center.”

The announcement of these newly discovered regions was made in a presentation today at the American Astronomical Society meeting in Miami, Florida. The team of astronomers that collaborated on the search includes Thomas Bania of Boston University, Loren Anderson of the Astrophysical Laboratory of Marseille in France, Dana Balser of the National Radio Astronomy Observatory (NRAO), and Robert Rood of the University of Virginia.

H II regions that you may be familiar with include the Orion Nebula (M42), visible just South of Orion’s Belt with the naked eye, and the Horsehead Nebula, so famously imaged by the Hubble Space Telescope. For more information on other known regions (and lots of pictures), visit the 2Micron All-Sky Survey at IPAC.

By studying such regions in other galaxies, and our own, the chemical composition and distribution of a galaxy can be determined. H II regions form out of giant molecular clouds of hydrogen, and remain stable until a collision happens between two clouds, creating a shockwave, or the resulting shockwave from a nearby supernova collapses some of the gas to form stars. As these stars form and start to shine, their radiation strips the molecular hydrogen of its electrons.

The astronomers used both infrared and radio telescopes to see through the thick dust and gas that pervades the Milky Way. By combing surveys taken by the Spitzer Space Telescope’s infrared camera, and the Very Large Array (VLA) radio telescope, they identified “hot spots” that would be good candidates for H II regions. To further verify their findings, they used the Robert C. Byrd Green Bank Telescope (GBT), a sensitive radio telescope that allowed them to detect radio frequencies emitted by electrons as they rejoined protons to form hydrogen. This process of recombination to form hydrogen is a telltale sign of regions that contain ionized hydrogen, or H II.

The location of the regions is concentrated near the ends of the central bar of the Milky Way, and in its spiral arms. Over 25 of the regions discovered were further from the center of the galaxy than our own Sun – a more detailed study of these outlying regions could give astronomers a better understanding of the evolution and composition of our Milky Way.

“There is evidence that the abundance of heavy elements changes with increasing distance from the Galactic center,” Bania said. “We now have many more objects to study and improve our understanding of this effect.”

Source: NRAO Press Release