Artist’s impression showing the disc around the young star T Chamaeleontis. The companion object in the foreground may be either a brown dwarf or a large planet. Credit: ESO/L. Calçada
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An international team of astronomers peering at a young star in the constellation Chamaeleon have detected a smaller companion — a dust-shrouded brown dwarf, or perhaps a planet — that appears to be carving out a large gap in the stellar disk. The discovery is a first: Although planets have been spotted before in more mature disks, this is the first detection of a planet-sized object in the disk around a young star.
Planets form from the disks of material around young stars, but the transition from dust disk to planetary system is rapid and few objects are caught during this phase. Astronomers are getting ever closer to glimpsing the births of planets, though — today’s announcement comes on the heels of a discovery last week using the Subaru Telescope in Hawaii, of a stellar disk around the star LkCa 15 similar in size to our own solar system, featuring rings and gaps possibly associated with the formation of giant planets.
T Chamaeleontis (RA 1h 04m 09.131s dec -76° 27′ 19.30″), T Cha for short, is a faint, young but sun-like star in the small southern constellation of Chamaeleon, about 350 light-years from Earth. T Cha is about seven million years old.
This chart shows the location of the young star T Cha within the constellation of Chamaeleon. The map shows most of the stars visible to the unaided eye under good conditions and the star itself is marked as a red circle. This star is too faint to see with the unaided eye, but is easily seen with a small telescope. Credit: ESO, IAU and Sky & Telescope
“Earlier studies had shown that T Cha was an excellent target for studying how planetary systems form,” said Johan Olofsson of the Max Planck Institute for Astronomy in Heidelberg, Germany, one of the lead authors of two related papers in the journal Astronomy & Astrophysics. “But this star is quite distant and the full power of the Very Large Telescope Interferometer was needed to resolve very fine details and see what is going on in the dust disk.”
The astronomers first observed T Cha using the AMBER instrument and the VLT Interferometer (VLTI). They found that some of the disk material formed a narrow dusty ring only about 20 million kilometers (12.4 million miles) from the star. Beyond this inner disk, they found a region devoid of dust with the outer part of the disk stretching out into regions beyond about 1.1 billion kilometers (683.5 million miles) from the star.
The ESO Very Large Telescope. Credit: ESO/G. Lombardi
“For us the gap in the dust disk around T Cha was a smoking gun,” said Nuria Huélamo, of the Centro de Astrobiología, ESAC in Spain, lead author of the second paper, “and we asked ourselves: could we be witnessing a companion digging a gap inside its protoplanetary disk?”
After further analysis, the team found the clear signature of an object located within the gap in the dust disk, about one billion kilometers, or 621 million miles, from the star — slightly further out than Jupiter is from our own sun.
The astronomers searched for the companion using NACO in two different spectral bands — at around 2.2 microns and 3.8 microns. The companion is only seen at the longer wavelength, which means that the object is either cool, like a planet, or a dust-shrouded brown dwarf.
Huélamo said he hopes future observations will reveal more about the companion and the disk, and explain what fuels the inner dusty disk.
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Anyone who took elementary science in grade school recalls the lesson about the three states of matter, right? That was the one where we were told that matter comes in three basic forms: liquid, solid and gas. This works for the periodic table of elements and can be extended to include just about any compound. Except perhaps for whipped cream (that damnable compound continues to defy attempts as classification!) But what if there were a fourth state for matter? It occurs when a state of matter similar to gas contains a large portion of ionized particles and generates its own magnetic field. It’s called Plasma, and it just happens to be the most common type of matter, comprising more than ninety-nine percent of matter in the visible universe and which permeates the solar system, interstellar and intergalactic environments.
The basic premise behind plasma is that heating a gas dissociates its molecular bonds, rendering it into its constituent atoms. Further heating leads to ionization (a loss of electrons), which turns it into a plasma. This plasma is therefore defined by the existence of charged particles, both positive ions and negative electrons.The presence of a large number of charged particles makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma, therefore, has properties quite unlike those of solids, liquids, or gases and is considered a distinct state of matter. Like a gas, plasma does not have a definite shape or a definite volume unless enclosed in a container. But unlike gas, under the influence of a magnetic field, it may form structures such as filaments, beams and double layers. It is precisely for this reason that plasma is used in the construction of electronics, such as plasma TVs and neon signs.
The existence of plasma was first discovered by Sir William Crookes in 1879 using an assembly that is today known as a “Crookes tube”, an experimental electrical discharge tube in which air is ionized by the application of a high voltage through a voltage coil. At the time, he labeled it “radiant matter” because of its luminous quality. Sir J.J. Thomson, a British physicist, identified the nature of the matter in 1897, thanks to his discovery of electrons and numerous experiments using cathode ray tubes. However, it was not until 1928 that the term “plasma” was coined by Irving Langmuir, an American chemist and physicist, who was apparently reminded of blood plasma.
As already mentioned, plasmas are by far the most common phase of matter in the universe. All the stars are made of plasma, and even the space between the stars is filled with a plasma, albeit a very sparse one.
We have written many articles about plasma for Universe Today. Here’s an article about the plasma engine, and here’s an article about the states of matter.
If you’d like more info on plasma, check out these articles from Chem4Kids and NASA Science.
[/caption]Magnetism is a fundamental force of the universe, essential to its function and existence in the same way that gravity and weak and strong nuclear forces are. But interestingly enough, there are several different kinds of magnetism. For example, there is ferromagnetism, a property which applies to super magnets, where magnetic properties exist regardless of whether or not there is a magnetic field acting on the material itself. There is also Diamagnetism, which refers to materials that are not affected by a magnetic field, and Paramagnetism, a form of magnetism that occurs only in the presence of an externally applied magnetic field.
Materials that are called ‘paramagnets’ are most often those that exhibit, at least over an appreciable temperature range, magnetic susceptibilities that adhere to the Curie or Curie–Weiss laws. According to these laws, which apply at low-levels of magnetization, the susceptibility of paramagnetic materials is inversely proportional to their temperature. Mathematically, this can be expressed as: M = C(B/T), where M is the resulting magnetization, B is the magnetic field, T is absolute temperature, measured in kelvins, C is a material-specific Curie constant.
Paramagnets were named and extensively researched by British scientist Michael Faraday – the man who gave us Faraday’s Constant, Faraday’s Law, the Faraday Effect, etc. – beginning in 1845. He, and many scientists since, found that certain material exhibited what was commonly referred to as “negative magnetism”. Most elements and some compounds are paramagnetic, with strong paramagnetism being exhibited by compounds containing iron, palladium, platinum, and certain rare-earth elements. In such compounds atoms of these elements have some inner electron shells that are incomplete, causing their unpaired electrons to spin like tops and orbit like satellites. This makes the atoms act like a permanent magnet, tending to align with and hence strengthen an applied magnetic field. However, once the magnetic field is removed, the atoms fall out of alignment and the material return to its original state. Strong paramagnetism also decreases with rising temperature because of the de-alignment produced by the greater random motion of the atomic magnets.
Weak paramagnetism, independent of temperature, is found in many metallic elements in the solid state, such as sodium and the other alkali metals. Other examples include Iron oxide, Uranium, Platinum, Tungsten, Cesium, Aluminum, Lithium, Magnesium, Sodium, and Oxygen gas. Even iron, a highly magnetic material, can become a paramagnet once it is heated above its relatively high Curie-point.
We have written many articles about magnetism for Universe Today. Here’s an article about magnetic field, and here’s an article about what magnets are made of.
If you’d like more info on paramagnetism, check out these articles from Hyperphysics and Physlink.
Watch the shuttle launch from a PlayStation. Image via the PlayStation Blog.
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Get a dose of reality via Sony’s PlayStation gaming system. The final liftoff of space shuttle Discovery on February 24, 2011 at 4:50 pm EST will be the first live streaming event to be offered by PlayStationHome, the social gaming networking service, and provide a unique “social viewing” environment.
“We’re excited about this new way for people to experience the exhilaration of human spaceflight as part of a larger community,” said David Weaver, NASA associate administrator for the Office of Communications. “In addition to the other two shuttle launches planned for April and June, NASA looks forward to sharing more of our endeavors with PlayStation users.”
The event is offered by Sunset Yacht, a premium personal space from LOOT, Sony DADC’s interactive entertainment development team. Users will be able to chat via Bluetooth headsets with others watching the launch – all from inside the PlayStation Home social gaming environment.
In addition to live streamed events, the Sunset Yacht’s NASA TV channel will offer hundreds of videos offering spectacular views of the universe from past and current NASA missions. A gallery of podcasts showcasing several missions including the Mars Science Laboratory and Voyager spacecraft also will be available from the agency’s Jet Propulsion Laboratory in Pasadena.
“The launch of the space shuttle Discovery provides a wonderful opportunity to introduce people to the fun of social viewing,” said LOOT Managing Director David Sterling. “Users can share this experience with their friends, regardless of where those friends happen to be in the world.”
Ready for another Where In The Universe Challenge? Here’s #138! Take a look and see if you can name where in the Universe this image is from. Give yourself extra points if you can name the spacecraft, telescope or instrument involved with this image. We provide the image today, but won’t reveal the answer until tomorrow. This gives you a chance to mull over the image and provide your answer/guess in the comment section. And Please, no links or extensive explanations of what you think this is — give everyone the chance to guess.
UPDATE: Answer now posted below!
This is the launch of space shuttle Discovery on an earlier launch – STS-70, back in 1995. It is a side view (much like the view that our photographer Alan Walters had from Astronaut Road for STS-133 last week — see our gallery of launch images), so that’s why only one SRB plume is visible. Of course STS-133 launched last week on Discovery’s final mission to space, a very historic page in space history.
News conference held Feb. 15 following the flyby of comet Tempel 1 by the Stardust-NExT spacecraft on Valentine's Day, Feb. 14. The spacecraft's closest approach was a distance of 112 miles. Participants are: Ed Weiler, NASA's associate administrator, Science Mission Directorate, Washington; Joe Veverka, Stardust-NExT principal investigator, Cornell University; Tim Larson, Stardust-NExT project manager, NASA's Jet Propulsion Laboratory, Pasadena, Calif.; Don Brownlee, Stardust-NExT co-investigator, University of Washington, Seattle; and Pete Schultz, Stardust-NExT co-investigator, Brown University.
As Stardust-Next was racing past Comet Tempel at 9.8 km/sec, or 24,000 MPH, it encountered a hail of bullet like particles akin to a warplane meeting the fury of armed resistance fighters which potentially could have utterly destroyed the probe.
NASA has released a cool sound track of the sounds of thousands of cometary dust particles pelting Stardust-NExT. The audio was recorded by an instrument aboard the spacecraft called the Dust Flux Monitor which measures sound waves and electrical pulses from dust impacts.
Telemetry downlinked after the Feb. 14 flyby indicates the spacecraft flew through waves of disintegrating cometary particles.
“The data indicate Stardust went through something similar to a B-17 bomber flying through flak in World War II,” says Don Brownlee, Stardust-NExT co-investigator from the University of Washington in Seattle.
I contacted co-investigator Don Brownlee for further insight into the sounds and sights of the Tempel 1 flyby.
“The 12 biggest particles penetrated the centimeter thick front honeycomb plate of the whipple meteoroid shield and were detected with the Dust Flux Monitor Instrument,“ Brownlee told me. “The instrument had two type of sensors made in a collaboration between the University of Chicago and the University of Kent in the UK.
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The shielding was installed to protect Stardust from the hail of cometary particles during its prior flyby at Comet Wild 2 in 2004. Brownlee was the Principal Investigator for Stardust during its original mission at Wild 2.
I asked Brownlee if the shields were essential to the spacecraft surviving the Tempel 1 flyby ?
“Yes,’ he replied.
“A total of approximately 5,000 particle impacts were detected,” Brownlee said. This was over a period of about 11 minutes during closest approach. The movie is in real time and is a visual representation of the sounds. It covers just a portion of the flyby.
“Like at Wild 2, the particles came out in bursts and clumps. The Tempel 1 flyby, the Wild 2 flyby and the recent imaging of Comet Hartley confirm that fragmenting. Dust and ice clods are commonly released into space by comets.”
“The biggest at Wild 2 was about 0.5 cm and this time at Tempel 1 they were probably a bit bigger. The penetrating impacts at Tempel 1 were about twice what they were at Wild 2 ….. Also about twice as fast!”
“The data indicate Stardust went through something similar to a B-17 bomber flying through flak in World War II,” said Don Brownlee, Stardust-NExT co-investigator from the University of Washington in Seattle. “Instead of having a little stream of uniform particles coming out, they apparently came out in chunks and crumbled.”
To my eye, I was surprised that the flyby images seemed to surpass those at Wild 2. Brownlee agreed.
“I was surprised,” said Brownlee. “The team did a terrific job and the images are better than before. Tempel is a little closer to the sun, the flyby was a little closer, the pictures were taken at a much higher rate and the imaging team put in a great effort to plan the exposures and to clean up the camera before the encounter. The mirror was scanning at it’s maximum rate!”
Listen to the Stardust-NExT post flyby briefing
News conference held Feb. 15 following the flyby of comet Tempel 1 by the Stardust-NExT spacecraft on Valentine’s Day, Feb. 14. The spacecraft’s closest approach was a distance of 112 miles. Participants are: Ed Weiler, NASA’s associate administrator, Science Mission Directorate, Washington; Joe Veverka, Stardust-NExT principal investigator, Cornell University; Tim Larson, Stardust-NExT project manager, NASA’s Jet Propulsion Laboratory, Pasadena, Calif.; Don Brownlee, Stardust-NExT co-investigator, University of Washington, Seattle; and Pete Schultz, Stardust-NExT co-investigator, Brown University.
Credit: X-ray: NASA/CXC/UNAM/Ioffe/D. Page, P. Shternin et al.; Optical: NASA/STScI; Illustration: NASA/CXC/M. Weiss
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NASA’s Chandra X-ray Observatory has discovered the first direct evidence for a superfluid, a bizarre, friction-free state of matter, at the core of a neutron star.
The image above, released today, shows X-rays from Chandra (red, green, and blue) and optical data from Hubble (gold) of Cassiopeia A, the remains of a massive star that exploded in a supernova. The evidence for superfluid has been found in the dense core of the star left behind, a so-called neutron star. The artist’s illustration in the inset shows a cut-out of the interior of the neutron star, where densities increase from the orange crust to the red core and finally to the inner red ball, the region where the superfluid exists.
Superfluids created in laboratories on Earth exhibit remarkable properties, such as the ability to climb upward and escape airtight containers. When they’re made of charged particles, superfluids are also superconductors, and they allow electric current to flow with no resistance. Such materials on Earth have widespread technological applications like producing the superconducting magnets used for magnetic resonance imaging [MRI].
Two independent research teams have used Chandra data to show that the interior of a neutron star contains superfluid and superconducting matter, a conclusion with important implications for understanding nuclear interactions in matter at the highest known densities. The teams publish their research separately in the journals Monthly Notices of the Royal Astronomical Society Letters and Physical Review Letters.
Cas A (RA 23h 23m 26.7s | Dec +58° 49′ 03.00) lies about 11,000 light-years away. Its star exploded about 330 years ago in Earth’s time-frame. A sequence of Chandra observations of the neutron star shows that the now compact object has cooled by about 4 percent over a ten-year period.
“This drop in temperature, although it sounds small, was really dramatic and surprising to see,” said Dany Page of the National Autonomous University in Mexico, leader of one of the two teams. “This means that something unusual is happening within this neutron star.”
Neutron stars contain the densest known matter that is directly observable; one teaspoon of neutron star material weighs six billion tons. The pressure in the star’s core is so high that most of the charged particles, electrons and protons, merge — resulting in a star composed mostly of neutrons.
The new results strongly suggest that the remaining protons in the star’s core are in a superfluid state and, because they carry a charge, also form a superconductor.
Both teams show that the rapid cooling in Cas A is explained by the formation of a neutron superfluid in the core of the neutron star within about the last 100 years as seen from Earth. The rapid cooling is expected to continue for a few decades, and then it should slow down.
“It turns out that Cas A may be a gift from the Universe because we would have to catch a very young neutron star at just the right point in time,” said Page’s co-author Madappa Prakash, from Ohio University. “Sometimes a little good fortune can go a long way in science.”
The onset of superfluidity in materials on Earth occurs at extremely low temperatures near absolute zero, but in neutron stars, it can occur at temperatures near a billion degrees Celsius. Until now there was a very large uncertainty in estimates of this critical temperature. This new research constrains the critical temperature to between one half a billion to just under a billion degrees.
Cas A will allow researchers to test models of how the strong nuclear force, which binds subatomic particles, behaves in ultradense matter. These results are also important for understanding a range of behavior in neutron stars, including “glitches,” neutron star precession and pulsation, magnetar outbursts and the evolution of neutron star magnetic fields.
Betelgeuse is a red super-giant, meaning it has enough mass that it will end as a supernova, rather than as a white dwarf with a planetary nebula. New research suggests that the star could've consumed a smaller companion star. Image credit: Hubble Space Telescope
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While planets orbiting twin stars are a staple of science fiction, another is having humans live on planets orbiting red giant stars. The majority of the story of Planet of the Apes takes place on a planet around Betelgeuse. Planets around Arcturus in Isaac Asimov’s Foundation series make up the capital of his Sirius Sector. Superman’s home planet was said to orbit a the fictional red giant, Rao. Races on these planets are often depicted as being old and wise since their stars are aged, and nearing the end of their lives. But is it really plausible to have such planets?
Stars don’t last forever. Our own Sun has an expiration date in about 5 billion years. At that time, the amount of hydrogen fuel in the core of the Sun will have run out. Currently, the fusion of that hydrogen into helium is giving rise to a pressure which keeps the star from collapsing in on itself due to gravity. But, when it runs out, that support mechanism will be gone and the Sun will start to shrink. This shrinking causes the star to heat up again, increasing the temperature until a shell of hydrogen around the now exhausted core becomes hot enough to take up the job of the core and begins fusing hydrogen to helium. This new energy source pushes the outer layers of the star back out causing it to swell to thousands of times its previous size. Meanwhile, the hotter temperature to ignite this form of fusion will mean that the star will give off 1,000 to 10,000 times as much light overall, but since this energy is spread out over such a large surface area, the star will appear red, hence the name.
So this is a red giant: A dying star that is swollen up and very bright.
Now to take a look at the other half of the equation, namely, what determines the habitability of a planet? Since these sci-fi stories inevitably have humans walking around on the surface, there’s some pretty strict criteria this will have to follow.
First off, the temperature must be not to hot and not to cold. In other words, the planet must be in the Habitable zone also known as the “Goldilocks zone”. This is generally a pretty good sized swath of celestial real estate. In our own solar system, it extends from roughly the orbit of Venus to the orbit of Mars. But what makes Mars and Venus inhospitable and Earth relatively cozy is our atmosphere. Unlike Mars, it’s thick enough to keep much of the heat we receive from the sun, but not too much of it like Venus.
This diagram shows the distances of the planets in the Solar System (upper row) and in the Gliese 581 system (lower row), from their respective stars (left). The habitable zone is indicated as the blue area, showing that Gliese 581 d is located inside the habitable zone around its low-mass red star. Based on a diagram by Franck Selsis, Univ. of Bordeaux. Credit: ESO
The atmosphere is crucial in other ways too. Obviously it’s what the intrepid explorers are going to be breathing. If there’s too much CO2, it’s not only going to trap too much heat, but make it hard to breathe. Also, CO2 doesn’t block UV light from the Sun and cancer rates would go up. So we need an oxygen rich atmosphere, but not too oxygen rich or there won’t be enough greenhouse gasses to keep the planet warm.
The problem here is that oxygen rich atmospheres just don’t exist without some assistance. Oxygen is actually very reactive. It likes to form bonds, making it unavailable to be free in the atmosphere like we want. It forms things like H2O, CO2, oxides, etc… This is why Mars and Venus have virtually no free oxygen in their atmospheres. What little they do comes from UV light striking the atmosphere and causing the bonded forms to disassociate, temporarily freeing the oxygen.
Earth only has as much free oxygen as it does because of photosynthesis. This gives us another criteria that we’ll need to determine habitability: the ability to produce photosynthesis.
So let’s start putting this all together.
Firstly, the evolution of the star as it leaves the main sequence, swelling up as it becomes a red giant and getting brighter and hotter will mean that the “Goldilocks zone” will be sweeping outwards. Planets that were formerly habitable like the Earth will be roasted if they aren’t entirely swallowed by the Sun as it grows. Instead, the habitable zone will be further out, more where Jupiter is now.
However, even if a planet were in this new habitable zone, this doesn’t mean its habitable under the condition that it also have an oxygen rich atmosphere. For that, we need to convert the atmosphere from an oxygen starved one, to an oxygen rich one via photosynthesis.
So the question is how quickly can this occur? Too slow and the habitable zone may have already swept by or the star may have run out of hydrogen in the shell and started contracting again only to ignite helium fusion in the core, once again freezing the planet.
The only example we have so far is on our own planet. For the first three billion years of life, there was little free oxygen until photosynthetic organisms arose and started converting it to levels near that of today. However, this process took several hundred million years. While this could probably be increased by an order of magnitude to tens of millions of years with genetically engineered bacteria seeded on the planet, we still need to make sure the timescales will work out.
It turns out the timescales will be different for different masses of stars. More massive stars burn through their fuel faster and will thus be shorter. For stars like the Sun, the red giant phase can last about 1.5 billion years, so ~100x longer than is necessary to develop an oxygen rich atmosphere. For stars twice as massive as the Sun, that timescale drops to a mere 40 million years, approaching the lower limit of what we’ll need. More massive stars will evolve even more quickly. So for this to be plausible, we’ll need lower mass stars that evolve slower. A rough upper limit here would be a two solar mass star.
However, there’s one more effect we need to worry about: Can we have enough CO2 in the atmosphere to even have photosynthesis? While not nearly as reactive as oxygen, carbon dioxide is also subject to being removed from the atmosphere. This is due to effects like silicate weathering such as CO2 + CaSiO3 –> CaCO3 + SiO2. While these effects are slow they build up with geological timescales. This means we can’t have old planets since they would have had all their free CO2 locked away into the surface. This balance was explored in a paper published in 2009 and determined that, for an Earth mass planet, the free CO2 would be exhausted long before the parent star even reached the red giant phase!
So we’re required to have low mass stars that evolve slowly to have enough time to develop the right atmosphere, but if they evolve that slowly, then there’s not enough CO2 left to get the atmosphere anyway! We’re stuck with a real Catch 22. The only way to make this feasible again is to find a way to introduce sufficient amounts of new CO2 into the atmosphere just as the habitable zone starts sweeping by.
Fortunately, there are some pretty large repositories of CO2 just flying around! Comets are composed mostly of frozen carbon monoxide and carbon dioxide. Crashing a few of them into a planet would introduce sufficient CO2 to potentially get photosynthesis started (once the dust settled down). Do that a few hundred thousand years before the planet would enter the habitable zone, wait ten million years, and then the planet could potentially be habitable for as much as an additional billion years more.
Ultimately this scenario would be plausible, but not exactly a good personal investment since you’d be dead long before you’d be able to reap the benefits. A long term strategy for the survival of a space faring species perhaps, but not a quick fix to toss down colonies and outposts.
Artist’s rendering of the environment around the supermassive black hole at the center of Mrk 231. The broad outflow seen in the Gemini data is shown as the fan-shaped wedge at the top of the accretion disk around the black hole, in side view. A similar outflow is probably present under the disk as well. The total amount of material entrained in the broad flow is at least 400 times the mass of the sun per year. Credit: Gemini Observatory/AURA, artwork by Lynette Cook
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Astronomers have long suspected that something must stymie actively growing black holes, because most galaxies in the local universe don’t have them. Now, the Gemini Observatory has captured a galactic check-and-balance — a large-scale quasar outflow in the galaxy Markarian 231 that appears to be depriving a supermassive black hole its diet of gas and dust.
The work is a collaboration between David Rupke of Rhodes College in Tennessee and the University of Maryland’s Sylvain Veilleux. The results are to be published in the March 10 issue of The Astrophysical Journal Letters.
Markarian 231 (12h56’14.23″ +56d52’25.24″) is located about 600 million light-years away in the direction of the constellation of Ursa Major. Although its mass is uncertain, some estimates indicate that Mrk 231 has a mass in stars about three times that of the Milky Way, and its central black hole is estimated to have a mass of at least 10 million solar masses or also about three times that of the supermassive black hole in the Milky Way.
Theoretical modeling specifically points to quasar outflows as the counterbalance to black hole growth. In this negative feedback loop, while the black hole is actively acquiring mass as a quasar, the outflows carry away energy and material, suppressing further growth. Small-scale outflows had been observed before, but none sufficiently powerful to account for this predicted and fundamental aspect of galaxy evolution. The Gemini observations provide the first clear evidence for outflows powerful enough to support the process necessary to starve the galactic black hole and quench star formation by limiting the availability of new material.
This extraction from the data cube shows the large-scale, fast outflow of neutral sodium at the center of the quasar Markarian 231. We are looking down onto the material that moves toward us relative to the galaxy, so the measured velocities are negative. The large black circle marks the location of the black hole, and red lines show the location of a radio jet. In addition to the quasar outflow, the jet pushes the material at the top right, resulting in even greater speeds. Part of the starburst is located at the position of the box at the lower left, and it is likely responsible for the gas motion in this region.
Study author Veilleux says Mrk 231 is an ideal laboratory for studying outflows caused by feedback from supermassive black holes: “This object is arguably the closest and best example that we know of a big galaxy in the final stages of a violent merger and in the process of shedding its cocoon and revealing a very energetic central quasar. This is really a last gasp of this galaxy; the black hole is belching its next meals into oblivion!” As extreme as Mrk 231’s eating habits appear, Veilleux adds that they are probably not unique: “When we look deep into space and back in time, quasars like this one are seen in large numbers, and all of them may have gone through shedding events like the one we are witnessing in Mrk 231.”
Although Mrk 231 is extremely well studied, and known for its collimated jets, the Gemini observations exposed a broad outflow extending in all directions for at least 8,000 light-years around the galaxy’s core. The resulting data reveal gas (characterized by sodium, which absorbs yellow light) streaming away from the galaxy center at speeds of over 1,000 kilometers per second. At this speed, the gas could go from New York to Los Angeles in about 4 seconds. This outflow is removing gas from the nucleus at a prodigious rate — more than 2.5 times the star formation rate. The speeds observed eliminate stars as the possible “engine” fueling the outflow. This leaves the black hole itself as the most likely culprit, and it can easily account for the tremendous energy required.
The energy involved is sufficient to sweep away matter from the galaxy. However, “when we say the galaxy is being blown apart, we are only referring to the gas and dust in the galaxy,” notes Rupke. “The galaxy is mostly stars at this stage in its life, and the outflow has no effect on them. The crucial thing is that the fireworks of new star formation and black hole feeding are coming to an end, most likely as a result of this outflow.”
Source: Gemini press release. The paper appears here. See also some galactic merger animations, courtesy of the Harvard-Smithsonian Center for Astrophysics.
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If you’re an early riser, then perhaps you’ve noticed Kepler’s Laws in action? No, it’s not a new Bruce Willis movie, just the inevitable pairing of the waning crescent Moon and shining Venus. As you can see from this great photo taken last month by John Chumack, it happens as regular as clockwork… and it’s about to happen again. But what is it about such pairings that command our attention? Step inside and find out!
According to the Sky & Telescope press release, the brightest planet and the eerie waning crescent Moon will create an arresting sky scene low in the southeast in the early dawn of Monday, February 28th, and Tuesday, March 1st. “These are the two brightest astronomical objects in the sky after the Sun,” says Alan MacRobert, a senior editor of Sky & Telescope magazine. “They’ll certainly catch your eye, if you look low in the southeast about 60 to 40 minutes before sunrise — weather permitting.”
Venus will be shining to the Moon’s lower left on the morning of Monday Feb. 28th. The next morning Venus will be to the Moon’s right or upper right. Although they look close together, they’re not. Venus is currently 400 times farther away than the Moon. It’s at a distance of 8.8 light-minutes (the distance light takes to travel that far), compared to the Moon’s distance of 1.3 light-seconds. In miles, that’s 99 million miles for Venus and just 249,000 miles for the Moon. (In fact, you may have driven cars enough miles to get to the Moon.) And despite appearances, Venus is 3½ times wider than the Moon’s diameter.
Locator Chart Courtesy of Sky & Telescope Magazine
“Why do people care about this?” asks MacRobert. “Because some people know we need to look up beyond our own little world — and recognize where we are as part of nature, part of the universe. So many of us live our busy little ant-hill lives without ever noticing the gigantic universe beyond the anthill. A lot of people don’t even know you can see alien planets from your driveway while you’re unlocking the car to go to work.”
But just what is it about such a celestial scene that draws our eye like no other? When it comes to our eyes, almost every photoreceptor has one ganglion cell receiving data in the fovea. That means there’s almost no data loss and the absence of blood vessels in the area means almost no loss of light either. There is direct passage to our receptors – an amazing 50% of the visual cortex in the brain! Since the fovea doesn’t have rods, it isn’t sensitive to dim lights. That’s another reason why the conjunctions are more attractive than the surrounding starfields. Astronomers know a lot about the fovea for a good reason: it’s is why we learn to use averted vision. We avoid the fovea when observing very dim objects in the eyepiece.
“Your eye is like a digital camera,” explains Dr. Stuart Hiroyasu, O.D., of Bishop, California. “There’s a lens in front to focus the light, and a photo-array behind the lens to capture the image. The photo-array in your eye is called the retina. It’s made of rods and cones, the fleshy organic equivalent of electronic pixels.” Near the center of the retina lies the fovea, a patch of tissue 1.5 millimeters wide where cones are extra-densely packed. “Whatever you see with the fovea, you see in high-definition,” he says. The fovea is critical to reading, driving and even watching television. The fovea has the brain’s attention. The field of view of the fovea is only about five degrees wide.” When Venus and the crescent Moon are close to that narrow angle, it signals to the brain, “this is worth watching!”
Let’s pretend we’re a photoreceptor. If a light were to strike us, we’d be “on” – recording away. If we were a ganglion cell, the light really wouldn’t do much of anything. However, the biological recorder would have responded to a pinpoint of light, a ring of light, or a light with a dark edge to it. Why? Light in general just simply doesn’t excite the ganglion, but it does wake up the neighbor cells (as does hooting and screaming while pointing at the morning sky). A small spot of light makes the ganglion go crazy, but the neighbors don’t pay much attention (unless you’re in your pajamas cleaning the snow off your car). However, a ring of light makes the neighbors go nuts (and their dogs) and the ganglion turns off. It’s all a very complicated response to a simple scene, but still fun to understand why we are compelled to look!
