We’re going to try a new experiment with the Virtual Star Party this week. I’m going to post the video live on Universe Today as we start it up. Join us live here, or watch the archive after.
This week we had two active telescopes, from Cory Schmitz and Gary Gonnella. We did a quick tour through the nebula region of the Milky Way, making stops at the Ring Nebula, Dumbbell Nebula, Veil Nebula, Lagoon Nebula, Triffid Nebula, a couple of star clusters and even a galaxy.
If you want to join the Virtual Star Party live, we broadcast every Sunday night when it gets dark on the West Coast of North America. For July 21st, it’ll probably be 9:00 pm PDT/12:00 am EDT. But we’re much earlier in the Winter.
P.S. We’re always looking for new astronomers to join us. If you’ve got a telescope that can broadcast images to your computer, and you’d like to participate, please drop me an email at [email protected], and I’ll help you get set up.
Gennady Borisov, who lives in Naunchniy near the Crimean Observatory in the Ukraine, discovered the comet C/2013 N4 on July 8. He's shown here with his two telescopes. Credit: Oleg Bruzgalov
Ukrainian amateur astronomer Gennady Borisov discovered a brand new comet on July 8 near the bright star Capella in the constellation Auriga. The comet was confirmed and officially christened C/2013 N4 (Borisov) on July 13. At the time of discovery, Borisov was attending the Russian-Ukrainian “Southern Night” star party in Crimea, Ukraine. He nabbed the comet – his first – using an 8-inch (20-cm) f/1.5 wide field telescope of his own design equipped with a CCD camera.
Comet Borisov is the fuzzy spot with a brighter central region in this recent photo. Credit: Oleg Bruzgalov
The new comet is on the faint side, appearing as a small, fuzzy patch of 13th magnitude with a brighter center. To see it you’ll need at least a 10-inch (25-cm) telescope and the fortitude to rise in the wee hours before dawn. The reason for the early hour is Borisov’s location in Auriga, a constellation that doesn’t clear the horizon until shortly before the start of morning twilight. Faintness and low altitude will combine to make Comet Borisov an enticing if challenging object for amateur astronomers.
Animation of Comet Borisov compiled from multiple images. Credit: http://astronomamator.narod.ru/cometes/comet_anim.gif
C/2013 N4 is currently traveling through Auriga not far from the easy-to-spot naked eye star Beta and will slowly brighten as it approaches perihelion – closest point to the sun – on August 20 at a distance of 113.5 million miles (182.7 million km). Unfortunately its elongation or separation from the sun will be slowly shrinking in the coming weeks, causing the comet to drop lower in the sky as it approaches perihelion. Our fuzzy visitor misses Earth by a comfortable 192.5 million miles (310 million km) on August 11. It’s likely Comet Borisov won’t get much brighter than 12th magnitude. Astronomers are still working out the details of its orbit, so it’s possible brightness predictions could change in the near future.
C/2013 N4 (Borisov) tracks through northern Auriga not far from Capella in the coming nights. Positions are shown every 5 days at 3 a.m. CDT. The comet is faint and will require a more detailed chart and telescope to see. Created with Stellarium
Aside from how prominent or not Gennady’s comet will become, the most amazing thing is that he beat the automated surveys to the punch. These days nearly all comets and many asteroids are found by professional astronomers using robotic telescopes hooked up to sensitive cameras and computers. Large areas of the sky are covered each clear night. If a fuzzy, moving object is detected by the computer, astronomers are alerted, follow-up observations are made and the new object receives a letter, number and the survey’s name. That’s why there are a plethora of comets in the past 15 years with names like LINEAR(Lincoln Near-Earth Asteroid Survey), Pan-STARRS (Panoramic Survey Telescope & Rapid Response System), LONEOS (Lowell Observatory Near-Earth-Object Search) and others.
By dint of persistence, a smart plan and a keen eye, Gennady Borisov has made his mark in the sky. For that he deserves a well-deserved congratulations and round of applause!
Amateurs who wish to plot the comet on a star map using a star charting software program can get Comet Borisov’s orbital elements HERE. To follow the latest developments, check out Leonid Elenin’s blog. You might recall it was Elenin in 2010 who discovered famed comet C/2010 X1 (Elenin), blamed for everything from earthquakes to future world catastrophes. Instead, the comet proved so friable, it disintegrated as it approached the sun. Let’s see how Comet Borisov fares.
The LADEE spacecraft awaits spin balance testing, conducted to ensure stability during flight, at NASA’s Wallops Flight Facility in Virginia. LADEE is slated to liftoff from Wallops on Sep. 5, 2013 July 10. Credit: NASA/Patrick Black
NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) Observatory has arrived at the launch site on the Eastern Shore of Virginia at NASA’s Wallops Flight Facility on Wallops Island and is now in the midst of weeks of performance testing to ensure it is ready for liftoff in early September.
The LADEE lunar orbiting probe will be the first planetary science mission ever launched from NASAWallops and the Mid-Atlantic Regional Spaceport (MARS). It will soar to space atop a solid fueled Minotaur V rocket on its maiden flight.
LADEE will blaze a brilliant trail to the Moon during a spectacular nighttime blastoff slated for Sept. 6, 2013 at 11:27 PM from Launch Pad 0B.
LADEE is equipped with three science instruments to gather detailed information about the lunar atmosphere, conditions near the surface and environmental influences on lunar dust.
“LADEE will investigate the moons tenuous exosphere, trace outgases like the sodium halo and lofted dust at the terminator,” said Jim Green, Planetary Science Division Director at NASA HQ, in an exclusive interview with Universe Today.
“The spacecraft has a mass spectrometer to identify the gases, a physical dust detector and an imager to look at scattered light from the dust. These processes also occur at asteroids.”
“And it will also test a laser communications system that is a technology demonstrator for future planetary science missions. It communicates at 650 megabits per second,” Green explained to me.
The couch sized 844 pound (383 kg) robotic explorer was assembled at NASA’s Ames Research Center, Moffett Field Calif., and is a cooperative project with NASA Goddard Spaceflight Center in Maryland.
The LADEE spacecraft awaits spin balance testing, conducted to ensure stability during flight, at NASA’s Wallops Flight Facility in Virginia. LADEE is slated to liftoff from Wallops on Sept. 6, 2013. Credit: NASA/Patrick Black
The spacecraft was then shipped cross country by a dedicated truck inside a specially-designed shipping container – blanketed with protective nitrogen – which insulated the spacecraft from temperature, moisture, bumps in the road and more than a few crazy drivers.
The first leg of LADEE’s trip to the Moon took 5 days. The trans lunar leg will take 30 days.
It’s standard practice that whenever space probes are moved by ground transportation that they are accompanied by a caravan that includes a lead scout vehicle to ensure safe road conditions and followed by engineers monitoring the health and environmental storage conditions.
Technicians are now engaged in a lengthy series of performance tests to confirm that LADEE was not damaged during the road trip and that all spacecraft systems are functioning properly.
“One important preparation about to begin is spin-balancing LADEE,” says Butler Hine, LADEE Project Manager. “During this procedure, the spacecraft is mounted to a spin table and rotated at a high-speed to make sure it is perfectly balanced for launch.”
After all spacecraft systems pass the performance tests, LADEE will be fueled, encapsulated and moved to the Wallops Island launch pad later this summer for mating with the five stage Minotaur V booster stack.
“I’m excited about the night launch because people up and down the Atlantic seacoast will be able to see it,” Green told me.
Looking up the Flame Trench –
LADEE Launch Pad 0B at NASA Wallops Flight Facility in Virginia. Credit: Ken Kremer/kenkremer.comAerial view of NASA Wallops launch site on Virginia shore shows launch pads for both suborbital and orbital rockets. The Antares rocket Pad 0A for missions to the ISS is in the foreground. Suborbital rockets blast off just behind the Pad 0A water tower. This photo was snapped from on top of Pad 0B that will soon launch NASA‘s LADEE orbiter to the Moon. Credit: Ken Kremer- kenkremer.com
Sierra Nevada Corporation's Dream Chaser successfully rolls through two tow tests at NASA's Dryden Flight Research Center in California in preparation for future flight testing
Sierra Nevada Corporation’s Dream Chaser successfully rolls through two tow tests at NASA’s Dryden Flight Research Center in California in preparation for future flight testing later this year. Watch way cool Dream Chaser assembly video below![/caption]
Sierra Nevada Corporation’s winged Dream Chaser engineering test article is moving forward with a series of ground tests at NASA’s Dryden Flight Research Center in California that will soon lead to dramatic aerial flight tests throughout 2013.
Pathfinding tow tests on Dryden’s concrete runway aim to validate the performance of the vehicles’ nose skid, brakes, tires and other systems to prove that it can safely land an astronaut crew after surviving the searing re-entry from Earth orbit.
The Dream Chaser is one of the three types of private sector ‘space taxis’ being developed with NASA seed money to restore America’s capability to blast humans to Earth orbit from American soil – a capability which was totally lost following the forced shutdown of NASA’s Space Shuttle program in 2011.
Dream Chaser commercial crew vehicle built by Sierra Nevada Corp docks at ISS
For the initial ground tests, the engineering test article was pulled by a tow truck at 10 and 20 MPH. Later this month tow speeds will be ramped up to 40 to 60 MPH.
Final assembly of the Dream Chaser test vehicle was completed at Dryden with installation of the wings and tail, following shipment from SNC’s Space Systems headquarters in Louisville, Colo.
Watch this exciting minute-long, time-lapse video showing attachment of the wings and tail:
In the next phase later this year, Sierra Nevada will conduct airborne captive carry tests using an Erickson Skycrane helicopter.
Atmospheric drop tests of the engineering test article in an autonomous free flight mode for Approach and Landing Tests (ALT) will follow to check the aerodynamic handling.
The engineering test article is a full sized vehicle.
Dream Chaser is a reusable mini shuttle that launches from the Florida Space Coast atop a United Launch Alliance Atlas V rocket and lands on the shuttle landing facility (SLF) runway at the Kennedy Space Center, like the Space Shuttle.
“It’s not outfitted for orbital flight. It is outfitted for atmospheric flight tests,” said Marc Sirangelo, Sierra Nevada Corp. vice president and SNC Space Systems chairman, to Universe Today.
“The best analogy is it’s very similar to what NASA did in the shuttle program with the Enterprise, creating a vehicle that would allow it to do significant flights whose design then would filter into the final vehicle for orbital flight,” Sirangelo told me.
NASA’s Dryden Flight Research Center welcomes SNC’s Dream Chaser shrink wrapped engineering test article for a flight test program in collaboration with NASA’s Commercial Crew Program this summer. Winds and tail were soon joined and ground testing has now begun. Credit: NASA/Tom Tschida
Sierra Nevada Corp, along with Boeing and SpaceX are working with NASA in a public-private partnership using a combination of NASA seed money and company funds.
Each company was awarded contracts under NASA’s Commercial Crew Integrated Capability Initiative, or CCiCap, program, the third in a series of contracts aimed at kick starting the development of the private sector ‘space taxis’ to fly US and partner astronauts to and from low Earth orbit (LEO) and the International Space Station (ISS).
“We are the emotional successors to the shuttle,” says Sirangelo. “Our target was to repatriate that industry back to the United States, and that’s what we’re doing.”
The combined value of NASA’s Phase 1 CCiCap contracts is about $1.1 Billion and runs through March 2014.
Phase 2 contract awards will eventually lead to actual flight units after a down selection to one or more of the companies.
Everything depends on NASA’s approved budget, which seems headed for steep cuts in excess of a billion dollars if the Republican dominated US House has its way.
Dream Chaser awaits launch atop Atlas V rocket
The Commercial Crew program’s goal is to ensure the nation has safe, reliable and affordable crew transportation systems to space.
“Unique public-private partnerships like the one between NASA and Sierra Nevada Corporation are creating an industry capable of building the next generation of rockets and spacecraft that will carry U.S. astronauts to the scientific proving ground of low-Earth orbit,” said William Gerstenmaier, NASA’s associate administrator for human exploration and operations in Washington, in a statement.
“NASA centers around the country paved the way for 50 years of American human spaceflight, and they’re actively working with our partners to test innovative commercial space systems that will continue to ensure American leadership in exploration and discovery.”
All three commercial vehicles – the Boeing CST-100; SpaceX Dragon and Sierra Nevada Dream Chaser – are designed to carry a crew of up to 7 astronauts and remain docked at the ISS for more than 6 months.
The first orbital flight test of the Dream Chaser is not expected before 2016 and could be further delayed if NASA’s commercial crew budget is again slashed by the Congress – as was done the past few years.
In the meantime, US astronauts are totally dependent on Russia’s Soyuz capsule for rides to the ISS. NASA must pay Russia upwards of $70 million per seat until the space taxis are ready for liftoff – perhaps in 2017.
“We have got to get Commercial Crew funded, or we’re going to be paying the Russians forever,” said NASA Administrator Charles Bolden at Dryden. “Without Commercial Crew, we probably won’t have exploration.”
Concurrently, NASA is developing the Orion Crew capsule for missions to the Moon, Asteroids and beyond to Mars and other destinations in our Solar System -details here.
Scale models of NASA’s Commercial Crew program vehicles and launchers; Boeing CST-100, Sierra Nevada Dream Chaser, SpaceX Dragon.
Credit: Ken Kremer/kenkremer.comSierra Nevada Corp.’s Dream Chaser spacecraft landing on a traditional runway. Dream Chaser is being developed in collaboration with NASA’s Commercial Crew Program during the Commercial Crew Integrated Capability initiative (CCiCAP). Credit: Sierra Nevada Corp.
Artist concept of a 5 kg CubeSat with CubeSat Ambipolar Thruster (CAT) firing in low Earth orbit. Via Kickstarter.
Cubesats are all the rage these days: they’re usually inexpensive and quick to build and they can tag along on launches already scheduled for other things. We think of cubesats as being almost “disposable” satellites – tiny spacecraft that go into Earth orbit for a short time, do their science and then burn up harmlessly in Earth’s atmosphere. But a team of scientists have a more long-term, long-distance plan for their cubesats. Benjamin Longmier and James Cutler from the University of Michigan want to build cubesats that have tiny plasma thruster engines that could propel them into deep space, maybe even interstellar space.
They have a vision of their plasma-thruster cubesat waving as it speeds past the Voyager spacecraft at the edge of our Solar System.
They are working on what they call the CubeSat Ambipolar Thruster (CAT), a new plasma propulsion system. This thruster technology doesn’t exist all in one piece yet, but Longmeir and Cutler said they could put it together in months, with just a little funding. The CAT plasma thruster will propel a 5kg satellite into deep space, far beyond Earth orbit, at 1/1000th the cost of previous missions.
They’ve begun a $200,000 Kickstarter campaign to help fund their project. Their ideas of what these thruster propelled cubesats could do are mind-bogglingly exciting: flying through the plumes of Enceladus to look for life, studying and tagging asteroids, formation flying through Earth’s magnetosphere to learn more about solar flares and the aurora or just an interplanetary message in a bottle lasting for hundreds of millions of years in orbit around the Sun.
They think they can get a satellite up and flying within 18 months.
“The traditional funding process starts with some seed data, a large government grant and a large number of milestones and gates to go through,” said Longmier in a press release from the University of Michigan. “We’d like to leverage Kickstarter funds to compress that timeline and go from initial seed data to flight in about 18 months, a much faster time scale than is possible with traditional grants.”
The cubesats would be about as big as a loaf of bread and the thrusters – the first of its kind — would use superheated plasma directed through a magnetic field to propel the CubeSat. The duo says that with this technology, exploring interplanetary space and eventually other planets would become faster and cheaper than ever before.
While plasma rockets have been used before, they’ve only been used on big spacecraft like Deep Space 1 and DAWN. Longmier and Cutler are miniaturizing the system. Most of the thruster components have been built and have been tested individually, but they need help through Kickstarter to assemble everything into one compact thruster unit for testing the integrated components in the lab, then in Earth orbit, and then interplanetary space.
They’ve got more info on how the thrusters work on their Kickstarter page.
This graphic shows the view of Earth and the portion of its surface that will be illuminated during the Earth imaging event by the Cassini spacecraft on July 19, 2013. Credit: NASA/JPL-Caltech.
July 19, 2013 will be a day that we should really all try to get along. Isn’t that a noble goal? And you can be a part of it in several different ways. In a special project, the Cassini spacecraft will be taking an image of Earth, from the spacecraft’s orbit around Saturn. Specifically, Cassini will be on the far side of Saturn when it snaps a picture of “us” between 21:27 to 21:42 UTC (5:27-5:42 pm EDT.) Cassini will be in just the right spot that it can “see” Earth, but Saturn will be blocking the glare from the Sun. There will likely be a dramatic view of Saturn and its rings in the foreground, with Earth off in the distance. Our home planet won’t be much more than a few pixels in the image, but it will be “us, …everyone you love, everyone you know, everyone you ever heard of, every human being who ever was,” as Carl Sagan said about the Pale Blue Dot image taken by the Voyager spacecraft.
“It will be a day to revel in the extraordinary achievements in the exploration of our solar system that have made such an interplanetary photo session possible,” said Cassini imaging team leader Carolyn Porco of the Space Science Institute, who had the idea for this special image. “And it will be a day for all of us to smile and celebrate life on the Pale Blue Dot.”
First, while Earth has been imaged before from other distant spacecraft (the famous Pale Blue Dot image and Cassini has taken pictures of Earth before) this is the first time that many of the inhabitants of Earth will know the image is being taken – hence the invitation to smile and wave.
Second, Saturn is now visible in the night sky — bright and shining — allowing us a direct line of sight to smile and wave back. No, we can’t see Cassini, but we know it’s there!
Plus, there’s other special chances to submit your own images – of Saturn, and of Earth, or of yourself in the moments Cassini is taking the image.
Astronomers Without Borders is also sponsoring a special Saturn Observing Program, and they are encouraging people and organizations to either organize a special observing event for July 19 (you can register it as an official event here) or to attend an event near you. You can find TDTES events here. This can be a full-blown observing event with telescopes, or just an excuse to get together with friends to go out and look at Saturn in the night sky.
Curiosity Heading for Mount Sharp, Sol 329. Credit: NASA/JPL-Caltech
As the Martian crow flies, the Curiosity rover has about 8 kilometers (5 miles) to trek until it reaches its science destination of the foothills of Mount Sharp. But there will likely be twists and turns along the way. There could be boulders, pits and sand traps to avoid, as well as enticing science targets to stop and study. Just how will the rover be driven all that way? Are rover drivers “hand-driving” every turn or will Curiosity use its autonomous driving software? A combination of both, says Jeff Biesiadecki, MSL Rover Planner and flight software developer. In the Rover Update video below, he explains how each day’s drive will be planned and executed. The rover team is hoping to make at least 100 meters every day.
The image above shows the lower slopes of Mount Sharp at the end of a drive of about 135 feet (41 meters) during the 329th Martian day, or sol, of the rover’s work on Mars (July 9, 2013). That was the third drive by Curiosity since finishing observations at the mission’s final science target in the “Glenelg” area east of the rover’s landing site. Curiosity is driving to the southwest as it heads to Mt. Sharp.
How long will the drive to Mt. Sharp (Aeolis Mons) take? The MSL team expects it will take nine months to a year with stops for science.
“The mission is discovery driven,” said John Grotznger, who leads the MSL mission. “We will go to where the science takes us.”
An artist's conception of jets protruding from a quasar. Credit: ESO/M. Kornmesser
Understanding the formation of stars and galaxies early in the Universe’s history continues to be somewhat of an enigma, and a new study may have turned our current understanding on its head. A recent survey used archival data from four different telescopes to analyze hundreds of galaxies. The results provided overwhelming evidence that radio jets protruding from a galactic center enhance star formation – a result that directly contradicts current models, where star formation is hindered or even stopped.
All early galaxies consist of intensely luminous cores powered by huge black holes. These so-called active galactic nuclei, or AGN for short, are still the topic of intense study. One specific mechanism astronomers are studying is known as AGN feedback.
“Feedback is the astronomer’s slang term for the way in which an AGN – with its large amount of energy release – influences its host galaxy,” Dr. Zinn, lead researcher on this study, recently told Universe Today. He explained there is both positive feedback, in which the AGN will foster the main activity of the galaxy: star formation, and negative feedback, in which the AGN will hinder or even stop star formation.
Current simulations of galaxy growth invoke strong negative feedback.
“In most cosmological simulations, AGN feedback is used to truncate star formation in the host galaxy,” said Zinn. “This is necessary to prevent the simulated galaxies from becoming too bright/massive.”
Zinn et al. found strong evidence that this is not the case for a large number of early galaxies, claiming that the presence of an AGN actually enhances star formation. In such cases the total star formation rate of a galaxy may be boosted by a factor of 2 – 5.
Furthermore the team showed that positive feedback occurs in radio-luminous AGN. There is strong correlation between the far infrared (indicative of star formation) and the radio.
Now, a correlation between the radio and the far infrared is no stranger to galactic astronomy. Stars form in extremely dusty regions. This dust absorbs the starlight and re-emits it in the far infrared. The stars then die in huge supernova explosions, causing powerful shock-fronts, which accelerate electrons and lead to the emission of strong synchrotron radiation in the radio.
This correlation however is a stranger to AGN studies. The key lies in the radio jets, which penetrate far into the host galaxy itself. A “jet which is launched from the AGN hits the interstellar gas of the host galaxy and thereby induces supersonic shocks and turbulence,” explains Zinn. “This shortens the clumping time of gas so that it can condense into stars much more quick and efficiently.”
This new finding conveys that the exact mechanisms in which AGN interact with their host galaxies is much more complicated than previously thought. Future observations will likely shed a new understanding of the evolution of galaxies.
What's the Most Earth-Like Planet In The Solar System?
Life on Earth got you down? Thinking you’d like to pick up and move to another planet? I’ve got bad news for you. Without protection, there’s no place in the entire Solar System that wouldn’t kill you in few seconds.
You’re looking at scorching temperatures, poisonous atmospheres, crushing gravity, bone chilling cold, a complete lack of oxygen, killer radiation, and more.
The entire Solar System is hostile to life as we know it.
If we had to choose from a range of terrible options, what would be the most Earthlike place in the Solar System?
We would want a world that has a similar gravity, similar atmospheric pressure and composition, protection from radiation, and a comfortable temperature. Just like the Earth.
Let’s look at a few candidates:
The Moon looks good. It’s close and… well, it’s close. It’s an airless world, so you’d need a spacesuit. Low gravity is bad news for your bones, which will lose mass and become brittle. Temperatures range from freezing cold to scorching hot, and there’s no atmosphere or significant magnetic field to protect you from the radiation of space.
While we’re suggesting moons, how about Titan, Saturn’s largest Moon?
It’s only 15% of Earth’s gravity, and the temperatures dip down to minus -179 degrees C; cold enough that it rains liquid methane. Even though the atmosphere is unbreathable, the good news is that the pressure is only a little higher than Earth’s. Which means you wouldn’t need a pressurized spacesuit, just a really, really warm coat.
The gravity of Mars is only 38% the gravity of Earth; and we don’t know what effect a long stay in this gravity would have on the human body. The atmosphere is poisonous carbon dioxide, and the pressure is less than 1% of sea level on Earth. So, you’d better pack a spacesuit. The temperatures can rise as high as a comfortable 35 degrees C, but then plunge down to -143 degrees C at the poles. One big problem with Mars is a total lack of magnetosphere. Radiation from space would be a constant hazard for anyone on the surface of the planet.
Atmosphere of Venus. Credit: ESAPerhaps another planet? How about Venus?
On the surface, it’s right out of the running. The temperature is an oven-like 462 degrees C, with a surface pressure 92 times more than Earth. The atmosphere is almost entirely carbon dioxide, with clouds of sulphuric acid. On the plus side, it has gravity roughly similar to Earth, and a thick atmosphere that would protect you from radiation.
Unfortunately, you’d die faster on the surface of Venus than almost anywhere else in the Solar System.
But… there is a place on Venus that’s downright lovely.
Up in the clouds.
Amazingly, if you rise up through the clouds of Venus to an altitude of 50-60 kilometers, the atmospheric pressure and temperature are the same as on Earth. The atmosphere would still be toxic carbon dioxide, but breathable air would be a “lifting gas” on Venus. You could float around the skies of Venus in a balloon made of breathable air. Stand out on the deck of your Venusian sky city in shorts and a T-shirt, soaking up the sunlight in regular Earth gravity.
Sounds idyllic, right?
So, opinions will vary. Some think Mars is the most Earthlike place in the Solar System, but in my opinion, the clouds of Venus are the place to go.
When too much material tries to come together, everything starts to spin and flatten out. You get an accretion disc. Astronomers find them around newly forming stars, supermassive black holes and many other places in the Universe. Today we’ll talk about what it takes to get an accretion disc, and how they help us understand the objects inside.
And the podcast is also available as a video, as Fraser and Pamela now record Astronomy Cast as part of a Google+ Hangout (usually recorded every Monday at 3 pm Eastern Time):
