Interview with Prof. Mary Crone Odekon (Skidmore College)

Available here is my interview with Prof. Mary Crone Odekon of Skidmore College, which was originally broadcast on the January 14th episode of this radio show. I apologize for the bad sound quality during parts of this interview - I recorded them using an extension to Skype, which for some reason has been giving me grief lately. For more information on her research, check out her web page and the web page of the ALFALFA project, of which she is a member, which even has a blog! If you have any questions, comments, or concerns, please email me or leave them below. Thank you very much for listening!

NASA technology and the Presidential Inauguration

Using the same technology that produces those amazing panaromic pictures of Mars from data taken by NASA's rovers, a photographer at the presidential inauguration, David Bergman, created this image from 220 different images. For more information on how this picture was put together, read this NASA article. Hope you enjoy!

Want to help choose where Hubble points next?

NASA has identified six interesting targets for the Hubble Space Telescope to look at, and is sponsoring a public vote here until March 1 to determine which one will be observed. As you might imagine, this is a rather large departure from how they normally determine which objects Hubble looks at, one where astronomer submit proposals where less than one-in-ten are approved for actual observations.

I'd personally vote for Arp 274 or NGC 5172, but that's just me. As we say in my hometown (Chicago), vote early and vote often! (and if you're dead, vote twice for good measure.)

January 14th Radio Show: Galaxies and Galaxy Formation

Finally available here is the January 14th episode of this radio show, feature an interview with Prof. Mary Crone Odekon of Skidmore College on using galaxies to study galaxy formation. Hope you enjoy, and sorry it took me more than two weeks to post it...

Past Interview: Dr. Tod Strohmayer (NASA/GSFC)

As a compliment of the description of the December 3rd radio show on black holes, here is my interview with Dr. Tod Strohmayer of NASA's Goddard Space Flight Center. The original post, with links to his webpage and other resources, is located here.

Description of December 3rd Radio Show: Black Holes

Long available here, below is a description of the 2008 December 3rd episode of this radio show with focused on black holes. On this program, I discussed the following:

• Black Holes: Black Holes are objects believed to be so dense that light can not escape if it gets to close (i.e., past the "event horizon"). Additionally, its gravity is so strong that material that makes up a black hole can not arrange itself into a structure that can withstand its own gravity, so this material is thought to collapse into a point. But if one can't see too close to a black hole, how does one know? Well, it the above is correct, that black holes should not have a surface, unlike a neutron star. If a neutron star or a black hole is close enough to a normal star, its gravity is so strong that it will rip material off the surface of the normal star and cause it to fall on itself. This process is called "accretion", and as discussed previously on this radio show by Dr. Tod Strohmayer, this has process have been observed for many neutron stars and black hole candidates. In the case of a neutron star, this material will pile up on the surface of the neutron star, and this pile will got hotter and denser until it is so hot and dense that the hydrogen in this material fuses into helium, releasing a burst of heat and light which is observable by X-ray telescopes such as the Rossi X-ray Timing Explorer. One would not expect such bursts from material falling onto a black hole - which is more massive than a neutron star - since their is no surface for the material to collect. These X-ray bursts have been detected from neutron stars (for example this link), but not from any black hole candidates. Therefore, even there seems to be evidence that black holes indeed do not have surfaces. Additionally, black holes appears to have a mass either a few times that of the Sun (called "stellar-mass black holes"), or millions to billions times that of the Sun - like the black hole believed to reside in the center of our galaxy, the Milky Way (called "super-massive black holes"). Why there seems to be a lack of black holes with a mass between these two extremes (for example, a thousand solar masses) isn't known. One possibility is that such black holes exist, but reside in the middle of globular clusters where they would be hard to detect. A recent survey of globular cluster RZ2109 did not find such a black hole, suggesting that if this was correct they are extremely rare (link). Studies of the super-massive black holes suggest that their may be an upper-limit to how massive they can be, around 10 billion times that of the Sun (link). Since black holes do not have any structure, they are often thought to be some of the simplest objects in the universe (really!) - according to Einstein's theory of General Relativity, in order to completely describe the properties of a black hole you need to know its mass, its spin, and its electric charge (and real black holes in the universe and expected to have zero electrical charge). If so, stellar-mass black holes and super-massive black holes should accrete matter the same way - as observed for black holes in the nearby galaxy M81 (link). As mentioned before, it a normal star passes too close to a black hole, the black hole's gravity will cause material from the star to fall towards, and eventually fall inside, the black hole. As this material falls towards the black hole, it gets hotter - so hot that it produces a lot of X-rays. By looking at the periodic flickering of this light, it is possible to estimate the mass of the black hole. This was recently done for one black hole in the Milky Way, at they estimate a mass of just 3.8 times that of the Solar Mass, the lowest mass black hole known (link). Periodic flickering has also been observed from the super-massive black holes in the centers of other galaxies, and can be used to estimate their mass as well. This was done for galaxy RE J1034+396, which has a mass a million times that of the Sun (link). What causes the light from gas falling into a black hole to flicker is not known, but a recent study of the visible light flickering and X-ray light flickering from a Galactic black hole suggests that its magnetic field plays an important role (link). As mentioned before, there is a super-massive black hole in the center of our galaxy called Sgr A*, and material falling into this black hole also produces regular flares of light (link). In fact, there is evidence that, around 300 years ago, it produced a flash of light so bright that today we are seeing some of the light reflecting off molecular clouds near the Galactic center (link). A major goal of astronomers today is to make an image of light coming from the event horizon around a black hole. The best chance to do this is using radio telescopes to observe Sgr A*, and radio astronomers have gotten down to only 3 times the expected size of the event horizon (link 1, link 2). It is possible to use to orbits of objects around black holes to test general relativity (GR), just as one does this with neutron stars. This was recently done for the two black holes believed to be orbiting each other in center of galaxy OJ 287, and the time between the closest approach of these two black holes agreed with what GR predicts. The material that flows into a black hole is believed to form a disk (called an "accretion disk") around the black hole before it passes the event horizon. Quasars are believed to be galaxies where the optical light of this disk shines much, much brighter than all the stars in the rest of the galaxy. If so, the spectrum of the quasar - how bright the quasar is at different colors - should resemble that of a disk. This is hard to measure in great detail since the light at some colors is absorbed by material between the Earth and the galaxy, but a recent study suggests that it does (link). Additionally, for some unknown reason, the presence of gas flowing into the black hole is often associated with the presence of gas flowing AWAY from the black hole with very high velocities (>60 million mph). Astronomers at UCSC and University of Florida recently observed this outflow turn on around a quasar (link). Sometimes this very collimated outflow (called a "jet) is pointed directly at the Earth, in which case the galaxy is called a "blazar." Recent radio observation of a blazar suggest that these jets are powered by the magnetic field of the black hole (link). Quasars come in very different varieties, with one class recently observed to produce many more X-ray than previously thought to be possible (link). The presence of very, young stars around super-massive black holes like Sgr A* strongly suggest that stars can form in the accretion disk around them (article, link 1). Optical observations of these accretion disk have also detected weird optical filaments around them, suggesting this gas is confined by a weak magnetic field possibly generated by the black hole (link). While all galaxies are currently thought to have a super-massive black hole in their center, very few galaxies are quasars. Why some galaxies are quasars are most are not is unknown, but it is though that quasars are the result of two galaxies recently merging together.
• Calendar of upcoming Astronomy / science events in the greater Poughkeepsie / New York City area.
• Wednesday Morning Astronomer:
• News:

Asteroid Flyby Today

Today, newly-discovered asteroid 2009 BD is slowly passing the Earth at a distance of only 400,000 miles away. This asteriod is thankfully too small (approximately 10 meters wide) to pose a threat, but is interesting because its orbit appears to be almost identical to the orbit of Earth - a rare event. For more information of this asteroid, and information on where to see it on the sky, visit spaceweather.com. Enjoy!

Solar Eclipse on Monday, 2009 January 26

Unfortunately, it is not a total eclipse, and is only visible from Indonesia, Australia, South-East Asia, and part of Southern India and South Africa, but the Moon will cover "just" 93% of the Sun, producing a rare sight - for those lucky enough to see it called an annular "ring of fire." Go to spaceweather.com for more information, and hope you get a chance to see it!

Past Interview: Prof. Allyson Sheffield (Vassar College)

Already available, here is my interview with Prof. Allyson Sheffield of Vassar College on her research on determining the origin of the "thick disk" of the Milky Way. I didn't get a chance to discuss this on my January 7th radio show where I covered the Milky Way, so I thought it might be of interest. Hope you enjoy!

Name NASA's next Mars rover (Competition)

NASA is currently hosting a competition to rename its next rover to Mars, currently called the Mars Science Laboratory. This contest, in partnership with Disney-Pixar's WALL-E, is open to students 5 to 18 years old and enrolled in a U.S. school (not necessarily a US citizen). You must submit an essay explaining why your name is a good fit, and entries will be accepted until
midnight Jan. 25. For more information, go here. Good luck!

Icicles and Rockets

I know rockets are very, very hot, and icicles only form when it is very, very cold, but check out this video from NASA on why icicles and rockets can go together in some circumstances. Read this article for more information, and hope you enjoy!

Mars Rover Birthday Party

To celebrate NASA Mars rovers Spirit and Opportunity's 5th anniversary on Mars, JPL in Pasadena, CA is sponsoring a slew of public events in late January to honor this accomplishment. Go here for more information on these events. In addition, JPL has put up two new videos on the accomplishments of these two rovers. Enjoy!

January 7th radio show: The Milky Way

Now available here is the January 7th episode of this radio show, where I do my best to describe and cover all the latest news of the different components of the Milky Way - starting with million solar mass black hole at the center to the diffuse, large "halo" of stars which surrounds the Galactic disk where the Sun resides. Hope you enjoy, and as always, any and all feedback is appreciated. Thank you for listening!

Comet Lulin approaches

Discovered in 2007, Comet Lulin (C/2007 N3) is currently approaching Earth as it orbits the Sun, and should make its closest approach in February - at which time is should be bright enough to be seen with the naked eye. Go to spaceweather.com for more information on seeing this comet.

Comic Strip on Stars

Hope you enjoy this comic strip below. I also don't recomment swinging on a star...

Biggest Full Moon of the Year...

... will be this weekend. Go here to read why this is not just an optical illusion. Hope you get a chance to see it!

Hubble Images of Runaway Stars

Just like a jet plane flying supersonically, when a star moves through the surrounding gas faster than the speed of sound in that gas, it creates a shock wave called a bow shock. Though rare, there are stars that do this, and the Hubble Space Telescope has recently released beautiful images of 24 such stars, available here. Enjoy!

Description of November 19th Radio Show: Supernovae and Gamma-Ray Bursts

Long available here, below (finally) is the description of the November 19th episode of this radio show, devoted to supernovae and Gamma-Ray Bursts (GRBs). On this program I discussed:

• News: SHIMMER spacecraft observes second season of Polar Mesospheric Clouds, the highest clouds on Earth (link); Chandrayaan-1 Lunar Spacecraft reaches final orbit around the Moon, successfully impacts lunar surface with probe (link); Martian dust storm cuts energy supply on NASA's Mars Rover Spirit (link), but it is still communicating with the Earth (link); recent European conference discussed how life formed on Earth and maybe could have formed on Mars (link); Cassini discovers new, weird aurorae on Saturn (link); Hubble Space Telescope directly images planet around another star - first time ever done! (link), another extra solar planetary system similarly imaged using Keck Observatory (link); International Space Station celebrates 10th anniversary, receives payload of spiders and butterflies (link), a camera to observe crops in the Great Plains and Rockies, and a device to recycle human liquid waste (link); NASA design for new Ares rocket passes review, receives hardware for upcoming test flight of rocket's first stage; NASA restores historic picture of Earth rising above the Moon, available here; NASA tests new Lunar Rover concepts in Hawaii; rocket launched to study effect of Northern Lights on radio communications (link); NASA's Orbiting Carbon Observatory arrives at launch site; 'sun shield" designed for James Webb Space Telescope, NASA's successor to Hubble (link); first "pico satellites" (very small satellites) beign designed and built at University of Florida (link); ESA ministers meet to determine their objectives for upcoming years; Czech Republic becomes 18th member state of ESA; Doug Cooke appointed next NASA Associate Administrator for Exploration Systems; ESA sponsors development of "Health Early Warning System" in Africa; NASA introduces Endeavor Science Teaching Certificate program (link).
• Calendar of upcoming Science / Astronomy events in the greater Poughkeepsie / New York City area.
• Supernovae and Gamma-Ray Bursts: As massive stars age, they run out of lighter elements like Hydrogen and Helium to fuse together to produce energy, and end up with a core full of Iron. Since energy is not released when Iron fuses together, there is no energy source to prevent the core from collapse under its own gravity, so it collapses. As it does so, it releases a lot of energy (much much more energy than the Sun will release in its lifetime), creating a shock wave that moves through the outer part of the star - heating it up and eventually causing it to explode. Light from the hot gas behind this shock is trapped until the shock wave leaves the star, causing a flash of light called "shock breakout." This flash was observed for the first time from a supernova SN2008d (link 1, link 2), an important confirmation for how astronomers think massive stars explode. Analysis of archival data indicated that shock breakout was observed from another supernova (article, link). After this shock exits the star, the star explodes. The stellar material is initially so hot and dense that it forms heavy nuclei, like Nickel 56, whose radioactive decay powers optical light for days - months after the explosion. The spectrum of this light, and the way its brightness (luminosity) changes with time, provides pretty much the only available information on the type of star that exploded and how it did so. Thanks to dust clouds reflecting this light - through a process called "light echos", this emission has been seen from the supernova which created the Cas A supernova remnant (SNR) - confirmed that this explosion was from the core-collapse of a massive star (article, link), and maybe reflection emission from the shock breakout of this explosion has also been detected (link). Light echos from past supernova explosions have detected from many supernova remnants in the Large Magellanic Cloud (link), where they are actually easier to see than in the Milky Way due to the lack of dust in that dwarf galaxy. As I mentioned before, the light from these explosion is powered by the radioactive decay of Nickel-56, which scientists have made in the lab for the first time recently (link). Two clusters of Red Supergiant Stars, likely to produce lots of supernovae in the "near" future, discovered in the Galactic Bar of the Milky Way (link). By looking at "before" and "after" pictures of nearby galaxies which have supernovae, it is possible to identify the star that exploded. This was done for a supernova in NGC 6946, and the exploding star had a mass close to the minimum mass believed to be required for a core-collapse supernova, about 10 times that of the Sun. Stars can also explode if they come to close to a black hole, whose gravity will literally rip the star apart and cause it to explode (link). Similar to NGC 6946, an exploding star was identified in nearby galaxy NGC 2397, which also had a "low" mass for this type of event (link). A supernova similar to SN 1987a which occurred in the Large Magellanic Cloud and is, by far, the best observed supernova ever, is identified (SN 1996cr, link). It has been suggestsed that supernovae whose energy output is much higher than "normal" might produce an ultra-dense object called a "quark star" instead of a neutron star (link). By studying the spectrum of the optical light produced in these explosions, astronomers have found evidence that the explosions are not symmetric. It has also been speculated that SN 2008d, the supernova with the shock breakout, might be a gamma-ray burst (GRB) - a rare class of supernova which produced a narrow beam of gamma-rays - where the gamma-rays were not pointed towards the Earth, though this is highly controversial (article, link). One of these GRBs, GRB 080319B, produced a flash of visible light so bright it could be seen with the naked eye, believed to be the result of this jet of gamma-rays pointed directly towards the Earth (link). Integral satellite detects low-power GRBs. Current satellites are able to see GRBs from the time the first stars formed after the Big Bang, but don't, suggesting these stars when they exploded did not produce GRBs. The galaxies which host long GRBs (the ones produced by exploding stars) tend to be low mass, contain a relatively small amount of metals, while the host galaxies of short GRBs aren't as specific - suggesting two different of objects create these two different classes of GRBs. The properties of the stars that produce long GRBs can be estimated from the X-ray emission observed during and after these explosions (article). Origin of short GRBs still unknown, though there are several suspects.

Thank you very much for listening, and your patience, and hope you enjoyed this show. As always, please email or post below any comments, questions, or concerns you might have.

December 31st Radio Show: Latest Astronomy News

Available here is the December 31st radio show, where I discussed most of the Astronomy news which occurred during the three weeks I was away. Hope you enjoy and, as always, please email me or leave below and questions, comments, or concerns you might have. Thank you for listening!

Supernova Remnant Movie

Using data taken by the Chandra X-ray Observatory, astronomers have been able to observe both the expansion of the Cas A supernova remnant as well as determine its three-dimensional structure. Go here to see the expansion and time variability of this remnant, and here to see its 3D structure. Enjoy!

James Webb Space Telescope website

NASA has just unveiled a new website for the under-construction James Webb Space Telescope (JWST), its successor to the Hubble Space Telescope. For more information on JWST (astronomers and government agencies share a love of acronyms), I encourage you to listen to this interview with Dr. Mark Clampin on NASA's Goddard Space Flight Center, one of the project scientists on JWST. Enjoy!

Hubble Image of the Galactic Center

The near-infrared camera on the Hubble Space Telescope recently took this picture of the Galactic Center, and it looks absolutely gorgeous. For a zoomable version of this image (which is definitely worth looking at), go here. Enjoy!

First Meteor Shower of 2009

Courtesy of spaceweather.com:
"The annual Quadrantid meteor shower peaks on Jan. 3rd when Earth enters a stream of debris from shattered comet 2003 EH1. The timing of the encounter favors observers in western North America and across the Pacific Ocean who could see dozens to hundreds of meteors during the dark hours before sunrise this Saturday morning. Visit http://spaceweather.com for a sky map and more information."

2009: International Year of Astronomy

To honor the achievements of Galileo (I think), 2009 has been declared the "International Year of Astronomy," which plans for public events around the world to celebrate and increase people's knowledge on what we think is going on in the cosmos. To celebrate this, Nature magazine has devoted an entire issue to the past and future of astronomy. The articles are quite good and pretty interesting, go here if you want to read them for yourself. Hope you enjoy!