While "Mars Science Laboratory" is a fairly descriptive name for a rover - it is going to be on Mars to do Science with its on-board Laboratory, it is pretty dry and not that exciting. Too come up with a new name, NASA held a nationwide contest for suggestions, and now you can vote for which name you like here starting today until March 29th. This poll is non-binding, much to the chagrin of Stephen Colbert, I'm sure (though I personally kinda like the sound of "Mars Truthiness Rover" but that is just me). Enjoy!
Monday, March 23, 2009
Friday, March 20, 2009
This February, the Hubble Space Telescope took a picture of four moons of Saturn passing in front of their parent planet which can be seen here and here. Such events are rare, and only happen when the tilt of Saturn's ring plane is nearly "edge on" as seen from Earth. Enjoy!
NASA has recently produced a "unique 'spherical' movie" (their words, not mine) showing how the ice and snow cover of the Earth changes over time as imaged by NASA spacecraft. This movie is called "Frozen," 12-minutes long, and meant to view on a six-foot sphere which has been installed in more than 30 locations around the world. For more information about "Frozen," including a list of locations showing the film, go here. Enjoy!
Cut-and-paste directly from their press release:
NASA scientists will reveal new information and images about our sun and its influence on Earth and the solar system for Sun-Earth Day, recognized each year in conjunction with the spring equinox. The highlight of this year's celebration is a webcast for students and teachers around the world, beginning at 10 a.m. PDT (1 p.m. EDT), Friday, March 20.
This year's theme, "Our Sun, Yours to Discover," celebrates the International Year of Astronomy and emphasizes daytime astronomy. During the live, interactive event, participants from around the world and NASA scientists will share new discoveries and visualizations about our sun. Participating students will have the opportunity to demonstrate personally designed sundials, while others will be monitoring the sun and preparing their own space weather forecast.
"Tremendous strides have been made with satellite and ground-based observations of the sun, which have enabled us to monitor the sun to gain a better understanding of the processes that govern its influence on our solar system," said Eric Christian, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.
Sun-Earth Day is a celebration of the sun and how it affects life on our planet and the space around Earth, known as geospace. For the past nine years, NASA has sponsored and coordinated education and public outreach events for Sun-Earth Day that highlight NASA heliophysics research and discoveries. NASA's goal is to use celestial events to engage the public and students in kindergarten through 12th grade via webcasts, podcasts, space science activities, demonstrations and interactions with space scientists.
"These events also support the spirit of international collaboration," said Lou Mayo, project manager at Goddard for Sun-Earth Day 2009. "We are excited about sharing the latest discoveries about our sun and encourage others to join our quest for a greater understanding of our closest star."
Goddard is producing the Sun-Earth Day webcast. NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the Adler Planetarium in Chicago also are participating in the broadcast. NASA Television and the agency's Web site will broadcast the event live. For NASA TV streaming video, downlink and scheduling information, visit: here. For more information about Sun-Earth Day, visit: here. For more information about NASA's Education programs, visit: here.
Thursday, March 19, 2009
Over the past few months, I've done my best to explain what Astronomers believe is going on in the universe. An equally interesting and difficult question is how did the universe get to be the way it is, and that is focus of the very-delayed-but-finally-posted February 18th episode of this radio show. Thanks a lot for listening!
Tuesday, March 17, 2009
Previously available here, below is a description of the January 21st episode of this radio show, where I try to describe the current thinking (and many questions) on how galaxies formed:
- Galaxy Formation: Pretty much every galaxy is believed to have a super-massive black hole (SMBH) at its center, but is unclear if the galaxy formed before the SMBH or vice versa. Recent radio observations of distant galaxies suggest that the SMBH formed first, and then the galaxy around it (link), though recent optical observations of other distant galaxies suggest the opposite. As matter falls into the SMBH, it heats up and radiates a lot of energy, which is absorbed by the surrounding gas, causing it to heat up and possible decreasing the amount of future gas will fall into the SMBH. This process was originally believed to be very sporadic and violent, but recent evidence suggests this process may be gentler in some galaxies (link). Most galaxies are either spiral galaxies currently forming stars (like the Milky Way, referred to as "blue spirals" because young, massive stars cause the galaxy to appear bluish) or elliptical galaxies consisting almost entirely of old stars (referred to as "red ellipticals" or "red, dead galaxies" which old, low mass stars give the galaxy a red color). A population of red spirals do exist, and are either cases where the spiral galaxy ran out of gas and dust to form new stars, or have so much gas and dust that the blue light produced by young, massive stars is absorbed and the galaxy appears red (link). Galaxies where a lot of material appears to be falling into (a process astronomer call "accretion") the SMBH are often referred to as AGN, or "Active Galactic Nuclei." Discoveries of AGN with the Swift telescope have found differences in the types of galaxies that host nearby and distant AGN (link). It is currently believed that the massive (Milky Way-sized) galaxies observed today or the result of smaller, proto-galaxies merging together in earlier times. This process predicts that the relationship between different current properties of a galaxy (e.g., its size, mass, total light output, gas content) is complicated because they are effected differently by the merging process. However, a recent study found that all of these parameters just depend on the mass of the galaxy - which is very puzzling indeed. Even if this is true, there is a wide diversity in the properties of nearby galaxies, and to study this the Hubble Space Telescope has been measuring the properties of individual stars in these galaxies to determine the history of how quickly they formed stars, etc. (link). One feature of spiral galaxies is that some of these appear to have "bars" in the center (like the Milky Way does, actually), while others don't. A recent survey of galaxies done as part of the COSMOS project has found that the fraction of spirals with bars has tripled over the last 7 billion years (link) . It is currently believed that the merger of two galaxies together will lead to a short-lived but intense increase in the rate at which the resultant galaxy forms stars - called a starburst galaxy. If this correct, then astronomers expect that all startburst galaxies should either show morphological evidence for a recent merger, or be in a crowded regions of galaxies where mergers are likely to occur. An exception to this was NGC 1569, but recent Hubble observations allowed a new measurement of the distance to the galaxy, placing it in the midst of 10 other galaxies (link). Starbursts galaxies are a very active area of research since they play an important role in understanding the history of star formation in the universe, and observations of distant galaxies suggests that star formation in the universe peaked ~2 billion or so years after the Big Bang (about 12 billions years ago; link). The rate of star formation in these galaxies is huge, star formation rates as high as 4000 new stars a year (the Milky Way current makes about 10) has been estimated in some galaxies (link).
- News: Op-ed article in the November 24, 2008 New York Times on on-going problems at NASA with astronomy programs and others going over budget. Also in the New York Times, Dr. Aaron Hirsh write a guest column for their "The Wild Side" arguing for "citizen science" - stepping up a widespread data taking and analysis network. Astronomy has some similar networks, e.g. amateur astronomers searching for supernovae and other transient events, and projects like Galaxy Zoo.
- Wednesday Morning Astronomer: In this article, Gregg Easterbrook speculates that the excess of radio emission from deep outer space is the sound of interstellar war (No. Radio waves are actually light, not sound waves), and discusses recent observations of the Sun's motion around the center of the Milky Way that suggests the inner part of the Milky Way has 50% more mass than previously thought. One reader writes in that this was discovered using a simple method - which is very true, but very hard to do precisely.
- Calendar of upcoming Astronomy/science events in the greater Poughkeepsie/New York City area. Galaxy Formation (continued): As I mentioned earlier, the merger of galaxies is believed to be the most important process in producing the galaxies we see today. Not surprisingly, what happens when two galaxies merge is very complicated, and much of our current understanding comes from studying the Antennae Galaxies - the nearest example of a galaxy merger. Recent observations of this pair of interacting galaxies change the distance from 65 million light-years to 45 million light-years, important in measuring the properties of these galaxies (link). A recent survey of interacting galaxies suggest that all galaxies have undergone a "major merger" in the last 6 billion years, and the peak in the merger rate of galaxies corresponds with the peak of the fraction of starburst galaxies in the universe - suggesting a link between the two. Evidence for a recent merger in a very distant galaxy has been uncovered thanks to gravitational lensing - which makes this galaxy appear much brighter than it ordinarily would (link). New observations suggests that SMBH were common inside galaxies 12 billion years ago, based on observations of two colliding galaxies at this time (link). The merging of two galaxies is also believed to drive gas towards the center of the galaxy, where it falls into the SMBH - creating a Seyfert galaxy. If so, the distribution of hydrogen gas inside such galaxies show evidence for being disrupted by such a merger - and they do (link). I said before that the merger/collision of two galaxies can lead to a period of intense star formation. Well, there is evidence that in some cases, this actually can cause star formation to stop (link). Additionally, the energy radiated by gas falling into the SMBH triggered by a galaxy merger/collision can also stop star formation in the outer part of the gas (link). Not just galaxies can merge / collide, this happens to galaxy clusters as well, and one example of a colliding galaxy cluster is surrounding by a diffuse haze of very low frequency radio emission (link). These collisions may also explain the existence of the magnetic field which exists in the void between galaxies inside galaxy clusters. (article)
Sunday, March 15, 2009
Long available here, below is a description of the January 7th episode of the radio show, where I continue the "Tour of the Universe" with a description of the Milky Way:
- Galactic Center and Galactic Plane - At the very center of the Milky Way, there is believed to a black hole which has a mass approximately a million or so times that of the Sun called Sgr A*. Pretty strong evidence for the existence of such an object comes from studying the orbit of stars very close to Sgr A* (link). Measuring the mass of similar black holes believed to be at the centers of other galaxies is much more difficult since there you can't resolve the orbits of individual stars. Other methods which have been proposed are the tightness of their spiral arms (link), the temperature of the hot, X-ray emitting gas surrounding the galaxy (if it is a galaxy without much ongoing star formation; link). Surrounding Sgr A* is a disk of stars including the Sun, referred to as the Galactic Plane. They stars orbits Sgr A*, and a new, precise measurement of the rotation of stars in the Milky Way was recently made using a particular class of pulsating stars called Cepheids - which have also been used to measure the distance to other galaxies (link). The spiral arms in the Milky Way are not believed to concentration of particular stars, but where a significant number of stars are born "at once" - which is why they appear brighter than other parts of the Milky Way and contain a vast majority of the most massive (and therefore, very short lived) stars in the Galaxy. There is evidence that our Sun has traveled a considerable distance from its birth site in the Milky Way. Since young stars are clustered along spiral arms, and young, massive stars are the dominant source of ultraviolet radiation in a galaxy, ultraviolet images like the one the Swift satellite recently made of M33 (link), are good ways of studying the spiral structure in a galaxy. Spiral arms, and other features of the galactic disks make the results of gravitational interactions between galaxies (link). The Milky Way also contains clusters of stars, the densest and oldest of which are called "globular clusters", which are believed to be stars formed at the same time out of the same cloud of gas. A recent study of the a particular globular cluster measured its age using three different methods and got three different answers - a bit of a puzzle (link). As discussed on a previous show, the most massive stars in the Milky Way are believed to end their life in a supernova explosions, which actually plays a very important role in the properties of the gas which fills the Galactic plane of the Milky Way. Recent Chandra and Very Large Array observations have discovered the remnant of the most recent supernova explosion in the Milky Way, believed to have occurred only 140 years ago (link). The material released in these explosion expand with a very high velocity, heating the surrounding gas to very high temperatures and compressing into a thin shell of material which make for lovely Hubble images - and very interesting science (link). The hot gas and cosmic rays produced in the interaction between the material ejected in a supernova and its surrounding might explain the flow of gas out of the Milky Way's Galactic Plane, and carve bubbles out of nearby cold gas as observed in the Tarantula Nebula in the Large Magellanic Cloud (link). This is believed to explain why clusters of young stars are often surrounding by "holes" in gas, though this is not the case for nearby dwarf galaxy IC 2574. In most galaxies like the Milky Way, ionized hydrogen is only found in the center of these galaxies, most likely the result of star formation occurring only in certain regions and not distributed uniformly around a galaxy (link). Spitzer observations of a nearby spiral galaxy M101 shows that organic molecules are only present towards its center and not its edges (link; image. In the Milky Way, most star formation is currently taking place near the center of the galaxy, but not so in M83 where GALEX recently observed star formation at the outer edge (link)
- Wednesday Morning Astronomer: I understand and don't necessarily disagree with his point in this article, but astronomers did not "cavalierly" come up with the idea of Dark Matter - it was first proposed to explain some observations in the 1930s I believe, did not gain acceptance for at least 30 years, and still bothers many people, dark matter has been "located" (though not yet explained), the every controversial "dark flow" observed in distance galaxy clusters might be due to an unknown force, but not one outside our universe but one important on distances greater than the speed of light times the age of the universe which defines the "observable universe." I know that is pretty subtle, but it is an important distinction.
- Calendar of upcoming Astronomy/Science events in the greater Poughkeepsie/New York City area.
- Globular Clusters and Galactic Halo: Outside the Galactic Plane there are dense concentrations of millions of old stars referred to as globular clusters. Recent observations suggest that, even though they are "only" 9-13 billion years old, the structure of stars inside globular clusters is still evolving (link). It is though the some globular clusters are actually the remnants of the centers of dwarf galaxies which have been absorbed by the Milky Way. Since such galaxies are also believed to have black holes at their center, the presence of a massive black hole (much more massive than the Sun) might be proof this occurring. Such a black hole might have been found in globular cluster Omega Centauri (link), which - unlike other globular clusters - also contains dust (link). A similar process might explain the large number of globular clusters in M87, the giant elliptical galaxy in the center of the Virgo cluster - it "stole" them from lower mass galaxies which got too close (link). By measuring the velocity of the stars in the halo of the Milky Way, the diffuse "cloud" of stars which surrounds the Galactic Plane, it is possible to estimate the total mass of our galaxy. A recent such measurement suggests a lower mass than previously estimated (link). How the Milky Way's halo got there is an open, and interesting question. The two possibilities are that the stars formed out of the same cloud of gas that collapsed to form the Milky Way, or that it is the remnants of galaxies which have merged into the Milky Way. Recent studies of the structure of the halo suggest the second possibility, as do the presence of streams of stars in the halos of two nearby galaxies (here). It is expected that there are stars in the vast empty space between galaxies, and astronomers are searching for them (link). Last, but not least, it appears that most of the mass of galaxies is not in stars, gas, or dust, but in "dark matter" - this mysterious stuff that has mass but doesn't seem to produce light. Dark Matter is present in the dwarf galaxies which orbit the Milky Way - in fact, one of these has the highest ratio of dark to "normal" matter of any known object (link), and the galactic plane might be enclosed in a larger disk of dark matter(link). The distribution of dark matter in a galaxy is not expected to be entirely smooth but contain clumps and streams (link) which might be measurable using the motion of nearby stars in the night sky. An alternative to dark matter is the Newton's equation for gravity is wrong on very large distances (called MOdified Newtonian Dynamics, or MOND), which can do a good job reproducing the orbit of dwarf galaxies around the Milky Way (link). There are many fewer known dwarf galaxies around the Milky Way than expected, a problem for our current understanding of galaxy formation, though possible solutions have been suggested (link)
Friday, March 13, 2009
Over a month after it first aired, here is the February 11th radio show on cosmology, where I discuss why astronomers think the universe is mostly composed of dark matter and dark energy. Hope you enjoy and, as always, please leave below or email me any questions, comments, or concerns you might have. Thanks for listening!
Wednesday, March 11, 2009
Long available here, below is a description of the December 31st episode of this radio show, where I discussed the major Astronomical results to come out in December 2006. They were:
- Solar System News: Recent powerful solar flare produced both neutral and charged particles, first time neutral particles detected from such an event; ESA's Venus Express detects hydrogen leaving Venus's atmosphere from the day-side for the first time - gas appears to be result of water being broken down into hydrogen and oxygen in upper atmosphere, and might explain why there is so little water on Venus; NASA's THEMIS satellites detect the opening of a large hole in the Earth's magnetic field due to the interaction with a clump in the solar wind; NASA instrument on India's Chandrayaan-1 Lunar spacecraft measures changes in chemical composition of lunar surface on small physical scales (link, image); next NASA mission to the Moon, the Lunar Reconnaissance Oribter; completes major milestone before April 2009 launch (website); evidence for climate change on Mars resulting from regular changes in the tilt of its orbit around the Sun - deduced from studying patterns of rock layers in a large crater (link); results from ESA's Mars Express satellite suggests that peculiar light-toned deposits result on ground water bursts onto the surface (link); NASA's Mars Reconnaissance Orbiter completes primary mission (website), releases new 3D images of surface (link), and found evidence for carbonite on Martian surface which requires the past presence of neutral or basic water on Mars's surface (article); evidence that site of NASA's Phoenix Mars Lander is currently going through a "dry" phase; next NASA mission to Mars - the Mars Science Laboratory - delayed until late 2011 due to cost over-runs, delay expected to have implications for future planetary missions; ongoing debate whether future joint NASA/ESA Solar System mission should be to Jupiter's moon Europa or Saturn's moon Titan; recent flybys of Saturn's moon Enceladus by Cassini show continuing activity and of Titan show evidence for volcanos spewing ice in to this moon's atmosphere; Swift satellite detects X-ray emission from Solar System comets (link)
- Wednesday Morning Astronomer: Yes, an ice cream carton hurtling towards the Earth at 99% the speed of light would be a very bad thing (article); no, the astronomical theory for what Voorwerp might be is not an attempt to upstage the Dutch schoolteacher who found it, but is an attempt to understand a still very bizarre object (link); star formation in the universe is actually on a decline, and if the current thinking on the universe is correct, the ultimate fate is a starless night sky - a very depressing prospect indeed (link); and I think it is definitely a good thing that the more we look, the less we understand (link).
- Calendar of upcoming Astronomy/Science events in the greater Poughkeepsie/New York area.
- More News: Evidence that brown dwarfs form like stars not planets (link); up and coming sub-mm radio interferometer ALMA gets its first telescope; astronomers discover the two faintest brown dwarfs known (link); analog to young Sun identified by CoRoT satellite (link); turbulence in proto-planetary disk important in determining how planets form (link); Spitzer images massive stars destroying proto-planetary disks of their neighbors (link); Dutch undergrads discover first extrasolar planet orbiting a fast-rotating star (link); Hubble Space Telescope discovers carbon dioxide in the atmosphere of an extrasolar planet (link) and measure the size of a different extrasolar planet (link); proposal to look for moons around extrasolar planets through the "wobbles" they create in their orbits (link); new technique proposal to look for water in the atmosphere of an extrasolar planet; direct imaging of extrasolar planets is Science magazine's #2 breakthrough of the year; Kepler spacecraft - which will search for Earth-like planets around Sun-like stars - shipped to Florida (just launched last week!!!)
As always, please post below or email any questions, comments, or concerns you might have. Thank you for listening!
Tuesday, March 10, 2009
Ever wonder what the view from the International Space Station looks like? Thanks to a new onboard webcam camera you can see for yourself between 1 p.m. to 1 a.m. CST. To check it out, go here. Enjoy!
I'm really sorry for the lack of posts lately, especially the large delay in putting up recent radio shows as well as descriptions of past ones. Between a death in the family and work, I've fallen quite a bit behind. Thank you for your patience...
Posted by You'd Prefer an Astronaut at 12:58 PM
Wednesday, March 4, 2009
The next space shuttle is scheduled to launch on March 12th, and during the NASA TV broadcast covering the launch, the commentators will be answering questions submitted by you (and lots of other people around the globe)! If you have a questions you would like answered on air, go to
http://webcast.ksc.nasa.gov. Discovery and its seven astronauts are tentatively targeted to launch March 12 at 8:54 p.m. EDT from NASA's Kennedy Space Center in Florida. NASA commentary will begin about five hours before liftoff. For more information about the STS-119 crew and mission, go here. Good luck!