Well, killer to satellites. They make pretty sheets of light when they hit the atmosphere. Go here to read more. Enjoy!, and watch out?
Wednesday, March 31, 2010
Tuesday, March 30, 2010
Monday, March 29, 2010
In general, it is believed that galaxies form hierarchically: small galaxies formed first, and then these merged into larger ones, which merge into larger ones, etc. As a result, all massive galaxies are expected to be found by lots of smaller ones. This is true for the Milky Way, and M31, and lots of other galaxies - but not ESO 306-17, it is all alone? Did all the small galaxies which would normally be around it merge into this one? Go here to find out. Interesting...
Sunday, March 28, 2010
Saturday, March 27, 2010
Since ice reflects radar (radio light waves) differently than solid rock, mapping the surface of something with radar (essentially shining radio waves at it and measuring the reflection) it is an effective way of finding water ice - and a little less destructive then smashing some big thing into the Moon and looking at the resultant dust plume. NASA built such a radar instrument for India's Chandrayaan-1 spacecraft called Mini-SAR instrument, which apparently for more than 40 small craters with water ice. Cool! Go here to read a nice summary of all the different pieces of evidence for water on the Moon.
Friday, March 26, 2010
Read this article to learn how, by studying the smallest galaxies near the Milky Way, astronomers can figure out how stars formed in the early universe. The crux of the star is that the conditions in these galaxies isn't that different from what we believe existed at these early times, but that doesn't mean we understand how stars form in them.
Thursday, March 25, 2010
While almost certainly astrophysical, where they come from seems to be a little more complicated than previously thought. Go here to learn more. Personally, this is what makes science fun for me at least.
Wednesday, March 24, 2010
Though it is now stationary, NASA still plans to put the scientific instruments on Spirit to good use. Go here to read what science it can still accomplish, assuming it doesn't freeze to death during the Martian winter. Keep your fingers crossed...
Tuesday, March 23, 2010
Monday, March 22, 2010
A new 3D IMAX Movie is coming out starring Hubble images (given that Hubble only takes 2D images of the sky, I'm more than a little curious how they add the 3D aspect), which sounds pretty cool. Go here for the details. Enjoy!
One of the Cassini's satellites biggest discoveries that one of Saturn's moons, Enceladus, is ejecting dust and gas into its surroundings - which is possibly responsible for one of Saturn's outer rings. Thanks to a semi-recent flyby of this moon by Cassini, we now know much better where this material is coming from. Go here to read all the details. Enjoy!
Sunday, March 21, 2010
Saturday, March 20, 2010
Astronomers currently believe that when the universe was a billion years old or so (as opposed to the 14 billion years old it is now), it was full of small galaxies which were merging together to form bigger ones - and it was by this process that all of the big galaxies we see today were formed. Wouldn't it be great if we could somehow observe the same thing nearby, so we can study it better? Well, Hubble and GALEX may have discovered such an example. Go here for the details. Enjoy!
Friday, March 19, 2010
Thursday, March 18, 2010
Just like the ESO press release above, another group of astronomers have looked at a dwarf galaxy (this time, Sculptur) and found another star that dates back to around the time the first stars ever formed. Go here to read more about this discovery. Exciting!
Believe it or not, but I hope you do, the lifetime of stars with masses less than that of the Sun is similar to that of the current age of the universe. That means that such stars born at early times should still be around today. (This does NOT mean that all stars with mass less than the Sun's were born at these early times.) Do you we expect any such stars in the Milky Way? Yes. Astronomers currently believe that the Milky Way formed from the merger of several smaller galaxies which should have been full of such stars. Is there anyway of identifying them? Yes. Since elements heavier than Lithium or only produced by stars, old stars should have a smaller percentage of such metals than younger ones because the material they were formed out of had fewer such metals. Do we know of many such stars? No. Why am I rambling about this? Well, astronomers might have finally found many of these missing low-metal, low-mass stars. Go here to read more. Enjoy!
Wednesday, March 17, 2010
... this one courtesy of the Hubble Space Telescope, which observed Saturn when its rings where edge-on as observed from the Earth, during which time one can see both of Saturn's pole at once for the Earth. Go here to watch its images of Saturn's Northern and Southern lights!
Tuesday, March 16, 2010
Monday, March 15, 2010
Sunday, March 14, 2010
As seen in this beautiful image of the Orion Nebula, many of the young stars in this region are ejecting gas of at speeds of several thousands of miles per hour. Why? How? Well, people are still trying to work it out... The pictures are gorgeous though!
Saturday, March 13, 2010
As I'm sure many of you have already heard, the proposal 2010 Federal Government budget has major implications of NASA - essentially suggesting that the new Constellation program to replace the space shuttle be scrapped in favor of more basic science satellites. The NY Times has its opinion here, what do you think? I'm curious to know, so please leave your opinion below.
Friday, March 12, 2010
While the first exoplanets (planets orbiting stars other than our own Sun) were first discovered more than a decade ago, the composition of these planets has long remained a mystery - especially since these planets appears to be very different than any planets in our own Solar System. Thanks to the capabilities of the ESO's VLT in Chile, a group of astronomers were able to finally directly measure the spectrum of one of these exoplanets (as opposed to looking at absorption lines which appears with the exoplanet passes between us and its star) - giving vital information on the chemical composition of its atmosphere. Go here for details, and enjoy!
Thursday, March 11, 2010
Wednesday, March 10, 2010
Tuesday, March 9, 2010
Hubble might have imaged their ancestors, the proto-galaxies which merged together to form spirals like our own Milky Way. And they didn't appear to be spiral-like at all. Go here for more details.
Monday, March 8, 2010
Sunday, March 7, 2010
Saturday, March 6, 2010
Friday, March 5, 2010
You would think, given how "empty" space is, the odds of two asteroids colliding together would practically never happen. However, it appears that Hubble might have imaged the debris from such a collision. Go here for details.
Thursday, March 4, 2010
Not the TV show, unfortunately. But NASA is planning on launching a new satellite called Firefly to study flashed of gamma-rays - from the Earth! Where they are coming from (no, they are not from underground nuclear tests. Those would be absorbed by the ground and atmosphere and never make it out to space), no one really knows. Read more about it here.
Wednesday, March 3, 2010
Tuesday, March 2, 2010
The type of supernova (Type Ic) discussed in the press release I posted about yesterday, with direct evidence it formed a black hole, is believed to be associated with Gamma-Ray Bursts. Why some of these supernovae produced gammma-rays and others don't isn't known, but maybe this result will help clear things up. Maybe. It is still a puzzle...
Monday, March 1, 2010
As you may have seen, last week a major discovery concerning the nature of Type Ia supernovae which are so important for cosmology. First, why are these supernovae so important? It is because this class of stellar explosions are believed to all be essentially the same - i.e., they all produce the same amount of energy. This means that, if you see one on the sky, you can use its brightness to get its distance (its "luminosity distance" to be overly technical). From its spectrum, you can get its redshift, and by comparing the distance vs. redshift for many of these, one derives the expansion history of the universe. This is pretty much how astronomers first inferred the existence of "dark energy" in the universe, a measurement that is supported by completely separate techniques which I'm not going to discuss now.
Okay, so what are these explosions? That has been the tricky part. Based on their similarity to each other, their optical spectra, how often they occur, and the type of galaxies in which they occur, type Ia supernovae have long been associated with the thermonuclear explosion created by the gravitational collapse of white dwarf. What's that? Well, white dwarfs are "stars" which are supported not by fusion in their core like our Sun, but by the fact that electrons can't get too close to each other ("electron degeneracy pressure"). However, if the mass of the white dwarf is too high, its own gravity is too strong to be balanced by this pressure and it collapses on its self, triggering an explosion which envelopes, burns, and then blows up the entire white dwarf. Since this maximum mass is pretty much the same for all white dwarfs (1.4 Solar Masses, the so-called Chandrasekhar limit since it was first derived by Prof. Chandrasekhar - easily one of the most brilliant astrophysicists of the 20th century and the person that Chandra is named after), it isn't too surprising that Ia supernovae are so similar.
Okay, but how does the white dwarf get so much material? There are two possibilities. The first is that a normal star is in a close orbit around the white dwarf. In some cases, the gravitational attraction of the white dwarf will be so strong that is will rip off the outer layers of the normal star and cause this material to fall onto the white dwarf, gaining mass. (This process is generically called "accretion") The second possibility is that two white dwarfs are orbiting each other, merge for whatever reason, and then the combined mass of the two white dwarfs is so high that it explodes. How can you distinguish them? Well, in the first scenario, the material which accretes onto the white dwarf is hot and shines brightly in the X-rays, while in the second scenario you would get no such emission before a Ia supernova. Is this difference actually observable? Looks like it is. To read more, go here and here among other places. The actual scientific article can be read here, but you might need a library or university IP address to read it for free (any decent public library will have the print version, which is easier to read anyway). Hope this made sense. Please leave questions below.
... it turns out that their formation might help their parent explode after all. Black holes as black widows seems fairly fitting, don't you think? Go here to read about it. This is one of the very few times where we actually observed the supernova and measured the properties of the produced compact object - and the first time for the limited set of explosions that it appears a black hole and not a neutron star was produced. Very exciting indeed.