Monday, May 30, 2011

Pluto a planet's discovery story

Courtesy of Astro Leo's planets
Pluto's discovery story is not only an important part of Astronomy's history, it is also part of American history. It all started with Uranus, the 7th planet. In the early 1840's French mathematician Urbain Le Verrier predicted that there should be another celestial body perturbing the orbit of planet Uranus. The story of the discovery of Neptune then confirmed this prediction from Le Verrier. Further observations of Uranus later in the 19th century led to the speculation of yet another celestial body still perturbing Uranus.  Therefore in 1906, Percival Lowell from Boston Massachusetts, started a project in search for the 9th planet from the Lowell Observatory in Flagstaff, Arizona.  Lowell died without knowing that the observatory had imaged Pluto but had failed to recognize it.

The search for Pluto was put into hiatus until 1929, when Clyde Tombaugh a natural from Kansas, working at the Lowell Observatory finally found a moving object in photographic plates between the nights of Januray 23rd and Janurary 29th, 1930.  The results were sent to the Harvard Observatory on March 13, 1930 after confirming with a third exposure made before in January 21st.  The name's that went up for vote were Minerva, Cronus and Pluto.   Pluto received every vote!

Wednesday, May 25, 2011

The Expanded Very Large Array

EVLA image of supernova G55.7+3.4
Bhatmagar et al.
The electromagnetic spectrum is the realm of astronomers. From high energetic X-Ray photons to the the long wavelength radio photons. So how do we detect these radio photons? The answer is: radio telescopes. Why are they called telescopes anyways? Well, they let us "see" into the universe at frequencies where our eyes can't see. But more impressive, we can take pictures of the night sky so that we can see what our eyes couldn't otherwise. Radio telescopes have been around for a long time now. The largest single dish Radio telescope in the world is in Arecibo, Puerto Rico. If you have ever seen the movie "Contact", then you have seen this excellent facility. Another entertaining sci-fi movie is "The Arrival". On this movie we see a telescope facility of 27 white dishes. These dishes are the famous Very Large Array telescope in New Mexico.

The Very Large Array has recently been beefed up and renamed the EVLA or Expanded Very Large Array.  The image above is supernova G55.7+3.4, the remnant of a star that blew up to smithereens. The filamentation seen on this radio image was not visible until the EVLA was upgraded to be 10 times more sensitive that in the past.   So what was changed in VLA?  Well it was pretty much gutted out of the 1970's electronics and added new 2000 tech to it.   This new and improved electronics makes the VLA so much more sensitive than before.  So why the image of a supernova remnant?  Can't we already see these objects in the sky?   Sure we can!  But not like this.   Imagine that you are watching your favorite movie on your old TV without high definition.   Now erase that memory and imagine your favorite movie in HD (high definition).   The difference is like night and day!  That is a good analogy to the new revamped EVLA.  We will be able to see fainter and deeper into our galaxy and detect until now unseen objects and reveal new details on existing ones.

Tuesday, May 17, 2011

SETI goes Kepler

Courtesy of NASA/Ames Research Center
The search for extraterrestrial intelligence (SETI) is one of the outstanding questions on the minds of many.   Needless, to say, this stems from a need to know if we are alone in the Universe.  SETI is focusing its search on the recent data release from the Kepler Space Telescope.   SETI has selected 86 planets from the the 1235 released by Kepler.   Why only 86?  Well, the main reason for this is that they want planets that can sustain water in liquid form.  Many of the planets detected by Kepler, so far, are giant gaseous roasters.

The search will be performed with the Green Bank Radio Telescope in West Virginia.   This facility can  record over 60 terabytes of data per day of observations in the range between the 21 cm hydrogen line and the 18 cm hydroxyl line.  Why between these 2 lines?  Well, to begin with this region on the radio is rather quite in the Universe and it is not absorbed by anything that we know of.  And second, SETI scientists believe that an intelligent civilization that depends on water will broadcast signals in this region dubbed, the "water hole" region.

The question remains, will we find intelligent life via radio waves?   Well, the answer is really out there, according with extrapolations from the Kepler observations, we could easily find about 50 billion planets in the Milky Way.  That is a huge number of planets.  Perhaps ET is in one of them!

Wednesday, May 11, 2011

Stars Delivered in 10 seconds a lesson in Magnitude

Welcome back to another astronomy blog after a long week.   On the right there is an image of the sky taken with my SCT 12" telescope and my main CCD camera. The exposure was 10 seconds long in the neighborhood of the North Star, Polaris.   The first feature I would like to point out on this image is the light bleeding out from Polaris into the image.   Even though Polaris itself is not on the image you can still see the light streaking out from the left side of the image.  This is because Polaris has an apparent magnitude of 1.97.  That means that it is a very bright star. For comparison, a full Moon has an apparent magnitude of -12.7.   The more negative the magnitude the brighter the object is.

The image is also inverted in color space.  What this means is that the black dots are the stars.  It is sometimes easier to see them this way.  Now lets talk about the stars on the image.  The brightest of them is the one that look the largest on the image, slightly right off center.  This is HR 286 a 6.47 apparent magnitude main sequence star.  Now, try this out, find the dimmest star on the image.  There are several very dim stars on this image.   Their apparent magnitude is around 14.

But what does this apparent magnitude means?  It means that a star of 0 magnitude is 100 times brighter than a star of 6th magnitude.   In our previous example HR 286 is approximately 1000 times brighter than the dimmest star in the image.   That is a LOT brighter!

Wednesday, May 4, 2011

M15 a Globular Cluster in our Milky Way

Messier 15 is a globular cluster in our Galaxy, that is to say, it is a bunch of stars that are bound gravitationally and travel along our Milky Way galaxy as a set.   Globular Clusters are different than Open Clusters by the fact that there could be hundred of thousands of stars in them commpared to the tens you find in Open Clusters. So you may ask yourself the following question: Is a Globular Cluster a Mini Galaxy in of itself?   This is a very good question, that has many answers depending on who you ask.   That wasn't very helpful.  Was it?    Well here is one of the defining criteria according to me!   A Globular Cluster is not a Galaxy because there is no current material exchange in the evolution process of their stars.  In English, what that means is that GCs are typically gas less objects.   There is little to no gas in them which inhibits their star formation.  Galaxies in general have gas and star formation process.

So why M15 for today's blog?   Well, other than it is a very pretty and super dense cluster in our Milky Way, it is believed that among its numerous star in its core there is a black hole.  It is also a magnitude 6.2 object in the sky, which means that it is a the limit of naked eye visibility under exceptionally good conditions and easily found with binoculars.   It is also the home of PSR 2127+11 C , a pulsar that is on a binary system with another neutron star.   This binary system is test ground for the theory of General Relativity and gravitational waves. Also, Pease 1 is the first planetary nebula found on a Globular Cluster.   It is home to 119 variable stars.  Its age has been calculated to be around 13.2 billion years old?  Isn't that mind boggling?

So in general M15 is a sandbox of astronomical science.  It has a bit for everyone from observational to theoretical astrophysicists.