All mysteries solved??

I received an email from a relative, asking if the newly discovered “missing link” in astronomy now solves all the known mysteries. My original response was a defiant “No”—for how could observation of polarized light from gravitational waves at the time of the Big Bang, thereby proving inflation, be the answer to all of our mysteries? It definitely does not help answer the question of “how far away is epsilon Aurigae?” But it got me thinking about what impact this amazing finding will actually have on physics. Does it really solve all mysteries?

I first heard about the proof of inflation via a feed I get in my email. There is an excellent summation of what this really means on the Bad Astronomy blog from slate.com. It is quite a complicated finding, but let’s see if I can write a brief summary of what it is and what the BICEP2 B-mode figure means.

The published figure shows polarization (the lines) “ripples” in the Cosmic Microwave Background (CMB), which were created during the inflationary period at the beginning of the universe. The lines show how the light/radiation/CMB is polarized. (Your polarized sunglasses block out light polarized in a certain orientation) The CMB is left-over radiation from the beginning of the universe—it permeates everywhere (that is shown in the blue and red). It is how the polarization “curls” that is the signature astronomers have been looking for. This is indicative of gravitational waves interacting with the CMB.

Now, why does this matter? The figure below gives a lot of information, but the point is that the inflation period happened quickly and allows for the gravitational waves to polarize the CMB. So, it is essentially proof of how the universe came to be—it helps answer how everything is. It provides a link toward the grand unification where the strong, weak, and electromagnetic interactions are all unified (see the 3^rd figure, here). This is a wonderful statement from Phil Plait of Bad Astronomy:

“Inflation is based on principles of quantum mechanics, while gravitational waves are the purview of relativity. QM has brought us computers, solar power, atomic energy—a huge amount of modern tech. Relativity is critical in many aspects of our lives as well, including GPS and also nuclear power. In the past these two concepts haven’t played well together, but now we have a direct and profound connection between them. This result is new, and we have a long, long way to go to understand it better. There’s no way to know what will result from this. Yet. But whenever we open up new fields of science, all sorts of interesting things follow. Bet on it.”

So, let’s refine the opening statement: it solves many mysteries, just not all; and it will open the door to more.

The Future of Space Science

NASA's 2015 budget was unveiled earlier this week and, not surprisingly, the numbers weren't pretty. The proposed budget is 180 million less than for 2014, for a total of 17.5 billion. But only about 5 billion of this is NASA's science budget.  Large amounts of money are required for other NASA programs, specifically anything related to human spaceflight.  For example, development on the Orion capsule and rocket will cost 2.8 billion for the year, and commercial spacecraft development another 850 million.

However, in order to pay the bills associated with human spaceflight, NASA has resorted to gutting its other science programs.  For example, it plans to cut funding for SOFIA entirely. SOFIA is an infrared observatory that is mounted inside a Boeing 747.  The advantage of this telescope is that it can get above much of the interference/absorption from the atmosphere that ground-based telescopes suffer from while flying, but when it lands repairs or upgrades can be made, which is difficult (or usually impossible) on space telescopes.  This is also an international project, so NASA is letting their partner space agencies down in addition to the scientific community.  Of course I'm paraphrasing, but it sounds like NASA's official stance is that if the Germans want to use SOFIA, they can pay for it.

Jupiter's moon Europa

Of course there are science programs receiving funding.  James Webb Space Telescope got 645 million to keep it on track for a 2018 launch, and Planetary Science is getting 1.3 billion. However, most of that money goes toward Mars missions. While I acknowledge that NASA's Mars program has had numerous recent successes and yielded interesting results, there are many other interesting targets in the solar system that are being ignored as a result of this almost singular focus.  One example is a mission to Europa, considered by some to be the likeliest place in the solar system to find life other than earth.  This received only 15 million in funding - just enough for so-called "pre-formulation work"...it isn't even on NASA's long-term roadmap yet.

Plutonium pellet

There's also the question of powering a Europa orbiter, or any future deep-space mission for that matter. Because you receive less light from the sun the farther you get away from it, probes sent deep into the solar system can't rely on solar panels to generate their power. Instead, they use a radioisotope thermoelectric generator (RTG), sometimes called a nuclear battery.  These contain plutonium-238 (not the isotope that goes into nuclear bombs).  The plutonium heats up to over 1200° C, and that heat can be converted into electricity.  The Cassini mission to Saturn and New Horizons to the Kuiper Belt both use RTGs.  Both Voyager probes can attribute their long lives to the reliability of power from an RTG.  So, what's the problem?  NASA only has 36 pounds of plutonium-238 left (the previously mentioned Europa orbiter would require 47), and it hasn't been produced anywhere since the 1980s.  Due to lawmakers dragging their feet on restarting production, it's likely that all the plutonium-238 on the planet will have been used by the end of the decade.

While NASA's Orion project may provide future PR for the space program, it is enormously expensive.  If only a fraction of the 2.8 billion it will get next year (or the 3.1 billion it got this year) was diverted into restarting plutonium production, NASA could save its planetary science program. The same goes for the approximately 2 billion it would cost for asteroid redirection mission planned for 2025, which in essence "creates" a destination for Orion. However, it seems that even given the reality that NASA's budget isn't getting bigger, politicians and administrators continue to choose big, flashy missions that give good photo ops rather than the ones that can give the most science for the money.  Now stepping down from my soapbox...

Cosmos: The book and TV series

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I guess many of you saw the promo for the upcoming show called Cosmos: A Space-time Odyssey. If you haven't seen it yet then you should definitely watch it http://www.youtube.com/watch?v=kBTd9--9VMI 
It is a 13 episodes television series featuring Neil deGrasse Tyson which will air in many television stations from March 9th. It is a follow up of 1980 Cosmos: A Personal Voyage by Carl Sagan http://www.youtube.com/watch?v=ClPShKs9Kr0 . You can watch all the episodes from the series in youtube. There is also a book titled Cosmos by Carl Sagan. This book and the television series have many crossovers as well as different content.
I highly recommend every one to watch this documentary as it is informative and easy to understand. If you prefer to read, then Cosmos will be a good read (in case you haven't read it yet). The book is written in plain English and you don't need to have science background to understand it. It is one my favourite books of all time. What I liked the most about this book was information on the history of science, astronomy in particular. He discusses about how different civilizations approached scientific endeavours. I was left in awe when I read about many historical persons who achieved so much at time when there was not much to work with. In addition to historical events there are many other interesting stuffs in this book. It tries to answer the basic questions about our cosmos which most of us have wonder at some point in our lives.
Do you have any recommendation for other good books?

Asteroids Galore!

Another asteroid just made a close approach! Asteroid 2014 DX110 was closest to the Earth at 4pm EST.

How close?   According to the officials at NASA's Jet Propulsion Laboratory in California, the asteroids closest approach was about 217,000 miles, which is about 350,000 km. Remember, the average distance from the Earth to the moon is 239,000 miles. That means this asteroid just passed between the Earth and the moon!

Now, for us here in Denver, or even those on the East Coast, the sun is still up. You couldn't see anything. Even for those people on the other side of the globe, you still couldn't see anything without a large telescope. This asteroid only has a diameter of 100 meters and thus is very, very faint. Even with some larger telescopes, this asteroid was moving so quickly, it was still hard to track.

The image on the right shows the asteroid that just made its close approach in relation to the background stars. 2014 DX110 is highlighted in a box and blown up so you can see what the object looks like. Mostly, it just looks like just another background star, except for the streak, which was caused because this asteroid is moving so quickly.

The image to the left shows the path the asteroid took as it made its close approach. The path that is depicted is how far the asteroid traveled in only 2 hours! Because this asteroid moves so quickly, it makes it very difficult to track. 

Why might you not have heard about this object? Most likely because it was only discovered last Friday, announced by the Minor Planet Center on Sunday, it is faint, and it won’t be impacting Earth. Although, Slooh hosted a live event detailing this asteroid as it made its close approach. You can watch it here and catch up on all the details.

During the show, the host mentioned that there is going to be another asteroid the will pass extremely close to us within the next couple of days. This object is 2014 CU13, an asteroid of about 20-46 feet in diameter. This asteroid will pass within 37,000 miles of Earth!! Slooh will be hosting another live show on Sunday to track this asteroid.

Science kids

I was in a thrift store the other day looking through the vast number of available children’s books for my toddler son. Out of all of those books, I found a book with a black and blue cover with semi-purple lettering; there were white spots across the front and a misty, blue-purplish region in the upper left. Sure enough, it was the same book I had as a child: A Book About Planets and Stars.

I could remember spending hours staring through the pages and soaking in the variety of features our solar system holds in its planets. I don’t know how much influence that had on me choosing to become an astrophysicist, but I know I loved it then.

And just the other day, my 2 ½ year-old asked me to read him that book before bed. We went through the inner solar system (Mercury, Venus, Earth, Mars) and discussed (yes, discussed!) the differences between these planets. Okay, we just discussed the difference in color, but even then we talked about why. And I’m pretty sure he knows each of the names of the planets now.

Anyway, the point of this post is not to brag about my son, but to point out the importance of helping kids get excited about science/astronomy/physics. From television shows—for instance, Zoom, Bill Nye the Science Guy, and Sid the Science Kid—to youth programs—such as Odyssey of the Mind, FIRST LEGO League, FIRST, YAE— there are a lot of ways for children to participate and compete/learn.

The figure above shows data from APS, documenting the number of physics bachelor’s over the last 45 years, verse the number of bachelor’s in STEM fields (including the medical sciences). It is interesting to note the peaks of the physics numbers: the first peak follows the landing on the moon (1969); the second precedes the successful Pathfinder mission to Mars in 1997 (the first since 1976). I don’t know if the scientific programming as stated previously had anything to do with the increase since 2000, but it is great to see this increase occurring.

The important thing is to help spread the joy of science and discovery to people of all ages, especially those that will influence the path of science for the next generation. Any other thoughts of ideas?

And here are sum fun images regarding Moon and Mars missions from wikipedia:

Space Technology

You may have heard quips about how primitive the electronics used in space technology are compared to what you can buy as a consumer. This can be a puzzling fact given that space exploration is a very technical (and expensive) enterprise.  If we're going to spend hundreds of millions or billions of dollars to send a spacecraft out into the solar system (most of which just goes to getting to your destination), why give it old brains?

In fact, the example of the computers in the lunar landers isn't a very good one to illustrate the point I am trying to make.  While the computing power available is very small compared to devices today, it was actually quite advanced for the time.  So why would I mention an example that doesn't fit with the norm?  There are a couple reasons why technology in the early days of space exploration was more up-to-date than it is today.  The first is easy:  We were engaged in the "space race" with the Soviet Union.  NASA had an enormous budget compared to today, and was given the directive to take whatever steps (and often, risks) were necessary to win the race.

Core rope memory

The second reason takes a bit more explanation. The picture to the left is of a massive 128 byte (wow!) memory module from the Apollo Guidance Computer.  This is what is known as core rope memory, which means that a person sitting in a factory literally wove the wire into a pattern encoding the data.  So...how does that explain why Apollo-era technology could be sent into space easier than today's electronics?  If a human being put the memory modules together, that means the wires must have been at least a minimum workable size.  But consider current generation CPUs.  The size of transistor gates is 22nm.  For comparison, a human hair is about 50,000nm across and a silicon atom (which microchips are made of) is 0.11nm.

A Solar Flare

Both core rope memory and new computer components work fine on Earth, so why not in space?  The difference is that outer space is constantly flooded with radiation from the solar wind and cosmic rays, but (luckily for us) Earth's magnetic field protects us from most of this.  When enough highly energetic particles are passing through your spacecraft, one is bound to hit something important and transfer that energy into whatever it hits.  In old electronics that wasn't a big deal - the components were big enough that the energy could spread out and cause few problems.

Newer components are a different story.  As you may have noticed above, the current generation of computer parts have die features on the scale of a few atoms.  This means that it doesn't take very much energy to flip a digital bit from 1 to 0 or back. That's good when you need to power a CPU with over a billion transistors but very bad when you're being bombarded by high-energy radiation.  Then again, I'm not sure that's ever a good situation to find yourself in...  When a bit flips in a memory chip (usually causing a crash or data corruption), that's called a soft error.

Clearly, electronics on spacecraft must be different than personal computers to function in their environment. Any component that leaves Earth's protective magnetic bubble must be radiation hardened.  There are many techniques for accomplishing this, but they fall into 2 general categories. First, the components are often manufactured using different materials and surrounded by radiation shielding to prevent errors.  Second, there can be error correcting codes for memory and redundant calculations to check for errors that have already occurred.  All of this adds complexity to the design, which then must undergo multiple rounds of testing before it has a chance of seeing spaceflight.  This testing process, which is essential to ensuring spacecraft systems continue functioning after we hit "launch," is why these systems are less powerful than what you can buy at any electronics store.  So rather than making fun of NASA's newest Mars rover, Curiosity, for having a camera with less resolution than your cell phone (it's 2 MP), just enjoy the images it takes and remember that it survives being bombarded by radiation every day.

Telescopes a window to the universe

A telescope is an instrument made up of lens or mirror to observe the far away objects. A telescope magnifies and brings object much closer. Thus making the study of far away object much easier. The first telescope was invented in Netherlands in 17th century. Soon after that Galileo made similar telescope and used it to study the sky.

Observation of moon by Galileo and the picture he made from the observation.

http://www.nasa.gov/audience/forstudents/9-12/features/telescope_feature_912.html
Above link gives us brief history of the telescopes.

http://science.howstuffworks.com/telescope1.htm

The above image illustrates a very simplistic view of how a telescope work. Initially telescopes were made using lenses, later the use of mirror was introduced. There are various types of telescopes in use now.
It can be divided based on what range of electromagnetic waves we are looking at. The light we see is also a collection of a range of electromagnetic (EM) wave.  EM waves can be divided into various categories based on their wavelength. There is very limited range of wavelengths that a human eye can perceive.

Electromagnetic wave spectrum

Brief classification of telescopes on the basis of wavelength
a) Optical telescope
b) Radio telescope
c) X-ray telescope
d) Gamma ray telescope
e) Infrared telescope etc.


These different types of telescopes are used for different proposes. For example
the image here shows the galactic centre but
they are observed by different types of telescopes (i.e. in different wavelengths).
So depending on what they are trying to understand, scientists use different types of telescopes. Even though the older telescopes were ground based (i.e. they were used from the earth for observations) there are many telescopes now which are space based. Some of them are Hubble, Sptizer, Chandra etc. There are lot of beautiful images taken by these telescopes which you can find very easily in the internet.

Also the sizes and weight of telescopes varies a lot. There are telescopes weighing few pounds to thousands of pounds.
I encourage everyone to look through the telescope whenever you can. Most schools with observatories have open house. You can see many wonderful celestial objects through these telescopes if you go to an open house. Here at University of Denver, there is one open house at old Chamberlin observatory every month for the public. If you are in Denver area you should definitely make use of it. Click here to get more informations regarding the open house. http://mysite.du.edu/~rstencel/Chamberlin/

Stargazing Time

Ask yourself this question: "When do the stars come out?"  A first answer to this question might be "when the sun goes down."  I'm not going to say this is wrong...clearly you can see that stars at night.  However, I would say this is a rather inexact statement.  Think about this - how long after sunset does it take for it to get dark outside?  This period of time between sunset (or sunrise) and night is called twilight, and it has nothing to do with sparkly vampires.

As shown in the figure to the left, there are three different categories of twilight:

1) Civil Twilight: This is the brightest of the 3 since it is the closest to sunset or sunrise.  It lasts from when the sun is just below the horizon until it is 6 degrees below.  The name civil twilight comes from the fact that many laws define night to start at the end of this period.  For example, motorists must begin to use their headlights and pilots need to licensed to fly at night.  During this period of time, earthbound objects are usually distinguishable without artificial light while only the brightest stars and planets are visible.

2) Nautical Twilight: This twilight lasts until the sun is 12 degrees below the horizon, so it gets darker than civil twilight.  Nautical twilight got its name from the days when sailors would have to use a sextant for navigation.  It is the time where the sky is dark enough so well-known stars are visible for sighting while it is still light enough to distinguish the horizon for measuring elevation.

3) Astronomical Twilight: This period last until the sun reaches 18 degrees below the horizon, at which point the sky is dark enough for any type of astronomical observation.  Up until this time, most stars can be observed while some galaxies and nebulae cannot.  The sky can appear to be completely dark near the end of astronomical twilight.  Due to the effects of light pollution in populated areas, many observers don't see a sky darker than this.

It's more enlightening to see how twilight works in terms of an actual day, so I got a table of the twilight times in relation to sunrise and sunset for today (in the Denver area).  Of course, these times will change everyday like sunrise and sunset do.  They also depend on the latitude of your city.  If you're interested, click here and then on "more" in the bottom table to see a table for the current date at your location.  See...isn't this twilight so much better?

Supernova

“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.”

― Carl Sagan, Cosmos

Simplistic view of different stages of stars

Crab Nebula

 Doesn't it feel wonderful to be made up off starstuff. Well today I want talk about a spectacular phenomenon called supernova where most of the massive metals are made. Above is a very simplistic diagram of life cycle of a star. As you can see depending on the mass of the star (roughly if mass is greater than 8 times the mass of sun, it is considered a massive star) it can have different paths. During their life span they burn hydrogen initially to produce the energy. As the time passes, massive elements are formed. In the end they end their life as a supernovae.

 Supernova is an explosion of massive star at the end of its life. It is a very energetic event where energy equivalent to billion times the energy of sun is produced. To get the sense of this amount of energy, the energy consumption of the world for 2008 was about 5*10^20 joules. The energy from one supernova is nearly 10^46 joules.  From this explosion the elements made in star core is distributed in space. These event on average occur only once per galaxy per 100 years. In the universe there are around 30 supernovae per second. This interesting fact gives you idea as to how huge our universe is.

Whew, that was close!

Did you know that an asteroid flew past Earth last night? On the left is the trajectory. The 270 meter asteroid (about the size of three football fields), known as 2000 EM26, streaked past Earth at a distance of about 2.1 million miles (3.4 million km). Just for comparison, the mean distance from the Earth to the Moon is 238,900 miles (384,400 km). So this asteroid was about 8.8 times the distance from the Earth to the Moon at its closest point, and it will be traveling about 17,000 mph.

This object is classified as potentially hazardous when it was discovered in 2000 because of its projected path and because of its size. There were 32 observations in 9 days and then something interesting happened; it disappeared! Based on the trajectory determined in the those 9 days, this asteroid made close approaches in 2002, 2003, 2006, 2009, 2011 and 2012 and yet it was still never rediscovered! This asteroid is very faint, aka very low albedo, and thus hard to track.

Slooh, a community observatory where you can view live through a telescope, generally shows interesting astronomical events; transits, asteroid flybys, etc. Slooh also tracks newly discovered

asteroids and submits the data to the Minor Planet Center. This is in hopes of never loosing an asteroid again. 

Slooh hosted a "live" event last night for the asteroid flyby, which you can re-watch here. 

Spoiler Alert: Still haven't rediscovered it!! The Dubai Astronomy Group was feeding in live images of the sky of where the asteroid should have been based on its trajectory, again determined 14 years ago, but nothing could be deduced.

This asteroid is now nicknamed Moby Dick for its elusiveness.

We need your help! Amateur astronomers, help us find this asteroid before it is too far away! Check out some more information here. 

The idea of LCROSS

My grandfather has been able to do many things during his astrophysics tenure. I attribute my love of physics and astronomy to him. I remember wanting to wear one of his rocket missions-into-the-aurora borealis t-shirts for a week straight (I don’t remember if my mother allowed her crazy son to actually do it!). He has had a lot of impact on what I’ve chosen to do, even with very sporadic communication. Regardless, my head still turns when I hear about things that he has contributed to.

One thing that he was very excited about was his involvement in pitching the idea of LCROSS. He said it took about 25 years for the idea to come to fruition, but it finally did in 2009 when—if you recall—a spacecraft was hurdled into the depths of a crater on the south pole of the moon. A large series of figures and pictures are included here. One of the purposes of smashing into the moon was to find water (in the form of ice) at the base of the craters, where the water hasn’t been sublimated by the sun. Well, it turns out, my grandfather and his co-workers were correct.

They did indeed find water at the base of the craters. However, LCROSS also found a number of volatiles, including methane, ammonia, and hydrogen gas. A debate has begun on where or how those volatiles got into that crater. One of the most common thoughts is that comets or asteroids composed of those materials crashed into the moon and delivered those materials; this is a very viable option considering the number of impacts the moon has absorbed. The other thought is that the lunar ice is able to react with high-energy cosmic rays (that are not shielded by an atmosphere or magnetic field) over millions of years.

This idea was published by Crites et al. (2013). They state that these cosmic rays (because of their constant, high-energy bombardment of simple ices) have the ability to “stimulate organic synthesis.” This means that the growth of more complex molecules can happen anywhere that has volatile ices and exposure to high-energy cosmic rays. This would include many of the smaller planets and moons in our solar system (Mercury, Pluto, Jupiter’s moons, etc.).

An example of their modeling and experimental results are found above, which is Table 3 from their published paper. The important things to note are the starting compounds (column 1), the product resulting from cosmic ray bombardment (column 2), and the resulting mass of the product from a mass of 1kg of the starting compounds (column 5). So, just by starting from different combinations and ratios of water, carbon dioxide, methane, and carbon monoxide, they were able to get molecules of methanol (CH3OH), ethanol (C2H5OH), and many others.

To me, this shows the impact (no pun intended) and progression of ideas: (1) a group of scientists had a thought to create a plume of material from the base of a lunar crater; (2) that turned into a mission at NASA; (3) the discovery of water AND volatiles present on the moon’s surface; (4) theories of the origination of these materials concludes this conversion process could be occurring all over the solar system.

In other words: keep the ideas/thoughts/questions/hypotheses coming!

The Universe on Your Phone (or Computer)

Have you ever looked up at the night sky and tried to remember the names of the stars and constellations you are seeing?  If you have a smartphone, Google has a very nice Android app for locating constellations, stars, planets, etc.  If you're an iPhone user, Apple doesn't play nice with Google, so you don't get their toys...sorry.  I included a screenshot of what Google Sky looks like running on my phone.

Your phone knows several pieces of information that allows it to generate this sky map.  First, and not at all surprisingly, it knows the time.  It also knows your location.  Even without GPS, a phone can tell where it is by what cell towers are in range.  The time and place on Earth's surface are both necessary to determine which stars are overhead.  Then, you need to know which direction in which your phone is pointing.  This is done using an accelerometer, which can measure which way gravity is pulling on the phone.  With all that, you can point your phone up and - voila - the stars and constellations on the screen follow the ones in the sky...except these ones are conveniently labeled.  Another neat feature of Google sky is that you don't have to pan around the entire map to find a particular object.  Being a Google product, this also includes a search function.  I showed a screenshot of locating Mars.  The circle is red to indicate that I'm almost pointing directly at it, and it would be blue far away.  Google Sky also has a website here, which also includes visible, infrared, and microwave observations stitched together into a full-sky map.

While it is not as accessible as Google's products (it's a program that only runs on Windows 7/8 computers), Microsoft Research's WorldWide Telescope offers access to a much larger amount of data.  This includes planetary data, and the ability to browse in 3D.  If you click here, you can see a sample dataset they put online allowing you to look around the MilkyWay in 3D (click your mouse and drag on the picture...it's not just an animation).

The great thing about both Google Sky and WorldWide Telescope is that they are both intended to be used by the general public.  They were designed by consumer companies (Google and Microsoft) with that use in mind.  This has two big advantages:  First, the webpages and documentation were written assuming a home user would be reading them.  Second, the user interfaces were designed professionally, eliminating a great deal of confusion in the first place.  Happy...observing?

Astronomers discover oldest star to date

It was announced this week that astronomers at The Australian National University, led by Dr. Stefan Keller, have discovered a 13.7 billion-year-old star, meaning it formed soon after the Big Bang.  This is helpful to our understanding of the early universe, because by determining the chemicals present in this star (which has been done), astronomers can have a better sense of what the early universe was like.

Previously, astronomers believed that this type of star would have died in a supernova and emitted large amounts of iron into the surrounding space.  However, the signature of this newly discovered star shows no iron at all, which indicates a much smaller supernova than previously thought.

The star was discovered as part of the SkyMapper program which has been searching for ancient stars for several years, while also creating a map of the southern sky.

A link to a user-friendly article about the discovery:  http://www.sciencedaily.com/releases/2014/02/140209200836.htm

A link to the publication in Nature:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12990.html

Our home: Milky Way galaxy

 

 One of my favourite ways to pass time has always been looking up at the sky and wondering how huge the universe is. When I was kid I lived in a small town so there were not much light pollution. Thus I could see the milky way band during clear nights. The band consists of stars which our eyes cannot differentiate and seems fuzzy. These stars extend over the horizon giving the appearance of a band. Above is one of the many beautiful pictures you can find in internet of the milky way band. It is one part of the galaxy we reside in. Today I want to talk a little about our home galaxy. 

 

An artistic illustration for our galaxy. http://apod.nasa.gov/apod/ap050825.html

 

 

 

 

Milky way galaxy is a barred spiral galaxy. You can see  artistic illustration  in the above picture. It is composed of spiral arms and a central bulge.The central bulge has a massive black hole. Since this bulge is very dense we cannot even see the centre of our galaxy. Thus, we cannot see the other side of the galaxy. Our galaxy contains about 200 billion stars and, it also contains lots of gas and dust to create billions of more stars. It has a diameter of 31 to 37 kpc. 1kpc is nearly equal to 3*10^16km which is a huge number.

The scale of size in astronomy is very interesting as well as frustrating at times. It is very difficult to comprehend the size scale in case of astronomical objects. I have linked a video which try to give you the idea of how huge the stars are. Thus might help you to understand the size scale.

http://www.youtube.com/watch?v=HEheh1BH34Q 

Also I am liking the blog by Brandon Kuschel where he has talked about the size of the universe. http://astrorad14.blogspot.com/2014/01/scale-of-universe.html

Our solar system is out of the central bar. Here is an illustration of the location of our solar system in the galaxy. Our solar system is revolving around the centre of the galaxy at the speed of 220 km/s.  

 Our sun is an average mass star and around 4.6 billion years old. About half of the stars in our galaxy are older than our sun. Most common stars are red dwarf in our galaxy. These are cooler and less massive than  the sun. The oldest star known in our galaxy is older than 13.6 billion year.

Even though our galaxy is huge, we are part of even bigger structure, called the cluster of galaxies. And we belong to Virgo cluster. And there are many such clusters. It is amazing how huge the universe is. 

Let's not stop looking at the vast and amazing night sky.