The Sombrero Galaxy

How is this not a hilarious name?

Another spiral galaxy, this one has most of its dust and gas in a ring around the center unlike ours. Additionally, its central supermassive black hole is much larger than ours and it has many more globular clusters than our galaxy. The Sombrero galaxy is also home to bright, younger stars making it twice as useful to study, since you get both the really old and really new stars within it. However, this sombrero is not without its mystery; due to the amount of dust in the central, much of the light coming from it is scattered, making that portion difficult to study. Astronomers are also not quite sure why there is so much dust in this galaxy, though it has been proposed that it is due to a dissolved bar.

The Sombrero galaxy is overhead at midnight now (RA ~12:40) with a declination of ~-11:37, so if you have a telescope at home you should be able to see it, as it is also a pretty bright galaxy (+9 magnitude) for being about 30 million light years away (that's something to think about while looking at it!).

(Image taken from Nasa's "Astronomy Picture of the Day")

More Galaxy Stuff

The galaxy with the recent supernova:

(Taken from Nasa's "Astronomy Picture of the Day")

The galaxy itself is ~75,000 light years across and resides in the Leo constellation. Like our galaxy, M95 (as it's called) is also a barred spiral galaxy. It's about 38000 klys from us and the center star forming ring is about 2000 lys across. Its declination is ~+11:42 and its right ascension is ~10:44, so now is a pretty decent time of the year to see it for astronomers, especially if you don't feel like staying up super late (which makes me think, that supernova had pretty convenient timing for being observed...).

Galaxies

So hopefully we all know that we live in a galaxy and most likely even people know that we live in a spiral galaxy. However, most people probably don't know that there are many types of galaxies, not just spirals.

Galaxies are collections of celestial matter, such as gas, dust, etc. held together via gravitational attraction. Their shapes and types range from spirals, to rings, dwarfs to huge sizes and are classified under spiral, elliptical and irregular. A few years ago, it was proposed that there are also "dark galaxies", or galaxies made up of entirely dark matter.

Going through each of the types of galaxies and what makes them unique enough to be classified separately, let's start with irregular galaxies. Irregular galaxies do not have a structured form that lends itself to a particular shape. They are comprised of partially ionized hydrogen, caused by UV emitting stars. Wind plays an important part in these galaxies causing, from what I can understand, some of the gas to be blown out from the galaxy, changing the mass and density of the galaxy. Stars seemed to be formed in bursts in these galaxies, with long periods of rest in between. Irregular galaxies tend to be more faint have have less mass than other galaxies, as well as containing more gas and less metals.

(Image taken from Nasa's "Astronomy Picture of the Day")

Next are elliptical galaxies. Elliptical galaxies get their name from their shape and contain older stars (globular clusters!). Additionally, because there is not much gas or dust contained within these galaxies, elliptical galaxies tend not to form stars. They tend to be found in clusters of other galaxies and it may be the case the elliptical galaxies are formed from galaxy collisions. While elliptical galaxies are generally less blue (since the stars contained within are red and colder), some elliptical galaxies have shown to be quite blue due to older stars fusing helium in their cores, causing a higher overall temperature. Many of these galaxies contain supermassive black holes at their center, with other elliptical galaxies awaiting confirmation on the presence of one.

Centaurus A - An elliptical galaxy? Astronomers are still unsure

As a note of transition, there are also lenticular galaxies, which are something like an "in between" of an elliptical and a spiral galaxy. They contain many old stars and do not actively form new stars, but they also have semblances of spiral arms. Also, they have more dust than elliptical galaxies and have a similar luminosity to speed ratio but offset by the fact that the stars in a lenticular galaxy are much older.

Finally we come to spiral galaxies. Spiral galaxies have a large concentration of stars towards the center of the galaxy, with star forming regions in the arms. They have a rotating disc (unique to spiral galaxies), which contains newly formed stars. Additionally, they too have supermassive black holes at the center. Our own supermassive black hole still has not been observed that well, though we have found evidence that ours is not as massive as black holes in other galaxies. Spiral galaxies may also have a "bar", which are found in the majority of spiral galaxies, though it's not entirely clear what the function of such a bar is, however bars are indicative of the galaxy being fully formed.

The pinwheel galaxy

Obviously there is much more to say about galaxies past what I've covered here and there is still much more to study about galaxies.

Earthstorm - "Defeating the Moon"

The moon does not work this way. Nor do magnetic fields. Or pretty much anything else. Luckily for the movie's plot, Stephen Baldwin does not give a ****.
Backstory to this clip: some rift got created in the moon...somehow (an asteroid did it, according to the internet, I couldn't actually remember) and of course started ruining life on Earth. Luckily, Earth's top "scientists" had the brilliant idea of sending some people to space to plant an explosive in the moon and detonate it, which they figured would somehow fix everything. Apparently it worked. My dad and I were watching this on TV for the lols (this clip is not the only scientifically terrible thing that you will see, among other things there are also people walking around the space shuttle as if they were on Earth. Because you know, gravity works like that. Also, they spell "astronomy" incorrectly) and I had stepped out of the room for a bit and when I came back, I had missed this sequence. When I asked what had happened, my dad said that they defeated the moon, hence the title of this post.
Just look at the boredom in everybody's face. They are all simultaneously thinking "God, I want to go home".

Blog Posts

It technically being Thursday today and the last day for the posts to have any grade value, I'm going to try to get out 2 more good posts by the end of the day. I'm not sure when the cutoff time is but I will try to have them up by 5PM.

The Crab Nebula

I have a really hard time coming up with blog ideas, mainly because I'm not used to blogging or any of that sort of thing (I don't have a personal blog or a Facebook page or anything like that). However, thinking back to a somewhat recent game of Astronomy Monopoly gave me the idea for this blog. While playing, I became intent on "owning" (a phrase I hate when it comes to astronomical bodies) the crab nebula. But aside from it being in a lucrative position on the game board, what makes it so interesting?

The Crab Nebula is a leftover from a supernova. The brilliant colours that are observed (well, from colourized pictures) are all from the gas that was once a part of the star, lit up by x-rays and other forms of electromagnetic radiation.

How is this not awesome?

In relation to my last blog, the Crab Nebula is the result of a star going supernova, which created a neutron star. When the light from the supernova finally reached Earth, it was so remarkable that it was widely recorded across many civilizations and remained bright for months, giving the Sun some massive competition for being our only appreciable source of light from the sky. The original star was about 9 times the mass of our sun but now what is left of the source star is tiny and its remains are strewn all around it. The gas surrounding the neutron star weighs about 5 times that of our sun! The central ring of gas is comprised mostly of helium, and more outwardly comprised of heavier elements.  Also, the neutron star pulses very quickly, though like all neutron stars it is slowly losing its energy and is slowing down. 

The Crab Nebula is what is known as a "diffuse nebula", meaning its boundaries are not clearly defined and it is very bright in the infrared. When viewed in the infrared, the nebula appears as a very intense blue colour. It has also been suggested that the blue of the Crab Nebula is due to electrons curving due to their high velocities. This is due to the inherently strong magnetic field within a pulsar, causing the electrons temporarily caught within it to be sped up.

Additionally, the Crab Nebula is still expanding, which helps us determine how far away from us it is. That being said, it is about 2 kiloparsecs away (or about 6.17*10^19 meters), so while not the closest thing, it is still closer to us than the center of our own galaxy.

The Crab Nebula is still a subject of great interest, even today. There is still a lot that we don't know concerning the neutron star at its center because it is very difficult to see past the gas surrounding it. For instance, we don't know how much the neutron star weighs, its radius, luminosity, etc. We do know it is a young neutron star and its pulse rate (33 milliseconds) and the nebula itself is the source of very strong x and gamma rays. The mass of the neutron star is still quite a mystery since scientists are currently unable to resolve the predicted star mass (pre-supernova) to the remnants existing today. Additionally, the nebula is almost directly in line with the Earth, meaning it often gets covered up by things between us and it, including the plasma from the Sun. Also, its aforementioned expansion seems to be increasing, making it difficult to date exactly when the supernova originally happened.

"Crabby McAwesome" (by far the most professional nickname I've given to anything) is an historic nebula that we still have much to learn about and hopefully as our technology improves even more, we will find new ways to gather information about it, giving us more insight into how this badass nebula works and possibly what the star was like before it exploded.

Neutron Stars

Since I briefly mentioned neutron stars in my last post, I thought I would expand on them a bit further.

Neutron stars are essentially the remains of a star that has undergone a supernova. Once a star has finished burning all of its fuel, the core collapses. The result of the collapse is a huge amount of mass in a very small space; a typical neutron star has a mass of about 1.5 times that of the sun (or nearly 3x10^30 kg) with a radius of about 11-15km. This amount of mass in such a compact space is ridiculous (there are a few perspective examples out there of comparing the radius to the size of a certain city but honestly I don't think that even these easily imaginable examples really clearly communicate the state of a neutron star because honestly, what person can actually put 3000000000000000000000000000000 kg into any understandable perspective, even with an imaginable, relatable radius size comparison?).

Due to this amount of mass in such a small volume, the density of a neutron star is immense (p=Mass/Vol, so the density of a neutron star with a 1.5 solar mass and a 15 km radius would be about 2.122x10^14 g/cm^3 -I've given it a larger radius just to illustrate how extreme these things are), meaning there is also a lot of pressure in a neutron star. This pressure is what gives a neutron star its name, as the pressure will cause protons and electrons to form neutrons - the main composition of a neutron star.

Obviously due to this mass, it also means that they have an incredibly strong gravitational attractive force, so gravitational lensing (light being bent) occurs. Additionally, the decrease in radius also means an increase in rotational velocity, with neutron stars rotating with periods of less than a minute. A subset of neutron stars, millisecond pulsars, are neutron stars that rotate once every few milliseconds (hence their name). I imagine these to be somewhat like the most horrifying merry-go-round in existence. Millisecond pulsars are very reliable in their rotational periods, making them easy to study and also provide for relatively easy study of anything that interacts with them (since the interaction will change their rotation rate, which is easy to detect). Millisecond pulsars are also emit across the entire EM spectrum, with some pulsars emitting more strongly in some areas of the spectrum than others (i.e. gamma-ray pulsars, x-ray pulsars, etc).

Some neutron stars are binary partners, though this is rare. Neutron stars are not limited to binary systems with other neutron stars however. If its partnered star is close enough and low enough in mass, the neutron star will end up "eating" its partner. Along with any mass accumulation due to a binary system, a neutron star can also collect gas from its "friend" in the system. When the gas gets close enough it will heat up, causing the neutron star to emit x-rays.

So all of this information may seem great but why should we care about neutron stars? Well, neutron stars have large magnetic fields, far beyond what we find on Earth, so that's interesting within itself. Also, because of their small radius and huge mass, neutron stars a somewhat similar to black holes but much more friendly to study. The reliability of millisecond pulsar's rotations also make for a nice "cosmic clock" and allow us to study events very with precise time measurements. Occasionally neutron stars exhibit strange behaviour or are found to exist with certain oddities that can be of interest to study. Obviously these are not all of the reasons why neutron stars are interesting but it is at least a decent selection to start with.

End note: I had to use p instead of rho because blogger did not like the introduction of a semi-foreign letter. Also, count how many times I used the word "also" in this post. It's a terrible linguistic crutch that I find slightly amusing.

Globular Clusters

Globular clusters are large (>100 ly diameter), spherical groups of stars that are bound to one another by a very strong gravitational attraction. They are fairly commonly found (at least 150 are known in our galaxy) and contain many dense, old stars (10 billion+ yrs). The stars within a globular cluster have highly eccentric orbits with high radial velocities. Some clusters are close enough that we can study individual stars within them; a great asset indeed!

Globular clusters are found in the part of the galaxy with hot, ionized gas, known as the halo. What makes globular clusters interesting is the sheer amount of stars (10,000+), all of which are about the same age and all located within a fairly condensed region of space. The stars range from variable, white dwarfs, neutron stars, pulsars, etc. though most are variable. Generally, the stars in globular clusters are not giants or supergiants due to their age (giants and supergiants have fairly short lifespans, as far as stars go). This also explains the presence of neutron stars in globular clusters, indicating that perhaps at one time, giants or supergiants did exist in the clusters but died out (this is just my guess). Most of the stars in the cluster are comprised of mainly hydrogen and helium, which is also a clue to indicate the star's age (the older a star is, it will have a great composition of hydrogen and helium, as opposed to a younger star which will be composed of a greater diversity of elements).

(Photo taken from sciencephoto.com)

(H-R diagram for the globular cluster M5. Notice the values for the luminosity and B-V, putting these stars well out of the main sequence range. Photo source)

Additionally, all globular clusters are of about the same age and tend to contain about the same amount of stars.  It is thought that globular clusters have survived early galaxy collisions due to their high gravitational attraction, disallowing for the stars to be destroyed by the changing gravitational forces that occur during galaxy collision. This means that while other stars and star clusters were being destroyed because they couldn't handle the changing gravitational forces, globular clusters were able to survive because their collective gravitational force with one another left them relatively unaffected by the changing conditions.

Globular clusters are great for astronomers to study because of their age and number of stars present. It helps give an idea about how stars evolve and also tells us what stars were like in the early universe, as well as giving us and indication about the age of the universe itself. Additionally, some globular clusters may contain black holes; these black holes give us information about all sorts of things, including star and galaxy formation, as well as black hole formation (whether they are formed all at once, or slowly over time). Also, since globular clusters are so old, this indicates that the black holes are rather ancient as well.

Globular clusters are a fascinating and important part of our universe and we are lucky to have them around!

What Astronomers Do

I have a hard time explaining my understanding of what astronomers do when I am asked by family or other people I know. The first and most obvious answer I give is that they observe things, usually stars, in the sky so they can later study them. Most people, when I say this, probably don't realize that there are a lot of different kinds of stars that are formed and behave differently. The differences in these stars make them interesting for study. Why should one star form one way and another star form a completely different way? Learning about the forming conditions are just one jobs of the astronomer. Other astronomers are interested in how things first started billions of years ago. Learning about how other galaxies were formed and how they work gives us insight about our own galaxy. Then there is the question of what is space itself made of? Before the 20th century or so, astronomers thought space was made up of the aether but that was found to be false. The constant inquiry of astronomers has lead to a more accurate understanding about the very nature of space itself.

Those are just a few of the things that come to mind immediately when I am asked about what astronomers do. Of course, one can't think about astronomy without thinking of telescopes and pretty pictures as well. If most people don't really know what astronomers do then they also have less of an idea about how the telescopes work as well. So knowing how to operate the telescope is also a part of what astronomers do, at least if they want to collect any data.

Astronomers also employ math to come to conclusions about their data, or to support new ideas that are in the process of becoming theories. I always have to remember not to overlook this aspect when describing astronomy to other people, that astronomy is not just collecting data with a bunch of cool technology.

Although for me, the hardest part about trying to explain what astronomers do is to try and put it in some sort of context that most people will care about or be able to relate to. For most people, understanding how stars form and such is rather useless knowledge; it's (most likely) not going to cure cancer and it doesn't help run a business. To me though, learning and developing a better understanding of our universe is more important than managing a business. After all, we are all living in this giant expanse of space and to limit our interests to the mundane, everyday activity of ourselves is to miss the point of what it means to be inquisitive beings trying to expand our knowledge.