DARK MATTERS

I'm a physics student from the UK, and this is my blog about space, the universe, and anything sciency :)

[spaceexp]

Why is the Earth's axis tilted?

Earth’s axis is tilted by 23.5 degrees. But why?

Well, Here’s what scientists have theorized.  Theia, a mars sized planet collided with the Earth around 4.553 billion years ago.

Theia’s debris gathered together around Earth to form what we now call- The Moon.

The collision between the early earth and Theia was so immense that it tilted the axis of rotation of the early earth by 23.5 degrees. And it remains tilted so that way even today!!

(Source : http://en.wikipedia.org/wiki/Theia_%28planet%29)

More from me at : 

Fuck Yeah Physics! and  What did you learn today?

[rotationcurve-blog]

A-Z of Astronomy - A

So the word I picked for A was (somewhat predictably) Astronomy! I thought it would be a good idea just to define what it actually is and where it comes from

The definition of astronomy is the study of celestial objects: basically anything that we can see floating around in space. This includes everything from tiny dust particles floating around the spiral arms of galaxies, to superclusters of galaxies lining up along dark matter fringes, forming the largest structures in the known universe! So its a pretty big topic! (Photo from NASA APOD)

Astronomy involves looking at the physics, chemistry and even a bit of biology of these objects to try and explain what is happening. We can use both observations and theory, and one of the key problems in modern astronomy is trying to fit the two together, specifically with things like dark matter and quasars. We need to use a wide variety of wavelengths to study space, from gamma rays to radio waves, and each section of the electromagnetic spectrum enables us to learn something different.

It is one of the oldest sciences, humanity has been staring at the stars for 5000 years, but it wasn't until the invention of the telescope that we started making real progress. The beauty of astronomy is that anyone can do it, you only need to look up at night, and amateurs have contributed a surprising amount to the field.

The word astronomy is interchangeable with astrophysics; they are both used, but mean the same thing. This is something that confused me when I first started learning about it!

[rotationcurve-blog]

New series idea

Ok so I've been kind of busy with all my uni work and other stuff at the moment, so my tumblr hasn't been getting much attention, but I’ve decided I’m going to take a break from my Dark Matter Explained series and start a new one.

Since my blog is all about astronomy and astrophysics, I thought it would be good to do an intro guide to astronomy, specifically an A-Z of some of the words and ideas used :) Hopefully this well help peopel learn and understand more about space, but its also good for my revision as well since I’m currently on the astrophysics course at my uni! When I’m finished I’ll go back to the dark matter one and I’ve got an idea for a series to celebrate 25 years of Hubble watch out for that!

Here’s a cool picture of the Sombrero galaxy (M104)

[rotationcurve-blog]

The comet's song

So I've just started work on an assignment about the Rosetta mission, and while I was researching, I found this interesting fact about the comet 67P's magnetic field. The Philae lander has found that the comet has a constantly oscillating magnetic field, and when this is converted to sound, it produces a strange 'song'. 

Here is a video showing what this sounds like

Interestingly, this has been compared to a modern piece of classical music, called Continuum by György Ligeti.

What do you think? Can you see the resemblance?

[rotationcurve-blog]

Taking a break from Tumblr over the next 2 weeks as I struggle through my university exams! Wish me luck, I'm going to need it!!!!!

[rotationcurve-blog]

Dark Matter 5: MACHOs

In the last post of my dark matter explained series, I talked about the theory that is most likely to be correct in explaining the weird rotation we see in galaxies. This is a yet undiscovered particle called a WIMP which could be anything from a heavy neutrino to a supersymmetric particle. Whatever it is, it has to fit onto the Standard Model somewhere.

But this isn't the only theory. Astrophysicists have been working since the late 1930s on this topic, and there are other explanations around. Another possible one is the theory of MAssive Compact Halo Objects (MACHOs) which says that perhaps there are really big, dark objects; they could be interesting things like brown dwarfs or maybe black holes. They would work in the same way as clumps of dark matter: they would sit around the outside of galaxies, causing this part of the galaxy to rotate faster than the central part, and causing us to see these strange rotation curves.

They could also explain a phenomena called gravitational lensing which is sometimes attributed to dark matter.

This image shows a very massive object (in this case, a star) which is directly in front of a galaxy many light years behind it. The star has so much mass that it is able to bend the light around causing an "Einstein ring" to appear. It is called this due to Einstein's theory of General Relativity, which explains this quite nicely.

This diagram shows what is happening, and how a MACHO could be used to explain the effect.

So what could a MACHO be? An isolated black hole would be a good example, because when they are far away from any other stars, than they cannot form an accretion disc, which would make it basically invisible to our eyes. The only way we can see them is through effects like gravitational lensing.

Even MACHO theory seems like a really good explanation it just doesn't work well enough to explain rotation curves. It seems there just isn't enough normal matter present in the Universe to account for MACHOs being present in nearly every galaxy. A new type of matter needs to exist to explain this, and unless there are massive stars or black holes made out of a new unknown particle then it seems like MACHOs just won't work.

But what if everything we have worked out is wrong? What if galaxies don't actually need more mass? What if Newton was wrong??

More to come in the next post!

[spaceplasma]

Pillars of Creation in Visible and in Near-Infrared Light

"Pillars of Creation" is a photograph taken by the Hubble Telescope of elephant trunks of interstellar gas and dust in the Eagle Nebula, some 7,000 light years from Earth. They are so named because the gas and dust are in the process of creating new stars, while also being eroded by photoevaporation from the ultraviolet light of relatively close and hot stars that have recently formed.

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

[just--space]

A shot of just a tiny bit of the Andromeda Galaxy, from the sharpest ever view taken by the Hubble Space Telescope [NASA] [995x466]

[rotationcurve-blog]

Some of the 100 million stars visible in the new Andromeda image

[ohstarstuff]

Sharpest View of the Andromeda Galaxy, Ever.

The NASA/ESA Hubble Space Telescope has captured the sharpest and biggest image ever taken of the Andromeda galaxy — a whopping 69,536 x 22,230 pixels. The enormous image is the biggest Hubble image ever released and shows over 100 million stars and thousands of star clusters embedded in a section of the galaxy’s pancake-shaped disc stretching across over 40,000 light-years.

Use the ZOOM TOOL to view in full detail.

(WARNING: May cause existential crisis)

[rotationcurve-blog]

100 million stars. In one image

[bobbycaputo]

[rotationcurve-blog]

Happy 15th Birthday Chandra X-Ray Observatory

Fifteen years ago, NASA’s Chandra X-ray Observatory was launched into space aboard the Space Shuttle Columbia. Since its deployment on July 23, 1999, Chandra has helped revolutionize our understanding of the universe through its unrivaled X-ray vision.

Chandra, one of NASA’s current “Great Observatories,” along with the Hubble Space Telescope and Spitzer Space Telescope, is specially designed to detect X-ray emission from hot and energetic regions of the universe.

With its superb sensitivity and resolution, Chandra has observed objects ranging from the closest planets and comets to the most distant known quasars. It has imaged the remains of exploded stars, or supernova remnants, observed the region around the supermassive black hole at the center of the Milky Way, and discovered black holes across the universe. Chandra also has made a major advance in the study of dark matter by tracing the separation of dark matter from normal matter in collisions between galaxy clusters. It is also contributing to research on the nature of dark energy.

Chandra orbits far above Earth’s X-ray absorbing atmosphere at an altitude up to 139,000 km (86,500 mi), allowing for long observations unobscured by Earth’s shadow. When it was carried into space in 1999, it was the largest satellite ever launched by the shuttle.

To celebrate this incredible instrument’s 15th birthday, the Sifter has compiled 15 standout photos Chandra helped capture over the years. Click here to see more Chandra X-ray Observatory images.

These images are absolutely stunning

[futurismnews]

Astronomy Photo of the Day: 1/06/15 — The Pillars of Creation: Revisited

In celebration of Hubble’s 25th year in operation, NASA and the ESA have released a new breathtaking image of the Pillars of Creation, which shows them in unprecedented resolution. Learn more: http://bit.ly/1Altexa

Credit: NASA, ESA/Hubble and the Hubble Heritage Team (Acknowledgement: P. Scowen (Arizona State University, USA) and J. Hester)

[rotationcurve-blog]

New Hubble images!

To celebrate the Hubble Space Telescope's 25th birthday, it has taken pictures of 'old favourites', using its upgraded camera to capture images in more detail than ever before. Pictured here is the sharpest image ever taken of the Andromeda Galaxy (NGC 224). Using this, astronomers will be able to study stars and gas clouds in the galaxy in even more detail, enabling us to learn more about the structure of the spiral galaxy. The HST has also taken an image of the 'Pillars of Creation'

Fun fact: Even in this small section of the galaxy, 100 million stars are visible!

Source: http://www.bbc.co.uk/news/science-environment-30699647

[rotationcurve-blog]

Dark Matter 4: What is Dark Matter made of? - The search for WIMPS

In my last post, I talked about how we can see the effects of dark matter not just in galaxies, but in the wider Universe as well. Gravity pulls the galaxies into a 'cosmic web' pattern - called galactic filaments.

Now we are sure that there is more mass in the universe than we can see, we can start to think about what this extra mass actually is. Obviously, it must be either very difficult or impossible to see with light, and it must be very heavy. This shows that it is not baryonic or 'normal' matter - stuff made out of protons and neutrons that we can see all around us in everyday life. Normal matter can interact with light, and this is why we can see it - it reflects and diffracts light into our eyes. If a dark matter particle exists, then it shouldn't interact with light at all, and this is why can not zoom in with a telescope and actually see it.

It makes sense then to assume that dark matter is not 'normal matter' and must be made out of something more exotic. We know that normal matter is made of atoms which can be split up into particles, so can we get 'dark atoms' made up of 'dark particles'? 

The first image I have included shows a few types of particle that dark matter could be made out of. Out of all of these, the most likely theory seems to be that dark matter is made out of a new type of particle called a Weakly Interacting Massive Particle (WIMP). These basically do what they say on the tin - they don't interact with light very much, and they are really heavy (up to 1000 GeV!).

The second image shows the Standard Model of Elementary Particles - a list of all the different types of particles we have found so far. If WIMPs do exist then they will have to fit into this model somewhere, which is why it has been suggested that they are a type of neutrino (see the bottom row). This is why the hunt for dark matter particles is really on, and scientists at CERN are hopeful that they may be able to find something when the accelerators are turned on later this year.

But if a dark matter particle can't be found, what happens then? Well dark matter might not exist and we might have to find another theory to try and explain it all! More to come in the next post!

[spaceexp]

An “Einstein Ring”or gravitational lensing at work: the blue galaxy is behind the yellow galaxy but we can see it because the light from the far galaxy gets wrapped around by the closer galaxy. Photo NASA/Hubble

via reddit

[rotationcurve-blog]

This can also be caused by dark matter! If the dark matter is clustered together and forms a really dense area in space, then the same effect can happen - the light is bent around the object!

[rotationcurve-blog]

Just found this scientific report where 3 physicists calculate the energy needed to turn water into wine! Turns out it would require nearly 0.4 GJ, which definitely would take a miracle, especially without the proper equipment!

[rotationcurve-blog]

Just realised how long my last post was! I'll try and cut it down for the next one in my Dark Matter Explained series! Stay tuned :)

[rotationcurve-blog]

Dark Matter 3: Filaments - The largest structures in the universe

In my last blog post, I talked about how dark matter or something similar must exist in galaxies, as they seem to be rotating far too quickly to match Newton's laws. If this dark stuff does exist, then it must be dominant towards the outside of the galaxies, forming a 'halo' structure, which would explain why all the stars and gas we see here seem to travel at very fast speeds.

However, we are yet to find a dark matter particle, so in order to make dark matter seem like a more realistic theory, we need to find another use for it in the Universe. The force of gravity is more difficult to see on a small scale so we are unlikely to see its influence here on Earth. So the solution is clear, we need to look at bigger structures in the Universe!

Well what's bigger than a galaxy? What can be bigger than the largest collection of stars in the universe? It turns out that we can get groups of galaxies called clusters and even bigger ones called superstructures. This makes sense; if groups of stars can attract one another enough to form a galaxy, then galaxies can attract one another to form a cluster.

This is shown in the first image, which shows a plot of galaxies as we can see from Earth. There are clear groups of galaxies visible in all directions, along with voids (which may provide evidence for dark energy - maybe I'll make a blog series about this one day!).

However, if we zoom out even further and look at even more distant galaxies (millions of light years away), we find something really quite surprising. These superclusters all seem to line up and form filaments - this is shown in the second image. It almost acts like a 'cosmic web' with gas clouds and galaxies all connected via the force of gravity.

This is surprising because if we look at images like the CMBR, the universe looks like it should be roughly the same in all directions. So the force gravity must be strong enough that it can pull all these galaxies together to form a very clear pattern. Its unsurprising then to find that these filaments line up with tendrils of dark matter, as predicted by simulations that calculated how the Universe formed, and how it changes over time.

So dark matter exists on both galactic scales, and also in extra-galactic scales, showing its influence through the force of gravity. It seems to line up and stick to 'ordinary matter', causing it to form recognisable patterns in the universe. Now we know what dark matter actually does in the universe, we can now start to look at what it might be made of. Is it just so far undiscovered particle? Or could it be something bigger that we just can't see? More in the next post!