Monstrous-mind - The Monster Mind

Astronomy From 45,000 Feet

What is the Stratospheric Observatory for Infrared Astronomy, or SOFIA, up to?

SOFIA, the Stratospheric Observatory for Infrared Astronomy, as our flying telescope is called, is a Boeing 747SP aircraft that carries a 2.5-meter telescope to altitudes as high as 45,000 feet. Researchers use SOFIA to study the solar system and beyond using infrared light. This type of light does not reach the ground, but does reach the altitudes where SOFIA flies.

 Recently, we used SOFIA to study water on Venus, hoping to learn more about how that planet lost its oceans. Our researchers used a powerful instrument on SOFIA, called a spectrograph, to detect water in its normal form and “heavy water,” which has an extra neutron. The heavy water takes longer to evaporate and builds up over time. By measuring how much heavy water is on Venus’ surface now, our team will be able to estimate how much water Venus had when the planet formed.

We are also using SOFIA to create a detailed map of the Whirlpool Galaxy by making multiple observations of the galaxy. This map will help us understand how stars form from clouds in that galaxy. In particular, it will help us to know if the spiral arms in the galaxy trigger clouds to collapse into stars, or if the arms just show up where stars have already formed.

We can also use SOFIA to study methane on Mars. The Curiosity rover has detected methane on the surface of Mars. But the total amount of methane on Mars is unknown and evidence so far indicates that its levels change significantly over time and location. We are using SOFIA to search for evidence of this gas by mapping the Red Planet with an instrument specially tuned to sniff out methane.

The plumes, illustrated in the artist’s concept above, were previously seen in images as extensions from the edge of the moon. Next our team will use SOFIA to study Jupiter’s icy moon Europa, searching for evidence of possible water plumes detected by the Hubble Space Telescope. The plumes were previously seen in images as extensions from the edge of the moon. Using SOFIA, we will search for water and determine if the plumes are eruptions of water from the surface. If the plumes are coming from the surface, they may be erupting through cracks in the ice that covers Europa’s oceans. Members of our SOFIA team recently discussed studying Europa on the NASA in Silicon Valley Podcast.

This is the view of Jupiter and its moons taken with SOFIA’s visible light guide camera that is used to position the telescope.  

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Saturn - March 11 2006

Image Credit: NASA/JPL-Caltech/CCI/CICLOPS/Kevin M. Gill

String Theory

String theory is a fascinating physical model in which all particles are replaced by one-dimensional objects known as strings. This theory says that we live in more than four dimensions, but we can not perceive them.

String theory, is a complete theory and unites quantum physics with Einstein’s general relativity.

On distance scales larger than the string scale, a string looks just like an ordinary particle, with its mass, charge, and other properties determined by the vibrational state of the string. In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries gravitational force. Thus string theory is a theory of quantum gravity.

According to string theory, the reason we can not observe these dimensions is because they are very small and compact (smaller than the plank length 10 −35)

Compactification is one way of modifying the number of dimensions in a physical theory. In compactification, some of the extra dimensions are assumed to “close up” on themselves to form circles. In the limit where these curled up dimensions become very small, one obtains a theory in which spacetime has effectively a lower number of dimensions. A standard analogy for this is to consider a multidimensional object such as a garden hose. If the hose is viewed from a sufficient distance, it appears to have only one dimension, its length. However, as one approaches the hose, one discovers that it contains a second dimension, its circumference. Thus, an ant crawling on the surface of the hose would move in two dimensions.

Compactification can be used to construct models in which spacetime is effectively four-dimensional. However, not every way of compactifying the extra dimensions produces a model with the right properties to describe nature. In a viable model of particle physics, the compact extra dimensions must be shaped like a Calabi–Yau manifold

Another approach to reducing the number of dimensions is the so-called brane-world scenario. In this approach, physicists assume that the observable universe is a four-dimensional subspace of a higher dimensional space. In such models, the force-carrying bosons of particle physics arise from open strings with endpoints attached to the four-dimensional subspace, while gravity arises from closed strings propagating through the larger ambient space. This idea plays an important role in attempts to develop models of real world physics based on string theory, and it provides a natural explanation for the weakness of gravity compared to the other fundamental forces

One notable feature of string theories is that these theories require extra dimensions of spacetime for their mathematical consistency. In bosonic string theory, spacetime is 26-dimensional, while in superstring theory it is 10-dimensional, and in M-theory it is 11-dimensional. In order to describe real physical phenomena using string theory, one must therefore imagine scenarios in which these extra dimensions would not be observed in experiments.

The original version of string theory was bosonic string theory, but this version described only bosons, a class of particles which transmit forces between the matter particles, or fermions. Bosonic string theory was eventually superseded by theories called superstring theories. These theories describe both bosons and fermions, and they incorporate a theoretical idea called supersymmetry.

This is a mathematical relation that exists in certain physical theories between the bosons and fermions. In theories with supersymmetry, each boson has a counterpart which is a fermion, and vice versa.

There are several versions of superstring theory: type I, type IIA, type IIB, and two flavors of heterotic string theory (SO(32) and E8×E8). The different theories allow different types of strings, and the particles that arise at low energies exhibit different symmetries. For example, the type I theory includes both open strings (which are segments with endpoints) and closed strings (which form closed loops), while types IIA, IIB and heterotic include only closed strings.

Branes

In string theory and other related theories, a brane is a physical object that generalizes the notion of a point particle to higher dimensions. For instance, a point particle can be viewed as a brane of dimension zero, while a string can be viewed as a brane of dimension one. It is also possible to consider higher-dimensional branes. In dimension p, these are called p-branes. The word brane comes from the word “membrane” which refers to a two-dimensional brane

In string theory, D-branes are an important class of branes that arise when one considers open strings

D-branes are typically classified by their spatial dimension, which is indicated by a number written after the D. A D0-brane is a single point, a D1-brane is a line (sometimes called a “D-string”), a D2-brane is a plane, and a D25-brane fills the highest-dimensional space considered in bosonic string theory. There are also instantonic D(–1)-branes, which are localized in both space and time.

Duality

A striking fact about string theory is that the different versions of the theory prove to be highly non-trivial in relation. One of the relationships that exist between different theories is called S-duality. This is a relationship that says that a collection of interacting particles in a theory may in some cases be viewed as a collection of weak interacting particles in a completely different theory. Approximately, a collection of particles is said to interact strongly if they combine and deteriorate frequently and interact poorly if they do so infrequently. The type I string theory turns out to be equivalent by S-duality to the heterotic string theory SO (32). Likewise, type IIB string theory is related to itself in a non-trivial way by S-duality

Another relationship between different string theories is T-duality. Here one considers strings propagating around a circular extra dimension. T-duality states that a string propagating around a circle of radius R is equivalent to a string propagating around a circle of radius 1/R in the sense that all observable quantities in one description are identified with quantities in the dual description. For example, a string has momentum as it propagates around a circle, and it can also wind around the circle one or more times. The number of times the string winds around a circle is called the winding number. If a string has momentum p and winding number n in one description, it will have momentum n and winding number p in the dual description. For example, type IIA string theory is equivalent to type IIB string theory via T-duality, and the two versions of heterotic string theory are also related by T-duality.

Black holes

In general relativity, a black hole is defined as a region of spacetime in which the gravitational field is so strong that no particle or radiation can escape. In the currently accepted models of stellar evolution, black holes are thought to arise when massive stars undergo gravitational collapse, and many galaxies are thought to contain supermassive black holes at their centers. 

Black holes are also important for theoretical reasons, as they present profound challenges for theorists attempting to understand the quantum aspects of gravity. String theory has proved to be an important tool for investigating the theoretical properties of black holes because it provides a framework in which theorists can study their thermodynamics.

The big bang theory doesn’t offer any explanation for what started the original expansion of the universe. This is a major theoretical question for cosmologists, and many are applying the concepts of string theory in attempts to answer it. One controversial conjecture is a cyclic universe model called the ekpyrotic universe theory, which suggests that our own universe is the result of branes colliding with each other.

Some things that string theory could explain: Neutrinos would have to have mass (minimum), Decay of Proton, New fields of force (short and long range) defined by some forms of calabi-yau, Explanations for Dark Matter.

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String theory is a very complex and broad area, so this post is only a summary. To better understand, I suggest you read Brian Greene’s books: The Elegant Universe and The Fabric of the Cosmo.

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What’s Enceladus?

Before we tell you about Enceladus, let’s first talk about our Cassini spacecraft…

Our Cassini mission to Saturn is one of the most ambitious efforts in planetary space exploration ever mounted. Cassini is a sophisticated robotic spacecraft orbiting the ringed planet and studying the Saturnian system in detail.

Cassini completed its initial four-year mission to explore the Saturn System in June 2008. It has also completed its first mission extension in September 2010. Now, the health spacecraft is making exciting new discoveries in a second extension mission!

Enceladus

Enceladus is one of Saturn’s many moons, and is one of the brightest objects in our solar system. This moon is about as wide as Arizona, and displays at least five different types of terrain. The surface is believed to be geologically “young”, possibly less than 100 million years old.

Cassini first discovered continually-erupting fountains of icy material on Enceladus in 2005. Since then, the Saturn moon has become one of the most promising places in the solar system to search for present-day habitable environments.  

Scientists found that hydrothermal activity may be occurring on the seafloor of the moon’s underground ocean. In September, it was announced that its ocean –previously thought to only be a regional sea – was global!

Since Cassini is nearing the end of its mission, we are able to make a series of three close encounters with Enceladus, one of Saturn’s moons.

Close Encounters

On Oct. 14, Cassini performed a mid-range flyby of Enceladus, but the main event will take place on Oct. 28, when Cassini will come dizzyingly close to the icy moon. During this flyby, the spacecraft will pass a mere 30 miles above the moon’s south polar region!

This will be the deepest-ever dive through the moon’s plume of icy spray, where Cassini can collect images and valuable data about what’s going on beneath the frozen surface.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com

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