That time of year thou may’st in me behold When yellow leaves, or none, or few, do hang Upon those boughs which shake against the cold, Bare ruin’d choirs, where late the sweet birds sang. In me thou see’st the twilight of such day, As after sunset fadeth in the west, Which by-and-by black night […]
It’s been a while since I posted anything reasonably technical, largely because I’ve been too busy, so I thought I’d spend a bit of time today on a paper (by Livadiotis & McComas in the journal Entropy) that provoked a Nature News item a couple of weeks ago and caused a mild flutter around the internet.
Here’s the abstract of the paper:
In plasmas, Debye screening structures the possible correlations between particles. We identify a phase space minimum h* in non-equilibrium space plasmas that connects the energy of particles in a Debye sphere to an equivalent wave frequency. In particular, while there is no a priori reason to expect a single value of h* across plasmas, we find a very similar value of h* ≈ (7.5 ± 2.4)×10−22 J·s using four independent methods: (1) Ulysses solar wind measurements, (2) space plasmas that typically reside…
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In my previous blog posts, I highlighted that today astronomers have been working collectively on a single project. Researchers need to communicate their work with both other astronomers and the non-astronomers. Here, other astronomers refer to a group of professionals who work as peers to review the original work. American Astronomical Society (AAS) publishes two journals where astronomers can share their work. They are: the Astrophysical Journal and the Astronomical Journal. The Astrophysical Journal focuses on astrophysics and related research work. The Astronomical Journal primarily publishes work done in observational astronomy and related fields. Both of these journals charge their readers to access the articles published there. This blog discusses whether astronomical research work can be accessed at a low cost. Ethical guides for the AAS journals can be accessed here: http://bit.ly/ZHYjDK.
Analysis of the Thesis
Astronomers submit their research papers in either one of the journals mentioned above. The reviewers give feedback. In many cases, the writers and the reviewers exchange several notes to increase the clarity of their scientific language used in the papers. Now, one can wonder why reviewing and publishing require money. The peer review process involves several stages. They are:
- Formatting the paper
- Posting the paper to an online server
- Forming an editorial board and reviewing the work of the peers
These days, stage #3 is considered to be the most time consuming one, which increases the cost of publication. I ignored stage #2 because maintaining an online server requires a fixed amount of money. Forming an editorial board, which will be mostly familiar with the research content described in a paper, is considered to be a moderately difficult task. Anyone from the researchers’ home institution cannot take part in this process.
Currently, American Astronomical Society reviews a submitted paper following the model of a single reviewer. Since astronomical sciences and researches have become a global collaboration among several groups of scientists and professionals, a single reviewer model seems to be outdated. In order to engage a group of peers who will qualify to go through a particular paper, one can think of recruiting a group of referees. Now, does this increase the publication cost? It does not. Distributing tasks among referees will be helpful for publishing a superior quality paper. The peer review will be less time-consuming. As the tasks are distributed among a group of referees, the incentive should be offered accordingly.
Many young researchers start their career by replicating experiments done by others. If the science described in a paper fails to produce the exact results (within the margin of error predicted in the results section), the young researchers can question about the merit of the work in a published paper. When an expert group gets involved in peer reviewing they can easily pinpoint the strengths and the weaknesses of the paper.
A well-written and well-received paper makes science journalists’ work easier. Scientists get money to do their research work primarily because the government funds them. Scientists’ responsibilities lie on reporting their science work in less ambiguous terms. A group of referees can notify the researchers about ambiguous terms they introduced in their papers.
A single reviewer model is helpful in guiding the researchers to improve their science writing. Depending on the complexity of the work, if a group of peers evaluate the merit of the research work, then publishing research work will be much quicker. The rest of the researcher communities will be aware of the work through this.
A group of referee can lower the publication cost of publishing an astronomical paper. This will be beneficial for researchers to access others’ work at a minimal cost.
The Hubble Space Telescope was launched into space in 1990. Due to a technical problem that occurred during its installation, earlier images taken by the space telescope had some deformities in them. This problem was resolved in 1993. NASA published the first picture taken by the Hubble Space telescope back in January 1994.
Since then, the Hubble Space Telescope has been capturing a significant number of images of various celestial objects including stars and galaxies, which help to understand how our universe, galaxies and stars behave at a large-scale.
NASA’s Spitzer Space Telescope was launched in 2003, primarily aiming to do infrared observing. Infrared light is a form of electromagnetic radiation. As most of the infrared radiation gets absorbed by the earth’s atmosphere, the Spitzer Space Telescope was also launched into space to make observations in the infrared spectrum of the electromagnetic radiations.
Let’s remind ourselves a few definitions before we go farther. Stars are primarily composed of hydrogen, which fuses into helium. During this process energy is released. It causes the stars to shine in the night sky. Our sun is a star and we reside in a galaxy named the Milky Way. Assuming the universe is finite, the scientists found that the early universe was a very different place than the present observable universe. Right after the Big Bang, the universe was immensely hot. Eventually, the universe cooled off, and hydrogen atoms were formed.
Last November, NASA announced that a joint collaboration between the Hubble Space Telescope and the Spitzer Space Telescope discovered the most distant galaxy in the observable universe. The galaxy was cataloged as MACS0647-JD. Surely, it does not have any fancy name like our own galaxy or our neighboring galaxy, Andromeda.
In astronomy, looking at a distant object is simply analogous to looking back in time. Astronomers found that the most distant galaxy was formed when the universe was only about 430 million years old; whereas, currently the universe is about 13.7 billion years old.
In a research paper published by Coe et al. from the Space Telescope Science Institute, the researchers claimed that their team found the most distant galaxy in our observable universe. The visual images were obtained using the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS). For the infrared part, the Spitzer Space Telescope’s InfraRed Array Camera (IRAC) was exposed over 5 hours. As the object is really far away, the exposure time increases.
This galaxy was directly viewed because gravitational lensing helped us to see this distant celestial object. In principle, light can be bent by gravity. In the case of this distant object, there are numerous massive sources lie in between the light source and us. One can consider other galaxies and stars to be the intermediate massive sources, which bend light.These massive sources can also magnify the source you are aiming to look at. This phenomenon is known as gravitational lensing. The distant galaxy is visible to us because the intermediate mass-sources bend light and magnify its real size.
Finding this galaxy successfully testified various models on gravitational redshift. When a fast paced object moves towards the observer, its frequency gets shorter and the wavelength gets compressed. Blue light has a shorter wavelength than red light. That is why blue shift refers to an object moving towards us with a high speed. On the other hand, when an object moves away from us, it exhibits a red shift. The wavelength gets stretched away. Red light has a longer wavelength than blue light. In reality, gravity has the same effect on mass-less photons or light particles. By testing various models for gravitational redshifts, researchers concluded that this distant object first emitted light from it when the universe was only about 430 million years old. This observed galaxy had a really high red shift.
Researchers think that this distant object can be studied using the futuristic James Webb Space Telescope. This will reveal many unknown facts about the formation of big structures such as how primordial galaxies and stars shape our universe.
MaxIM DL image processing software is used to calibrate astronomical images. Astronomers often prefer to come with algorithms on different programming languages to stack a large number of images and remove noises from them. This entry will help astronomy enthusiasts to process images on their computers using the MaxIM DL over programming languages based on two criteria: easiness and the time it takes to process images. This software requires a few simple steps to follow for creating a calibrated image. To learn more about MaxIM DL software, please click here.
In order to calibrate astronomical images obtained through Charged-Couple Device (CCD) photometry, one needs to shoot three types of correction frames. They are: Bias frames, dark frames and the flat frames. Let’s remind us what the purpose is of taking images of these three different frames. Bias frames are taken to remove the readout noise and computer interference from the picture. Readout noise will give you information on the number of electrons are produced upon signal accumulation on the CCD chip.
In general, all CCD chips are manufactured in a way that already have some offset voltage in them. One needs to remove this preset voltage in order to improve the image quality. Here is a picture of the master bias frame, which was created by combining 10 bias frames of the same exposures.
To simply put this, dark frames remove thermal noise from images, which is caused due to temperature difference between the CCD chip and the environment.
A Master Dark Frame
Shooting a flat frame is one of the most difficult tasks. The picture used in this post was taken by illuminating a box. A flat frame gives information on the light path obscured by the dust sitting on the chip.
Taking bias frames is a must when someone is doing astronomical observations. Bias frames are done in 0 seconds exposure with the camera shutter closed. In order to create a master image on MaxIM DL, one needs to follow these steps:
1. Click on the MaxIM DL launch icon.
2. When the MaxIM DL is open, click on the process menu.
3. Click on set calibration under the process menu.
4. Select the folder which contains bias frames.
5. Click on the auto generated clear old option.
6. Select combine type of the images be median.
In order to create a master dark frame, one can follow the same procedures (1-6). Obviously, one needs to choose the proper folder, which contains dark frames (4) in it. A master flat frame can be created using the same procedures described above, but one needs to keep in mind that color filters response to light differently. That is why we take flat frame exposures in all available filters.
After creating the master frames for three corrections, one can finally calibrate the science image. To achieve it, follow the following steps:
1. Keeping the MaxIM DL window open, click on file.
2. Open images you want to calibrate ( It is recommended to open 20 frames at a time, if your image is 3073X2048 pixels wide).
3. Under the process menu, select calibrate all.
4. Wait when the images are being calibrated. You will have your calibrated science images within two minutes. After this, you are ready to analyze the reduced data. Here is a picture of a calibrated field taken in R Filter.
The red star indicates an SX Phoenicis star named XX Cyg.
Why Choose MaxIM DL
In a nutshell, calibrating science images using MaxIM DL is painless and it reduces noise from the science images fairly quickly. On the other hand, using a freeware such as AstroImageJ performs poorly for reporting detailed information about the steps taken to reduce noises from the images. An experienced programmer will like using programming languages, but the MaxIM DL software offers various statistical tools, which are useful for data analysis.
Values in Observational Astronomy
In the early seventeenth century, Italian astronomer Galileo Galilei first used the telescope to look at the celestial objects. He made several important observations including phases of the Venus and the Jovian moons, which changed the contemporary worldview. The geocentric model of the solar system was challenged by his observations. Later, the heliocentric model was accepted. As time progressed, observational astronomy became popular in Europe. The Dutch and the English pioneered in the field of big optical telescopes. Among them, Sir William Herschel built a 20 feet long reflector one. He also proposed a theory on how big the visual universe is and he created a sky atlas of the Milky Way.
Later in the nineteenth century, observational astronomy research geared toward the United States of America. A new group of professional astronomers emerged during this period. For example, the Smithsonian Astrophysical Observatory, the Astronomical Society of the Pacific, the American Astronomical Society, the American Association of Variable Star Observers were founded then. Later in the twentieth century, Edwin Powell Hubble discovered that the farther a galaxy appears, the faster it recedes from us. This is known as Hubble’s law. In the last decade, the Hubble Space Telescope observed the farthest object in our observable universe.
Observational Astronomy has been playing a great role in unfolding the mystery of the universe. Professional astronomers from all over the world are working as a group in various projects. The rest of the blogpost will highlight three major observational projects, which aim to reveal the formation and evolution of the universe.
The American Association of Variable Star Observers (AAVSO) undertook the APASS (the AAVSO Photometric All-Sky Survey) back in 2010. This ambitious project aims to prepare a sky atlas of the entire northern and southern hemisphere in five different optical filters. This project will include stars which have the apparent magnitude 17 or higher.
Readers probably figured out that today’s research work involves collaboration among scientists at the highest level. So far, observational astronomy projects discussed in this blog focused mainly on observations done in the visual wavelength of the spectrum. Since late 1960s astronomical observations have been made in the entire electromagnetic spectrum of the light, such as X-rays, gamma-rays, microwaves, radio waves, etc. The NASA’s James Webb Space telescope is a visionary project, which will capture images in the IR (infrared) band of the spectrum. This project was threatened due to budget cut. The Webb telescope will be funded by the NASA, the Canadian Space Agency (CSA), and the European Space Agency (ESA).
The last project mentioned here aims to do radio astronomy at a massive scale. The Square Kilometre Array project has been considered to be the largest radio astronomical telescope, which will be built in Australia and South Africa. Scientists across the Asia-Pacific nations, China, India, the UK, Sweden, Italy and Germany are hoping to reveal the mystery of galaxy formation, super massive black holes and many more through this project.
Readers can see that astronomy is an empirical science. People often ask whether these researches have any direct implication in real life. To address that concern, we can think of how the telecommunication science has been improved in the last decade. We cannot simply ignore the fact of having access to better computing and software relies on astronomers’ endless effort in developing algorithms, which analyze a huge data set efficiently. Astronomers inspire and challenge the computer scientists and it is because of the research that we have cell phone cameras, which can take pictures and transfer them to another device instantaneously.