Spiral Arms In a Star's Disk Leads To Planets

Credit: www.futurity.org

Picture above shows a disk of gas and dust circulating around a Sun-like star. A structure like spiral arms could mean the existence of planets which haven't been detected yet. Computer simulation has shown that gravitational force from a planet in the disk could disturb the trajectory of gases and dusts which form spiral arms.

Looking For Light Pollution But Not From This Earth

Earth at Night
Credit: C. Mayhew & R. Simmon (NASA/GSFC), NAA/NGDC, DMSP Digital Archive

Astronauts orbiting the Earth often look upon our planet illuminated by lights in night zone. Researchers start to think that scientists should be able to detect light from other civilizations too. Many scientific fictions had ever dreamed about a planet filled with illuminated cities, for example, the galaxy's capital like Coruscant from Star Wars.

Dance of a star: Part III - (Problem 7-8)

by Mee Wong-u-railertkun, David Vartanyan, John Pharo

Credit: www.wikipedia.com

We present the solution to problems from the worksheet "Planet Host Stars Wobble But They Don't Fall Down" (which could be found here.) The outline of this worksheet is as following. First, we are going to see how a planet affects the movement of a star. From that knowledge, we can observe this "weird" characteristic of a star to find exoplanets. In this post, we present solution to question seven and eight.

Dance of a star: Part II - (Problem 4-6)

by Mee Wong-u-railertkun, David Vartanyan, John Pharo

Credit: ESO

We present the solution to problems from the worksheet "Planet Host Stars Wobble But They Don't Fall Down" (which could be found here.) The outline of this worksheet is as following. First, we are going to see how a planet affects the movement of a star. From that knowledge, we can observe this "weird" characteristic of a star to find exoplanets. In this post, we present solution to question four to six.

Dance of a star: Part I - (Problem 1-3)

by Mee Wong-u-railertkun, David Vartanyan, John Pharo

We present the solution to problems from the worksheet "Planet Host Stars Wobble But They Don't Fall Down" (which could be found here.) The outline of this worksheet is as following. First, we are going to see how a planet affects the movement of a star. From that knowledge, we can observe this "weird" characteristic of a star to find exoplanets. In this post, we present solution to question one to three.

Becoming an Astronomer: Alternative Career Arcs

Credit: www.clipartguide.com

The "Becoming An Astronomer" writing project starts out with a blog about my first impression on being an professional astronomer (here). As a second part, David and John interviewed Professor Richard Ellis about his career and profession (here and here). Professor Ellis is a well-established astronomer but what are other paths? Here is where I come in. In this post, I will examine other astronomy career arcs.

Kepler 18 - the packed system

Credit: McDonald observatory
The graphic shows the orbits of Kepler-18b, c, and d around their star compared to Mercury's orbit. The lower graphic shows the relative size of planets to their star and Earth to our Sun.

Kepler Space Telescope hunting for exoplanets found three planets orbiting a star, Kepler-18, which is 10% larger than our Sun but has only 97% of solar mass. There are still planets yet to discovered in this system. What is special for this system is that the planets are in resonant orbiting path.

Those three planets are called Kepler-18b, c, and d. They orbit their star at very close range, even closer than Mercury which is the closest planet in our solar system. Kepler-18b uses only 3.5 days to orbit around the star. It is approximately 6.9 times Earth's mass and two times larger than our Earth. Thus, it is called "super-earth"

From Gas Giants To Rocky Planets

Credit: cdn.physics.com

Picture of a planet which is almost finished its forming process "swimming" through gases and dusts surrounding its mother star. The planet might pull some gases and dusts and form its atmosphere which could disintegrate away when it gets closer to the star. From this process, gas giants could turn in to rocky planets.

As I learned from the Ay20 class today, Kepler mission has found more than 1200 planet candidates. One quarter of that amount are expected to be "super-earth." Several studies suggest that those rocky planets might be a result of failed formation of Jupiter-sized gas giants.

"Drunken" Uranus got sideways tilt from several hits

Credit: www.ifa.hawaii.edu

Uranus has an uncanny characteristic of rotation axis making an angle 98 degree with the axis perpendicular to the solar system plane. In other words, it turns sideway. No other planet has such a huge angle like this, for example, Jupiter is at 3 degree, Earth is at 23 degree, and Saturn and Neptune rotates at 29 degree. How could Uranus get this special configuration?

Becoming an Astronomer: Astronomer Manual

Credit: science.kukuchew.com

As a first part of the how-to-be-an-astronomer writing project, this post contains my initial impression on astronomer career path. Basically, I am trying to guess how could one can be a professional astronomer? Well, I am pretty sure that it is not by a lottery. When does one have to make a decision to become a star gazer? Also, how much knowledge one has to know?

Amazing View of Our Earth

The video above is taken with a special low-light 4K-camera by the crew of expedition 28&29 of the International Space Station (ISS) from August to October, 2011. 

If you wonder where the shooting locations are, here is the list in order of appearance:

1. Aurora Borealis Pass over the United States at Night

2. Aurora Borealis and eastern United States at Night

3. Aurora Australis from Madagascar to southwest of Australia

4. Aurora Australis south of Australia

5. Northwest coast of United States to Central South America at Night

6. Aurora Australis from the Southern to the northern Pacific Ocean

7. Halfway around the World

8. Night Pass over Central Africa and the Middle East

9. Evening Pass over the Sahara Desert and the Middle East

10. Pass over Canada and Central United States at Night

11. Pass over Southern California to Hudson Bay

12. Islands in the Philippine Sea at Night

13. Pass over Eastern Asia to Philippine Sea and Guam

14. Views of the Mideast at Night

15. Night Pass over Mediterranean Sea

16. Aurora Borealis and the United States at Night

17. Aurora Australis over Indian Ocean

18. Eastern Europe to Southeastern Asia at Night

FYI, aurora borealis are the northern lights while aurora australis are the southern lights. Both of them have almost identical features.

Proto-stars and the pre-main sequence

By Mee Wong-u-railertkun, John Pharo, David Vartanyan

Credit: www.wikipedia.com

In this week of Ay20, we learn about the mechanism of how a star is formed. Picture above is an artist's interpretation of the stage while a star is formed. The proto-star sits in the middle surrounded by a cloud of mass accreted into the star forming the accretion disk. Two yellow jets of mass are excreted from the star to maintain the angular momentum. Here, we solve problem number 4 on the worksheet "The Formation of Stars" located here.

Fried Egg In Space

Credit: www.space.com

Anyone up for a fried egg?

Astronomers use The Very Large Telescope (VLT) to take a picture of a giant star which is classified as a super rare type called the yellow supergiant. It is the most detailed picture and is the first time to see two layers of dust around the supergiant. The star and its dust are so similar to a fried egg that astronomers give its a nickname, "Fried Egg nebular."

Calculation Of A Big Boom

Credit: NASA/CXC/JPL

Infrared image of Tycho's Nova which is the remnant of Type Ia supernova.

Because of the work of our guest last Wednesday, Dr. Ryan Foley, and some events earlier this year, I feel that it is time to study something about the supernova.

When a high-mass star reaches the end point of its life, it explodes into a big ball of flame called supernova.  Astronomers have calculated that around 3 massive stars will go through a special Type Ia supernova every thousand year in our Milky Way galaxy. In other words, within distance of several thousand light year from Earth, a fair amount (20+) of stars is about to give a big boom. The picture above shows a nice picture of the remnant of supernova. It is beautiful to observe from some distance but we don't want to get too close to the explosion. That is why we are trying to determine when a star will blow up.

Did Baptistina Asteroid Cause Dinosaur's Extinction?

Credit: www.tickreel.com

There are many theories behind the extinction of dinosaurs 65 million years ago. One theory is that an impact of an asteroid causes it but no one is sure what type or how the asteroid heads to the Earth. From the study in 2007 by using data from observatories in visible-wavelength range, the culprit is the type of asteroid called "Baptistina."

Stellar Properties From Afar

by Mee Wong-u-railertkun, Nathan Baskin, John Pharo, David Vartanyan

Credit: apod.nasa.gov Info about this picture is presented below.

We present the solution to the first question from the worksheet "Stellar Properties From Afar."

We are given the following information about the sun,
1) The angular diameter of the sun is 0.5 degrees.
2) The astronomical unit (AU), distance between the Earth and the Sun, is approximately 1.5 * 10^13 cm.

Determining the Astronomical Unit from Mercury's Transit

by Mee Wong-u-railertkun, John Pharo, David Vartanyan

We were given a picture of Mercury's transit taken by NASA's Transition Region and Coronal Explorer (TRACE) which is a polar low-Earth orbit satellite. The picture looks like this.

Planet Surface Temperature

by Mee Wong-u-railertkun, John Pharo, David Vartanyan

Abstract

We investigate the relationship between the energy emitted from a star and the surface temperature of a planet. We assume that a star and a planet are perfect spheres and they are perfect blackbodies, i.e. power absorbed equals to power emitted. Moreover, they radiate isotropically. Later, we compare between the theoretical surface temperature of the Earth with the real data.

A Brief History of Palomar Observatory

Credit: www.astro.caltech.edu/palomar

Since we, Ay20-ites, are going to Palomar Observatory tomorrow (Sunday 10/16), I should dig out some information before hand. Inside the big dome, the temperature is kept around 30 to 40 degree so we better bring a jacket!

The Palomar Observatory is located in north San Diego County, California around 100 miles south of Caltech. Its coordinates are 33 degree 21' 21''N and 116 degree 51' 50'' W with the altitude of 5618 feet or 1712 meter. It is a world-class instrument for astronomical research that is owned and operated by the California Institute of Technology. The observatory is consisted of five telescopes including the 200-inch telescope.

Recalling Blackbody Radiation

by Mee Wong-u-railertkun, John Pharo, David Vartanyan

Abstract

We present the solution to the Black Body Radiation worksheet problem 1, from week 3, recalling basic ideas of black body radiation from energy density to specific intensity and flux. In the first part, we investigate the contradiction of the units of energy density. In order to convert from energy density to intensity and flux, we have to study the concept of solid angle. These equations are used frequently in astronomy.

On The Way Back

After finishing Ay20 helping session, Iryna, Nathan, David, and I walked back together while talking about the "Phinney-unit." Then, Iryna pointed at a bright spot in the sky near to the Moon and asked, "Is that a planet?" Nathan replied, "Yeah, that's Jupiter. Actually, if you look through a binocular, you can see the Galilean moons." So, after grabbing a binoculars at Nathan's room, we looked up in the sky and saw the following picture.

Basically, we saw the jupiter with two moons to the right. That makes me wonder, which two moons are we looking at? So, when I came back to my room, I opened up the program called Stellarium and checked it out.

Those two moons turn out to be Ganymede and Calisto. We can't see Io and Europa, may be because they are close to Jupiter today (or I just have bad eyes.)

Observation Planning For The Very Large Telescope and The Keck Telescope

by Mee Wong-u-railertkun, John Pharo, Eric Mukherjee, Nathan Baskin

Abstract

We present the solution to the Celestial Sphere and Observation Planning worksheet problem 4, from week 2, picking range of declination that both the Very Large Telescope (VLT) and The Keck Telescope can observe galaxies at visible wavelengths for at least 6 months a year. In order to choose a small area of the sky to be observed very deeply, it should be seen by as many telescopes as possible. We use the fact that stars, from Earth’s point of view, circle around the North Celestial Pole (NCP) and the South Celestial Pole (SCP) to determine behavior of stars at different declinations seen from VLT and Keck.

Estimating The Radius of The Earth

by Mee Wong-u-railertkun

Abstract

We present how the radius of the Earth could be measured using only a stopwatch and a place where the horizon can be seen, e.g. beach. A stopwatch and a difference in height provide the curvature of the Earth by watching a sunset and assuming that the Earth is a perfect sphere. Since a person’s height is much less than the radius of the Earth, one small error in a measurement could mean a large inaccuracy in the final answer.

"Wet" Mars

Credit: www.esa.int

           

            On June 2^nd, 2003, European Space Agency (ESA) launched a probe named Mars Express to investigate, well, Mars. Now, it is orbiting its target at the orbital inclination of 86.3 degree with a period of 6 h 43m. On board, SPICAM spectrometer works by receiving a light from Mars, putting it through grating, and looking for a pattern in a spectrum to determine what does Mars’ atmosphere consist of. From a discovery published in Science by Maltagliati et al (2011), Mars’ atmosphere is supersaturated with water vapor.

Looking Outside My Window

           Because of more free time on weekend, I, just recovered from jetlag, finally have a chance to look outside from my room’s window at night. With daylight, the view from my room is a typical parking lot with some trees having picturesque mountain range as a faraway background.

            But tonight is different. As I stared outside my window while working on math problem set, I can see only darkness with some streetlights. Since I turn on the light in my room, the sky outside is completely dark – not a single star shows up. Then, I notice a tiny orange spot. It’s definitely not an airplane or Jupiter since it stays stationary. What else could it be? (I’m pretty sure that it’s not an UFO also) So, I take another picture from my digital camera and compare with the one taken during a day. It’s the area indicated by a red circle. (The camera makes everything look so much brighter than what is seen by naked eyes) Suddenly, I realize that the light must come from one of the most famous places in astronomy history – the Mount Wilson Observatory.

             The Mount Wilson Observatory (MWO) is located on the peak of, well, Mount Wilson at 5715 foot above sea level. It contains two important telescopes: the 60-inch Hale telescope and the 100-inch Hooker telescope.

            The Hale telescope was once the largest operational telescope in the world allowing many scientific procedures, e.g. parallax measurements, nebula photography. The Hooker telescope, also, was once the largest telescope until the 200-inch telescope at Palomar Observatory was built (which is also called Hale telescope.) Here, Edwin Hubble, a prominent astronomer, made the discovery of redshift which leads to the conclusion that the universe is expanding.

            It’s true that the MWO appears as a tiny dot outside my window. However, its place in the astronomy history gives me some inspiration (at least enough for me to write this post!) To be true, the scene of parking lot with an orange flickering spot is not bad at all.

T.K.O. Mathematics

          There are plenty types of martial art – boxing, taekwondo, sumo, judo, aikido, kung fu and solving math problems. Hold on a second, mathematics? Even though they might come from different fields, math and martial arts are more similar than differing. Picking up a fight is a good analogy to solving problems. (Proof? We, at least once, were “knocked out” by a math problem on an exam. Don’t tell me that you never had that experience!)

            In boxing, both amateur and professional, there are plenty of rules and settings – size of the ring, referee, using only fists, time per round etc. If a boxer violates a rule, he/she might get a point stripped off or even disqualified. In order to box, a boxer needs to have appropriate equipment. A paradigm of problem solving nowadays is similar to a rigorous boxing fight. Every step has to be beautiful, strict and perfect. Addition or multiplication must be exact, no room for estimation.

            However, not every fight in this world is staged in an arena. Actually, there are more “street fighting” than official boxing match. In street fighting, no rule applies – dirty tricks are even acceptable. It doesn’t matter how the strikes were conducted. Final result is the most important goal – not the beauty of a kick or the style of fighting.

            Sanjoy Mahajan, a professor at Massachusetts Institute of Technology, broke a paradigm of problem solving by introducing the “street fighting mathematics.” In some situations, the top priority is the final answer, not the pathway. Frequently, life attacks you with rough questions. Most of the time, an exact answer is not required to survive; a rough answer will do the trick. Thus, if you confront with problems in unofficial situation, you are free to make some rough assumptions and estimations. The answer might not be 100% correct but, with reasonable assumptions, it should turn out to be in the same order of magnitude. For example, a student solves a problem and discovers the Earth’s radius to be 2000 km. Even though the right answer ranges from 6353 km to 6384 km, the student’s answer is good enough for street-fighting mathematics.

            For practicing, there are couples of question for street-fighting mathematics in Ay20 first set. (The link is http://www.astro.caltech.edu/~jrv/Ay20/ws/ws_collab_sfmath.pdf) But don’t forget, even though it is a convenient way to solve a complicated problem, street-fighting mathematics is casual. In official exams, e.g. Caltech finals, it is fine to use street-fighting trick to figure out a problem roughly but not entirely. Otherwise, you would get a T.K.O. from a professor, if not an F. 

Little and Humble

            In the past summer, I met a guy from Malaysia who is a fairly nice person. Even though he doesn’t share an interest in astronomy or science, he does have something interesting to share – religion.

He is a worshiper of the Holy Platypus. This belief comes from an idea that, since the existence of god is not completely disproved, and if a god did exist, why not he takes a form of a platypus. Humans, selfish and arrogant, often consider god to be human-like. If the god really had created all living creatures, shouldn’t He share characteristics with plenty types of life form? And that’s where the platypus comes in. It shares characteristics of a bird with a duck-like beak; it shares characteristics of a mammal with fur and mammal glands; it shares characteristics of an amphibian with web-like feet; it shares characteristics of a reptile with its egg-laying and water-based habitat properties.

With a long description of the reason behind the Holy Platypus, I was struck by the main idea – be humble. As I looked back more and more, I found many signs and identifications of humans’ arrogance. The first thing came to my mind is a picture of an alien. From popular media, either movies or novels, an alien appears to share great similarities with human – two eyes, standing on two feet with head as the highest organ, two arms, two feet, ability to see only in visible light etc. Look around, even only on this Earth, there are millions of species and life forms. It would be disappointing that in the universe, plenty of time larger than our Earth, exists only a human-like creature. In movie, a creature maneuvering a spacecraft never has rose-like form. There is no reason why that couldn’t happen. Moreover, we assume that highly intelligent life tends to have similar size to human. May be there is a civilization at atomic or galactic level.

            Not only in popular media, but also astronomy that humans’ arrogance shares a great portion. Earth was believed to be a center of everything – on a pinnacle. Later, we knew that, actually, the Earth orbits around the Sun. That’s not too bad – we are down just to the Sun but on a higher priority than millions other stars. However, the more we explored, the more minute and less important we are. The Sun orbits around a gigantic black hole and is part of the Milky Way galaxy; our galaxy also orbits in a bigger cluster. It’s a long way from Earth as a center of the universe to the position where Earth is now.

            Modern technology emphasizes how “not” important we are. You, me, Cahill building, the whole Caltech, or even this Earth are made up of matter – an “ordinary” matter. However, it turns out to be that matter is just a small fraction of what created the universe – dark matter, dark energy. We use the word “dark” since we cannot see them. May be to other civilizations in the universe, if there is one, we are the “dark” matter ourselves.

In the end, I would like to share a famous picture “Pale Blue Dot.” The picture was taken by the spacecraft Voyager 1, destined to leave our solar system, from approximately 6 billion kilometers away. Around middle of the brown band, there is the Earth as a tiny dot in a vast dark space. Aren't we so "little"? On the day that humans can abandon their hubris and become more humble, the Holy Platypus would provide us the Unified Theory.

Picture from: fettss.arc.nasa.gov