(Astro)Physics

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Fermi Summer School 2014

I asked Dr. Perkins, “Why does Fermi have sunglasses?”

Response: “Because Fermi is cool.”

I don’t know what to say to that. On a related note, I am slowly (emphasis on the word slowly) working on my first first-author paper on a gamma-ray survey of small, nearby molecular clouds. It won’t revolutionize anything, but it is a good study and highlights some issues the community is talking about. Maybe I’ll get my butt in gear and write about it some day. And other things. I have a post on the Asimov Memorial Debate and another on a talk about inflation and the BICEP2 results from last week. But for now … enjoy Fermi with sunglasses:

And if anyone is interested, the Fermi Gamma-ray Space Telescope team is hosting another summer school! It lasts almost two weeks and costs $1000. You get to enjoy good company at a nice University of Delaware getaway while learning the ins-and-outs of the Fermi instruments and science done with the data. I went last year, and it was a blast.

The focus last year was on dark matter. This year will apparently focus on the center of the Galaxy: the bubbles, this whisper of too many gamma-rays (this excess fits a dark matter profile remarkably well), modeling a very busy region … it should all be good stuff.

Mar 4

Cosmos time

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Cosmos: A Spacetime Odyssey premiered at a special event today, and on television on Sunday.

The show aims to popularize science, and I think it will do a better job than the original did. Regardless your opinion on the host, Neil deGrasse Tyson, he is a great choice. He gives a face to the traditionally underrepresented minorities in the sciences. He isn’t just another white guy telling you what’s up. Here is a black man that everyone listens to and everyone respects.

Perhaps a year ago, I attended a seminar at the American Museum of Natural History where the speaker talked about underrepresented minority participation in astronomy. Early in the talk, she presented the following graph, which shows the number of Ph.D.s granted to underrepresented minorities year by year:

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From this paper concerned with the underrepresented minorities in astronomy.

Tyson gets up and points to the screen, “This one was me!” He pointed at the blue blip at 1991 (check his CV). That data point was him. No other black person in the entire country received their Ph.D. in astronomy that year. Talk about lonely.

I hope this series will do more than promote that science is as natural as breathing and that our world contains plenty of wonder. I hope that people become inspired to think clearly. Perhaps having Tyson as a host will show that being black or hispanic is not a bad thing, that you can do astronomy too. I hope that the established majority in astronomy (the white people) will start to actively encourage diversity rather than turning a blind eye to it. I hope it is time for a change.

The oldest star in the universe? Maybe, maybe not

I’ll talk about this article twice, if I get to the second one. I first want to comment on the “oldest star found.” The star found has the lowest fraction of iron ever found. Iron and other elements heavier than helium were all made in stars. Specifically, those elements were made after the beginning of the universe. Hydrogen and a lot of helium were created during the beginning: in the first few minutes of existence. So as a rule, gas with a lower fraction of elements heavier than hydrogen and helium is older gas. There has been less time for other stars to “pollute” the gas with heavier elements.

Does that mean this is a very old star? Not necessarily. If it is a low mass star, then it could potentially have formed near the beginning of the universe and still be burning bright. The fill paper (Nature) includes discussion on possible pollution by prior stars. This occurs when a massive star explodes and mixes its enriched guts into the neighborhood.

But do they consider different mixing? Inhomogeneous mixing, for example? Or the fact that galaxies, even today, have gas falling into the galaxy from outside. This gas often takes the form of pristine atomic hydrogen. Can these clouds get shocked during its passage through the Galaxy and start forming stars? It could be a reserve of unenriched gas from which the star could form.

What are the kinematics of this star — how is it moving? Have we performed stellar evolution simulations to see how old it is? The answer is … sort of. The fraction of lithium is significantly different from what was created in the Big Bang. They take this as evidence that the star must have gone through a particular stage of evolution which uses up lithium. Ok … but lithium is easy to kill.

Well, I’ll poke through the paper a bit more and see what I can find. I’m not entirely convinced this is the oldest star so far found. But I’ve been wrong before.

Black hole firewall solution?

There was a paper published an New Year’s day which claims to solve the black hole firewall paradox. All right, by now there are a handful of hopeful solutions. What is different about this one?

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I wonder what’ll happen if I go over there.

The paradox arose as a direct result of Stephen Hawking’s calculation that black holes give off radiation. Black holes aren’t black because of the strangeness of quantum mechanics. Four physicists from the Kavli Institute for Theoretical Physics at UC Santa Barbara found a contradiction: the theory of gravity predicts that anything passing into a black hole should not notice anything wrong, besides the usual stretching. In order for the black hole’s radiation to abide by physics, the object can NOT get into the black hole. Or else any information about the object will disappear.

So for physics to be physics, an person has to simultaneously enter the black hole without trouble AND smash into a wall and be prevented from entering the black hole. Hmm…

Recent headlines state that Stephen Hawking has proclaimed that black holes do not exist in the traditional sense. The media blew that out of proportion. He said that black holes do not have eternal event horizons. Instead, they have temporary “apparent” horizons, which allows for the black hole to evaporate and eventually release everything that ever went into it. That is not saying that black holes do not exist.

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Nobody understands me…

Among the many proposed solutions is the suggestion by Sabine Hossenfelder that the paradox stands on shaky grounds. There are certain assumptions which went into the formulation of the paradox. They include that the black hole Hawking radiation is “pure,” the radiation comes from near the surface of the black hole, and observers see nothing strange when passing through that surface. The second assumption comes from Hawking’s calculations using quantum mechanics near a black hole, and the last assumption is required by our theory of gravity.

It turns out the radiation is not pure. It is mixed and messier than previously thought. That was result of Hossenfelder’s paper mentioned in the previous paragraph, along with two other previous papers. In other words, there is no paradox, it is just wrong. Well, it certainly got people interested in black holes again and it pushed research forward significantly in the past year.

See Ethan Siegel’s blog for more explanation. I haven’t gone over Hossenfelder’s paper; I do not know quantum field theory in curved spacetime yet (I hope to learn soon), so I wouldn’t be able to appreciate the paper.

astronomnomy:

I won’t provide screenshots as that would be impolite to those participating in the conversation but - over the last few hours there has been frenzied discussion on the Professional Astronomers’ Facebook page about that Type 1a supernova in M82 and they may have already found the progenitor (star that exploded). There’s also been a lot of work on Twitter, too.

Scientists are using social media to do work on amazingly short timescales. Whoop!

It will probably be a while before the gamma-ray signature changes noticeably.

Project Idea

I know this has been done at other universities, but not at mine as far as I know. Some of my students last semester showed some interest in astrophotography (and why not? it is awesome). They can pursue it in a couple of ways.

York College holds a public observatory night typically the second Wednesday of every month during the fall and winter semesters. Professor Paglione brings an 8” computerized telescope (Schmidt-Cassegrain). I can encourage my students to go and then possibly take images by holding their smartphones up to the eyepiece. This is called afocal photography.

Please don’t point the telescope in anyone’s window.

Or I can have them use a publicly available robotic telescope. If they wanted, perhaps they could contact a privately owned robotic telescope and request time. Hopefully the telescope can make the raw images available, so the student can really play around with the image. Example telescopes available:

Admittedly, the last one would be a little involved for an introductory astronomy course, but the option is available. It requires writing a 2 page scientific proposal and knowing the details of observing conditions.

They can at least virtually hang out with observers. The google hangout “virtual star party" is good for those of us trapped in New York City when the local amateur astronomy clubs are not active.

Another option is if the student already has a telescope, then they can start doing things on their own. How about harvesting a store-bought webcam? They can be used to take phenomenal images of planets and the Sun. Or simply point their cameras up and take pictures of the night sky.

I think these options will go over well, even though most people will not do them. The fact that these options are available helps make the class more free and enjoyable. I’m sure I have missed other options. What else could I have the students do?

It’s likely the universe extends forever in space and will go on forever in time. Our results are consistent with an infinite universe.

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New measurements from the BOSS study tell us the shape and size of our universe to within one percent accuracy. Turns out, it’s essentially flat, and probably infinite.  (via brookhavenlab)

No edge, like a BOSS

(via jtotheizzoe)

I searched most of the likes/reblogs and I am a little surprised the comment wasn’t already made. The fact that the universe is flat does not tell us that the universe is infinite in extent! After all, a torus (donut) is considered flat, too! However, if an ant were to crawl in a straight line in any direction, the ant would always come back to where it started. Flat, never ending, but not infinite.

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(wiki) Here we start with a flat sheet. Fold it into a tube, then bend the tube until the two ends meet. We have taken a flat sheet and turned it into a donut.So a donut is actually flat. Silly geometry.

This does say that if the universe repeats itself like the donut, then the size is significantly bigger than the observable universe, or else we would have seen correlations in the sky either by seeing similar patterns of galaxies or in the cosmic microwave background.

The infinite is still a hard pill to swallow. Nothing we deal with normally is infinite. Does the universe extend infinitely far in all directions? I cannot answer that. Nor does this new data.

Just saying.

[1401.2204] A Suggestion for MOND

I have not read this yet, so I should probably refrain from commenting, but I will anyway. I’ll quote some of the abstract:

We present an alternative theory with two forces, one the traditional Newtonian inverse-square, and the other that falls off inversely with distance at large distances.

Now regular Newtonian gravity is a single force that falls off as the inverse-square of the distance:

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This new force goes like:

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Where I don’t know A, they may have it or may simply leave it unknown. They claim that the effect of the new force is suppressed near stars. Fine; at small distances, the (1/r2) term dominates anyway. My point:

In the book The Physical Foundations of General Relativity by Dennis Sciama, the author considers such a new force. Sciama is well known in relativity theory as worked in astronomy, as well. His doctoral adviser was Dirac, and he was adviser to a number very talented and well known astronomers and physicists (see Sciama’s wiki). Note: I should also finish the book, I got about halfway through.

I’ll skip details. Sciama considers a 1/r force and concludes that this extra force simple acts like inertia! It is the reason for the equivalence principle (inertial mass = gravitational mass). In other words, consider Newton’s 2nd Law:

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According to Sciama, there is no “m" on the right side of this equation. Rather, this mass comes from the gravitational interaction with everything else in the universe! Or something like that.

Reaction to this paper: at the very least, a special case has been done. The special case recovers general relativity from Newtonian gravity. Therefore, the general case will necessarily modify general relativity. Perhaps this paper warrants a read?

Jan 6

infinity-imagined:

City lights photographed from the International Space Station and Neurons imaged with fluorescence microscopy.

Source images; Cities (1) (2) (3) (4) (5), Neurons (1) (2) (3) (4) (5)

Check out the concept of “centrality" in network theory. This is simply an efficient way of storing and transporting things, clearly. Most of the time, both cities and neurons grow organically, with connections to neighbors. These connections are meaningful and must, therefore, be as efficient as possible while maintaining the meaningfulness.

So while these images are amazing and captivating, it is not necessarily surprising to me. That gravity shows the same structure is more interesting. The following is perhaps not the greatest example, but it was easy to find:

The mass of a galaxy cluster may, then, grow in a similar fashion to neurons. An initial seed drawing in material from around it: the seed grows. The bigger object is able to draw more things to it. The filaments seen in the right image come naturally from simulations of how gravity works. It is all about the connections between two things: in this case, how one thing draws material from it’s immediate environment.

Jan 2

The nights sky was stunning! Unfortunately, I didn’t get as much Milky Way time as I wanted because of the moon (full moon to 3rd quarter during the trip) and weather. Beautiful landscape, though.

I met Jack Newton (his winter house is shown with two domes). He is super friendly; I definitely want to visit him and his wife’s bed and breakfast in Canada this summer (Bed and Breakfast in Osoyoos).

Expect more writing this semester as opposed to last! I felt sort of dumpy last semester. I think this vacation was a good thing. More writing and more photos to come.

Note: the middle photo is sunrise. The last photo, with the cloud flopping over the mountain: I hikes on that mountain just the day before. Portal, AZ is a wonderful place. The Milky Way photos were all taken at Casitas de Gila in Gila, NM (Gila is pronounced hee-lah).

Jan 2

vic-torl:

rabraha3:

I’ll add some more when I can. I went on a trip to Arizona and New Mexico where I was able to see the Milky Way for the first time in a while.

The first image features Jupiter and the Beehive (I think) poking over the mountains. The second image includes M 31, the Andromeda galaxy. There aren’t touched up or modified. Just a 20 second and 30 second exposure, respectively. Location, location, location. The night sky is amazing.

You should visit my little farm here in Australia. I live away from populated areas, and my night sky is incredible, all year.

Wow, that sounds amazing! After visiting these places, I want to go visiting places around the world. Maybe I’ll apply to the NSF fellowship which can pay me to do work in Australia (EAPSI)…

Jan 2

I’ll add some more when I can. I went on a trip to Arizona and New Mexico where I was able to see the Milky Way for the first time in a while.

The first image features Jupiter and the Beehive (I think) poking over the mountains. The second image includes M 31, the Andromeda galaxy. There aren’t touched up or modified. Just a 20 second and 30 second exposure, respectively. Location, location, location. The night sky is amazing.

The Beehive cluster (Praesepe). Located east, and a bit north, of Gemini, this open star cluster is in the same naked-eye field of view as the radiant point of the Geminid meteor shower.

And Jupiter, again next to Wasat in Gemini. But Jupiter has moved noticeably over the course of several days. This is a crop of the original, which suffers from significant vignetting (I need to start taking flats). The nearby bright stars of Pollux and Castor are visible in the originals, which facilitate comparison.

And last, on the way back from imaging the stars, I stopped to image this nice icicle formation. This is Fort Tryon park, near the Cloisters (my star images are taken in the parking lot of the Cloisters, under the harsh streetlights). I should start processing my images more.

Dec 9

Searching for our place

We went to the Moon in 1969. Now the talk is on Mars again. NASA is planning on going back eventually. Denis Tito wants to help fund a cruise by Mars before 2020, SpaceX wants to put people on Mars around the same time, Mars One wants to establish a permanent colony on Mars not long after. These events will get a lot of attention if the happen. It is interesting to imagine what will happen if we do go.

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Going to Mars. Image from gizmag article; credit: Space X

There is no doubt that it will inspire another generation to do great things; the STEM fields will be hot again. Will it have the same affect as the first moon landings? An estimated 500 million people watched the first moon landing [spaceline]. The world’s population was only 3,600 million, so almost 1/6th the world’s population tuned in! Everyone figured that Mars was next. It was the inevitable next step. The human exploration of space was a welcome distraction from the bitter cold war.

Mars was envisioned to be the next step. And now that private companies are willing to risk their own capital on a venture, the trip to Mars is looking more and more inevitable. I claim that landing on Mars will not have the same impact that the first Moon landing had. It is the first human to set foot on another planet, sure. We can hype it up all we want. But it will take such a long time, that it won’t be quite as impressive at those first steps on the Moon. It is going to happen, but we are dragging our feet (for some good reasons).

There is yet one thing which will capture the imagination again. Like the first Moon landing, NASA and its affiliates can yet again change the way we perceive our role in the cosmos. Landing on Mars would extend our reach further into the cosmos. But there is a lingering question which people have imagined for generations now. Are we alone in the universe?

Everywhere we look on Earth, we find life. At the bottom of the ocean, inside ice, miles down buried in rock … exists things alive and kicking. If we find life somewhere else in the solar system, the chances that life arose anywhere else in the universe instantly becomes a certainty. And how the possibilities abound. Life on Earth has something in common. We are connected through our use of DNA.

Earthrise is not the first color images of the Earth taken from space.

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For many, images such as this inspired feelings of unity. There are no political borders visible, no strife nor violence. Everything on this planet shares one home; we are part of something bigger than ourselves. Finding life on another world will engender the same feelings. Only this time, we would be connected to the entire universe of worlds.

The search for life has been stated to be one of the prime motivators for many of NASAs missions, especially in recent years. A primary mission objective for the Curiosity rover, in all its nuclear powered glory, is the search for signs of life on Mars. The stated objectives are dry and typical science-y jargon. But really, it is there to assess the possibility that Mars once had life and the possibility of supporting future life [National Geographic]. The Kepler spacecraft, which has found about 3,538 planet candidates during its mission [NASA]. But Kepler can only see a small fraction of possible planets. If we remove that effect, an estimated 20 billion Earth-like planets exist in our own Milky Way galaxy [Time]. The primary goal for the spacecraft was to try to find other planets similar to the Earth, at least in size.

By far, the most interesting topic for the majority of my students is the possibility of life in space. A discovery will bring with it a host of ethical dilemmas and biological possibilities which we have barely begun to imagine in our science fiction. It will launch our consciousness into the vast universe. The universe will continue to be uninviting, but no longer desolate. We won’t be isolated in our little corner of the universe, alone with just our thoughts.

Or there is nothing and we are alone.

Dec 8
I have more posts coming, I swear! One is basically complete (I want to tweak the end), I have a good idea and a lot of the thinking done, and I have another good idea where I play devil’s advocate. The 2nd one seems fund to me, I claim that a recently published paper does not show what it claims to show. The work is probably right, but the interpretation is … shaky.
For now, enjoy this image of Jupiter I took last night. The seeing conditions were crap, I was looking through some clouds, but that’s all right. Jupiter is in the constellation Gemini; I labeled the star next to it. Look closer, and we see a smudge inside the brightness halo of Jupiter: it is the combined light of Callipso and Ganymede. Look even closer, and there is a little bump coming off of Jupiter on the same side as those moons — that’s Europa.
I was testing out an IR remote and a new and crappy tripod for my camera. I am pleased with the results, all things considered. Making star trail images will be painful, since I can’t have the shutter open more than three or four seconds at a time (too much light pollution), so I won’t experiment with that a lot.
And I’m thinking of buying a telescope. Yes, even from New York City, there are things to see. The Andromeda Galaxy may be 3.5 V mag, but I can photograph it with 5 streetlights shining straight into the camera.

I have more posts coming, I swear! One is basically complete (I want to tweak the end), I have a good idea and a lot of the thinking done, and I have another good idea where I play devil’s advocate. The 2nd one seems fund to me, I claim that a recently published paper does not show what it claims to show. The work is probably right, but the interpretation is … shaky.

For now, enjoy this image of Jupiter I took last night. The seeing conditions were crap, I was looking through some clouds, but that’s all right. Jupiter is in the constellation Gemini; I labeled the star next to it. Look closer, and we see a smudge inside the brightness halo of Jupiter: it is the combined light of Callipso and Ganymede. Look even closer, and there is a little bump coming off of Jupiter on the same side as those moons — that’s Europa.

I was testing out an IR remote and a new and crappy tripod for my camera. I am pleased with the results, all things considered. Making star trail images will be painful, since I can’t have the shutter open more than three or four seconds at a time (too much light pollution), so I won’t experiment with that a lot.

And I’m thinking of buying a telescope. Yes, even from New York City, there are things to see. The Andromeda Galaxy may be 3.5 V mag, but I can photograph it with 5 streetlights shining straight into the camera.