Cepheid + Light Echo = Accurate Distances

Cepheid + Light Echo = Accurate Distances

I am so so frustrated that I can’t get the full journal article associated with this press release. I’m going to have to do some emailing tomorrow to see if someone can get it to me. Here is what has me excited. In a new paper in Astronomy and Astrophysics (which my Uni doesn’t get) with Pierre Kervella as lead author,  the distance to a Cepheid variable has finally been accurately measured in a method so simple I can’t believe it wasn’t done before. The binocular-bright Cepheid RS Pup is embedded in a nebula. As it’s light varies, it causes the dust and gas to also vary in brightness. By measuring how long after the star varies in brightness the blob of gas and dust varies in brightness, it is possible to tell how far...

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4 stars within 6 AU

4 stars within 6 AU

The universe keeps throwing neat stuff up for our telescopes to look at. A team lead by Evgenya Shkolnik (University of Hawaii), has observed a tight system of 4 stars crammed within 6 AU of one another – If located in our solar system, all four stars would fit within the orbit of Jupiter! The system consists of 2 tight binaries, with the two binary systems orbiting the center of mass for all 4 stars. There is less than a 1 in 2000 percent chance that stars of this type could form in this 4-star type of a system, and this is the first time a system like this has been found. The two sets of binaries are very tight. One pair orbits a point between the two stars (their center of mass) with a separation of 0.06 AU, and the other set has a maximum separation of...

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Type 1a Supernoave: A Non-Standard Candle

Type 1a Supernoave: A Non-Standard Candle

One of the most exciting discoveries of astronomy in recent years was the measurement of an acceleration term in the universe’s rate of expansion. Announced by both the Supernova Cosmology Project at the Lawrence Berkeley National Laboratory and the High-z Supernova Search Team, these results at once confirmed one another an revolutionized how astronomers view the universe. This discovery meant, quite simply, that our universe will expand forever, tearing itself apart and ever increasing rates. Someday, the expansion of space will carry everything we are not gravitationally attached to so far away so fast that the light will get red-shifted beyond all easy (and perhaps even all possible) reach. (image credit: NASA, ESA, CXC, JPL-Caltech, J. Hester and A....

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Giants and Dwarfs with Barium

I’m beginning to think that a large fraction of the astronomical community is in pre-semester stars chaos. The number of press releases has radically slowed, and the journal articles just don’t seem to be flying as fast and furious as normal. Admittedly, this is a personal impression, and while I have data to support the number of press releases, it could simply be some wishful thinking that makes the number of papers seem fewer. That said, what the papers lack it number, the make up for in titles. For instance, consider the following: Ruthenium and hafnium abundances in giant and dwarf barium stars by D.M. Allen and G.F. Porto de Mello. So imagine with me if you will: Before you expands a waiting room of sick dwarves and sicker giants who all happen...

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The Sun and its Danger Zone: The Chromosphere

One of the deeply confusing aspects of our Sun (and other stars) is their temperature structure. Starting in the core, the Sun is millions of degrees kelvin and supports nuclear burning. As you leave the nuclear burning core and climb first into the radiative zone and then the convective zone, the temperature systematically drops until it reaches a temperature of several 1000 degrees at a star’s surface. This makes sense. In the core, the gas is being compressed under the pressure of all the upper layers of the star gravitationally pushing down. The pressure allows nuclear reactions to release energy in a form that can heat things up: specifically light. That light then interacts with stellar material, being absorbed and reabsorbed over and over as it loses energy and goes on a random walk through the radiative region (think light bulb heating the air around it), and then (think of the lava lamp material above a light bulb) it also gives off energy as it heats cells of material at the base of the convective zone that rise and convectively give off heat as the cells rise (and then, when cool, sink back down).

So far so good.

The problem is, as you then move away from the surface of the Sun, you enter regions where the temperatures again go up – A lot – like back to millions of degrees hot levels of a lot!

And no one fully knows why. This is a very counter intuitive situation. Imagine that the surface of a lava lamp was 23C and the air half an inch away was 200C! In a press conference Wednesday, astronomers announced that they think they may have found a starting point for understanding what is going on in this bizarre situation.

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A Brown Dwarf, A Black Hole, and 4 Jets …

A Brown Dwarf, A Black Hole, and 4 Jets …

phot-24-07-preview.jpgOpening my press release email folder this morning, I found what could have been the beginning of a good joke if I were actually a skilled humorist. So a black hole and a brown dwarf both start to form. As the black hole consumes his parent star, he shots powerful gamma ray jets off to announce his arrival. At the same time, a little brown dwarf, with a not so little planet, works to spring out of its proto-stellar cloud, and it blows with its feeble little jets as hard as it can to announce its arrival. The black hole looks at the brown dwarf and laughs and says “[insert something witty and demeaning]”. The brown dwarf, not one to be discouraged, just smiles and states “[Something thoughtful and witty that puts the black hole in his place]”

Not being a good humorist, I will not try to fill in the blanks. I will simply work to explain how two such very different objects can announce their formation via the same physical process.

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