May 23, 2011

Endings and New Beginnings

I am moving this blog from Blogger and to Tumblr. There will be no more updates here, and all new updates will be at this new location.

Essentially, the reasoning behind the move was that Blogger was no longer a good fit for the way I wanted to maintain this blog. Don’t get me wrong, Blogger is a wonderful platform, and still has a few advantages over Tumblr. However, what it came down to for me was that Blogger was not implementing a few core features that I desperately wanted to use, such as greater control over editing the theme.

This is a particularly emotional decision for me since this was the place where I first started writing seriously about astronomy and space, and the experience has taught me so much. Even though this move does not signify at all an ending of what I love to do, it is the ending of a big chapter of it. But with that ending, has come a new beginning, one that will allow me to better achieve the goals I have wanted for the project. Something I have started to value, especially recently, is the ability to remain agile and quickly adopt something new and better for me, and not hold onto the past for its own sake.

With that, this location should remain completely functional for archival purposes, but all new updates will be found here. Thanks for all your support.

March 25, 2011

New Candidate for Coldest Known Star May Help Blur the Distinction Between a Star and a Planet

An artist’s impression of the CFBDSIR 1458+10 star system.
The star in the background is the candidate for the coldest known star.
Image: ESO/L. Cal├žada

There may be a new candidate for the coldest known star, an object classified as a brown dwarf with a surface temperature of only about 100 degrees Celsius. The temperature is close to the boiling point of water which is hot when compared with temperatures obtained on the surface of the Earth. In cosmic terms, however, this temperature is remarkably cold, in fact about 55 times colder than the surface of the Sun. Yet, the title for the coldest star rests on an important distinction: is this particular object a star, and can the definition of a star actually change?

This particular cool object, named CFBDSIR 1458+10B, is part of a binary star system at a distance of about 75 light-years from the Earth. Both parts of the binary system are classified as brown dwarfs1, and are about the size of Jupiter. They orbit each other at a separation distance of about 3 AU, or 3 times the distance from the Earth to the Sun, in a time period lasting 30 years. The system was detected last year by the Very Large Telescope, part of the European Souther Observatory in Chile. At first it was thought to be a single star with a very low temperature2, but the presence of a smaller even colder companion made it much more interesting.

A color image of the star system made using four different filters at near-infrared wavelengths.
Captured at the Keck II Telescope in Hawaii. Image: Michael Liu, University of Hawaii.

Brown dwarfs are often considered failed stars, and are objects that are not able to gather enough mass so that their gravity can trigger the Hydrogen-1 fusion reaction that takes place in the cores of most other stars. Smaller brown dwarfs, due to their low mass, begin to more closely resemble gas giant planets. There is still a lingering question on whether or not this object can, or even should be considered a brown dwarf and a star. The most simple distinction between stars and planets is whether or not there is any fusion taking place inside the star. By this definition, the cutoff point occurs at about 13 times the mass of Jupiter. At this mass, objects start to fuse deuterium and can be considered stars. Since the mass of this object is between 6 and 15 times the mass of Jupiter, there is a possibility that nuclear fusion is not happening. There is a new argument brought up by some astronomers that the formation of an object should factor into whether it can be a classified as a star or not, which is much more difficult to measure and determine. Brown dwarfs, and other stars as well, are formed due to the collapse of interstellar gas and dust. Planets on the other hand are thought to be formed as a disc of dust accretes into distinct bodies around a star. CFBDSIR 1458+10B is thought to be formed through the first process, and it is argued that it should subsequently be thought of as a star.

This candidate for the coldest star known is interesting in that it represents a potential shift in defining the lower mass limit for stars. What particularly excites me about this discovery, though, is not the change in classification that it might bring but that it is a new example of a type of object that we do not understand very well yet. This object lies very close to the boundary between a large gas giant planet and a brown dwarf star, and subsequently exhibits properties from both types of objects, especially in its atmosphere. Hot brown dwarf stars obtain their color mostly through the presence of sodium and potassium atoms in their atmospheres. In cooler brown dwarfs, and likely in an object like this one, it is expected that the sodium and potassium atoms join together into molecules, like potassium chloride, and are subsequently removed from the atmosphere. Due to this effect, their colors should be different. There is also the possibility of the presence of water clouds in the atmosphere, much more typical of gas giants. Regardless of whether or not this object is a star, it is undoubtedly very interesting.

Footnotes:

1: The name of the other object is CFBDSIR 1458+10A, and the name of the entire system is CFBDSIR 1458+10. Yes, astronomers are a witty bunch…
2: Even then, the low temperature would have placed it as the third coldest star known.

February 19, 2011

Kepler: An Evolution and a Shift

The announcement by Kepler a little more than two weeks ago was undoubtedly huge. The discovery and confirmation of a really interesting planetary system consisting of six confirmed planets was released. This announcement was coupled with the discovery of over 1200 other planet candidates. In the time since the announcement, I have been struggling to fully comprehend the immense size of the numbers. Now, I have started to just realize that the numbers may not be the most interesting idea to keep in mind. We also have to step back from the recent news and see that the Kepler announcement may be the representation of the start of a new era and a giant shift in looking for life outside of the Earth.

At one level this Kepler announcement represents the evolution of our exoplanet detecting skills, and the number of planets discovered does tell a huge story. The rapid pace we have achieved in detecting exoplanets is no small feat. About 15 years ago, the first extrasolar planets, about the size of Jupiter, were just beginning to be detected. Before these discoveries, many scientists doubted ever being able to detect an extrasolar planet. Now, including great contributions being made by the Kepler spacecraft, we may have about 1500 planets detected and confirmed soon, a remarkable jump especially since many of these planets are much smaller than Jupiter. The Kepler announcement is also encouraging in that its discoveries are only being made in a single patch of sky. This area covers only about 1/400 of the area of the entire sky. Admittedly, other patches of the sky may not be as rich of stars containing planets as Kepler’s field of view, but it is extremely likely a huge amount of planets are still waiting to be discovered.

What really excites me though is that this announcement marks a shift in our search for extraterrestrial life. Although Kepler’s mission is to look for planets and not life, I feel that  the scientific community and the rest of society is particularly interested in exoplanets because they may offer clues as to whether Earth life is an anomaly or the norm. This is why in every news piece I have read about the announcement so far, the fact about the list of potential Kepler candidates containing 54 planets about the size of the Earth located in the habitable zone is particularly emphasized. Any of these planets could contain life that is similar to ours and therefore their discovery captures our attention. The Kepler mission in particular represents a new era, in which our search for life outside our solar system is passing from a passive approach to a more active approach. In the era before Kepler, finding life outside of the solar system meant relying on projects such as SETI (Search for ExtraTerrestrial Intelligence). SETI attempts to detect signals that intelligent life may be broadcasting. This relies on the lifeforms having evolved and progressed as a society far enough so that they are able to regularly broadcast signals in the specific frequency ranges that Kepler is able to detect. Kepler, on the other hand, is taking a more active role. Kepler actually searches for planets that may be hospitable to life. Afterwards these planets can be examined in detail for traces of life, which do not necessarily have to be left behind by intelligent life.

The change, I think, is extremely important. Our search for life has become much more efficient and likely more fruitful. It as if we no longer have to face an expansive ocean hoping intensely that something in it will make contact with us. We can now wade in, start turning over rocks, and examine what we find. This is why I have been very obsessed and excited about the announcement. I believe when looking back after a number of years, the Kepler project and announcements like this will mark the point in history when we no longer sat back, but stood up and got our feet wet.

February 11, 2011

Kepler Discovers New Planetary System and Announces Over 1200 Planet Candidates


The Kepler spacecraft started doing its work in May 2009, continuously watching the stars contained in a patch of sky with the hope of being able to discover exoplanets. Just recently, the Kepler team had a very exciting set of announcements resulting from this diligent work.

An artist’s conception of the Kepler-11 system.
Image: NASA/Tim Pyle
Comparison of Kepler-11 orbit sizes
and our Solar System’s orbit sizes.
Image: NASA/Tim Pyle
One of these was the discovery and confirmation of a newly found planetary system with six confirmed planets. Their star, Kepler-11, is a sun-like star, located about 2000 light years away from Earth. This star is only the second known so far to host multiple planets outside of our solar system, and now holds the record for hosting the most known planets. Plus, all of its planets have extremely tight orbits. The largest orbit is smaller than that of Venus in our solar system, while the other five orbits are even smaller than that of Mercury. This results in the most compact planetary system yet discovered in addition to the largest planetary system by number. Furthermore, the planets are bigger than the Earth, with the largest planet comparable to the size of Uranus and Neptune in our solar system. Still five of the six newfound planets are among the eight smallest extrasolar planets found so far. These interesting facts and characteristics of the system also lead to some clues about the formation and the dynamics of the system.

Kepler detects planets by measuring for drops in the light of their stars as they pass across, called the transit method (This method is detailed further in this previous post about Kepler). Measuring the changes in how much the light drops, at what times, and in what patterns can allow astronomers to calculate characteristics of the planet like size, distance from the star, and number of planets. Since the planets are located extremely close to each other in this particular system, five of the six planets produce significant perturbations on each others orbits that are measurable by Kepler. As they are detected, they will let the researchers calculate estimates for the masses of these planets. Further transits in the future will allow the estimates to be further refined. Adding this information with the sizes of the planets leads to the density of the planets that in turn could allow other researchers to hypothesize about the makeup of the planet. The densities of the planets in the Kepler-11 system appear low, suggesting that they are gaseous planets composed of light elements. These would be similar to planets like Neptune in our solar system rather than terrestrial planets like Earth. The conclusions also give suggestions about the formation of the planetary system. Presence of a large amount of light gas likely means that these planets were formed early in the history of their system. Finding out more about the formation of other planetary systems, such as this one, could, in turn, lead to valuable realizations about our own system.

Locations of Planet Candidates in Kepler FOV
Image: NASA/Wendy Stenzel
Yet, probably the more important announcement could be that in addition to these confirmed planets, Kepler has found over 1200 other planet candidates. These are discoveries that result in data that may be similar to that produced by the presence of an exoplanet, but needs to be verified and confirmed. The amount of actual planets from the list will almost definitely be less, but, more importantly, by how much? Some analyses are suggesting that about 80 to 90 percent of the objects on this preliminary list could be planets. This means that the amount of exoplanets discovered (currently about 530) could go up very significantly, by around 1000 (or about 200% of the current number) if the early analyses end up being accurate. Plus, in that preliminary list of planets, 54 are located in the habitable zone of their stars. This zone includes the orbits where a planet could potentially hold liquid water. The radius of one of these is about 0.9 times the size of the Earth’s, while the radii of four others are less than two Earth radii. A planet more Earth-like than any discovered so far may be among these data.

Results like this one are hugely important. They suggest the presence of the hundreds of other star systems, some unique systems like Kepler-11, or perhaps others also like our own solar system.

January 10, 2011

A Supermassive Black Hole in a Dwarf Galaxy

A supermassive black hole exists in the center of our galaxy, with an incredible mass on the order of 4 million times that of the Sun. Our galaxy is not alone; most large galaxies also possess very large black holes as well. This leads to some interesting questions in galaxy formation and development: Which comes first, the black hole or the galaxy? Does a galaxy develop first, and then later, a massive black hole forms? Or does a black hole appear first, around which a galaxy much later forms? The discovery of a supermassive black hole could help answer that question.

A composite (X-ray, optical, and radio) image of the Henize 2-10 dwarf galaxy.
Image: X-Ray (NASA/CXC/Virginia/A. Reines et al);
Radio (NRAO/AUI/NSF); Optical (NASA/STScl)

Amy Reines, a graduate student, and her colleagues at the University of Virginia initially wanted to study the rapid star formation in the Henize 2-10 galaxy. The dwarf galaxy possesses many starburst regions and interesting newly formed super star clusters, where star formation has recently taken place. However, while looking back at the data, Reines and the researchers realized that there were signs of a black hole in the center of the galaxy. Radio radiation was originating at the spot, suggesting the presence of jets of radiation resulting from matter falling into the black hole. Further data from the Chandra X-ray Space Telescope revealed a high amount of X-ray radiation in the region, more evidence for the existence of a black hole.

Looking at black holes in the center of other galaxies has shown that there is a correlation with the mass of the central bulge in the galaxy and the mass of the black hole in the galaxy center. This has led some to speculate that a bulge in the galaxy was necessary for a black hole to form. The discovery of a black hole, with a mass about 2 million times that of the Sun, in Henize 2-10 challenges that notion. Henize 2-10 lacks a bulge, and being a dwarf galaxy, it has a low mass, only 10% of the Milky Way’s mass. It also has an irregular shape, with a rapid rate of star formation. These characteristics suggest that Henize 2-10 could be an early phase in the evolution of a galaxy and the answer to the above questions could be that black holes develop before galaxies form. With that though, we still have to keep in mind that the black hole in Henize 2-10 might be an outlier. Until we find more examples, the questions are still open.

January 1, 2011

2010 Going Into 2011

Looking back, I have to say 2010 was a great year both for my blog and myself. I covered many interesting topics on my blog, including quite a few about exoplanets. Among other things this year, the Hubble celebrated its 20th birthday, the rover Spirit got stuck on Mars, and there is increasing evidence for an ocean on Mars. More personally, I started heavily using my binoculars, finished up my high school senior project on orbit determination, and started college this year.

I can’t yet say what I will write about in the coming year. This summer I decided to write some reflections about this blog, and I still feel that my purposes for this blog are evolving. I can’t predict exactly what kinds of things will be on my blog in the coming year. I also cannot predict all of the exciting discoveries that will undoubtedly be released this year. Right now, I just know that I can’t wait to start my first astrophysics class in college in this coming semester, and also share some exciting posts on this blog.

Happy new year everyone!