Archive for February, 2012
December 14, 2011 | Author:AAAS member — Freelance Writer Brian Dodson, Ph.D. (Retired)
The discovery of Kepler-22b, an exoplanet orbiting Kepler-22 (otherwise known as UCAC3 276-148830, a sun-like G5 star about 600 light years from Earth) within the “habitable zone,” the region where liquid water could exist on a planetâ€™s surface, was confirmed on December 5, 2011.
Kepler-22b is about 2.4 times the radius of Earth. Its orbital period is 289.9 days, which sets the semimajor axis of its orbit at 0.85 Astronomical Units. Scientists don’t yet know if the newly discovered planet has a predominantly rocky, gaseous, or liquid composition, but its discovery is a step closer to finding Earth-like planets.
AAAS MemberCentral had the opportunity to ask AAAS member Alan Boss of the Department of Terrestrial Magnetism at the Carnegie Institute for Science about Kepler-22b and the status of the quest for exoplanets. Here are his comments.
AAASMC: Can you briefly describe Kepler-22b and its home star?
Alan Boss: The planet is a super-Earth, that is, a planet with a mass perhaps in the range of 10 to 15 times that of the Earth. We do not know of what it is composed, but given its size, about 2.4 the diameter of the Earth, we expect it to be made up of rock, iron, ice, and water. Most likely it has an ocean covering most of its surface. If the planet has an atmosphere, as we expect it does, the average temperature on the surface should be about 72 degrees Fahrenheit.
The host star is a star remarkably similar to our sun — if we were living on the planet and looked up at the star, it would look very much like our own sun. It has just about the same mass and size, though it is a little bit fainter.
AAASMC: What observational methods and techniques have so greatly changed the exoplanetary landscape? Is this new momentum likely to continue?
Boss: 51 Peg b, discovered in 1995, is considered the first bona fide planet found around a sun-like star. Since then, most of the confirmed planet candidates have been found by Doppler spectroscopy, which measures the wobble of the star around the center of mass of the star-planet system. Ground-based transit surveys have found the next largest number of exoplanets. Kepler has now found over 2000 exoplanet candidates, by doing a transit survey from space, so that the Earth’s atmosphere does not interfere with the observations. Kepler will continue to discover large numbers of new exoplanets, especially if NASA grants a mission extension for Kepler.
AAASMC: Kepler-22b was discovered by observing its transit between its star and us. This makes the atmosphere (if any) surrounding the planet available for observational analysis. Is there currently any sign that Kepler-22b has an atmosphere, and if so, what is known about it?
Boss: Exoplanetary atmospheres are studied by how the light of the host star is absorbed by passing through the planet’s atmosphere. An atmosphere on Kepler-22b has not been detected to my knowledge, and it is unlikely to be detected with any current instrumentation.
AAASMC: What upcoming technique and/or missions may tell us more about the nature of Kepler-22b? And what sort of characteristics might we be able to discover, if present?
Boss: Kepler-22 may be too far away for even the yet to be launched James Webb Space Telescope to say anything about the atmosphere of its planet. We need to find planets that are much closer to Earth for us to do a proper follow-up.
AAASMC: The Drake equation attempts to quantify the number of SETI-discoverable civilizations in the galaxy. Two of the multiplicative factors in Drakeâ€™s equation characterize solar systems in ways to which the current spate of exoplanetary discovery is relevant — fp is the fraction of stars that have planets, and Î·e is the average number of planets that can potentially support life per star that has planets. What effect has the recent spate of exoplanetary discoveries had on the Drake equation?
Boss: It means that Î·e is going to turn out to be fairly close to one, though we won’t know for sure what it really is until Kepler finishes an extended mission, perhaps four or five years from now.
- Cutting Edge: Astrophysics and the search for exoplanets with Alan Boss
- NASA: The Kepler Mission
January 6, 2012 | Author:AAAS member — Freelance Writer Brian Dodson, Ph.D. (Retired)
Two recent experiments (ATLAS – A Toroidal Lhc ApparatuS, and CMS – Compact Muon Solenoid) have independently found indications that the Higgs boson may exist (with a mass of about 125 GeV/c2, or roughly 133 times the mass of a hydrogen atom). Although these indications are at about the 2 sigma level of certainty (5 sigma levels are required to claim a discovery), the experimental results suggest that the existence and properties of the Higgs boson should be pinned down during 2012, if all goes well.
Why is finding the Higgs boson so important to the future of high energy physics? The Standard Model (SM) explains the existence of massive particles by the Higgs mechanism, in which a spontaneously broken symmetry associated with a scalar field (the Higgs field) results in the appearance of mass. The quantum of the Higgs field is the Higgs boson. It is the last particle predicted by the SM that has still to be discovered experimentally.
Lisa Randall is the Baird Professor of Theoretical Physics at Harvard University. She has received multiple awards and honorary degrees while pursuing the furthest boundaries of fundamental physics. Randall’s most recent book, Knocking on Heavenâ€™s Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World, contains a chapter on the Higgs mechanism and boson, and several more on the application and potential of the Large Hadron Collider.
AAAS MemberCentral had the opportunity to talk with Randall about the CERN results and the Higgs boson.
AAASMC: Why is determining the existence (or lack thereof) of the Higgs Boson such an important question that it has attracted the professional efforts of thousands of scientists?
Lisa Randall: We understand the Standard Model of particle physics that tells us about matter’s most basic elements and interactions (as observed so far) extremely well. But, as I describe in Knocking on Heaven’s Door, the story of physics has to do with advancing in scales. We know the Standard Model works at the energies we’ve so far observed–it’s been extremely well tested–but we don’t know what underlies it. This is particularly acute for the Standard Model because it assumes elementary particles can have masses. But consistency of our theory tells us that those masses can only arise as a consequence of something called the Higgs mechanism.
If particles had masses from the get-go, the predictions for their interactions at high energy would be nonsense.
(Detecting) the Higgs boson would be, first of all, an experimental verification that the Higgs mechanism is correct. It would also tell us something about what underlying theory was responsible for distributing “charge” in the vacuum in the first place.
AAASMC: Assuming the Higgs Boson is confirmed to exist, will this put the Standard Model on a firmer foundation? Will the adjustable parameters of the SM decrease in number or in range?
Lisa Randall: We will indeed understand the basis for the Standard Model better. We will still be left with questions about particular mass values, for example, but we will know the context in which to try to solve these problems.
AAASMC: If there is no Higgs Boson, is the Standard Model dead? If the Higgs Boson does exist, are we left only with the Standard Model as a viable theoretical framework?
Lisa Randall: The Higgs boson with the particular properties that are currently assumed is a consequence of one particular implementation of the Higgs mechanism. Other implementations have other experimental evidence. And, until we rule those out, we can’t rule out the Higgs mechanism, even if the particular model that predicts a standard Higgs boson is ruled out.
AAASMC: Does the Higgs Boson itself have mass? That is, does it interact with the Higgs field in such a way that it is a massive particle?
Lisa Randall: It does indeed have mass and it is indeed a consequence of its interactions with the Higgs field. Nice question.
AAASMC: Do we have any idea how Higgs Mechanism mediated mass might couple into (generate) general relativistic space-time curvature?
Lisa Randall: The same way all other masses do. Once the Higgs mechanism is in place, particles act like they have mass.
AAASMC: What is the difference between the Higgs Field as an omnipresent background field and the classical notion of ‘an ether’?
Lisa Randall: An ether is supposed to be some actual substance. It would pick out a particular reference frame for example (that in which it isn’t moving). The Higgs field isn’t an actual thing. It is more like a charge. It is a property of empty space–space that is empty of any material matter.
AAASMC: Why was the Higgs Boson nicknamed the ‘God’ particle?
Lisa Randall: Leon Lederman named it that in his book. The Higgs mechanism is important, but so are a lot of other aspects of physics, science, and the world. We can leave religion out of it!
- Explore the latest Higgs data results
- Confused about the Higgs field? This site offers simple, one page explainations.
Lisa Randall recently spoke at a recent AAAS Dialogue on Science, Ethics and Religion Program discussion on what science can explain.
At the 2011 Annual Meeting, Lisa Randall presented on the latest thinking on String Theory, Higgs Boson