Astro-Drummer

Astronomy

What we know (and don’t know) about exoplanet Kepler-22b

by on Feb.04, 2012, under Astronomy, Science

December 14, 2011 | Author:AAAS member — Freelance Writer Brian Dodson, Ph.D. (Retired)

This artist's conception illustrates Kepler-22b, a planet known to comfortably circle in the "habitable zone" of a sun-like star. (Photo: NASA/Ames/JPL-Caltech)

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 planet’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 Drake’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 ηe 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 ηe 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.

Related links:

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Why the Higgs boson is important

by on Feb.04, 2012, under Astronomy, Science

January 6, 2012 | Author:AAAS member — Freelance Writer Brian Dodson, Ph.D. (Retired)

Real CMS proton-proton collision events in which 4 high energy electrons (green lines and red towers) are observed. The event shows characteristics expected from the decay of a Higgs boson but is also consistent with background Standard Model physics processes. (Image: CERN)

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 Heaven’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!

More information:

video Lisa Randall recently spoke at a recent AAAS Dialogue on Science, Ethics and Religion Program discussion on what science can explain.

video At the 2011 Annual Meeting, Lisa Randall presented on the latest thinking on String Theory, Higgs Boson

 

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First Soyuz Launch from Arianespace’s Guiana Space Center

by on Oct.20, 2011, under Astronomy, Science

Arianespace’s first launch of the Soyuz rocket from the Guiana Space Center (CSG) in French Guiana will orbit the first two satellites in Europe’s Galileo satellite navigation system. This mission, to be followed by the first launch of Europe’s Vega light launcher in 2012, signals the introduction of the most complete family of commercial launch services in history.

The Launch will occur October 20, 2012 at 6:34 AM EST. Launch will be live in the window below. Hopefully I am not too late!

We will be broadcasting on Twitter as well (http://twitter.com/arianespace) for the “Live tweet” of the Soyuz mission from 3:00 am EST. Please feel free to follow us to be a part of this histroric moment.

With the Soyuz launcher operating out of the Guiana Space Center in French Guiana, Arianespace will be the only launch services provider in the world capable of launching all types of payloads to all orbits,from the smallest to the largest geostationary satellites, along with clusters of satellites for constellations and missions to support the International Space Station.

The Soyuz at CSG program carries on the long-standing partnership between France and Russia, one that kicked off in 1996 with the creation of the joint venture Starsem to operate the Soyuz launcher at Baikonur. This strategic partnership gives Europe a medium launch vehicle, while allowing Russia to increase the number of Soyuz launches. A total of 23 successful Soyuz commercial launches have already been performed at the Baikonur cosmodrome, and three more are still scheduled in 2011-2012. All versions of the Soyuz launcher have carried out 1,776 missions to date, from both Russia and
Kazakhstan.

The European Space Agency (ESA) first began studying the possibility of Soyuz launches from the Guiana Space Center in early 1998, and officially started this program in 2004. Construction work in French Guiana kicked off in 2005 and the first Russian components started arriving in 2008.

ESA named French space agency CNES prime contractor for this project, overseeing the development and qualification of the Soyuz launch complex (ELS) at the Guiana Space Center. Russian space agency Roscosmos was in charge of the Russian segment of the program, and also coordinated the work of all Russian companies involved.

Arianespace managed the supply of Russian systems and coordinated the work by Russian companies during the development phase. The «Soyuz at CSG» program is already a business success, with Arianespace having won 14 launch contracts even before the first launch.

On its first mission from CSG, Soyuz will place the Galileo IOV-1 PFM and FM2 (In Orbit Validation) satellites, named Tiis and Natalia, into circular orbit at an altitude of 23,000 kilometers. The satellites were built by a consortium led by Astrium GmbH.

Arianespace and its subsidiary Starsem earlier orbited the experimental satellites Giove-A and Giove-B, enabling Galileo to secure its allocated frequencies.

More information regarding this mission can be downloaded here in a PDF provided by Arianespace.

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Early Earth may have had two moons

by on Aug.04, 2011, under Astronomy, Science

The Earth-Moon system is unique, and it believed that without our Moon life would not have had a chance to form. However how the Moon came to exist is a bit of a mystery. One theory is they formed together  each sweeping up material as the pair orbit the Sun. Yet another theory is a large impact on Earth tore away a nice sized chunk of debris that later evolved to become our Moon. A new theory has been published in Nature Magazine in that a large Mars sized body struck the Earth and two large chunks appeared eventually coming together to form our Moon. This could explain why the side of the Moon facing us has many low lying areas and the far side of the Moon has a thicker crust ans is more cratered. Below is the article from Nature.

A previous collision with a smaller companion could explain why the Moon's two sides look so different. Martin Jutzi and Erik Asphaug

Earth once had two moons, which merged in a slow-motion collision that took several hours to complete, researchers propose in  Nature today.

Both satellites would have formed from debris that was ejected when a Mars-size protoplanet smacked into Earth late in its formation period. Whereas traditional theory states that the infant Moon rapidly swept up any rivals or gravitationally ejected them into interstellar space, the new theory suggests that one body survived, parked in a gravitationally stable point in the Earth–Moon system.

Several such ‘Lagrangian’ points exist, but the two most stable are in the Moon’s orbit, 60° in front or 60° behind.

Traces of this ‘other’ moon linger in a mysterious dichotomy between the Moon’s visible side and its remote farside, says Erik Asphaug, a planetary scientist at the University of California, Santa Cruz, who co-authored the study with Martin Jutzi, now of the University of Berne.

The Moon’s visible side is dominated by low-lying lava plains, whereas its farside is composed of highlands. But the contrast is more than skin deep. The crust on the farside is 50 kilometres thicker than that on the nearside. The nearside is also richer in potassium (K), rare-earth elements (REE) and phosphorus (P) — components collectively known as KREEP. Crust-forming models show that these would have been concentrated in the last remnants of subsurface magma to crystallize as the Moon cooled.

What this suggests, Asphaug says, is that something ‘squished’ the late-solidifying KREEP layer to one side of the Moon, well after the rest of the crust had solidified. An impact, he believes, is the most likely explanation.

“By definition, a big collision occurs only on one side,” he says, “and unless it globally melts the planet, it creates an asymmetry.”

Asphaug and Jutzi have created a computer model showing that the Moon’s current state can be explained by a collision with a sister moon about one-thirtieth the Moon’s mass, or around 1,000 kilometres in diameter.

Such a moon could have survived in a Lagrangian point long enough for its upper crust and that of the Moon to solidify, even as the Moon’s deeper KREEP layer remained liquid.

Meanwhile, tidal forces from Earth would have been causing both moons to migrate outward. When they reached about one-third of the Moon’s present distance (a process that would take tens of millions of years), the Sun’s gravity would have become a player in their orbital dynamics.

“The Lagrange points become unstable and anything trapped there is adrift,” Asphaug says. Soon after, the two moons collided. But because they were in the same orbit, the collision was at a relatively low speed.

“It’s not a typical cratering event, where you fire a ‘bullet’ and excavate a crater much larger than the bullet,” Asphaug says. “Here, you make a crater only about one-fifth the volume of the impactor, and the impactor just kind of splats into the cavity.”

Like A Pancake

In the hours after the impact, gravity would have crushed the impactor to a relatively thin layer, pasted on top of the Moon’s existing crust. “You end up with a pancake,” Asphaug says. The impact would have pushed the still-liquid KREEP layer to the Moon’s opposite side.

Apshaug’s theory isn’t the only attempt to explain the lunar dichotomy. Others have invoked tidal effects from Earth’s gravity, or convective forces from cooling rocks in the Moon’s mantle.

“The fact that the nearside of the Moon looks so different to the farside has been a puzzle since the dawn of the space age,” says Francis Nimmo, one of the authors of a 2010 paper in  Science proposing tidal forces as the cause.

But despite his competing model, Nimmo (a colleague of Asphaug’s at Santa Cruz, but not an author of the new study) calls the new theory “elegant”.

And Peter Schultz of Brown University in Providence, Rhode Island, calls it “interesting” and “provocative”, despite his own theory involving a high-angle collision at the Moon’s south pole, which he believes would have pressed crustal material northward to form the farside highlands.

“All this is great fun and tells us that there are very fundamental questions that remain about the Moon,” he says.

NASA’s upcoming GRAIL mission, designed to probe the Moon’s interior using precise measurements of its gravity, may help figure out what happened billions of years ago. “But in the end,” Schultz says, “new lunar samples may be necessary.”

Author: Richard Lovett

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Hubble Discovers Another Moon Around Pluto

by on Aug.03, 2011, under Astronomy, Science

Hubble discovery image of P4

These two images, taken about a week apart by NASA’s Hubble Space Telescope, show four moons orbiting the distant, icy dwarf  planet Pluto. The green circle in both snapshots marks the newly discovered moon, temporarily dubbed P4, found by Hubble in June. P4 is the smallest moon yet found around Pluto, with an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Pluto’s largest moon Charon is 648 miles (1,043 km) across. Nix and Hydra are 20 to 70 miles (32 to 113 km) wide. The new moon lies between  the orbits of Nix and Hydra, two satellites discovered by Hubble in 2005. P4 completes an orbit around Pluto roughly every 31 days.

HuubleSite

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Kepler Watches Stellar Throbbing

by on Aug.02, 2011, under Astronomy, Science

Credit: Science/AAAS

Launched in March 2009, NASA’s Kepler observatory has become synonymous with the search for        extra-solar planets. But that’s not all it’s been doing up in space. The spacecraft has also been recording the gentle pulsations of stars—the small variations in their brightness caused by sound waves throbbing outward from the stellar core to the surface (seen in the yellow star in illustration). In the latest issue of Science, researchers report measuring these pulsations for some 500 sun-like stars, which is        enabling statistical studies of stellar characteristics like mass, radius and age and test models of stellar evolution. In another paper in the same issue, a different research team reports using Kepler data to detect a  system of three stars, which includes a red giant star and two red dwarfs. Although astronomers thought that the red giant would show sun-like oscillations caused by waves from within, they found that the star’s pulsations        were being driven by the waxing and waning of gravity from the orbital motion of the two red dwarfs. Researchers hope to use these observations to gain new insights into the formation of stellar systems, as well as the evolution of stars.

ScienceShots

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First Stars Were Spinning Tops

by on Aug.01, 2011, under Astronomy, Science, Website Related

The first stars born in the universe are believed to have been massive objects, up to hundreds of times bigger than the sun. They were also spinning tops or “spinstars,” according to a new study, that spent their lives whirling at incredible speeds. If true, astronomers may one day be able to glimpse the final days of these early suns.

Twirling wildly. A simulation of a fast-spinning early star. Credit: Adapted from A. Stacy et al., MNRAS, 413 (2011)

Astronomers have yet to catch a glimpse of the earliest stars, which formed some 300 million years after the Big Bang and burned out by the time the universe was 1 billion years old. Made entirely of hydrogen and helium, these stars produced heavier elements in the process of consuming their fuel and ultimately died in explosions that spewed out the newly forged elements into interstellar space. Those elements were incorporated into later generations of stars. By measuring the relative proportions of heavy elements in second- and third-generation stars, many of which have survived to this day, astronomers can make inferences about their now-extinct ancestors.

That’s exactly what a team led by Cristina Chiappini of the Leibniz Institute for Astrophysics in Potsdam, Germany, set out to do by analyzing the ratio of different elements in eight stars from NGC 6522, one of the oldest globular clusters in the Milky Way. The cluster is more than 12 billion years old, which means the stars that the researchers looked at formed only a few hundred million years after the death of first-generation stars. Studying the spectra of the stars, the researchers found unexpectedly high abundances of the heavy elements strontium (Sr) and yttrium (Y). Based on the other characteristics of the stars, it was evident that these two elements had not been made within the stars themselves but were likely present in the interstellar clouds from which the stars originated.

The researchers knew from theory that rare elements such as Sr and Y are forged at higher rates in rotating stars as a result of mixing between outer and inner layers of gas within the star. The nuclear reactions that result from this gas mixing produce a large supply of neutrons that are captured by the nuclei of heavy elements such as iron to make Sr and Y. Chiappini and her colleagues found that the best way to explain the pattern of abundances they had observed was to apply a stellar model involving a spinning velocity of 500 kilometers per second at the surface. In other words, the ancestral stars that spawned the eight stars observed in the study were likely to have been spinning at that velocity, the authors report online today in Nature. That’s 250 times as fast as the sun.

If the first stars were indeed rapid spinners, they are likely to have ended their lives with a huge Gamma Ray Burst (GRB), producing an enormous flash of high-energy radiation. That augurs well for astronomers hoping to watch the first stars in the act of dying. “I think we have little hope of detecting individual first stars directly in the distant universe, but GRBs can be seen much further away than individual stars,” says Jason Tumlinson, an astronomer at Space Telescope Science Institute in Baltimore, Maryland. “A higher frequency of bursts increases the chances of seeing the first generations directly,” he says.

Volker Bromm, a theoretical astrophysicist at the University of Texas, Austin, says rapid rotation “could also lead to a special class of energetic supernova explosions called hypernovae, with unusual chemical abundance patterns.” And, he says, high rates of spinning would induce deep mixing of currents inside the star, causing the star to evolve into a chemically homogeneous object. Future missions such as the Joint Astrophysics Nascent Universe Satellite—a small explorer mission being considered by NASA—could give astronomers their first look at gamma-ray bursts produced by these first-generation stellar objects.

Science Magazine: by Yudhijit Bhattacharjee

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