Posted on by Fraser Cain

Just How Earthlike is this New Planet?

Artist illustration of the rocky planet around the M dwarf Gliese 876. Image credit: NSF. Click to enlarge.
In the land rush known as extrasolar planet hunting, the most prized real estate is advertised as “Earth-like.” On Monday, June 13, scientists raced to plant their flag on a burning hunk of rock orbiting a red star.

This newly discovered planet is about seven times the mass of Earth, and therefore the smallest extrasolar planet found to orbit a main sequence, or “dwarf” star (stars, like our sun, that burn hydrogen).

There are even smaller planets known to exist beyond our solar system, but they have the misfortune to encircle pulsars, those rapidly spinning husks of dying stars. Such planets aren’t thought to be remotely habitable, due to the intense radiation emitted by pulsars.

Planets that are ten Earth masses or less are thought to be rocky, while more massive planets are probably gaseous, since their stronger gravity means they collect and retain more gas during planetary formation. 155 extrasolar planets have been found so far, but most of them have masses that are more comparable to gaseous Jupiter than rocky Earth (Jupiter is 318 times the mass of Earth).

Although this new planet is advertised as Earth-like because of its relatively low mass, earthlings wouldn’t want to rent a house there any time soon. For one thing, the house would melt. The surface temperatures estimated for this planet – 200 to 400 degrees Celsius (400 to 750 degrees Fahrenheit) – are due to the planet’s kissing-close distance from its star.

The planet resides a mere 0.021 AU from the star Gliese 876 (1 AU is the distance between the Earth and the sun), and completes an orbit in less then two Earth days. The closest planet to the sun in our own solar system – blazing hot Mercury – is nearly 20 times further away, orbiting at about 0.4 AU.

“Because the planet is in a two-day orbit, it is heated to oven-like temperatures, so we do not expect life,” says science team member Paul Butler of the Carnegie Institution of Washington.

In our solar system, the habitable zone – the temperate region where water could exist as a liquid on a planet’s surface – is roughly 0.95 to 1.37 AU, or between the orbits of Venus and Mars. The star Gliese 876 is about 600 times less luminous than our sun, so the proposed habitable zone is much closer in, roughly between 0.06 and 0.22 AU.

At 0.021 AU, the new planet is too close to the star to be in the habitable zone, and it also is subjected to greater amounts of high energy radiation like ultraviolet light and X-rays. While red dwarfs like Gliese 876 emit lower levels of UV than stars like our sun, they do emit violent X-ray flares.

Another complication from such a close orbit is that the planet may be tidally locked, with the same side of the planet always facing the star. Unless there is a substantial atmosphere to distribute heat, one side of the planet will be overcooked while the other will remain cold.

Gliese 876 is thought to be about 11 billion years old, making it more than twice as old as our sun. But in a way, Gliese is a teenager to our sun’s middle-aged adult. G-class stars like our sun live about 10 billion years, while M-class red dwarfs are thought to live for 100 billion years (older than the age of the universe!).

Science team member Geoff Marcy of the University of California, Berkeley, says that M stars take a long time to cool off and shrink down to their main sequence size and luminosity. He says that if the planet migrated inwards to its present day close orbit, it probably made this move during the first few million years, and then was subjected to much more radiation than at present for hundreds of millions of years.

Gliese 876 is thought to be metal-poor (to an astronomer, any element heavier than hydrogen and helium is classified as a “metal”). The formation of planets may be related to the metallicity of the star, since both the star and the planets form from the same original material. So a rocky planet like the Earth, made out of elements such as silicates and iron, is expected to orbit a star that is metal-rich.

Despite being metal-poor, Gliese 876 is a multiple planet system. Two gas giant planets are known to orbit Gliese 876: the outermost planet is nearly twice the mass of Jupiter, and orbits at 0.21 AU; the middle planet is about half the mass of Jupiter, orbiting at 0.13 AU.

“The whole planetary system is sort of a miniature of our solar system,” says Marcy. “The star is small, the orbits are small, and in closer is the smallest of them, just as the architecture is in our own solar system, with the smallest planets orbiting inward of the giants.”

We have a lot more elbow room in our solar system. Mercury is further away from the sun than the distances of all these planets combined. The planets in the Gliese 876 system are so close together, they gravitationally interact with each other. This sort of gravitational tug of war was how the scientists were able to detect the planets in the first place.

Over the course of an orbit, planets will gravitationally pull on their star from different sides. Scientists measure the resulting shift in star light to determine the existence of orbiting planets.

To learn more about Gliese 876’s smallest planet, scientists would need to use another planet-hunting technique called transit photometry. This method looks at how a star’s light seems to dip when a planet passes in front of the star from our field of view. The eclipse of the orbiting planet allows astronomers to determine that planet’s mass and radius. Pinning down those numbers indicates the planet’s density, which then suggests what the planet is made of, and whether the planet is rocky or gaseous.

Transit photometry can’t be used to tell us anything about planets orbiting Gliese 876, however, because the system is inclined 50 degrees from our point of view. This angle means the planets won’t block any of the starlight that reaches Earth.

Red dwarfs are the most common type of star in our galaxy, comprising about 70 percent of all stars. Yet out of the 150 red dwarfs they have studied over the years, Marcy and Butler only have found planets orbiting two of them. Because most of the planets found so far are gas giants, this could mean that red dwarfs are less apt to harbor those kinds of worlds.

Marcy says they will continue to monitor Gliese 876 for any hints of a fourth or fifth planet. “This will definitely be one of our favorite stars from now on.”

A Race to the Finish Line
The research paper describing this discovery has been submitted to the Astrophysical Journal. The scientists say they received a favorable preliminary referee’s report, and they expect their paper will be accepted and then published in a few months. During Monday’s press conference, the scientists were asked why they decided to publicize their finding now, before the paper had been accepted for publication. Was it done to beat out other planet hunters who might be hot on their heels?

Marcy replied that they wanted to prevent news of their discovery from leaking out. “We knew about it three years ago, we’ve been following it quietly, carefully, guarding the secret while we double and triple checked. Then about a month ago I talked with Michael Turner here, people at NSF (National Science Foundation), and jointly we decided that this discovery was so extraordinary, maybe what you would call a milestone in planetary science, that it was difficult to imagine keeping the lid on this for very much longer. So we decided that rather than have it leak out to the news media, and be dribbled around, with one newspaper learning about it early and so on, that it would be better to quickly announce this.”

Marcy then launched into a defense for why he believed their finding is correct, and he was quickly backed by his fellow team members. However, the accuracy of their finding had not been questioned. Perhaps their early announcement, combined with the need for secrecy beforehand, is evidence of the intense competition that has marked planet hunting since the beginning.

The first extrasolar planet discovery was announced October 5, 1995 by Michel Mayor and Didier Queloz of the Geneva Observatory, and Marcy and Butler confirmed the observations the following week. A recent example of the competition to grab other extrasolar planet “firsts” occurred last summer, when on August 25, 2004, Mayor, Nuno Santos, and colleagues announced the discovery of the first extrasolar Neptune-mass planet — at the time the smallest extrasolar planet known to orbit a sun-like star. This announcement came less than a week before two other Neptune-mass planet discoveries were announced by Marcy and Butler.

Mayor and his colleagues also have studied Gliese 876. At an astronomy conference in June 1998, Mayor and Marcy each independently announced the detection of the more massive gas giant orbiting this star. Marcy and Butler were first to follow up on this finding, announcing the discovery of the star’s second gas giant planet in 2001.

The Kepler mission, due to launch in June 2008, will search for terrestrial planets orbiting distant stars. The mission defines an Earth-size planet as being between 0.5 and 2.0 Earth masses, or between 0.8 and 1.3 Earth’s diameter. Planets between 2 and 10 Earth masses, such as the planet announced on Monday, are defined as Large Terrestrial planets.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

Staring into a Cosmic Jet

Herbig-Haro 211 consists of two jets of material, visible at lower right. Image credit: A.A. Muench-Nasrallah, CfA. Click to enlarge.
Astronomers find jets everywhere when they look into space. Small jets spout from newborn stars, while huge jets blast out of the centers of galaxies. Yet despite their commonness, the processes that drive them remain shrouded in mystery. Even relatively nearby stellar jets hide their origins behind almost impenetrable clouds of dust. All stars, including our sun, pass through a jet phase during their “childhood,” so astronomers are eager to understand how jets form and how they may influence star and planet formation.

At this week’s meeting on submillimeter astronomy in Cambridge, Mass., astronomers described the latest results from an international collaboration using the Submillimeter Array (SMA) atop Mauna Kea, Hawaii. The SMA has begun to peer through the dust and home in on the sources of nearby stellar jets.

“Using the SMA, we can stare into the throat of the jet,” said SMA project scientist Paul Ho of the Harvard-Smithsonian Center for Astrophysics (CfA). “We’re getting close to seeing its launching point.”

Astronomer Hsien Shang of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) and her colleagues have created a model of jet formation that calculates temperatures, densities and brightnesses within stellar jets. SMA observations of a young star system prosaically named Herbig-Haro (HH) 211 have confirmed the validity of the model.

“Our model predicts what we will see about 100 astronomical units from the star,” Shang said. (One astronomical unit is the average Earth-Sun distance of 93 million miles.) “With the SMA, we can begin to look at the HH 211 system at the scale of the model and test those predictions. So far, everything checks out.”

HH 211 is located about 1,000 light-years away in the constellation Perseus. Astronomers estimate that the small protostar hidden within HH 211 is less than 1,000 years old-a mere baby by astronomical standards, so young that it is still growing by accumulating matter from a surrounding disk of gas and dust. The protostar eventually will become a low-mass star similar to the sun.

Although most of the matter in the disk will flow onto the star, some must be ejected outward to carry away excess angular momentum. Complex physical processes funnel that ejected matter into dual jets that shoot outward in opposite directions.

“Jets form very close to a protostar, within about 5 million miles of its surface according to the model we applied” said researcher Naomi Hirano (ASIAA). “The SMA can help test the jet model on the youngest protostars using molecular tracers from within that innermost region.”

SMA’s successor, the planned ALMA project, should finally reveal the nature of the engine powering these jets by peering into the core where they form.

“The SMA has brought us tantalizingly close to our goal-the answer to the question of how jets form,” said Ho. “ALMA will take us those final few steps.”

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: Harvard CfA News Release

Posted on by Fraser Cain

Neutrino Evidence Confirms Big Bang Predictions

A cosmic view of neutrino ripples. Image credit: Oxford. Click to enlarge.
Astrophysicists from the Universities of Oxford and Rome have for the first time found evidence of ripples in the Universe?s primordial sea of neutrinos, confirming the predictions of both Big Bang theory and the Standard Model of particle physics.

Neutrinos are elementary particles with no charge and very little mass, which are extremely difficult to study due to their very weak interaction with matter. Yet pinning down the physical properties of neutrinos is of paramount importance to scientists attempting to understand the fundamental building blocks of Nature. According to the standard Big Bang model, neutrinos permeate the Universe at a density of about 150 per cubic centimetre. The Earth is therefore immersed in an ocean of neutrinos, without us ever noticing.

Although it is impossible to measure this ?Cosmic Neutrino Background? directly with present-day technology, physicists predict that ripples or waves in it have an impact on the growth of structures in the Universe.

In research to be published in the journal Physical Review Letters, Dr. Roberto Trotta, Lockyer Fellow of the Royal Astronomical Society at Oxford?s Department of Physics, and Dr. Alessandro Melchiorri of La Sapienza University in Rome were able to demonstrate for the first time the existence of ripples of primordial origin in the Cosmic Neutrino Background.

The discovery, made by combining data produced by the NASA WMAP (Wilkinson Microwave Anisotropy Probe) satellite and the Sloan Digital Sky Survey, confirms the predictions of both the Big Bang theory and the Standard Model of particle physics. The research has important implications for the study of neutrinos, showing that theories of the infinitely large (cosmology) and the infinitely small (particle physics) are in agreement.

Dr. Trotta said: ?This research provides important new evidence in favour of the current cosmological model, unifying it with fundamental physics theories. Cosmology is becoming a more and more powerful laboratory where physics not easily accessible on Earth can be tested and verified. The high quality of recent cosmological data allows us to investigate neutrinos in the cosmological framework, obtaining measurements which are competitive with ? if not superior to ? particle accelerator findings.?

Original Source: Oxford News Release

Posted on by Fraser Cain

Audio: Get Ready for Deep Impact

Deep Impact’s impactor module on a collision course with Comet Tempel 1. Image credit: NASA/JPL. Click to enlarge.
Listen to the interview: Get Ready for Deep Impact (6.1 MB)

Or subscribe to the Podcast: universetoday.com/audio.xml

Fraser: Can you give me a preview for what we’re going to be seeing on July 4th?

Dr. Lucy McFadden: I wish I knew exactly what was going to happen on July 4th, but this is an experiment. I can tell you what we think we might see, but chances are it may be significantly different.

So, we have a spacecraft on its way to Comet Tempel 1, which is a short-period comet that orbits – comes into the inner solar system – about once every 5.5 years. It is about the size of Washington DC. It can be fit into the area of Washington DC, but it’s a little bit elongated. It’s about 14 km by 4 km by 4 km, and as our spacecraft is heading toward it, we have planned to actually separate the spacecraft into two parts. Let me set the stage here, this comet is in orbit around the Sun. It’s coming to its closest point of the Sun, called its perihelion, and thus be moving at its fastest speed through the solar system in early July. Our spacecraft is also in orbit around the Sun, and it’s heading to intercept the orbit of the comet. 24 hours before we plan to impact this comet, we’re going to separate the two spacecraft, the impactor and the flyby. The impactor will continue on its collision course to the comet, and the flyby – or mother ship – will slow down a little bit and change its direction ever so slightly so that it will be able to watch as the impactor hits the comet. When it hits the comet, when we have this cosmic collision in space, what’s going to happen is the energy of the impact is going to propagate into the comet itself, in the form of a shock wave. This shock wave will plough into the comet; how deep, we don’t know. But at some point, the force of the material in the comet itself will push back on the advancing energy shock wave and push material out of the comet. We will have formed a crater with ejected material coming out of the hole that we created.

Now, you may ask, why are we doing this? We’re doing this to take a look – to take advantage of the opportunity of this comet being so close to us – to take a look at the inside of the comet; to see what the inside is made of, and see what structure is there.

To elaborate more, I think I need to give you some perspective on what comets are, and what they are in the solar system. I like to say they’re the oldest and coldest part of the solar system. They formed at the edges of the solar system, hundreds of thousands of times the distance that the Earth is from the Sun. So, everything where comets formed is cold. They also formed 4.5 billion years ago, when the solar system was forming. They have never been incorporated into a planet. So they’re both old and cold as well. We’re taking advantage of the comets coming closer to the Earth to use it as a laboratory and as a probe to distant edges of the solar system in both space and time.

Fraser: Now, Deep Impact only launched a couple of months ago, so did we get really lucky with Tempel 1 being at the wrong place at the right time?

Dr. McFadden: Yeah, well, from my perspective it was at the right place at the right time.

Fraser: I was more looking from the perspective of the comet.

Dr. McFadden: Let me say two things here. First of all, the comet isn’t going to be harmed. Let’s get some perspective here in terms of the mass of the spacecraft versus the mass of the comet. Or the energy of the spacecraft versus the energy of the comet in motion. It’s equivalent to a gnat, or a small mosquito being run into by a 767 aircraft. So, we’re not going to hit the comet. But, needless to say, I’ll let you take the perspective of the comet if you want. But yes, it was in the right place, or the wrong place, at this time. NASA said, when it issued its announcement of opportunity for space exploration missions, they said that this announcement covers money available within a certain time frame, and the time frame was between 2000 and 2006. And so, we went looking for comets that were available during the time NASA would give us money, and then when we found Comet Tempel 1 close to perihelion, when it’s moving fastest, that also pleased us because the faster the comet’s moving, the more energy involved in the transfer to create the crater. So, it’s good from that point of view. And then there’s a third, but secondary reason why Comet Tempel 1 is good; it’s not as active as some comets might be. There’s not as much dust and jet activity associated with Comet Tempel 1, which might be confusing or make it hard for us to actually observe the formation of the crater when we hit it. So, Comet Tempel 1 fits.

Fraser: How are we going to be observing it from here on Earth and from space?

Dr. McFadden: We have the spacecraft observing it from space – our Deep Impact spacecraft. We have the Rosetta spacecraft, which is heading to another comet, will also observe it from space. We have NASA’s three Great Observatories: Chandra, Hubble and Spitzer will be observing it. Three different wavelengths; Chandra’s an X-ray telescope, and Hubble’s an optical and near-infrared imaging telescope. We’ll be observing some spectroscopy with Hubble too. And then Spitzer’s an infrared telescope. So, we’ll be using those. As well as all the major observatories around the world will be observing the comet, before, during and after impact. So we’re having a worldwide observing campaign.

Fraser: And how will the pictures from Deep Impact compare to the pictures we saw from Stardust?

Dr. McFadden: It’s interesting, I’m using the images from Stardust to practice interpreting the images we get from Deep Impact. We will get a closer look at Comet Tempel 1 than the Stardust spacecraft did; we will be flying closer – we’ll be flying 500 km from Comet Tempel 1, whereas the Stardust spacecraft was 1,100 or 1,300 km distant.

Fraser: I remember that Stardust got hit quite a bit by debris, how will Deep Impact do if it’s going to be closer to the comet?

Dr. McFadden: You have to remember that the main objective of Stardust was to collect dust, so, they wanted to get hit. So they flew into the region with the largest dust density. What we do when we fly through that same region is we turn the spacecraft away into shield mode to protect the telescope during the time when we should be getting the greatest number of hits from dust and debris. And we actually fly at an angle. Most of the debris exists in the plane of the orbit, in the direction of its motion, and so the spacecraft will fly past it at an angle; so there’ll be a short, 20 minute period when we will not be observing to protect the cameras.

Fraser: Once Deep Impact completes its flyby, will you have any additional scientific targets you’d like to be able to use the spacecraft for, once it gets out of visual range of Tempel 1?

Dr. McFadden: There are currently no specific plans for observing in a follow-on mission; that has to be approved by NASA. We have done some research and know that there are another comet or two that we could observe, but we haven’t gotten approval for that yet.

Fraser: So, in your wildest dreams, what will turn up on July 4th?

Dr. McFadden: Well, my wildest dream is that the impactor will go into the comet and come out the other side, but that’s not very likely.

Fraser: Okay then, maybe a less wild dream.

Dr. McFadden: Okay, less wild, in order of probability is that the comet will have the consistency of a brick, for example, and the impactor will hit it and not do much damage to the surface, or not really create much of an impact because the comet is the consistency of a brick. But that’s not very likely either. On the other extreme, what if the comet is like Corn Flakes? If it’s like Corn Flakes, we should get a spectacular display of ejecta. We call it an ejecta curtain during the formation of the crater, and I’m hoping that that’s what we’ll see, because that would be very dramatic. And hopefully we could watch as we’re taking fast pictures with very short exposures repeatedly. We’ll be clicking as we go by. If we have a big ejecta curtain, we should be able to see the ejecta form, or traveling along in space, and that will allow us to determine the most information about the internal structure of the comet itself. So that’s what I’m hoping will happen.

Posted on by Fraser Cain

Planetary Systems Can Form in Hellish Surroundings

Artist interpretation of protoplanetary systems forming inside a nebula. Image credit: CfA. Click to enlarge.
Meeting this week in Cambridge, Mass., astronomers using the Submillimeter Array (SMA) on Mauna Kea, Hawaii, confirmed, for the first time, that many of the objects termed “proplyds” found in the Orion Nebula do have sufficient material to form new planetary systems like our own.

“The SMA is the only telescope that can measure the dust within the Orion proplyds, and thereby assess their true potential for forming planets. This is critical in our understanding of how solar systems form in hostile regions of space,” said Jonathan Williams of the University of Hawaii Institute for Astronomy, lead author on a paper submitted to The Astrophysical Journal.

Surviving in the chaotic regions within the Orion Nebula where stellar winds can reach a staggering two million miles per hour and temperatures exceed a searing 18,000 degrees Fahrenheit, the question remained – would enough material endure to form a new solar system or would it be eroded away into space like wind and sand eroding away desert cliffs? It now appears that these protoplanetary disks are quite tenacious, bringing new grounds for optimism in the search for planetary systems.

Imaged by the Hubble Space Telescope back in the early 1990s as misshapen silhouettes against the nebular background, the most spectacular proplyds appear bright. Their surrounding ionized cocoons glow due to their close proximity to a nearby hot star formation called the Trapezium. The Trapezium is a star cluster consisting of more than 1,000 young, hot stars that are only 1 million years old. They condensed out of the original cold, dark cloud of gas that now glows from their ionizing light. They are crowded into a space about 4 light-years in diameter, the same as the distance between the Sun and Proxima Centauri, the next closest star in space.

Blasted by the solar winds of the Trapezium, the proplyds are the next generation of smaller stars to arise in Orion, this time with visible discs that may be forming planets. It has remained unclear, however, whether they contained enough material to form stable planetary systems. Using the SMA, astronomers now have been able to probe deep inside these disks to measure their mass and to unravel the formation process presented by these potential infant solar systems.

“While the Hubble pictures were spectacular, they revealed only disk-like shapes that did not tell us the amount of material present,” said David Wilner, of the Harvard-Smithsonian Center for Astrophysics (CfA). Since some of the discs appear to be comparable in size and mass to our own solar system, this strengthens the connection between the Orion proplyds and our origins.

Since most Sun-like stars in the Galaxy eventually form in environments like the Orion Nebula, the SMA results suggest that the formation of solar systems like our own is common and a continuing event in the Galaxy.

“The same cycle of birth, life and death we experience here on Earth is repeated in the stars overhead. Now, the SMA provides us with a front-row seat in unraveling the wonder of these cosmic events,” reflected Wilner.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: CfA News Release

Posted on by Fraser Cain

Podcast: Get Ready for Deep Impact

July 4th is Independence Day In the United States, and Americans typically enjoy their holiday with a few fireworks. But up in space, 133 million kilometres away, there’s going to be an even more spectacular show… Deep Impact. On July 4th, a washing machine-sized spacecraft is going to smash into Comet Tempel 1, carve out a crater, and eject tonnes of ice and rock into space. The flyby spacecraft will watch the collision from a safe distance, and send us the most spectacular pictures ever taken of a comet – and its fresh bruise. Dr. Lucy McFadden is on the science team for Deep Impact, and speaks to me from the University of Maryland.
Continue reading “Podcast: Get Ready for Deep Impact”

Posted on by Fraser Cain

Large Rocky Planet Discovered

Artist illustration of the rocky planet around the M dwarf Gliese 876. Image credit: NSF. Click to enlarge.
Taking a major step forward in the search for Earth-like planets beyond our own solar system, a team of astronomers has announced the discovery of the smallest extrasolar planet yet detected. About seven-and-a-half times as massive as Earth, with about twice the radius, it may be the first rocky planet ever found orbiting a normal star not much different from our Sun.

All of the nearly 150 other extrasolar planets discovered to date around normal stars have been larger than Uranus, an ice-giant about 15 times the mass of the Earth.

“We keep pushing the limits of what we can detect, and we’re getting closer and closer to finding Earths,” said team member Steven Vogt, a professor of astronomy and astrophysics at the University of California, Santa Cruz.

?Today’s results are an important step toward answering one of the most profound questions that mankind can ask: Are we alone in the universe?? said Michael Turner, head of the Mathematical and Physical Sciences Directorate at the National Science Foundation, which provided partial funding for the research.

The newly-discovered ?super-Earth? orbits the star Gliese 876, located just 15 light years away in the direction of the constellation Aquarius. This star also possesses two larger, Jupiter-size planets. The new planet whips around the star in a mere two days, and is so close to the star’s surface that its temperature probably tops 400 to 750 degrees Fahrenheit (200 to 400 degrees Celsius)?oven-like temperatures far too hot for life as we know it.

Nevertheless, the ability to detect the tiny wobble that the planet induces in the star gives astronomers confidence that they will be able to detect even smaller rocky planets in orbits more hospitable to life.

“This is the smallest extrasolar planet yet detected and the first of a new class of rocky terrestrial planets,” said team member Paul Butler of the Carnegie Institution of Washington. “It’s like Earth’s bigger cousin.”

The team measures a minimum mass for the planet of 5.9 Earth masses, orbiting Gliese 876 with a period of 1.94 days at a distance of 0.021 astronomical units (AU), or 2 million miles.

Though the team has no direct proof that the planet is rocky, its low mass precludes it from retaining gas like Jupiter. Three other purported rocky planets have been reported, but they orbit a pulsar, the flashing corpse of an exploded star.

“This planet answers an ancient question,” said team leader Geoffrey Marcy, professor of astronomy at the University of California, Berkeley. “Over 2,000 years ago, the Greek philosophers Aristotle and Epicurus argued about whether there were other Earth-like planets. Now, for the first time, we have evidence for a rocky planet around a normal star.”

Marcy, Butler, theoretical astronomer Jack Lissauer of NASA/Ames Research Center, and post-doctoral researcher Eugenio J. Rivera of the University of California Observatories/Lick Observatory at UC Santa Cruz presented their findings today (Monday, June 13) during a press conference at NSF in Arlington, Va.

Their research, conducted at the Keck Observatory in Hawaii, was supported by NSF, the National Aeronautics and Space Administration, the University of California and the Carnegie Institution of Washington.

A paper detailing the results has been submitted to The Astrophysical Journal. Coauthors on the paper are Steven Vogt and Gregory Laughlin of the Lick Observatory at the University of California, Santa Cruz; Debra Fischer of San Francisco State University; and Timothy M. Brown of NSF?s National Center for Atmospheric Research in Boulder, Colorado.

Gliese 876 (or GJ 876) is a small, red star known as an M dwarf ? the most common type of star in the galaxy. It is located in the Aquarius constellation, and, at about one-third the mass of the sun, is the smallest star around which planets have been discovered. Butler and Marcy detected the first planet there in 1998; it proved to be a gas giant about twice the mass of Jupiter. Then, in 2001, they reported a second planet, another gas giant about half the mass of Jupiter. The two are in resonant orbits, the outer planet taking 60 days to orbit the star, twice the period of the inner giant planet.

Lissauer and Rivera have been analyzing Keck data on the Gliese 876 system in order to model the unusual motions of the two known planets, and three years ago got an inkling that there might be a smaller, third planet orbiting the star. In fact, if they hadn’t taken account of the resonant interaction between the two known planets, they never would have seen the third planet.

“We had a model for the two planets interacting with one another, but when we looked at the difference between the two-planet model and the actual data, we found a signature that could be interpreted as a third planet,” Lissauer said.

A three-planet model consistently gave a better fit to the data, added Rivera. “But because the signal from this third planet was not very strong, we were very cautious about announcing a new planet until we had more data,” he said.

Recent improvements to the Keck Telescope’s high-resolution spectrometer (HIRES) provided crucial new data. Vogt, who designed and built HIRES, worked with the technical staff in the UC Observatories/Lick Observatory Laboratories at UC Santa Cruz to upgrade the spectrometer’s CCD (charge coupled device) detectors last August.

“It is the higher precision data from the upgraded HIRES that gives us confidence in this result,” Butler said.

The team now has convincing data for the planet orbiting very close to the star, at a distance of about 10 stellar radii. That’s less than one-tenth the size of Mercury’s orbit in our solar system.

“In a two-day orbit , it’s about 200 degrees Celsius too hot for liquid water,” Butler said. “That tends to lead us to the conclusion that the most probable composition of this thing is like the inner planets of this solar system ? a nickel-iron rock, a rocky planet, a terrestrial planet.”

“The planet’s mass could easily hold onto an atmosphere,” noted Laughlin, an assistant professor of astronomy at UC Santa Cruz. “It would still be considered a rocky planet, probably with an iron core and a silicon mantle. It could even have a dense steamy water layer. I think what we are seeing here is something that’s intermediate between a true terrestrial planet like the Earth and a hot version of the ice giants Uranus and Neptune.”

Combined with improved computer software, the new CCD (charge coupled device) detectors designed by this team for Keck’s HIRES spectrometer can now measure the Doppler velocity of a star to within one meter per second ? human walking speed ? instead of the previous precision of three meters per second. This improved sensitivity will allow the planet-hunting team to detect the gravitational effect of an Earth-like planet within the habitable zone of M dwarf stars like Gliese 876.

“We are pushing a whole new regime at Keck to achieve one meter per second precision, triple our old precision, that should also allow us to see Earth-mass planets around sun-like stars within the next few years,” Butler said.

“Our UC Santa Cruz and Lick Observatory team has done an enormous amount of optical and technical and detector work to make the Keck telescope a rocky planet hunter, the best one in the world,” Marcy added.

Lissauer also is excited by another feat reported in the paper submitted to the journal. For the first time, he, Rivera and Laughlin have determined the line-of-sight inclination of the orbit of the stellar system solely from the observed Doppler wobble of the star. Using dynamical models of how the two Jupiter-size planets interact, they were able to calculate the masses of the two giant planets from the observed shapes and precession rates of their oval orbits. Precession is the slow turning of the long axis of a planet’s elliptical orbit.

They showed that the orbital plane is tilted 40 degrees to our line of sight. This allowed the team to estimate the most likely mass of the third planet as seven and a half Earth masses.

“There’s more dynamical modeling involved in this study than any previous study, much more,” Lissauer said.

The team plans to continue to observe the star Gliese 876, but is eager to find other terrestrial planets among the 150 or more M dwarf planets they observe regularly with Keck.

“So far we find almost no Jupiter-mass planets among the M dwarf stars we’ve been observing, which suggests that, instead, there is going to be a large population of smaller mass planets,” Butler noted.

Original Source: Carnegie Institute News Release

Posted on by Fraser Cain

What’s Up This Week – June 13 – June 19, 2005

Comet Tempel 1. Deep Impact Gallery. Click to enlarge.
Monday, June 13 – Today in 1983, Pioneer 10 made space history as it became the first manmade object to leave our solar system.

Have you been watching your equinox marker? Today marks an important date for the Sun’s journey across the sky. In ancient times, and even in our modern ones, sundials are used to measure time. The position of the Sun today will allow a well placed sundial will match a standard clock. Although a sundial is fairly accurate, we apply a correction known as the Equation of Time and only four times a year does it reach zero.

Comet 9/P Tempel 1 is sailing through Virgo and is now nearing magnitude 9 – putting it within reach of most telescopes. If you haven’t found the object of Deep Impact yet, you’ll be happy to know that Heaven’s Above is now offering highly accurate locator charts. In a smaller scope, it is dim, small, and has a slight concentration toward the core. For the very large scope, note the intense stellar nucleus and wide fan of the tail. I have been observing this comet now for weeks and it looks very much like the picture in a big scope. Now, go… Find it!

Tuesday, June 14 – For those located near 40 degrees north, today will be the earliest sunrise of the year. Tonight the Moon reaches first quarter and this would be a wonderful opportunity to look for the “Alpine Valley” in the lunar northern hemisphere. Valles Alpes will appear as a long, dark scar running through the foothills west of crater Aristotle.

If you would like more of a challenge, then know that Pluto is now at opposition and viewable in Serpens Caudia west of Xi Serpentis. At close to magnitude 14, the tiny planet will require at least a moderate-sized telescope to view, and a very accurate locator chart. In order to distinguish Pluto from background stars, I suggest sketching the field and observing over a number of nights to see which “star” moves.

Wednesday, June 15 – For most observers, Jupiter and the Moon will have wonderfully close encounter as they follow each other across the sky. Tonight on the lunar surface, look just south of central for the descending three rings of Ptolmaeus, Alphonsus and Arzachel. To the west of Arzachel near the terminator, you will see the smooth floor of Mare Nubium. Look for a very curious feature called the “Straight Wall”. It will appear like a very thin, black line that extends from crater Thebit.

While out, take the time to check out Alpha Herculis -Ras Algethi. You will find it not only to be an interesting variable, but a colorful double as well. The primary star is one of the largest known red giants and at about 430 light years away, it is also one of the coolest. Its 5.4 magnitude greenish companion star is easily separated in even small scopes – but even it is a binary! This entire star system is enclosed in an expanding gaseous shell that originates from the evolving red giant. Enjoy it tonight.

Thursday, June 16 – North Australia and New Zealand are featured on this universal date as the Moon occults Jupiter. Be sure to check out this IOTA webpage for precise times in your area. You won’t want to miss it…

The June Lyrids meteor shower will also peak in the early morning hours and will be best after the the Moon has set. With the radiant near bright Vega. you may see up to 15 faint blue meteors per hour from this branch of the May Lyrid meteor stream.

Valentina Tereshkova became the first woman in space, 32 years ago today. She flew aboard the Russian spacecraft, Vostok 6, and her solo flight is still unique.

Although the Moon will fade the view, telescope users might be able to just make out Comet 2004 Q2 Machholz as it passes about a degree east of Alpha Canum. Although we have explored Cor Caroli before, take the time again to check out the soft orange and lavender colors of this splendid double star.

Friday, June 17 – Ah, to waltz around the “Bay of Rainbows” with you! Tonight the lunar surface will offer the telescopic opportunity to view one of perhaps the most romantic of areas – Sinus Iridium. Look to the lunar north where you will discover the smooth bay partially encircled by the Juras Mountains. Promentoriums Heraclides and LaPlace stand like distant lighthouses at either tip. If seeing conditions are good, you will note many graceful rilles, like frozen waves, crossing its floor.

If you don’t own a telescope, Sinus Iridium still shows quite well in binoculars. For unaided viewers? See if you can spot cool, blue Spica nearby.

Saturday, June 18 – Today in 1983, Sally Ride became the first American woman to go into orbit. Sally’s ride? The Space Shuttle!

But you won’t need the Space Shuttle to take you into orbit tonight as the lunar surface becomes a binocular hunter’s paradise. Starting in the lunar north, look for the blank, loveless eye of Plato and the dramatically brightening rays of Tycho to the south. Look for ancient Copernicus just slightly west of the mid-section and the brilliant points of light near the terminator that are Keplar to the north and Artistarchus to its south. Eroded crater Gassendi on the shore of Mare Humorum to the south will round out our lunar tour.

For North American observers, be sure to check out Saturn before it sets. Like a temporary “moon”, 7th magnitude star SAO79782 will be visible to its north.

Sunday, June 19 – If you are up just before dawn this morning, keep an eye on the sky as we pass through another portion of the Ophiuchid meteor stream. The radiant for this pass will be more near Sagittarius and the fall rate varies from 8 to 20, but can sometimes produce unexpectedly more.

No matter what time zone you live in, Jupiter will be a lively place tonight! For some viewers, you will see a very close pairing of Ganymede and Europa – and for others, Io and Europa. For viewers well positioned at 22:19 UT, the “Great Red Spot” will also transit.

If you haven’t been following the intricate dance of the evening planets, then go out just after sunset and look! Venus, Saturn, and Mercury are now within a fist width apart, sitting low in the west-northwest during. Mercury, the lowest of the three, sets about 1 1/2 hours after sunset, so don’t wait too late to observe. The planets will contine to move closer all next week, so mark your calendars for next weekend when they appear only 1.5 degrees apart. You won’t want to miss this!

Keep your eyes on the skies and may all your journeys be at Light Speed! …~Tammy Plotner

Posted on by Mark Mortimer

Book Review: Deep Space NASA Mission Reports

Deep Space – The NASA Mission Reports. Click to enlarge.
With the maturing of space flight in the 1960’s, NASA could set goals loftier than clambering around Earth’s nearest satellite for a few short hours. There existed the ability to travel anywhere in the solar system, take measurements and view the results. Grabbing this opportunity with both hands, NASA launched:

? the Pioneer 10 and 11 crafts on two missions to Jupiter,
? the Voyager 1 and 2 crafts on two missions to Jupiter, Saturn and beyond,
? the Galileo craft on a mission to Jupiter,
? the Cassini-Huygens craft on a mission to Saturn,
? the Deep Space 1 craft on a mission to comet 19P/Borrelly, and
? the Stardust craft on a mission to comet Wild-2.

Nominally each was to expand our knowledge of the solar system and to better understand our relative place within it.

NASA, as typical for all government bureaucracies, dutifully printed up extensive documentation for each mission. From these, the book provides reproductions of press kits, special reports, status reports and fact sheets. The press kits predominate. They describe the craft, the mission, current activities, any extenuating circumstances and expectations just prior to critical moments. Typically, one kit gives a pre-launch summary and others give a summary just before the first encounter of a target. The kits are quite detailed with break downs of the components and functions of each spacecraft. Descriptions of the purpose and equipment for each science experiments clarify the purpose. The trajectory, navigation and communication elements demonstrate some challenges to be overcome. Lists of project managers, principal investigators and contractors ensure posterity to many participants. Thin coverage of the results is an indicator that, though NASA ran the missions and wrote many transcripts, there were others that promulgated the results in their own distinct fashion.

The enclosed DVD shows how NASA has leapt into the new media of video. Audio/video footage from NASA TV and other NASA sources show boosters lofting payloads up and away. During final countdown, often a lengthy time of apparent inactivity, images of trucks and transport aeroplanes delivering components liven up the proceedings. Clean room activities, such as checking solar arrays and mating components, give some insight into preflight activities. Video results of encounters particularly reward viewers. A wonderful segment shows a complete 360 degree coverage of the tumbling asteroid Eros from a very close perspective. Voyager’s visual imagery of the swirling storms on Jupiter transfix the eye and certainly credit the usage of video as a strong communication media.

With the inclusion of all these deep space missions, the editors Godwin and Whitfield provide a marvellous resource for reviewing any deep space mission. Further, by proceeding in a chronological order, the reader can easily grasp how results of an earlier mission influenced the investigations of the following one. From the Pioneer mission, where transit of the asteroid belt came with much misgivings, to Cassini-Huygens dropping a capable probe onto a moon of Saturn, the press kits look the same but the contents just keep getting better.

One thing about having dual missions like Pioneer 10 and 11 or Voyager 1 and 2 is that a lot of similarity exists. The same must be said for their press kits. Though the editors appear to have tried to remove some repetitive verbiage, there are still many tracts, drawings and lists that appear time and again in the book. This is true whether the kits are for different moments of the same mission or of related missions. Also, in keeping with government-eze, just about all the dissertation blandly recites facts and figures. Qualitative descriptors are few and far between. Regarding the DVD, the short 8 page PDF file for Galileo seems an injustice especially considering the 100’s of pages and videos for both Pioneer and Voyager.

One truly rewarding decisions created NASA as a non-military organization. In consequence, they hide little in the quest to learn more about the universe in which we live. The book Deep Space – The NASA Mission Reports as edited by Robert Godwin and Steve Whitfield compiles the very detailed official announcements from NASA for their missions that travelled beyond Mars. In it, facts, figures, data and images corroborate our new awareness and appreciation of our planetary neighbourhood.

Order a copy online from Countdown Creations or Amazon.com.

Review by Mark Mortimer

Posted on by Fraser Cain

Mmmm, Food From Mars

Spirulina Gnocchis, a recipe that could be cooked up from food grown in space. Image credit: ESA. Click to enlarge.
‘Martian bread and green tomato jam’, ‘Spirulina gnocchis’ and ‘Potato and tomato mille-feuilles’ are three delicious recipes that two French companies have created for ESA and future space explorers to Mars and other planets.

The challenge for the chefs was to offer astronauts well-flavoured food, made with only a few ingredients that could be grown on Mars. The result was 11 tasty recipes that could be used on future ESA long-duration space missions. ADF ? Alain Ducasse Formation and GEM are the two French companies that produced the recipes, and their mutual experience in creating new products and ?haute cuisine? have led to excellent results.

The menus were all based on nine main ingredients that ESA envisions could be grown in greenhouses of future colonies on Mars or other planets. The nine must comprise at least 40% of the final diet, while the remaining (up to) 60% could be additional vegetables, herbs, oil, butter, salt, pepper, sugar and other seasoning brought from Earth.

“We are aiming initially at producing 40% locally for astronauts’ food on future long-duration space missions, for example to Mars,” says Christophe Lasseur, ESA’s biological life-support coordinator responsible for recycling and production of air, water and food for long-term space missions.

“Why 40%? By growing enough plants to cover around 40% of what we eat, we also get ‘for free’ the oxygen and water needed to live”, explains Lasseur.

The nine basic ingredients that Lasseur plans to grow on other planets are: rice, onions, tomatoes, soya, potatoes, lettuce, spinach, wheat and spirulina ? all common ingredients except the last. Spirulina is a blue-green algae, a very rich source of nutrition with lots of protein (65% by weight), calcium, carbohydrates, lipids and various vitamins that cover essential nutritional needs for energy in extreme environments.

Today all the food for astronauts in space is brought from Earth, but this will not be possible for longer missions. Although still on the drawing board, ESA has already started research to see what could be grown on other planets – and what a self-supporting eco-system might look like on Mars.

“In addition to being healthy and sufficiently nutritious for survival, good food could potentially provide psychological support for the crew, away from Earth for years,” emphasises Lasseur.

ADF chef Armand Arnal, adds: “The main challenge was to create a wide panel of recipes, distinct and full-flavoured, with only nine basic products.”

“Moreover, we had absolute restrictions on using salt, but were allowed to add a bit of sugar and fat, ingredients normally essential to the elaboration of a dish and to highlight its flavours.”

Original Source: ESA News Release