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  • richardmitnick 4:18 pm on November 14, 2018 Permalink | Reply
    Tags: "Searching for an Exoplanet", , , Barnard's Star, , , ,   

    From ESOblog: “Searching for an Exoplanet” 

    ESO 50 Large

    From ESOblog

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    14 November 2018

    After archival data indicated the possible presence of a planet around nearby Barnard’s Star, a team of scientists undertook an epic campaign to try to confirm its presence. The result, published this week and described in an ESO press release, was the discovery of evidence for the second-closest exoplanet to Earth. In this blog post, lead scientist Ignasi Ribas helps us investigate the discovery further and look at the incredible story behind it.

    Related ESO press release can be found here.
    See https://sciencesprings.wordpress.com/2018/11/14/from-european-southern-observatory-super-earth-orbiting-barnards-star/ for a full accounting of the instrumentation used in this project and also the science team.

    Q. Could you start by telling us what you found and why it’s exciting?

    A. We have combined 20 years of observations to discover a candidate planet around Barnard’s Star, one of the nearest stars to the Sun. Barnard’s Star has been famous for a long time, not only because of its proximity and because it is the fastest moving star in the night sky, but also because back in the 1960s scientists thought that they found an exoplanet system orbiting it. Those planets were later disproved, but now we believe that we really have found one!

    We are 99% sure that this planet exists. It is a cold super-Earth at least 3.2 times the mass of the Earth, orbiting 60% closer to its parent star than Earth does to the Sun. Even so, Barnard’s Star is so small and cool that it provides this planet with just 2% of the energy that the Earth receives from the Sun, and therefore this planet is a very cold world.

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    Data from many different instruments, including ESO´s planet-hunter HARPS, have revealed this frozen, dimly lit world. (Artist´s impression)
    Credit: ESO/M. Kornmesser

    Q. Why do you think it’s important to search for planets around other stars?

    A. Personally I am involved in this area of research because I want to understand our place in the Universe. I think part of understanding our situation is to find out about nearby planets, to discover their properties and figure out how they formed. This will help us discover whether Earth is unique or whether life could be commonplace in the Universe.

    Much of the Universe is still a complete mystery; at the moment we are exploring it long-distance, from Earth, but perhaps someday in the distant future we will really be able to visit these planets, so we need to find out more about them first.

    Q. So tell us how you went about finding this planet.

    A. We used a technique called the radial velocity, or Doppler, method.

    Radial Velocity Method-Las Cumbres Observatory

    Radial velocity Image via SuperWasp http:// http://www.superwasp.org/exoplanets.htm

    When a planet orbits a star, its gravity pulls the star forwards and backwards just a tiny amount, changing its velocity slightly and making the star wobble. When a star comes towards us, its light becomes “squashed” and the wavelength we see is more blue, and when the star moves away, its light reddens, in what is known as the Doppler effect. This method allows us to find out the minimum mass of the planet, but we must use complementary techniques to determine a planet’s true mass.

    We went through huge amounts of data dating back to the 90s to look for a pattern in this star’s motions and saw that it was moving forwards and backwards with a regular rhythm. The wavelength, and therefore the star’s velocity, varies with a period of roughly 233 days, implying that a planet orbits once every 233 days. Determining how much the wavelength changes over this time allowed us to figure out how fast the star moves towards and away from us. The mass of the planet is related to the change in velocity, so we were able to calculate the minimum mass of the planet to be about three times the mass of Earth.


    This animation shows how astronomers watch for changes in the wavelength of light from a star to search for exoplanets.
    Credit: ESO/L. Calçada

    Q. Planets have been discovered around stars thousands of light-years away. Barnard’s Star is just six light-years away, so why was this planet not found before?

    A. There have actually been many previous searches for planets around Barnard’s Star, and even announcements of discoveries, but not one has ever been confirmed. The thing is that the candidate planet we found is so small and so far from its host star that its effect on the star is really, really tiny. The planet only changed the star’s speed by 4.3 km/h in each direction and with a long period of 233 days, making it extremely difficult to detect. Finding the planet was only possible by collecting an enormous number of velocity measurements. In total, we combined nearly 800 measurements from seven different facilities.

    In particular, between 2016 and 2017 we used the High Accuracy Radial velocity Planet Searcher (HARPS) on the ESO 3.6-metre telescope to observe Barnard’s Star on every possible night that we could, to gather as much information as possible on how its velocity changes over time. It is thanks to HARPS and the CARMENES instrument at Calar Alto Observatory that we can be sufficiently confident that this planet exists.

    ESO/HARPS at La Silla


    ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    CARMENES spectrograph, mounted on the Calar Alto 3.5 meter Telescope, located in Almería province in Spain on Calar Alto, a 2,168-meter-high (7,113 ft) mountain in Sierra de Los Filabres



    Calar Alto 3.5 meter Telescope, located in Almería province in Spain on Calar Alto, a 2,168-meter-high (7,113 ft) mountain in Sierra de Los Filabres

    Q. You say that you are 99% sure that this is a planet. Where does the uncertainty come from? And how certain do you have to be before you are convinced this is a planet?

    A. We would like to be 99.9% certain that this is a planet before we stop observing it. We already feel very sure — it passes all the tests that a planet should pass, but we will continue to make more observations to become more certain.

    The uncertainty comes from the intrinsic error in each radial velocity measurement. In this case, the typical uncertainty of our data is 3.6 km/h, meaning that each velocity measurement we obtain could actually be anywhere within an interval of 3.6 km/h around the value we observe. This is large compared to the velocity values of 4.3 km/h that we are dealing with, so we needed hundreds of measurements to beat down the errors. Furthermore, such precision requires instruments to be extremely stable over timescales of decades so that we can trust that all radial velocities are free from systematic effects. Heat and cold, for example, can affect how instruments operate, so engineers try to keep the instruments at a constant temperature and we are sure to correct for any change. We are convinced that instrument effects cannot be responsible for the 4.3 km/h signal we observed because we see the same value in datasets from different instruments.

    Q. If it isn’t a planet, what else could it be?

    A. There is a small chance that the signal is produced naturally by the star. We found that Barnard’s Star spins very slowly, with a rotation period of about 140 days. As the star rotates, the starspots on its surface rotate with it, appearing and disappearing in a way that could give rise to a signal similar to the one we observed. We calculated the possibility of this to be 0.8% — small, but not zero. More observations will help us decrease this small chance even further and nail the case for the planetary nature of the radial velocity modulations that we are seeing.

    Q. Will you try to confirm that this is a planet in the future? How will you do this?

    A. Absolutely! It’s proximity makes this planet a prime target for exoplanet research. For now, we will continue to collect more radial velocity data to push down the uncertainty even further. Then we would like to observe the planet using different techniques, for example, we could use the Hubble Space Telescope or ESA’s Gaia mission to look for the change in the position of the star in the sky as the planet’s gravity pulls the star around as it orbits. Using a space telescope to do this would tell us more about the properties of this planet.

    NASA/ESA Hubble Telescope

    ESA/GAIA satellite

    This planet is one billion times fainter than its parent star, so it would be extremely difficult to take a direct image of it — we could not dream of doing this with the telescopes that exist today. But now we know where to look for it, we would like to use the amazing imaging capabilities of ESO’s future Extremely Large Telescope to image it.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

    This would reveal a huge amount of information about the planet, for example about its orbit, radius, mass and temperature.

    Q. Earlier you mentioned that scientists thought they found a planet around Barnard’s Star back in the 1960s. Did you see any sign of this “planet” whilst you were carrying out this research?

    A. We did find something! Our analysis revealed that the velocity of Barnard’s Star varies not only with the 233-day period of the planet discovered by us, but also with an intriguing long-term period of 15–20 years. This period is similar to that of the planets proposed in the 1960s but the radial velocity variations are much smaller than would be expected. If the variations were caused by a second planet, it would be very distant from its parent star and with a mass similar to Neptune.

    But we actually think it’s more likely that the long-term variation is caused by changes in the magnetic activity of the star. Just like the Sun — which has a sunspot cycle of about 11 years — Barnard’s Star gets more and less active over time. Very precise position measurements using the Hubble Space Telescope or Gaia could be used to further investigate the possibility of an outer planet orbiting Barnard’s star.

    See the full article here .


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    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

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    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 3:46 pm on July 19, 2017 Permalink | Reply
    Tags: Barnard's Star, , , , , , , , U Chicago Yerkes Observatory   

    From Centauri Dreams: “Keeping an Eye on Ross 128” 

    Centauri Dreams

    July 19, 2017
    Paul Gilster

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    A screen shot from Abel Méndez’s lab note titled “Strange Signals from the Nearby Red Dwarf Star Ross 128.” Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo/Aladin Sky Atlas.

    Frank Elmore Ross (1874-1960), an American astronomer and physicist, became the successor to E. E. Barnard at Yerkes Observatory.

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    U Chicago Yerkes Observatory

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    U Chicago Yerkes Observatory interior

    Barnard, of course, is the discoverer of the high proper motion of the star named after him, alerting us to its proximity.

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    http://www.daviddarling.info/encyclopedia/B/BarnardsStar.html

    And as his successor, Ross would go on to catalog over 1000 stars with high proper motion, many of them nearby. Ross 128, now making news for what observers at the Arecibo Observatory are calling “broadband quasi-periodic non-polarized pulses with very strong dispersion-like features,” is one of these, about 11 light years out in the direction of Virgo.

    NAIC/Arecibo Observatory, Puerto Rico, USA

    Any nearby stars are of interest from the standpoint of exoplanet investigations, though thus far we’ve yet to discover any companions around Ross 128. An M4V dwarf, Ross 128 has about 15 percent of the Sun’s mass. More significantly, it is an active flare star, capable of unpredictable changes in luminosity over short periods. Which leads me back to that unusual reception. The SETI Institute’s Seth Shostak described it this way in a post:

    “What the Puerto Rican astronomers found when the data were analyzed was a wide-band radio signal. This signal not only repeated with time, but also slid down the radio dial, somewhat like a trombone going from a higher note to a lower one.”

    And as Shostak goes on to say, “That was odd, indeed.”

    It’s this star’s flare activity that stands out for me as I look over the online announcement of its unusual emissions, which were noted during a ten-minute spectral observation at Arecibo on May 12. Indeed, Abel Mendez, director of the Planetary Habitability Laboratory at Arecibo, cited Type II solar flares first in a list of possible explanations, though his post goes on to note that such flares tend to occur at lower frequencies. An additional novelty is that the dispersion of the signal points to a more distant source, or perhaps to unusual features in the star’s atmosphere. All of this leaves a lot of room for investigation.

    We also have to add possible radio frequency interference (RFI) into the mix, something the scientists at Arecibo are examining as observations continue. The possibility that we are dealing with a new category of M-dwarf flare is intriguing and would have obvious ramifications given the high astrobiological interest now being shown in these dim red stars.

    All of this needs to be weighed as we leave the SETI implications open. The Arecibo post notes that signals from another civilization are “at the bottom of many other better explanations,” as well they should be assuming those explanations pan out. But we should also keep our options open, which is why the news that the Breakthrough Listen initiative has now observed Ross 128 with the Green Bank radio telescope in West Virginia is encouraging.



    GBO radio telescope, Green Bank, West Virginia, USA

    No evidence of the emissions Arecibo detected has turned up in the Breakthrough Listen data. We’re waiting for follow-up observations from Arecibo, which re-examined the star on the 16th, and Mendez in an update noted that the SETI Institute’s Allen Telescope Array had also begun observations.

    SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA

    Seth Shostak tells us that the ATA has thus far collected more than 10 hours of data, observations which may help us determine whether the signal has indeed come from Ross 128 or has another source.

    “We need to get all the data from the other partner observatories to put all things together for a conclusion,” writes Mendez. “Probably by the end of this week.”
    [Shostak]

    Or perhaps not, given the difficulty of detecting the faint signal and the uncertainties involved in characterizing it. If you’re intrigued, an Arecibo survey asking for public reactions to the reception is now available.

    I also want to point out that Arecibo Observatory is working on a new campaign to observe stars like Ross 128, the idea being to characterize their magnetic environment and radiation. One possible outcome of work like that is to detect perturbations in their emissions that could point to planets — planetary magnetic fields could conceivably affect flare activity. That’s an intriguing way to look for exoplanets, and the list being observed includes Barnard’s Star, Gliese 436, Ross 128, Wolf 359, HD 95735, BD +202465, V* RY Sex, and K2-18.

    A final note: Arecibo is now working with the Red Dots campaign in coordination with other observatories to study Barnard’s Star, for which there is some evidence of a super-Earth mass planet. More on these observations can be found in this Arecibo news release.

    ESO Red Dots Campaign

    Centauri Dreams


    See the full article here .

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    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 11:21 am on July 2, 2017 Permalink | Reply
    Tags: , , Barnard's Star, , ,   

    From EarthSky: “The enduring mystique of Barnard’s Star” 

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    EarthSky

    June 27, 2017
    Larry Sessions

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    Our sun’s closest neighbors among the stars, including Barnard’s Star. Image via NASA PhotoJournal.

    Perhaps you know that, over the scale of our human lifespans, the stars appear fixed relative to one another. But Barnard’s Star – sometimes called Barnard’s Runaway Star – holds a speed record of sorts as the fastest-moving star in Earth’s skies. It moves fast with respect to other stars because it’s relatively close, only about 6 light-years away. What does its fast motion mean? It means Barnard’s Star is nearby! It’s only about six light-years away. Relative to other stars, Barnard’s Star moves 10.3 arcseconds per year, or about the width of a full moon in 174 years. This might not seem like much. But – to astronomers – Barnard’s Star is virtually zipping across the sky. Follow the links below to learn more about Barnard’s Star, which has high interest for astronomers and the public alike.

    Barnard’s Star in history and popular culture

    How to see Barnard’s Star

    The science of Barnard’s Star

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    Barnard’s star, 1985 to 2005. Most stars are fixed with respect to each other, but – being close to us – Barnard’s Star appears to move. Image via Steve Quirk/ Wikimedia Commons.

    Barnard’s Star in history and popular culture Yerkes Observatory astronomer E. E. Barnard discovered the large proper motion of Barnard’s Star – that is, motion across our line of sight – in 1916.

    He noticed it while comparing photographs of the same part of the sky taken in 1894 and again in 1916. The star appeared in significantly different positions, betraying its rapid motion.

    Later, Harvard astronomer Edward Pickering found the star on photographic plates taken in 1888.

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    Barnard’s Star is named for this astronomer, E.E. Barnard, seen here posing with the 36? refractor at Lick Observatory. Image via OneMinuteAstronomer.

    UCO Lick Observatory, Mt Hamilton, in San Jose, California

    The UCO Lick C. Donald Shane telescope is a 120-inch (3.0-meter) reflecting telescope located at the Lick Observatory, Mt Hamilton, in San Jose, California

    UC Observatories Lick Aumated Planet Finder, fully robotic 2.4-meter optical telescope at Lick Observatory, situated on the summit of Mount Hamilton, east of San Jose, California, USA

    Lick Observatory, Mt Hamilton, in San Jose, California

    Barnard’s star came to our attention barely 100 years ago and cannot even be seen with the human eye, so the ancients did not know about it. It doesn’t figure into the lore of any constellation or cultural tradition. But that doesn’t mean that it doesn’t a have certain mystique about it that extends beyond the known facts.

    For example, even as long ago as the 1960s and ’70s – long before successful planet-hunters like the Kepler spacecraft – there were suggestions that Barnard’s Star might have a family of planets. At that time, reported discrepancies in the motion of the star led to a claim that at least one Jupiter-size planet orbits it. Although the evidence was disputed and the claim now largely discredited, there is still a chance of planetary discoveries.

    It’s likely due to this rumor of planets that Barnard’s Star has found a place in science fiction. It’s featured in, for example, The Hitchhiker’s Guide to the Galaxy by Douglas Adams; The Garden of Rama by Arthur C. Clarke and Gentry Lee; and several novels of physicist Robert L. Forward. In these works, the hypothetical planets are locations for early colonization or way-stations for exploration further into the cosmos.

    Barnard’s Star also was the hypothetical target of Project Daedalus, a design study by members of the British Interplanetary Society, in which they envisioned an interstellar craft that could reach its destination within a human lifetime.

    Clearly, Barnard’s Star captures peoples’ imaginations!

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    Image via BBC/ Sky at Night/ Paul Wootton. Read more.

    How to see Barnard’s Star. Barnard’s Star is faint; its visual magnitude of about 9.5. Thus this star can’t be seen with the eye alone.

    Whats more, its motion – though large in astronomical terms – is still too slow to be noticed in a single night or even easily across a human lifetime.

    Since Barnard’s Star can’t be seen without powerful binoculars or a telescope, finding it requires both experience and perseverance. It is currently located in the constellation Ophiuchus, which is well placed on June, July and August evenings.

    Because Barnard’s Star is a telescopic object, details on how to observe it are beyond the scope of this article, but Britain’s Sky at Night magazine has a good procedure online here: http://bit.ly/2rZNDe1

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    Artist’s concept of a red dwarf star – similar to Barnard’s Star – with a planet of about 12 Jupiter-masses. There has been speculation about planets orbiting Barnard’s Star, but none have been confirmed. Also, Barnard’s Star is thought to be considerably older than our sun, which could affect the potential for finding life there. Image via NASA/ ESA/ G. Bacon (STScI)/ Wikimedia Commons.

    The science of Barnard’s Star. The fame of Barnard’s Star is in its novelty, the fact that it moves fastest through Earth’s skies. But its real importance to astronomy lies in the fact that being so close, it is one of the best sources for studying red dwarfs, the most abundant stars in the universe.

    With only about 14% of the solar mass and less than 20% of the radius, it would take roughly seven Barnard’s Stars to match the mass of our sun, and 133 to match our sun’s volume.

    Like all stars, Barnard’s Star shines via thermonuclear fusion, changing light elements (hydrogen) into more massive elements (helium), while releasing enormous amounts of energy. Even so, the lower mass of Barnard’s Star makes it about 2,500 times less powerful than our sun.

    In other words, Barnard’s Star is much dimmer and cooler than our sun. If it replaced the sun in our solar system, it would shine only about four ten-thousandths as brightly as our sun. At the same time, it would be about 100 times brighter than a full moon. No life on Earth would be possible if we orbited Barnard’s Star instead of our sun, however. The much-decreased stellar heat would plunge Earth’s global temperatures to hundreds of degrees below zero.

    Although very common, red dwarfs like Barnard’s Star are typically dim. Thus they are notoriously faint and hard to study. In fact, not a single red dwarf can be seen with the unaided human eye. But because Barnard’s Star is relatively close and bright, it has become a go-to model for all things red dwarf.

    At nearly six light-years’ distance, Barnard’s Star is often cited as the second-closest star to our sun (and Earth). This is true only if you consider the triple star system Alpha Centauri as one star.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    ESO Pale Red Dot project

    ESO Red Dots Campaign

    Proxima Centauri, the smallest and faintest of Alpha Centauri’s three components, is the closest known star to the sun at just 4.24 light years away. It, too, is a red dwarf. So Barnard’s Star is only the second-closest red dwarf star. It is perhaps more important for astronomical purposes, though, because Proxima is four times fainter and thus harder to study.

    Special thanks to David J. Darling and Jack Schmidling for their help with this article.

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    Of course, all stars are moving through the space of our Milky Way galaxy. So even the “fixed” stars move over time. This illustration shows the distances to the nearest stars – including Barnard’s Star – in a time range between 20,000 years in the past and 80,000 years in the future. Image via FrancescoA/ Wikimedia Commons.

    Bottom line: Barnard’s Star is the fastest-moving star in Earth’s skies, in terms of its proper motion. It moves fast because it’s relatively close, only about 6 light-years away.

    See the full article here .

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