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  • richardmitnick 1:52 pm on March 28, 2019 Permalink | Reply
    Tags: "Two New Planets Discovered Using Artificial Intelligence", AI helps us search the data set uniformly, , K2 data is more challenging to work with because the spacecraft was moving around all the time, McDonald Observatory, , , Of the two planets one is called K2-293b and orbits a star 1300 light-years away in the constellation Aquarius. The other K2-294b orbits a star 1230 light-years away also located in Aquarius.,   

    From University of Texas at Austin: “Two New Planets Discovered Using Artificial Intelligence” 

    U Texas Austin bloc

    From University of Texas at Austin

    McDonald Observatory U Texas at Austin

    U Texas at Austin McDonald Observatory, Altitude 2,070 m (6,790 ft)

    26 March 2019

    Media Contact:
    Rebecca Johnson, Communications Mgr.
    rjohnson@astro.as.utexas.edu
    McDonald Observatory
    512-475-6763

    Science Contacts:
    Anne Dattilo
    anne.dattilo@utexas.edu
    Department of Astronomy
    512-471-6493

    Dr. Andrew Vanderburg
    %u200Bavanderburg@utexas.edu
    Department of Astronomy
    512-471-6493

    Astronomers at The University of Texas at Austin, in partnership with Google, have used artificial intelligence (AI) to uncover two more hidden planets in the Kepler space telescope archive. The technique shows promise for identifying many additional planets that traditional methods could not catch.

    The planets discovered this time were from Kepler’s extended mission, called K2.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    3
    Anne Dattilo

    To find them, the team, led by an undergraduate at UT Austin, Anne Dattilo, created an algorithm that sifts through the data taken by Kepler to ferret out signals that were missed by traditional planet-hunting methods. Long term, the process should help astronomers find many more missed planets hiding in Kepler data. The discoveries have been accepted for publication in an upcoming issue of The Astronomical Journal.

    Other team members include NASA Sagan fellow at UT Austin Andrew Vanderburg and Google engineer Christopher Shallue. In 2017, Vanderburg and Shallue first used AI to uncover a planet around a Kepler star — one already known to harbor seven planets. The discovery made that solar system the only one known to have as many planets as our own.

    Dattilo explained that this project necessitated a new algorithm, as data taken during Kepler’s extended mission K2 differs significantly from that collected during the spacecraft’s original mission.

    “K2 data is more challenging to work with because the spacecraft is moving around all the time,” Vanderburg explained. This change came about after a mechanical failure. While mission planners found a workaround, the spacecraft was left with a wobble that AI had to take into account.

    The Kepler and K2 missions have already discovered thousands of planets around other stars, with an equal number of candidates awaiting confirmation. So why do astronomers need to use AI to search the Kepler archive for more?

    “AI will help us search the data set uniformly,” Vanderburg said. “Even if every star had an Earth-sized planet around it, when we look with Kepler, we won’t find all of them. That’s just because some of the data’s too noisy, or sometimes the planets are just not aligned right. So, we have to correct for the ones we missed. We know there are a lot of planets out there that we don’t see for those reasons.

    “If we want to know how many planets there are in total, we have to know how many planets we’ve found, but we also have to know how many planets we missed. That’s where this comes in,” he explained.

    The two planets Dattilo’s team found “are both very typical of planets found in K2,” she said. “They’re really close in to their host star, they have short orbital periods, and they’re hot. They are slightly larger than Earth.”

    Of the two planets, one is called K2-293b and orbits a star 1,300 light-years away in the constellation Aquarius. The other, K2-294b, orbits a star 1,230 light-years away, also located in Aquarius.

    Once the team used their algorithm to find these planets, they followed up by studying the host stars using ground-based telescopes to confirm that the planets are real. These observations were done with the 1.5-meter telescope at the Smithsonian Institution’s Whipple Observatory in Arizona and the Gillett Telescope at Gemini Observatory in Hawaii.

    The 1.5-meter Tillinghast Telescope, Fred Lawrence Whipple Observatory,Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m 8,550 ft


    Frederick C Gillett Gemini North Telescope Maunakea, Hawaii, USA

    The future of the AI concept for finding planets hidden in data sets looks bright. The current algorithm can be used to probe the entire K2 data set, Dattilo said — approximately 300,000 stars. She also believes the method is applicable to Kepler’s successor planet-hunting mission, TESS, which launched in April 2018. Kepler’s mission ended later that year.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    Dattilo plans to continue her work using AI for planet hunting when she enters graduate school in the fall.

    See the full article here
    .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Texas at Austin

    U Texas Austin campus

    In 1839, the Congress of the Republic of Texas ordered that a site be set aside to meet the state’s higher education needs. After a series of delays over the next several decades, the state legislature reinvigorated the project in 1876, calling for the establishment of a “university of the first class.” Austin was selected as the site for the new university in 1881, and construction began on the original Main Building in November 1882. Less than one year later, on Sept. 15, 1883, The University of Texas at Austin opened with one building, eight professors, one proctor, and 221 students — and a mission to change the world. Today, UT Austin is a world-renowned higher education, research, and public service institution serving more than 51,000 students annually through 18 top-ranked colleges and schools.

     
  • richardmitnick 2:39 pm on March 24, 2017 Permalink | Reply
    Tags: , , , , , , McDonald Observatory, ,   

    From WIRED: “Astronomers Don’t Point This Telescope—The Telescope Points Them” 

    Wired logo

    WIRED

    03.23.17
    Sarah Scoles

    1
    U Texas Austin McDonald Observatory Hobby-Eberly Telescope

    The hills of West Texas rise in waves around the Hobby-Eberly Telescope, a powerful instrument encased in a dome that looks like the Epcot ball. Soon, it will become more powerful still: Scientists recently primed the telescope to find evidence of dark energy in the early universe, prying open its eye so it can see and process a wide swath of sky. On April 8, scientists will dedicate the new telescope, capping off the $40 million upgrade and beginning the real work.

    The dark energy experiment, called Hetdex, isn’t how astronomy has traditionally been done. In the classical model, a lone astronomer goes to a mountaintop and solemnly points a telescope at one predetermined object. But Hetdex won’t look for any objects in particular; it will just scan the sky and churn petabytes of the resulting data through a silicon visual cortex. That’s only possible because of today’s steroidal computers, which let scientists analyze, store, and send such massive quantities of data.

    “Dark energy is not only terribly important for astronomy, it’s the central problem for physics. It’s been the bone in our throat for a long time.”

    Steven Weinberg
    Nobel Laureate
    University of Texas at Austin

    The hope is so-called blind surveys like this one will find stuff astronomers never even knew to look for. In this realm, computers take over curation of the sky, telling astronomers what is interesting and worthy of further study, rather than the other way around. These wide-eyed projects are becoming a standard part of astronomers’ arsenal, and the greatest part about them is that their best discoveries are still totally TBD.

    Big Sky Country

    To understand dark energy—that mysterious stuff that pulls the taffy of spacetime—the Hetdex team needed Hobby-Eberly to study one million galaxies 9-11 billion light-years away as they fly away from Earth. To get that many galaxies in a reasonable amount of time, they broadened the view of its 91 tessellated stop-sign-shaped mirrors by 100. They also created an instrument called Virus, with 35,000 optical fibers that send the light from the universe to a spectrograph, which splits it up into constituent wavelengths. All that data can determine both how far away a galaxy is and how fast it’s traveling away from Earth.

    But when a telescope takes a ton of data down from the sky, scientists can also uncover the unexpected. Hetdex’s astronomers will find more than just the stretch marks of dark energy. They’ll discover things about supermassive black holes, star formation, dark matter, and the ages of stars in nearby galaxies.

    The classical method still has advantages; if you know exactly what you want to look at, you write up a nice proposal to Hubble and explain why a fixed gaze at the Whirlpool Galaxy would yield significant results. “But what you see is what you get,” says astronomer Douglas Hudgins. “This is an object, and the science of that object is what you’re stuck with.”

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

     
  • richardmitnick 12:30 pm on December 19, 2015 Permalink | Reply
    Tags: , Finding Jupiter like planets, McDonald Observatory   

    From McDonald Observatory: “High School Student Helps Discover New Planet, Calculates Frequency of Jupiter-like Planets” 

    McDonald Observatory bloc

    McDonald Observatory

    9 December 2015
    Science Contact:
    Dr. Stefano Meschiari, W.J. McDonald Postdoctoral Researcher
    McDonald Observatory, The University of Texas at Austin
    512-471-3574

    1
    Dominick Rowan

    2
    This artist’s concept shows the relative sizes and separation of the star HD 32963 and its newly discovered Jupiter-mass planet. Credit: Stefano Meschiari/McDonald Observatory. Media Contact Rebecca Johnson ph: 512-475-6763 fax: 512-471-5060 rjohnson@astro.as.utexas.edu

    2
    This artist’s concept shows the orbit of the newly discovered Jupiter-mass planet orbiting the star HD 32963, compared to the orbits of Earth and Jupiter around the Sun. Credit: Stefano Meschiari/McDonald Observatory

    High school senior Dominick Rowan of Armonk, New York, is making discoveries about other worlds. Working with University of Texas at Austin astronomer Stefano Meschiari, Rowan has helped to find a Jupiter-like planet and has calculated that this type of planet is relatively rare, occurring in three percent of stars overall. Their research is has been accepted for publication in the Astrophysical Journal.

    The team, which also includes astronomers from the University of California, Santa Cruz and others, announced their newly discovered planet orbits a Sun-like star called HD 32963. They discovered the planet using observations with the Keck Telescope in Hawaii.

    Keck Observatory
    Keck Observatory Interior
    Keck Observatory

    While working on this project, Rowan said that he became interested in how these large, Jupiter-like planets are so important to the formation of planetary systems.

    “The story of our solar system is really the story of Jupiter,” Meschiari explained. “It’s important for us to find Jupiter analogs to find other solar systems like ours.”

    Meschiari suggested to Rowan that he could undertake a project to calculate how often Jupiter-like planets form, using the sample of more than 1,000 stars that the team has probed with the Keck Telescope over the past two decades, looking for planets around them.

    “It was a collaborative process,” Meschiari said. “We went through every dataset — every star — to look at how many Jupiters they have, or how many could have been missed.”

    They used software previously created by Meschiari, called Systemic. An online version of it, called “Systemic Live,” is used in astronomy classes at colleges across the country. It is a web-based application that lets students visualize and manipulate real data from telescopes around the world, to try to find the signatures of extrasolar planets as-yet unknown.

    Rowan explained that when he started the project, “the first objective of the study was to detect all the Jupiter analogs in the Keck survey to calculate their frequency. However, after identifying HD 32963b as a new, unpublished Jupiter analog, Dr. Meschiari and I worked to constrain the planetary parameters as an additional objective of the research.

    “After detecting a total of eight Jupiter analogs within the datasets, we worked to correct the frequency for detectability. In other words, it was necessary to assess the probability that a Jupiter analog was missed.”

    Rowan has submitted his work into several science competitions. Among other honors, he has been selected as a national finalist for the Siemens Competition in Math, Science, and Technology. More than just competing for awards, however, he said, “working with Dr. Meschiari has solidified my interest in astrophysics and extrasolar studies.”

    In addition to his widely used academic software, Meschiari has created a popular online game called “Super Planet Crash.” It allows anyone to create a virtual solar system with planets of various masses and orbits. They can then set the system in motion to see how it fares over cosmic time, whether it is stable, or planets crash into each other, or get slung out of the system via gravitational interactions. Super Planet Crash has been played more than 11 million times. It can be found at http://www.save-point.io

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    McDonald Observatory Campus

    Telescopes Are Windows To the Universe

    Astronomers use them to study everything from the asteroids and planets in our own solar system to galaxies billions of light-years away in space and time. Though they bring the mysteries of the universe to us, their workings are anything but mysterious. They gather and focus light from objects in the sky, so that it can be directed into an instrument attached to the telescope, and ultimately, studied in detail by a scientist. At McDonald Observatory, we have several telescopes, built at various times since the Observatory’s founding in the 1930s.

    Here is an introduction to the telescopes that McDonald Observatory astronomers use for their research:

    McDonald Observatory Hobby-Eberly Telescope
    Hobby-Eberly Telescope

    McDonald Observatory Harlan J Smith Telescope
    Harlan J. Smith Telescope

    McDonald Observatory Otto Struve telescope
    Otto Struve Telescope

    McDonald Observatory .8 meter telescope
    0.8-meter Telescope

    McDonald Observatory .9 meter telescope
    0.9-meter Telescope

    McDonald Observatory Rebecca Gale  Telescope Park
    Rebecca Gale Telescope Park

     
  • richardmitnick 4:27 pm on December 7, 2015 Permalink | Reply
    Tags: , , McDonald Observatory,   

    From McDonald Obsrvatory: “Texas Astronomer Solves Mystery of ‘Born Again’ Stars with Hubble Space Telescope” 

    McDonald Observatory bloc

    McDonald Observatory

    7 December 2015
    Media contacts:
    Rebecca Johnson, UT Austin McDonald Observatory: 512-475-6763
    Ray Villard, Space Telescope Science Institute: 410-338-4514

    Science Contact:
    Dr. Natalie Gosnell, W.J. McDonald Postdoctoral Fellow, UT Austin McDonald Observatory: 512-471-3423

    1
    Left: A normal star in a binary system gravitationally pulls in matter from an aging companion star that has swelled to a bloated red giant that has expanded to a few hundred times of its original size. Right: After a couple hundred million years the red giant star has burned out and collapsed to the white dwarf that shines intensely in ultraviolet wavelengths. The companion star has bulked up on the hydrogen siphoned off of the red giant star to become much hotter, brighter and bluer than it was previously. Credit: NASA/ESA, A. Feild (STScI)

    University of Texas astronomer Natalie Gosnell has used Hubble Space Telescope to better understand why some stars aren’t evolving as predicted.

    NASA Hubble Telescope
    NASA/ESA Hubble

    These so-called blue stragglers look hotter and bluer than they should for their advanced age. It’s almost as it they were somehow reinvigorated to look much younger than they really are.

    Though blue stragglers were first identified 62 years ago, astronomers have yet to converge on a solution for their odd appearance. The most popular explanation among several competing theories is that an aging star spills material onto a smaller companion star. The small star bulks up on mass to become hotter and bluer while the aging companion burns out and collapses to a white dwarf – a burned out cinder.

    To test this theory Gosnell’s team conducted a survey of the open star cluster NGC 188 that has 21 blue stragglers. Of those, she found that seven had white dwarf companions, by identifying their ultraviolet glow that is detectable by Hubble.

    Of the remaining 14 of the 21 blue stragglers, a further seven show evidence of so-called mass transfer between stars in other ways. Gosnell said she believes these are older white dwarf-blue straggler binaries, and indicate two-thirds of blue stragglers form through mass transfer.

    “This was really great,” Gosnell says. “Until now there was no concrete observational proof, only suggestive results,” Gosnell said. “It’s the first time we can place limits on the fraction of blue stragglers formed through mass transfer.”

    This discovery sheds light on the physical processes responsible for changing the appearance of 25 percent of evolved stars. Gosnell’s work, which closes gaps in our understanding of how stars age, is published in the current issue of The Astrophysical Journal.

    The problem came to light because in recent years, astronomers have been able to make a complete and accurate census of stars in a number of open star clusters, Gosnell said.

    “Open clusters really are the best laboratory for the study of stellar evolution,” Gosnell said. “They have a simple stellar population.” The stars in a cluster form at the same time and from the same materials, she explained.

    The cluster population studies revealed that up to a quarter of the oldest stars “are not evolving like we think they’re supposed to,” Gosnell said. Stars that astronomers expected to become red giants (like Aldebaran, the eye of Taurus, the bull) instead became “blue stragglers,” unexpectedly bright, blue stars with a host of strange characteristics.

    Gosnell wanted to find out what happened to them. So she, along with Bob Mathieu at the University of Wisconsin-Madison and their collaborators, designed a study using Hubble Space Telescope’s Advanced Camera for Surveys [ACS] to try to differentiate between three theories of how these stars became blue stragglers.

    NASA Hubble ACS
    ACS

    The theories included: collisions between stars in the cluster (with debris coalescing to form a blue straggler), the merger of two of the stars in a triple star system, or mass transfer between two stars in a binary pair.

    In a binary pair of stars, the larger star will evolve faster, Gosnell said. That star becomes a red giant. A red giant is so bloated that the outermost layers of gas on its surface are only tenuously held by the star’s gravity. They can be pulled off by the gravity of the companion star. This is mass transfer.

    As the gas is siphoned off by the partner, the red giant is left with only its core, making it into a white dwarf. The partner — initially the less massive of the pair, but now the heavier one — becomes a blue straggler.

    Gosnell’s method is limited by the fact that it will not detect white dwarfs that have cooled down enough so that they don’t glow in UV light detectable by Hubble, she said. That means that only those white dwarfs formed in the last 250 million years (youngsters, astronomically speaking) are detectable.

    Knowing more about how these stars form is important because astronomers use their assumptions to model the stellar populations of distant galaxies (where the light from all the stars blends together). “You don’t want to be ignoring 25 percent of the evolved stars” in those galaxies, Gosnell said.

    Such models are important because distant galaxies figure into many different types of cosmological studies. Right now, Gosnell said, “the models have a lot of room for improvement.”

    “If we tweak the way models treat mass transfer, that would bring the observations and theory together,” Gosnell said. “They would agree. And we can use this to inform our understanding of unresolved stellar populations” — that is, those stars in galaxies so far away that all their light is blended together.

    The science team comprises N. Gosnell (University of Texas, Austin), R. Mathieu (University of Wisconsin, Madison), A. Geller (Northwestern University and University of Chicago), A. Sills (McMaster University), N. Leigh (University of Alberta and American Museum of Natural History), and C. Knigge (University of Southampton, UK).

    Gosnell plans to continue studying these stars using the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory and its IGRINS spectrograph to constrain the number of blue stragglers that could form through mergers in triple systems.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    McDonald Observatory Campus

    Telescopes Are Windows To the Universe

    Astronomers use them to study everything from the asteroids and planets in our own solar system to galaxies billions of light-years away in space and time. Though they bring the mysteries of the universe to us, their workings are anything but mysterious. They gather and focus light from objects in the sky, so that it can be directed into an instrument attached to the telescope, and ultimately, studied in detail by a scientist. At McDonald Observatory, we have several telescopes, built at various times since the Observatory’s founding in the 1930s.

    Here is an introduction to the telescopes that McDonald Observatory astronomers use for their research:

    McDonald Observatory Hobby-Eberly Telescope
    Hobby-Eberly Telescope

    McDonald Observatory Harlan J Smith Telescope
    Harlan J. Smith Telescope

    McDonald Observatory Otto Struve telescope
    Otto Struve Telescope

    McDonald Observatory .8 meter telescope
    0.8-meter Telescope

    McDonald Observatory .9 meter telescope
    0.9-meter Telescope

    McDonald Observatory Rebecca Gale  Telescope Park
    Rebecca Gale Telescope Park

     
  • richardmitnick 5:44 pm on November 20, 2015 Permalink | Reply
    Tags: , , , McDonald Observatory,   

    From McDonald Observatory: “Early Galaxies More Efficient at Making Stars, Hubble Survey Reveals” 

    McDonald Observatory bloc

    McDonald Observatory

    19 November 2015
    Science Contact:
    Dr. Steven Finkelstein
    The University of Texas at Austin
    512-471-1483

    1
    Galaxies in HST’s CANDELS GOODS-South Field

    A study published in today’s Astrophysical Journal by University of Texas at Austin assistant professor Steven Finkelstein and colleagues reveals that galaxies were more efficient at making stars when the universe was younger. The announcement explains the team’s discovery, announced in the journal’s September 1 issue, that there are a lot more bright, highly star-forming galaxies in the early universe than scientists previously thought.

    “This was an unexpected result,” Finkelstein said. “It has implications for galaxy formation at the earliest times” in the universe.

    For both studies, his team used galaxy observations from Hubble Space Telescope’s CANDELS survey, of which he is a team member. Hubble’s largest survey to date, CANDELS stands for Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey.

    NASA Hubble CANDELS

    NASA Hubble Telescope
    NASA/ESA Hubble

    Today’s finding stems from studies of about 8,000 CANDELS galaxies seen at times ranging from 0.75 to 1.5 billion years after the Big Bang (that is, between redshift four and redshift seven). As the universe is a little less than 14 billion years old, this corresponds to only the first five to 10 percent of the history of the universe.

    The team deduced the rate of star formation in these galaxies from the Hubble images, by noting their brightness in ultraviolet light, and then correcting this measurement depending on how much light-absorbing dust the galaxy contains. The dust estimation comes from the Hubble images, too. The redder a galaxy is, the dustier it is.

    Investigating the highly star-forming galaxies further, they compared the mass in stars in these galaxies to the theoretically predicted rate at which galaxies grow their mass in the early universe. They found higher masses than predicted, implying that galaxies are more efficient at turning gas into stars in the early universe than they are today.

    There could be a couple of different reasons why, Finkelstein said.

    First, as the universe has been expanding outward since the Big Bang, at earlier times everything in the universe was packed closer together, including the gas in galaxies. Dense gas is the material that makes stars, so perhaps these galaxies simply had more of it.

    Second: feedback. “No galaxy is 100 percent efficient at turning gas into stars,” Finkelstein said, explaining that there are several mechanisms inside galaxies that can cause some of the gas to not form stars. These include things like the massive explosions called supernovae, winds from massive stars, and active supermassive black holes that can heat their surrounding gas. Altogether, these barriers to star formation collectively are called “feedback.” Finkelstein said that galaxies at earlier times may experience less feedback, and so may form stars more readily.

    He anticipates that these bright galaxies in the early universe can be studied in greater detail with the forthcoming James Webb Space Telescope (JWST), the infrared successor to Hubble, which will launch in 2018. Future studies with JWST should provide a better understanding of star formation in early galaxies.

    NASA Webb Telescope
    JWST

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    McDonald Observatory Campus

    Telescopes Are Windows To the Universe

    Astronomers use them to study everything from the asteroids and planets in our own solar system to galaxies billions of light-years away in space and time. Though they bring the mysteries of the universe to us, their workings are anything but mysterious. They gather and focus light from objects in the sky, so that it can be directed into an instrument attached to the telescope, and ultimately, studied in detail by a scientist. At McDonald Observatory, we have several telescopes, built at various times since the Observatory’s founding in the 1930s.

    Here is an introduction to the telescopes that McDonald Observatory astronomers use for their research:

    McDonald Observatory Hobby-Eberly Telescope
    Hobby-Eberly Telescope

    McDonald Observatory Harlan J Smith Telescope
    Harlan J. Smith Telescope

    McDonald Observatory Otto Struve telescope
    Otto Struve Telescope

    McDonald Observatory .8 meter telescope
    0.8-meter Telescope

    McDonald Observatory .9 meter telescope
    0.9-meter Telescope

    McDonald Observatory Rebecca Gale  Telescope Park
    Rebecca Gale Telescope Park

     
  • richardmitnick 3:04 pm on August 27, 2015 Permalink | Reply
    Tags: , , McDonald Observatory   

    From U Texas McDonald Observatory: “Dying Stars Suffer from ‘Irregular Heartbeats'” 

    McDonald Observatory bloc

    McDonald Observatory

    26 August 2015

    1
    White Dwarf Outburst

    2
    Keaton Bell

    Some dying stars suffer from ‘irregular heartbeats,’ research led by astronomers at The University of Texas at Austin and the University of Warwick has discovered.

    The team discovered rapid brightening events — outbursts — in two otherwise normal pulsating white dwarf stars. Ninety-seven percent of all stars, including the Sun, will end their lives as extremely dense white dwarfs after they exhaust their nuclear fuel. Such outbursts have never been seen in this type of star before.

    “It’s the discovery of an entirely new phenomenon,” said graduate student Keaton Bell of The University of Texas at Austin. Bell reported the first pulsating white dwarf to show these outbursts, KIC 4552982, in a recent issue of The Astrophysical Journal.

    This week, a team led by recent University of Texas PhD J.J. Hermes, now of the University of Warwick, is reporting the second white dwarf to show this trait: PG1149+057. Hermes’ team includes Bell and others from The University of Texas. Their research is published in the current Astrophysical Journal Letters.

    Both white dwarf discoveries were made using data from the Kepler space mission.

    NASA Kepler Telescope
    Kepler

    The Kepler spacecraft trails Earth in its orbit around the Sun, recording time lapse movies of a few patches of sky for months on end.

    The Kepler data show that in addition to the regular rhythm of pulsations expected from a white dwarf, which cause the star to get a few percent brighter and fainter every few minutes, both stars also experienced arrhythmic, massive outbursts every few days, breaking their regular pulse and significantly heating up their surfaces for many hours.

    “We have essentially found rogue waves in a pulsating star, akin to ‘irregular heartbeats,’” Hermes explained. “These were truly a surprise to see: We have been watching pulsating white dwarfs for more than 50 years now from the ground, and only by being able to stare uninterrupted for months from space have we been able to catch these events.”

    Bell elaborated: “When we build a telescope that observes the sky in an entirely new way, we’re going to end up discovering things that we never expected.” Though Kepler’s notoriety derives from its prowess as a planet hunter, “it’s told us at least as much about stars as it has about planets,” Bell said.

    White dwarfs have been known to pulsate for decades, and some are exceptional clocks, with pulsations that have kept nearly perfect time for more than 40 years. Pulsations are believed to be a naturally occurring stage when a white dwarf reaches the right temperature to generate a mix of partially ionized hydrogen atoms at its surface.

    That mix of excited atoms can store up and then release energy, causing the star to resonate with pulsations characteristically every few minutes. Astronomers can use the regular periods of these pulsations just like seismologists use earthquakes on Earth, to see below the surface of the star into its exotic interior. This was why astronomers targeted these stars with Kepler, hoping to learn more about their dense cores. In the process, they caught these unexpected outbursts.

    “These are highly energetic events, which can raise the star’s overall brightness by more than 15% and its overall temperature by more than 750 degrees in a matter of an hour,” Hermes said. “For context, the Sun will only increase in overall brightness by about 1% over the next 100 million years.”

    There is a narrow range of surface temperatures where pulsations can be excited in white dwarfs, and so far irregularities have only been seen in the coolest of those that pulsate. Thus, these irregular outbursts may not be just an oddity; they have the potential to change the way astronomers understand how pulsations, the regular heartbeats, ultimately cease in white dwarfs.

    “The theory of stellar pulsations has long failed to explain why pulsations in white dwarfs stop at the temperature we observe them to,” Texas’ Keaton Bell said. “That both stars exhibiting this new outburst phenomenon are right at the temperature where pulsations shut down suggests that the outbursts could be the key to revealing the missing physics in our pulsation theory.”

    Astronomers are still trying to settle on an explanation for these outbursts. Given the similarity between the first two stars to show this behavior, they suspect it might have to do with how the pulsation waves interact with themselves, perhaps via a resonance.

    “Ultimately, this may be a new type of nonlinear behavior that is triggered when the amplitude of a pulsation passes a certain threshold, perhaps similar to rogue waves on the open seas here on Earth, which are massive, spontaneous waves that can be many times larger than average surface waves,” Hermes said. “Still, this is a fresh discovery from observations, and there may be more to these irregular stellar heartbeats than we can imagine yet.”

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    McDonald Observatory Campus

    Telescopes Are Windows To the Universe

    Astronomers use them to study everything from the asteroids and planets in our own solar system to galaxies billions of light-years away in space and time. Though they bring the mysteries of the universe to us, their workings are anything but mysterious. They gather and focus light from objects in the sky, so that it can be directed into an instrument attached to the telescope, and ultimately, studied in detail by a scientist. At McDonald Observatory, we have several telescopes, built at various times since the Observatory’s founding in the 1930s.

    Here is an introduction to the telescopes that McDonald Observatory astronomers use for their research:

    McDonald Observatory Hobby-Eberly Telescope
    Hobby-Eberly Telescope

    McDonald Observatory Harlan J Smith Telescope
    Harlan J. Smith Telescope

    McDonald Observatory Otto Struve telescope
    Otto Struve Telescope

    McDonald Observatory .8 meter telescope
    0.8-meter Telescope

    McDonald Observatory .9 meter telescope
    0.9-meter Telescope

    McDonald Observatory Rebecca Gale  Telescope Park
    Rebecca Gale Telescope Park

     
  • richardmitnick 9:44 pm on January 30, 2015 Permalink | Reply
    Tags: , , , McDonald Observatory   

    From McDonald Observatory: “Black Hole Chokes on a Swallowed Star” 

    McDonald Observatory bloc

    McDonald Observatory

    A five-year analysis of an event captured by a tiny telescope at McDonald Observatory and followed up by telescopes on the ground and in space has led astronomers to believe they witnessed a giant black hole tear apart a star. The work is published this month in The Astrophysical Journal.

    1
    When a star encounters a black hole, tidal forces stretch the star into an elongated blob before tearing it apart, as seen in these images from a computer simulation by James Guillochon of Harvard University.

    On January 21, 2009, the ROTSE IIIb telescope at McDonald caught the flash of an extremely bright event. The telescope’s wide field of view takes pictures of large swathes of sky every night, looking for newly exploding stars as part of the ROTSE Supernova Verification Project (RSVP). Software then compares successive photos to find bright “new” objects in the sky — transient events like the explosion of a star or a gamma-ray burst.

    McDonald Observatory ROTSE-IIIb Telescope
    ROTSE-IIIb telescope

    With a magnitude of -22.5, this 2009 event was as bright as the “superluminous supernovae” (a new category of the brightest stellar explosions known) that the ROTSE team discovered at McDonald in recent years. The team nicknamed the 2009 event “Dougie,” after a character in the cartoon South Park. (Its technical name is ROTSE3J120847.9+430121.)

    The team thought Dougie might be a supernova, and set about looking for its host galaxy (which would be much too faint for ROTSE to see). They found that the Sloan Digital Sky Survey [SDSS] had mapped a faint red galaxy at Dougie’s location. The team followed that up with new observations of the galaxy with one of the giant Keck telescopes in Hawaii, pinpointing the galaxy’s distance at three billion light-years.

    Sloan Digital Sky Survey Telescope
    SDSS Telescope

    Keck Observatory
    Keck Observatory

    These deductions meant Dougie had a home — but just what was he? Team members had four possibilities: a superluminous supernova; a merger of two neutron stars; a gamma-ray burst; or a “tidal disruption event” — a star being pulled apart as it neared its host galaxy’s central black hole.

    2
    Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background

    To narrow it down, they studied Dougie in various ways. They made ultraviolet observations with the orbiting Swift telescope, and took many spectra from the ground with the 9.2-meter Hobby-Eberly Telescope at McDonald. Finally, they used computer models of how the light from different possible physical processes that might explain how Dougie would behave — how it varies in brightness over time, and what chemical signatures it might show — and compared them to Dougie’s actual behavior.

    NASA SWIFT Telescope
    NASA/Swift

    In detail, Dougie did not look like a supernova. The neutron star merger and gamma-ray burst possibilities were similarly eliminated.

    “When we discovered this new object, it looked similar to supernovae we had known already,” said lead author Jozsef Vinko of the University of Szeged in Hungary. “But when we kept monitoring its light variation, we realized that this was something nobody really saw before. Finding out that it was probably a supermassive black hole eating a star was a fascinating experience,” Vinko said.

    Team member J. Craig Wheeler, leader of the supernova group at The University of Texas at Austin, elaborated. “We got the idea that it might be a ‘tidal disruption’ event,” he said, explaining that means that the enormous gravity of a black hole pulls on one side of the star harder than the other side, creating tides that rip the star apart.

    “A star wanders near a black hole, the star’s side nearer the black hole is pulled” on more than the star’s far side, he said. “These especially large tides can be strong enough that you pull the star out into a noodle” shape.

    The star “doesn’t fall directly into the black hole,” Wheeler said. “It might form a disk first. But the black hole is destined to swallow most of that material.”

    Though astronomers have seen black holes swallow stars before — though less than a dozen times — this one is special even in that rare company: It’s not going down easy.

    Models by team members James Guillochon of Harvard and Enrico Ramirez-Ruiz at the University of California, Santa Cruz, showed that the disrupted stellar matter was generating so much radiation that it pushed back on the infall. The black hole was choking on the rapidly infalling matter.

    Based on the characteristics of the light from Dougie, and their deductions of the star’s original mass, the team has determined that Dougie started out as a Sun-like star, before being ripped apart.

    Their observations of the host galaxy, coupled with Dougie’s behavior, led them to surmise that the galaxy’s central black hole has the “rather modest” mass of about a million Suns, Wheeler said.

    Delving into Dougie’s behavior has unexpectedly resulted in learning more about small, distant galaxies, Wheeler said, musing “Who knew this little guy had a black hole?”

    The paper’s lead author, Jozsef Vinko, began the project while on sabbatical at The University of Texas at Austin. The team also includes Robert Quimby of San Diego State University, who started the search for supernovae using ROTSE IIIb (then called the Texas Supernova Search, now RSVP) and discovered the category of superluminous supernovae while a graduate student at The University of Texas at Austin.

    See the full article here.

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    McDonald Observatory Campus

    Telescopes Are Windows To the Universe

    Astronomers use them to study everything from the asteroids and planets in our own solar system to galaxies billions of light-years away in space and time. Though they bring the mysteries of the universe to us, their workings are anything but mysterious. They gather and focus light from objects in the sky, so that it can be directed into an instrument attached to the telescope, and ultimately, studied in detail by a scientist. At McDonald Observatory, we have several telescopes, built at various times since the Observatory’s founding in the 1930s.

    Here is an introduction to the telescopes that McDonald Observatory astronomers use for their research:

    McDonald Observatory Hobby-Eberly Telescope
    Hobby-Eberly Telescope

    McDonald Observatory Harlan J Smith Telescope
    Harlan J. Smith Telescope

    McDonald Observatory Otto Struve telescope
    Otto Struve Telescope

    McDonald Observatory .8 meter telescope
    0.8-meter Telescope

    McDonald Observatory .9 meter telescope
    0.9-meter Telescope

    McDonald Observatory Rebecca Gale  Telescope Park
    Rebecca Gale Telescope Park

     
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