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  • richardmitnick 10:02 am on September 11, 2019 Permalink | Reply
    Tags: "All comets in the solar system might come from the same place", , , , , , Leiden University,   

    From Universiteit Leiden via phys.org: “All comets in the solar system might come from the same place” 


    From Universiteit Leiden

    via


    phys.org

    September 9, 2019
    Bryce Benda

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    (NASA/W. Liller)

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    This single frame Rosetta navigation camera image of Comet 67P/Churyumov-Gerasimenko was taken on 7 July 2015 from a distance of 154 km from the comet centre. Credit: ESA/Rosetta/NAVCAM

    A team of American and European scientists found that 14 different comets originated at the same time and place: a protoplanetary disk orbiting near our newly-formed Sun.

    All comets might share their place of birth, new research says. For the first time ever, astronomer Christian Eistrup applied chemical models to fourteen well-known comets, surprisingly finding a clear pattern. His publication has been accepted in the journal Astronomy & Astrophysics.

    Given that comet impacts are thought to be a potential source of organic materials on Earth, exploring this new cosmic origin story could lead to a better understanding of the origin of life.

    This particular survey of 14 comets is too small in scale to use as evidence that all comets came from the same time and place in the early Solar System.

    But it is an interesting starting point for future research, given that the researchers didn’t expect to find so much in common among their samples in the first place.

    Comets: balls of ice or more?

    Comets travel through our solar system and are composed of ice, dust, and small rock-like particles. Their nuclei can be as large as tens of kilometers across. “Comets are everywhere, and sometimes with very funky orbits around the Sun. In the past, comets even have hit the Earth,” Christian Eistrup says. “We know what comets consist of and which molecules are present in them. They vary in composition, but are normally seen as just one group of icy balls. Therefore, I wanted to know whether comets are indeed one group, or whether different subsets can be made.”

    A new take on comets

    “What if I apply our existing chemical models to comets?”, Eistrup thought during his Ph.D. at Leiden University. In the research team at Leiden Observatory, which included Kavli Prize winner Ewine van Dishoeck, he developed models to predict the chemical composition of protoplanetary discs—flat discs of gas and dust encompassing young stars. Understanding these discs can give insight into how stars and planets form. Conveniently, these Leiden models turned out to be of help in learning about comets and their origins.

    “I thought it would be interesting to compare our chemical models with published data on comets,” says the astronomer. “Luckily, I had the help of Ewine. We did some statistics to pin down if there was a special time or place in our young solar system, where our chemical models meet the data on comets.” This happened to be the case, and to a surprising extent. Where the researchers hoped for a number of comets sharing similarities, it turned out that all fourteen comets showed the same trend. “There was a single model that fitted each comet best, thereby indicating that they share their origin.”


    Credit: Leiden University

    Ice-cold

    And that origin is somewhere close to our young Sun, when it was still encircled by a protoplanetary disc and our planets were still forming. The model suggests a zone around the Sun, inside the range where carbon monoxide becomes ice—relatively far away from the nucleus of the young Sun. “At these locations, the temperature varies from 21 to 28 Kelvin, which is around minus 250 degrees Celsius. That’s very cold, so cold that almost all the molecules we know are ice.

    “From our models, we know that there are some reactions taking place in the ice phase—although very slowly, in a time-frame of 100,000 to 1 million years. But that could explain why there are different comets with different compositions.”

    But if comets come from the same place, how do they end up in different places and orbits in our solar system? “Although we now think they formed in similar locations around the young Sun, the orbits of some of these comets could be disturbed—for instance by Jupiter—which explains the different orbits.”

    Comet data hunter

    As befits a scientist, Eistrup places some side-notes to his publication. “With only fourteen comets, the sample is quite small. That’s why I’m currently hunting for data on many more comets, to run them through our models and further test our hypothesis.” Eistrup also hopes that astronomers that study the origin of our solar system and its evolution can use his results. “Our research suggests that comets have formed during the period they’re studying, so this new information might give them new insights.”

    He is also keen to get in touch with other comet researchers. “Because we show a new trend, I would like to discuss what other astronomers think of our research.”

    The seeds of life

    Comets and life on Earth, they go hand in hand. “We still don’t know how life on Earth began. But the chemistry on comets could lead to the production of organic molecules, including some building blocks for life. And if the right comet hits the right planet, with the right environment, life could start growing,” Eistrup concludes. So, interestingly, understanding the birth of comets potentially could help us understand the birth of life on Earth.

    See the full article here.

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    Universiteit Leiden Heijmans onderhoudt

    Universiteit Leiden was founded in 1575 and is one of Europe’s leading international research universities. It has seven faculties in the arts, sciences and social sciences, spread over locations in Leiden and The Hague. The University has over 6,500 staff members and 26,900 students. The motto of the University is ‘Praesidium Libertatis’ – Bastion of Freedom.

     
  • richardmitnick 1:28 pm on July 10, 2017 Permalink | Reply
    Tags: , , , , , , IAC80 and SONG telescopes, , , Leiden University, NITES   

    From astrobites: “Finding the Brightest Exoplanet Hosts with MASCARA” 

    Astrobites bloc

    Astrobites

    Title: MASCARA-2 b: A hot Jupiter transiting a mV=7.6 A-star
    Authors: G.J.J. Talens, A. B. Justesen, S. Albrecht, et al.
    First Author’s Institution: Leiden Observatory, Leiden University, the Netherlands

    Leiden Observatory


    Status: Submitted to A&A, open access

    Before we start: the system discussed in this astrobite was discovered separately by two teams and presented simultaneously. The other paper, by the KELT team, can be found here. This astrobite will focus on the results of the MASCARA team.


    The MASCARA instrument on La Palma

    Kelt North Telescope In Arizona at Winer Observatory by Ohio State University

    KELT South robotic telescope, Southerland, South Africa

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    Figure 1: The Leiden MASCARA instrument on La Palma. Source: http://mascara.strw.leidenuniv.nl/technical/

    It’s clear that there are a lot of exoplanets out there. While large surveys like K2 continue to bring in hundreds of new planets, other projects are filling in the gaps that these surveys miss.

    NASA/Kepler Telescope

    The relatively new project MASCARA intends to find planets around the brightest host stars yet. They are targeting stars with magnitudes less than 8.4 (remember that fainter stars have higher magnitudes). For comparison, that’s still fainter than the human eye can see (magnitude 6 or less), but it’s a fair bit brighter than the Kepler space telescope can see (Kepler saturates on stars brighter than about 11th magnitude). There are currently only 14 exoplanet host stars known that are brighter than 8.4th magnitude, with the brightest being KELT-9 at a magnitude of 7.56. These exoplanets around bright stars are interesting because it’s so much easier to do follow-up observations on them. In particular, in-depth studies of exoplanet atmospheres — which require collecting starlight that has passed through the exoplanet atmosphere, and studying how the atmosphere has affected the starlight — are much easier when the exoplanet orbits bright stars like these, simply because there are so many more photons that reach us.

    The MASCARA team operate a station at the La Palma observatory in Spain, observing the northern sky. Like many astronomical acronyms, MASCARA takes a bit of imagination: it stands for the Multi-site All-Sky CAmeRA. The station consists of five cameras, one each pointing North, South, East and West, and the fifth pointing straight up. Between them they can cover the whole visible sky. The cameras remain motionless while the stars pass overhead. Like Kepler, MASCARA is looking for exoplanet transits — the dip in a star’s light that means a planet is passing between us and the star. To do this, they take a series of six-second images with each camera. By identifying the same stars between images, and taking into account any atmospheric effects such as passing clouds, they can search each star for dips in brightness that might be exoplanet transits.

    Planet transit. NASA/Ames

    MASCARA-2b [No image available]

    MASCARA-2b is the second exoplanet to be discovered by this method, but the first to be published (MASCARA-1b is also in the works, but 2b was pushed ahead in the queue because of a simultaneous discovery by another team). From the MASCARA data in Figure 2, a clear transit can be seen every 3.47 days. To follow this up, the team observed transits with the NITES, IAC80 and SONG telescopes.

    6
    Near Infra-red Transiting ExoplanetS (NITES) telescope is 0.4-m semi-robotic telescope located at El Observatorio del Roque de los Muchachos (ORM) on La Palma in the Canary Islands

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    The IAC 80 telescope of the Observatorio del Teide.

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    Danish led SONG telescope i the Canary Islands, Spain.

    To emphasise how bright this star is compared to the usual astronomical targets: these are small telescopes — NITES in particular is only 40cm in diameter. Even these telescopes however had to be kept deliberately out-of-focus, blurring the resulting image and spreading the star’s light over more pixels, because otherwise there would be a danger of saturating the image. This practise is not uncommon for larger telescopes, but it’s surprising to see it necessary on these rather smaller telescopes.

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    Figure 2: Searching for strong periods in the MASCARA data (top) and then wrapping data around on that period to see the transit shape (bottom). This is Figure 1 in today’s paper.

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    Figure 3: Transits observed with MASCARA (top), NITES (middle) and IAC80 (bottom). Source: Figure 2 in today’s paper.

    The host star has a magnitude of 7.58, narrowly missing the record. It’s also an A-type star, towards the hotter end of the spectrum, and as such the star spins on its axis faster than the average star does. Generally fast rotation makes spectroscopic measurements difficult, as the difference Doppler shift between opposite sides of the star smears out the spectral lines that we’re interested in. Aided by the system’s brightness, however, the team were able to obtain spectra that were high-enough quality to overcome this difficulty. They found that the planet is a hot Jupiter, orbiting at around 6% of the Earth-Sun separation, and that it has a radius around double that of Jupiter itself. They also found that the planet’s orbit is quite well aligned with the direction that the star spins — this is unusual for hot Jupiters in systems like this, which generally seem to orbit with a slight tilt. The team hope that the system is well-placed for follow-up studies of the planet’s atmosphere, adding to the fairly small pool of planets in which such studies are possible.

    The MASCARA team is currently building a second MASCARA instrument in Chile, where it will be able to explore the southern sky — at present, only two of the fourteen brightest exoplanet hosts are southern. This same planet was simultaneously discovered by KELT, another project exploring the same types of stars. This is a growing area of exoplanet research, so look for further interesting results in the future!

    To emphasise how bright this star is compared to the usual astronomical targets: these are small telescopes — NITES in particular is only 40cm in diameter. Even these telescopes however had to be kept deliberately out-of-focus, blurring the resulting image and spreading the star’s light over more pixels, because otherwise there would be a danger of saturating the image. This practise is not uncommon for larger telescopes, but it’s surprising to see it necessary on these rather smaller telescopes.

    See the full article here .

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    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 7:20 am on June 22, 2016 Permalink | Reply
    Tags: , Leiden University, , Second layer of information hidden in our DNA   

    From Science Alert: “Physicists confirm there’s a second layer of information hidden in our DNA 

    ScienceAlert

    Science Alert

    9 JUN 2016
    FIONA MACDONALD

    1
    Liya Graphics/Shutterstock.com

    Theoretical physicists have confirmed that it’s not just the information coded into our DNA that shapes who we are – it’s also the way DNA folds itself that controls which genes are expressed inside our bodies.

    That’s something biologists have known for years, and they’ve even been able to figure out some of the proteins responsible for folding up DNA. But now a group of physicists have been able to demonstrate for the first time through simulations how this hidden information controls our evolution.

    Let’s back up for a second here, because although it’s not necessarily news to many scientists, this second level of DNA information might not be something you’re familiar with.

    As you probably learnt in high school, Watson and Crick discovered in 1953 the double helix structure of DNA. Since then we’ve learnt that the DNA code that determines who we are is made up of a sequence of the letters G, A, C, and T.

    The order of these letters determines which proteins are made in our cells. So, if you have brown eyes, it’s because your DNA contains a particular series of letters that encodes for a protein that makes the dark pigment inside your iris.

    But that’s not the whole story, because all the cells in your body start out with the exact same DNA code, but every organ has a very different function – your stomach cells don’t need to produce the brown eye protein, but they do need to produce digestive enzymes. So how does that work?

    Since the ’80s, scientists have found that the way DNA is folded up inside our cells actually controls this process. Environmental factors can play a big role in this process too, with things like stress known to turn certain genes on and off through something known as epigenetics.

    But the mechanics of the DNA folding is an incredibly important control mechanism. That’s because every single cell in our body contains around 2 metres of DNA, so to fit inside us, it has to be tightly wrapped up into a bundle called a nucleosome – like a thread around a spool.

    And the way the DNA is wrapped up controls which genes are ‘read’ by the rest of the cell – genes that are all wrapped on the inside won’t be expressed as proteins, but those on the outside will. This explains why different cells have the same DNA but different functions.

    In recent years, biologists have even started to isolate the mechanical cues that determine the way DNA is folded, by ‘grabbing onto’ certain parts of the genetic code or changing the shape of the ‘spool’ the DNA is wrapped around.

    So far, so good, but what do theoretical physicists have to do with all this?

    A team from Leiden University in the Netherlands has now been able to step back and look at the process on a whole-genome scale, and back up through computer simulations that these mechanical cues are actually coded into our DNA.

    The physicists, led by Helmut Schiessel, did this by simulating the genomes of both baker’s yeast and fission yeast, and then randomly assigning them a second level of DNA information, complete with mechanical cues.

    They were able to show that these cues affected how the DNA was folded and which proteins are expressed – further evidence that the mechanics of DNA are written into our DNA, and they’re just as important in our evolution as the code itself.

    This means the researchers have shown that there’s more than one way that DNA mutations can affect us: by changing the letters in our DNA, or simply by changing the mechanical cues that arrange the way a strand is folded.

    “The mechanics of the DNA structure can change, resulting in different packaging and levels of DNA accessibility,” they explain, “and therefore differing frequency of production of that protein.”

    Again, this is simply backing up what many biologists already knew, but what’s really exciting from a purely speculative point of view is the fact that the computer simulations open up the possibility for scientists to model and maybe one day even manipulate the mechanical cues that shape our genetic code.

    There’s no evidence that we can do that just yet, but what we do know is that the more scientists understand about how our DNA is controlled and folded, the closer we get to being able to improve upon it.

    The research has been published in PLOS ONE.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
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