How do you observe that the Universe is expanding?
In 2011, the Nobel Prize in Physics was awarded to Saul Perlmutter, Brian Schmidt and Adam Riess for discovering that the Universe is expanding at an accelerating rate. We’d known for a while that the Universe has been expanding ever since its birth - but we didn’t know whether the expansion was slowing down, staying the same, or speeding up.
So, how exactly do you discover something like this?
Perlmutter, Schmidt, and Riess did it by observing a special type of supernovae: Type Ia supernovae. Supernovae are the explosive deaths of large stars, and they usually occur when a star runs out of fuel and collapses under its own weight, generating a shockwave that blasts its material out into space. However, this only happens when a star is big enough - the initial star has to have a critical, threshold mass, called the Chandrasekhar limit. Our sun, for example, won’t go supernova because the Chandrasekhar limit happens to be around 1.4 solar masses. When it runs out of fuel, our sun will instead gently blow off its outer layers and quietly become a dense core of carbon and oxygen, called a white dwarf.
But here’s the kicker: not all white dwarfs stay white dwarfs.
Some white dwarfs exist as one half of a binary system, where two stars orbit each other in a perpetual celestial dance. In some situations, the white dwarfs can actually “steal” matter from their partner star, siphoning it off and guzzling it up to grow more and more massive. Eventually, when their mass hits the Chandrasekhar limit, the white dwarf is ripped apart in a supernova.
Image Credit
This happens in binary systems all across the Universe, and because these white dwarfs all go supernova at exactly the same mass, this means we know exactly how bright the supernovae are. When they’re observed through telescopes, some look brighter and some look fainter depending on their distance - but because we know their actual intrinsic brightness, we can work out how far away they really are. (You could do this yourself using a more earthly standard candle.) For this reason, Type Ia supernovae are called “standard candles”.
In their observations, Perlmutter, Schmidt, and Riess realised that far away supernovae were more redshifted than the supernovae close by. “Redshift” is essentially a measure of how much the Universe has expanded since the light left the supernovae, so by comparing the distance and the redshift of the supernovae, they could create an “expansion history” of the Universe.
This showed pretty clearly that the universe isn’t just expanding, it’s accelerating - i..e, everything’s flying apart more quickly than it was yesterday, or a century, or a billion years ago. Why? Dark energy.
Hi all! Grace here.
I am not yet studying Anatomy and probably won’t until next year, but I decided to look up sources relating to Anatomy and gather them here for future reference! I will be adding more to it as I find more. If you are currently studying Anatomy or already have, please let me know if there were sources you are using/did use that were/are helpful so I can add them! :)
Nurse Journal
Human Body Images
Gross Anatomy
E-Skeleton
Human Anatomy
Introduction to the Human Body
Digestive System: The Inside Story
Body Parts Game
The Immune System
Human Anatomy Learning Modules
The Respiratory System
Anatomy of the Eye
Digestive Disorders and Anatomy
Anatomy Flashcards
Human Anatomy and Physiology
Blood Type Lesson Plan
Introduction to Human Genetics
Anatomy of the Human Brain
Heart Anatomy
Anatomy of the Lungs
NYU Virtual Microscope
Muscle Quizzes
Parts of the Brain
Dermatology Glossary
Interactive Body Games
Anatomical Images
The Bone Box
Muscles of the Body
Anatomy and Physiology Course
Human Body Maps
The Digestive System
Interactive Case Studies
Online Biology Book
Radiographic Anatomy
Body Guide: Skin
Immunity Guide
Anatomy Self-Test
I hope this is helpful! x
The Light Year: Part 3 of 3 (Part 1, Part 2) Episode 5: A Sky Full of Ghosts, Cosmos: A SpaceTime Odyssey
▪︎Copernican armillary sphere.
Date: 1807-1846
Place of origin: Paris
From the source: Copernican armillary sphere from set of two armillary spheres and a celestial globe constructed in paper on pasteboard with metal fitments supported on a decorative mahogany baluster base. Shows planets out to Uranus, plus four asteroids, Ceres, Pallas, Juno & Vesta, first quarter 19th century.
“Since its discovery in 1998, the accelerated expansion has lacked a compelling, simple explanation that didn’t hypothesize a completely new set of forces, properties or interactions. If you wanted a scalar field — a quintessence model — it had to be finely tuned. But in a very clever paper just submitted yesterday by Fergus Simpson, Raul Jimenez, Carlos Pena-Garay, and Licia Verde, they note that if a generic scalar field couples to the neutrinos we have in our Universe, that fine-tuning goes away, and that scalar field will automatically begin behaving as a cosmological constant: as energy inherent to space itself.”
The accelerated expansion of our Universe was one of the biggest surprise discoveries of all-time, and something that still lacks a good physical explanation. While many models of dark energy exist, it remains a completely phenomenological study: everything appears consistent with a cosmological constant, but nothing appears to be a good motivator for why the Universe should have one. Until now, that is! In a new paper by Fergus Simpson, Raul Jimenez, Carlos Pena-Garay and Licia Verde, they note that any generic scalar field that couples to the neutrino sector would dynamically and stably give rise to a type of dark energy that’s indistinguishable from what we’ve observed. The huge advance is that this scenario doesn’t require any fine-tuning, thanks to this dark energy arising from neutrinos “freezing,” or becoming non-relativistic. In addition, there are experimental signatures to look for to confirm it, too, in the form of neutrinoless double-beta decay!
Enzyme-linked immunosorbent assay is a plate-based assay technique used to detect substances such as proteins, peptides and hormones.
An antigen is immobilized on a solid surface
It is complexed with an antibody that is linked to an enzyme.
The conjugated enzyme activity is assessed via incubation with a substrate.
Which produces a product that can be measured.
Antigen is coated directly to wells of microtitre plate
an enzyme-labelled primary antibody that detects the antigen is added.
Advantages
Fast and minimal steps needed.
Minimum precursor requirement makes it less error prone.
Disadvantages
The immobilization of the antigen is not specific - background interference.
Less flexibility of primary antibody.
No signal amplification –> less sensitivity.
An enzyme labelled secondary antibody interacts with a primary antibody to increase sensitivity.
Advantages
Offers high sensitivity and flexibility as a secondary antibody can label different primary antibodies
It is cheap (fewer labelled antibodies needed)
Disadvantages
Increased background noise from the secondary antibody.
Extra labour.
Capture antibody bound to surface.
Antigen-containing sample is applied and captured.
A specific antibody is added, and binds to antigen (sandwiching the antigen between 2 antibodies).
Enzyme-linked secondary antibodies are used as detection antibodies.
Advantages
Offers high sensitivity and a highly specific reaction due to 2 antibodies (both have to bind to the antigen).
Disadvantages
For recognition of a specific epitope, only monoclonal antibodies can be applied as matched pairs.
Procuring monoclonal antibodies is difficult and expensive.
The Carina Nebula - A Birthplace Of Stars
The Carina Nebula lies at an estimated distance of 6,500 to 10,000 light years away from Earth in the constellation Carina. This nebula is one of the most well studied in astrophysics and has a high rate of star formation. The star-burst in the Carina region started around three million years ago when the nebula’s first generation of newborn stars condensed and ignited in the middle of a huge cloud of cold molecular hydrogen. Radiation from these stars carved out an expanding bubble of hot gas. The island-like clumps of dark clouds scattered across the nebula are nodules of dust and gas that are resisting being eaten away by photons (particles of light) that are ionizing the surrounding gas (giving it an electrical charge).
Credit: NASA/Hubble
ESO - European Southern Observatory logo. 24 February 2016
The southern plane of the Milky Way from the ATLASGAL survey
A spectacular new image of the Milky Way has been released to mark the completion of the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The APEX telescope in Chile has mapped the full area of the Galactic Plane visible from the southern hemisphere for the first time at submillimetre wavelengths — between infrared light and radio waves — and in finer detail than recent space-based surveys. The pioneering 12-metre APEX telescope allows astronomers to study the cold Universe: gas and dust only a few tens of degrees above absolute zero. APEX, the Atacama Pathfinder EXperiment telescope, is located at 5100 metres above sea level on the Chajnantor Plateau in Chile’s Atacama region. The ATLASGAL survey took advantage of the unique characteristics of the telescope to provide a detailed view of the distribution of cold dense gas along the plane of the Milky Way galaxy [1]. The new image includes most of the regions of star formation in the southern Milky Way [2].
The southern plane of the Milky Way from the ATLASGAL survey
The new ATLASGAL maps cover an area of sky 140 degrees long and 3 degrees wide, more than four times larger than the first ATLASGAL release [3]. The new maps are also of higher quality, as some areas were re-observed to obtain a more uniform data quality over the whole survey area. The ATLASGAL survey is the single most successful APEX large programme with nearly 70 associated science papers already published, and its legacy will expand much further with all the reduced data products now available to the full astronomical community [4].
The southern plane of the Milky Way from the ATLASGAL survey (annotated)
At the heart of APEX are its sensitive instruments. One of these, LABOCA (the LArge BOlometer Camera) was used for the ATLASGAL survey. LABOCA measures incoming radiation by registering the tiny rise in temperature it causes on its detectors and can detect emission from the cold dark dust bands obscuring the stellar light. The new release of ATLASGAL complements observations from ESA’s Planck satellite [5]. The combination of the Planck and APEX data allowed astronomers to detect emission spread over a larger area of sky and to estimate from it the fraction of dense gas in the inner Galaxy. The ATLASGAL data were also used to create a complete census of cold and massive clouds where new generations of stars are forming.
Comparison of the central part of the Milky Way at different wavelengths
“ATLASGAL provides exciting insights into where the next generation of high-mass stars and clusters form. By combining these with observations from Planck, we can now obtain a link to the large-scale structures of giant molecular clouds,” remarks Timea Csengeri from the Max Planck Institute for Radio Astronomy (MPIfR), Bonn, Germany, who led the work of combining the APEX and Planck data.
Comparison of the central part of the Milky Way at different wavelengths (annotated)
The APEX telescope recently celebrated ten years of successful research on the cold Universe. It plays an important role not only as pathfinder, but also as a complementary facility to ALMA, the Atacama Large Millimeter/submillimeter Array, which is also located on the Chajnantor Plateau. APEX is based on a prototype antenna constructed for the ALMA project, and it has found many targets that ALMA can study in great detail.
Comparison of the central part of the Milky Way at different wavelengths
Leonardo Testi from ESO, who is a member of the ATLASGAL team and the European Project Scientist for the ALMA project, concludes: “ATLASGAL has allowed us to have a new and transformational look at the dense interstellar medium of our own galaxy, the Milky Way. The new release of the full survey opens up the possibility to mine this marvellous dataset for new discoveries. Many teams of scientists are already using the ATLASGAL data to plan for detailed ALMA follow-up.”
Close look at the ATLASGAL image of the plane of the Milky Way
Notes: [1] The map was constructed from individual APEX observations of radiation with a wavelength of 870 µm (0.87 millimetres). [2] The northern part of the Milky Way had already been mapped by the James Clerk Maxwell Telescope (JCMT) and other telescopes, but the southern sky is particularly important as it includes the Galactic Centre, and because it is accessible for detailed follow-up observations with ALMA. [3] The first data release covered an area of approximately 95 square degrees, a very long and narrow strip along the Galactic Plane two degrees wide and over 40 degrees long. The final maps now cover 420 square degrees, more than four times larger. [4] The data products are available through the ESO archive: http://archive.eso.org/wdb/wdb/adp/phase3_main/form?phase3_collection=ATLASGAL&release_tag=1 [5] The Planck data cover the full sky, but with poor spatial resolution. ATLASGAL covers only the Galactic plane, but with high angular resolution. Combining both provides excellent spatial dynamic range. More information: ATLASGAL is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Max Planck Institute for Astronomy (MPIA), ESO, and the University of Chile. APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. Operation of APEX at Chajnantor is carried out by ESO. ALMA is a partnership of the ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”. Links: The ATLASGAL survey: http://www3.mpifr-bonn.mpg.de/div/atlasgal/index.html LABOCA (the LArge BOlometer Camera) : https://www.eso.org/public/teles-instr/apex/laboca/ Max-Planck-Institute for Radio Astronomy (MPIfR): http://www.mpifr-bonn.mpg.de/2169/en Onsala Space Observatory (OSO): http://www.chalmers.se/en/centres/oso/Pages/default.aspx ATLASGAL information at MPIfR: http://www3.mpifr-bonn.mpg.de/div/atlasgal/index.html The Csengeri et al. 2016 paper on the combination with Planck data: http://esoads.eso.org/abs/2016A%26A…585A.104C ATLASGAL papers linked in the ESO Telescope Bibliography: http://telbib.eso.org/?q=atlasgal&boolany=or&boolaut=or&boolti=or&yearto=2016&boolins=or&booltel=or&search=Search ESA’s Planck satellite: http://www.esa.int/Our_Activities/Space_Science/Planck_overview Related article: First ATLASGAL release: https://www.eso.org/public/news/eso0924/ Images, Text, Credits: ESO/APEX/ATLASGAL consortium/NASA/GLIMPSE consortium/ESA/Planck/D. Minniti/S. GuisardAcknowledgement: Ignacio Toledo, Martin Kornmesser/Videos: ESO/APEX/ATLASGAL consortium/NASA/GLIMPSE consortium/ESA/Planck/VVV Survey/D. Minniti/S. Guisard/Acknowledgement: Ignacio Toledo, Martin Kornmesser. Music: Johan B. Monell (www.johanmonell.com). Best regards, Orbiter.ch Full article
The circulatory system: dissection of the stomach and intestines, with the arteries and veins indicated in red and blue. Coloured lithograph by Joseph Maclise, 1841/1844.
This is a studyblr for everyone have some passion for science, especially astronomy and biology
129 posts