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ESA’s XMM-Newton X-ray observatory has spied hot gas sloshing around within a galaxy cluster – a never-before-seen behaviour that may be driven by turbulent merger events.
Galaxy clusters are the largest systems in the Universe bound together by gravity. They contain hundreds to thousands of galaxies and large quantities of hot gas known as plasma, which reaches temperatures of around 50 million degrees and shines brightly in X-rays.
Very little is known about how this plasma moves, but exploring its motions may be key to understanding how galaxy clusters form, evolve and behave.
“We selected two nearby, massive, bright and well-observed galaxy clusters, Perseus and Coma, and mapped how their plasma moved – whether it was moving towards or away from us, its speed, and so on – for the first time,” says Jeremy Sanders of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and lead author of the new study.
“We did this over large regions of sky: an area roughly the size of two full Moons for Perseus, and four for Coma. We really needed XMM-Newton for this, as it’d be extremely difficult to cover such large areas with any other spacecraft.”
Jeremy and colleagues found direct signs of plasma flowing, splashing and sloshing around within the Perseus galaxy cluster – one of the most massive known objects in the Universe, and the brightest cluster in the sky in terms of X-rays. While this kind of motion has been predicted theoretically, it had never been seen before in the cosmos.
By looking at simulations of how the plasma moved within the cluster, the researchers then explored what was causing the sloshing. They found it to be likely due to smaller sub-clusters of galaxies colliding and merging with the main cluster itself. These events are energetic enough to disrupt Perseus’ gravitational field and kickstart a sloshing motion that will last for many millions of years before settling.
Unlike Perseus, which is characterised by a main cluster and several smaller sub-structures, the Coma cluster contained no sloshing plasma, and appears to instead be a massive cluster made up of two major sub-clusters that are slowly merging together.
“Coma contains two massive central galaxies rather than a cluster’s usual single behemoth, and different regions appear to contain material that moves differently,” says Jeremy.
“This indicates that there are multiple streams of material within the Coma cluster that haven’t yet come together to form a single coherent ‘blob’, like we see with Perseus.”
The finding was made possible by a new calibration technique applied to XMM-Newton’s European Photon Imaging Camera (EPIC). The ingenious method, which involved mining two decades of archival EPIC data, improved the accuracy of the camera’s velocity measurements by a factor of over 3.5, raising XMM-Newton’s capabilities to a new level.
“The EPIC camera has an instrumental background signal – the so-called ‘fluorescent lines’ which are always present in our data, and can sometimes be annoying as they’re usually not what we’re looking for,” adds co-author Ciro Pinto, an ESA research fellow at the European Space Research and Technology Centre in Noordwijk, The Netherlands, who recently moved to Italy’s National Institute for Astrophysics.
“We decided to use these lines, which are a constant feature, to compare and align EPIC data from the past 20 years to better determine how the camera behaves, and then used this to correct for any instrumental variation or effects.”
This technique made it possible to map the gas in the clusters more accurately. Jeremy, Ciro and colleagues used the background lines to recognise and remove individual variations between observations, and then eliminated any subtler instrumental effects identified and flagged up by their 20 years of EPIC data mining.
EPIC comprises three CCD cameras designed to capture both low- and high-energy X-rays, and is one of a trio of advanced instruments aboard XMM-Newton.
Exploring the dynamic X-ray sky since its launch in 1999, XMM-Newton is the biggest scientific satellite ever built in Europe, and carries some of the most powerful telescope mirrors ever developed.
“This calibration technique highlights newfound capabilities of the EPIC camera,” says Norbert Schartel, ESA XMM-Newton Project Scientist.
“High-energy astrophysics often entails comparing X-ray data at different points in the cosmos for everything from plasma to black holes, so the ability to minimise instrumental effects is key. By using past XMM-Newton observations to refine future ones, the new technique may open up inspiring opportunities for new research and discovery.”
These XMM-Newton observations will also remain unparalleled until the launch of ESA’s Advanced Telescope for High-ENergy Astrophysics (Athena) in 2031. Whereas covering such large areas of sky will largely be beyond the capabilities of telescopes such as the upcoming JAXA/NASA X-ray Imaging and Spectroscopy Mission, or XRISM, Athena will combine a large X-ray telescope with state-of-the-art scientific instruments to shed new light on the hot, energetic Universe.
Notes for editors
"Measuring bulk flows of the intracluster medium in the Perseus and Coma galaxy clusters using XMM-Newton" by J. S. Sanders et al. is published in Astronomy & Astrophysics.
The study uses X-ray observations from XMM-Newton’s European Photon Imaging Camera (EPIC), and data from JAXA’s Hitomi satellite for comparison and elements of calibration.
For more information, please contact:
Max Planck Institute for Extraterrestrial Physics
European Space Agency
European Space Research and Technology Centre
Noordwijk, The Netherlands
Institute of Space Astrophysics and Cosmic Physics (IASF)
National Institute for Astrophysics (INAF)
XMM-Newton project scientist
European Space Agency | 0.890251 | 4.098135 |
It's called Apophis. It's 390m wide. And it could hit Earth in 31 years time. A meteorite on a collision course with planet earth. When it hits the earth atmosphere and moments later the surface it will make a hell of show and that is a very big understatement.
In Egyptian myth, Apophis was the ancient spirit of evil and destruction, a demon that was determined to plunge the world into eternal darkness. And this Apophis could very well do the same thing. Nasa has estimated that an impact from Apophis, which has an outside chance of hitting the Earth in 2036, would release more than 100,000 times the energy released in the nuclear blast over Hiroshima. Thousands of square kilometres would be directly affected by the blast but the whole of the Earth would see the effects of the dust released into the atmosphere.
And, scientists insist, there is actually very little time left to decide. At a recent meeting of experts in near-Earth objects (NEOs) in London, scientists said it could take decades to design, test and build the required technology to deflect the asteroid. Monica Grady, an expert in meteorites at the Open University, said: "It's a question of when, not if, a near Earth object collides with Earth. Many of the smaller objects break up when they reach the Earth's atmosphere and have no impact. However, a NEO larger than 1km [wide] will collide with Earth every few hundred thousand years and a NEO larger than 6km, which could cause mass extinction, will collide with Earth every hundred million years. We are overdue for a big one."
Apophis had been intermittently tracked since its discovery in June last year but, in December, it started causing serious concern. Projecting the orbit of the asteroid into the future, astronomers had calculated that the odds of it hitting the Earth in 2029 were alarming. As more observations came in, the odds got higher.
Having more than 20 years warning of potential impact might seem plenty of time. But, at last week's meeting, Andrea Carusi, president of the Spaceguard Foundation, said that the time for governments to make decisions on what to do was now, to give scientists time to prepare mitigation missions. At the peak of concern, Apophis asteroid was placed at four out of 10 on the Torino scale - a measure of the threat posed by an NEO where 10 is a certain collision which could cause a global catastrophe. This was the highest of any asteroid in recorded history and it had a 1 in 37 chance of hitting the Earth. The threat of a collision in 2029 was eventually ruled out at the end of last year.
Alan Fitzsimmons, an astronomer from Queen's University Belfast, said: "When it does pass close to us on April 13 2029, the Earth will deflect it and change its orbit. There's a small possibility that if it passes through a particular point in space, the so-called keyhole, ... the Earth's gravity will change things so that when it comes back around again in 2036, it will collide with us." The chance of Apophis passing through the keyhole, a 600-metre patch of space, is 1 in 5,500 based on current information.
There are no shortage of ideas on how to deflect asteroids. The Advanced Concepts Team at the European Space Agency have led the effort in designing a range of satellites and rockets to nudge asteroids on a collision course for Earth into a different orbit.
No technology has been left unconsidered, even potentially dangerous ideas such as nuclear powered spacecraft. "The advantage of nuclear propulsion is a lot of power," said Prof Fitzsimmons. "The negative thing is that ... we haven't done it yet. Whereas with solar electric propulsion, there are several spacecraft now that do use this technology so we're fairly confident it would work."
The favoured method is also potentially the easiest - throwing a spacecraft at an asteroid to change its direction. Esa plans to test this idea with its Don Quixote mission, where two satellites will be sent to an asteroid. One of them, Hidalgo, will collide with the asteroid at high speed while the other, Sancho, will measure the change in the object's orbit. Decisions on the actual design of these probes will be made in the coming months, with launch expected some time in the next decade. One idea that seems to have no support from astronomers is the use of explosives.
Prof Fitzsimmons. "If you explode too close to impact, perhaps you'll get hit by several fragments rather than one, so you spread out the area of damage."
In September, scientists at Strathclyde and Glasgow universities began computer simulations to work out the feasibility of changing the directions of asteroids on a collision course for Earth. In spring next year, there will be another opportunity for radar observations of Apophis that will help astronomers work out possible future orbits of the asteroid more accurately.
If, at that stage, they cannot rule out an impact with Earth in 2036, the next chance to make better observations will not be until 2013. Nasa has argued that a final decision on what to do about Apophis will have to be made at that stage.
"It may be a decision in 2013 whether or not to go ahead with a full-blown mitigation mission, but we need to start planning it before 2013," said Prof Fitzsimmons. In 2029, astronomers will know for sure if Apophis will pose a threat in 2036. If the worst-case scenarios turn out to be true and the Earth is not prepared, it will be too late. "If we wait until 2029, it would seem unlikely that you'd be able to do anything about 2036," said Mr Yates. | 0.820906 | 3.049654 |
Marshall Space Flight Center's Astrophysics Branch uses space and ground-based observatories to peer back to the earliest epochs of the universe, unravel its mysteries, and study the most violent explosions in our galaxy and beyond. Our goal is to help discover how the universe works, explore how it began and evolved, and search for life on planets around other stars.
LIGO-VIRGO Announce New Type of Binary Black Hole Merger
Tyson Littenberg (Astrophysics Branch) is part of the LIGO Scientific Collaboration team that announced the discovery of a new type of binary black hole: GW190412. The signal was recorded on April 12, 2019 during the first month of LIGO-Virgo’s third observing run (O3). GW190412 is a unique event in that the constituent black holes that merged were of very different mass – a ~30 solar mass black hole merging with a ~8 solar mass black hole. All black hole mergers observed previously were consistent with equal mass binaries. Asymmetric mass binaries were predicted to emit gravitational waves at higher-order multipoles of the dominant quadrupole signal. Tests performed on the GW190412 observation unambiguously show the presence of higher order components to the gravitational wave signal consistent with the predictions from Einstein’s general theory of relativity, and marks the first time this phenomena has been observed. GW190412 is only the second O3 event to be published (following the binary neutron star observation GW190425) with dozens of additional candidates going through the LIGO-Virgo vetting process.
The paper and associated data are publicly available for download at https://dcc.ligo.org/LIGO-P190412/public and is accompanied by a numerical relativity simulation of the system viewable at https://www.youtube.com/watch?v=5AkT4bPk-00.
MoonBEAM Proposal Selected for Astrophysics Science SmallSat Studies Program
The “MoonBEAM: A Beyond Earth-orbit Gamma-ray Burst Detector for Multi-Messenger Astronomy” proposal has been selected for a concept study by the Astrophysics Science SmallSat Studies (AS3) program. MoonBeam was submitted in response to NASA’s Research Opportunities in Space Science and is led by ST12’s Michelle Hui. The Marshall Space Flight Center Advanced Concept Office will conduct the mission design study together with the science team.
MoonBEAM is a SmallSat concept of deploying gamma-ray detectors in cislunar space to increase gamma-ray burst detections and improve localization precision with the timing triangulation technique. Such an instrument will probe the extreme processes involved in the cosmic collision of compact objects and facilitate multi-messenger time-domain astronomy to explore the end of stellar life cycles and black hole formation. MoonBEAM’s mission goals are to 1.) detect short gamma-ray bursts associated with gravitational wave events to study astrophysical jets and probe fundamental physics from neutron star merger events, and 2.) improve localization to enable faster afterglow detection to study kilonova evolution and the origin of heavy elements.
MoonBEAM’s in-house science instrument consists of five detector modules, each equipped with phoswiches and silicon photomultipliers positioned on five of the six sides of the instrument to maximize sky coverage. MoonBEAM’s mission is planned for two years (with a one year minimum) and one of the suitable orbits is the cislunar L3 halo orbit of the Earth-Moon system (95,000 – 665,000 km from Earth, 0.3-2.1 light-seconds difference). Based on the sky coverage and duty cycle at Earth-Moon L3 orbit and detector area, MoonBEAM will detect 30-70 short GRBs/year with onboard detection algorithms, competitive with current missions in operation. Adding another instrument in a different orbit will increase the number of GRB detections and improve localization via arrival time difference.
In the image to the right, the purple region showcases the localization improvement of an average GBM detection by MoonBEAM and an instrument in low Earth orbit.
Paper Detailing Improvement to Fermi Gamma-ray Burst Monitor (GBM) Localizations Accepted for Publication
“Evaluation of Automated Fermi GBM Localizations of Gamma-ray Bursts” led by Adam Goldstein (USRA) was accepted for publication in the Astrophysical Journal. This paper details improvements to automated gamma-ray burst localizations provided to the community within 10 minutes of a burst by the RoboBA algorithm developed by the Fermi GBM team. The overall accuracy of RoboBA localizations has been improved significantly. This paper also compares this algorithm to another developed by an outside team. This analysis of more than 500 gamma-ray bursts with known localizations from other satellites shows that the GBM team provided RoboBA algorithm provides confidence regions more than ten times smaller than those provided by the outside group’s algorithms, once systematic uncertainty is considered for both techniques.
Fermi GBM Publishes Follow-up of First LIGO-VIRGO Event Catalog
The Fermi-GBM follow-up analysis of the first LIGO-Virgo gravitational wave catalog (GWTC-1) was published in the Astrophysical Journal on April 20, 2020. The study was led by UAH graduate student and GBM team member Rachel Hamburg and is a collaboration between the full GBM team and the LIGO and Virgo Collaborations. The analysis included deep offline searches of GBM data around the times of all confident gravitational wave detections to identify any potential counterparts. The GRB associated with the binary neutron star merger in LIGO-Virgo’s second observing run (GW1709817/GRB170817a) was found with high confidence, but no “subthreshold” events were discovered in the search. Based on lessons learned from that analysis, improvements to the GBM follow-up algorithms have been implemented and offline searches of new gravitational wave events are ongoing.
Marshall Scientists Support New Video Series
Multiple Marhsall scientists are supporting the US Space and Rocket Center's (USSRC’s) new video series aimed at 10-14 year-olds called “Science Never Stops”. Videos are posted on Facebook and YouTube. ST12 scientists contributing are Tyson Littenberg, Steven Ehlert, and Colleen Wilson-Hodge.
Chandra Project Science team member, Steven Ehlert, gave an interview as part of this digital series. His interview focused on the science mission of the Chandra X-ray Observatory as well as some personal anecdotes. The edited interview video will be made available on the Space and Rocket Center’s social media pages.
Fermi Gamma-ray Burst Monitor (GBM) Paper in Top 10% of Downloads
The First Fermi-GBM Terrestrial Gamma Ray Flash Catalog led by Oliver Roberts (USRA), was in the top 10% of downloaded papers published between January 2018 and December 2019 by the Journal of Geophysical Research: Space Physics. This paper detailed results from 4,144 terrestrial gamma-flashes (TGFs) detected with Fermi GBM from July 11, 2008 through July 31, 2016. TGFs are gamma-rays associated with lightning in thunderstorms. The detection rate of TGFs was about 800 per year on average, with strong correlations with the seasonal variation of lightning. This study quantitatively showed that TGFs occur preferentially near coastlines.
10-Year Compendium of Accreting Pulsar Observations with the Fermi GBM Accepted for Publication
“The Ups & Downs of Accreting X-ray Pulsars: Decade-long Observations with the Fermi Gamma-ray Burst Monitor” led by NASA Postdoctoral Program Fellow Christian Malacaria (USRA) was accepted for publication in the Astrophysical Journal. This paper details observations of 39 accreting X-ray pulsars from August 2008 through November 2019. Accreting pulsars are highly magnetized neutron stars in binary systems with normal star companions. The neutron star accretes mass from its companion onto its poles, emitting X-rays, periodic with the spin period of the neutron star. Fermi GBM observations are vital to our understanding of these systems, revealing long-term cycles, uncovering torque reversals, and providing new orbital solutions.
Universe's Expansion May Not be the Same in All Directions
One of the fundamental ideas of cosmology is that everything looks the same in all directions if you look over large enough distances. A new study using galaxy clusters examines whether the Universe is "isotropic," or the same in all directions. Galaxy Clusters are enormous structures that astronomers can use to measure important cosmological properties. The latest result uses X-ray data from Chandra and X-ray MultiMirror-Newton (XMM-Newton) of hundreds of galaxy clusters. The cluster observations suggest that the Universe may be different depending on which way astronomers look.
For more information see: https://chandra.harvard.edu/photo/2020/isotropic/
Paper accepted for publication in Planetary and Space Science
Steven Ehlert (Astrophysics Branch) is the lead author on a paper accepted for publication in Planetary and Space Science entitled “Measuring Fluxes of Meteor Showers with the NASA All-Sky Fireball Network”. The manuscript was submitted for publication while Dr. Ehlert was in his previous position supporting the Meteoroid Environment Office in the MSFC Natural Environments Branch (EV44)
Black Hole’s Record-breaking Explosion Spotted
On February 27, 2020, Chandra released a new image and press release of the biggest explosion seen in the Universe that astronomers have discovered – the Ophiuchus galaxy cluster. In the center of the Ophiuchus cluster is a large galaxy containing a supermassive black hole. Researchers have traced the source of this gigantic eruption to jets that blasted away from the black hole and carved out a large cavity in the hot gas. Astronomers obtained this result using data from NASA's Chandra X-ray Observatory, XMM-Newton, and two radio telescopes in Australia and India. The explosion released a factor of five more energy than the previous record holder and hundreds of thousands of times more than typical clusters.
For more information see: https://www.nasa.gov/mission_pages/chandra/images/ophiuchus-galaxy-cluster.html.
Colleen Wilson-Hodge Selected as American Astronomical Society (AAS) Legacy Fellow
The American Astronomical society (AAS) has established a new accolade, Fellow of the AAS, to honor members for extraordinary achievement and service over the course of their careers. Dr. Colleen Wilson-Hodge was selected as one of the initial set of Legacy AAS Fellows. The press release is found here https://aas.org/press/aas-announces-first-class-aas-fellows. After this year, there will be an annual selection for this honor. The list of legacy fellows is found here https://aas.org/grants-and-prizes/aas-fellows.
Chandra Data Tests “Theory of Everything”
Astronomers used Chandra to perform a test of string theory, a possible "theory of everything" that would tie all known physics together. The researchers were looking for a type of particle known as an "axion" and other similar particles. Galaxy clusters with their strong magnetic fields and X-ray emission can be excellent places to search for evidence for axions. The team looked at the Perseus galaxy cluster for over 5 days with Chandra, but did not find signals of any axion-like particles.
For more information see: https://chandra.cfa.harvard.edu/photo/2020/perseus/.
A Cosmic Jekyll and Hyde
On February 20, 2020, Chandra released a new image of Terzan 5 CX1, a globular cluster located about 19,000 light years from the earth that has shown behavior traits of two different types of objects. Chandra data from 2003 show this system acted as a low-mass X-ray binary, with a neutron star pulling material from a star like the Sun. In Chandra and VLA data taken from 2009 to 2014, Terzan 5 CX1 showed the system changed into behaving like a millisecond pulsar, then in 2016 went back to acting like a low-mass X-ray binary. To confirm this pattern of "Jekyll and Hyde" behavior, astronomers need to detect radio pulses while Terzan 5 CX1 is faint in X-rays. More radio and X-ray observations are planned to search for this behavior, along with sensitive searches for pulses in existing data. Only three confirmed examples of these identity-changing systems are known, with the first discovered in 2013 using Chandra and several other X-ray and radio telescopes.
For more information see: https://www.nasa.gov/mission_pages/chandra/cosmic-jekyll-and-hyde.html.
Stellar Explosions and Jets Showcased in New 3D Visualizations
On January 29, 2020, the Chandra team released a new collection of 3D visualizations based on data from Chandra and other X-ray telescopes. This compilation of 3D visualizations which includes DG Tau, Cassiopeia A, UScorpii, SN1006, SN 1987A, and Tycho was created by Salvatore Orlando (National Institute for Astrophysics (INAF), Osservatorio Astronomico di Palermo) and his colleagues. These visualizations can teach astronomers about the physical properties of cosmic objects such as their geometry, velocity, and more. Each of these computer simulations is available using free software that is supported by most platforms and browsers and allows users to interact with and navigate 3D models as they choose.
For more information see: https://www.nasa.gov/mission_pages/chandra/main/index.html.
Large Area Burst Polarimeter (LEAP) Selected for Concept Study
On March 16, 2020, Large Area Burst Polarimeter (LEAP), an Astrophysics Mission of Opportunity (MO), was selected for a nine-month implementation concept study. LEAP is an externally mounted International Space Station (ISS) instrument that will study the energetic jets launched during the explosive death of a massive star, or the merger of compact objects such as neutron stars. The LEAP principal investigator (PI) organization is Dr. Mark McConnell/ University of New Hampshire, the deputy PI responsibility is assigned to Marshall’s ST12 Astrophysics Branch, and the project management responsibility is assigned to Marshall’s ST14 Project Management Branch. The project team held a kickoff meeting on March 18, 2020 to review the Phase A schedule and a kickoff with the Explorer’s Project Office will be held on April 23, 2020. The Phase A study will conclude with the delivery of a concept study report in the December time frame.
Progress on IXPE
Marshall scientists, technicians and partners continue to make process on the Imaging X-ray Polarimetry Explorer (IXPE). Recently, the Italian Instrument Team (I2T) at Marshall completed rework and the vibration test of the Detector Unit 2 (DU2), a highly specialized unit that determine the polarization of incident X-rays. The Italian DU2 is flight hardware contributed for use by the IXPE Project and DU2 property custody was transferred from the Italian Space Agency (ASI) to IXPE (NASA).
Also, the Astrophysics Branch, MSFC Engineering, and IXPE Project has validated margin in the mirror module assembly, MMA2, 9394 epoxy bonds using independent engineering groups and cleared the epoxy process used in the MMA final assembly. The IXPE team is ready to begin proto-type level environmental testing. The MMA2 is flight hardware developed by Marshall Space Flight Center for use by the IXPE Project. Following thermal-vacuum (TVAC) testing this flight unit will undergo acoustic and vibration testing before start of X-ray calibration.
Nicole Pelfrey Selected as Marshall's Astrophysics (ST12) Branch Chief
Nicole Pelfrey received a Bachelor of Science degree in biology from Wofford College in 1998. She began her career in the generic pharmaceutical industry, starting as a compliance auditor, leading a microbiology lab and performing research and development for new products. She spent 8 years performing microbiological and chemical testing of drug products. She also served as the assistant quality control laboratory manager for the seventh largest generic pharmaceutical company in the United States. In 2006, she joined the International Space Station (ISS) Payload Operations Team as a Payloads Communications Manager (PAYCOM), collaborating with the ISS crew to ensure successful on-board science operations. She served as PAYCOM team lead for 6 years before shifting her focus to training and organizational management. She served as the operations engineer for an ISS emerging technology development project, supported multiple technical contract proposal teams, developed training for multiple organizations, and supported the Sierra Nevada Dream Chaser vehicle PDR. Her last two years on the ISS Program were as the Operations Manager for the Mission Operations & Integration contract with approximately 300 contractors, 10 direct reports across 5 branches and 24 disciplines. Ms. Pelfrey joined NASA in 2018 as the Deputy Branch Chief of the Astrophysics Branch and began serving as the acting Branch Chief in May 2019. She was recently selected as the Branch Chief in January 2020 to succeed Dr. Nasser Barghouty, who accepted a NASA Headquarters position.
The Fermi Gamma-ray Burst Monitor Releases 10 Year Catalog of Gamma-ray Burst Observations
The Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope has released its 4th Gamma-ray Burst (GRB) catalog, covering over 10 years of observations. Fermi-GBM has been a prolific detector of GRBs; bright flashes of gamma-rays that originate in the distant Universe and are due to the death of massive stars or the inspiral of two compact stellar remnants. The 4th Fermi-GBM GRB catalog includes 2356 bursts, providing a vast trove of information with which scientist can study these unique events. The GBM GRB catalog series provides the community with the most important observables of the GBM detected GRBs, including the location and main characteristics of the prompt emission, duration, peak flux and fluence for each of the cataloged bursts. This 4th catalog is an official product of the Fermi-GBM science team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center (HEASARC).
The catalog has been accepted to the Astrophysical Journal Supplement Series and will be available on the arXiv pre-print server at the link below.
Galaxy Gathering Brings Warmth
Using NASA’s Chandra X-ray Observatory, European Space Agency's X-ray Multi-Mirror Mission (XMM)-Newton, the Giant Metrewave Radio Telescope (GMRT), and optical observations with the Apache Point Observatory in New Mexico, a team of astronomers has found that two galaxy groups are smashing into each other at a remarkable speed of about 4 million miles per hour. This could be the most violent collision yet seen between two galaxy groups. By studying mergers like this, astronomers can learn more about galaxy groups grow and evolve over time. The system is called NGC 6338, which is located about 380 million light-years from Earth. This composite image contains X-ray data from Chandra (displayed in red) that shows hot gas with temperatures upward of about 20 million degrees Celsius, as well as cooler gas detected with Chandra and XMM (shown in blue) that also emits X-rays. The Chandra data have been combined with optical data from the Sloan Digital Sky Survey, showing the galaxies and stars in white.
The new Chandra and XMM-Newton data also show that the gas to the left and right of the cool cores, and in between them, appears to have been heated by shock fronts -- similar to the sonic booms created by supersonic aircraft -- formed by the collision of the two galaxy groups. This pattern of shock-heated gas has been predicted by computer simulations, but NGC 6338 may be the first merger of galaxy groups to clearly show it. Such heating will prevent some of the hot gas from cooling down to form new stars.
For more information, see: https://www.nasa.gov/mission_pages/chandra/main/index.html.
NASA’s Great Observatories Help Astronomers Build a 3D Visualization of Exploded Star
A Chandra-issued image release on January 5, 2020 combined X-ray, visible and infrared data from NASA's Great Observatories to create a three-dimensional representation of the Crab Nebula. The multiwavelength computer graphics visualization is based on images from the Chandra, Hubble and Spitzer space telescopes. The powerhouse "engine" energizing the entire system is a pulsar, a rapidly spinning neutron star that is shooting blistering pulses of radiation towards us 30 times a second with clockwork precision. A video was created that dissects the intricate nested structure that makes up the stellar corpse, giving viewers a glimpse of the extreme and complex physical processes powering the nebula.
For more information, or to view the video, go to: https://www.nasa.gov/feature/goddard/2019/nasas-great-observatories-help-astronomers-build-a-3d-visualization-of-an-exploded-star.
Black Holes and Baby Stars
On November 18, 2019 Chandra released to the press a featured discovery entitled “A Weakened Black Hole Allows Its Galaxy to Awaken.” The associated image release was featured as the NASA Image of the Day on November 20, 2019. Through this observation of the Phoenix Constellation, astronomers have confirmed the first example of a galaxy cluster where large numbers of stars are being born at its core. More information can be found at the website: https://www.nasa.gov/mission_pages/chandra/images/a-weakened-black-hole-allows-its-galaxy-to-awaken.html.
On November 26, 2019, Chandra released to the press a feature entitled “Black Hole Nurtures Baby Stars a Million Light-Years Away.” The associated image release was featured as the NASA Image of the Day on November 26, 2019. The press release describes one black hole that is influencing the rate of star formation in multiple galaxies and across vast distances. This is a rare example of "positive feedback" where a black hole is helping to spur star formation, not suppress it. Researchers used X-rays from Chandra, radio waves from the VLA, and optical light from ground-based telescopes to make this discovery. If confirmed, this result would represent the largest distance over which a black hole has boosted the birth of stars. More information can be found at the website: https://www.nasa.gov/mission_pages/chandra/images/black-hole-nurtures-baby-stars-a-million-light-years-away.html.
Famous Black Hole has Jet Pushing Cosmic Speed Limit
Chandra data shows that the black hole in the galaxy Messier 87 (M87) is propelling particles away from it faster than 99% the speed of light. These remarkable speeds were detected in changes in the X-ray emission between 2012 and 2017 in regions along a jet generated by the black hole. M87 became famous in April 2019 when the Event Horizon Telescope released the first-ever direct image of its black hole. The jet seen with Chandra is 500,000 times larger and shows much older activity from the black hole than the ring imaged by the EHT.
For more information see: https://chandra.cfa.harvard.edu/photo/2020/m87/.
Marshall scientist presents ground-breaking gamma-ray research at conference in Japan.
Dr. Daniel Kocevski gave an invited talk on the high-energy detection of GRB 190114C at a conference held in Yokohama, Japan. The talk focused on the Fermi and Swift contributions to a paper reporting the first very high-energy detection of a gamma-ray burst (GRB) by ground-based air Cherenkov telescopes. The detection gave high-energy astrophysicists a better understanding of accelerated mechanisms that generate the gamma-rays from these events. The paper has been accepted for publication in the journal Nature.
On January 14, 2019, just before 4:00 p.m. EST, both the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory detected a spike of gamma rays from the constellation Fornax. These distant explosions have produced the highest-energy light yet seen from these events, called gamma-ray bursts, or GRBs. The missions alerted the astronomical community to the location of the burst, dubbed GRB 190114C.
One facility receiving the alerts was the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) observatory located on La Palma in the Canary Islands, Spain. Both of its 17-meter telescopes automatically turned to the site of the facing burst. They began observing the GRB just 50 seconds after it was discovered and captured the most energetic gamma rays yet seen from these events. With GRB 190114C, MAGIC became the first facility to report unambiguous very high-energy (VHE) emission, with energies up to a trillion electron volts (1 TeV). That's 10 times the peak energy Fermi has seen to date.
Scientists suspect that most of the gamma rays from GRB afterglows originate in magnetic fields at the jet's leading edge. High-energy electrons spiraling in the fields directly emit gamma rays through a mechanism called synchotron emission. But other scientists, including the MAGIC team, interpret the VHE emission as a distinct afterglow component, which means some additional process must be at work, perhaps inverse Compton scattering. High-energy electrons in the jet crash into lower-energy gamma rays and boost them to much higher energies.
In the paper detailing the Fermi and Swift observations, the researchers conclude that an additional physical mechanism may be needed to produce the VHE emission. Within the lower energies observed by these missions, however, the flood of synchotron gamma rays makes uncovering a second process much more difficult.
Several papers have been published about GRB 190114C. Dr. Kocevski's invited talk presented information from the paper titled "Fermi and Swift Observations for GRB 190114c: Tracing the Evolution of High-Energy Emission from Prompt to Afterglow," for which he was one of the authors.
This paper on the Fermi and Swift contributions can be found at https://arxiv.org/abs/1909.10605.
Additional data and information about MAGIC and GRB 190114C can be found at: https://www.nature.com/articles/s41586-019-1750-x.
Read the Goddard press release here: https://www.nasa.gov/feature/goddard/2019/nasa-s-fermi-swift-missions-enable-a-new-era-in-gamma-ray-science/.
Time Domain Astronomy with the Fermi Gamma-Ray Burst Monitor in the Multimessenger Era presented at Yale University.
On Thursday, November 7, 2019, Dr. Colleen Wilson-Hodge presented an invited Yale Astronomy and Astrophysics Colloquium about the Fermi Gamma-ray Burst Monitor and its exciting science for transients ranging from gravitational wave counterparts to pulsars and magnetars to solar flares and terrestrial gamma-ray flashes. During an impromptu lunchtime talk, when she was asked to speak extemporaneously without slides, she described her experiences with current and future missions for NASA, including the path that led to her involvement in the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X).
To find out more about STROBE-X, go to this site: https://gammaray.nsstc.nasa.gov/Strobe-X/index.html.
To view a link to the seminar, visit: https://astronomy.yale.edu/event/yale-astronomy-astrophysics-colloquium-colleen-wilson-hodge.
Lynx team presented to the ASTRO2020 Panel on the Electromagnetic Observations from Space 2
On November 6, 2018, the Lynx Team presented to the Astro2020 EOS2 panel on the science, technical, and cost of the Lynx mission. Lynx is one of four flagship mission concepts that would launch in the 2030s, after the James Webb Space Telescope and the Wide Field InfraRed Survey Telescope. if prioritized by the Astro2020 Decadal. The Decadal Survey on Astronomy and Astrophysics (Astro2020) is a partnership between the National Academies and the Astronomical community to identify key priorities in astronomy and astrophysics and develop a comprehensive strategy for agency investments in the upcoming decade. Participants from MSFC included Karen Gelmis (ST14), Jessica Gaskin (ST14), and Douglas Swartz (ST12/USRA).
Lynx will provide unprecedented X-ray vision into the otherwise "Invisible" Universe with unique power to directly observe the dawn of supermassive black holes, reveal the drivers of galaxy formation, trace stellar activity including effects on planet habitability, and transform our knowledge of endpoints of stellar evolution.
The clumpy and lumpy death of a star.
A Chandra press release was issued on October 17, 2019 describing new data from Chandra and other telescopes providing a new image of the Tycho supernova remnant from Chandra. The pattern shows bright clumps and fainter holes in the X-ray data. Scientists are trying to determine if this "clumpiness" was caused by the supernova explosion itself or something in tis aftermath. By comparing Chandra data to computer simulations, researchers found evidence that the explosion was likely the source of this lumpy distribution. The original supernova was first seen by skywatchers in 1572, including the Danish astronomer Tycho Brahe for whom the object was eventually named.
For more information go to https://chandra.cfa.harvard.edu/photo/2019/tycho/.
Chandra spots a mega-cluster of galaxies in the making.
A Chandra press release was issued on October 24, 2019, describing a mega-merger of four galaxy clusters in Abell 1758 which was observed by Chandra and other telescopes. Abell 1758 contains two pairs of galaxy clusters, each with hundreds of galaxies embedded in large amounts of hot gas and unseen dark matter. Eventually these two pairs of clusters will collide to form one of the most massive objects in the Universe. The X-rays from Chandra helped astronomers estimate how fast one pair of clusters were moving toward each other.
For more information, go to https://chandra.cfa.harvard.edu/photo/2019/a1758/.
Fermi Gamma-ray Burst Monitor (GBM) continues to follow up unique gravitational wave detections.
September has been an exciting time for the gamma-ray follow up by the Fermi Gamma-ray Burst Monitor of gravitational wave detections. The past four weeks saw the detection of two binary neutron star merger candidates and three neutron star black hole merger candidates by the LIGO Scientific collaboration and the Virgo Collaboration. The merger of two neutron stars has long been thought to be the origin of short GRBs, a theory that was confirmed by the detection of GRB 170817 in both gamma-rays and gravitational waves. It is currently an open question as to whether neutron star black hole mergers could also produce short GRBs, and the past few months have seen the first of these kind of detections by LIGO and Virgo. the GBM did not detect coincident emission from any of the recent binary neutron star or neutron star black hole mergers, but additional observations of such events gives astronomers valuable insight into the ubiquity of electromagnetic emission from such mergers and may be used in the future to constrain theories that aim to explain how these systems work.
Fermi and Swift Observations of GRB 190114C: Tracing the evolution of high-energy emission from prompt to afterglow.
The Fermi Gamma-ray Burst Monitor (GBM) team in Huntsville, working with members of the Fermi Large Area Telescope (LAT) collaboration and the Neil Gehrels Swift Observatory, released a paper on the high-energy observations of gamma-ray burst (GRB) 190114C. GRB 190114C was a unique event in that it was the first GRB ever detected by a ground-based Cherenkov telescope at energies in excess of 1 TeV. Long GRBs result from the explosion of massive stars in distant galaxies and are among the most energetic supernovae ever detected. the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope, located in the Canary Islands, was able to observe the GRB within a minute of its detection by GBM and Swift. The MAGIC observations revealed gamma-ray emission over a million times higher in energy than the emission typically observed by GBM from these events. The combined Fermi and Swift observations placed these VHE observations in context, but providing comprehensive observations at lower energies and revealed how that emission evolved with time.
Using these observations, the Fermi and Swift teams were able to estimate the energy and speed of the relativistic blast wave that was created when the progenitor star went supernova. Being able to measure these properties allowed the Fermi and Swift teams to show that a theory used to explain the emission observed by the GBM and LAT instruments could not also explain the VHE emission observed by MAGIC and that an additional emission mechanism would be needed. The combined observations ultimately allows astronomers to obtain a better understanding of the physics behind the most energetic explosions in the Universe.
You can find the paper online at https://arxiv.org/abs/1909.10605.
Evaluation of Automated Fermi GBM Localizations of Gamma-ray Bursts
The Fermi Gamma-ray Burst Monitor (GBM) detects onboard roughly 240 gamma-ray bursts (GRBs) a year, and the localization of these events and other transients observed by GBM are of prime importance in the era of multi-messenger and time-domain astronomy. To this end, an accurate estimate of the GBM localization uncertainty is a requirement to prevent reporting over-confident localizations that may result in false counterpart associations or lead to ruling out real associations. Therefore, it is important for GBM localizations to be as precise as possible and to account for systematic uncertainty to ensure the overall reported accuracy is reliable.
The GBM team implemented improvements to its automated localization algorithm of GRBs, called RoboBA, and compared the operation of the original and updated version of RoboBA to an alternative, independently-developed localization algorithm, BALROG. Through a systematic study utilizing over 500 GRBs with known locations from instruments like Swift and the Fermi LAT, the GBM team directly compare the effectiveness of, and accurately estimate the systematic uncertainty for, both algorithms.
The GBM team showed that simple adjustments to RoboBA, in operation since early 2016, yields significant improvement in the systematic uncertainty, removing the long tail previously identified in the systematic, and improved the overall accuracy. The systematic uncertainty for the updated RoboBA localizations is 1.8 deg. for 52% of GRBs and 4.1 deg. for the remaining 48%. Both from public reporting by BALROG and the GBM team's systematic study, the systematic uncertainty of 1-2 deg. quoted by the BALROG team for bright GRBs is an underestimate of the true magnitude of the systematic, which is found to be 2.7 deg. for 74% of GRBs and 33 deg. for the remaining 26%. The GBM team showed that, once the systematic uncertainty is considered, the RoboBA 90% localization confidence regions can be more than an order of magnitude smaller in area than those produced by BALROG.
Read the paper online at https://arxiv.org/abs/1909.03006.
The Fermi Gamma-ray Burst Monitor receives positive senior review results.
The Fermi 2019 Senior Review (SR) results have been released and the Fermi mission, including operations of the Gamma-Ray Burst Monitor (GBM), have been extended into 2022. Led by a team at NASA's Marshall Space Flight Center and the University of Alabama in Huntsville, GBM is currently the most prolific detector of transient astrophysical gamma-rays in the sky. The unique, full-sky observational capability of GBM was lauded and Fermi's scientific merit expectations were directly tied to GBM's multi-messenger observations with the Laser Interferometer Gravity Wave Observatory (LIGO) and other gravitational wave observatories. The Fermi Mission was also invited to submit another extended mission proposal for the 2022 SR cycle.
The full astrophysics Senior Review report can be found at: https://science.nasa.gov/astrophysics/2019-senior-review-operating-missions
Chandra's 20th Anniversary!
In 2019, NASA's Chandra X-ray Observatory celebrates its 20th year in space exploring the extreme universe.
Listen to a Public Radio Hour special on Chandra featuring Marshall scientists, Dr. Martin Weisskopf and Dr. Jessica Gaskin, as they join historian Brian Odom to talk about Chandra's discoveries. Just click on the link below.
Marshall X-ray optics will map the X-ray universe.
Scientists and technicians at the Marshall Space Flight Center (MSFC) have designed and fabricated eight Astronomical Roentgen Telescope - X-ray Concentrator (ART-XC) X-ray optics modules that have been launched into space as part of the Spectrum-Roentgen-Gamma (SRG or Spectr-RG observatory) mission. The purpose of this mission is to study the Universe's X-ray range of electromagnetic radiation and create a map of the X-ray Universe including large clusters of galaxies and active galactic nuclei. The SRG mission successfully launched from the Baikonur Cosmodrome on July 13, 2019.
The SRG mission is a Russian-led X-ray astrophysical observatory that carries two, co-aligned, X-ray telescope systems. The extended Roentgen Survey with an Imaging Telescope Array (eROSITA) is the German-led primary instrument for the mission and is a 7-module X-ray telescope system that operates in the 0.2 - 10 KeV band. The complementary instrument is the Astronomical Roentgen Telescope – X-ray Concentrator (ART-XC). This instrument is a seven module X-ray telescope system that operates in the 4-30 KeV energy range.
Marshall Space Flight Center designed and fabricated the seven (and one spare) co-aligned X-ray mirror modules making up the ART-XC telescope. Each module is composed of 28 concentric grazing-incidence mirror shells made using the same electroform-nickel replication process developed at MSFC for numerous space astrophysics and ground-based research applications.
You can learn more about the SRG mission by clicking on the following sites:
LISA Pathfinder sheds new light on interplanetary dust.
Researchers examining LISA Pathfinder data have been able to detect tiny impacts from cosmic dust, identify where the dust came from, and reveal clues to their origin. Read the full article from physicsworld to find out about cosmic dust and the search for gravitational waves. | 0.930423 | 3.556494 |
From: Jet Propulsion Laboratory
Posted: Thursday, April 21, 2011
Image: A newly found, buried deposit of frozen carbon dioxide -- dry ice -- near the south pole of Mars contains about 30 times more carbon dioxide than previously estimated to be frozen near the pole. This map color-codes thickness estimates of the deposit derived and extrapolated from observations by the Shallow Subsurface Radar (SHARAD) instrument on NASA's Mars Reconnaissance Orbiter. The orbiter does not pass directly over the pole, and the thickness estimates for that area (with smoother transitions from color to color) are extrapolations. Red corresponds to about 600 meters or yards thick; yellow to about 400; dark blue to less than 100, tapering to zero. The scale bar at lower right is 100 kilometers (62 miles). The background map, in muted colors, represents different geological materials near the south pole. More images
NASA's Mars Reconnaissance Orbiter (MRO) has discovered the total amount of atmosphere on Mars changes dramatically as the tilt of the planet's axis varies. This process can affect the stability of liquid water if it exists on the Martian surface and increase the frequency and severity of Martian dust storms.
Researchers using MRO's ground-penetrating radar identified a large, buried deposit of frozen carbon dioxide, or dry ice, at the Red Planet's south pole. The scientists suspect that much of this carbon dioxide enters the planet's atmosphere and swells the atmosphere's mass when Mars' tilt increases. The findings are published in a report in the journal Science.
The newly found deposit has a volume similar to Lake Superior's nearly 3,000 cubic miles. The deposit holds up to 80 percent as much carbon dioxide as today's Martian atmosphere. Collapse pits caused by dry ice sublimation and other clues suggest the deposit is in a dissipating phase, adding gas to the atmosphere each year. Mars' atmosphere is about 95 percent carbon dioxide, in contrast to Earth's much thicker atmosphere, which is less than .04 percent carbon dioxide.
"We already knew there is a small perennial cap of carbon-dioxide ice on top of the water ice there, but this buried deposit has about 30 times more dry ice than previously estimated," said Roger Phillips of Southwest Research Institute in Boulder, Colo. Phillips is deputy team leader for MRO's Shallow Radar instrument and lead author of the report.
"We identified the deposit as dry ice by determining the radar signature fit the radio-wave transmission characteristics of frozen carbon dioxide far better than the characteristics of frozen water," said Roberto Seu of Sapienza University of Rome, team leader for the Shallow Radar and a co-author of the new report.
Additional evidence came from correlating the deposit to visible sublimation features typical of dry ice.
"When you include this buried deposit, Martian carbon dioxide right now is roughly half frozen and half in the atmosphere, but at other times it can be nearly all frozen or nearly all in the atmosphere," Phillips said.
An occasional increase in the atmosphere would strengthen winds, lofting more dust and leading to more frequent and more intense dust storms. Another result is an expanded area on the planet's surface where liquid water could persist without boiling. Modeling based on known variation in the tilt of Mars' axis suggests several-fold changes in the total mass of the planet's atmosphere can happen on time frames of 100,000 years or less.
The changes in atmospheric density caused by the carbon-dioxide increase also would amplify some effects of the changes caused by the tilt. Researchers plugged the mass of the buried carbon-dioxide deposit into climate models for the period when Mars' tilt and orbital properties maximize the amount of summer sunshine hitting the south pole. They found at such times, global, year-round average air pressure is approximately 75 percent greater than the current level.
"A tilted Mars with a thicker carbon-dioxide atmosphere causes a greenhouse effect that tries to warm the Martian surface, while thicker and longer-lived polar ice caps try to cool it," said co-author Robert Haberle, a planetary scientist at NASA's Ames Research Center in Moffett Field, Calif. "Our simulations show the polar caps cool more than the greenhouse warms. Unlike Earth, which has a thick, moist atmosphere that produces a strong greenhouse effect, Mars' atmosphere is too thin and dry to produce as strong a greenhouse effect as Earth's, even when you double its carbon-dioxide content."
The Shallow Radar, one of MRO's six instruments, was provided by the Italian Space Agency and its operations are led by the Department of Information Engineering, Electronics and Telecommunications at Sapienza University of Rome. NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the MRO project for NASA's Science Mission Directorate at the agency's headquarters in Washington. Lockheed Martin Space Systems in Denver built the spacecraft.
For more information about MRO, visit: http://www.nasa.gov/mro
// end // | 0.862424 | 3.916964 |
It takes about a century to take the very first picture of the black hole. Here are some really amazing and interesting facts you should know about the black hole and NASA’s first picture of it.
1. You can’t directly see a black hole. To achieve the necessary resolution to see a black hole directly a single telescope would need to be the size of planet earth.
2. The massive gravitational influence of a black hole distorts space and time in the near neighborhood. The closer you get to a black hole, the slower time runs. Material that gets too close to a black hole gets sucked in and can never escape.
3. In 2009 Event Horizon Telescope (EHT) is a collaboration of many Institution and sites to make a telescope the size of the earth, giving us the highest resolution to capture the image of Black Hole. It consists of 8 telescopes around the globe. In April 2019 we capture the very first image of the Black Hole.
4. The image is based on data from radio telescopes all over the world, so it’s not technically even a picture of a black hole. Black holes are, scientifically speaking, unseeable.
5. The black hole in Christopher Nolan’s ‘Interstellar’ wasn’t so far off from the real thing. It was all VFX but now as we have the real image of the Blackhole we can say that both looks quite the same. (If you haven’t watched Interstellar then you must, it’s an amazing movie.)
6. Material spirals into a black hole through an accretion disk — a disk of gas, dust, stars, and planets that fall into orbit the black hole.
7. The “point of no return” around a black hole is called the “event horizon”. This is the region where the gravity of the black hole overcomes the momentum of material spinning around it in the accretion disk. Once something crosses the event horizon, it is lost to the pull of the black hole.
8. Black holes were first proposed to exist in the 18th century but remained a mathematical curiosity until the first candidate black hole was found in 1964. Cygnus X-1 was first found a black hole, according to NASA, the black hole is 10 times more massive to the Sun. Nearby is a blue supergiant star that is about 20 times more massive than the Sun, which is bleeding due to the black hole and creating X-ray emissions.
9. Black holes do not emit radiation on their own. They are detected by the radiation given off as the material is heated in the accretion disk, and also by the black hole’s gravitational effect on other nearby objects (or light passing by).
10. There are at least three types of black holes, Primordial black holes are the smallest kinds and range in size from one atom’s size to a mountain’s mass. Stellar black holes, the most common type, are up to 20 times more massive than our own Sun and are likely sprinkled in the dozens within the Milky Way. And then there are the gargantuan ones in the centers of galaxies, called “supermassive black holes.” They’re each more than one million times more massive than the Sun. How these beasts formed is still being examined.
Black Holes Photos:-
Using the Event Horizon Telescope, scientists obtained an image of the black hole at the center of galaxy M87, outlined by emission from hot gas swirling around it under the influence of strong gravity near its event horizon.
Official NASA blog about Black Hole photo 2019. | 0.925757 | 3.722972 |
Pulsar path over about 2.5 million years. Image credit: Bill Saxton, NRAO/AUI/NSF Click to enlarge
A speeding, superdense neutron star somehow got a powerful “kick” that is propelling it completely out of our Milky Way Galaxy into the cold vastness of intergalactic space. Its discovery is puzzling astronomers who used the National Science Foundation’s Very Long Baseline Array (VLBA) radio telescope to directly measure the fastest speed yet found in a neutron star.
The neutron star is the remnant of a massive star born in the constellation Cygnus that exploded about two and a half million years ago in a titanic explosion known as a supernova. Ultra-precise VLBA measurements of its distance and motion show that it is on course to inevitably leave our Galaxy.
“We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding,” said Shami Chatterjee, of the National Radio Astronomy Observatory (NRAO) and the Harvard-Smithsonian Center for Astrophysics. “This discovery is very difficult for the latest models of supernova core collapse to explain,” he added.
Chatterjee and his colleagues used the VLBA to study the pulsar B1508+55, about 7700 light-years from Earth. With the ultrasharp radio “vision” of the continent-wide VLBA, they were able to precisely measure both the distance and the speed of the pulsar, a spinning neutron star emitting powerful beams of radio waves. Plotting its motion backward pointed to a birthplace among groups of giant stars in the constellation Cygnus — stars so massive that they inevitably explode as supernovae.
“This is the first direct measurement of a neutron star’s speed that exceeds 1,000 kilometers per second,” said Walter Brisken, an NRAO astronomer. “Most earlier estimates of neutron-star speeds depended on educated guesses about their distances. With this one, we have a precise, direct measurement of the distance, so we can measure the speed directly,” Brisken said. The VLBA measurements show the pulsar moving at nearly 1100 kilometers (more than 670 miles) per second — about 150 times faster than an orbiting Space Shuttle. At this speed, it could travel from London to New York in five seconds.
In order to measure the pulsar’s distance, the astronomers had to detect a “wobble” in its position caused by the Earth’s motion around the Sun. That “wobble” was roughly the length of a baseball bat as seen from the Moon. Then, with the distance determined, the scientists could calculate the pulsar’s speed by measuring its motion across the sky.
“The motion we measured with the VLBA was about equal to watching a home run ball in Boston’s Fenway Park from a seat on the Moon,” Chatterjee explained. “However, the pulsar took nearly 22 months to show that much apparent motion. The VLBA is the best possible telescope for tracking such tiny apparent motions.”
The star’s presumed birthplace among giant stars in the constellation Cygnus lies within the plane of the Milky Way, a spiral galaxy. The new VLBA observations indicate that the neutron star now is headed away from the Milky Way’s plane with enough speed to take it completely out of the Galaxy. Since the supernova explosion nearly 2 and a half million years ago, the pulsar has moved across about a third of the night sky as seen from Earth.
“We’ve thought for some time that supernova explosions can give a kick to the resulting neutron star, but the latest computer models of this process have not produced speeds anywhere near what we see in this object,” Chatterjee said. “This means that the models need to be checked, and possibly corrected, to account for our observations,” he said.
“There also are some other processes that may be able to add to the speed produced by the supernova kick, but we’ll have to investigate more thoroughly to draw any firm conclusions,” said Wouter Vlemmings of the Jodrell Bank Observatory in the UK and Cornell University in the U.S.
The observations of B1508+55 were part of a larger project to use the VLBA to measure the distances and motions of numerous pulsars. “This is the first result of this long-term project, and it’s pretty exciting to have something so spectacular come this early,” Brisken said. The VLBA observations were made at radio frequencies between 1.4 and 1.7 GigaHertz.
Chatterjee, Vlemmings and Brisken worked with Joseph Lazio of the Naval Research Laboratory, James Cordes of Cornell University, Miller Goss of NRAO, Stephen Thorsett of the University of California, Santa Cruz, Edward Fomalont of NRAO, Andrew Lyne and Michael Kramer, both of Jodrell Bank Observatory. The scientists presented their findings in the September 1 issue of the Astrophysical Journal Letters.
The VLBA is a system of ten radio-telescope antennas, each with a dish 25 meters (82 feet) in diameter and weighing 240 tons. From Mauna Kea on the Big Island of Hawaii to St. Croix in the U.S. Virgin Islands, the VLBA spans more than 5,000 miles, providing astronomers with the sharpest vision of any telescope on Earth or in space.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreeement by Associated Universities, Inc.
Headquartered in Cambridge, Massachusetts, the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists organized into seven research divisions study the origin, evolution, and ultimate fate of the universe.
Original Source: CfA News Release | 0.871709 | 4.047905 |
A Unique Metal-Rich Chondrite
Details of Northwest Africa (NWA) 12379, a meteorite unlike any previously identified
Researchers supported in part by the Emerging Worlds Program have reported the mineralogy, petrology, and oxygen isotopic composition of Northwest Africa (NWA) 12379. This metal-rich chondrite was discovered in Morocco near the border of Algeria sometime between August 2017 and September 2018. NWA 12379 shows a number of unique characteristics that distinguish it from all previously described meteorites. Some features found in NWA 12379 are similar to metal-rich carbonaceous and G chondrites, while others more closely resemble ordinary chondrites.
The team suggests that NWA 12379 should be classified as an ungrouped metal-rich chondrite, with the affinity of its non-metal portion to unequilibrated ordinary chondrites. They propose that NWA 12379 was formed by a collision of two such bodies, one similar to an ordinary chondrite and the other metal-rich.
Meteorites are remnants of the early Solar System, and studying their composition can provide clues about the evolution of planets and other bodies that orbit the Sun. These objects also provide an inventory of the materials that the planets formed from, as well as materials that could have been delivered to the Earth’s surface at the time of life’s origins. Meteorites can help astrobiologists reconstruct the events that shaped the formation of Earth and the conditions that led our planet to become habitable for life. Understanding how life gained a foothold on Earth is important in the search for life elsewhere in the Universe.
The study, “Mineralogy, Petrology, and Oxygen Isotopic Composition of Northwest Africa 12379, Metal-Rich Chondrite with Affinity to Ordinary Chondrites,” was published in the journal Geochemistry. This work was supported by the Emerging Worlds Program. The NASA Astrobiology Program provides resources for Emerging Worlds and other Research and Analysis programs within the NASA Science Mission Directorate (SMD) that solicit proposals relevant to astrobiology research. This research is a critical part of NASA’s work to understand the Universe, advance human exploration, and inspire the next generation. As NASA’s Artemis program moves forward with human exploration of the Moon, the search for life on other worlds remains a top priority for the agency. | 0.803791 | 3.338664 |
Someone else asked a similar question that was linked here as a duplicate. It seems that question isn't quite the same, but similar enough that it makes sense to put it here.
That person asked:
I know that the Sun is made up of hydrogen and helium.
Also, hydrogen explodes when it touches a flame.
But why does the Sun not explode?
The kind of explosion that happens when hydrogen touches flame is an exothermic chemical reaction in which hydrogen is rapidly combined with oxygen (oxidation). When heat is applied (flame) to hydrogen (H2) in the presence of oxygen (O2), it causes a molecule of O2 to separate and each oxygen atom to bind with a molecule of H2. When this happens, it releases a large amount of energy ( believe this is caused by the breaking of the O2 bonds), and you end up with water (probably steam) and heat (fire).
The kind of "buring" that happens in stars is thermonuclear fission. When two atoms of hydrogen are brought together by immense heat and pressure, they fuse into an atom of helium. In this process, enormous amounts of energy are released. This is the same nuclear reaction that takes place in a thermonuclear fusion bomb. It does not involve a chemical change, but a nuclear one.
Let me take a half-step back on that. A chemical change or reaction is when the atoms rearrange themselves in molecules. In most such reactions, energy is either absorbed (endothermic) or released (exothermic). Sometimes fairly large amounts are released. Explosives such as gunpowder, TNT, C4, and the like are all chemical explosives and mostly their reactions involve very rapid oxidation of the substance being burned. The burning of a match, candle or campfire is the same type of chemical oxidation reaction, but at a much slower pace.
Nuclear reactions come in two main types: fission and fusion. Fission is the splitting of larger atoms into smaller ones. The isotope of uranium with an atomic mass of 235 (92 protons and 143 neutrons) has a half-life of about 700 million years (which is far shorter than the 4.5 billion year half-life of the more common U238). Atoms naturally decay over time, and in a span of 700 million years, a mass of U235 will naturally split on its own and the number of atoms will reduce by half (hence the term half-life). When an atom of U235 splits, it releases a bunch of energy, produces an atom of krypton and one of barium, and releases a few extra neutrons. When one of these neutrons meets another atom of U235, it joins that atom, which destabilizes it, and causes the reaction to happen again. Note: because we are talking about reactions in the nucleus of the atom and resulting changes to the atoms themselves, we are talking about nuclear reactions, not chemical ones.
The reaction I mentioned above takes place in U235 naturally. If you don't have much of it and it's not in a dense enough state, it just sits there like a lump of rock and seems to do nothing. Most of the neutrons it releases don't find another atom to play with, and end up just flying off into space. But if you squeeze it down enough or get enough of it together, more neutrons are meeting up with other atoms than are flying off into nowhere. This creates a chain reaction, which is the basis for nuclear power and nuclear weapons.
A reactor works by controlling the rate of this reaction, keeping it from going too fast. Lumps of uranium are held just close enough together to react,but not rapidly, and rods of neutron-absorbing material (usually graphite) are slid between the lumps to help absorb the neutrons and prevent them from causing more reactions. A nuclear meltdown occurs when the reaction gets out of control and heats up so much that it literally melts the framework holding it all together.
This isn't enough, however, to create a nuclear explosion. That occurs when you apply pressure and squeeze the material down, increasing its density. U235 isn't actually suited for this, but element 94, plutonium, is. When you squeeze plutonium down to a high enough density, this reaction happens extremely rapidly. First one atom of Pu239 splits, releasing its energy in the form of light and heat along with additional neutrons. Then those extra neutrons find other atoms of Pu239 and cause them to split. Every split creates at least twice as many extra neutrons as splitting atoms. The first atom splits to cause 2 to split, which split and cause 2 each for four, then eight, sixteen, 32, 64, 128, 256, 512, 1024, 2048, 4096... each "generation" of these splits is double the previous. This all happens at a time scale measured in tiny fractions of a second, the time it takes light to go only a few millimeters. This all builds up tremendous amounts of heat and pressure, which, unconstrained, erupt out of the core of the bomb.
As it turns out, only a small percentage of the original mass is actually lost to fission. The heat and pressure build up so great so fast that it forces the atoms away from each other in the explosion, thus ending the reaction. In fact, in a fission bomb, before anything other than high-energy x- and gamma rays leaves the bomb case, the reaction is complete, all that's left is for it to expand outward due to the immense pressure.
The other kind of nuclear reaction, fusion, is also used in bombs. In fusion, as I mentioned above, huge amounts of pressure are used to force atoms of lighter elements, typically hydrogen, together. Every time two atoms of hydrogen fuse into one, a huge amount of heat and energy are released (to be honest, I've never understood why energy is released here and not absorbed, but I'm not a nuclear physicist, just a guy who likes to read a lot). In bombs, the 'trigger' for the fusion is actually a fission bomb. The fission bomb creates the heat and pressure necessary, and when hydrogen atoms are added to the mix (usually in the form of tritium or deuterium), the fusion reaction begins and starts adding its heat and pressure to the pot, which helps sustain the reaction long enough to put out an amount of energy several times that which the fusion bomb started.
If you remember back to your high school chemistry lessons, Boyle's Law states $P_1V_1 = P_2V_2$. P is pressure, V is volume. This formula shows that pressure and volume are inextricably interconnected. Charles' law states that $V_1T_2 = V_2T_1$, showing the interrelation between volume and temperature. Gay-Lussac's law, $P_1T_2 = P_2T_1$ shows the relation between pressure and temperature. These all come together into the combined gas law and Avogadro's law. They show that if you increase the pressure, volume, or temperature of a mass, the others are affected as well. An increase in pressure results in an increase of temperature. A decrease of volume creates an increase in pressure which create an increase in temperature. If you increase the volume, the temperature and pressure decrease. Etc...
Ok, so, now here's where it all applies to stars.
In the result of the Big Bang, most of the matter created was hydrogen. There was some helium and a little lithium, but the overwhelming majority was hydrogen.
When the hydrogen molecules floating through space started to clump together through gravity, they started to condense down into smaller and smaller volumes. Separately, the gravity of a single atom of hydrogen is minuscule. But as more and more of them interacted, the combined gravity began to build up. The clouds became more and more compact - denser, and their gravity brought in more and more mass, which added their gravity to the total. Things began to heat up, due to the pressure caused by the volume. The gravity started to get to be enough to continue to pull things toward the center of mass, into the "gravity well" caused by the cloud. As the heat increased due the the pressure caused by gravity, it caused outward pressure. The forces continued to balance each other. As more mass fell in, gravity increased, causing more heat, which caused more pressure, which pushed outward... and so on.
At a certain point, the gravity gets so great, that it exerts enough pressure on the center of the mass to cause nuclear fusion. This, in turn, causes more pressure outward, but the force of gravity of the entire mass is great enough to keep it all together. This is when a star is born. The pressure of gravity has caused a gravitational collapse to ignite into a star. The balance of the forces of gravity and heat and pressure are what keep it going. If there wasn't enough pressure outward, it would collapse further into a singularity (a black hole), if there's too much pressure outward, it would either explode (type II supernova) or at least expand outward until balance, what we call hydrostatic equilibrium, is achieved again.
As a star ages and burns through its supply of hydrogen, the equilibrium changes and at some point it begins to burn helium. After that, carbon. Depending on the original mass, it may fuse other materials up to iron.
In some stars, the mass is enough that when the fusion can no longer be supported, there is no longer enough outward pressure, and the core collapses in on itself. The gravity increases as it shrinks, and there's not enough heat or pressure to overcome it. It collapses to a point of infinite density and becomes a gravitational singularity and a black hole is created. In other stars, the mass isn't quite enough to keep collapsing, and the pressure overcomes it in a massive explosion (type II supernova). In other stars, the star belches out wave after wave of gas as it expands and contracts, finally belching enough away to no longer have enough reactive mass. It shrinks down into a white dwarf - a hot ball of atomic particles that slowly cools over billions and billions of years until they are no longer luminous, becoming a black dwarf (the time for this to occur is believed to be so long that there are, as yet, no black dwarfs in the universe... but there someday should be, long, long in the future).
So, to circle back to the original questions... why doesn't the sun explode, and why doesn't the hydrogen in the sun explode... the main reason is gravity. It reaches a balance. The heat and pressure pushing are balanced against the gravity pulling in. There is no chemical oxidation going on, because the atoms of hydrogen are being fused into helium and there's little oxygen to be consumed in the oxidation process to begin with. Someday we expect the sun will run out of hydrogen to burn. As it starts burning helium, it will expand out past the orbit of Mars, then at some point it will shed its cooler, outer layers and contract into a white dwarf which will slowly cool down to a dying ember in the ever darkening universe. | 0.84859 | 3.592084 |
Planet 9 takes shape
Astrophysicists at the University of Bern have modelled the evolution of the putative planet in the outer solar system. They estimate that the object has a present-day radius equal to 3.7 Earth radii and a temperature of minus 226 degrees Celsius.
How big and how bright is Planet 9 if it really exists? What is its temperature and which telescope could find it? These were the questions that Christoph Mordasini, professor at the University of Bern, and his PhD student Esther Linder wanted to answer when they heard about the possible additional planet in the solar system suggested by Konstantin Batygin and Mike Brown of the California Institute of Technology in Pasadena.
The Swiss scientists are experts in modelling the evolution of planets. They usually study the formation of young exoplanets in disks around other stars light years away and the possible direct imaging of these objects with future instruments such as the James Webb Space Telescope. Therefore, Esther Linder says: “For me candidate Planet 9 is a close object, although it is about 700 times further away as the distance between the Earth and the Sun.” The astrophysicists assume that Planet 9 is a smaller version of Uranus and Neptune – a small ice giant with an envelope of hydrogen and helium. With their planet evolution model they calculated how parameters like the planetary radius or the brightness evolved over time since the solar system has formed 4,6 billion of years ago. The study was financed by the research project of the Swiss National Science Foundation PlanetsInTime and the National Center for Competence in Research (NCCR) PlanetS.
Heated from the inside
In their paper accepted by the journal “Astronomy & Astrophysics” the scientists conclude that a planet with the projected mass equal to 10 Earth masses has a present-day radius of 3.7 Earth radii. Its temperature is minus 226 degrees Celsius or 47 Kelvin. “This means that the planet’s emission is dominated by the cooling of its core, otherwise the temperature would only be 10 Kelvin,” explains Esther Linder: “Its intrinsic power is about 1000 times bigger than its absorbed power.” Therefore, the reflected sunlight contributes only a minor part to the total radiation that could be detected. This also means that the planet is much brighter in the infrared than in the visual. “With our study candidate Planet 9 is now more than a simple point mass, it takes shape having physical properties,” says Christoph Mordasini.
The researchers also checked if their results explain why planet 9 hasn’t been detected by telescopes so far. They calculated the brightness of smaller and bigger planets on various orbits. They conclude that the sky surveys performed in the past had only a small chance to detect an object with a mass of 20 Earth masses or less, especially if it is near the farthest point of its orbit around the Sun. But NASA’s Wide-field Infrared Survey Explorer may have spotted a planet with a mass equal to 50 Earth masses or more. “This puts an interesting upper mass limit for the planet,” Esther Linder explains. According to the scientists, future telescopes like the Large Synoptic Survey Telescope under construction near Cerro Tololo in Chile or dedicated surveys should be able to find or rule out candidate Planet 9. “That is an exciting perspective,” says Christoph Mordasini.
E. Linder/C. Mordasini: «Evolution and Magnitudes of Candidate Planet Nine» http://www.aanda.org/10.1051/0004-6361/201628350 | 0.884016 | 3.788576 |
The ExoMars Trace Gas Orbiter, a Russian-launched, European-built spacecraft that arrived at Mars in October, is starting to dip into the upper reaches of the red planet’s atmosphere in a year-long “aerobraking” campaign place the observatory in the right position to hunt for methane, an indicator of potential biological activity.
The effort to reshape the craft’s course around Mars uses aerodynamic drag from repeated dips into the upper atmosphere to gradually drag down the high point of the probe’s orbit from its current altitude of 20,500 miles (33,000 kilometres) to a planned perch 250 miles (400 kilometres) above the Martian surface.
Ground controllers at the European Space Operations Centre in Darmstadt, Germany, are overseeing a series of seven thruster burns to nudge the low point of the spacecraft’s orbit from an altitude of 120 miles (200 kilometres) down to 70 miles (113 kilometres).
The Trace Gas Orbiter completed the first two burns Wednesday and Saturday, according to Håkan Svedhem, TGO’s project scientist at the European Space Agency. He said the orbit’s low point was at an altitude of 87 miles (140 kilometres), as of Monday.
The next orbit-lowering maneuver is scheduled for Tuesday, followed by more burns March 24, March 27, April 1 and April 6.
“It’s not ESA’s first experience with aerobraking, but it is the first time we’ve used this technique to achieve a planned science orbit, repeating it for such a long duration,” said Michel Denis, ESA’s ExoMars flight director. “The mission controllers have worked intensively with our flight dynamics experts to prepare for this challenging phase – we’re go for aerobraking.”
The gradual step-down into TGO’s aerobraking orbit allows ground controllers to monitor pressures and temperatures on the spacecraft.
“The atmospheric models aren’t perfect, so we have to ‘feel’ our way down to the start of aerobraking proper,” said Chris White, an ExoMars spacecraft operations engineer, in an ESA blog post describing the aerobraking procedures.
The orbiter will fly in a special orientation as it slices through the rarefied upper layers of the atmosphere, preventing direct communications with Earth at the most critical point of each orbit. As the spacecraft encounters air particles, friction will cause temperatures to rise outside the probe. Models predict the temperatures should be around 158 degrees Fahrenheit (70 degrees Celsius) on the craft’s two power-generating solar arrays during each passage.
If the temperatures reach 293 degrees Fahrenheit (145 degrees Celsius), or if other temperature and pressure redlines are exceeded, the spacecraft will automatically fire its thrusters to raise its orbit in a “pop-up” maneuver to avoid such extreme conditions on the next orbit, according to ESA.
“We’ll closely monitor the solar array temperature and the acceleration of the spacecraft, not only during the first few passages through the atmosphere but throughout the rest of 2017, and adjust the trajectory as needed,” Denis said in an ESA statement.
Changes in the density of the upper atmosphere caused by dust storms and solar activity make each TGO close approach unpredictable.
ESA’s Venus Express spacecraft flew deeper into the atmosphere of Venus during its final year of operations in 2014, gathering data about the planet’s thick, toxic atmosphere and giving European engineers experience with aerobraking techniques needed on future missions, starting with TGO.
NASA has conducted aerobraking maneuvers the red planet with the Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter missions.
The technique saves fuel, reducing the mass of a spacecraft at launch. In TGO’s case, the tradeoff saved around 1,300 pounds (600 kilogrammes) of fuel, according to ESA.
The aerobraking campaign will take a two-month hiatus in July and August, when Mars is behind the sun as seen from Earth. The conjunction disrupts normal communications with spacecraft at the red planet, so managers want to temporarily raise TGO’s orbit to a safer altitude before resuming aerobraking at the end of August.
By early 2018, the repeated passes through the Martian atmosphere should pull TGO’s peak altitude to around 250 miles. Another rocket burn will raise the low point of the orbit to the same altitude, placing the spacecraft in a circular perch to begin regular scientific observations.
The circular orbit also allows TGO to act as a data relay satellite between Earth and landers and rovers on the Martian surface. ESA and Roscosmos, the Russian space agency, plan to send a stationary landing platform and rover to the red planet in 2020, and TGO will be critical to enable communications for the mission.
The aerobraking maneuvers come after thruster burns in January and February and tilted the angle of TGO’s orbit from a path hugging the Martian equator to one circling at an angle of 74 degrees, permitting greater coverage of the planet.
TGO’s four science instruments have collected initial data since the spacecraft arrived at Mars on Oct. 19, but the meat of the mission will wait for 2018.
“These dress rehearsals enable our science teams to fine-tune their data acquisition techniques including pointing commands, iron out any software bugs, and get used to working with the data, well in advance of the start of the main mission starting next year,” Svedhem said in a press release. “What we’re seeing so far is really promising for our science goals.”
TGO’s camera has taken several test images of Mars, and the orbiter’s two atmospheric measurement suites also completed successful demos. The Russian-made FREND neutron detector, designed to look for signs of water just below the top layer of Martian soil, is also working as expected.
Svedhem said the science team has no observations planned during the year-long aerobraking campaign, but there may be opportunities to turn on the science payload to test new instrument modes.
TGO flew to Mars with the Schiaparelli lander, a demonstrator designed to test European entry, descent and landing technologies for the 2020 rover. The lander crashed after prematurely releasing its parachute and turning off its braking rockets due to incorrect altitude data fed to the craft’s computer.
The orbiter’s chief objective is to tease out the trace constituents of the Martian atmosphere, particularly methane, a gas detected intermittently over the last decade that scientists think could be produced by microbes or undiscovered ongoing geological activity.
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1. | 0.813008 | 3.201228 |
A planet orbiting a red dwarf star 20 light years away could be the first known water world, entirely covered by a deep ocean.
The planet, named Gliese 581d, is not a new discovery, but astronomers have now revised its orbit inwards, putting it within the “habitable zone” where liquid water could exist on the surface. “It is the only low-mass planet known inside the habitable zone”, says Michel Mayor of Geneva Observatory.
Mayor and his team used the European Southern Observatory’s 3.6-metre telescope in Chile to observe the low-mass star Gliese 581, and a precise spectrometer called HARPS to analyse its light.
That turned up the faint footprints of four planets, since the orbiting planets make the star wobble slightly, giving its light a slight Doppler shift. Three of the planets had been identified previously.
The outermost planet had been thought to have a period of 83 days, putting it too far away from the small star’s gentle heat to bear liquid water. But that was a mistake. “We only had a limited number of observations”, Mayor told New Scientist. Now with three times as much data, he finds an orbital period of 66 days, putting the planet closer to its star – about a quarter of the Earth-Sun distance – and just inside the red dwarf’s habitable zone.
Gliese 581d is about seven times as massive as Earth, so it is much too small to be a gas giant like Jupiter, but probably too big to be a rocky world like our own. “Around such a small star, it is very difficult to have so much rocky material at such a [large] distance,” says Mayor. Instead, the planet is likely to have a makeup similar to Neptune or Uranus, which are dominated by ices of water, ammonia and methane.
In the warmth of the habitable zone, these substances should form a sea thousands of kilometres deep. “Maybe this is the first of a new class of ocean planets. That is my favourite interpretation,” says Mayor. “Whether there is life or not, I don’t know.”
The same set of observations also revealed a new world, Gliese 581e, with only 1.9 times the mass of Earth. That is the lowest published mass of any exoplanet around a normal star – although preliminary results have hinted that another exoplanet may weigh just 1.4 Earth masses. Gliese 581e is very close to the star, however, and probably far too hot for liquid water.
The results were announced on Tuesday at the European Week of Astronomy and Space Science meeting in Hatfield, UK.
More on these topics: | 0.820284 | 3.758803 |
Jets, Not Neutrinos, May Cause Supernova Explosions, Scientists Say
2 March 2000
Austin, Texas: Astrophysicists at the University of Texas at Austin and the Naval Research Laboratory (NRL) in Washington, D.C., have developed a new theory of how supernovae explode, based on observations made at the University of Texas at Austin McDonald Observatory. The results were published in the Astrophysical Journal Letters on October 20 by Alexei Khokhlov, Elaine Oran, and Almadena Chtchelkanova of NRL and Peter Hoeflich, Lifan Wang, and J. Craig Wheeler of the University of Texas.
"Combining Texas observations with the cutting-edge numerical techniques at NRL has pointed the way to a new idea," says Wheeler, the Samuel T. & Fern Yanagisawa Regents Professor in Astronomy at the University of Texas at Austin. "We think that jets cause a major class of supernova explosions."
Supernovae are caused by the explosion of a massive star, and the explosions have been thought to arise through one of two mechanisms. In the first type, called Type Ia, massive stars can explode like a stick of dynamite, leaving no collapsed remnant. Astronomers use Type Ia supernovae as "standard candles" to measure distances in the Universe, and studies of Type Ia supernovae have suggested that the expansion of the Universe is accelerating.
Other types of supernovae involve the collapse of the center of an especially massive star to form an extremely dense object, either a neutron star or, perhaps in some circumstances, a black hole. The formation of a neutron star is thought to be more common. These types of supernovae are called Type Ib and Ic and Type II.
Astronomer Lifan Wang, a Hubble Postdoctoral Fellow at the University of Texas at Austin, has studied all types of supernovae for several years, primarily using the 2.1-meter Otto Struve Telescope at McDonald Observatory. Wang's work has focused on determining whether the light of supernovae is polarized that is, if the light waves given off by supernovae are aligned in certain directions. If a supernova's light is expanding uniformly in all directions, there is no polarization. There will be measurable polarization if light from the parts of the supernova is spreading asymmetrically.
All the supernovae Wang has examined that are thought to arise from core collapsethe Type Ib and Ic and Type II supernovaehave been substantially polarized, and hence substantially "out-of-round." At the same time, all the Type Ia supernovae have shown little or no polarization.
For the polarized supernovae, Wang has identified a trend suggesting that the closer one looks to the center of a supernova explosion, the larger the asymmetry found. In many cases, his data suggest, the explosion must be occurring strongly along a preferred axis. The explosion must be bipolar. "These observations cannot be explained by current theory," says Wang, "so a new theory was needed."
When the core collapses, a neutron star forms before any explosion can occur. Up to now, the theory of core-collapse supernovae has been focused on the production of neutrinos that are generated within the newly formed neutron star. These ephemeral particles carry off more than a hundred times the energy required to trigger the explosion of the star. The question has been whether they carry too much and spoil the explosion, or leave enough energy behind to cause the explosion.
To help with a new theory that explains supernova formation and takes polarization into account, Wang and his Texas colleagues turned to Khokhlov, Oran, and Chtchelkanova of NRL, who used computer modeling to test scenarios that could explain the newfound polarization of these supernovae. Their models tested the idea that collapsing supernovae begin by expelling mass and energy from the new neutron star in a strongly directional process.
"Moving mass and energy in a single direction is the operational definition of a jet," says Wheeler. "These are jet-induced explosions."
If the new jet theory is right, the traditional questions about neutrinos and supernovae may be irrelevant. In their calculations, Khokhlov and his associates found that the jet punches out of the star, but also sends shock waves sideways, sharing some of the energy throughout the star. The result is that the entire star is blown up by the jet and the neutrinos do not need to play any obvious role. The ejected matter is sent out in the jet and in a pancake containing other star material. "The result is just what we need to explain the polarization," says Peter Hoeflich, a Research Scientist at the University of Texas at Austin, who is an expert on the flow of radiation from supernovae.
The numerical techniques to compute the effect of a jet on a star were developed by Khokhlov when he was at the University of Texas at Austin and have been refined and applied to this problem at the Naval Research Laboratory, where he is currently a Research Scientist. The computer code developed by Khokhlov is fully three dimensional and has an "adaptive-mesh" capability, so that it automatically computes most carefully just where the need is greatest. This code was used by Khokhlov and his colleagues to compute the propagation of a jet from near the surface of a newly formed neutron star to its eruption into space.
"The next task is to better understand the origin of the jet," says Wheeler. "The most plausible cause is the rapid rotation of the neutron star and its strong magnetic field. We have begun to look into how the newly formed neutron star can channel its energy up the rotation axis by magnetic jets or intense pulsar radiation."
For Additional Information, contact: | 0.873382 | 3.898777 |
Classical novae participate in the cycle of Galactic chemical evolution in which grains and metal enriched gas in their ejecta, supplementing those of supernovae, AGB stars, and Wolf-Rayet stars, are a source of heavy elements for the ISM. Once in the diffuse gas, this material is mixed with the existing gases and then incorporated into young stars and planetary systems during star formation. Infrared observations have confirmed the presence of carbon, SiC, hydrocarbons, and oxygen-rich silicate grains in nova ejecta, suggesting that some fraction of the pre-solar grains identified in meteoritic material come from novae. The mean mass returned by a nova outburst to the ISM probably exceeds ∼ 2 × 10-4 M⊙. Using the observed nova rate of 35±11 per year in our Galaxy, it follows that novae introduce more than ∼ 7 × 10-3 M⊙ yr -1 of processed matter into the ISM. Novae are expected to be the major source of 15N and 17O in the Galaxy and to contribute to the abundances of other isotopes in this atomic mass range. Here, we report on how changes in the nuclear reaction rates affect the properties of the outburst and alter the predictions of the contributions of novae to Galactic chemical evolution. | 0.852686 | 3.736092 |
Crescent ♌ Leo
Moon phase on 1 August 2008 Friday is New Moon, less than 1 day young Moon is in Leo.Share this page: twitter facebook linkedin
Moon rises at sunrise and sets at sunset. It's part facing the Earth is completely in shadow.
Moon is passing about ∠11° of ♌ Leo tropical zodiac sector.
Lunar disc is not visible from Earth. Moon and Sun apparent angular diameters are ∠1925" and ∠1891".
Next Full Moon is the Sturgeon Moon of August 2008 after 15 days on 16 August 2008 at 21:16.
There is high New Moon ocean tide on this date. Combined Sun and Moon gravitational tidal force working on Earth is strong, because of the Sun-Moon-Earth syzygy alignment.
At 10:13 on this date the Moon completes the old and enters a new synodic month with lunation 106 of Meeus index or 1059 from Brown series.
29 days, 9 hours and 45 minutes is the length of new lunation 106. It is 2 hours and 29 minutes shorter than next lunation 107 length.
Length of current synodic month is 2 hours and 59 minutes shorter than the mean length of synodic month, but it is still 3 hours and 10 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠39.2°. At beginning of next synodic month true anomaly will be ∠64.9°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
2 days after point of perigee on 29 July 2008 at 23:24 in ♊ Gemini. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 9 days, until it get to the point of next apogee on 10 August 2008 at 20:18 in ♐ Sagittarius.
Moon is 372 372 km (231 381 mi) away from Earth on this date. Moon moves farther next 9 days until apogee, when Earth-Moon distance will reach 404 558 km (251 381 mi).
12 days after its ascending node on 20 July 2008 at 03:27 in ♒ Aquarius, the Moon is following the northern part of its orbit for the next day, until it will cross the ecliptic from North to South in descending node on 2 August 2008 at 01:21 in ♌ Leo.
12 days after beginning of current draconic month in ♒ Aquarius, the Moon is moving from the beginning to the first part of it.
3 days after previous North standstill on 29 July 2008 at 06:17 in ♊ Gemini, when Moon has reached northern declination of ∠27.598°. Next 10 days the lunar orbit moves southward to face South declination of ∠-27.611° in the next southern standstill on 11 August 2008 at 22:13 in ♐ Sagittarius.
The Moon is in New Moon geocentric conjunction with the Sun on this date and this alignment forms Sun-Moon-Earth syzygy. | 0.837327 | 3.123685 |
June 28, 2010 report
New theory for magnetic stripes on Mars
(PhysOrg.com) -- A controversial new theory has been proposed to explain a series of stripes of permanently magnetized minerals containing iron in the Martian crust. The magnetized stripes, which have alternating orientations, have intrigued scientists since their discovery in 1997.
The Mars Global Surveyor (MGS) began orbiting almost 400 km above the surface of Mars in 1997, and its magnetometer began sending signals back to Earth, which revealed the presence of the magnetized stripes. The latest research, led by Ken Sprenke and Daisuke Kobayashi of the University of Idaho in Moscow, Idaho, theorizes the stripes were created as a result of ancient hotspots beneath the planet’s crust.
The theory, published in Icarus, is that sub-surface hotspots caused material to rise to the surface from the interior, and the mineral was then magnetized with the field present at the time. Sprenke noted that on Earth the Hawaiian Islands were probably created by hotspots moving slowly below the hard crust, leaving parallel magnetized tracks. He said there could have been dozens of hotspots in the first few hundred million years of Mars’s existence, when the molten iron in the planet’s core was probably acting as a dynamo.
The stripes form parallel arcs and are of two different types with distinctive pairs of poles, and Sprenke believes these magnetic poles, with “polar wandering” between them, represent the axis of the planet’s spin at the time. In order to explain how the crust was dragged over the hotspots, Sprenke suggests Mars may have captured some satellites early in its history, and these could have exerted a gravitational tide that would have reduced the speed of the crust relative to the hotspots beneath. As evidence for this hypothesis, Sprenke pointed out that seven of the 15 impact basins on the planet were found unexpectedly to fall along equators of the two poles fixed by the magnetic stripes.
One problem with the new theory is that there is no surface topography corresponding to the proposed hotspots. Planetary scientist John Connerney at the NASA Goddard Space Flight Center in Greenbelt, Maryland, pointed out that on Earth hotspots are associated with chains of islands or mountains, but the same thing is not seen on Mars. Sprenke suggests this may be because later volcanic activity on Mars could have eliminated the surface topography after the dynamo activity had stopped.
Connerney worked on the MGS project and has his own theory for the stripes - that the stripes were a result of ancient spreading of the sea floor - but his theory has also been criticized by planetary scientists. Detection in the 1960s of alternating magnetic stripes of rock at the bottom of the Atlantic led to theories of sea floor spreading on Earth, which in turn led to the theories of plate tectonics.
The stripes on Earth were detected by ships and were not noticed from satellites, which suggests the mystery might only be resolved when higher resolution data becomes available. This may be in 2013 when the Mars Atmosphere and Volatile EvolutioN (MAVEN) reaches Mars, carrying two magnetometers. MAVEN will gather data for several years and may fly at only 150 km above the surface for at least some of the time. If it does, the quality of data on the magnetized surface would be much improved.
© 2010 PhysOrg.com | 0.831202 | 3.716008 |
Astronomers find that some stars have a rhythmic pulsing not unlike a heartbeat. The fucking Cosmos pulses, yo!
Fucking astronomer wizards have done it again, folks. They’ve long been puzzled by the rhythmic pulses of a certain type of star, and now they’ve finally been able to cut through all the noise. To discover! Their beating hearts! Okay, okay. Not literally, but this is dope.
Astronomers have long been puzzled by the rhythmic pulsations of a certain type of stars. But now for the first time, they’ve been able to cut through the cosmic background noise of the universe to discover their “beating hearts.”
For the past few decades, astronomers have attempted to hear the pulsations from a class of stars known as “delta Scuti.” New data from NASA’s Transitioning Exoplanet Survey Satellite (TESS) reveals these exact patterns from the insides of dozens of nearby stars, according to a study published this week in the journal Nature.
“Previously we were finding too many jumbled up notes to understand these pulsating stars properly,” lead author Professor Tim Bedding from the University of Sydney said in a press release. “It was a mess, like listening to a cat walking on a piano.”
Delta Scuti stars, named after a star in the constellation Scutum, are young, rapidly-rotating stars that are about 1.5 to 2.5 times the mass of the sun. While researchers were aware that these stars can pulsate, they had not yet previously been able to detect any clear patterns in the beats.
After looking at thousands of stars, the research team found 60 — which range from about 60 to 1,400 light-years away from Earth — with shockingly regular high-frequency pulsations that are essentially like beating hearts. One of the stars studied, beta Pictoris, is just 60 light-years from Earth and visible to the naked eye from Australia.
“The incredibly precise data from NASA’s TESS mission have allowed us to cut through the noise. Now we can detect structure, more like listening to nice chords being played on the piano,” Bedding said.
These elusive pulsations, caused by energy being stored and released within the star, fall into two major categories. Some of them occur as the entire star symmetrically expands and contracts, while others occur as opposite sides alternatively expand and contract, appearing to astronomers as changes in brightness.
The scientists noted that some of the stars they studied are surprisingly close to one another. “Our results show that this class of stars is very young and some tend to hang around in loose associations. They haven’t got the idea of ‘social distancing’ rules yet,” Bedding said.
Researchers said the asteroseismological discovery is like getting to look inside a star and see what it’s made of. Their findings could help explain the inner workings of billions of stars across the universe.
“Over periods of time, variations in the data reveal intricate — and often regular — patterns, allowing us to stare into the very heart of the massive nuclear furnaces that power the universe,” researchers said.
Asteroseimological findings like this one will not only help researchers understand the insides of distant stars, but also those of our own sun. In the hunt for dark matter, studying the sun’s temperature, chemical make-up and production of neutrinos plays an important role.
“The more we know about stars, the more we learn about their potential effects on their planets,” said co-author and PhD student Isabel Colman. | 0.811837 | 3.567243 |
|San José State University|
& Tornado Alley
Retrograde Rotation of Venus
The Solar System is a wonderously regular system. From a viewpoint high above the North Pole of the Sun the planet and their satellites are generally rotating and revolving about the Sun in a counterclockwise direction. Most of the planets of the Solar System formed near the resonance orbits; i.e., where the period of revolution about the Sun is one half or two-fifths of the period of the next planet beyond it. Most of the planet have periods of rotation between ten and twenty-four hours.
There are a few anomalies. Some satellites and the planet Venus rotate in the opposite direction. The period of rotation for Venus is 243 days. What is investigated here is a plausible explanation for the retrograde rotation of Venus and the enormously long period of rotation.
Consider the following scenario. Suppose in the region where Venus is now two planetoids formed; one near the 0.4 resonance orbit and one near the 0.5 resonance orbit. Here everything is measured relative to Earth's orbit radius and orbit period. (These are called Astronomical Units (A.U.).)
By Kepler's Law, R=T2/3, the radii corresponding to these orbit periods are 0.42/3=0.543 and 0.52/3=0.630 .
The tangential velocities of the two planetoids would then be 2π(0.543)/0.4=8.5294 and 2π(0.630)/0.5=7.9168. When the two planetoids were adjacent to each they would appear to be rotating in a clockwise direction with respect to their center of mass (C.M.). Clockwise rotation is retrograde.
The difference (0.6126) is their tantgential velocities would rate of rotation ω times the difference in their orbital radii (0.870).
This means that it takes 2π/7.0414 Earth years to complete one rotation of the two planetoid system. This is 0.8923 of an Earth year or 326 days. The actual period of rotation of Venus is 243 days.
When the planetoids merge their surfaces are moving on opposite directions. It is a head-on collision of their surfaces. An enormous amount of energy must be dissipated as heat. The material of the planetoids would melt. The initial counterclockwise rotations of the planetoid would be cancelled. The collapsed system would be left with a clockswise rotation at a relatively slower rate. This is qualitatively what Venus has. The scenario establishes retrograde rotation as a consequence of the merger of nearby planets. This makes plausible the origin of Venus as the merger of two smaller planetoids in nearby orbits.
HOME PAGE OF Thayer Watkins | 0.835453 | 3.686234 |
Gravitational waves are ripples in space-time (the fabled “fabric” of the Universe) caused by massive objects moving with violent accelerations (in outer space that means objects like neutron stars or black holes orbiting around each other at ever increasing rates, or stars that blow themselves up). Explore the links below to learn more about these ephemeral phenomena.
Gravitational waves are ‘ripples’ in the fabric of space-time caused by some of the most violent and energetic processes in the Universe. Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity. Einstein’s mathematics showed that massive accelerating objects (such as neutron stars or black holes orbiting each other) would disrupt space-time in such a way that ‘waves’ of distorted space would radiate from the source (like the movement of waves away from a stone thrown into a pond). Furthermore, these ripples would travel at the speed of light through the Universe, carrying with them information about their cataclysmic origins, as well as invaluable clues to the nature of gravity itself.
The strongest gravitational waves are produced by catastrophic events such as colliding black holes, the collapse of stellar cores (supernovae), coalescing neutron stars or white dwarf stars, the slightly wobbly rotation of neutron stars that are not perfect spheres, and the remnants of gravitational radiation created by the birth of the Universe itself.
Though gravitational waves were predicted to exist in 1916, actual proof of their existence wouldn’t arrive until 1974, 20 years after Einstein’s death. In that year, two astronomers working at the Arecibo Radio Observatory in Puerto Rico discovered a binary pulsar–two extremely dense and heavy stars in orbit around each other. This was exactly the type of system that, according to general relativity, should radiate gravitational waves. Knowing that this discovery could be used to test Einstein’s audacious prediction, astronomers began measuring how the period of the stars’ orbits changed over time. After eight years of observations, it was determined that the stars were getting closer to each other at precisely the rate predicted by general relativity. This system has now been monitored for over 40 years and the observed changes in the orbit agree so well with general relativity, there is no doubt that it is emitting gravitational waves. For a more detailed discussion of this discovery and work, see Look Deeper.
That was the case up until September 14, 2015, when LIGO, for the first time, physically sensed distortions in spacetime itself caused by passing gravitational waves generated by two colliding black holes nearly 1.3 billion light years away! LIGO and its discovery will go down in history as one of the greatest human scientific achievements.
Lucky for us here on Earth, while the origins of gravitational waves can be extremely violent, by the time the waves reach the Earth they are millions of times smaller and less disruptive. In fact, by the time gravitational waves from the first detection reached LIGO, the amount of space-time wobbling they generated was thousands of times smaller than the nucleus of an atom! Such inconceivably small measurements are what LIGO was designed to make. To find out how LIGO can achieve this task, visit LIGO’s Interferometer. | 0.804476 | 4.222471 |
Assembling data gathered by eight radio telescopes around the world, astronomers created the picture showing the violent neighborhood around a supermassive black hole, the light-sucking monsters of the universe theorized by Einstein more than a century ago and confirmed by observations for decades.
It looked like a flaming orange, yellow and black ring.
"We have seen what we thought was unseeable. We have seen and taken a picture of a black hole. Here it is," said Sheperd Doeleman of Harvard.
Jessica Dempsey, a co-discoverer and deputy director of the East Asian Observatory in Hawaii, said it reminded her of the powerful flaming Eye of Sauron from the "Lord of the Rings" trilogy.
Unlike smaller black holes that come from collapsed stars, supermassive black holes are mysterious in origin. Situated at the center of most galaxies, including ours, they are so dense that nothing, not even light, can escape their gravitational pull. This one's "event horizon" - the point of no return around it, where light and matter begin to fall inexorably into the abyss - is as big as our entire solar system.
Three years ago, scientists using an extraordinarily sensitive observing system heard the sound of two much smaller black holes merging to create a gravitational wave, as Albert Einstein predicted. The new image, published in the Astrophysical Journal Letters and announced around the world in several news conferences, adds light to that sound.
Outside scientists suggested the achievement could be worthy of a Nobel Prize, just like the gravitational wave discovery.
While much around a black hole falls into a death spiral and is never to be seen again, the new image captures "lucky gas and dust" circling at just far enough to be safe and seen millions of years later on Earth, Dempsey said.
Taken over four days when astronomers had "to have the perfect weather all across the world and literally all the stars had to align," the image helps confirm Einstein's general relativity theory, Dempsey said. Einstein a century ago even predicted the symmetrical shape that scientists just found, she said.
"It's circular, but on one side the light is brighter," Dempsey said. That's because that light is approaching Earth.
The measurements are taken at a wavelength the human eye cannot see, so the astronomers added color to the image. They chose "exquisite gold because this light is so hot," Dempsey said. "Making it these warm gold and oranges makes sense."
What the image shows is gas heated to millions of degrees by the friction of ever-stronger gravity, scientists said. And that gravity creates a funhouse effect where you see light from both behind the black hole and behind you as the light curves and circles around the black hole itself, said astronomer Avi Loeb, director of the Black Hole Initiative at Harvard. (The lead scientists in the discovery are from Harvard, but Loeb was not involved.)
The project cost $50 million to $60 million, with $26 million of that coming from the National Science Foundation.
Johns Hopkins astrophysicist Ethan Vishniac, who was not part of the discovery team but edits the journal where the research was published, pronounced the image "an amazing technical achievement" that "gives us a glimpse of gravity in its most extreme manifestation."
He added: "Pictures from computer simulations can be very pretty, but there's literally nothing like a picture of the real universe, however fuzzy and monochromatic."
"It's just seriously cool," said John Kormendy, a University of Texas astronomer who wasn't part of the discovery team. "To see the stuff going down the tubes, so to speak, to see it firsthand. The mystique of black holes in the community is very substantial. That mystique is going to be made more real."
There is a myth that says a black hole would rip you apart, but Loeb and Kormendy said the one pictured is so big, someone could fall into it and not be torn to pieces. But the person would never be seen from again.
Black holes are "like the walls of a prison. Once you cross it, you will never be able to get out and you will never be able to communicate," Loeb said.
The first image is of a black hole in a galaxy called M87 that is about 53 million light years from Earth. One light year is 5.9 trillion miles, or 9.5 trillion kilometers. This black hole is about 6 billion times the mass of our sun.
The telescope data was gathered by the Event Horizon Telescope two years ago, but it took so long to complete the image because it was a massive undertaking, involving about 200 scientists, supercomputers and hundreds of terabytes of data delivered worldwide by plane.
The team looked at two supermassive black holes, the M87 and the one at the center of our own Milky Way galaxy. The one in our galaxy is closer but much smaller, so they both look the same size in the sky. But the more distant one was easier to take pictures of because it rotates more slowly.
"We've been hunting this for a long time," Dempsey said. "We've been getting closer and closer with better technology."
The South Pole Telescope, which is operated by the University of Chicago, is one of the radio telescopes used. That Antarctica-based device wasn't in a position to capture the historic image, but scientists said it has contributed to an almost-completed effort to create similar pictures of a black hole in our own galaxy, the Milky Way.
"You work a long time to do these measurements... it's pretty remarkable," said University of Chicago's Bradford Benson, an assistant professor of astronomy and astrophysics, who is part of the Event Horizon Telescope team.
WLS-TV contributed to this report. | 0.893581 | 3.913817 |
In the evening hours of late winter and early spring in the northern mid-latitudes like Ontario, the constellation Orion is a very familiar friend. The brightest star in Orion, Betelgeuse, is itself endlessly fascinating.
If you can picture the constellation then you can find Betelgeuse right away. It’s the orange-shaded bright star at the “right shoulder” of Orion – or on the left as we see the asterism. The other stars in Orion don’t have a noticeable colour most of the time, but Betelgeuse is decidedly reddish-orange.
Betelgeuse has been known as an interesting star since antiquity, but what astronomers have learned in the past 20 or more years make it all the more fascinating. For one thing, we don’t know how far away it is too much in the way of accuracy. Betelgeuse is relatively close to earth – somewhere between 400 and 700 light years away, or only about half as far as the Great Nebula in Orion, which we see with our naked eyes as the third “star” in the sword hanging from Orion’s belt. The lack of accuracy is no indication of lack of trying. For stars of this distance, astronomers often use a triangulation method called parallax to work out distances. Betelgeuse is hard to pin down this way because it is not in fact a “point” of light in the sky. The star is so big and so close that it actually has been photographed as a disk by the Hubble Space Telescope in 1995 (Gilliland & Dupree. 1996). It has a complex outer envelope that is changing its size and shape, and makes the parallax method no better than about 1 part in 5 for accuracy. The star is about 640 light years away, but that’s plus & minus 140 light years!
The size of this star is also staggering. Its diameter is approximately the same as the diameter of the orbit of Saturn in our own solar system. It’s also shining about 100,000 times as bright as our own sun. It’s likely a relatively young star compared to our own sun, and some time in the near future (in astronomical terms) it will likely explode as a supernova.
Recent scientific papers on Betelgeuse have gathered together more observations of the star itself and have tried to interpret various areas that look brighter to us as either bright patches on a darker background, or possibly as bright areas areas showing up through overlaying dark features.
This star is also moving quickly toward a linear “wall” of material that is part of the local stellar environment. Betelgeuse has a shell of glowing material thought to be part of the material blown off of the surface of the star in the past. This shell will hit the wall in about 5,000 years, followed by the star itself about 12,000 years later (Decin et al. 2012). Don’t wait up for it.
Decin et al. 2012. The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed by Herschel. I. Evidence of clumps, multiple arcs, and a linear bar-like structure. Astronomy and Astrophysics 548, A113 (http://www.aanda.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/aa/full_html/2012/12/aa19792-12/aa19792-12.html).
Gilliland & Dupree. 1996. HST imaging of Betelgeuse. Stellar surface structure: proceedings of the 176th Symposium of the International Astronomical Union, held in Vienna, Austria, October 9-13, 1995. Edited by Klaus G. Strassmeier and Jeffrey L. Linsky. International Astronomical Union. Symposium no. 176, Kluwer Academic Publishers, Dordrecht, p.165 (http://adsabs.harvard.edu/full/1996IAUS..176..165G)
Copyright © 2013 David Allan Galbraith | 0.939665 | 3.887043 |
In Canis Major, nearly 12,000 light years from Earth, lies an emission nebula that always makes me think of a particular comic book character. NGC 2359 is 30 light years across, and is colloquially known as Thor’s Helmet.
The complex structure of Thor’s helmet consists of bubbles and filaments, and is due to a series of bursts from the massive star HD 56925. This star is a rare Wolf-Rayet star, which consistently expels its outer layers of gas at high velocities, and is characterized by its very high temperature.
The blue bubble in the above image is a result of the XMM-Newton X-ray telescope. The X-rays trace the hottest bubble of gas plasma in the nebula, reaching 2 million degrees as a result of the shock waves of stellar wind. The rest of the image, the red and green filaments, result from optical measurements, tracing the glow of ionized Hydrogen and Oxygen.
As with most astronomical images, this view could not be seen with human eyes, as it combines different parts of the spectrum. But at the same time, techniques in imaging can allow a human brain to study the interactions of the hot and cool gas to determine how the central star is behaving, and how the local interstellar medium is structured. | 0.848619 | 3.084208 |
Exoplanets, i.e. planets that orbit stars beyond our solar system, play a special role in the search for extraterrestrial life. So far, a little more than 4,000 exoplanets are known, however, none has been habitable for human or human-like life. About 96 percent of these exoplanets are significantly larger than Earth and are more of the size of gas giants like Neptune or Jupiter. Still, scientists assume that this percentage does not reflect the real conditions in space, since large planets are much easier to detect than small ones.
Researchers at the Max Planck Institute for Solar System Research (MPS), the Georg August University of Göttingen and the Sonneberg Observatory have now discovered 18 exoplanets that are only about the size of the Earth – in cosmic dimensions, quite small. Therefore, they have also been overlooked in previous searches for other exoplanets.
Earth-like planet with conditions friendly to life
One of these exoplanets that have recently been discovered is even one of the smallest ever known, only 69 percent of the size of the Earth. The largest is hardy more than twice the Earth’s radius. And in addition to the fact that all 18 planets could not been detected with data from the Kepler Space Telescope before, they feature one more very special trait: one planet could even offer conditions friendly to life.
The latest discovery was made thanks to a new, more sensitive method developed by the researchers themselves, which they used to re-analyze a part of the data from NASA’s Kepler Space Telescope. After the preliminary completion of the evaluations, the group estimates that more than 100 additional exoplanets could be found this way in the Kepler mission’s entire data set.
Previously, astronomers usually used the so-called transit method in their search for distant worlds. They look for stars with periodically recurring drops in brightness, because every time an exoplanet orbits in front of its star, it occults a small fraction of the stellar light. As a result, the star appears less bright for a few hours.
Traditional transit method too inaccurate
“Standard search algorithms attempt to identify sudden drops in brightness,” explains Dr. Rene Heller from MPS, first author of the current publications. “In reality, however, a stellar disk appears slightly darker at the edge than in the center. When a planet moves in front of a star, it therefore initially blocks less starlight than at the mid-time of the transit. The maximum dimming of the star occurs in the center of the transit just before the star becomes gradually brighter again.”
As for large planets, they produce deep and clear brightness variations of their host stars so that this subtle difference plays only a subordinate role in their discovery. With small planets the situation is quite different. Their effect on the stellar brightness is so small that it is hardly noticeable and difficult to distinguish from the natural brightness fluctuations of the star and from the noise that necessarily comes with any kind of observation.
However, the German team has now been able to show that the sensitivity of the transit method can be significantly improved, if a more realistic light curve is assumed in the search algorithm. The researchers used data from NASA’ Kepler Space Telescope to test their new algorithm. In the first mission phase from 2009 to 2013, the telescope recorded the light curves of more than 100,000 stars and discovered more than 2,300 planets this way. Despite a technical defect, it had monitored more than 100,000 additional stars by the end of the mission in 2018.
In order to test the potential of their new algorithm, the researchers decided to re-analyze all 517 stars from K2 that were already known to host at least one transiting planet. They found 18 more planets that had been overlooked so far.
Significant step forward in the search for Earth-like planets
“In most of the planetary systems that we studied, the new planets are the smallest,” co-author Kai Rodenbeck of the University of Göttingen and MPS describes the results. In addition, most of the new planets would orbit their star closer than previously known planets. Due to this closer orbit, the surface temperatures of almost all these new planets would be well over 100 degrees Celsius; some even reach temperatures of up to 1000 degrees Celsius.
But there is one exception: one planet orbits its red dwarf star within the so-called habitable zone and may therefore offer conditions under which liquid water could occur on its surface – one of the basic prerequisites for life as we know onEarth. “Our new algorithm helps to draw a more realistic picture of the exoplanet population in space,” summarizes Michael Hippke of Sonneberg Observatory. “This method constitutes a significant step forward, especially in the search for Earth-like planets.”
Although they have discovered the 18 previously unknown planets with this new method, the researchers do not want to rule out that they could still have overlooked other planets. For example, there could be other small planets orbiting their stars at large distances and therefore taking longer to complete a full orbit than planets orbiting their stars closer in. Therefore, the transits of planets in wide orbits would occur less often and their already weak signals would be even harder to detect.
The new method developed by René Heller and his team could soon lead to more fascinating discoveries, because the Kepler mission still offers data sets of hundreds of thousands of other stars. The scientists therefore assume that they will be able to find more than 100 more Earth-sized worlds. “This new method is also particularly useful to prepare for the upcoming PLATO mission to be launched in 2026 by the European Space Agency,” says Prof. Dr. Laurent Gizon, Managing Director at the MPS. PLATO will launch into space in 2026 and and characterize many more multi-planet systems around Sun-like stars, some of which will be capable of harboring life.
The results of the studies were published in the journal Astronomy & Astrophysics.
Asteroids Help to Calculate the Size of Distant Stars
Einstein was Right After All: First Picture of a Black Hole
The Milky Way Weighs 3 000 000 000 000 000 000 000 000 000 000 000 000 000 TONS
ESO’s VLT Shows Bubbles of Brand New Stars
Hubble Discover the Brightest Quasar in the Early Universe
Hubble Find More Evidence for Moon Outside our Solar System | 0.936855 | 3.964924 |
Princeton astronomer recalls a once-in-a-lifetime star sighting
On Jan. 9, 2008, Alicia Soderberg, a postdoctoral research associate in astrophysics at Princeton, was studying the X-ray emissions conveyed from space by NASA's Swift satellite when she recognized an extremely bright light on the screen of her computer, saturating the satellite's view "as if we had pointed a digital camera directly at the sun." That light, Soderberg and colleague Edo Berger later confirmed, was a supernova â an explosion of a massive star. Seeing a supernova is not unusual â the stars are brighter than 100 billion suns. But in the vastness of space, there generally is a delay of days or weeks between a supernova's explosion and its discovery by astronomers. By then, "most of the fireworks are already over," Soderberg said. Soderberg is the first astronomer to observe a supernova in the act of exploding. Her finding, named Supernova 2008D, is described in a paper to be published in Nature May 22, and in a May 21 teleconference, she described the experience as being at the right place, at the right time, with the right telescope. "I truly won the astronomer's lottery," she said. Soderberg had been studying another supernova, SN 2007uy, in the spiral galaxy NGC 2770, located 90 million light years from Earth in the constellation Lynx. Seeing two supernovae in the same galaxy in a matter of weeks is extraordinarily unusual â a one-in-10,000 chance, she estimates. A typical galaxy produces one supernova every 100 years. The Princeton group's discovery sparked a campaign of observations from telescopes in the United States and beyond, including the Hubble Space Telescope. The use of an X-ray flash, rather than optical observation, to detect a supernova marks a "paradigm shift" and could lead to more discoveries, according to Robert Kirshner, a professor of astronomy at Harvard University and one of Soderberg's mentors. Kirshner also stressed that luck was only part of Soderberg's find. "If you're active and you're energetic, it helps a lot because you manufacture your own luck, in a way," he said. "There's nobody who's more focused and energetic than Alicia Soderberg."
Courtesy of NASA/Swift/Skyworks Digital/Dana Berry
This digital animation shows an artist's rendering of the shock wave discovered by Princeton University's Alicia Soderberg and a team of scientists. A supernova is born when the core of a massive star (the blue orb) runs out of nuclear fuel and collapses under its own gravity to form an ultradense object known as a neutron star. The shock wave erupts and ripples through the star, emitting X-rays (seen here as bright white light). The remnants of the explosion cool (the white light gets smaller), and then the visual light from the supernova glows (seen as yellow clouds). The fading white dot in the middle of the animation represents a newly born neutron star.
Correction: An earlier version of this post misstated the frequency at which supernovae occur in a galaxy. It is about once every 100 years.
Down and up, 1,000 times
On May 5, with his hands pressed against the hardwood of the Princeton Seminary gym, Ryan Bonfiglio ’01 completed 1,000 push-ups in 20 minutes and 50 seconds, besting a mark from The Guinness Book of World Records set by fitness guru Jack LaLanne on the national television show You Asked For It in 1956.
The high-speed push-ups, completed in sets of 25, were recorded by a digital camera that also captured Bonfiglio's "official timer" - a wristwatch positioned on the floor. Bonfiglio, a former Princeton wrestler, is not new to breaking world records. In 2004, he set the record for most pull-ups in one hour: 507. That record was broken when a competitor chinned-up over 600 times in 60 minutes. Bonfiglio contested the mark, arguing that chin-ups and pull-ups use different muscles and therefore are different exercises, but the Guinness Book officials were firm in their refusal to differentiate. LaLanne's "quickest completion of 1,000 push-ups" category has been retired by the The Guinness Book of World Records, so Bonfiglio is looking to challenge a related mark: most push-ups in one hour. Record-holder Roy Berger, a Canadian who was proclaimed "Mr. Push-up" by Muscle & Fitness Magazine, completed 3,416 push-ups in an hour in 1998. Photo courtesy of Benjamin Robinson
Names in the News
With the Boston Celtics rolling toward the NBA's Eastern Conference finals, ESPN told the story of how Celtics CEO Wyc Grousbeck ’83 came back home to Boston and stepped into one of the most cherished corner offices in town. ... Wendy Kopp ’89's Teach for America continues to grow, according to a recent AP report, and Kopp expects even more expansion in the next two years, as the group aims to increase its corps of first- and second-year teachers from 5,000 to 8,000. ... Princeton musicologist Simon Morrison *97 is helping to revive Prokoviev's ballet "Romeo and Juliet" for a series of July performances at Bard College. ... Two hundred years ago, China was the world's greatest economic power, Princeton economics professor Burton Malkiel *64 told CFAs at a recent conference. Malkiel expects that China will regain that position in the next 20 years. ... William Zinsser ’44 wrote a May 18 New York Times essay about the most peculiar Manhattan office he ever occupied and its most memorable perk: a fireman's pole that connected the fifth and fourth floors. | 0.852285 | 3.603955 |
NASA likes to do things gradually, building knowledge as it goes along. Each step provides information used in building the next probe.
The evolution goes something like this:
- Flyby. Initial reconnaissance of a planet. Gather information on e.g. the local radiation environment, and other potential obstacles for an orbiter mission.
- Orbiter. Detailed surface mapping to help plan a lander mission.
- Lander. More details on surface composition to help plan a rover mission.
Each step costs more than the previous one. So only the most interesting targets have rovers sent to them.
There are other factors. Sending an orbiter to Pluto wasn't possible in the timeframe of the New Horizons launch: an orbiter would need a much heavier rocket than was available at the time. NH was hurried to launch because scientists had discovered Pluto has an atmosphere at the moment, and predictions were this atmosphere would collapse somewhere between 2014 and 2020, the probe had to arrive before this happened.
Because Pluto's so small and doesn't have a dense atmosphere, all braking must be done using rocket fuel. So either:
you launch at a low speed to reduce the delta-V for getting into Pluto orbit. This means the orbiter takes very long to get there (wild guess: at least 30 years instead of 9). Keeping a science team together for that long is difficult.
or you launch a probe with a huge fuel tank and engine, and you need two SLS or Saturn V to get that off the ground. This means 20 times the launch cost of New Horizons.
New Horizons goes through the Pluto system at a relative velocity of 11 km/s.
This Slashdot post contains an interesting calculation of launch weight for an orbiter:
The Space Shuttle Main Engines, one of our most efficient rocket engines, has an Isp of 4.436 km/s. By the rocket equation [this means that, to change velocity by 11 km/s using this engine, a spacecraft would need a ratio of wet mass to dry mass of exp(11/4.436) = 11.9. In other words, to stop the New Horizons probe at Pluto, we'd need to have sent along an extra 10.9 times its mass in fuel. And that's ignoring the mass of the engine and tankage, which makes things worse.
Fuel boil-off... is an additional problem: it means we couldn't use the liquid-hydrogen/liquid-oxygen propellant used by the SSMEs, but some more stable (and less efficient) propellant, which further increase the required fuel mass.
...New Horizons was launched on an Atlas V 551, which has a capacity of 19t to LEO. To send the probe plus 10.9 times its mass in fuel would therefore take an equivalent capacity of ~11.9*19 = 226t to LEO. The Saturn V, the most powerful launcher ever made, had a capacity of 118t to LEO. So you'd need two Saturn V launches, rendesvousing in orbit, to get a spacecraft with enough fuel to fly to Pluto and stop there. (Probably 3-4 launches, when you consider the other problems described above.)
The Pioneer and Voyager missions had similar constraints. No knowledge at all of space beyond Mars' orbit, budget limits because of the Apollo project.
Your initial premise is also off. We've had some high-profile flyby missions, but much more money has been spent on orbiters (Cassini, various Mars orbiters, Rosetta), landers (Viking) and rovers (Curiosity is several times more expensive than New Horizons).
Voyager and New Horizons are just the tip of the iceberg. 47 orbiters and landers, 43 flyby missions, with some overlap in that list (Rosetta is counted as both a flyby and an orbiter, for instance). | 0.838612 | 3.522543 |
Just over a month ago, scientists working on the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) observatory at Haleakala, Hawaii caught a glimpse of something truly extraordinary: the first known interstellar object to pass through the solar system. Over the past month, we’ve refined observations and detailed what we could make of the object. Now known as 1I/2017 U1 ‘Oumuamua, it’s the first object of its kind. The “I” denotes its interstellar origin (ISO).
‘Oumuamua plunged into the solar system as if dropped into it from above, closing to within 0.25 AU from the sun. That puts it between the orbit of the sun and Mercury, but there was no hint of a “tail” as ‘Oumuamua approached. On its initial approach from “above” the solar system, the asteroid was moving at a solid 15.8 miles per second (25.5km/s). It bottomed out “under” the solar system after the sun’s gravity pulled it into a different orbit, and is now on its way back out of the solar system on a different trajectory and an even higher speed (44km/s).
`Oumuamua is rapidly fading as it heads out of the Solar System and recedes from both the Sun and the Earth, so getting new observations as fast as possible was crucial. “The IfA team — including those who discovered 1I — was already prepared to rapidly follow up solar system discoveries from Pan-STARRS, which is operated by the IfA and funded by NASA,” said Karen Meech, the astronomer who led the investigative team. “We were able to rapidly develop a follow-up strategy on a very short timescale. It is exciting to think that the brief visit by `Oumuamua gave us the opportunity to do the first characterization of a sample from another solar system.”
Based on its observed characteristics, ‘Oumuamua is roughly cigar shaped, with two of its axes about 80 meters across and the third 800 meters long. Its trajectory and speed suggest it’s not an ejected fragment of our own solar system at any previous stage in its development. While this possibility cannot be completely ruled out, the research team seems to think it’s a distant possibility. In fact, they theorize that its encounter with our own sun may have been the first time ‘Oumuamua encountered another star at all.
The entire encounter, brief as it has been, reminds us of Arthur C. Clarke’s classic sci-fi book, Rendezvous with Rama, in which a massive cylindrical spacecraft on a fast approach inside our own solar system is explored by humans before it continues on its journey towards the Large Magellanic Cloud. We won’t see ‘Oumuamua again, but its brief visit to our solar system expanded our understanding of the cosmos, just a bit.
Feature image by ESO/M. Kornmesser . | 0.8458 | 3.991471 |
Scientists are repainting Jupiter’s portrait — scientifically, anyway. NASA’s Juno spacecraft swooped within 5,000 kilometers (3,100 miles) of Jupiter’s cloud tops last August 27. Scientists’ first close-up of the gas giant has unveiled several unexpected details about the planet’s gravity and powerful magnetic fields. They also give a new view of the planet’s auroras and ammonia-rich weather systems.
Researchers need to revamp their view of Jupiter, these findings suggest. They even challenge ideas about how solar systems form and evolve. The findings come from two papers published May 26 in Science.
“We went in with a preconceived notion of how Jupiter worked,” says Scott Bolton. “And I would say we have to eat some humble pie.” Bolton is a planetary scientist who leads the Juno mission. He works at the Southwest Research Institute in San Antonio, Texas.
Scientists thought that beneath its thick clouds, Jupiter would be uniform and boring. Not anymore. “Jupiter is much more complex deep down than anyone anticipated,” Bolton now observes.
One early surprise came from Jupiter’s gravity. Juno measured that gravity from its tug on the spacecraft. The values suggest that Jupiter doesn’t have a solid, compact core. Instead, the core is probably large and diffuse. It could even be as big as half the planet’s radius, Bolton and his colleagues conclude. “Nobody anticipated that,” Bolton notes.
Imke de Pater is a planetary scientist. She works at the University of California, Berkeley and was not involved in the new studies. The new gravity measurements should lead to a better understanding of the planet’s core, she says. But, she adds, doing so will require using some challenging math.
She was more surprised by Jupiter’s magnetic field. It is the strongest of any planet in our solar system. And Juno’s data show that it is almost twice as strong as expected in some spots. Its strength varies. It gets stronger than expected in some areas, weaker in others. These data support the idea that this magnetic field originates from circulating electric currents. Those currents are probably in one of the planet’s outer layers of hydrogen.
Responding to the ‘wind’
A second study looked at how Jupiter’s magnetic field interacts with a stream of charged particles flowing from the sun. Known as the solar wind, these particles affects Jupiter’s auroras, points out John Connerney. An astrophysicist, he led this study with colleagues at NASA’s Goddard Space Flight Center in Greenbelt, Md.
Auroras are brilliant shows of colored light that appear at or near a planet’s poles. (Earth’s auroras are known as the Northern and Southern Lights.) Juno captured Jupiter’s auroras in ultraviolet and infrared light. These images come from wavelengths beyond what the human eye can see. They showed particles falling into the planet’s atmosphere. That is similar to what happens on Earth. But they also showed beams of electrons shooting out from Jupiter’s atmosphere. Nothing like that occurs on Earth.
Bolton’s team described another oddity. Ammonia wells up from the depths of Jupiter’s atmosphere in a strange way. This upwelling resembles a feature on Earth called a Hadley cell. Warm air at our equator rises and creates trade winds, hurricanes and other forms of weather. Jupiter’s ammonia cycling looks similar to this. But Jupiter lacks a solid surface, the researchers note. So the upwelling likely works in a completely different way than on Earth. The scientists hope to figure out how this works on Jupiter. This could help scientists better understand the atmospheres of such huge gas planets.
Explains Bolton, Jupiter is a standard of comparison for all gas giants — both within and beyond our solar system. Most planetary systems have Jupiter-like planets. He says that means researchers can apply what they learn about Jupiter to giant planets elsewhere. | 0.863065 | 3.829954 |
eso1048 — Photo Release
A Swarm of Ancient Stars
8 December 2010
We know of about 150 of the rich collections of old stars called globular clusters that orbit our galaxy, the Milky Way. This sharp new image of Messier 107, captured by the Wide Field Imager on the 2.2-metre telescope at ESO’s La Silla Observatory in Chile, displays the structure of one such globular cluster in exquisite detail. Studying these stellar swarms has revealed much about the history of our galaxy and how stars evolve.
The globular cluster Messier 107, also known as NGC 6171, is a compact and ancient family of stars that lies about 21 000 light-years away. Messier 107 is a bustling metropolis: thousands of stars in globular clusters like this one are concentrated into a space that is only about twenty times the distance between our Sun and its nearest stellar neighbour, Alpha Centauri, across. A significant number of these stars have already evolved into red giants, one of the last stages of a star’s life, and have a yellowish colour in this image.
Globular clusters are among the oldest objects in the Universe. And since the stars within a globular cluster formed from the same cloud of interstellar matter at roughly the same time — typically over 10 billion years ago — they are all low-mass stars, as lightweights burn their hydrogen fuel supply much more slowly than stellar behemoths. Globular clusters formed during the earliest stages in the formation of their host galaxies and therefore studying these objects can give significant insights into how galaxies, and their component stars, evolve.
Messier 107 has undergone intensive observations, being one of the 160 stellar fields that was selected for the Pre-FLAMES Survey — a preliminary survey conducted between 1999 and 2002 using the 2.2-metre telescope at ESO’s La Silla Observatory in Chile, to find suitable stars for follow-up observations with the VLT’s spectroscopic instrument FLAMES . Using FLAMES, it is possible to observe up to 130 targets at the same time, making it particularly well suited to the spectroscopic study of densely populated stellar fields, such as globular clusters.
M107 is not visible to the naked eye, but, with an apparent magnitude of about eight, it can easily be observed from a dark site with binoculars or a small telescope. The globular cluster is about 13 arcminutes across, which corresponds to about 80 light-years at its distance, and it is found in the constellation of Ophiuchus, north of the pincers of Scorpius. Roughly half of the Milky Way’s known globular clusters are actually found in the constellations of Sagittarius, Scorpius and Ophiuchus, in the general direction of the centre of the Milky Way. This is because they are all in elongated orbits around the central region and are on average most likely to be seen in this direction.
Messier 107 was discovered by Pierre Méchain in April 1782 and it was added to the list of seven Additional Messier Objects that were originally not included in the final version of Messier’s catalogue, which was published the previous year. On 12 May 1793, it was independently rediscovered by William Herschel, who was able to resolve this globular cluster into stars for the first time. But it was not until 1947 that this globular cluster finally took its place in Messier’s catalogue as M107, making it the most recent star cluster to be added to this famous list.
This image is composed from exposures taken through the blue, green and near-infrared filters by the Wide Field Camera (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile.
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. 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 VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
ESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591 | 0.863112 | 3.879153 |
A powerful Nasa space telescope launched in June has unveiled its first results - including an image of the sky viewed through "gamma-ray glasses".
Nasa also revealed a new name; the Gamma-ray Large Area Space Telescope has become the Fermi telescope.
The name honours Enrico Fermi - one of the pioneers of high energy physics.
Fermi will study some of the most extreme phenomena in the cosmos, which liberate massive amounts of energy in the form of gamma-rays.
It will scan the sky for massive cosmic explosions, giant black holes that hurl matter across space, and dense neutron stars with powerful magnetic fields.
In the two months since the telescope's launch, scientists have been testing and calibrating its two instruments, the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM).
Eye on the sky
The Large Area Telescope (LAT) scans the the entire sky every three hours.
During its first 95 hours of operation, the telescope generated a gamma-ray map of the sky similar to the one obtained by Nasa's now-defunct Compton Gamma-ray Observatory, which took years of observations to produce.
The gamma-ray map of the sky from the LAT's "first light" observations shows the glowing gas of the Milky Way, blinking pulsars, and a flaring galaxy billions of light-years away.
The image shows gas and dust in the plane of the Milky Way glowing in gamma-rays as a result of collisions with accelerated nuclei called cosmic rays.
Familiar landmarks include the Crab Nebula, Vela and Geminga pulsars. Pulsars are fast spinning neutron stars, emitting powerful beams of radiation that sweep across the Earth's line of sight like lighthouse beacons.
They are formed when the core of a massive star collapses and matter is squeezed so tightly that an amount of material the size of a sugar cube would weigh more than one billion tonnes - about the same as Mount Everest.
Another bright spot in the LAT image lies some 7.1 billion light-years away, far beyond our galaxy.
This is 3C 454.3 in the constellation Pegasus, a type of active galaxy called a blazar. It is now undergoing a flaring episode that makes it especially bright.
Active galaxies are galaxies with extremely luminous cores powered by monster black holes.
The spacecraft's secondary instrument, the GBM, spotted 31 gamma-ray bursts in its first month of operations. These high-energy blasts occur when massive stars die or when orbiting neutron stars spiral together and merge.
The telescope's new name honours Enrico Fermi, an Italian physicist who immigrated to the US and died in 1954.
He worked on the development of the first nuclear reactor and was awarded the Nobel Prize in Physics in 1938 for his work on radioactivity. | 0.887845 | 3.952088 |
Observations of nitrogen in Earth’s atmosphere by a NASA spacecraft over 27 million kilometres (17 million miles) away are giving astronomers fresh clues to how that gas might reveal itself on faraway planets, thus aiding in the search for life.
Finding and measuring nitrogen in the atmosphere of an exoplanet — worlds outside our Solar System — can be crucial to determining if that world might be habitable. That’s because nitrogen can provide an indication of surface pressure. If the gas is found to be abundant in a planet’s atmosphere, that world almost certainly has the right pressure to keep liquid water stable on its surface – one of the prerequisites for life.
Should life truly exist on an exoplanet, detecting nitrogen as well as oxygen could help astronomers verify the oxygen’s biological origin by ruling out certain ways it can be produced abiotically, or through means other than life.
The trouble is, nitrogen is hard to spot from afar. It’s often called an ‘invisible gas’ because it has few light-altering features in visible or infrared light that would make it easy to detect. The best way to detect nitrogen in a distant atmosphere is to measure nitrogen molecules colliding with each other. The resulting, instantaneously brief ‘collisional pairs’ create a unique and discernable signature that can be picked up by spectroscopic techniques.
According to the University of Washington’s Edward Schwieterman, together with Victoria Meadows, who is also at Washington, a future large telescope could detect this unusual signature in the atmospheres of terrestrial, or rocky planets, given the right instrumentation.
The researchers used three-dimensional planet-modelling data from the University of Washington-based Virtual Planetary Laboratory to simulate how the signature of nitrogen molecule collisions might appear in the Earth’s atmosphere, and compared this simulated data to real observations of the Earth by NASA’s unmanned Deep Impact Flyby spacecraft, which was launched back in 2005.
Deep Impact undertook a revised mission, called EPOXI, which included observation and characterisation of the Earth as if it were an exoplanet. By comparing the real data from the EPOXI mission and the simulated data from Virtual Planetary Laboratory models, the authors were able to confirm the signatures of nitrogen collisions in our own atmosphere, and that they would be visible to a distant observer.
“One of the main messages of the Virtual Planetary Laboratory is that you always need validation of an idea — a proof of concept — before you can extrapolate your knowledge to studying a potentially Earth-like exoplanet,” explains Schwieterman. “That’s why studying the Earth as an exoplanet is so important — we were able to validate that nitrogen produces an impact on the spectrum of our own planet as seen by a distant spacecraft. This tells us it’s something worth looking for elsewhere.”
This confirmation in hand, the researchers used a suite of Virtual Planetary Laboratory models that simulated the appearance of planets beyond the Solar System bearing varying amounts of nitrogen in their atmospheres.
The detection of nitrogen will help astronomers characterise the atmospheres of potentially habitable planets and determine the likelihood of oxygen production by non-living processes. “One of the interesting results from our study is that, basically, if there’s enough nitrogen to detect at all, you’ve confirmed that the surface pressure is sufficient for liquid water, for a very wide range of surface temperatures,” concludes Schwieterman. | 0.895337 | 4.044221 |
Finding it difficult to wrap your mind around the immensity of the universe? With thousands of known exoplanet candidates and billions and trillions of stars out there, things can get overwhelming. But a couple of new visualizations of space can help.
The first, produced by Harvard astronomer Alex Parker shows 2299 of the planet candidates found by the Kepler telescope. In truth, those 2299 planets orbit around 1770 stars, but Parker didn't want to overwhelm his audience with so much on screen. Instead, he animated them all orbiting a single star, to give people an idea of the range of known (potential) exoplanets. Each body is roughly the same size and circles the star at the same distance as it would in reality.
"I wanted to convey the sheer size of the sample in a way that was as visually and viscerally impacting as possible," Parker tells PM. "As part of my research, I had produced a number of simple visualizations of a variety of orbital systems, and knew that a sea of orbiting bodies could be very hypnotic."
Parker coded the visualization himself by building off his earlier animation of the 6 planets in orbit around the star Kepler 11. Originally he was hoping to sonify the transits of every Kepler-discovered planet, but the sheer size of the sample made it impossible to pull any musicality out of the din of orbiting planets. Instead, he settled for the dizzying result created by animating one, impossibly large solar system.
A second video—released last week by the Sloan Digital Sky Survey—takes you on a "flight through the Universe" past every one of the nearly 400,000 galaxies scientists have photographic evidence of today.
Incredibly, this video only represents a small part of the Universe extending only 1.3 billion light years from Earth. Some astronomers estimate that the observable universe is home to at least 100 billion galaxies, making 400,000 a drop in the galactic bucket.
More PM coverage of Kepler: | 0.883745 | 3.455156 |
By Megan Watzke
A team of astrophysicists and planetary scientists has predicted that Neptune-like planets located near the center of the Milky Way galaxy have been transformed into rocky planets by outbursts generated by the nearby supermassive black hole.
These findings combine computer simulations with data from recent exoplanet findings, and X-ray and ultraviolet observations of stars and black holes.
“It’s pretty wild to think of black holes shaping the evolutionary destiny of a planet, but that very well may be the case in the center of our Galaxy,” said Howard Chen of Northwestern University in Evanston, IL, who led the study.
Howard Chen and collaborators from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., examined the environment around the closest supermassive black hole to Earth: the four-million-solar mass black hole known as Sagittarius A*.
It is well known that material falling into the black hole in occasional feeding frenzies will generate bright flares of X-ray and ultraviolet radiation. Indeed, X-ray telescopes such as NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton have seen evidence for bright outbursts generated in the past by the black hole ranging from about 6 million years to just over a century ago.
“We wondered what these outbursts from Sagittarius A* would do to any planets in its vicinity,” said John Forbes, a co-author from the CfA. “Our work shows the black hole could dramatically change a planet’s life.”
The authors considered the effects of this high-energy radiation on planets with masses in between Earth and Neptune that are located less than 70 light years away from the black hole.
They found that the X-ray and ultraviolet radiation would blast away a large amount of the thick, gas atmosphere of such planets near the black hole. In some cases this would leave behind a bare, rocky core. Such rocky planets would be heavier than the Earth and are what astronomers call super-Earths.
“These super-Earths are one of the most common types of planet that astronomers have discovered outside our Solar System,” said co-author Avi Loeb, also of CfA, “Our work shows that in the right environment they might form in exotic ways.”
The researchers think that this black hole impact may be one of the most common ways for rocky super-Earths to form close to the center of our Galaxy.
While some of these planets will be located in the habitable zone of stars like the Sun, the environment they exist within would be challenging for any life to arise. Supernova explosions and gamma ray bursts would buffet these super-Earths, which might damage the chemistry of any atmosphere remaining on these planets. Additional outbursts from the supermassive black hole could provide a knockout punch and completely erode the planet’s atmosphere.
These planets would also be subjected to the gravitational disruptions of a passing star that could fling the planet away from its life-sustaining host star. Such encounters might occur frequently near the Milky Way’s supermassive black hole since the region is so packed with stars. How crowded is it in the Galactic Center? Within about 70 light years of the center of the Galaxy, astronomers think the average separation between rocky worlds is between about 75 and 750 billion kilometers. By comparison the nearest star to the Solar System is 40,000 billion kilometers away.
“It is generally accepted that the innermost regions of the Milky Way is not favorable for life. Indeed, even though the deck seems stacked against life in this region, the likelihood of panspermia, where life is transmitted via interplanetary or interstellar contact, would be much more common in such a dense environment,” said Loeb. “This process might give life a fighting chance to arise and survive.”
There are formidable challenges required to directly detect such planets. The distance to the Galactic Center (26,000 light years from Earth), the crowded region, and the blocking of light by intervening dust and gas all make the observation of such planets very difficult.
However, these challenges may be met by the next generation of extraordinarily large ground-based telescopes. For example, searches for transits with future observatories like the European Extremely Large Telescope might detect evidence for these planets. Another possibility is searching for stars with unusual patterns of elements in their atmosphere that have migrated away from the center of the galaxy.
A paper describing these results appeared in the February 22, 2018 issue of The Astrophysical Journal Letters and is available online. | 0.92008 | 4.021835 |
Corotation Found to be Typical, Suggesting Cool Halo Gas Prolongs Galaxy Growth
Maunakea, Hawaii – A group of astronomers led by Crystal Martin and Stephanie Ho of the University of California, Santa Barbara, has discovered a dizzying cosmic choreography among typical star-forming galaxies; their cool halo gas appears to be in step with the galactic disks, spinning in the same direction.
The researchers used W. M. Keck Observatory to obtain the first-ever direct observational evidence showing that corotating halo gas is not only possible, but common. Their findings suggest that the whirling gas halo will eventually spiral in towards the disk.
“This is a major breakthrough in understanding how galactic disks grow,” said Martin, Professor of Physics at UC Santa Barbara and lead author of the study. “Galaxies are surrounded by massive reservoirs of gas that extend far beyond the visible portions of galaxies. Until now, it has remained a mystery how exactly this material is transported to galactic disks where it can fuel the next generation of star formation.”
Nearly a decade ago, theoretical models predicted that the angular momentum of the spinning cool halo gas partially offsets the gravitational force pulling it towards the galaxy, thereby slowing down the gas accretion rate and lengthening the period of disk growth.
The team’s results confirm this theory, which show that the angular momentum of the halo gas is high enough to slow down the infall rate but not so high as to shut down feeding the galactic disk entirely.
The astronomers first obtained spectra of bright quasars behind star-forming galaxies to detect the invisible halo gas by its absorption-line signature in the quasar spectra. Next, the researchers used Keck Observatory’s laser guide star adaptive optics (LGSAO) system and near-infrared camera (NIRC2) on the Keck II telescope, along with Hubble Space Telescope’s Wide Field Camera 3 (WFC3), to obtain high-resolution images of the galaxies.
“What sets this work apart from previous studies is that our team also used the quasar as a reference ‘star’ for Keck’s laser guide star AO system,” said co-author Stephanie Ho, a physics graduate student at UC Santa Barbara. “This method removed the blurring caused by the atmosphere and produced the detailed images we needed to resolve the galactic disks and geometrically determine the orientation of the galactic disks in three-dimensional space.”
The team then measured the Doppler shifts of the gas clouds using the Low Resolution Imaging Spectrometer (LRIS) at Keck Observatory, as well as obtaining spectra from Apache Point Observatory. This enabled the researchers to determine what direction the gas is spinning and how fast. The data proved that the gas is rotating in the same direction as the galaxy, and the angular momentum of the gas is not stronger than the force of gravity, meaning the gas will spiral into the galactic disk.
“Just as ice skaters build up momentum and spin when they bring their arms inward, the halo gas is likely spinning today because it was once at much larger distances where it was deposited by galactic winds, stripped from satellite galaxies, or directed toward the galaxy by a cosmic filament,” said Martin.
The next step for Martin and her team is to measure the rate at which the halo gas is being pulled into the galactic disk. Comparing the inflow rate to the star formation rate will provide a better timeline of the evolution of normal star-forming galaxies, and explain how galactic disks continue to grow over very long timescales that span billions of years.
ABOUT ADAPTIVE OPTICS
W. M. Keck Observatory is a distinguished leader in the field of adaptive optics (AO), a breakthrough technology that removes the distortions caused by the turbulence in the Earth’s atmosphere. Keck Observatory pioneered the astronomical use of both natural guide star (NGS) and laser guide star adaptive optics (LGS AO) on large telescopes and current systems now deliver images three to four times sharper than the Hubble Space Telescope. Keck AO has imaged the four massive planets orbiting the star HR8799, measured the mass of the giant black hole at the center of our Milky Way Galaxy, discovered new supernovae in distant galaxies, and identified the specific stars that were their progenitors. Support for this technology was generously provided by the Bob and Renee Parsons Foundation, Change Happens Foundation, Gordon and Betty Moore Foundation, Mt. Cuba Astronomical Foundation, NASA, NSF, and W. M. Keck Foundation.
The Near-Infrared Camera, second generation (NIRC2) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the center of our galaxy. Astronomers also use NIRC2 to map surface features of solar system bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.
The Low Resolution Imaging Spectrometer (LRIS) is a very versatile visible-wavelength imaging and spectroscopy instrument commissioned in 1993 and operating at the Cassegrain focus of Keck I. Since it has been commissioned it has seen two major upgrades to further enhance its capabilities: addition of a second, blue arm optimized for shorter wavelengths of light; and the installation of detectors that are much more sensitive at the longest (red)wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in2011 for research determining that the universe was speeding up in its expansion.
ABOUT W. M. KECK OBSERVATORY
The W. M. Keck Observatory telescopes are the most scientifically productive on Earth. The two, 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. | 0.895469 | 4.004103 |
September 23rd is the first day of the fall season, beginning with the autumnal equinox at 4:21 AM. There are a few ways of looking at this day. First, it has been celebrated around the world from harvest time to ancient pyramid shadow alignments. This day, the sun is at the halfway point between the summer and winter solstice. For the northern hemisphere it marks the first day of fall, and an increasing drop in daily temperature as the days get shorter. But is there equal daylight? It is equal gravity? Can you stand an egg on end? Here is a look at everything I felt relevant for fellow science geeks to eat up and teachers to share with their students. This includes a few videos as well.
If we plot the angle of the mid-day sun (as seen here), the Autumnal Equinox is a day the sun’s ray’s are focused directly on the equator. With respect to the Northern Hemisphere, this angle is halfway between the highest point during the summer solstice (June 21), and the lowest point during the winter solstice (December 21). So if you were to plot how high the sun gets in the sky all year long, this day is half-way, but going lower. This change is due to the tilt of Earth on it’s axis at 23.5 degrees. So as we orbit the sun, the Northern Hemisphere either points towards or away from the sun, resulting in a higher or lower sun angle as seen in the image at the top of this post.
Why Do We Call It Fall?
This is a question now both of my boys are old enough to ask. I like to keep the options open for the young kids, so to them and during my school assemblies I say:
- The leaves begin to fall
- The temperature begins to fall
- The night begins to fall, earlier with speed this time of year.
Note: I give a similar answer for the reasons behind the name Nor’Easter: A coastal storm that
- moves towards the northeast
- heads into the Northeastern US
- and sends cool, damp northeasterly winds inland.
Sometimes more than one answer fits.
As the days get shorter and the nights get longer, the average temperature begins a drop of about one degree every two days for the rest of this month.
The weather almanac for Baltimore shows the normal high temperature today at 75F. If you were to compare that to the the other ‘equinox’ in March, the average temperature is 51F. Much cooler despite the same sun angle. This is due to seasonal lags of temperature. On any given day, the sun is highest in the sky between noon and 1 PM, but the hottest daily high would be between 3 to 5 PM. Our strongest solar rays are on June 21, but the hottest temperatures are the middle of July, weeks later. In short, there is a delayed response of warming, but also cooling. Since the ground and nearby water ways are still warm from summer, that residual heat helps delay our cooling. The upcoming longer nights will change that quickly.
Over the next 30 days, we will lose 10 degrees and expect a high of 65F by the third week of October. The cooling rate slows down a little and averages out to one degree cooler every three days.
Fall Begins: Equal Is Not Equal Sunlight
The word equinox sounds a lot like ‘equal’, and that is how it is often introduced in an earth science class. I was originally taught that it was the day when the entire planet also had equal time of daylight and darkness as well. That is not entirely true.
- Sunrise at 6:55 am, Sunset at 7:02 pm
- 12 hours and seven minutes of daylight.
Sure, the nights are getting longer. In fact this is the fastest change we can see in our region all year, as we are now losing about 3 minutes of daylight each day. But, you have to consider that light bends in our atmosphere. This image shows sunrise as seen from the International Space Station. The glow of light appearing above the sun shows how light bends around our atmosphere before you see the actual sun. Think about the red and orange sky in the morning and evening, that is a demonstration of how light bends in our atmosphere, especially at dawn and dusk. The view of the sun itself is also seen as the light bends around the horizon. So while the sun itself should be in our view for 12 hours today (splitting the time with darkness), the light of the sunlight bends in the atmosphere and gives us an extra few minutes of daylight on each end of equinox day.
Push forward three days to September 26
- Sunrise at 6:58 am, Sunset at 6:57 pm
- 11 hours and 59 minutes of sunlight, 12 hours and 1 minute of darkness. Nighttime will win.
The coolest thing seen in space: Sunrise from NASA and ISS
Stand An Egg On End? Some teachers in my High School tried to convince the class that the equal force of the sun’s gravitational pull on the equator would allow an egg to stand on it’s end during an equinox. Simply put, that is not true! It’s a demonstration I continue to see in both autumn and spring. I actually tried this many years ago on TV in Binghamton, NY. Since I could not duplicate it, I used double sided scotch tape to keep the egg upright during the broadcast. The truth: If you have the right egg, a flat spot to sit it on… just add patience and a steady hand will do the balancing any day of the year. I’m not the only one to debunk this. Check out this old video I found online showing a similar demonstration.
Polar seasons: Today, technically the sun will set on the north pole to begin 6 months of darkness. It will look more like twilight for about a month. On the flip side, the sun will rise on the south pole. Side note: Considering the heat and Arctic melt that was discussed at great length this summer, there has been record ice building and expansion in the Antarctic. Like last winter, we do expect a rapid recovery of rebuilding ice around the North Pole in the next few months, thanks to the darkness and building chill. Then the fun part begins, how it may relate to our winter and snowfall.
Video: National Geographic Describes Equinox Around The Globe
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Get the award winning Kid Weather App I made with my oldest son and support our love for science, weather, and technology. Our 3 year anniversary of the release and our contribution to STEM education is this November. It has been downloaded in 60 countries, and works in both temperature scales. With your support we can expand on the fun introduction to science and real weather.[/fusion_builder_column][/fusion_builder_row][/fusion_builder_container] | 0.866058 | 3.048736 |
Unlike their stationary counterpart, a pulsating aurora is continuously blinking, and sometimes it lights up the night sky like a party scene. And thanks to a Japanese satellite that measures plasma and electrons very precisely, scientists have discovered the mechanism underpinning this unique light show.
It is known that all auroras are caused by charged particles (typically electrons) crashing down into Earth’s atmosphere in high speed and bombarding air molecules in the upper atmosphere. However, between pulsating auroras and active auroras the source of these electrons is different.
Active auroras happen when a dense wave of solar wind—a blast of charged plasma, hits Earth’s magnetic field, causing it to rattle. This rattling releases electrons from the plasma, whose interaction with atmospheric atoms to create glowing lights that stretch across the sky in long ropes.
The electrons that cause pulsating auroras are believed to come in complex wave motions in the magnetosphere that can happen at any time, not just when a wave of solar material rattles the magnetic field. Rather than shimmer as a curtain of light, pulsating auroras glow and fade over tens of seconds. Although sometimes more intense than active auroras, most of pulsating auroras tend to be intermittent and faint.
With their Exploration of energization and Radiation in Geospace (ERG) satellite, planetary researchers from Japan measured waves in the plasma in the magnetosphere (the effective region of an astronomical object’ magnetic field), as well as the energy level of electrons.
The plasma and particles in a pulsating aurora event they tracked were also observed with an all-sky camera on Earth, at the location of The Pas, Manitoba. The Japanese researchers obtained the data from Canadian Space Agency and compared with their data from space.
According to their analysis, when chorus waves (just consider them as clumps of plasma waves) in the magnetosphere scatter their electrons intermittently, the energy level of the electrons is so high that when they can interact with particles, they emit a large number of photons, resulting in pulsating auroras.
Scientists suggested that the pulsating auroras could also happen on other planets of the solar system, such as Jupiter and Saturn, where chorus waves have been observed.
The findings were published in the journal Nature this February.
How We Solved the Mystery of Pulsating Auroras. Credit: SciShow Space | 0.802953 | 4.029981 |
At 13.40 on 15 December, a giant balloon carrying an equally gigantic payload lifted off from McMurdo station in Antarctica. Steve Barwick was glad to see it go. Maybe ’twas the season, but the device he had spent two years building had begun to remind him of a Christmas tree. However, the adornments on this 6-metre-tall hulk are radio antennas rather than baubles. And far from being decorative, this device is now turning the ice continent into the world’s biggest particle detector.
Barwick, of the University of California, Irvine, and colleagues developed ANITA – the Antarctic Impulsive Transient Antenna experiment – to detect ultra-high-energy neutrinos from sources outside our galaxy. If ANITA succeeds, it will become the first detector to spot such neutrinos. It could also help shed light on the origin of mysterious ultra-high-energy (UHE) cosmic rays, charged particles arriving on Earth at nearly the speed of light.
According to standard physics, cosmic rays created outside our galaxy with energies greater than about 1020 electronvolts (eV) should not reach Earth at those energies: as they travel over such vast regions of space they should lose energy because of collisions with photons of the cosmic microwave background (CMB), the radiation left over from the big bang.
This leads to a maximum possible energy for such cosmic rays reaching Earth, called the Greisen-Zatsepin-Kuzmin (GZK) cut-off. However, in 2004, Japan’s Akeno Giant Air Shower Array announced that since 1990 it had detected 11 cosmic rays with energies greater than this cut-off. In contrast, the HiRes cosmic ray detector in Utah did find signs of a cut-off (New Scientist, 14 October, p 14). “We’ve got a real mystery on our hands,” says physicist Peter Gorham, of the University of Hawaii, Honolulu, who heads the ANITA collaboration.
While cosmic-ray detectors such as the Pierre Auger observatory in Argentina are gearing up to look for UHE cosmic rays themselves, physicists have another ally in their quest to solve the puzzle. When cosmic rays hit the microwave photons in space, theory predicts that they should produce neutrinos with energies of about 1018 eV, as well as other particles. Because neutrinos rarely interact with matter, they should travel to Earth unimpeded.
It’s these so-called GZK neutrinos that Gorham and his colleagues are trying to detect with ANITA. “We need to find these neutrinos or we have real problems with our understanding of physics,” says Gorham, speaking from McMurdo Station in Antarctica. “These neutrinos are no longer optional.”
ANITA will exploit a phenomenon known as the Askaryan effect, whereby high-energy neutrinos streaming through ice, salt or sand produce a cone of radio waves when they collide with a nucleus in the material. These materials are transparent to radio waves, so the radio pulses should be detectable.
However, because neutrinos interact so rarely with matter, these collisions are few and far between. To have any chance of spotting them, you need to observe a vast mass of material. “We couldn’t find a huge quantity of pure sand or salt, but Antarctica has a huge mass of pure ice,” says Barwick. “That decided it.”
Before shipping their detector to Antarctica, the team had to prove that the theory works. So, six months ago, at the height of summer, Gorham, Barwick and colleagues found themselves jack-hammering away at a 10-tonne block of ice at the Stanford Linear Accelerator in Palo Alto, California. “It was the hottest day of the year and we were creating a mini-Antarctica from ice used by sculptors for weddings.” says Barwick. “I had to laugh.”
The team fired artificially generated neutrinos into their ice sculpture and successfully measured radio waves using the ANITA antennas (www.arxiv.org/hep-ex/0611008), which are designed to pick out radio waves from GZK neutrinos and nothing else. “It was vitally important to prove that the antennas work in this way,” says Gorham.
ANITA was shipped to Antarctica in September, after which the team had to just wait patiently for the right conditions for launch. Barwick, speaking from McMurdo earlier, said the atmosphere had been “electric”.
The balloon will take ANITA up to 38 kilometres over the Antarctic ice cap, where it will circle the South Pole, allowing its antennas to scan a million cubic kilometres of ice at a time (10 to 15 per cent of the whole continent), making this the largest neutrino detector by far. The next largest is IceCube, which will monitor a cubic kilometre of Antarctic ice using buried detectors to look for flashes of light generated by neutrinos hitting the ice.
Because radio waves can travel through ice for long distances without weakening, ANITA will be able to detect neutrino collisions occurring a mile down in the ice, even from 400 kilometres away.
The experiment is scheduled to fly for 40 days, but the time it spends up in the air is down to nature. The team will be monitoring the weather and the balloon carefully. If the balloon begins to veer towards the ocean or mountainous terrain, from where it can’t be recovered if it descends, the mission will have to be terminated, says Barwick. The team will detonate an explosive bolt in the wires holding ANITA, so that it can parachute down in an accessible region.
If the balloon veers towards terrain where it can’t be recovered, it will have to be released with explosive bolts
And even if all goes to plan, the equipment will probably land several thousand kilometres from its launch site, making it tough to recover, says Gorham. That’s what happened with the team’s prototype detector, ANITA-lite, sent up two years ago. Luckily it landed near an Australian station in Antarctica. “The Australians did us a favour and recovered it – they treated it as a training exercise for their pilots,” says Gorham.
With such probable delays in mind, the team have set up a satellite link with ANITA to receive important data even when the balloon is flying. “We’ll begin analysing the data immediately and should know within a few months whether we’re seeing neutrinos,” says Barwick.
Others are keenly awaiting the results. “This is virgin territory,” says astrophysicist Doug Cowen at Penn State University in Pittsburgh. Finding GZK neutrinos could allow astrophysicists to locate the sources of the high-energy cosmic rays. “The great thing about neutrinos is that they have no charge, so they don’t get deflected by magnetic fields,” says Cowen.
That means that, unlike cosmic rays, they will have followed a straight line to Earth. Hopefully when they are detected they will all have come from roughly the same direction, thus helping locate whatever shot out the neutrino-generating cosmic rays, he says. At the moment we don’t know what’s accelerating the cosmic rays – suggestions include supermassive black holes, quasars and gamma-ray bursts.
Hopefully the neutrinos will all come from roughly the same direction, helping locate whatever shot out the rays
If instead the neutrinos arrive randomly from all directions it could indicate that they have been hanging around since just after the big bang. “Neutrinos are the only particles that can give us this information,” says Cowen. “They are our cosmic messengers.”
And if ANITA doesn’t find any neutrinos? Gorham is confident it will. “We could pick up one an hour, or one per month – we don’t know yet,” he says. “But we should see something because all of physics is crying out for neutrinos to be there.”
Astrophysicist Igor Liubarksy at Imperial College London isn’t so sure. “They might see nothing, in which case we will have to rewrite our understanding of fundamental physics,” he says. “If that happens – well that would be the most exciting result of all.” | 0.822171 | 3.902355 |
Why a 'Faint Rumble' on Mars Is 'So Exciting'Newser — Arden Dier
It was a "faint rumble" but it meant something big—the first seismic signal detected on the surface of a planetary body other than our home planet and moon.
We have NASA's Martian InSight lander to thank. The lander has been listening for quakes that could shed light on Mars' guts since its robotic arm deposited a shielded seismometer on the western side of Elysium Planitia last December, a few weeks after the lander touched down.
The key moment—hear it here—came April 6, 128 days into the mission. "This particular Marsquake—the first one we've seen—is a very, very small one," says the mission's chief scientist, Bruce Banerdt.
"You wouldn't even notice this one in your day-to-life." Adds researcher Tom Pike, per the BBC: "There are a lot of uncertainties" but "it's probably only a Magnitude 1 to 2 event, perhaps within [62 miles] or so."
The tremor—which lasted 10 minutes, per National Geographic—could indicate movement inside the planet or a meteorite impact.
"Interestingly, InSight's scientists say the character of the rumble reminds them very much of the type of data the Apollo sensors gathered on the lunar surface," per the BBC.
The team is also investigating lesser signals detected March 14, April 10, and April 11 but can't yet confirm they were seismic events. "When you've got one, you don't know whether you were just lucky, but when we see two or three we will have a better idea" about the activity within the planet, Pike tells the BBC.
Yet one confirmed "Marsquake" seems enough for InSight's seismometer boss Philippe Lognonné. "It's so exciting to finally have proof that Mars is still seismically active," he says, per Space.com.
"We've been waiting [for] months."
- The Kilogram Will Never Be What It Was
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- Mass Grave Tells of Horror When the Men Were Away
This article originally appeared on Newser: Why a 'Faint Rumble' on Mars Is 'So Exciting' | 0.820659 | 3.15799 |
By 2030 our understanding of the way cosmological structures formed will have been dramatically improved. And LISA will fill the gap.
Improvements will have been made by high-redshift observations of quasi-stellar objects (QSOs) and protogalaxies from missions like the JWST, EUCLID and the Wide-Field Infrared Survey Telescope (WFIRST), and by the Atacama Large Millimeter/submillimeter Array (ALMA) on the ground.
These observations may well have constrained the supermassive black hole mass spectrum from a few times 1010 solar masses, or even higher, down to around 107 solar masses, but probably not into the main LISA range of 104 – 106 solar masses.
LISA observations will fill this gap and also provide a check on selection effects and other systematics of the electromagnetic observations. By measuring the mass and spins of massive black holes as a function of redshift out to z = 20 or so, LISA will greatly improve models of how ultra-massive black holes grow so quickly, and what roles accretion and mergers play in the growth of all massive black holes. LISA observations of mergers of 104 – 105 solar mass Black holes out to z = 20 can provide a strict test of the amount of growth by merger expected in these models. | 0.855951 | 3.530584 |
Credits: NASA’s Goddard Space Flight Center/Scientific Visualization Studio
This time-lapse video, obtained June 8, 2018, shows the precise choreography of NASA’s Neutron star Interior Composition Explorer (NICER) as it studies pulsars and other X-ray sources from its perch aboard the International Space Station. NICER observes and tracks numerous sources each day, ranging from the star closest to the Sun, Proxima Centauri, to X-ray sources in other galaxies. Movement in the movie, which represents a little more than one 90-minute orbit, is sped up by 100 times.
One factor in NICER’s gyrations is the motion of the space station’s solar arrays, each of which extends 112 feet (34 meters). Long before the panels can encroach on NICER’s field of view, the instrument pirouettes to aim its 56 X-ray telescopes at a new celestial target.
As the movie opens, the station’s solar arrays are parked to prepare for the arrival and docking of the Soyuz MS-09 flight, which launched on June 6 carrying three members of the Expedition 56 crew. Then the panels reorient themselves and begin their normal tracking of the Sun.
Neutron stars, also called pulsars, are the crushed cores left behind when massive stars explode. They hold more mass than the Sun in a ball no bigger than a city. NICER aims to discover more about pulsars by obtaining precise measures of their size, which will determine their internal make-up. An embedded technology demonstration, called Station Explorer for X-ray Timing and Navigation Technology (SEXTANT), is paving the way for using pulsars as beacons for a future GPS-like system to aid spacecraft navigation in the solar system — and beyond.
Read Full Article | 0.852579 | 3.306093 |
Approximately 2.4 billion years ago, the Great Oxidation Event, which dramatically increased the oxygen content in Earth’s atmosphere, paved the way for the rise of all lifeforms that use oxygen to break down nutrients for energy. While scientists agree about when the event happened, they are less certain about exactly how it occurred.
Now, however, researchers at Missouri S&T say they’ve discovered a possible trigger for the Great Oxidation Event and the arrival of plants and animals on Earth.
An assistant professor of geosciences and geological and petroleum engineering at Missouri S&T, Dr. Marek Locmelis’ geological research investigates the processes that occur in Earth’s interior. Part of his research examines if and how oxygen bound in minerals and magmas in the interiors of planets can affect the composition of oceans and atmospheres and contribute to whether a planet is habitable.
“Without the Great Oxidation Event, there would be no plant and animal life on Earth or at least no life on Earth as we know it – including us,” says Locmelis. “We provided really solid evidence that Archean mantle oxidation contributed to it, which was something that was ruled out for the past 20 or 30 years.”
In a paper for the August issue of American Mineralogist, Locmelis describes how he used a technique known as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis to study minerals that contain clues on how Earth’s interior changed over time. This technique enables much more sensitive isotopic and elemental analysis of solid samples than earlier methods.
Locmelis studied samples of the mineral olivine in igneous rocks called komatiites. These rocks were derived from Earth’s mantle during the Archean Eon – a geologic time period of Earth’s history from 4 billion to 2.5 billion years ago. In collaboration with researchers at the University of Maryland, The University of Western Australia and Royal Holloway, University of London, Locmelis gathered samples of komatiites from the Kaapvaal and Zimbabwe Cratons in southern Africa, the Yilgarn Craton in Australia, and the Superior Craton in Canada. A craton is an old, stable part of the Earth’s topmost layers – the crust and upper mantle. The samples range from 2.7 billion to 3.5 billion years old.
“Because they’re so old, and they came from deep in the Earth, they allow us a unique window into what the interior of our planet looked like more than 2.7 billion years ago,” says Locmelis.
The researchers compared the trace element chemistry of olivine from komatiites that are 3.5 billion to 3.3 billion years old to ones that formed more recently – about 2.7 billion years ago. Locmelis focused on redox-sensitive element rations, such as vanadium to scandium, which can be used to investigate redox conditions of magmas. Redox — or reduction-oxidation reaction – is a type of chemical reaction in which the oxidation states of atoms are changed. Reduction and oxidation reactions play an important part in the evolution of planetary atmospheres. Increased levels of oxygen – an oxidizing atmosphere – may have enabled the evolution of aerobic respiration, allowing today’s plant and animal life to evolve and thrive.
Locmelis’ research team found that, based on trace element ratios captured by olivine, it appears that Earth’s mantle gradually became more oxidized between 3.5 billion and 2.7 billion years ago. This oxidation, in turn, possibly triggered the Great Oxidation Event, which scientists agree occurred some 2.4 billion years ago.
Locmelis says previous studies from the 1990s and early 2000s largely dismissed the Archean Eon mantle oxidation because they used different analytical techniques. Researchers used to crush and analyze whole rocks instead of being able to isolate minerals, such as olivine, and analyze them via modern techniques, such as the one used in this study.
“Take eating a sandwich. You take a bite and just want to taste a pickle, but sometimes the pickle is so small that you’re overwhelmed by all the other flavors,” says Locmelis. “That’s the difference between whole rock studies and mineral studies. When you analyze minerals directly, you circumvent all the problems associated with bulk analysis, which really are just a mix of different flavors or geological processes. If you analyze minerals that crystallized early from the magma, you really have much more robust information, especially with all the modern techniques we have available today.”
Locmelis says his study suggests that Archean mantle oxidation may have contributed to, or even triggered, the oxidation of the atmosphere, which led to the lifeforms on Earth today. He notes that a recent study by Dr. Robert Nicklas from the University of Maryland, submitted at the same time as his, yielded similar results, but used a different analytical approach.
“If two studies come to the same conclusion, independently and with different techniques, it suggests that we are really onto something, and that we have to rethink our understanding of the redox evolution of our planet,” says Locmelis.
Understanding how Earth evolved also provides insight into the evolution of other planets and exoplanets and their atmospheres, according to Locmelis. He says that probably not all planets in our galaxy have undergone mantle oxidation and therefore have atmospheres that are more reduced and toxic. Understanding the geological past of extraterrestrial bodies can help scientists understand how life forms on other planets in our solar system and beyond, he says. Locmelis says S&T researchers are now investigating meteorites from other bodies in the solar system that represent different stages of planetary evolution to gain further insight into the evolution of these systems. | 0.865621 | 3.307797 |
eso1414 — Science Release
Length of Exoplanet Day Measured for First Time
VLT measures the spin of Beta Pictoris b
30 April 2014
Observations from ESO’s Very Large Telescope (VLT) have, for the first time, determined the rotation rate of an exoplanet. Beta Pictoris b has been found to have a day that lasts only eight hours. This is much quicker than any planet in the Solar System — its equator is moving at almost 100 000 kilometres per hour. This new result extends the relation between mass and rotation seen in the Solar System to exoplanets. Similar techniques will allow astronomers to map exoplanets in detail in the future with the European Extremely Large Telescope (E-ELT).
Exoplanet Beta Pictoris b orbits the naked-eye star Beta Pictoris , , which lies about 63 light-years from Earth in the southern constellation of Pictor (The Painter’s Easel). This planet was discovered nearly six years ago and was one of the first exoplanets to be directly imaged. It orbits its host star at a distance of only eight times the Earth-Sun distance (eso1024) — making it the closest exoplanet to its star ever to be directly imaged .
Using the CRIRES instrument on the VLT, a team of Dutch astronomers from Leiden University and the Netherlands Institute for Space Research (SRON) have now found that the equatorial rotation velocity of exoplanet Beta Pictoris b is almost 100 000 kilometres per hour. By comparison, Jupiter’s equator has a velocity of about 47 000 km per hour , while the Earth’s travels at only 1700 km per hour . Beta Pictoris b is more than 16 times larger and 3000 times more massive than the Earth, yet a day on the planet only lasts 8 hours.
“It is not known why some planets spin fast and others more slowly,” says co-author Remco de Kok, “but this first measurement of an exoplanet’s rotation shows that the trend seen in the Solar System, where the more massive planets spin faster, also holds true for exoplanets. This must be some universal consequence of the way planets form.”
Beta Pictoris b is a very young planet, only about 20 million years old (compared to 4.5 billion years for the Earth) . Over time, the exoplanet is expected to cool and shrink, which will make it spin even faster . On the other hand, other processes might be at play that change the spin of the planet. For instance, the spin of the Earth is slowing down over time due to the tidal interactions with our Moon.
The astronomers made use of a precise technique called high-dispersion spectroscopy to split light into its constituent colours — different wavelengths in the spectrum. The principle of the Doppler effect (or Doppler shift) allowed them to use the change in wavelength to detect that different parts of the planet were moving at different speeds and in opposite directions relative to the observer. By very carefully removing the effects of the much brighter parent star they were able to extract the rotation signal from the planet.
“We have measured the wavelengths of radiation emitted by the planet to a precision of one part in a hundred thousand, which makes the measurements sensitive to the Doppler effects that can reveal the velocity of emitting objects,” says lead author Ignas Snellen. “Using this technique we find that different parts of the planet’s surface are moving towards or away from us at different speeds, which can only mean that the planet is rotating around its axis“.
This technique is closely related to Doppler imaging, which has been used for several decades to map the surfaces of stars, and recently that of a brown dwarf — Luhman 16B (eso1404). The fast spin of Beta Pictoris b means that in the future it will be possible to make a global map of the planet, showing possible cloud patterns and large storms.
“This technique can be used on a much larger sample of exoplanets with the superb resolution and sensitivity of the E-ELT and an imaging high-dispersion spectrograph. With the planned Mid-infrared E-ELT Imager and Spectrograph (METIS) we will be able to make global maps of exoplanets and characterise much smaller planets than Beta Pictoris b with this technique”, says METIS principal investigator and co-author of the new paper, Bernhard Brandl.
Beta Pictoris has many other names, e.g. HD 39060, SAO 234134 and HIP 27321.
Beta Pictoris is one of the best-known examples of a star surrounded by a dusty debris disc. This disc is now known to extend out to about 1000 times the distance between the Earth and the Sun. Earlier observations of Beta Pictoris’s planet were reported in eso0842, eso1024 and eso1408.
The observations made use of the adaptive optics technique compensating for the Earth’s atmospheric turbulence which can distort images obtained at even the best sites in the world for astronomy. It allows astronomers to create super-sharp images, almost as good as those that could be seen from space.
Brown dwarfs are often dubbed “failed stars” as, unlike stars such as the Sun, they are not massive enough to sustain nuclear fusion reactions.
This research was presented in a paper “Fast spin of a young extrasolar planet”, by I. Snellen et al., to appear in the to appear in the journal Nature on 1 May 2014.
The team is composed of Ignas A. G. Snellen (Leiden Observatory, Leiden University, Leiden, the Netherlands), Bernhard Brandl (Leiden Observatory), Remco J. de Kok (Leiden Observatory, SRON Netherlands Institute for Space Research, Utrecht, the Netherlands), Matteo Brogi (Leiden Observatory), Jayne Birkby (Leiden Observatory) and Henriette Schwarz (Leiden Observatory).
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 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. 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 the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
- Research paper
- Photos of the VLT
- Photos of CRIRES
- The CRIRES instrument on the VLT
- More about METIS: A Mid-Infrared E-ELT Imager and Spectrograph
- Video describing the Beta Pictoris b result (from Leiden University/NOVA, the Netherlands)
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The Scientific Evidence Against the Big Bang
A Summary from LPPFusion, Inc.
The contradictions between Big Bang theory predictions and observations are not at all limited to those that have been widely dubbed a “Crisis in Cosmology”. Despite the continuing popularity of the theory, essentially every prediction of the Big Bang theory has been increasingly contradicted by better and better data, as shown by many teams of researchers. The observations are, on the other hand, consistent with a non-expanding universe with no Big Bang. The real crisis in cosmology is that the Big Bang never happened.
Key contradicted predictions (detailed descriptions below):
1) Light elements: Lithium and Helium
Prediction: Any superhot explosion throughout the universe, like the Big Bang, would have generated a certain small amount of the light element lithium and a large amount of helium.
Observation: Yet as astronomers have observed older and older stars, the amount of lithium observed has gotten less and less, and, in the oldest stars is less than one tenth of the predicted level. The oldest stars near to us have less than half the amount of helium predicted. However, well-understood fusion processes in stars and reactions initiated by cosmic rays have accurately predicted the correct amounts of these and other light elements.
2) Antimatter-matter annihilation
Prediction: Since the intense radiation of the Big Bang would produce matter and antimatter in equal amounts, mutual annulation of particle-antiparticle pairs would reduce the surviving matter density to around 10 -17 protons/cm3.
Observation: the matter density in the universe is observed to be at least 10 -7 ions /cm3 more than 10 billion times higher than the Big Bang prediction.
Big Bang fix to prediction: To try to fix this well-known vast gap, Big Bang theorists have proposed some unknown asymmetry between matter and antimatter which would lead to more production of matter. This has never been observed in laboratory experiments. A consequence of this predicted imbalance is the decays of the proton, initially predicted to decay with a lifetime of 1030 years. Large scale experiments have contradicted this prediction was well, with no evidence of decay at all.
Prediction: In any expanding universe, an optical illusion makes objects at high redshift appear larger and dimmer, so their surface brightness—the ratio of apparent brightness to apparent area—declines sharply with redshift.
Observation: Based on observations of thousands of galaxies, surface brightness is completely constant with distance, as expected in a universe that is NOT expanding.
Big Bang fix to Prediction: After observations showed that the surface brightness dimming did not occur, Big Bang theorists hypothesized that galaxies were much smaller in the distant past and have grown greatly. But observations have contradicted this fix as well, showing that there have not been enough galaxy mergers for the growth rates needed. In addition, the ultra-small galaxies hypothesized would have to have more mass in stars than total mass, an obvious impossibility.
4) Too Large Structures
Prediction: In the Big Bang theory, the universe is supposed to start off completely smooth and homogenous. Structure starts small and grows over time
Observation: As telescopes have peered farther into space, huger and huger structures of galaxies have been discovered, which are too large to have been formed in the time since the Big Bang.
5) Cosmic Microwave Background Radiation (CMB) and its Anisotropies
Prediction(Initial): The CMB is a smooth relic of the initial radiation of the Big Bang
Observation: The CMB is smooth on such large scales that , in a Big Bang there would be too little time for regions that we now see in different parts of the sky to reach equilibrium with each other, or even to receive energy from each other at the speed of light.
Big Bang fix to prediction: An unknown force, dubbed ”inflation” generated an exponential phase of the Big Bang that blew up the universe so rapidly that all asymmetries were smoothed away.
Additional observations: The actual very small anisotropies in the CMB were much smaller than those predicted by Big Bang theorists and additional fixes had to be added to the theory each time the observations became more precise, so that at present seven free variables—the density of dark matter, of ordinary matter, of dark energy and four additional fitting parameters—are needed to fit the observations. They still badly fail with some of the largest-scale anisotropies
The latest crisis: Based on the data from the Planck satellite, the best fit to the CMB predicts a Hubble constant (the ratio of redshift to distance) in conflict with observations based on Supernovae. The best fits imply a curved universe, in conflict with the predictions of inflation for a flat universe. And they predict a density of dark matter far greater than any measurements derived from the motion of galaxies.
In contrast to the multiple contradictions of the Big Bang theory of the CMB with its “ultra precise” but wrong predictions, non-Big Bang processes provide a better explanation. The energy that was released in producing the observed helium in the universe equal the energy in the CMB. Any radiation become isotropized if it travels in a medium that scatters it. There is abundant observational evidence that microwave-frequency radiation is scattered in the intergalactic medium.
6) Dark Matter
Prediction: The Big Bang theory requires the existence of dark matter—mysterious particles that have never been observed in the laboratory, despite huge experiments to find them.
Observation: Multiple lines of evidence, especially observations of the motions of galaxies, show that this dark matter does not exist. Extremely sensitive experiments on earth have failed to detect dark matter particles. In addition, dark matter, if it existed would create a viscosity effect on galaxies that would prevent the existence of the many long-lived groups of galaxies that are observed.
The response of most cosmologists to this growing body of evidence has, unfortunately, not been to decide the Big Bang theory has been falsified, but to add new “parameters” and hypotheses, like dark energy. The theory is now far more complex and speculative than the Ptolemaic epicycles that were destroyed by the Scientific Revolution. Each contradiction with observation is taken as a mere “anomaly” that does not undermine the theory as a whole. Strong peer pressure is applied against many of those who question the theory.
“It’s as if researchers are saying ‘I can see the Emperor’s elbow through his New Clothes,’ ‘I can see the Emperor’s knee though his New Clothes’ and so on,” says Lerner. “It is time to say: ‘The Emperor is not wearing any clothes.’ This theory has no correct predictions.”
To replace the Big Bang, other researchers have elaborated, in peer-reviewed publications, alternative explanations of the generation of light elements and of the energy in the CBR by ordinary stars, and of the development of large-scale structures through the interaction of gravity and electromagnetic processes. “No one would claim that all the problems in cosmology have been resolved,” agrees Lerner, “but the evidence is consistent with an evolving, but non-expanding universe, which had no beginning in time and no Big Bang.”
More detailed descriptions of the evidence against the Big Bang theory
- Light elements: Lithium and Helium
The Big Bang theory unequivocally predicts certain amounts of light element, including lithium, helium and deuterium, must be produced in the explosion that is hypothesized to have started the universe. For lithium, the prediction is 400 lithium atoms for every trillion hydrogen atoms.
However, astronomers have measured the abundances of lithium in old stars in our galaxy and they have not found the Big Bang predictions to be correct. They know the stars were formed very early in the history of our galaxy, because they have very tiny amounts of iron and other heavy elements that are produced by previously-existing stars. In most of these stars, the lithium abundance is only 160 lithium atoms per trillion atoms, far below the Big Bang predictions.
In addition, as more data became available over the last few years (as described by many researchers, including, for example, Sbordone, Bonifacio and Caffau) it became clear that the older the stars, the less the lithium.
A new study by Lerner, presented at the January, 2020 meeting of the American Astronomical Society, showed that for both lithium and helium observations of abundances in old stars now differ from predictions by more than a dozen standard deviations and the gap has been widening at an accelerating pace. The oldest stars have less than half the helium and less than one tenth the lithium than that predicted by Big Bang Nucleosynthesis theory. The lowest lithium levels observed are less than 1% that predicted by the theory. Indeed, the evidence is consistent with no helium or lithium having been formed before the first stars in our galaxy.
Equally important, the study shows that the right amounts of these light elements have been predicted by an alternative explanation, which hypothesizes that these elements were produced by stars in the earliest stages of the evolution of galaxies. This alternative explanation, which Lerner calls the Galactic Origin of Light Elements or GOLE hypothesis, derives from theoretical expectations that the first generation of stars to form in a galaxy are intermediate-mass stars that are from 4 to 12 times as massive as the sun. These stars burn hydrogen to helium in tens to a couple of hundred million years, much faster than our sun’s burn rate of ten billion years. The helium then disperses in powerful stellar winds during the late stages of these stars’ lifetimes. Cosmic rays from these early stars, colliding at high energy with other nuclei, produce deuterium and lithium.
Li vs Fe abundance for the 26 known dwarf stars with Fe/H<10 ppb. These are the oldest stars, with the least contamination from earlier stars. Dark blue dots are measured values, red dots are Li upper limits and light blue dots are Li and Fe upper limits. The BBN predicted range of values is shown by the red solid lines. rk upper limits on lithium abundance of individual stars.
While these data flatly contradict the predictions of the Big Bang, they were predicted and simply explained by theories of galactic evolution that assumed there was no Big Bang, including a paper published in 1989 by Lerner. Lithium, as is well known, is produced by cosmic rays, emitted by early stars, crashing into carbon and oxygen nuclei, as well as by stars in their giant phase. The same stellar processes, Lerner showed, could produce the observed abundance of helium—from thermonuclear reactions in early intermediate-mass stars—and deuterium (again from cosmic rays), while producing the observed amounts of heavier elements like carbon and oxygen.
The new study includes new calculations based on this GOLE hypothesis that show that not only do early stars produce the observed amounts of helium, deuterium and lithium, but that they also produce other elements such as carbon, boron and beryllium in the amounts observed in the oldest stars. “The GOLE hypothesis was first published in a full form in my own paper in 1989 and had been discussed by others even earlier” explains Lerner. “Those published predictions have been confirmed by decades of subsequent observations, unlike the predictions of the Big Bang hypothesis. The new work that I am reporting at this conference makes the predictions more precise and is based on the much more extensive knowledge we now have of stellar evolution.”
These conclusions, based on observations of old stars in our galaxy, are strengthened by recent observations of the conditions in newly-formed galaxies. These galaxies are ultra-luminous, converting hydrogen to helium at hundreds of times the rate of our galaxy at present. Work by other researchers published in the last year show that their luminosity is driven by stars of about 8 solar masses and above, as had been predicted by the GOLE hypothesis.
2. Surface Brightness
The hypothesis that the universe is expanding is a basic pillar of the Big Bang theory. But observations of the size and brightness of thousands of galaxies contradict predictions based on the Big Bang expansion hypothesis, thus shaking this key pillar as detailed in a paper in MNRAS by LPPFusion Chief Scientist Eric Lerner, titled “Observations contradict galaxy size and surface brightness predictions that are based on the expanding universe hypothesis”, which finds that none of the published expanding-universe predictions of galaxy-size growth fit the actual data. All of the proposed physical mechanisms for galaxy growth, such as galaxy mergers, also contradict observations. However, the paper finds that the data are closely fit by the contrary hypothesis that the universe is not expanding, and that the redshift of light is caused by some other, currently unknown, process.
This research tests a striking 1930s prediction of Big Bang hypothesis that objects at great distances should actually appear larger, not smaller. According to the hypothesis, this is because of an optical illusion due to the galaxies having been much closer when their light was emitted.
This prediction was repeated in the literature through the 1980s but in the 1990s, the Hubble Space Telescope did not confirm the prediction. Hubble’s images instead showed that the most distant galaxies do in fact look the smallest. A group of researchers then formulated an additional hypothesis that galaxies actually grow in size with time. So very distant galaxies, viewed as they were billions of years ago, were theorized to have been much smaller than present-day ones. In this way, the smaller intrinsic galaxy sizes of the 1990s galaxy-growth theory neatly cancelled out the 1930s optical illusion prediction.
In Lerner’s paper the quantitative, published, predictions of the galaxy-growth theories were tested against the observed sizes of thousands of both spiral and elliptical galaxies, using HST observations from the period 2004-2014. The paper limited the samples to galaxies that have close to the same UV brightness. (Brighter galaxies are larger.) The observed data did not come close to fitting the predictions that galaxy size grows in proportion to the rate of expansion of the universe (Figure 1).
Figure 1. Log of the median radius of galaxies (in kiloparsec where 1 kiloparsec is 3,260 light-years), calculated with the expanding universe formula, are plotted here against the log(H(z)), a measure of hypothesized cosmological expansion, a function of the red shift z. Red squares are samples of spiral galaxies, black circles are samples of elliptical galaxies. The black straight line is the closest prediction of galaxy size based on cosmological expansion and the hypothesized galaxy growth. It does not fit the data.
In addition, Lerner pointed out that the process hypothesized for the growth of elliptical galaxies—mergers with other galaxies—occurs at a rate nearly ten times too slow for the growth hypothesized. A still worse contradiction with observation is obtained by comparing the gravitating mass of distant galaxies, (calculated from rotational speed and size), with the mass of the stars in them, (calculated from their emitted light). The size predictions based on the expanding universe lead to a gravitating mass smaller than the mass of the stars, an obvious impossibility.
While the expanding universe predictions did not fit the data, Lerner found that predictions based on a non-expanding universe fit both the spiral and elliptical galaxies at all distances to an accuracy of a few percent. No matter what the distance, with a non-expanding universe, the galaxies of a given brightness were the same size, just as predicted by the non-expanding hypothesis. (Figure 2).
Figure 2. The log radius of galaxies assuming a non-expanding universe is plotted against the log of z, where z is the redshift. Black circles are samples of elliptical galaxies and blue and red symbols are samples of spiral galaxies. As predicted by the non-expanding hypothesis, the size remains constant for galaxies of the same brightness (luminosity).
“In this hypothesis, the simple linear relation between the redshift of light and distance is caused by something that happens to the light as it travels, not by the expansion of space,” Lerner explains. “Right now, no one knows what could cause this, but the linear relationship and a non-expanding space make predictions that fit the data, while the expanding universe predictions don’t fit. ”
The present research is an extension of earlier work done by Lerner at LPPFusion with colleagues Dr. Renato Falomo (INAF – Osservatorio Astronomico di Padova), and Dr. Riccardo Scarpa (Instituto de Astrofısica de Canarias, Spain) and published in 2014.
More background on this research can be found here.
3. Structures Too Large to Form in the Time Since the Hypothesized Big Bang
The Big Bang theory hypothesizes that the universe came into existence with an almost perfectly homogenous—even—distribution of matter, and that structures built up gradually from stars to galaxies to cluster to superclusters.
But larger and larger structures have been uncovered at earlier and earlier times. To cite one recent example of many, in 2013 a team of observers, Roger Clowes, et al, discovered a huge collection of quasars over 3 billion light years in extent, existing billions of years ago. This was, in their view, too large to have been created within the hypotheses of conventional cosmology. Even larger structures of galaxies where found in 2016 by Shirokov et al.
Figure 3. The huge agglomerations of quasars discovered by Roger Clowes et al. Tick marks are separated by 600 million light years. These objects are far too large to have been generated in the time since the Big Bang.
Figure 4. In 2016 Shirokov et al found similarly-sized conglomerations of galaxies. Here density of galaxies is plotted against redshift.
Indeed, Lerner has pointed out that, when the existing low velocities of galaxies are taken into account, the large structures of conglomerations of galaxies that we observe would take hundreds of billions of year to form. In pioneering work in 1986 Lerner used plasma physics to predict a fractal structure of the universe, including structures up to billions of light years across, structures that were later discovered. In Lerner’s theory, these structures could only have formed in a universe whose history stretches far back before 14 billion years ago.
4. The Cosmic Microwave Background Radiation and the Problem of Large-Scale, Non-Random, Asymmetries
The Cosmic Microwave Background Radiation (CMB) is frequently cited as the key evidence for the Big Bang, and for inflation, the super-expansion during the Big Bang that is a critical element of the theory. One of the few concrete predictions of inflation is that the universe is isotropic, the same in all directions.
The inflation theory predicts that any asymmetries in the universe existing before inflation would be wiped out by the vast expansion during inflation. “The most decisive observational evidence against inflation would be provided by evidence that the Universe possesses large-scale rotation,” wrote Barrow and Liddle in a 1997 paper.
But in fact the CMB evidence, combined with evidence from observations of galaxies, flatly contradicts the prediction of perfect isotropy.
The results from the Planck satellite confirmed what had been known for years, that there are non-random alignments on the sky of the small fluctuations in the intensity of the CMB. (These are only the most prominent contradictions of inflation predictions by Planck data).
In addition, a study of the handedness of spiral galaxies in 2012 showed a non-random alignment of the galaxy spins on a very large scale. Such spin alignments indicate precisely the large scale rotation that contradicts inflation. In 2019 Lee et al found coherent rotation in filaments of galaxies. The dynamical time to form such large, slowly rotating objects is on the order of a trillion years—they could not possibly have formed in the 14 billion years since the hypothesized Big Bang.
Researchers have for years attempted to find evidence of the Big Bang theory in the spectrum of anisotropies in the CMB—the plot of the power of the fluctuations versus their size on the sky. In order to fit the six bumps and seven dips in this curve, theorists have required seven free variables—the density of dark matter, of ordinary matter, of dark energy and four additional fitting parameters. Even so, the theory remains a poor fit to the spectrum at the largest scales—those of a few degrees or more, as can be seen in Figure 5, where the dips at 2 and 20 are entirely missed by the best theoretical fit.
Figure 5. The amplitude of the anisotropies in the CMB are plotted against mode number. The larger the mode number, the smaller the anugualr size of the anisotropies. Note the big deviation form the fitted, red, curve at 2 and 20.
In the past two years, much attention was given to the fact that the value of the Hubble constant predicted by the fit to the CMB spectrum was different from the value actually measured by comparing the distance to supernovae with their redshifts. While this was described as. Difference between two measurements, it was in fact a failure of a theoretical prediction, based on fitting the CMB spectrum with the help of Big Bang theory. The only direct measurement was based on the supernovae data, which compare two observable quantities, the apparent brightness of the supernovae and the redshift of their spectrums.
The latest crisis paper by Eleonora Di Valentino, Alessandro Melchiorri and Joseph Silk details additional serious contradictions between predictions and observations, as well as inconsistencies in the predictions themselves. These authors point out that the parameters that fit the smaller scale part of the spectrum are different than those that fit the entire spectrum. In addition, if all seven parameters are used, the best fit is a combination of dark matter and dark energy that describes a curve, closed universe, not the Euclidean flat universe that is a prediction of inflation. On top of that, the amount of dark matter predicted by the best fit is so large that it would cause galaxies to move past each other much faster than observed. As well the new fits worsens the prediction of the Hubble constant.
In summary, despite the multiplication of fitting factors and the addition of dark energy and dark matter, the Big Bang predictions concerning the CMB fail in every direction.
There are alternative explanations of the CMB that do not require a Big Bang. It has been known for decades that the energy needed to account for the microwave background is equal to the energy that would have been released by the production by ordinary stars of the known amount of helium. In addition, the isotropy and black-body spectrum of the CMB are inevitable if the intergalactic medium is not perfectly transparent to microwave radiation. Indeed evidence has been accumulating for 30 years that this is the case. The CMB is a radio fog permeating the present-day universe, not some ghost of a long-ago Big Bang.
If the universe scatters or absorbs microwave and radio radiation, but is transparent in the shorter-wavelength infrared bands, then more distant objects will appear dimmer in radio bands then in IR. Lerner first published observational evidence of this absorption effect in 1990 and 1993, showing that radio emission by galaxies dropped by a factor of 10 as distance increased to 200 Mpc. This distance corresponds to a look-back time of only 600 MY, too short a time for any evolutionary process to create such a dramatic change.
Figure 6. This graph, from Lerner’s 1993 paper shows the logarithm of radio luminosity of galxies plotted aginst the log of the distance. The corrleation can only be explained by a strong asborption in the IGM.
In the past decade, much deeper surveys have shown that this same trend of radio dimming with distance continues to higher z. While by itself this dimming over much large distance and thus much greater look-back times could be interpreted as some sort of evolution, the fact that it is continuous with the much shorter-range effect analyzed 30 years ago rules out a purely evolutionary explanation. Lerner found that for nearby galaxies with redshift z<0.07 radio emission falls as z-0.32, while Delhaize et al in 2017 found that for z< 1.5 radio emission falls as z-0.27, and a continuous slope now extends out to z=3. An evolutionary process accounting for this change in brightness with distance would have to accelerate ridiculously as it approached the present, with galaxies doubling in brightness in the last 10 million years alone.
Not only does the observation of radio-frequency absorption allow the production of an isotropic black-body CMB in the present-day universe, it rules out the hypothesis that the CMB was created by a Big Bang. Absorption of such radiation would dim its spectrum to a grey-body, not a black-body shape, something clearly contradicted by observation.
There are at least two phenomenon that could account for the absorption of microwave and RF radiation. Lerner had derived from plasma theory a prediction that radiation in these wavelengths would be absorbed and reemitted by electrons trapped in dense plasma filaments emitted from a range of astrophysical jets extending from stellar Herbig-Haro objects to quasars. In addition, other researchers have pointed out that spinning dust particles can also absorb and re-emit microwaves.
5. Evidence Against Dark Matter
The Big Bang theory, in its current form, predicts that most matter in the universe is dark matter, unlike any that has been found on earth.
Increasingly sensitive experiments on earth have failed to turn up any evidence of the dark matter particles that are firmly predicted by the Big Bang theory. But in addition, astronomical evidence as well has ruled out dark matter. The simplest evidence is in the relatively low velocities of galaxies in the universe. (These can be measured for galaxies for which there are independent, non-redshift-based measurements of their distance. The redshifts can then be used to measure velocities of galaxies relative to one another.) The large amounts of dark matter predicted by the Big Bang would generate gravitational forces that will whip the galaxies around at hundreds of km per second. But the observed average velocities of 50 km/sec rules out the large amounts of dark matter required by the Big Bang, as Baryshev, Sylos-Labini, Montuori, Pietronero and Teerikourpi have pointed out. Nor would a super-smooth distribution of dark matter needed to avoid high velocities be compatible with the lumpiness—inhomogeneity—of matter that is observed on all scales.
In addition, the satellite galaxies of both the Milky Way and the nearby Andromeda galaxy are in a disk configuration, just as expected if the gravitating mass is ordinary matter. If the gravitating mass were dark matter, the satellites would have to be in a random sphere. This evidence completely contradicts the dark matter hypothesis, as Pavel Kroupa, among many other researchers, has pointed out.
Perhaps most decisively, Oehm and Kroupa in 2018 showed that the viscosity effect that is inevitable with dark matter would cause groups of galaxies to merge so rapidly that very few would be observed, in contrast with the many such groups that actually exist.
Again, there are other, simpler, non-Big Bang ways of explaining the data. Over 30 years ago, Peratt and Green showed that electromagnetic forces would produce the constant velocity of rotation in spiral galaxies that has long been used as a key evidence of dark matter. These velocities are measurements of the velocity of radio-emitting plasma within a galaxy, which is as much influenced by magnetic forces as by gravitational forces.
Jolacha, Bratek and others have shown that in the outer regions of galaxies, including the Milky Way, gas moves faster than stars and that this difference can be explained by the influence of magnetic fields on the gas. More recently Kounkel and Covey provided strong evidence of the influence of magnetic fields on the motion of stars as well. They found that a large fraction of nearby stars are embedded in filaments that have endured for hundreds of MY of even GY. While the authors don’t draw this conclusion in their paper, it is clear that gravitational forces alone can’t create long-lasting filamentary structures. However, magnetic fields with observed
strengths can dominate the dynamics of filaments of dense gas and these filaments can in turn gravitationally control the motion of the stars within them. Magnetic fields, rather than hypothetical dark matter, can provide the additional confining forces observed in galaxies.
Each of these sets of problems could be, and in fact often are, dismissed as mere “anomalies” in an otherwise well-supported theory. But taken collectively they contradict all the predictions of the theory, leaving no support at all. The response of supporters of the Big Bang theory has been to continually add “parameters” to the theory to account for new discordant data. As a result, as Michael Disney has demonstrated, the theory, now with over 20 parameters to be adjusted, has never had any power to predict new results. So it lacks the basic hallmark of a sound scientific theory. Indeed, the recent, well-publicized results from the BiCEPS instrument has led many researchers to add yet more parameters to the theory to explain apparent contradictions between BiCEPS and Planck results.
In contrast, the data that contradicts the Big Bang theory can be explained far more simply with hypotheses that are consistent with a universe that had no beginning in time and no Big Bang. | 0.853101 | 4.032699 |
ESA PR 47-2015: LISA Pathfinder en route to gravitational wave demonstration
3 December 2015ESA's LISA Pathfinder lifted off earlier today on a Vega rocket from Europe's spaceport in Kourou, French Guiana, on its way to demonstrate technology for observing gravitational waves from space.
|Launch of LISA Pathfinder.
Credit: ESA–Stephane Corvaja, 2015
Gravitational waves are ripples in the fabric of spacetime, predicted a century ago by Albert Einstein's General Theory of Relativity, published on 2 December 1915.
Einstein's theory predicts that these fluctuations should be universal, generated by accelerating massive objects. However, they have not been directly detected to date because they are so tiny. For example, the ripples emitted by a pair of orbiting black holes would stretch a million kilometre-long ruler by less than the size of an atom.
LISA Pathfinder will test the extraordinary technology needed to observe gravitational waves from space. At its core is a pair of identical 46 mm gold–platinum cubes separated by 38 cm, which will be isolated from all external and internal forces acting on them except one: gravity.
The mission will put these cubes in the purest free-fall ever produced in space and monitor their relative positions to astonishing precision, laying the foundations for gravitational wave observatories in space.
Such future missions will be key partners to the ground sites already searching for these elusive cosmic messengers. Space and ground experiments are sensitive to different sources of gravitational waves, both opening up new possibilities to study some of the most powerful phenomena in the Universe.
The Vega launcher lifted off at 04:04 GMT (05:04 CET). About seven minutes later, after separation of the first three stages, the first ignition of Vega's upper stage propelled LISA Pathfinder into a low orbit, followed by another ignition about one hour and forty minutes into the flight.
|Launch of LISA Pathfinder. (Click here for further details and larger versions of this video.)|
The spacecraft separated from the upper stage at 05:49 GMT (06:49 CET). Controllers at ESA's operations centre in Darmstadt, Germany then established control.
Over the next two weeks, the spacecraft itself will raise the orbit's highest point in six critical burns.
The final burn will propel the spacecraft towards its operational location, orbiting around a stable virtual point in space called L1, some 1.5 million kilometres from Earth towards the Sun.
LISA Pathfinder is expected to reach its operational orbit about 10 weeks after launch, in mid February. After final checks, it will begin its six-month scientific mission at the beginning of March.
En route to the final orbit, the two cubes will be released from the locking mechanisms that hold them during launch and cruise. Once in orbit around L1, the final mechanisms will be unlocked and the cubes will no longer be in mechanical contact with the spacecraft.
A complex system of laser beams bouncing between the two cubes will measure how close to true free-fall they are to within a billionth of a millimetre – never previously achieved in space.
"Fundamental research tries to understand our world," says Johann-Dietrich Woerner, ESA's Director General.
"Einstein's theoretical findings are still very impressive. With LISA Pathfinder we will try to take a further step towards confirmation of one of Einstein's predictions: gravitational waves."
The spacecraft itself will be an active part of the experiment, firing tiny thrusters about 10 times a second to adjust its position and avoid making contact with the cubes, thus shielding them from any forces that would prevent them from moving under the effect of gravity alone.
If these extraordinarily high-precision measurements and operations can be achieved by LISA Pathfinder, the door will be open to building a future space observatory, capable of detecting the minute disturbances in spacetime produced by gravitational waves, which are expected to be a few tens of a billionth of a millimetre over distances of millions of kilometres.
"Gravitational waves are the next frontier for astronomers. We have been looking at the Universe in visible light for millennia and across the whole electromagnetic spectrum in just the past century," says Alvaro Giménez Cañete, ESA's Director of Science and Robotic Exploration.
"But by testing the predictions made by Einstein one hundred years ago with LISA Pathfinder, we are paving the road towards a fundamentally new window on the Universe."
LISA Pathfinder will operate as a physics laboratory in space. Over an intense period of six months, mission scientists will analyse the data received on Earth from each day's operations to plan the experiments to be performed on the satellite during the following days.
"After many years of development and testing on the ground, we are looking forward to the ultimate test, which can only be run in space," says Paul McNamara, ESA's LISA Pathfinder project scientist.
"In a few weeks, we will be exploring the very nature of gravity in space, gaining the confidence to build a full-scale space observatory to study the gravitational Universe in the future."
An industrial team led by the prime contractor, Airbus Defence & Space Ltd, built the spacecraft. Airbus Defence & Space GmbH provided the integrated LISA Technology Package payload and a consortium of European companies and research institutes provided its subsystems. NASA provided additional hardware and software that contributes to the mission by validating an alternative technological approach to keeping the spacecraft from making contact with the test masses.
"Integrating LISA Pathfinder posed many challenges, and we are extremely happy to see our trailblazing machine finally in space, ready to embark on its journey to L1, where it will pave the way for a new class of future space projects," concludes César García Marirrodriga, ESA's LISA Pathfinder project manager.
About the launcher
The launch of LISA Pathfinder was the last of five flights intended to demonstrate the capability and flexibility of the Vega launcher system, as part of ESA's Verta – Vega Research and Technology Accompaniment – programme.
During the Verta period, Vega has confirmed its versatility by delivering payloads into different orbits, demonstrating the full range of possible missions.
ESA was responsible for all Verta missions, which have refined and improved the launch system configuration and operations.
The Vega launches in 2015 (IXV, Sentinel-2A and LISA Pathfinder) have displayed the capacity of the system to reach three missions per year, providing confidence to customers and helping Arianespace to maintain its lead in this market segment.
The Vega launcher program is now fully qualified and ready for commercial exploitation by Arianespace.
About the European Space Agency
The European Space Agency (ESA) provides Europe's gateway to space.
ESA is an intergovernmental organisation, created in 1975, with the mission to shape the development of Europe's space capability and ensure that investment in space delivers benefits to the citizens of Europe and the world.
ESA has 22 Member States: Austria, Belgium, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Luxembourg, the Netherlands, Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland and the United Kingdom, of whom 20 are Member States of the EU.
ESA has established formal cooperation with seven other Member States of the EU. Canada takes part in some ESA programmes under a Cooperation Agreement.
By coordinating the financial and intellectual resources of its members, ESA can undertake programmes and activities far beyond the scope of any single European country. It is working in particular with the EU on implementing the Galileo and Copernicus programmes.
ESA develops the launchers, spacecraft and ground facilities needed to keep Europe at the forefront of global space activities.
Today, it develops and launches satellites for Earth observation, navigation, telecommunications and astronomy, sends probes to the far reaches of the Solar System and cooperates in the human exploration of space.
Learn more about ESA at www.esa.int.
For further information, please contact:
ESA Media Relations Office
Tel: +33 1 53 69 72 99 | 0.904407 | 3.713468 |
People used to argue about whether or not planets like the eight (or more) in our solar system were rare. Starting in the 1990s with the discovery of the first exoplanets, it became clear planets are common around other stars. What about planets without stars? Astronomers have identified a handful of such planets, but a new simulation developed at the University of Leiden suggests there could be as many as 50 billion rogue planets in the Milky Way.
In the immortal words of Douglas Adams: “Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is.” Rogue planets, even the largest among them, are but tiny specs floating in the infinite cosmic void without a star to point the way. That we’ve spotted any of them is a minor miracle, but the technology doesn’t exist to conduct an accurate survey of rogue planets. Thus, the importance of the new simulation.
The team built a simulation of 1,500 stars in a region of space called Orion Trapezium. Of course, we don’t know how many planets really exist around these stars, but the model included between four and six planets in orbit around about 500 of those planets. That’s a total of 2,522 planets in the model.
Over the course of millions of simulated years, gravitational interactions between the stars kicked more than 350 of those planets out of their solar systems. That works out to approximately 14 percent of all the planets in the model becoming rogue planets.
We don’t know how many planets exist in the galaxy, but there are about 200 billion stars. Most of them are in clusters not unlike Orion Trapezium. Estimating even a modest number of planets on average, that could mean billions of rogue planets in the Milky Way. The team used a number of guesstimates to arrive at 50 billion. Some of those might even have come from our own solar system.
Most of the confirmed or suspected rogue planets we’ve spotted are under 100 light years away, and several of those are too faint to characterize beyond the most basic details. If there are anywhere close to 50 billion planets without a star, it’s likely astronomers will discover more of them that are close enough to study with instruments like the upcoming James Webb Space Telescope.
Scientists May Have Detected the First Exoplanets in Another Galaxy
It stands to reason that if there are exoplanets orbiting stars in our own galaxy, then there would also be exoplanets in other galaxies.
Confirmed: Kepler Satellite Discovers 95 New Exoplanets
A review of Kepler data reveals 95 newly discovered exoplanets, one of which could be of great interest to astronomers.
Google Open Sources Exoplanet-Hunting AI
Late last year, Google showed how machine learning could help astronomers dig through the Kepler backlog, and it discovered a few new exoplanets in the process. Google has now open sourced the planet-spotting AI so anyone can give it a shot.
TRAPPIST-1 Exoplanets May Have Too Much Water for Life
Researchers from School of Earth and Space Exploration at Arizona State University say there might actually be too much water for the TRAPPIST-1 planets to harbor life. | 0.934195 | 3.66606 |
Image: Hubble spots a swarm of stars
This image from the NASA/ESA Hubble Space Telescope shows a dwarf galaxy named UGC 685. Such galaxies are small and contain just a tiny fraction of the number of stars in a galaxy like the Milky Way. Dwarf galaxies often show a hazy structure, an ill-defined shape, and an appearance somewhat akin to a swarm or cloud of stars—and UGC 685 is no exception to this. Classified as an SAm galaxy—a type of unbarred spiral galaxy—it is located about 15 million light-years from Earth.
These data were gathered under Hubble's LEGUS (Legacy ExtraGalactic UV Survey) program, the sharpest and most comprehensive ultraviolet survey of star-forming galaxies in the nearby universe.
LEGUS is imaging 50 spiral and dwarf galaxies in our cosmic neighborhood in multiple colors using Hubble's Wide Field Camera 3. The survey is picking apart the structures of these galaxies and resolving their constituent stars, clusters, groups and other stellar associations. Star formation plays a huge role in shaping its host galaxy. By exploring these targets in detail via both new observations and archival Hubble data, LEGUS will shed light on how stars form and cluster together, how these clusters evolve, how a star's formation affects its surroundings, and how stars explode at the end of their lives. | 0.845097 | 3.657904 |
Astronomy News with The Cosmic Companion Podcast February 11, 2020
|The Cosmic Companion||Feb 11|
In this week's episode of The Cosmic Companion, we look at how the smallest subatomic particles could be responsible for all the matter in the Universe, the icy heart of Pluto could control the climate on that world, an ancient galaxy is discovered that lived fast and died young, The CHEOPS Space Telescope takes its first image, and the Cocoon Galaxy is found to have a rare double core.
Video version of this podcast:
When matter first formed in the early Universe, theories suggest antimatter should have been created in the same, identical proportions. These two families of particles should have completely annihilated each other long ago, according to current theories. However, the Universe consists almost entirely of matter.
This may be explained if neutrinos, which only rarely interact with matter, changed just one in a billion particles of antimatter into matter, a new study suggests. This process may have produced gravitational waves which could be visible to a new generation of observatories. Finding such waves could prove this new theory, researchers suggest.
An artist's impression of CHEOPS in space. Image credit: ESA/ATG Media LabThe first space telescope from the European Space Agency dedicated to studying planets around other stars has returned its first image. The CHaracterising ExOPlanet Satellite, or CHEOPS, was launched on December 18th, on a mission to study exoplanets discovered by other telescopes. This first image was created to test systems on the spacecraft and on the ground, and further testing on the orbiting observatory will the carried out over the course of the next two months.
A giant heart-shaped feature on Pluto, named Tombaugh Regio, may play a significant role in driving climate on that world, a new study reveals. As the Heart of Pluto warms during the day, nitrogen is driven into the atmosphere. At night, this gas cools, falling back to Pluto as frozen nitrogen, in a regular cycle similar to a heartbeat, altering the climate of the dwarf planet.
Astronomers believe the cocoon galaxy and its smaller companion galaxy, called NGC 4485, are the products of an ancient collision between a pair of small spiral galaxies. Now, Iowa State astronomers have recognized a second galactic core within the larger galaxy. One of the cores is seen in visible light and has long been known to astronomers, while the newly-recognized second core is obscured by clouds, and is only visible in radio wavelengths.
An ancient galaxy recently discovered by astronomers apparently lived fast and died young. This family of stars thrived just one billion years after the Big Bang, experiencing a period of active star formation. Just 800 million years later, star production had ceased, leaving behind a dead galaxy. Researchers are uncertain why this galaxy, known as XMM-2599, died so quickly or what became of this stellar grouping after star production ceased.
On February 18th, I will interview Dr. Gillian Wilson of the University of California Riverside, about her work on the recent discovery of this fast-living galaxy. Make sure to listen in to Astronomy News with The Cosmic Companion right here, or on any major podcast provider.
Did you like this episode? Subscribe to The Cosmic Companion Newsletter! Astronomy News with The Cosmic Companion is also available as a podcast from all major podcast providers. Or, add this show to your flash briefings on Amazon Alexa. | 0.908497 | 3.744823 |
Module 02: Backyard Astronomy
This unit covers astronomical observations including night-sky observations, the moon’s characteristics, eclipses and other astronomical cycles.
1. Locate, interpret,
1.1 Identify reliable sources of astronomical information
1.2 Identify key terms and figures in astronomy
1.4 Discuss current astronomical advances and discoveries
2. Describe astronomical cycles and how they affect our view of the night sky
2.1 Apply scientific reasoning to describe the observed characteristics and differences between various celestial objects
2.2 Explain reoccurring cycles from earth-based observations
Welcome to our first full week of astronomy exploration. This is one of my favourite modules because we start by learning what we refer to as "backyard astronomy". This is the neat science that you can see from your very own backyard, and with very little technology.
Here are four (4) short videos to get you started on your backyard look at Astronomy.
Naked Eye Observations
We'll start with Naked-Eye Observations as they form the building blocks for budding astronomers. The night sky is much more than a bunch of little dots, a bright moon and the occasional shooting star. Once you learn more about what you are actually seeing in the sky, and why, you will be able to relax under the stars and share this information with your friends and family.
Cycles in the Sky
One of the most important aspects of naked-eye astronomy is the understanding of various Cycles in the Sky. Bodies spin, orbit and even wobble, and all in a predictable manner. As such, the cycles of all of the visible bodies can be anticipated and help you find your way around the night sky.
Of course, our own moon figures prominently into these cyclic observations, providing us with a consistent display of Moon Phases. Although the moon is the most viewed “out of the world” object, it is the subject of a surprisingly large number of simple scientific misconceptions. This video will help to dispel many of these mistaken beliefs and bring you a bit closer to our neighbour in the sky.
Occasionally, the bodies we see in the skies Eclipse and alter the “normal” view of the sky. Just about any object can be part of an eclipse, however we most often use this term when referring to the straight-line configuration of the Earth, Sun and either the moon or a planet. We will have a look at why they occur and what we can learn from them.
We're just getting started, but if your interest has already been piqued by this module's topics, I have some extra content for you to explore...
Below I've gathered some of the most interesting things I could find on NAKED-EYE OBJECTS, CYCLES, MOON PHASES, and ECLIPSES!
- THIS MONTH: NASA's What's up this month video will give you a quick synopsis of what's in the sky this month.
- THIS WEEK: Sky & Telescope offer up a weekly observations (check back often!)
- MOON PHASES: Dateandtime provides data on phases of the Moon - for anytime and for anyplace.
- THE EARTH'S MOVEMENT: Vsauce engages us with how the Earth's movement influences calendars and time!
- THE MOON (as a disco ball?): Vsauce again with what would actually occur (if this were possible)!
- ECLIPSES OVERVIEW: Vox provides a brief but effective overview of eclipses.
- ECLIPSE DATES: Dateandtime provides dates and anticipated views of upcoming eclipses - for anytime and for anyplace!
Videos have their (time) listed at the end the title below...so that you know what you're getting yourself into.
If you prefer watching in YouTube or full-screen please click on the title of the video - Or the YouTube icon on the video.
Naked Eye Observations:
Check out Sky & Telescope’s weekly observing update, Sky at a Glance, published every Friday. Not only do they provide simple sky maps and observing tips for the upcoming week, they also keep you up to date on the latest celestial events.
Cycles in the Sky:
Presented by Timeanddate.com
Moon Phases for THIS, or any year with full moon and new moon times.
- When is the next full moon?
- When are the best moon viewing times?
How Earth Moves (21:36)
Presented by Vsauce
Join Vsauce in this well presented journey into time, calendars, the Sun and Earth.
It is time to question... TIME: and how the Earth moves!
Presented by Vsauce
Just for FUN! and because I love the Vsauce channel !
For those who have ever wondered what it would be like to replace our Moon with a moon-sized disco ball; or wondered what a moon-size mirror orbiting the Earth as the International Space Station would look like from Earth? Explore!!
Presented by Scott Hobbis
A very short 2-D instructional animation created to show how the moon appears to change shape throughout its cycle.
Presented by Vox
A brief but effective overview of eclipses.
For detailed information on dates and times of eclipses (and transits), as well as visual representation of how the eclipses will appear in your region/city.
Concepts to Consider
- Why do you (or perhaps currently you don't...) have an interest in astronomy?
- What is your favourite space-related song - or one that stands out in your mind?
- What is something that you always thought was really neat about space/astronomy | 0.823399 | 3.672311 |
Stars are formed within large clouds of gas and dust known as stellar nurseries. While star formation was once seen as a simple gravitational process, we now know it is a complex dance of interactions. When one star forms it can send shock waves through the interstellar medium that trigger other stars to form. Supernovae and galactic collisions can trigger the creation of stars as well. One way to study stellar formation is to look at where stars form within a galaxy.
In some regions of our galaxy, such as the Orion Nebula, stars are actively forming. We can see stellar nurseries in action. But on a cosmic scale, these star-forming regions tend to fizzle out fairly quickly. So astronomers also look at the distribution of OB stars. These are massive, bright stars with short lifetimes. Because these stars only live for about a million years, they don’t have time to wander far from their place of birth. And because they are very bright they are easy to observe.
In the late 1800s, astronomer Benjamin Gould studied OB stars and found that many of them lie within a partial ring within our galaxy, titled about 20 degrees from the plane of the Milky Way. It came to be known as the Gould Belt. We are within this region of the Milky Way, which is one of the reasons there are so many bright stars in the night sky.
It isn’t clear what could have caused the Gould belt, but one idea is that a cluster of dark matter collided with molecular gas clouds in our galaxy. Similar star-forming belts are seen in other galaxies, so it was thought that this kind of dark matter collision could be a trigger.
But once again we’re beginning to learn that things aren’t quite so simple. Recently a team looked at data gathered from the Gaia spacecraft to make a detailed map of the position and motion of bright stars in the Gould Belt regions. From this, they created a 3-D map of interstellar gas and dust. They found that rather than being arranged in a ring structure, the stellar nurseries followed a narrow region that follows a sinusoidal curve. It is about 9,000 light-years across, and rises and falls about 500 light-years above and below the galactic plane.
This complex structure throws shade on the idea that Gould’s Belt exists at all. Its appearance could just be due to our view of this wave structure. It isn’t clear what formed this filament structure, but it does resemble a kind of ripple effect as if something collided with our galaxy.
Detailed surveys such as those gathered Gaia are still in the relatively early stages. We’re only beginning to create truly accurate maps of our galaxy. These new maps will certainly have much to teach us in the coming years.
Source: Alves, J., Zucker, C., Goodman, A.A. et al. “A Galactic-scale gas wave in the solar neighborhood” Nature (2020) | 0.881314 | 4.040614 |
For the past few months, NASA's New Horizons has been sending us images of Pluto and its moons via the Long Range Reconnaissance Imager (LORRI) camera, sending back the best pics of Pluto ever taken. But with the spacecraft now beginning its close encounter with the faraway worlds, it's now the Ralph camera's time to shine.
The name isn't an acronym. The 22-pound camera sits next to New Horizons' main ultraviolet imager, Alice, with both named after the Kramdens in "The Honeymooners." Where its spouse sees in ultraviolet, Ralph is meant to see in color in the visual spectrum and return color images of Pluto and Charon. It also is equipped to see in the visual range of methane, believed to be a big part of Pluto's composition.
Ralph was designed by Ball Aerospace, the company behind the five instruments aboard the Hubble Space Telescope and some of the optical equipment for the upcoming James Webb Space Telescope. Unlike either of those telescopes, the imager for New Horizons had to be designed to work in the far reaches of space.
"We've had to make sure we picked parts that were tolerant to radiation, tolerant to cold temperatures," says Lisa Hardaway, a program manager at Ball. "Coldness is another issue we had to deal with. And one of the ways we dealt with that is that we made the instrument athermal. In other words, as it gets colder, all the parts will start to shrink."
Hardaway says Ralph had to be covered up until it reached the vacinity of Mars, lest light from the Sun (and reflected light from the Moon and Earth) fry the sensitive cameras on board. They also had to make it as light as possible, so they hollowed out certain components and used a K1100 carbon fiber composite for construction.
In the next week (especially on the July 14th flyby), Ralph will take center stage, snapping photos of the surface of Pluto and Charon at a resolution of 800 feet per pixel from a height of 6,213 miles. (Or 325 meters per 10,000 km.) Those photos will come in RGB colors, methane spectrum, and monochromatic all at once, allowing for the possibility of an overlay to create detailed stack images.
And Ralph is in it for the long haul. After New Horizons has left the Pluto system, it will (pending budget approval) enter its secondary mission, characterizing another, smaller Kuiper Belt object, likely one about 30-ish miles in diameter. The candidate list has been narrowed down to two objects. Ralph will be there to see whichever tiny icy world is chosen.
"There's not much limiting on Ralph. There are actually no moving parts, so there's nothing that can break that way," Hardaway says. "We expect it to last just as long as the spacecraft will."
This post has been updated to correct the resolution measurements of Ralph. | 0.834154 | 3.333217 |
Welcome back to Messier Monday! We continue our tribute to our dear friend, Tammy Plotner, by looking at the open star cluster of Messier 48. Enjoy!
In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects in the night sky. In time, he would come to compile a list of approximately 100 of these objects, with the purpose of making sure that astronomers did not mistake them for comets. However, this list – known as the Messier Catalog – would go on to serve a more important function.
One of these is the open star cluster known as Messier 48 (aka. NGC 2548). Located approximately 1,500 light years from Earth in the direction of the Hydra constellation, Charles Messier actually got the position of this cluster wrong, a mistake which was corrected by Caroline Herschel in 1783 (hence why she is sometimes credited with its discovery). This object is visible to the naked eye on a clear night, providing light conditions are favorable.
At a modest 300 million years old, this group of about 50 easily visible stars and 80 total members spans an area of space which covers 23 light years. By studying proper motion over time with an astrograph telescope, astronomers have determined it is roughly 1500 light years away from our solar system. But how are determinations like this made? By long term studies and painstaking photographic plates, which address which stars are moving, at what speeds, and in what direction.
As Z. Y. Wu of the Shanghai Astronomical Observatory indicated in a 2001 study:
“Absolute proper motions, their corresponding errors and membership probabilities of 501 stars in the intermediate-age open cluster NGC 2548 region are determined from MAMA measurements of 10 photographic plates. The plates have the maximum epoch difference of 82 years and they were taken with the double astrograph. The average proper motion precision is 1.18 mas yr -1. These proper motions are used to determine the membership probabilities of stars in the region. The number of stars with membership probabilities higher than 0.7 is 165.”
So now we understand how to determine distance, but how do astronomers determine age? As M. Hancock (et al) indicated in their 2008 study:
“We present an empirical assessment of the use of broad-band optical colours as age indicators for unresolved extragalactic clusters and investigate stochastic sampling effects on integrated colours. We use the integrated properties of Galactic open clusters (OCs) as models for unresolved extragalactic clusters. The population synthesis code Starburst99 (SB99) and four optical colours were used to estimate how well we can recover the ages of 62 well-studied Galactic OCs with published ages. We provide a method for estimating the ages of unresolved clusters and for reliably determining the uncertainties in the age estimates. Our results support earlier conclusions based on comparisons to synthetic clusters, namely the (U?B) colour is critical to the estimation of the ages of star-forming regions. We compare the observed optical colours with those obtained from SB99 using the published ages and get good agreement.”
History of Observation:
According the SEDS, this open cluster was discovered by Charles Messier and cataloged by him on February 19, 1771. “Cluster of very small [faint] stars, without nebulosity; this cluster is at a short distance from the three stars that form the beginning of the Unicorn’s tail.”
However, as he did an error in data reduction, he gave a wrong position in his catalog so that the object was missing until Oswald Thomas identified it in 1934, and independently T.F. Morris in 1959. The identification of M48 by Oswald Thomas was confused by some historians, who have claimed erroneously instead that he had identified M47.
As M48 was lost, two independent rediscoveries occurred: First, Johann Elert Bode apparently found it in or before 1782, and second, Caroline Herschel independently rediscovered it in 1783; “March 8th 83. At an equal distance from 29 [Zeta] and 30 Monocerotis, making an equilateral triangle with those two stars is a nebulous spot. By the telescope it appears to be a cluster of scattered stars. It is not in Messier catalogue.”
This latter discovery was published by Caroline’s famous brother, William Herschel, who included it in his catalog as H VI.22 on February 1, 1786. “A beautiful Cluster of much compressed stars, considerably rich. 10 or 12′ diameter. Caroline Herschel discovered it in 1783.”
John Herschel would visit Messier 48 often in his NGC cataloging efforts, describing it as, “A superb cluster which fills the whole field; stars of 9th and 10th to the 13th magnitude – and none below, but the whole ground of the sky on which it stands is singularly dotted over with infinitely minute points [stars]. Place that of a bright star, the southern of two which point into the concavity of an arc.”
Once again, Messier’s mistake would be missed when it was re-observed by Admiral Smyth, who described this object as follows:
“A neat but minute double star, in a tolerably compressed cluster on the Unicorn’s flank, and lying 14deg south-east of Procyon. A 9 1/2 [mag], and B 10, both white. This object is in the middle of a splendid group, in a rich splashy region of stragglers, which fills the field of view, and has several small pairs, chiefly of the 9th magnitude. It was discovered by Miss Herschel in 1783, and was classed by WH [William Herschel] in February, 1783.”
Thanks to careful research done by Owen Gingerich in 1960, we now know exactly what happened:
“Although the circumstances of M48 are not so obvious, only one cluster of the size and brightness likely to be recorded by Messier is found in the region near “the three stars that form the beginning of the unicorn’s tail” (Zeta, 27, and 28 Monocerotis). Dr. Morris has pointed out that this cluster, NGC 2548, has the same right ascension as the position given for M48. (Allowance must, of course, be made for precession in comparing Messier’s figures with modern positions). The declination disagrees by about 5 degrees. Since no conspicuous star is located 2 1/2 degrees away in declination, we cannot account for this position by another error in sign. It seems unlikely that the comparison star was misidentified, since the right ascension is probably correct. Messier did not publish the name of the star used, and his original records are apparently no longer extant. Thus, a careful survey of the region described by Messier leads to the conclusion that NGC 2548 is the cluster the French observer intended as his 48th object, for lack of any cluster nearby that fits the description.”
May you find it a bit easier!!
Locating Messier 48:
The diamond-bright stars of winter help make locating M48 a little easier, as it is located just a little less than a hand span southeast of Procyon (Alpha Canis Minor) – or about 3 degrees southeast of Zeta Monocerotis. Like M44 in Cancer, M48 lies within the limits of unaided sight. It is quite large and will show several dozen stars easily to almost all binoculars and be well resolved in telescopes of any aperture. Be sure to use low magnification to see it best! Because Messier 48 is bright, it makes a fine object for urban sky conditions and moonlit nights.
And here are the quick facts on this Messier Object to help you get started:
Object Name: Messier 48
Alternative Designations: M48, NGC 2548
Object Type: Open Galactic Star Cluster
Right Ascension: 08 : 13.8 (h:m)
Declination: -05 : 48 (deg:m)
Distance: 1.5 (kly)
Visual Brightness: 5.5 (mag)
Apparent Dimension: 54.0 (arc min)
We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons. | 0.913126 | 3.858334 |
|“||Between Sunside and Darkside, the Ribbon is a continuous garden swimming in the eternal morning of an eternal [summer].||”|
|— Famed elven poet and explorer Aldyn Leafbower.|
Radole was a rare tidally locked planet, which means that the same side of the planet was always facing its sun, much like the same side of the moon Selûne was always facing Toril. The most obvious effect of this was that the planet did not have day or night cycles. This resulted in extraordinary variations in temperature and climate across the whole planet that barely deviated throughout the year in any given location. Radole's Sunside was so hot that even some lighter metals melted. Its Darkside was so cold, that oxygen could liquefy. Only in the Ribbon, the border between light and dark, could life thrive, and here, the sun was always visible in perpetual dusk or dawn, depending on which hemisphere one resided.
Sunside was free of clouds and appeared red from space, whereas Darkside, being perpetually within its own shadow had few discernible features from orbit. Cloud cover over the Ribbon was variable with gaps.
Radole had a radius of 3,700 miles (6,000 kilometers) at the equator. It was slightly oblate and had no tilt to its revolution. It had no moons.
The rugged planet had many tall mountain ranges and plunging valleys, but there were no large bodies of seawater on the planet, which was thus considered to contain a single continent. Darkside contained one impressive plateau of enormous size called the Plateau of Night. In the Ribbon, the terrain contained rolling hills and fertile plains instead, with many small lakes and rivers providing irrigation.
Scholars who studied such matters believed that Radole was a "dead world" geologically, meaning that it no longer had any volcanic activity.
In Darkside, in the utter darkness farthest from the suns light, there were lakes of liquid oxygen. The largest of these were dubbed the Ocean of Death and the Ocean of Nightmares. In Sunside, it was so hot that there were lakes of molten metals, such as tin, with floating "islands" of half-melted lead. The two biggest were named the Hellspawn Sea and the Dragonbath.
The Ribbon was a paradise by any comparisons. It was a region about 200 miles (320 kilometers) wide. On its border with Darkside, there was a straight and tall mountain range, the Shieldwall Mountains that looped around the planet from pole to pole to pole. These mountains were a little under three miles (five kilometers) high, and from them, fresh water cascaded down into the Ribbons valleys and lakes.
Source: PP, p. 13
As already stated, the temperature on Darkside was exceptionally cold. On the equator, at the point farthest from the sun, the temperature was −310 ℉ (−190 ℃). This was cold enough to keep oxygen in its liquid form. So, besides being too cold for standard lifeforms to survive, the air was completely unbreathable. Temperatures rapidly increased as one move closer to the Ribbon.
Clouds covered the Darkside, and these frequently—about once every 72 hours—dropped precipitation of "rain" of liquid oxygen or "snow" of water ice and oxygen crystals. The winds were exceptionally powerful and dangerous and resulted in blizzards of oxygen snow.
The total opposite of hellish environments was on the other side of the planet. Here, the highest temperatures reached 620 ℉ (330 ℃). As already noted, this was hot enough to melt softer metals such as lead or tin. As in Darkside, the temperatures rapidly changed to habitable ones as one moved closer to the Ribbon.
There were no clouds on Sunside, as the heat drove all the water away, and thus no precipitation of any kind. Powerful dry winds rushed over the rugged surface.
The weather of the Ribbon, in stark contrast, was idyllic, ranging between 70 ℉ (21 ℃) and 80 ℉ (27 ℃). Pleasant breezes carried with them warm and dry air from Sunside, while the Shieldwall Mountains blocked most of the bitter cold winds from Darkside. Temperate rains fell from the clouds above the Ribbon about once or twice every tenday by Toril's time.
Flora & FaunaEdit
In Sunside, there were many types of giant insects with metallic exoskeletons. A common example of such a creature was the steelback beetle. Scholars speculated that these creatures converted sunlight into energy and obtained nourishment from the soil or from eating other such insects.
The Ribbon was bountiful with all manner of flowering plants, grains, trees, and grasses, with the absence of any dangerous plant life.
Radole was inhabited by humans, elves, dwarves, and halflings but entirely absent of goblinoids, orcs, or other typically evil humanoids. These all lived, of course, in the Ribbon. There was one account of a dracon colony as well, and some further said that unicorns could be found in the Ribbon.
Beyond the humanoid life of the Ribbon, metallic dragons inhabited Sunside, including a particular subtype of metallic dragon known as mithril dragons. The dragons enjoyed riding the thermal winds over the mountains. Some sages insisted that these dragons could not be the same metallic dragons seen on other worlds, as Sunside was too hot either for them, but others saw no issue with magical beings like dragons adapting to such hot conditions.
Rumors claimed a population of shadowy creatures roaming the barren landscape, and these were true—a gate to the Negative Energy Plane existed at the coldest point on the planet, and through it passed many sentient shadows. The shadows never passed over the mountains into the Ribbon, since it was never night there.
The inhabitants of Radole were keenly aware that their world was a ultimate paradise within the Ribbon, and for this reason, they were exceedingly hesitant to permit visitors to their planet and viewed any rare visitors with high levels of distrust if not outright xenophobia. The planet was defended by the Radole Navy, the Imperial Radole Fleet, which had over a hundred vessels consisting of 35 hammerships and about 70 smaller support vessels, including damselflies, dragonflies, and wasps. These space vessels formed an orbiting wall of defense against incoming spacecraft.
On the ground, the planet was protected by the Radole Planetary Defense Force (PDF), which included warriors, mages, and clerics. Anyone permitted clearance to land on the planet would be escorted down by the navy and then escorted anywhere they traveled on the planet by members of the PDF.
Some spread rumors that Radole necromancers had placed "minefields" of skeletons in orbit about their planet, which would unfold when entering the air envelope of a passing ship to attack, but these were only rumors.
Other than the navy and the PDF, however, the planet was contained a pacifist culture. The Ribbon acted as a single planetary-wide nation. Its citizens tended strongly towards lawfulness, and their law books even included rules on birth customs or romantic relationships. Lawbreakers were essentially shunned from society, and this alone was usually sufficient for maintaining law and order.
Visitors were treated to a tougher standard and were guilty until proven innocent of any alleged crimes against even the most mundane laws. Rulings were carried out by a Judiciary Committee, who had complete power over judging and sentencing of off-worlders. Typically, the sentence would be death, but actual executions were rarely carried out; instead, sentences were usually suspended in exchange for the convicted person performing a monumental task in benefit of Radole society. A "convict" successfully completing the task—which might involve something as dangerous as recovering specimens from either Sunside or Darkside—would be banished instead of executed.
To be a citizen of the Ribbon, one must have been born on the Ribbon. Only two cases have been recorded of a visitor being granted even the freedom to travel without PDF escort, and both examples involved elves.
The recorded history of the inhabitants of Radole covered several thousand years, but the ancient history of Radole was shrouded in mystery. Nevertheless, nearly all historians and scholars agreed that the central region of the planet must have been both terraformed and seeded with lifeforms. The Shieldwall Mountains were too regular to have been natural; they must have been artificially constructed, most likely with the intention of holding back the glaciers and winds from Darkside so that life could thrive in the Ribbon. Likewise, the rivers of the Ribbon always occurred at regular intervals of 10.25 miles (16.50 kilometers) apart. Furthermore, the stable balance of non-hostile animals, plants, and intelligent life could only have been planned; someone or something must have brought all of these lifeforms to Radole intentionally.
Beyond even these mysteries were the archeological evidences of life before the current civilizations. Deep within the Shieldwall Mountains, gigantic, smooth-walled tunnels were discovered that led deep into the mountains where they ended in enormous chambers hundreds of feet high and thousands wide. The walls of these ancient chambers were covered in murals and carvings with abstract symbology. Among these symbols were the distinctive markings of the Juna,[note 1] three-pointed stars and three-pointed petals. According to dwarven archeologists, the tunnels were not bored into the mountains; the mountains were built atop the structures of the tunnels and chambers! Most held to the theory that the Juna once called Radole home before bringing other creatures to live there.
In 1362 DR, in Realmspace, the Cloakmaster, Teldin Moore, was able to, by means of a magic amulet, see through the eyes of the Spelljammer. When he described what he was seeing to his friends Hectate and Vallus Leafbower, they suspected that he was seeing Radole in Winterspace. A course was plotted for this crystal sphere in response, and it was in Winterspace near Radole that a major battle of the Second Unhuman War then occurred.
- The Radiant Dragon
- ↑ 1.0 1.1 The Juna are not specifically named in the text of Practical Planetology; however the descriptions of their three-pointed symbols make it undoubtable that the Juna described in the Cloakmaster Cycle of novels are being referred to here.
Disclaimer: The views expressed in the following links do not necessarily represent the views of the editors of this wiki, nor does any lore presented necessarily adhere to established canon.
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 Nigel Findley (July 1991). Practical Planetology. (TSR, Inc.), pp. 13–16. ISBN 156-076134-2.
- ↑ 2.0 2.1 Elaine Cunningham (November 1992). The Radiant Dragon. (TSR, Inc.), p. 311. ISBN 1-56076-346-9.
- ↑ Elaine Cunningham (November 1992). The Radiant Dragon. (TSR, Inc.), p. 26. ISBN 1-56076-346-9.
- ↑ 4.0 4.1 Elaine Cunningham (November 1992). The Radiant Dragon. (TSR, Inc.), pp. 154–155. ISBN 1-56076-346-9.
- ↑ Dale "slade" Henson (April 1991). Realmspace. Edited by Gary L. Thomas, Karen S. Boomgarden. (TSR, Inc), p. 25. ISBN 1-56076-052-4.
- ↑ 6.0 6.1 6.2 Poster included in Nigel Findley (July 1991). Practical Planetology. (TSR, Inc.). ISBN 156-076134-2.
- ↑ Elaine Cunningham (November 1992). The Radiant Dragon. (TSR, Inc.), chaps. 20–21. ISBN 1-56076-346-9. | 0.862049 | 3.444892 |
Using gravitational "lenses" in space, University of Utah astronomers discovered that the centers of the biggest galaxies are growing denser -- evidence of repeated collisions and mergers by massive galaxies with 100 billion stars.
This image, taken by the Hubble Space Telescope, shows
a ring of light from a distant galaxy created when a closer
galaxy in the foreground – not shown in this processed
image – acts as a “gravitational lens” to bend the light
from the more distant galaxy into the ring of light,
known as an Einstein ring. In a new study, University of
Utah astronomer Adam Bolton and colleagues measured
these Einstein rings to determine the mass of 79 lens
galaxies that are massive elliptical galaxies, the largest
kind of galaxy with 100 billion stars. The study found
the centers of these big galaxies are getting denser over
time, evidence of repeated collisions between massive
galaxies. (Credit: Joel Brownstein, University of Utah,
for NASA/ESA and the Sloan Digital Sky Survey)
"We found that during the last 6 billion years, the matter that makes up massive elliptical galaxies is getting more concentrated toward the centers of those galaxies. This is evidence that big galaxies are crashing into other big galaxies to make even bigger galaxies," says astronomer Adam Bolton, principal author of the new study.
"Most recent studies have indicated that these massive galaxies primarily grow by eating lots of smaller galaxies," he adds. "We're suggesting that major collisions between massive galaxies are just as important as those many small snacks."
The new study -- published recently in The Astrophysical Journal -- was conducted by Bolton's team from the Sloan Digital Sky Survey-III using the survey's 2.5-meter optical telescope at Apache Point, N.M., and the Earth-orbiting Hubble Space Telescope.
The telescopes were used to observe and analyze 79 "gravitational lenses," which are galaxies between Earth and more distant galaxies. A lens galaxy's gravity bends light from a more distant galaxy, creating a ring or partial ring of light around the lens galaxy.
The size of the ring was used to determine the mass of each lens galaxy, and the speed of stars was used to calculate the concentration of mass in each lens galaxy.
Bolton conducted the study with three other University of Utah astronomers -- postdoctoral researcher Joel Brownstein, graduate student Yiping Shu and undergraduate Ryan Arneson -- and with these members of the Sloan Digital Sky Survey: Christopher Kochanek, Ohio State University; David Schlegel, Lawrence Berkeley National Laboratory; Daniel Eisenstein, Harvard-Smithsonian Center for Astrophysics; David Wake, Yale University; Natalia Connolly, Hamilton College, Clinton, N.Y.; Claudia Maraston, University of Portsmouth, U.K.; and Benjamin Weaver, New York University.
Big Meals and Snacks for Massive Elliptical Galaxies
The new study deals with the biggest, most massive kind of galaxies, known as massive elliptical galaxies, which each contain about 100 billion stars. Counting unseen "dark matter," they contain the mass of 1 trillion stars like our sun.
"They are the end products of all the collisions and mergers of previous generations of galaxies," perhaps hundreds of collisions," Bolton says.
Despite recent evidence from other studies that massive elliptical galaxies grow by eating much smaller galaxies, Bolton's previous computer simulations showed that collisions between large galaxies are the only galaxy mergers that lead, over time, to increased mass density on the center of massive elliptical galaxies.
When a small galaxy merges with a larger one, the pattern is different. The smaller galaxy is ripped apart by gravity from the larger galaxy. Stars from the smaller galaxy remain near the outskirts -- not the center -- of the larger galaxy.
"But if you have two roughly comparable galaxies and they are on a collision course, each one penetrates more toward the center of the other, so more mass ends up in the center," Bolton says.
Other recent studies indicate stars are spread more widely within galaxies over time, supporting the idea that massive galaxies snack on much smaller ones.
"We're finding galaxies are getting more concentrated in their mass over time even though they are getting less concentrated in the light they emit," Bolton says.
He believes large galaxy collisions explain the growing mass concentration, while galaxies gobbling smaller galaxies explain more starlight away from galactic centers.
"Both processes are important to explain the overall picture," Bolton says. "The way the starlight evolves cannot be explained by the big collisions, so we really need both kinds of collisions, major and minor -- a few big ones and a lot of small ones."
The new study also suggests the collisions between large galaxies are "dry collisions" -- meaning the colliding galaxies lack large amounts of gas because most of the gas already has congealed to form stars -- and that the colliding galaxies hit each other "off axis" or with what Bolton calls "glancing blows" rather than head-on.
Sloan Meets Hubble: How the Study Was Conducted
The University of Utah joined the third phase of the Sloan Digital Sky Survey, known as SDSS-III, in 2008. It involves about 20 research institutions around the world. The project, which continues until 2014, is a major international effort to map the heavens as a way to search for giant planets in other solar systems, study the origin of galaxies and expansion of the universe, and probe the mysterious dark matter and dark energy that make up most of the universe.
Bolton says his new study was "almost gravy" that accompanied an SDSS-III project named BOSS, for Baryon Oscillation Spectrographic Survey. BOSS is measuring the history of the universe's expansion with unprecedented precision. That allows scientists to study the dark energy that accelerates expansion of the universe. The universe is believed to be made of only 4 percent regular matter, 24 percent unseen "dark matter" and 72 percent yet-unexplained dark energy.
During BOSS' study of galaxies, computer analysis of light spectra emitted by galaxies revealed dozens of gravitational lenses, which were discovered because the signatures of two different galaxies are lined up.
Bolton's new study involved 79 gravitational lenses observed by two surveys:
- The Sloan Survey and the Hubble Space Telescope collected images and emitted-light color spectra from relatively nearby, older galaxies -- including 57 gravitational lenses -- 1 billion to 3 billion years back into the cosmic past.
- Another survey identified 22 lenses among more distant, younger galaxies from 4 billion to 6 billion years in the past.
The rings of light around gravitational-lens galaxies are named "Einstein rings" because Albert Einstein predicted the effect, although he wasn't the first to do so.
"The more distant galaxy sends out diverging light rays, but those that pass near the closer galaxy get bent into converging light rays that appear to us as of a ring of light around the closer galaxy," says Bolton.
The greater the amount of matter in a lens galaxy, the bigger the ring. That seems counterintuitive, but the larger mass pulls with enough gravity to make the distant star's light bend so much that lines of light cross as seen by the observer, creating a bigger ring.
If there is more matter concentrated near the center of a galaxy, the faster stars will be seen moving toward or being slung away from the galactic center, Bolton says.
Bolton and colleagues acknowledge their observations might be explained by theories other than the idea that galaxies are getting denser in their centers over time:
- Gas that is collapsing to form stars can increase the concentration of mass in a galaxy. Bolton argues the stars in these galaxies are too old for that explanation to work.
- Gravity from the largest massive galaxies strips neighboring "satellite" galaxies of their outskirts, leaving more mass concentrated in the centers of the satellite galaxies. Bolton contends that process is not likely to produce the concentration of mass observed in the new study and explain how the extent of that central mass increases over time.
- The researchers merely detected the boundary in each galaxy between the star-dominated inner regions and the outer regions, which are dominated by unseen dark matter. Under this hypothesis, the appearance of growing galaxy mass concentration over time is due to a coincidence in researchers' measurement method, namely that they are measuring younger galaxies farther from their centers and measuring older galaxies closer to their centers, giving an illusion of growing mass concentration in galactic centers over time. Bolton says this measurement difference is too minor to explain the observed pattern of matter density within the lens galaxies. | 0.845794 | 4.074474 |
NASA’s Fermi Explores High-energy ’Space Invaders’
Since its launch last June, NASA’s Fermi Gamma-ray Space Telescope has discovered a new class of pulsars, probed gamma-ray bursts and watched flaring jets in galaxies billions of light-years away. At the American Physical Society meeting in Denver, Colo., Fermi scientists revealed new details about high-energy particles implicated in a nearby cosmic mystery.Fermi’s Large Area Telescope is a state-of-the-art gamma-ray detector, but it’s also a terrific tool for investigating the high-energy electrons in cosmic rays," said Alexander Moiseev, who presented the findings. Moiseev is an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md.Cosmic rays are hyperfast electrons, positrons, and atomic nuclei moving at nearly the speed of light. Astronomers believe that the highest-energy cosmic rays arise from exotic places within our galaxy, such as the wreckage of exploded stars.Fermi’s Large Area Telescope (LAT) is exquisitely sensitive to electrons and their antimatter counterparts, positrons. Looking at the energies of 4.5 million high-energy particles that struck the detector between Aug. 4, 2008, and Jan. 31, 2009, the LAT team found evidence that both supplements and refutes other recent findings.Compared to the number of cosmic rays at lower energies, more particles striking the LAT had energies greater than 100 billion electron volts (100 GeV) than expected based on previous experiments and traditional models. (Visible light has energies between two and three electron volts.) The observation has implications similar to complementary measurements from a European satellite named PAMELA and from the ground-based High Energy Stereoscopic System (H.E.S.S.), an array of telescopes located in Namibia that sees flashes of light as cosmic rays strike the upper atmosphere.Last fall, a balloon-borne experiment named ATIC captured evidence for a dramatic spike in the number of cosmic rays at energies around 500 GeV. "Fermi would have seen this sharp feature if it was really there, but it didn’t." said Luca Latronico, a team member at the National Institute of Nuclear Physics (INFN) in Pisa, Italy. "With the LAT’s superior resolution and more than 100 times the number of electrons collected by balloon-borne experiments, we are seeing these cosmic rays with unprecedented accuracy.Unlike gamma rays, which travel from their sources in straight lines, cosmic rays wend their way around the galaxy. They can ricochet off of galactic gas atoms or become whipped up and redirected by magnetic fields. These events randomize the particle paths and make it difficult to tell where they originated. In fact, determining cosmic-ray sources is one of Fermi’s key goals.What’s most exciting about the Fermi, PAMELA, and H.E.S.S. data is that they may imply the presence of a nearby object that’s beaming cosmic rays our way. "If these particles were emitted far away, they’d have lost a lot of their energy by the time they reached us," explained Luca Baldini, another Fermi collaborator at INFN.If a nearby source is sending electrons and positrons toward us, the likely culprit is a pulsar -- the crushed, fast-spinning leftover of an exploded star. A more exotic possibility is on the table, too. The particles could arise from the annihilation of hypothetical particles that make-up so-called dark matter. This mysterious substance neither produces nor impedes light and reveals itself only by its gravitational effects."Fermi’s next step is to look for changes in the cosmic-ray electron flux in different parts of the sky," Latronico said. "If there is a nearby source, that search will help us unravel where to begin looking for it." | 0.882313 | 3.926855 |
How Many Planets Are There in The Solar System?
Earth is not alone as a planet. Since the beginning of our world, its shared space with its stellar sister and brothers of over 4 billion years, all playing a significant role in the ecosystem of our cosmic home. From mighty Jupiter to nearby Mars, our system is populated with planets as diverse and strange as the wonders of our own world.
Over the centuries of astronomy, new observations have been made. Studies conducted, research done, and new conclusions reached. Some of those conclusions relate to the planets. One, specifically, is how many. Well, you might think! That’s easy! Isn’t it nine? And in fact, that’s no longer correct. No longer correct – but how?
Well, when you hear the name “Pluto” you might imagine a few things. A small, distant, and cold world well beyond our stellar reach comes to mind, one so far it can only make solar orbit every two hundred years or so. Discovered in the 1930’s, it was originally thought to be the system’s ninth planet. As discoveries were made and evaluations conducted, this conclusion was challenged.
In 2005, another small, isolated body of icy-rock was discovered beyond Pluto, named Eris by NASA. Eris, in fact, is larger than Pluto, leading astronomers to redefine how to classify stellar bodies. In short, Pluto and Eris are now referred to as “Dwarf Planets.” Others refer to them as planetoids, but the conclusion is the same: Pluto no longer fit the typical characteristics of a planet. You can imagine this has been met with a variety of criticism – how can you change what it means to be a “planet?”
Dwarf Planets and the Kuiper Belt
The primary reason Pluto is no longer considered a planet is because of its reclassification. The discovery of Eris (and objects like it) gave astronomers a greater understanding of planetoid qualities. Today, both Eris and Pluto are now considered “dwarf planets.”
Aside from dimensions and size, there are reasons for this classification.
- Dwarf planets still orbit the sun
- Still large enough to maintain its own gravitational pull
- However, has not cleared the orbit of other objects
You might wonder what’s meant by “other objects.” Specifically, in relation to Pluto and Eris. These dwarf planets originate from something called the Kuiper Belt, some billions of miles distant from Neptune. Essentially, it’s an ovular shape composed of millions of icy-rocky bodies, likely fragments from the solar system’s creation. Beyond this is the Oort Cloud, even farther from our system. However, the two should not be confused.
Since Pluto and Eris have not cleared the orbit of the Kuiper belt (aka other rock-ice objects) they are defined as Dwarf Planets.
The Planets in the Solar System
With an understanding of why the Solar System is comprised of eight planets versus nine, we can break them down in their position and orbit.
At the center of our system is, of course, the Sun. All planets and stellar bodies native to our system revolve around the sun, and its powerful heat/light is what drives life here on Earth.
The first and smallest planet in our solar system. Because Mercury is so close to the sun, its uninhabitable. It has no atmosphere, no oxygen, and average daily temperatures reach around 400 degrees Celsius.
Although similar in size to planet Earth, Venus is quite different. It’s surrounded by a constant storm an inhospitable terrain, and happens to be the hottest planet in our system. That’s because the thick clouds cloaking it create an infinite greenhouse effect, trapping and cycling heat.
It’s home! It’s the only planet we know (so far) capable of supporting life. Home to millions of incredible species, deep oceans, thick forests, various terrains, and thousands of societies, everything that we ever know and ever occurred as humans happened here.
The pale red dot, Mars has fascinated astronomers for years with characteristics quite similar to earth. Many photos exist of the planet’s surface thanks to machines like the Curiosity rover, which have revealed rocky terrain and frozen bodies of brine (heavily salted) water. Some have speculated, in the right conditions, this fourth world could support life like on Earth.
Fifth and largest, mighty Jupiter is a gas giant consumed by swirling storms of cold ammonia. It’s most known for its “Great Red Spot,” a constant hurricane-like storm. Jupiter also has quite the family of moons, with over 75 lunar objects hanging in its orbit.
The second largest planet, Saturn is the sixth world in our system. Most known for its beautiful rings, which are clusters of millions of icy objects. As a gas giant (like Jupiter), it’s made mostly of helium and hydrogen.
Aside from a name spawning a lifetime of jokes, this planet is distant, dark, and mysterious. It has its own rings – like Saturn – though smaller in comparison. Its atmosphere is made of hydrogen sulfide and it’s an ice giant, mostly comprised of water and ammonia.
The last traditionally defined planet. Far Neptune is the eighth planet in our solar system, it’s another ice giant with one special property: winds. Frozen chunks of ice and methane are flung around the gassy world, estimated to be around 1200MPH/2000KMH.
As you can see, the nature of astronomy and our understanding of astrophysics is always evolving. The discovery of icy bodies from the Kuiper Belt and Oort Cloud changed how astronomers perceive planets and planetoids, shifting the definition of Pluto. As we continue to learn about our solar system, newer facts are always coming to light. Better technology allows us to send rovers to different worlds and satellite imagery demonstrates new visual factoids about things we know.
We hope this quick guide on the solar system rouses your enthusiasm to learn more. We’ve only touched the surface and there are still so many things to know about our solar system and the cosmos as a whole. But, now you know – it’s eight planets, not nine! | 0.882573 | 3.656715 |
NASA's Voyager 2 Probe Is About To Slip Beyond The Boundaries Of Our Solar System And Into Interstellar Space
To boldly go where one Voyager has gone before! NASA is reporting that, according to a familiar increase in cosmic radiation, the Voyager 2 probe may be about to follow in the footprints of Voyager 1 by crossing the boundary of the heliosphere and into interstellar space.
Image Credit: NASA/JPL-Caltech
Voyager 2 began it's journey away from Earth back in 1977 and is roughly 11 billion miles from home. In 2007 it entered the outermost layer of the heliosphere, and now based on data recorded by the probe's Cosmic Ray Subsystem instrument, NASA scientists say there's a good chance that it is about to reach the boundary (known as the heliopause) and join Voyager 1 in the history books as the second human-made object to go interstellar. Back in August, the cosmic rays hitting the probe increased by five percent. According to Science Alert, similar increases were detected by Voyager 1 back in May of 2012, and a few months later it crossed over. But that isn't a guarantee for Voyager 2. "Voyager team members note that the increase in cosmic rays is not a definitive sign that the probe is about to cross the heliopause," NASA wrote in an announcement. "Voyager 2 is in a different location in the heliosheath – the outer region of the heliosphere – than Voyager 1 had been, and possible differences in these locations means Voyager 2 may experience a different exit timeline than Voyager 1."
"We're seeing a change in the environment around Voyager 2, there's no doubt about that," said Voyager Project Scientist Ed Stone. "We're going to learn a lot in the coming months, but we still don't know when we'll reach the heliopause. We're not there yet – that's one thing I can say with confidence." So while the timeline is uncertain, Voyager 2 is getting closer to the heliopause and will eventually cross it. For more precise information on how far both probes are from Earth, their radiation levels, and the status of their various instruments, check out the Jet Propulsion Lab's Voyager Mission Status website. | 0.808747 | 3.143104 |
Methane found in Mars atmosphere / Scientist offers a few theories for presence of gas exuded by life forms
Mars scientists in Europe and the United States have detected tantalizing signs of methane gas in the Martian atmosphere, and cannot yet explain why it's there.
Methane is commonly exuded by living organisms and fermentation. It can also belch to the surface during volcanic eruptions, and can be carried by comets that at times have crashed into Earth and other planets.
The amounts of atmospheric methane detected by instruments aboard the European Space Agency's Mars Express spacecraft now orbiting the planet are extremely small -- barely more than 10 parts per billion, but the find is already creating a major buzz among Mars researchers.
Steven Squyres, now famed as the leader of the team guiding the Mars rovers Spirit and Opportunity on their epochal tour of the Martian surface, would not talk to a reporter about the European find this week after a talk to a major astrobiology conference at NASA's Ames Research Center in Mountain View.
But Bernard Foing, an organic chemist on the Mars Express team who also attended the astrobiology meeting, cited three possible major sources for the methane.
First, it could be emerging from a Martian volcano that is unexpectedly erupting right now, even though little or no volcanic activity has been observed on Mars from high-resolution ground-based telescopes on Earth or from orbiters circling the Red Planet.
Second, the gas could have carried into the planet's atmosphere by a grazing comet or asteroid, even by one that hit the surface very recently.
And third -- probably the least likely but certainly the most dramatic of all -- it could be emerging from beneath the Martian surface where some kind of living organisms -- bacteria, perhaps -- might be surviving and nourishing themselves by chewing on rocks containing chemicals that serve as a source of energy.
One thing is certain, however: Wherever the methane comes from, it must be either of relatively recent origin or be continuously replenished, because the gas lasts only a few hundred years or so before it oxidizes into water and carbon dioxide.
"We cannot know more until we find out more," Foing said in an interview, "and that will take many more observations both to confirm that the gas is there and to locate its source on the planet."
The European Space Agency first disclosed the methane find Monday after Vittorio Formasino, the lead scientist for the spacecraft's Planetary Fourier Spectrometer, confirmed that the instrument had indeed detected methane's chemical signature.
"The first thing to understand is how exactly the methane is distributed in the Martian atmosphere," Formasino said. "Based on our experience on Earth, the methane production could be linked to volcanic or hydrothermal activity (sub-surface hot springs) on Mars."
But Formasino added cautiously: "If we have to exclude the volcanic hypothesis, we could still consider the possibility of life."
The first tentative detection of methane in the Martian atmosphere was announced last year by Michael Mumma, a physicist at NASA's Goddard Space Flight Center near Washington, D.C. He found the telltale evidence in observations by ground-based telescopes at Cerro Pachon in Chile and the giant Keck II instrument on Mauna Kea in Hawaii.
Vladimir Krasnopolsky of the Catholic University of America in Washington, D.C., reported Monday that he and his colleagues had also found evidence of Martian methane using the Canada-France-Hawaii telescope atop Mauna Kea. | 0.893419 | 3.720442 |
Luis Argerich / Flickr
Even after nearly 20 years as an astronomer, I still believe the Perseid meteor shower in mid-August is one of the most spectacular astronomical events I have seen. If you are at all impressed by the majestic nature of the universe, you will not want to miss these Perseids, which usually peak around August 12. Beyond their aesthetic display, their very existence gives us a real connection to the solar system, its past formation, and thereby to the star and planet formation history of our entire galaxy.
Many people have some idea that a meteor shower is when material in space falls to the earth. That is essentially true, but what these particles are and where they come from isn’t as well known. A greater understanding of their background makes viewing this show of nature even more rewarding.
The bright streams of light coming from these meteors as they fall to the ground makes for spectacular viewing. We are essentially watching the burning up of tiny rocks that were in interplanetary space, and just happen to fall into the Earth’s orbit. When this rock falls into the Earth’s atmosphere the friction from molecules in the atmosphere create such intense heat that the rock begins to disintegrate. This occurs when the Earth’s orbit intersects with the pockets of debris within the solar system that were originally part of a comet.
The Perseid meteor shower has been known about for hundreds of years, but was only identified as a specific, recurring event in the early 19th century. The comet that produces the Perseids is known as Swift-Tuttle, named for the two American astronomers who discovered it in 1862.
This was long after the Perseids themselves were observed, and it took several decades for astronomers to make the connection between the comet and the meteor shower. Eventually, they noticed the orbit of the comet was similar to that of the dust debris that produces the meteor shower. Swift-Tuttle was last seen from Earth using telescopes in 1992, and will be observable again in 109 years. It is also one of the most likely comets to hit the earth, although this would not happen for several hundred years.
It’s fascinating to realise that the meteor streaks we see across the sky once came from this comet. Swift-Tuttle has a 133-year orbit in the solar system, which takes it 51 times further from the sun than the Earth. This means the comet originates from the outer solar system in the so-called Oort cloud beyond the orbit of the planet Neptune. This comet then comes into the inner solar system where it interacts with more massive objects. During these legs of its journey, we can view it with our telescopes.
Glimpse at the past
While this is happening, the comet interacts with the gravity of the Sun and other planets, which causes it to lose some of the rock and dust it is made up of. This stream of material left behind continues to orbit the sun in a path that intersects with the Earth’s orbit. So the steaks of light we see from burning debris during a meteor shower are the leftover material from a comet that originated in the outer parts of our solar system. We are essentially seeing a remnant of the early formation of the sun and our planets and also the destruction of material that was formed 5 billion years ago, as old as the oldest rocks on Earth.
The reason these particular meteors are called Perseids is that if you take the radiant – that is, the line from which these meteors can be traced from their origin – the constellation they appear to come from is Perseus. So the best place to see the Perseids is where the constellation can be seen, which luckily is throughout the night for most places in the northern hemisphere.
Observing the Perseids this year should be fairly straightforward. As with any astronomical event at night, the best place to view these Perseids is in a dark location away from any artificial light and with an unobstructed view of the sky. The 2016 show is expected to peak with 150 meteors an hour – more than two a minute – better than previous years. And with a quarter-moon making the night sky darker than in previous years they will be even more visible. | 0.903357 | 3.968256 |
Albert Einstein’s general theory of relativity has passed a multitude of tests over the past century, but physicists remain unsatisfied. That’s because it has never been matched up against a strong gravitational field, like that of a supermassive black hole. Now, a team monitoring a star on its way to a close encounter with the giant black hole at the center of our galaxy says early signs hint that the 102-year-old theory will once again hold up.
Observing stars close to the black hole known as Sagittarius A* (Sgr A*) is extremely difficult because it is 26,000 light-years from Earth and shrouded in a cloud of gas and dust. Astronomers have to use big telescopes that are capable of collecting infrared light, which can penetrate the murk. But over the past few decades, researchers have tracked the paths of a handful of stars as they race around Sgr A* at high speed. From those paths, they can deduce not only the existence of the supermassive black hole, but also its mass: four million times that of the sun.
Those studies did not invoke general relativity because in most situations it only differs from Newton’s theory of gravity in subtle ways. To put Einstein to the test requires tracking orbits with extreme precision to tease out those minute differences. The closest known star to Sgr A*, dubbed S2, is the most likely to show signs because it gets so near. Every 16 years, its highly elliptical orbit takes it in close to the black hole—about four times the distance between the sun and Neptune. During its last close encounter, in 2002, astronomers didn’t have the instruments to measure it accurately enough. But they’re ready for the next pass in mid-2018.
In the run-up to the big event, astronomer Andreas Eckart of the University of Cologne in Germany and his team sought to map out the orbit of S2 as accurately as possible with data gathered over more than 2 decades using the European Southern Observatory’s Very Large Telescope (VLT) in Chile and observations made by other groups. It was “tedious work,” says Eckart, but their efforts show that S2 is already deviating from a Newtonian orbit, and the values are “extremely close to the expected values” predicted by general relativity.
Newton predicted that a star should follow the same elliptical orbit through space over and over again. But according to relativity, when the star swings in close to the black hole, it overshoots slightly, shifting the center line of the orbit by a tiny amount. This also means that the orbit is a slightly different shape at closest approach compared to its path farthest from Sgr A*. In a paper published today in the Astrophysical Journal, the team reports seeing both signs—a shifting center line and different orbit shapes—in its observations of S2.
Theoretical physicist Abraham Loeb of Harvard University is not convinced this is enough to claim agreement with relativity because the study’s error bars are so large. But he’s optimistic that they are on the right track. “The silver lining is that more precise measurements could measure the expected correction in the future.”
As S2 approaches Sgr A*, Eckart’s team is preparing to use a new instrument called GRAVITY that will combine signals received by two of the four 8.2-meter telescopes that make up the VLT to produce images with a resolution equivalent to that of a mirror 120 meters across—the distance between the two telescopes. This will achieve a “much higher precision,” Eckart says, perhaps enabling them to nail general relativity once and for all.
*Correction, 5 September 6:36 p.m.: An earlier version of this story referred to Albert Einstein’s theory as the “theory of general relativity;” it should be the “general theory of relativity.” | 0.844145 | 4.096717 |
Washington: NASA’s New Horizons spacecraft, which successfully made a historic flyby of Pluto, has discovered young ice mountains on the dwarf planet which are as high as 11,000 feet and about 100 million years old.
New close-up images of a region near Pluto’s equator show a range of youthful mountains rising as high as 11,000 feet (3,500 meters) above the surface of the icy body, NASA said.
The mountains likely formed no more than 100 million years ago – mere youngsters relative to the 4.56-billion-year age of the solar system – and may still be in the process of building, said Geology, Geophysics and Imaging (GGI) team leader Jeff Moore of NASA’s Ames Research Centre in California.
That suggests the close-up region, which covers less than one per cent of Pluto’s surface, may still be geologically active today, researchers said.
Moore and his colleagues base the youthful age estimate on the lack of craters in this scene.
Like the rest of Pluto, this region would presumably have been pummelled by space debris for billions of years and would have once been heavily cratered – unless recent activity had given the region a face-lift, erasing those pockmarks.
“This is one of the youngest surfaces we’ve ever seen in the solar system,” said Moore.
Unlike the icy moons of giant planets, Pluto cannot be heated by gravitational interactions with a much larger planetary body. Some other process must be generating the mountainous landscape.
“This may cause us to rethink what powers geological activity on many other icy worlds,” said GGI deputy team leader John Spencer of the Southwest Research Institute in Boulder, Colorado.
The mountains are probably composed of Pluto’s water-ice “bedrock.”
Although methane and nitrogen ice covers much of the surface of Pluto, these materials are not strong enough to build the mountains. Instead, a stiffer material, most likely water-ice, created the peaks.
“At Pluto’s temperatures, water-ice behaves more like rock,” said deputy GGI lead Bill McKinnon of Washington University, St Louis.
The close-up image was taken about 1.5 hours before New Horizons closest approach to Pluto, when the craft was 77,000 kilometres from the surface of the dwarf planet.
Wajid Khan of music composer duo Sajid-Wajid dies at 42
Arjun joins Dua Lipa, Jason Derulo to raise COVID-19 relief funds
Actor Kiran Kumar tests negative for COVID-19
Animation series on Salman Khan’s ‘Dabangg’ in the works
Salma Hayek says daughter Valentina may follow in her acting footsteps
© 2020 State Times Daily Newspaper | 0.881351 | 3.635428 |
Mars’s magnetic field weakened and disappeared billions of years ago. Now, scientists have found that the weak field might have been worse than none at all.
Early Mars boasted an Earth-like magnetic field that shielded it from solar radiation and helped the planet hold onto its atmosphere. But as the Martian crust cooled, its magnetic field weakened. Now, new research reveals that this scrawny magnetic field may have been worse than no field at all.
How the planetary magnetic field helped Mars hold onto its atmosphere has been a longstanding question, and one that’s difficult to study today. The Sun was brighter in the solar system’s early years, dousing the planets with stronger radiation than today. Mars also produced a stronger magnetic field back then than the patchwork quilt it’s left with now. To study the escaping atmosphere under conditions drastically different from today, scientists turned to simulations.
"The relative effects have been controversial," says Kanako Seki (University of Tokyo), coauthor of the study published in the Journal of Geophysical Research: Space Physics. A global magnetic field can serve as both a blessing and a curse. It should act as a shield, blocking most interactions between a planet’s atmosphere and solar radiation. But some studies have shown that weak magnetic fields actually increase the loss of charged particles.
With simulations, Seki, study lead Ryoya Sakata (also at University of Tokyo), and their colleagues show that a planet with a weak magnetic field would lose ionized oxygen and carbon dioxide from its atmosphere 100 times faster than one with a strong field — and six times faster than a planet with no magnetic protection at all.
Weak Fields, Thin Air
Mars’s magnetic field was active in its youth, pushing back against the solar wind pressure created by charged particles streaming from the Sun. But as the field weakened, its pressure decreased, giving the solar wind easier access to the atmosphere.
The magnetized wind snaps the lines of the planet’s magnetic field, blowing them backward in the northern dusk or southern dawn regions. The dents in the magnetic field at these locations, called cusps, are the points of escape, where the magnetic field lines recently snapped or merged. "In cusps, the solar wind can easily penetrate and planetary ionized atmosphere can escape along the open field lines," Seki says. "The formation of the cusp can increase the atmospheric escape."
According to the simulations, the cusps become more prominent in the case of a weak magnetic field. Then, when the magnetic field fades altogether, there are no cusps at all, slowing the escape of charged hydrogen and oxygen.
Catherine Johnson (Planetary Science Institute), who was not involved in the study, points out that, according to the new research the transition between protecting the atmosphere and aiding escape occurs when the magnetic field is about 10 times weaker than present-day Earth's field. "Most studies of Mars's field have concluded that the ancient field was at least as strong as Earth’s," Johnson says.
However, the new study focuses only on how a magnetic field interacts with the charged part of the atmosphere, and previous studies have concluded that ion escape contributes only a minor role in removing the atmosphere today. Its role in the past, when the Sun burned stronger and brighter, is still debated.
"At least part of the disagreement comes from uncertainty over what both the atmosphere and the Sun were like in early solar system history," says David Brain (University of Colorado, Boulder), a member of the MAVEN mission. "Which processes dominated is uncertain."
Nevertheless, the researchers argue that the increase in the amount of atmosphere that escapes from a weak magnetic field compared to a strong one is significant enough to make a difference. "Two orders of magnitude variation in ion loss rates has a critical impact on atmospheric escape,” they write.
From Mars to Exoplanets
According Brain, the new simulations address two important issues at once: how much atmosphere escaped from ancient Mars and how the magnetic field influences that escape rate. While previous studies have touched on these concerns individually, none have addressed them in combination.
"This is the first [theoretical study] that addresses both questions simultaneously, and therefore provides an important benchmark for comparison with future studies," Brain says.
Understanding the role of the Martian magnetic field affects our understanding of exoplanet habitability as well. While Mars is small enough and has low enough gravity that other processes may dominate the process of atmospheric loss, Brain says that for larger, Earth-size worlds, "ion escape is the only game in town."
"The work presented here is important in a larger sense,” Brain says, “because it hints at the importance of magnetic fields for all planets—including ones where ion escape is the only viable escape process.” | 0.825849 | 4.091265 |
A brief debate broke out over the radio on Jan. 25, 2013. “Anyone in drill camp know who’s in the Super Bowl?” someone asked.
“49ers and Seahawks,” replied a female voice.
“No—49ers and Falcons,” argued a male voice on the radio. They were both wrong. The 49ers and Ravens had earned their spots in the Super Bowl five days before. But these people could be forgiven their ignorance. They were living in near-complete isolation from the outside world: 30 people, including myself, inhabiting a small constellation of tents in the middle of the West Antarctic Ice Sheet.
It was hard even to be sure of the date. Our camp sat just 380 miles from the South Pole—and there, at the height of the Antarctic summer, the sun never set. The roar of two 225,000-watt generators burning jet fuel reverberated through camp day and night—not for our comfort, but rather to power a hot-water drill. This behemoth occupied nearly a dozen cargo containers mounted on skis. It melted thousands of gallons of snow and pumped the heated water into a hose more than three-quarters of a mile long. People worked round the clock to unspool that hose, slowly, into a hole in the ice. The jet of hot water gushing from its nozzle melted the hole deeper and deeper—ever closer to the bottom of the ice sheet. The ice drillers constantly chatted on handheld radios to coordinate their opening and closing of water valves.
I followed this team of researchers and equipment operators down to Antarctica to witness a historic event: the first time that a subglacial lake, a huge pocket of liquid water hidden for millennia beneath Antarctica’s thick glacial ice, had ever been drilled and sampled.
There were many reasons for drilling into Lake Whillans, buried beneath half a mile of ice for up to 120,000 years. One of them is to understand what kind of life, if any, might survive outside of Earth, in the icy outer reaches of our solar system.
If you read or write often about Antarctica, as I do, you frequently hear that one project or another will help us understand the possibility of extraterrestrial life. I often find such claims a bit trite—not dishonest, but based on a superficial analogy: Antarctica is cold, and so are most other planets and moons in our solar system. This alone, in my view, does not make Antarctica relevant for astrobiology. But the work on Lake Whillans and other subglacial lakes is providing some deep insight into why and how life might exist elsewhere in our solar system—especially on Europa, a moon orbiting Jupiter, which holds an ocean of liquid water beneath a crust of ice 10 to 20 miles thick.
* * *
The drill finally broke into Lake Whillans on Jan. 27, 2013. Bottles of its mineral-rich, honey-colored water were raised a day later. And soon after, a plastic cylinder was hoisted up, holding a column of mud punched from the lake’s bottom—ancient sediments representing the long-hidden bedrock face of Antarctica.
Dark glops of this alien mud spattered on the snow by the drill rig, smooth and gleaming like chocolate gelato. It was surprisingly scratchy, like wet cement, when rubbed between the fingers—full of tiny shards of bedrock pulverized by sliding glaciers during many thousands of years.
Mud is mundane—so easily overlooked—but to see it there was truly stirring. The West Antarctic Ice Sheet covers an area four times that of Texas—a plain of white in which each place looks like any other. I have spent seven weeks there during two expeditions, in 2007 and 2013. The horizon was usually identical and flat in every direction. No rock, no sand, not a speck of dirt—not a single vestige of the natural world that most of us live our daily lives in.
So when people saw that mud, they did pretty much what you’d expect: They scooped it off the snow and painted lines on their faces with it.
Experiments performed back home in the U.S. would reveal that Lake Whillans was brimming with life, half a million cells in every teaspoon of water—similar to the abundance of microbes in much of the world’s oceans. It was another example of the still-astonishing capacity of life to persist in just about every niche ever explored on Earth, from 230 degrees Fahrenheit volcanic vents on the ocean floor to deep ice in Greenland as cold as minus 30 degrees Fahrenheit to the stratosphere at altitudes up to 60,000 feet. It would be a bigger discovery if no life was found at all, said Brent Christner, one of the lead biologists on the project, from Louisiana State University, in the weeks before the lake was drilled.
What’s astounding was just how hospitable Lake Whillans turned out to be.
It was easy to imagine the lake as profoundly hostile to life—cold, isolated from sunlight, and cut off the oxygen-rich atmosphere for possibly as much as 120,000 years. But it didn’t turn out to be so bad. Its water, at 31 F, was a tad warmer than the coastal seas surrounding Antarctica—waters that teem with krill, starfish, and whales—not to mention toothfish, weighing up to 100 pounds, which are commercially fished and served in restaurants around the world. (Salt and high pressure lower the freezing point of water, allowing it to stay liquid in oceans and deeply buried subglacial lakes several degrees below the traditional freezing point of 32 F.)
Most intriguing of all, the water in Lake Whillans actually contained oxygen—enough, theoretically, to support some common marine animals, like sea stars, sponges, and worms. These animals weren’t found in the lake, but it’s possible some small, rudimentary animals might inhabit its mud.
Although the lake sits under half a mile of ice, oxygen is constantly pumped into it from above. Ambient heat seeping up from the Earth’s interior melts a few penny-thicknesses of water from the underside of the ice sheet every year—liberating tiny air bubbles that were trapped when that ice formed from snow falling on the surface of the continent.
This downward conveyor belt of oxygen isn’t unique to Lake Whillans. Members of a Russian team found something similar when they drilled into subglacial Lake Vostok, locked beneath 2½ miles of ice in another part of Antarctica. When the Russians’ drill penetrated the lake, a pressurized froth of water and gas bubbles surged hundreds of feet into the borehole—so powerful that it forced up 100,000 pounds of kerosene drilling fluid in the hole above it.
Lake Vostok had popped its cork like a freshly opened bottle of Champagne. Those bubbles provided evidence that the lake might be pressurized with up to 50 times more oxygen, gallon for gallon, than the world’s oceans—despite being isolated from the atmosphere for 15 million years. The search for life in Lake Vostok remains in progress, with researchers still uncertain whether microbes detected in its water originated from the lake or from the drilling fluid.
Roughly half of Antarctica’s 5 million square miles of glacial ice may sit on a bed of liquid water and mud—“the largest swamp in the world,” as it’s called by Slawek Tulaczyk, a glaciologist from the University of California–Santa Cruz who co-led the Lake Whillans drilling project. Much of that subglacial swamp may contain oxygen.
It is the discovery of oxygen beneath the ice that transforms Antarctica’s subglacial lakes into a compelling analogy for how life might exist inside distant icy moons.
* * *
Six moons in our outer solar system are likely to have oceans of liquid water beneath an icy crust: Europa, Callisto, and Ganymede, which orbit Jupiter; Enceladus and Titan, which orbit Saturn; and Triton, which orbits Neptune. Together, they hold roughly 20 times as much liquid water as all of the rivers, oceans, and lakes on Earth. These moons are substantially smaller than Earth but contain a far higher percentage of water than Earth does.
It is often said that life requires liquid water. But with water now seeming pretty abundant in our solar system, the more stringent requirement for life may well be something else: an energy source that can power the growth of cells. This is where the finding of oxygen in Lake Whillans becomes important.
Most life on Earth subsists on energy from the sun: Photosynthetic plants and microbes use solar energy to split molecules of carbon dioxide into oxygen and carbon. Most other life on Earth piggy-backs on this solar energy scheme by running these chemical reactions in reverse. They use oxygen or some other reactive compound to “burn” carbon or other minerals and release energy.
Life subsisting beneath 10 to 20 miles of ice on Europa has no direct access to that energy—and neither does life in Lake Whillans. This subglacial lake shows how the flow of energy might still sustain life sealed under thick crusts of ice.
* * *
The temperature on Europa’s surface hovers between minus 260 F and minus 370 F—vastly colder than the lowest temperature ever recorded on Earth (minus 128.6 F, recorded at the Russians’ Vostok Station in Antarctica in 1983). It receives only about 4 percent as much sunlight per square foot as Earth does. It has no atmosphere to speak of. And yet somehow, Europa captures oxygen and other reactive compounds on its surface.
Earth-based telescopes and NASA’s Galileo space probe (which first flew by in 1997) have repeatedly detected signatures of oxygen on Europa’s surface, as well as sulfate and sulfur dioxide—two other reactive compounds that some microbes on Earth can use in place of oxygen. This supply of potentially life-giving oxidants comes from a bizarre interplay between Jupiter and its moons.
Europa’s orbit around Jupiter just happens to place it beside the most volcanically active object in the solar system: a yellow-white-orange sphere called Io, pimpled with several hundred volcanoes that spew sulfur dioxide and other gases into space. Its volcanic residue filters down onto Europa. There, it is cooked by radiation from Jupiter—producing the oxygen, sulfate, and other reactive chemicals seen on Europa’s surface. All told, Europa has gathered 60 million tons of sulfur from Io during its lifetime.
Magnetic and gravity measurements from Galileo suggest that Europa’s ocean sits on a rocky, Earth-like bottom. This solid, potentially mineral-rich base could supply the other half of the energy equation—iron or sulfur minerals that microbes could use as food. Just as microbes in Lake Whillans use oxygen from the ice above to burn iron, sulfur, and ammonia in the lake’s mud, alien life on Europa might use oxygen, sulfur dioxide, or sulfate to burn minerals on its own sea floor. The same broad formula for powering life applies to either place: Reactive, oxidizing chemicals derived from sunlight or radiation come from the ice above—and food to be burned by those chemicals comes from the rocks and mud below.
The potential hiccup is that Europa’s ice is 20 to 40 times thicker than that covering Lake Whillans—but even this might not prevent reactive chemicals from reaching the ocean below.
High-resolution images captured by Galileo show that Europa’s smooth surface is dotted with jumbled patches where blocks of ice seem to have tilted sideways. Planetary scientists now think that Europa’s ice shell is slowly churning and recycling itself. This is driven by warm ocean currents beneath the ice—and those currents are powered by intense tides and frictional heating as Europa’s interior strains and flexes under the force of Jupiter’s gravity. “Thermal forcing from the interior is high enough that it’s really affecting the ice,” says Britney Schmidt, a planetary scientist at Georgia Tech. “We may really be looking at quite a lot of heat.”
Schmidt calculates that these tumbled patches of ice probably overlie pockets of liquid water trapped in the shifting ice. Some of these pockets are quite big: One, beneath an area of chopped-up terrain named Thera Macula, is thought to hold more water than all of the Great Lakes combined.
This overturning of Europa’s ice could pump oxygen, sulfate, and sulfur dioxide into its ocean. “It actually ends up being relatively easy to oxidize Europa’s ocean,” says Kevin Hand, an astrobiologist at the NASA Jet Propulsion Laboratory—“even to the point where you’ve got enough oxygen to support complex life.”
These tossed-up blocks of Europan ice could also provide a compelling target for planetary exploration, since some of those Great Lake–sized pockets of water may sit only 2 miles beneath the ice surface.
Sending a space probe to drill through 20 miles of ice into Europa’s ocean represents a near-impossible task—but drilling through only 2 miles is much more doable. Researchers working in Antarctica and Greenland are already gaining expertise drilling through that thickness.
The Europa Clipper space probe now being considered for funding by NASA could set the stage for drilling into Europa’s hidden water by scouting out possible landing sites. Ice-penetrating radar on the probe could locate pockets of water near the surface that might become targets for future drilling missions. A magnetometer could estimate the depth—and even the saltiness—of the hidden ocean. An infrared spectrometer could make improved measurements of reactive chemicals like oxygen or sulfate on the surface. A mass spectrometer might even allow the probe to analyze water from Europa’s ocean: Plumes of water vapor sometimes seen around the moon are thought to come from ocean water forced up, in brief spurts, by the shifting of ice blocks.
If Europa Clipper is funded, it could launch sometime after 2020. Antarctica, meanwhile, will serve as a proving ground for developing tools needed to explore Europa and the other icy moons of our solar system. | 0.853437 | 3.284532 |
Japanese space scientists shot an asteroid to learn about its past
The tiny, rocky asteroid Ryugu, in orbit between Earth and Mars, gives up some of its secrets.
The unmanned Hayabusa2 spacecraft, launched by Japan's Aerospace Exploration Agency (JAXA), in 2014, made its rendezvous with the one kilometre in diameter near-Earth Asteroid Ryugu almost two years ago.
As part of its mission it fired a two kilogram copper cannonball into the asteroid's surface from very close range. The resulting artificial crater displaced about "10,000 buckets of sand," according to Seiji Sugita.
Sugita is a principal investigator with the Hayabusa2 mission, and professor in the Department of Earth and Planetary Science at the University of Tokyo.
Ryugu's age and composition
Making the crater gave researchers the opportunity to learn more about the asteroid's age and composition. The crater was semicircular in shape and measured just over 17 metres across at its widest point. Previous observations revealed that Ryugu was composed of sand and boulders. The impact revealed that the material wasn't well consolidated, or bound together,
Results from examination of the crater, and other naturally created craters on Ryugu, suggest that Ryugu may only be about 10 million years old.
Hayabusa's return to Earth
The Hayabusa2 spacecraft will return to Earth in December of this year. Scientists like Sugita are especially excited about that because of its special cargo. Earlier in its mission Hayabusa2 had touched down on the asteroid and scooped a small sample of its surface.
- Research paper in Science
When the spacecraft launched the projectile into the surface, special equipment on board also collected a tiny amount of material — or ejecta — from the plume created by the impact. Combined, these samples will will provide more definitive information about asteroid Ryugu. | 0.803525 | 3.424214 |
Craters by radiation/Laboratory
Some suggested types of cratering to consider include a lightning strike, a bullet shot into some material, a water droplet hitting the surface of a beaker of water, a subterranean explosion, a sand vortex, or a meteorite impact.
More importantly, there is your cratering idea. And, yes, you can crater a peanut butter and jelly sandwich if you wish to.
Okay, this is an astronomy cratering laboratory, but you may create what a crater is. Another example is a volcanic crater.
I will provide an example of a cratering experiment. The rest is up to you.
Questions, if any, are best placed on the discussion page.
For my cratering laboratory example, I will compose a control group. You will need at least one too.
Control group (circle):
- As a first approximation, a crater in the horizontal plane of a rocky-object's surface is a circle for an object dropping, or falling vertically, or for rocky matter ejected vertically.
- The lower the angle of impact, falling, or ejection, from vertical (90°), the more elongated and ellipsoidal the crater is in the direction of impact, fall, or ejection.
From crater astronomy, the sources of a circular crater are many:
- a volcanic bomb falling nearly vertically from above,
- a rocky meteor falling vertically from above,
- a volcanic eruption from an approximate point source below the center of the circle,
- an ejection from an electric arc above the ground arcing at the center of the circle,
- an explosion above or below the center of the circle, like a volcano,
- a subsidence or falling below the center of the circle into the ground below, or
- a lightning strike directly from above leaves a circle and a hole where missing rocky matter either melted into less volume or was ejected like other explosions.
- angularity away from a circle, when symmetric about the center is likely due to the structure of the rocky surface and beneath it.
To assess your cratering experiment, include your justification, analysis and discussion. I will provide such an assessment of my example.
The Nastapoka arc is a geological feature located on the southeastern shore of Hudson Bay, Canada.
It is a near-perfect circular arc, covering more than 160° of a 450 km diameter circle.
"C. S. Beals (1968) suggested that the Hudson Bay arc is the remnant rim of a giant impact crater nearly 300 miles across, or comparable to Mare Crisium in size."
"Although extensive clean rock exposures abound, no shatter coning was observed."
"[S]uevite-type or other unusual melt rocks, pseudotachylite or mylonite, radial faults or fractures, unusual injection breccias, and other possible shock metamorphic effects [were searched for, but] [n]one was found."
Deitz' "negative results, however, probably do not disprove an impact origin for the arc, as even shatter coning, which is the lowest level shock indicator, still requires over-pressures from 20 to 50 kbars."
"[A]n Archean impact might be forever buried beneath the Proterozoic sedimentary cover which filled the entire basin inside the postulated rim."
From the high degree of circularity of the Nastapoka arc for more than 160°, the area of Hudson Bay where the arc occurs is part of a crater. But, what happened to the western 55 % of the crater? And, of course, what is the origin of the crater?
Looking at the image above right, where Quebec is in red, there are the Belcher Islands, also in the image at lower left, almost within a chord connecting the two ends of the arc. Putting a circle holometer over the arc shows that the center of the circle is slightly north-north west of the Belcher Islands and does not touch them.
With respect to the paleoproterozoic orogens, all of the arc just beyond the chord connecting the upper and lower latitude tips of the arc is considered part of the continental margin for the Trans-Hudson orogen to the west.
The bay just north of that which is the bay of the Nastapoka arc is less circular and only about 90° of a circle. Up the same coast, the third inlet is also circular and about 80°.
The rock layers composing the Belcher Islands are not horizontal but may be dipping near vertically. If a cratering event occurred after the rock beds were tilted nearly on edge, the damage to the rock strata may have been more absorbed with less actual crater depth.
As at least half of each circle on the western half is missing, it may be that the craters are dipping downward to the west. The amount of dip is likely less than 10° so as to keep the craters from being ellipsoidal.
Craters initially circles dipping to the west result in a horizontal shortening of the W-E axis, while the N-S axis remains unchanged. The mountains of the eastern rim of the crater appear to decrease in relative elevation trending northward or southward around the arc from almost due east.
The more likely possibility is that the western halves have fallen or been depressed into the Earth approximately vertically. This would have the effect of maintaining circularity while causing a loss of the western half of each crater.
The origin of the residual craters is concluded to be subsidence of the rocky surface, perhaps under the weight of glacial ice.
An origin for the craters themselves is considered as unknown due to a lack of evidence associated with causes.
- Many of the craters traditionally assigned to impact craters may be electric arc or discharge craters.
- Robert S. Dietz and J. Paul Barringer (1973). "Hudson Bay Arc as an Astrobleme: a Negative Search". Meteoritics 8: 28-9. http://adsabs.harvard.edu/full/1973Metic...8...28D. Retrieved 2013-12-29.
- David W. Eaton, Fiona Darbyshire (January 5, 2010). "Lithospheric architecture and tectonic evolution of the Hudson Bay region". Tectonophysics 480 (1-4): 1-22. http://www.sciencedirect.com/science/article/pii/S0040195109005034. Retrieved 2013-12-30.
- David W. Eaton, Fiona Darbyshire (January 5, 2010). "Lithospheric architecture and tectonic evolution of the Hudson Bay region". Tectonophysics 480 (1-4): 1-22. http://www.sciencedirect.com/science/article/pii/S0040195109005034. Retrieved 2013-12-30. there is a pdf available.
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An international team of astronomers has produced the first ever picture of a supernova using gamma rays. The picture provides evidence that supernovae are one source of cosmic rays, highly energetic particles that bombard the planet, passing through us in their thousands every day.
Making an image using gamma radiation is very difficult because it is so penetrating - i.e. it passes through nearly everything. However, in this case astronomers have used Cherenkov radiation, flashes of blue light that last mere billionths of a second, to make the image.
Cherenkov radiation is caused by a charged particle exceeding the speed of light in the medium through which it travels - in this case by gamma rays interacting with the atmosphere. That doesn't mean the absolute speed of light has been exceeded, just that the gamma rays are moving so fast that they are going faster then the speed of light in the atmosphere.
Dr Paula Chadwick of the University of Durham said: "This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night."
The picture was taken using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa. The UK's involvement is funded by the Particle Physics and Astronomy Research Council, PPARC.
PPARC's Professor Ian Halliday commented: "These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays - something we have long suspected, but never been able to confirm." ® | 0.848363 | 3.549777 |
Heading toward its first target-asteroid, (2867) Steins, ESA's Rosetta spacecraft has started using its cameras to visually track the asteroid and eventually determine its orbit with more accuracy.
Rosetta started the optical navigation campaign on 4 August 2008, at a distance of about 24 million km from Steins; the campaign will continue until 4 September, when the spacecraft will be approximately 950 000 km from the asteroid.
"The orbit of Steins, with which Rosetta will rendezvous on 5 September, closing to a distance of 800 km, is only known thanks to ground observations, but not yet with the accuracy we would like for the close fly-by," said Gerhard Schwehm, Rosetta Mission Manager based at ESA's European Space Astronomy Centre (ESAC), near Madrid, Spain.
Optical tracking to better understand Steins' orbit
We will be able to use the first data set for the trajectory correction manoeuvre planned for mid-August.
The purpose of the tracking campaign is to reduce the error in our knowledge of Steins' orbit from about 100 km to only within 2 km (in the direction perpendicular to the flight direction of the asteroid, called 'cross-track'), so as to allow Rosetta an optimal approach to this celestial body.
Both Rosetta's navigation cameras and the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) imaging system will be used to track Steins.
"For the first three weeks of the campaign, however, only the powerful eyes of OSIRIS will actually be able to spot the asteroid, which will look only like a dot in the sky," said Andrea Accomazzo, Rosetta Spacecraft Operations Manager at ESA's European Space Operations Centre (ESOC), Darmstadt, Germany.
"Starting 11 days before closest approach, as the distance with Steins decreases, the two Rosetta navigation cameras will finally be able to see and track the asteroid, too," he added.
For the first three weeks of the campaign, Rosetta will image Steins twice a week and then, starting on 25 August, it will take images daily until 4 September.
The Steins orbital information gathered during the tracking campaign will be used to adjust Rosetta's trajectory for the 5 September fly-by. "We will already be able to use the first data set for the trajectory correction manoeuvre planned for mid-August," said Sylvain Lodiot, from the Rosetta Flight Control Team at ESOC.
"As Rosetta's distance from Steins decreases, the precision of the measurements for Steins' orbit will increase even further, allowing us the best possible trajectory corrections later on before closest approach, especially in early September."
OSIRIS to obtain Steins' 'light curves'
Rita Schulz, Rosetta Project Scientist based at ESA's European Space Research and Technology Centre (ESTEC), Noordwijk, the Netherlands, explained that this is the first time in the Rosetta mission that the OSIRIS scientific instrument is being used for tracking purposes.
"But OSIRIS will also take this opportunity to obtain 'light curves' of Steins. Light curves tell us how the asteroid brightness varies with time, providing us with additional preparatory information about the asteroid, such as better knowledge of its shape and rotation characteristics," she said.
The optical navigation campaign follows a series of active check-outs of Rosetta's scientific instrumentation, which lasted from 5 July to 3 August this year. A mission milestone for Rosetta, these activities also verified the instruments' readiness for the fly-by observations, and allowed on-board software modifications to be implemented for several of them.
Gerhard Schwehm, ESA Rosetta Mission Manager
Email: Gerhard.Schwehm @ esa.int
Rita Schulz, ESA Rosetta Project Scientist
Email: Rita.Schulz @ esa.int
Andrea Accomazzo, ESA Rosetta Spacecraft Operations Manager
Email: Andrea.Accomazzo @ esa.int | 0.836614 | 3.455976 |
The field of particle astrophysics is at the forefront of research in both high-energy particle physics and astronomy. In The University of Alabama particle astrophysics group, we use fundamental particles to explore some of the most extreme objects in the universe, and use astronomical signals to explore physics beyond the Standard Model.
IceCube Neutrino Observatory
IceCube is the largest neutrino detector on Earth. Located at the geographic South Pole, IceCube consists of strings of photomultiplier tubes deployed between 1500 and 2500 meters deep in the Antarctic icecap. Construction of the IceCube detector was complete as of January 2011, with 86 strings instrumenting a cubic kilometer of ice. IceCube was built to detect astrophysical neutrinos at TeV-PeV energies from objects such as active galactic nuclei and gamma ray bursts, which are believed to be the source of the highest-energy cosmic rays.IceCube also searches for neutrinos from the annihilation of dark matter and explores fundamental aspects of neutrino physics with neutrinos produced by cosmic rays interacting in our atmosphere.
The group of Dr. Dawn Williams is developing techniques to identify tau neutrinos in IceCube data. The Alabama IceCube group is also responsible for calibration of the detector with muons and LED flashers.
VERITAS Gamma Ray Observatory
VERITAS (Very Energetic Radiation Imaging Telescope Array System) is a ground-based gamma-ray instrument operating at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona, USA. It is an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. These imaging Cherenkov telescopes are deployed such that they have the highest sensitivity in the VHE energy band (50 GeV – 50 TeV), with maximum sensitivity from 100 GeV to 10 TeV. This VHE observatory effectively complements the NASA Fermi mission. Objects that emit gamma-rays are very interesting to astrophysicists. High-energy gamma rays are associated with exploding stars (supernovae), pulsars , quasars , and black holes rather than with ordinary stars or galaxies.
Dr. Marcos Santander is interested in high-energy neutrino astrophysics and multi-messenger searches for neutrino sources using gamma-ray and X-ray telescopes.
Professor Nobuchika Okada’s research interests are centered on phenomenological aspects of particle physics, in particular, new physics beyond the Standard Model. It has been clear in recent years that an extension of the Standard Model, i.e. new physics beyond the Standard Model, is needed to explain a number of experimental observations such as dark matter. In addition, the Standard Model suffers from several theoretical problems. These problems are expected to be solved by a certain new physics which is realized most likely at the TeV scale.
The main theme of Dr. Okada’s research is to reveal new physics beyond the Standard Model from the theoretical point of view, based on the experimental results. Along this direction, Dr. Okada has been working on various topics of particle physics phenomenology such as new physics model buildings, supersymmetry, extra-dimensional models, grand unified theory, neutrino physics, high energy collider physics, particle cosmology, and astroparticle physics. For a publication list see here. | 0.828028 | 3.850394 |
Big or small, black holes play same melody
(CNN) -- Massive black holes that dwell in distant galactic centers and diminutive counterparts that reside in nearby star systems have one startling likeness: they play the same energetic song, albeit at different tempos.
British astronomers came to that conclusion after tuning into the X-ray emissions of numerous black holes. They compared the slow variations in emissions from the larger ones with the much more rapid radiation outputs from the smaller siblings.
The former can be as much as a billion times heavier than the sun, feeding on an unstable diet of galactic gas. As matter approaches a central black hole, it compresses and releases fluctuating bursts of energy, including X-rays. Radiation emission variations can last hours or years.
In contrast, much smaller black holes feed off companion star material. Their energy release variations are measured in milliseconds or seconds.
But slow down the variation patterns of the little guys, for example, by a factor of 1 million, and they have an uncanny resemblance to those of the big boys, according to University of Southampton researchers.
"If you were to transcribe the X-ray output of these black holes as a series of musical notes, so greater X-ray output means a higher pitch, it would not sound quite like any particular sort of music, because the variations in X-ray output are essentially random," said astronomer Phil Uttley.
"But the 'tune' will still have a musical quality about it. This is because the general pattern of note changes is the same as you hear in all kinds of music," he said "You could say that these black holes are the ultimate improv artists!"
Uttley and colleagues used NASA's Rossi X-ray Timing Explorer satellite to monitor central galaxy black holes for six years.
That black holes emit variations of the same theme could serve as a valuable tool for astronomy.
"The tape speed setting is the only major difference, and it's governed by the black hole's mass. Bigger black holes show slower variations, so we can use the X-ray variability to measure the mass of the (larger, more distant) black holes," Uttley said.
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eso0128 — Nota de imprensa científica
Dancing around the Black Hole
14 de Agosto de 2001: Supermassive Black Holes are present at the centres of many galaxies, some weighing hundreds of millions times more than the Sun. These extremely dense objects cannot be observed directly, but violently moving gas clouds and stars in their strong gravitational fields are responsible for the emission of energetic radiation from such "active galaxy nuclei" (AGN). A heavy Black Hole feeds agressively on its surroundings. When the neighbouring gas and stars finally spiral into the Black Hole, a substantial fraction of the infalling mass is transformed into pure energy. However, it is not yet well understood how, long before this dramatic event takes place, all that material is moved from the outer regions of the galaxy towards the central region. So how is the food for the central Black Hole delivered to the table in the first place? To cast more light on this central question, a team of French and Swiss astronomers has carried out a series of trailblazing observations with the VLT Infrared Spectrometer And Array Camera (ISAAC) on the VLT 8.2-metre ANTU telescope at the ESO Paranal Observatory. | 0.85944 | 3.351946 |
Today, for the first time ever — we have an actual image taken of a black hole!
Specifically, the black hole at the centre of the Messier 87 (M87) galaxy which is 55 million light-years away from us. Everything you have seen previously were artistic impressions of what we thought black holes would look like. The astounding photo was taken by the Event Horizon Telescope (EHT), a network of eight radio telescopes including such varied locations as Antarctica and Spain. More than two-hundred scientists were involved in this massive scientific effort.
So what am I looking at?
You are looking at the accretion disk (gas, dust and other material in space that has come close to a black hole but not quite close enough to be sucked into it) of a black hole with a mass of 6.5 billion times that of our own sun. The black hole itself is essentially invisible to us because nothing, not even light, can escape the gravitational field created by it. Thus, the dark circular shape you see in the image is the black hole, as well as something called the event horizon. The event horizon defines the area around the black hole from which no light or matter can escape. This is why the circular shape shown is not the black hole alone but rather the black hole and its generated event horizon.
How was the image taken?
The image was taken by 8 radio telescopes here on Earth using something called Very-long-baseline-interferometry which basically creates a virtual telescope about the same size as the Earth. Because these are radio telescopes and not optical telescopes, we are actually looking at the radiation emitted by the material surrounding the black hole (the brighter the colour, the more emitted radiation) and not an actual optical photograph. This is incredibly useful as it allows us to “see” the material around the black hole from much farther away than with an optical telescope . These telescopes generated astonishingly large amounts of data (5,000 trillion bytes worth!) and it took two weeks to compile all the information generated into the image we now have using supercomputers.
Is this what was expected? | 0.844561 | 3.519062 |
Astronomers have found the youngest still-forming solar system yet seen, an infant star surrounded by a swirling disk of dust and gas more than 450 light-years from Earth in the constellation Taurus.
The star currently has about one-fifth the mass of the Sun, but, the scientists say, will likely pull in material from its surroundings to eventually match the Sun’s mass. The disk surrounding the young star contains at least enough mass to make seven Jupiters, the largest planet in our Solar System.
“This very young object has all the elements of a solar system in the making,” said John Tobin, of the National Radio Astronomy Observatory. Tobin and his colleagues used the Submillimeter Array and the Combined Array for Millimeter-wave Astronomy to study the object, called L1527 IRS, residing in a stellar nursery called the Taurus Cloud.
The nascent solar system is no more than 300,000 years old, compared to the 4.6-billion-year age of our Sun and its planets. “It may be even younger, depending on how fast it accumulated mass in the past,” Tobin explained.
The young star is one of the closest examples of the earliest stage of star formation. The astronomers used the millimeter-wave observatories to detect both dust and carbon monoxide around the object. They were the first observers to conclusively show that the young star is surrounded by a rotating disk of material, and the first to be able to measure the mass of the protostar itself.
By measuring the Doppler shift of radio waves coming from carbon monoxide in the disk, they were able to show that the rotation speed in the disk changes with the material’s distance from the star in the same fashion that the orbital speeds of planets change with distance from the Sun.
This pattern, called Keplerian rotation, “marks one of the first essential steps toward forming planets, because the disk is supported by its own rotation, will mediate the flow of material onto the protostar and allow the planet formation process to begin,” said Hsin-Fang Chiang of the University of Illinois and the Institute for Astronomy of the University of Hawaii.
“This is the youngest protostar found thus far to show that characteristic in a surrounding disk,” Tobin said. “In many ways, this system looks much like we think our own Solar System looked when it was very young,” he added. Previous observations from the Gemini Observatory suggested the presence of a large disk surrounding the protostar. This motivated Tobin and his team to pursue high-resolution millimeter-wave observations, confirming the presence of the disk and measuring its rotation.
The astronomers have received approval to improve their understanding of L1527 IRS by making high-precision observations with the Atacama Large Millimeter/submillimeter Array (ALMA), an international telescope system nearing completion at high elevation in northern Chile.
“ALMA’s advanced capabilities will allow us to study more such objects at greater distances,” Tobin said. “With ALMA, we will be able to learn more about how the disks form and how quickly the young stars grow to their full size, and gain a much better understanding of how stars and their planetary systems begin their lives,” he added.
Tobin and Chiang worked with Lee Hartmann and Nuria Calvet of the University of Michigan; David Wilner of the Harvard-Smithsonian Center for Astrophysics; Leslie Looney of the University of Illinois; and Laurent Loinard and Paola D’Alessio of the Radioastronomy and Astrophysics Center of the National Autonomous University of Mexico. The astronomers published their findings in the December 6 issue of the scientific journal Nature.
Dave Finley, Public Information Officer | 0.860635 | 3.977515 |
Whether there is life elsewhere in the universe is a question people have pondered for millennia, and within the last few decades, great strides have been made in our search for signs of life outside of our solar system.
NASA missions like the space telescope Kepler have helped us document thousands of exoplanets — planets that orbit around other stars. And current NASA missions like Transiting Exoplanet Survey Satellite (TESS) are expected to vastly increase the current number of known exoplanets. It is expected that dozens will be Earth-sized rocky planets orbiting in their stars’ habitable zones, at distances where water could exist as a liquid on their surfaces. These are promising places to look for life.
This will be accomplished by missions like the soon-to-be-launched James Webb Space Telescope, which will complement and extend the discoveries of the Hubble Space Telescope by observing at infrared wavelengths. It is expected to launch in 2021 and will allow scientists to determine if rocky exoplanets have oxygen in their atmospheres. Oxygen in Earth’s atmosphere is due to photosynthesis by microbes and plants. To the extent that exoplanets resemble Earth, oxygen in their atmospheres may also be a sign of life.
Not all exoplanets will be Earth-like, though. Some will be, but others will differ from Earth enough that oxygen doesn’t necessarily come from life. So with all of these current and future exoplanets to study, how do scientists narrow down the field to those for which oxygen is most indicative of life?
To answer this question, an interdisciplinary team of researchers, led by Arizona State University, has provided a framework called a “detectability index” that may help prioritize exoplanets that require additional study. The details of this index have recently been published in the Astrophysical Journal of the American Astronomical Society.
“The goal of the index is to provide scientists with a tool to select the very best targets for observation and to maximize the chances of detecting life,” said lead author Donald Glaser of ASU’s School of Molecular Sciences.
The oxygen detectability index for a planet like Earth is high, meaning that oxygen in Earth’s atmosphere is definitely due to life and nothing else. Seeing oxygen means life. A surprising finding by the team is that the detectability index plummets for exoplanets not too different from Earth.
Although Earth’s surface is largely covered in water, Earth’s oceans are only a small percentage (0.025%) of Earth’s mass. By comparison, moons in the outer solar system are typically close to 50% water ice.
“It’s easy to imagine that in another solar system like ours, an Earth-like planet could be just 0.2% water,” said co-author Steven Desch of ASU’s School of Earth and Space Exploration. “And that would be enough to change the detectability index. Oxygen would not be indicative of life on such planets, even if it were observed. That’s because an Earth-like planet that was 0.2% water — about eight times what Earth has — would have no exposed continents or land.”
Without land, rain would not weather rock and release important nutrients like phosphorus. Photosynthetic life could not produce oxygen at rates comparable to other nonbiological sources.
“The detectability index tells us it’s not enough to observe oxygen in an exoplanet’s atmosphere. We must also observe oceans and land,” Desch said. “That changes how we approach the search for life on exoplanets. It helps us interpret observations we’ve made of exoplanets. It helps us pick the best target exoplanets to look for life on. And it helps us design the next generation of space telescopes so that we get all the information we need to make a positive identification of life.”
Scientists from diverse fields were brought together to create this index. The formation of the team was facilitated by NASA’s Nexus for Exoplanetary System Science (NExSS) program, which funds interdisciplinary research to develop strategies for looking for life on exoplanets. Their disciplines include theoretical and observational astrophysics, geophysics, geochemistry, astrobiology, oceanography and ecology.
“This kind of research needs diverse teams, we can’t do it as individual scientists” said co-author Hilairy Hartnett, who holds joint appointments at ASU’s School of Earth and Space Exploration and School of Molecular Sciences.
In addition to lead author Glaser and co-authors Harnett and Desch, the team includes co-authors Cayman Unterborn, Ariel Anbar, Steffen Buessecker, Theresa Fisher, Steven Glaser, Susanne Neuer,Camerian Millsaps, Joseph O’Rourke, Sara Imari Walker and Mikhail Zolotov, who collectively represent ASU’s School of Molecular Sciences, School of Earth and Space Exploration, and School of Life Sciences. Additional scientists on the team include researchers from the University of California Riverside, Johns Hopkins University and the University of Porto (Portugal).
It is the hope of this team that this detectability index framework will be employed in the search for life.
“The detection of life on a planet outside our solar system would change our entire understanding of our place in the universe,” Glaser said. “NASA is deeply invested in searching for life, and it is our hope that this work will be used to maximize the chance of detecting life when we look for it.”
Quelle: New American University | 0.897697 | 3.913836 |
Venus is a particularly strange planet, and this is part of the reason why planetary scientists have taken so much interest in learning more about it. Unfortunately, deploying landers on the Venusian surface to explore isn’t much of an option because the planet’s environment is so harsh that they’d quickly fail. That said, external observations are more feasible and long-term.
Image Credit: JAXA/ISAS/DARTS/Damia Bouic
One of the ways planetary scientists can make external observations of Venus is with JAXA’s Akatsuki spacecraft, which has been orbiting the planet since the end of 2015. Fortunately, Akatsuki comes equipped with infrared imagers, which makes the spacecraft ideal for observing the depths of the Venusian atmosphere.
JAXA initially deployed its Akatsuki spacecraft in an effort to learn more about Venus’ super-rotation, which is a phenomenon where the planet’s atmospheric layers rotate several times faster than the planet’s terrestrial surface. On the other hand, the spacecraft is doing much more than that, such as unveiling the secrets that hide within the planet’s atmospheric layers.
Planetary scientists have no trouble observing Venus' uppermost clouds because they're the first thing you see when you peer at the planet with a space telescope. But observing the planet’s inner cloud layers is something that only Akatsuki’s infrared capabilities could achieve, and according to a paper now published in the journal Geophysical Research Letters, scientists are now reading into it.
"We observed completely unexpected events," said study lead author Javier Peralta, a researcher with Japan Aerospace Exploration Agency (JAXA). "We have discovered that the middle clouds are not as quiet or as boring as they seemed during previous missions."
As it would seem, Venus’ middle cloud layer is vastly different from the planet’s uppermost cloud layer. The former is vastly inconsistent with the latter, and they exhibit an entirely different albedo, which means that they reflect different amounts of sunlight back into space. The findings have implications for the composition of Venus’ middle cloud layer, and experts are somewhat excited about it.
Venus’ middle cloud layer sometimes exhibited a mix of dark and light clouds, but other times, only displayed featureless light clouds. The researchers go on to explain that these features are consistent with a process on Earth called convection, which is often responsible for causing thunderstorms.
Even the clouds’ albedo seemed to be unpredictable. Sometimes the clouds absorbed more sunlight, and other times, they absorbed less. This impacted Akatsuki’s ability to penetrate the clouds with infrared light, giving researchers the idea that Venus’ middle cloud layer either sports some type of infrared-absorbing compound or varies in thickness from one place to another.
As you might come to expect, the research is raising more questions than it answers, and that’s good for science. It’s possible that Venus’ super-rotation has something to do with the strange characteristics encompassing the planet’s middle cloud layer, but the only way planetary scientists can know for sure is to continue studying the planet and gathering data for analysis.
Perhaps NASA’s upcoming James Webb Space Telescope will provide more clues… | 0.888077 | 4.009895 |
Just recently, Sloan and Wolfendale published a paper in Environmental Research Letters, called "Testing the proposed causal link between cosmic rays and cloud cover". In the Institute of Physics Press Release, it said, "New research has deal a blow to the skeptics who argue that climate change is all due to cosmic rays rather than man made greenhouse gases". Did it really?
First, we should note that so called "skeptics" like myself or my serious colleagues never claimed that cosmic rays explain all the climate change, it does however explain most of the solar-climate link and a large fraction (perhaps 2/3's of the temperature increase over the 20th century).
Now for the paper itself.
Sloan and Wolfendale raise three points in their analysis. Although I certainly respect the authors (Arnold Wolfendale is very well known for his contributions to the subjects of cosmic rays and high energy astrophysics, he was even the astronomer royal, and for good reasons), their present critique rests on several faulty assumptions. Here I explain why each of the three arguments raised cannot be used to discredit the cosmic-ray/climate link.
Lack of latitudinal dependence:
According to Sloan and Wolfendale, if clouds are affected by the cosmic ray flux, they should exhibit the same latitudinal dependence as the cosmic ray flux variations. That is to say, because different magnetic latitudes have notably different cosmic ray flux variations, the relative cloud cover variations should similarly have a large dependence on the magnetic latitude. Although at first is sounds logical, this critique misses an important issue, and that is that the CRF variations at the top of the atmosphere are much larger than those at lower altitudes since the latter depends on the variations of much higher energy cosmic rays, those needed to penetrate the atmosphere. Let us look in more detail.
Sloan and Wolfendale compare the latitudinal dependence of solar min to solar max neutron monitor variations to the latitudinal variations of the solar-min to solar-max Low altitude Cloud Cover (LCC) variations. This wrongfully assumes that the ionization rate governing the low atmosphere (and with it the clouds) varies the same way as the neutron monitors.
The neutron monitors have a very weak dependence on the amount of atmosphere above them. The reason is that once neutrons are formed from cosmic ray spallation at the top of the atmosphere, they easily continue to the ground because they are neutral. This implies that the neutron monitor count rate will indeed be nearly proportional to the cosmic ray flux reaching the top of the atmosphere, and the latitudinal dependence will heavily depend on the magnetic cut-off.
On the other hand, the flux of ionizing particles to the lower atmosphere critically depends on the amount of atmosphere above. In fact only primary cosmic ray particles above about 10 GeV can generate showers of which their secondary charged particles can give any atmospheric ionization at an altitude of a few kilometers. The bulk of the low atmosphere ionization is actually generated by primary cosmic rays with energies a few times higher. This implies that the latitudinal dependence of the low altitude ionization rate is very weakly dependent on the magnetic latitude. This is because the magnetic field has an effect only for cosmic ray particles of 0 to 15 GeV, which are anyway blocked by the atmosphere!
Thus, the data to compare with would not have been with neutron monitor data but with ionization chambers which exhibit a much smaller latitudinal dependence. Another option is to calculate the actual latitudinal dependence of the atmospheric ionization variations. This was done by Usoskin et al. (2004), who took the top-of-the-atmosphere variations in the CRF, and using a code to calculate the shower products, calculated the actual latitudinal ionization rate variations.
They found that the relative change in the LCC is the same as the relative change in the ion density (which itself is proportional to the square root of the ionization rate). Both vary by several percent from equator to pole over the solar cycle. This can be seen in fig. 2. In other words, the latitudinal dependence of the cloud cover variations is totally consistent with the CRF/cloud cover mechanism. For comparison, the solar cycle variation in the neutron monitor data is almost 20% at the poles, and 5% at the equator.
Fig 1: (from Sloan and Wolfendale). Top panel: Sloan and Wolfendale expect the solar-min to solar-max variations in the cloud cover to have the same latitudinal dependence (i.e., magnetic cut-off dependence) as that of the neutron monitor variations. This assumption ignores the fact that low atmosphere ionization is generated by CRF particles of relatively high energy, those needed to penetrate the atmosphere. As a consequence, the ionization variations are only of a few percent, and in fact consistent with the observed cloud cover variations (see fig. 2 below). Bottom panel: Sloan and Wolfendale find that the cloud cover variations lead the cosmic ray flux variations by about 3 months, which according to them, is inconsistent with the mechanism. As we show below, this lead is actually consistent given the climate response.
Fig 2: (From Usoskin et al. 2004). The observed latitudinal variation in the cloud cover as a function of the magnetic latitude (right) or as a function of the atmospheric ionization variations (left). The graphs clearly demonstrate that the cloud cover varies as expected from the ionization variations.
Cloud cover CRF lead:
The next criticism Sloan and Wolfendale raise is the fact that when the cloud cover is correlated with the cosmic ray flux over the 11-year solar cycle, it appears that the cloud cover leads the cosmic ray flux variations by about 3 months (see panel 2 of fig. 1 above). If cosmic ray flux affect the cloud cover, such a lead should not be observed.
This would have been the case if all the cloud cover variations arise only from cosmic ray flux variations. However, Sloan and Wolfendale did not consider that the clouds are part of the climate system. The cloud also react, for example, to the varying global temperature, either variations due to the solar cycle, which lag behind the radiative forcing, or altogether unrelated temperature variations.
We can estimate the phase mismatch between the cloud cover variations (arising from the 11-year solar cycle) and the cosmic ray flux. Towards this goal we need to estimate LCC changes arising from the temperature variations. This depends on the cloud feedback in the climate system. We can expect it to be between 1 to 2 (W/m2)/°C if we want the cloud feedback to give a climate sensitivity of 1 to 1.5°C per CO2 doubling, which is the sensitivity consistent with the cosmic ray cloud cover link (see http://www.sciencebits.com/OnClimateSensitivity).
We also know that the global temperature changes by about 0.1°C between solar maximum and solar minimum, with a delay of a 1/8 cycle. (e.g., Nir J. Shaviv, "On Climate Response to Changes in the Cosmic Ray Flux and Radiative Budget", JGR-Space, vol. 110, A08105, and references therein).
The two numbers imply that we should expect a cloud feedback radiative forcing of about [0.1°C] x [1 to 2 (W/m2)/°C] = 0.1 to 0.2 W/m2. Since ERBE shows that low altitude clouds are responsible for a net forcing of 17 W/m2 from their 30% area fraction coverage, if the cloud feedback is through low clouds, then we can expect an area fraction change of about (0.1-0.2) / 17 * 30% ~ 0.17 to 0.35%.
More quantitatively, we see that the LCC changes by about 1.5% over the solar cycle (presumably from the CRF variations). The total LCC will therefore precede the CRF by something like [(0.17-0.35%) / 1.5% / sqrt(2)] / (2π) of a cycle, i.e., about 1.8 to 3.5 months. This of course is consistent with the observations!
No apparent effect during Forbush decreases.
The last point raised by Sloan and Wolfendale is the fact that no effect is observed during Forbush decreases. These are several-day long events during which the CRF reaching Earth can decrease by as much as 10%-20%. Sloan and Wolfendale expect to see a decrease in the cloud cover during the events, but just like with the latitudinal effect, they expect to see an effect which is much larger than should actually be present.
Sloan and Wolfendale plot a graph for the cloud cover reduction vs. the cosmic ray reduction during Forbush events, based on the Oulu neutron monitor data. For the largest event, the Oulu neutron count rate decreased by about 15%. If the cloud reduction during the Forbush decreases should be similar to that over the solar cycle, a 7% reduction in the cloud cover is expected.
Fig 3: (From Sloan & Wolfendale) The reduction in the LCC during Forbush decreases. The straight line is the expectation according to Sloan and Wolfendale. The correct expectation should consider that the cloud data points are either weekly (D2) or monthly (D1) averages. Over these durations, the average CR reduction is smaller than the reduction over 1 day for example. For D2, the slope should be about 3 times smaller, and more than 10 times smaller for the D1 averages.
At face value this might seem like a real inconsistency, but at closer scrutiny it becomes clear where the discrepancy arises from. Fig. 3 plots the CRF reduction following the biggest Forbush event between 1982 and 2002, which took place in 1991. Indeed, one can see that the immediate reduction in the Oulu count is of order 15%, however, the data points for the cloud cover, plotted by Sloan and Wolfendale are either monthly average or weekly averages. Over the week following the 1991 even, the average CRF reduction in Oulu was actually roughly 5%, not 15%. This implies that the expected LCC anomaly is three times smaller, and therefore drowns under noise. The situation is much worse for the monthly data.
Fig: 4: The largest Forbush decrease between 1982 and 2002, from Kudela & Brenkus (2002). Over 1 day, the Oulu neutron monitor decrease is about 15%. However, if averaged over a week or a month, the average reduction is much smaller.
To see effects, one therefore needs to use daily averages of the cloud cover. This was done, for example, by Harrison and Stephenson (2006) who found that there is an apparent Forbush decrease in the cloud cover over Britain.
Fig 5: To see the effects of Forbush decreases, one has to look at daily data, and then, because of the noise, average many Forbush decreases. The graph depicted here demonstrates that during Forbush decreases, there is a statistically significant reduction in the odds for an overcast day. That is, less cosmic rays implies less clouds. The data is from Harrison and Stephenson (2006), for stations located in the UK.
Sloan and Wolfendale raised three critiques which supposedly discredit the CRF/climate link. A careful check, however, reveals that the arguments are inconsistent with the real expectations from the link. Two arguments are based on the expectation for effects which are much larger than should actually be present. In the third argument, they expect to see no phase lag, where one should actually be present. When carefully considering the link, Sloan and Wolfendale did not raise any argument which bares any implications to the validity or invalidity of the link.
One last point. Although many in the climate community try to do their best to disregard the evidence, there is a large solar-climate link, whether on the 11-year solar cycle (e.g., global temperature variations of 0.1°C), or on longer time scales. Currently, the cosmic-ray climate link is the only known mechanism which can explain the large size of the link, not to mention that independent CRF variations were shown to have climatic effects as well. As James Whitcomb Riley supposedly once said:
- Harrison R.G. & D.B. Stephenson, Proc. Roy. Soc. A, doi:10.1098/rspa.2005.1628, 2006
- Kudela, K. & Brenkus, R., J. Atmos. Sol.-Terr. Phys. 66, 1121, 2004
- Shaviv, N.J., J. Geophys. Res. 110, A08105, 2005
- Sloan T. and A.W. Wolfendale, Environ. Res. Lett. 3 024001, 2008
- Usoskin, I.G., et al., Geophys. Res. Lett., 31, L16109, doi:10.1029/2004GL019507, 2004 | 0.815199 | 3.803875 |
Authors: Zhenzhen Li, Hongyan Zhou, Lei Hao, Xiheng Shi
First Author’s Institution: Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China
Behind the thick wall of dust and gas
Starting from their birth, supermassive black holes (SMBHs) co-evolve with their host galaxies through active galactic nuclei (AGNs) feedback. In the central region of the obscured AGN, a donut-shaped thick wall of dust and gas surrounds the accretion disk. This wall, referred to as the “dusty torus”, separates the broad emission line (BEL) region and the narrow emission line (NEL) region. As a result, the dusty torus can absorb most, if not all, of the BELs.
The scale of the torus region (pc-scale to ~100 pc) we are talking about here is quite small compared to that of the entire host galaxy. Direct observations are therefore challenging. However, it is very important to understand what occurs in the central region because AGN outflows can strongly affect galactic evolution from the center.
Today’s paper provides us with more information about AGN outflows.
Although it seems we can only observe NELs and suppressed BELs outside of the dusty torus, the authors show that there is more to see. When the authors pointed the Hubble Space Telescope (HST) towards a partially obscured quasar, J1516+1900, aside from the expected NELs and BELs, they also found a group of special lines in the ultraviolet (UV) spectrum. Unlike BELs and NELs, these unusual lines in the circumnuclear region have intermediate widths with FWHM about 1900 km/s, which may shed light on what is going on behind the curtain. Now the question is where these special intermediate emission lines (IEL) come from.
The unusual intermediate emission lines (IELs)
When the authors used a typical quasar model with dust extinction to fit the spectral energy distribution (SED) of their obscured quasar, they first noticed an excess in the far-UV continuum. After checking the X-ray luminosity, they found that the observed obscuration is stronger than the theoretical calculation. The photometry suggests that a blob of gases is located beyond the torus and is absorbing extra photons!
After a close examination of the individual emission lines in the UV (shown in Figure 1), the authors found that the broad components of UV emission lines are completely missing, leaving only the intermediate-width components. The authors then separated the IELs into two groups: a major group that is relatively still, and a minor group with blueshift. Both groups show little extinction, which places the origin of the IELs outside of the dusty torus.
Since both the blob of gases and the IEL region are beyond the torus, the question then became whether the IELs originated from the gases instead of photoionization by the central AGN. To answer this question and find the origin of these special lines, the authors simulated the locations of IEL regions. Their results suggest that the suspicious gaseous blob could be an ultradense region filled with shock-heated gases. Therefore, this region is dense and warm enough to produce the unabsorbed IELs in the UV band. On the other hand, even with a sophisticated model, AGN cannot ionize those hydrogen particles without extinction.
The production process of the IELs
After relating IELs to the ultradense gases beyond the torus, the authors demonstrate the production of these weird IELs in detail. Figure 2 shows an illustration of what happens in the circumnuclear region of quasar J1516+1900. Based on the reddened SED fitting model, it is certain that a dusty torus surrounds the active central SMBH, blocking our view to the inner region. As a result, there is barely any signal coming from the BEL region.
Although the outflows originate from the inner accretion disk, these gases do not want to be confined and silenced in the torus like BELs. Therefore, once the outflows are pumped with energy, they collide into whatever obstacles are standing in their way and try to break through.
Since the quasar is partially obscured and the torus is clumpy, some outflows are able to get through the gaps. On their way out, these outflowing gases bump into the surrounding isolated clouds, creating a shock. This shock further heats the gases and gives rise to the blue-shifted minor IELs.
Unfortunately, not all of the outflows can make it out easily. Those that are unable to escape through the gaps go straight head-to-head with the huge dense torus. In this case, the outflowing gases end up violently colliding into the inner wall and fail to escape. However, during the collision, the high kinetic energy ignites a giant spark visible to the outside. This spark is the unshifted dominating major IELs.
If these assumptions are true, the IELs may provide a direct link between emission-line properties and quasar outflows, a finding that may help astronomers understand the physical processes of the outflows and the effect on the SMBH-galaxy co-evolution.
Featured image: AGN outflows & feedback (Credit: Nature) | 0.864417 | 4.043849 |
21 June 2016
By Elizabeth Deatrick
A vast ocean of water beneath the icy crust of Saturn’s moon Enceladus may be more accessible than previously thought, according to new research. A new study has revealed that near the moon’s poles, the ice covering Enceladus could be just two kilometers (one mile) thick—the thinnest known ice shell of any ocean-covered moon. The discovery not only changes scientists’ understanding of Enceladus’ structure, but also makes the moon a more appealing target for future exploration, according to the study’s authors.
Until recently, scientists saw Jupiter’s moon Europa as the moon most likely to yield new understanding into worlds with ice-covered oceans, according to Gabriel Tobie, a planetary scientist at the Laboratory of Planetology and Geodynamics of CNRS, the University of Nantes, and the University of Angers in Nantes, France and co-author of the new study.
Estimates of Europa’s ice shell thickness range from just a few kilometers to over 10 kilometers to over 20 kilometers (12 miles) thick. By comparison, Enceladus’ ice was previously thought to be 20 to 60 kilometers (12 to 37 miles) thick. But the new study suggests that at its south pole, Enceladus’ ice is less than five kilometers (three miles) thick, and possibly as little as two.
The thinness of the ice opens up future mission possibilities, according to authors of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union. With ice this thin, an orbiting probe could use radar to see what lies beneath the moon’s shell. Though substantial engineering challenges would have to be solved first, scientists could even land a probe on the moon itself to drill down through the ice and sample the water below, Tobie said. Other scientists have proposed that ocean-covered moons like Europa could harbor life, and getting a look at Enceladus’ oceans could help us understand whether life could exist there, according to the authors.
The study yielded a second unexpected result: Enceladus’ core is likely much hotter than previously thought. Ice acts as an insulator, keeping the planet’s global oceans warm, but a thinner ice shell holds less heat. To maintain the same amount of water in the global oceans, with a thinner ice shell, Enceladus’ rocky core would have to generate much more heat than previously thought, according to the authors.
A new synthesis of data
In the new study, the research team used publicly available data collected by NASA’s Cassini spacecraft to measure Enceladus’ gravity and topography. The gravitational influence of Saturn causes liquid water on Enceladus to move differently than ice or rock, a movement called libration. The researchers used Enceladus’ gravity, shape, and libration data to build a computer model of the moon and determine how much of it is water, ice and rock.
The team concluded that the ice sheet over Enceladus was not only thinner than previously thought, but that its thickness varied over the surface of the planet. The ice sheet is noticeably thinner near the poles—especially the south pole, they found.
“I think it’s a very nice piece of work,” said Francis Nimmo, a planetary scientist at the University of California Santa Cruz who was not involved with the study. “On the one hand, you have the gravity and topography, and on the other hand you have the librations. They’re using both those pieces of data, which hasn’t been done before.”
—Elizabeth Deatrick is a science writing intern at AGU. | 0.900993 | 3.881573 |
NASA’s Cassini Spacecraft is nearing the end of a long journey rich with scientific and technical accomplishments, and it is having a powerful influence on future exploration.
In revealing that Saturn’s moon Enceladus has many of the ingredients needed for life, the Cassini-Huygens mission has inspired a pivot to the exploration of “ocean worlds” that has been sweeping planetary science over the past decade.
“Cassini has transformed our thinking in so many ways, but especially with regard to surprising places in the solar system where life could potentially gain a foothold,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. “Congratulations to the entire Cassini team!”
Onward to Europa
Jupiter’s moon Europa has been a prime target for future exploration since NASA’s Galileo mission, in the late 1990s, found strong evidence for a salty global ocean of liquid water beneath its icy crust. But the more recent revelation that a much smaller moon like Enceladus could also have not only liquid water, but also chemical energy that could potentially power biology, was staggering.
Many lessons learned during Cassini’s mission are being applied to planning NASA’s Europa Clipper mission, planned for launch in the 2020s. Europa Clipper will fly by the icy ocean moon dozens of times to investigate its potential habitability, using an orbital tour design derived from the way Cassini has explored Saturn. The Europa Clipper mission will orbit the giant planet — Jupiter in this case — using gravitational assists from its large moons to maneuver the spacecraft into repeated close encounters with Europa. This is similar to the way Cassini’s tour designers used the gravity of Saturn’s moon Titan to continually shape their spacecraft’s course.
In addition, many engineers and scientists from Cassini are serving on Europa Clipper and helping to develop its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer and Cosmic Dust Analyzer teams are developing extremely sensitive, next-generation versions of their instruments for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will help inform planning for Europa Clipper, should plume activity be confirmed on Europa.
Returning to Saturn
Cassini also performed 127 close flybys of Saturn’s haze-enshrouded moon Titan, showing it to be a remarkably complex factory for organic chemicals — a natural laboratory for prebiotic chemistry. The mission investigated the cycling of liquid methane between clouds in its skies and great seas on its surface. By pulling back the veil on Titan, Cassini has ushered in a new era of extraterrestrial oceanography – plumbing the depths of alien seas — and delivered a fascinating example of earthlike processes occurring with chemistry and at temperatures markedly different from our home planet.
In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission’s many discoveries. Mission concepts under consideration include spacecraft to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.
Giant Planet Atmospheres
Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent Planetary Science Decadal Survey continues to support interest in sending such a mission to Saturn. By directly sampling Saturn’s upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an eventual Saturn atmosphere probe.
Farther out in the solar system, scientists have long had their eyes set on exploring Uranus and Neptune. So far, each of these worlds has been visited by only one brief spacecraft flyby (Voyager 2, in 1986 and 1989, respectively). Collectively, Uranus and Neptune are referred to as “ice giant” planets, because they contain large amounts of materials (like water, ammonia and methane) that form ices in the cold depths of the outer solar system. This makes them fundamentally different from the gas giant planets, Jupiter and Saturn, which are almost all hydrogen and helium, and the inner, rocky planets like Earth or Mars. It’s not clear exactly how and where the ice giants formed, why their magnetic fields are strangely oriented, and what drives geologic activity on some of their moons. These mysteries make them scientifically important, and this importance is enhanced by the discovery that many planets around other stars appear to be similar to our own ice giants.
A variety of potential mission concepts are discussed in a recently completed study delivered to NASA in preparation for the next Decadal Survey — including orbiters, flybys and probes that would dive into Uranus’ atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini’s mission.
The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter. | 0.805662 | 3.792415 |
Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo
Join us at Japan House London for a talk by Professor Kajita Takaaki, Director of the University of Tokyo’s Institute for Cosmic Ray Research (ICRR), and joint winner of the 2015 Nobel Prize in Physics for the discovery of neutrino oscillations.
Humanity’s quest to understand the structure of nature is an eternal journey. In the 20th century, scientists discovered that 12 elementary particles, tinier than any atoms, and four fundamental forces govern all phenomena in the universe. The Standard Model developed by modern particle physics had predicted almost every known feature of all elementary particles except one: the mass of neutrinos.
Neutrinos are the least understood elementary particles in nature. Incredibly difficult to study, they are known as ‘ghost particles’, because they interact rarely with their surroundings and pass through most detectors.
The Super-Kamiokande neutrino observatory, is a tank filled with ultrapure water, 40 metres in height and diameter, buried deep under a mountain in Gifu Prefecture in Japan. The detector is equipped with over 10,000 of the world’s largest ultra-sensitive light sensors which can detect weak light from neutrino interactions. It was here in 1998, that Professor Kajiita and his team discovered a phenomenon called ‘neutrino oscillations’, which proved that neutrinos have mass. This discovery challenged the Standard Model for particle physics and led to Professor Kajita being awarded the Nobel Prize in Physics in 2015.
This is the beginning of an all-new chapter in particle physics. The role of neutrino mass is still unknown, and scientists all over the world, including in Japan, are building new experiments to deepen their understanding of neutrinos.
In this talk, Professor Kajita provides behind-the-scenes insight into the history of his discovery and discusses the future prospects of the very exciting field of neutrino physics.
About Professor Kajita Takaaki:
Professor Kajita Takaaki was born in Higashi-Matsuyama, Saitama, Japan. He studied at Saitama University and at the University of Tokyo where he received his doctorate in 1983. Since 1998, he has been affiliated with the Institute for Cosmic Ray Research (ICRR) which hosts dozens of projects all over the world, and become the institute’s director in 2015. He was awarded the Nobel Prize in Physics in December 2015. Recently, ICRR have started the operation of the Kamioka Gravitational Wave Detector (KAGRA) at the Kamioka mine next to the Super-Kamiokande. The next-generation experiment, Hyper-Kamiokande starts construction in 2020. | 0.849878 | 3.760855 |
It’s interesting to contemplate what has really changed about the way we see the world in ones own lifetime. Many major scientific developments I hear about as if new have been around long before I was born, and are merely percolating slowly into the public consciousness – witness for example the many TV programmes explaining quantum physics. Other new discoveries, such as the Higgs boson, are so small that we struggle to have any comprehension. But the impact of the Hubble space telescope, launched almost exactly 25 years ago by space shuttle, has been quite extraordinary. Astronomy, our oldest science, has been reborn, and we can all share in it in a way that has never been possible before
There’s a memorable short sci-fi story, Nightfall, by Isaac Asimov, written in 1941, about a world where the presence of six sun means that true darkness has never been known in living memory. Puzzling evidence that civilization has risen and disappeared in a cyclical fashion, has seeded the idea that something is revealed in those rare moments of darkness when all suns disappear from view, that causes psychological disturbance – a mass hysteria – so profound that it leads to the collapse of all culture. All knowledge disappears, and things have to start again from scratch . So people start to speculate that contrary to their deeply ingrained beliefs, their solar system is not alone, and there might … be other suns! Perhaps, they suggest, seeing this shocking truth causes people’s whole world view to collapse in a catastrophic way.
We read this slightly smugly, because we know that there are not just a few stars, but many. Yet the Hubble, in its short life, has been able to multiply the known universe to mind boggling numbers. We now routinely hear astronomers talk of ‘billions of galaxies, each containing billions of stars’. And even more dramatically, we all get to see the pictures for ourselves. The Hubble is our Nightfall! And ironically, most people live in cities whose glow blocks all but a few stars at night. Compared to Galileo, our night skies are empty.
So I strongly recommend this beautiful book (Expanding Universe. Photographs from the Hubble Space Telescope) published by Taschen, who are perhaps fittingly that better known for aesthetics than for science. Hubble pictures are all around us, in the newspapers, or in ‘pictures of the day’ from NASA, but I think it’s a joy to sit and just look at these large, high quality images that no-one in the history of the world has had the privilege to see before. Size does matter when it comes to images of the universe! And it also feels important for me to be able to sit and contemplate our universe and our (inifinitesimally small) place in it, and perhaps absorb and practise a little more humility in my day-to-day life.
The book is organized in sections that start closer to home in the solar system, our view of which has also changed markedly with Hubble (as well as the travelling robotic probes such as Voyager). So we have photographs of planets, moons and comets, before we move out to the Milky Way, mere thousands of light years away, and continue until we are billions of light years from home (how casually we speak of such numbers). Although most of the book consists of Hubble images, there is some text, but (rightly) not too much, and what there is is in English, French and German. A section at the back interviews Zoltan Levay, Head of Imaging, and asks amongst other things about the coloration, because these are in one sense false colour images: the wavelengths used to generate the images are greater than the narrow wavelengths we see, so there needs to be some conversion. The colours used are not random, and relate to our vision, but I think it’s important to know that there has been a transformation. Perhaps it’s that processing that contributes to an eery similarity to psychedelic sci-fi paintings such as those that graced prog rock albums in the 1970s!
At £30 from Amazon, this book costs more than you might normally spend on a book, but for the universe, it’s a snip! | 0.833352 | 3.072548 |
A binary star is two stars which orbit around each other. For each star, the other is its companion star. Many stars are part of a system with two or more stars. The brighter star is called the primary star, and the other is the secondary.
Binary stars are important in astrophysics because looking at their orbits allows scientists to find out their masses. From this is got the mass–luminosity relationship, and from this is got the masses of individual stars.
Binary stars are not the same as line-of-sight optical double stars, which look close together but are not connected by gravity. Optical double stars may actually be far apart in space, but binary stars are quite close together. The first person to discover and prove true binary stars was the Anglo-German astronomer William Herschel. He published the first catalogue of binary stars, and his son John Herschel found several thousand more and updated the catalogue.
By the modern definition, the term binary star is generally restricted to pairs of stars which revolve around a common centre of mass. Binary stars which can be resolved with a telescope or interferometric methods are known as visual binaries. For most of the known visual binary stars one whole revolution (complete circle) has not been observed yet, they are seen to have travelled along a curved path or a partial arc.
Some stars appear to be in orbit around empty space, and appear not to have a companion. In this case, the companion star is either very small and faint, or it is a neutron star or a black hole. The best-known example of a star with an invisible companion is Cygnus X-1, in which the visible star's companion appears to be a black hole.
The more general term double star is used for pairs of stars which are seen to be close together in the sky. This distinction is rarely made in languages other than English. Double stars may be binary systems or may be merely two stars that appear to be close together in the sky but have vastly different true distances from the Sun. The latter are termed optical doubles or optical pairs.
A visual binary star is one for which the separation of the two stars can be seen with a telescope. The brighter star is the primary and the fainter star is the secondary. Visual binaries take a long time to orbit one another, in the area of hundreds or even thousands of years.
A spectroscopic binary is one in which the two stars cannot be seen separately even with a telescope. They are very close together and move around each other very quickly, over a period of a few weeks or even a few days. However, they can be seen to be two separate stars by using a spectroscope, which is able to record the Doppler change in the color of the light sent out by stars moving quickly toward or away from the Earth.
Some spectroscopic binaries have an orbit that is edge-on to Earth. When this happens, the stars will take turns passing in front of and eclipsing the partner star, in what is called an eclipsing binary. In this case, the amount of light we see from the double dims slightly during the time one star is in front of the other.
An astrometric binary is one where only one companion can be seen. For astrometric binaries fairly near the Earth (up to about 10 parsecs), it may be possible to see the visible companion "wobble" as it moves around its invisible companion. By making measurements over a long period of time, it may be possible to calculate the mass of the visible star and how long its orbit takes. This method is also used to detect the presence of large planets orbiting a star; as of 2007, over two hundred planets have been discovered in this way.
Most binaries are detached binaries. Except for their gravitational pull on one another, they have no effect on each other.
Semidetached and contact binaries
Some binaries are so close to one another that one or both stars is able to pull material from the other. They may share the same stellar atmosphere, and as friction slows them down over a long period, they may merge into one star.
Though it could be possible that binary stars may form when one star passes very close to another, it is highly unlikely (since it would actually take three stars close to one another before two could join), and would occur only in places where stars are densely packed together. Our present understanding is that almost all binaries are formed together in the dense gas clouds where stars are born.
Runaways and novae
It is possible (though not likely) that a passing star will disrupt a binary system and provide enough gravitational force to split the binary. Such separated stars go on to live lives as ordinary single stars. Sometimes, though, enough gravitational force is involved that the two companions speed away from each other at great speeds, resulting in what is known as runaway stars.
Sometimes a star is in orbit around a white dwarf star. If it is large enough and close enough to the white dwarf, the dwarf may suck gasses from its companion's atmosphere. Over a period of time, a great deal of gas may collect on the white dwarf. As this gas is compacted by the white dwarf's gravity, it will eventually undergo nuclear fusion, resulting in a very bright outburst of light, known as a nova. In some cases, the white dwarf may gather so much gas that the explosion completely destroys it, in what is called a supernova. Such an event may also result in runaway stars, as the larger star no longer has a heavy companion which keeps it in orbit.
Images for kids
Binary star Facts for Kids. Kiddle Encyclopedia. | 0.902909 | 4.026484 |
The NASA/ESA Hubble Space Telescope has captured three magnificent sections of the Veil Nebula - the shattered remains of a supernova that exploded some 5 to 10 000 years ago.
Although we don’t usually think about it, the stars twinkling in the night sky don’t shine forever. How long a star lives depends on how big and heavy it is. The bigger the star, the shorter its life. When a star significantly heavier than our Sun runs out of fuel, it collapses and blows itself apart in a catastrophic supernova explosion.
A supernova releases so much light that it can outshine a whole galaxy of stars put together. The exploding star sweeps out a huge bubble in its surroundings, fringed with actual stellar debris along with material swept up by the blast wave. This glowing, brightly-coloured shell of gas forms a nebula that astronomers call a ‘supernova remnant’. Such a remnant can remain visible long after the initial explosion fades away.
A series of three new images taken with the NASA/ESA Hubble Space Telescope reveals magnificent sections of one of the most spectacular supernova remnants in the sky – the Veil Nebula. The entire shell spans about 3 degrees, corresponding to about six full moons. The small regions captured in the new Hubble images provide stunning close-ups of the Veil. Fascinating smoke-like wisps of gas are all that remain visible of what was once a Milky Way star.
Scientists estimate that the supernova explosion occurred some
The intertwined rope-like filaments of gas in the Veil Nebula result from the enormous amounts of energy released as the fast-moving debris from the explosion ploughs into its surroundings and creates shock fronts. These shocks, driven by debris moving at 600 000 kilometres per hour, heat the gas to millions of degrees. It is the subsequent cooling of this material that produces the brilliantly coloured glows.
Like the larger scale ground-based observations, the high-resolution Hubble images display two characteristic features: sharp filaments and diffuse emission. These correspond to two different viewing geometries: sharp filaments correspond to an edge-on view of a shock front, and diffuse emission corresponds to a face-on view of it.
The Hubble images of the Veil Nebula are striking examples of how processes that take place hundreds of light-years away can sometimes resemble effects we see around us in our daily life. The structures have similarities to the patterns formed by the interplay of light and shadow on the bottom of a swimming pool, rising smoke or ragged cirrus clouds.
Why are astronomers interested in studying supernovae and their remnants? Supernovae are extremely important for understanding our own Milky Way. Although only a few stars per century in our Galaxy will end their lives in this spectacular way, these explosions are responsible for making all chemical elements heavier than iron in the Universe. Many elements, such as copper, mercury, gold, iodine and lead that we see around us here on Earth today were forged in these violent events billions of years ago. The expanding shells of supernova remnants were mixed with other material in the Milky Way and became the raw material for new generations of stars and planets.
The chemical elements that constitute the Earth, the planets and animals we see around us – and as a matter of fact our very selves – were built deep inside ancient stars and in the supernova explosions that result in the nebula we are seeing here. The green in the grass and the red of our blood are indeed the colours of stardust.
The Veil Nebula is a prototypical middle-aged supernova remnant, and is an ideal laboratory for studying the physics of supernova remnants: it is fairly nearby, has a large angular size and has a relatively small amount of foreground extinction.
lso known as Cygnus Loop, the Veil Nebula is located in the constellation of Cygnus, the Swan. It is about 1 500 light-years away from Earth. One of the most remarkable parts of the remnant is the so-called Witch’s Broom Nebula (seen to the right in the overview image). The bright blue star – dubbed 52 Cygni and unrelated to the supernova explosion – can be observed with the naked eye on a clear summer’s night.
The images were taken with Hubble's Wide Field and Planetary Camera 2 (WFPC2). The colour is produced by composite of three different images. The different colours indicate emission from different kinds of atoms excited by the shock: blue shows oxygen, green shows sulphur, and red shows hydrogen.
Notes for editors:
The Hubble Space Telescope is a project of international cooperation between NASA and ESA.
For more information:
Lars Lindberg Christensen, Hubble/ESA, Garching, Germany
E-mail: lars @ eso.org
Alessandra Aloisi, ESA/ Space Telescope Science Institute, USA
E-mail: aloisi @ stsci.edu
Ray Villard, Space Telescope Science Institute, Baltimore, USA
E-mail: villard @ stsci.edu | 0.891178 | 4.015862 |
The last time Cosmos was on television was 34 years ago. In 1980, as the inimitable Carl Sagan was dazzling audiences across America, some 1 billion miles away two diminutive flying robots were approaching giant cold worlds never before seen by human eyes. Although other spacecrafts had been to closer planets before, the incredible journeys of the Voyager probes set an unprecedented standard and ushered in a new era of space exploration. Since then, data-gathering spacecraft have been dispatched to explore other planets and moons in greater detail than ever before, probe the sun's amazing structural layers, document asteroid and comet collisions and peer into the deepest reaches of space and time.
Since Sagan's days, what we've been able to learn about our ever complex universe has been nothing short of astounding. With Cosmos coming back to television this year, now's a fantastic opportunity to remind ourselves about the amazing achievements that science and human curiosity have made since it was last on.
1. Pluto is no longer classified as a planet.
Pluto was first observed in 1930, and apart from one of it's moons, Charon, no other objects beyond Neptune were found until 1992. The eventual discovery of Eris in 2005, a trans-Neputunian object bigger than Pluto, ended Pluto's distinction as a planet. Both objects are now classified as dwarf planets, and are known to orbit the sun not independently, but as part of a population of similarly sized objects known as the Kuiper Belt.
2. There is water on Mars.
Although many scientists believed that water once existed on Mars, it wasn't until 2008 when NASA's Phoenix Lander was able to test soil on the Martian surface near the North Pole and finally confirm the presence of water ice on the planet. In 2011 Mars Reconnaissance Orbiter presented the most compelling evidence of flowing water yet, with images that revealed the growth of dark streaks in Martian gullies during the summer. Researchers suggest that these marks are consistent with salty water flowing downslope and evaporating.
3. In fact there's many other places in our Solar System with water. Some even have giant geysers!
We've discovered that water in our Solar System is actually fairly common. Water ice has been detected on the moon, at Mercury's poles and on the asteroid Ceres, and traces of water vapor have been detected in the atmosphere of all the other planets. Perhaps the most exciting discoveries so far are the giant geysers on the icy moons of Europa and Enceladus, which shoot out water vapor from potential subterranean liquid oceans.
4. In 1980 we hadn't found any planets outside of the Solar System. We've since discovered thousands.
The discovery of an exoplanet, or extrasolar planet, was first confirmed in 1992. Since then, thanks to advanced technology such as the Kepler spacecraft, close to 1800 exoplanets have been found, encouragingly demonstrating that alien worlds are common in the universe. But what's especially interesting is that most of these expolanets are closer in mass to the Earth than to Jupiter and many fall within the "habitable zone," meaning they're conducive to water and life. There may even be up to 30,000 habitable worlds within one thousand light years of Earth.
5. We've solved a huge paradox about how the Sun produces its energy.
Nuclear fusion is the process that powers the sun, converting hydrogen to helium. For decades physicists have scratched their heads about why they could only detect one third of the expected amount of one of its by-products, neutrino particles. Initially scientists thought their model of the sun was wrong. In 2001 this mystery was finally solved when experiments revealed that in fact neutrinos can mutate into three different forms. Our general model of the sun was right, we were just unaware of all the particles it could produce.
6. We've learned a whole lot more about non-planetary objects in our solar system.
Interestingly, our investigation of comets and asteroids have revealed that in some ways they're much more similar to each other than we previously thought. We've been lucky enough to witness the impacts of these objects with the Sun, the moon and other planets, as well as spontaneous disintegrations, providing spectacular images in addition to valuable information.
7. Black holes are much more common than we thought.
When Cosmos was last on air, black holes were thought to be rare, appearing in around 1 out of every 100 galaxies. But when the Hubble Space Telescope came along, it showed that in fact the interior of almost all galaxies rotate quickly — up to 1.1 million miles per hour. Scientists concluded this rotation was due to the presence of supermassive material and that black holes are a standard feature of most galaxies.
8. We now know the age of the universe.
Observing the distances between stars and how fast they're moving can help scientists calculate the age of the universe. But before modern space telescopes, sufficiently accurate equipment was unavailable and the best estimates were between 10 to 20 million years. After 1990, the Hubble's clear optics allowed scientists to narrow down the calculation to between 13 to 14 billion years. Since then, the WMAP spacecraft has recorded high resolution cosmic background radiation maps, narrowing this figure down further to 13.8 billion years, with an uncertainty of under 0.3%.
9. The expansion of the universe is accelerating because of "dark energy."
Although scientists have long known that the universe is expanding, many commonly predicted that this expansion would eventually slow down due to gravity. But when scientists could finally measure the rate of expansion by comparing the speed of supernova at different distances, to their surprise they found that the expansion of the universe was accelerating. These observations seemed to contradict the prediction that the gravitational force generated by all the mass in the universe would eventually rein it in. Scientists think that there must be another force that works in the opposite direction — "dark energy." Estimated to account for 68% of the entire universe, dark energy is the next big cosmological mystery waiting to be unravelled.
Today, both Voyagers have since left the Solar System and are now the first human-made objects to explore interstellar space, some 19 billion miles away. Meanwhile back on Earth, Neil deGrasse Tyson is bringing Cosmos to a new audience.
Future space missions hope to put humans on Mars, probe for life in the subterranean oceans of Jupiter and Saturn's moons and build even more powerful particle colliders to better dissect the very fabric of the universe itself. Within this backdrop, today Tyson's remit is strikingly similiar to Sagan's 34 years ago: to inspire and renew a generation's passion and support for the beauty of science and space exploration.
Cosmos: A Spacetime Odessey can be seen on FOX on Sunday nights at 9 p.m., Eastern & Pacific, 8 p.m. Central, and National Geographic on Monday nights at 10 p.m. | 0.9233 | 3.515603 |
"The most primitive objects in the solar system record chemistry that started in the dark regions of cold molecular clouds," says geochemist George Cody of the Carnegie Institution of Washington (CIW). "We can identify such materials by their unusually rich abundances of certain isotopes for example, deuterium."
Astronomers theorize that these dust clouds, once nudged by an outside shockwave, gradually collapsed under their own gravity to form a glowing star surrounded by an accretion disk, where protoplanets took shape. In them the constituents of the interstellar dust were subjected to heat and pressure and reactions with water. Accretionary processes ultimately led to the formation of planets.
Within a band between Jupiter and Mars, however, perturbation by Jupiter's enormous mass interfered with the formation of a planet, leaving the vast rubble field we call the asteroid belt.
"Continuous collisions of asteroids over the past 4.5 billion years yield small fragments that in rare cases crash into the Earth," Cody says. "Most meteorites are pieces of failed planets."
In particular, he says, "organic-rich meteorites tell a spectacular story, but it's one we don't completely understand." To unravel the tale Cody is using a scanning transmission x-ray microscope (STXM) on beamline 5.3.2 at the Advanced Light Source, an instrument initially built by a team led by Harald W. Ade from North Carolina State University and now under the direction of David Kilcoyne of the ALS Scientific Support Group.
A matrix of clues
Cody uses STXM to analyze samples from a class of meteorites called carbonaceous chondrites. What he calls their "rich inventory of organic matter" holds important clues to the evolutionary phases through which they have passed: how much water was present during the processing of their parent bodies, for example, and whether chemical reactions occurred at high or low temperatures. The meteorites take their name from chondrules, or glassy melt droplets, "that must have formed at 1,200 to 1,500 degrees Celsius, embedded in a carbon-bearing matrix that in many cases probably experienced temperatures of not more than 20 degrees C. How is this possible? It's a raging debate."
The carbon in a carbonaceous chondrite is distinctive in another way: "70 to 90 percent of it is insoluble in any solvent," so classic analytic techniques like gas chromatography and mass spectrometry are impractical. Because meteorites typically come in chunks although Cody jokes that one of the hardest things about studying them is "getting the meteorite from the curator's hoard" he and his colleagues have developed analytical methods for applying solid-state nuclear magnetic resonance spectroscopy, or solid-state NMR.
By using NMR to record the chemical shifts of carbon compounds in meteorites, Cody has charted differences like varying ratios of hydrogen to carbon and oxygen to carbon, which reflect chemical processes characteristic of their parent bodies' stage of evolution, and point backward to the unprocessed state of the primal interstellar dust.
Cody has supplemented these solid-state NMR studies with x-ray microscopy and spectroscopy. Because each chemical constituent of a sample absorbs x-rays differently, STXM can make images showing the physical arrangement of chemical compounds in a sample. And STXM has other advantages. Unlike the NMR experiments, it can use very small samples, and it produces results in a hurry.
Says Cody, "All these factors led to STARDUST," a NASA mission led by Donald Brownlee of the University of Washington that will soon bring pieces of a comet and samples of interstellar dust to Earth unaltered material expected to date from before the origin of the solar system.
To catch a flying comet
Finding out what comets are made of requires more than whacking them with heavy objects, as the Deep Impact mission did to Comet Tempel 1 on July 4, 2005. The plume from that impact was imaged by the Deep Impact fly-by spacecraft, which closed to within 500 kilometers of Tempel 1's nucleus, and by other satellites and ground-based telescopes. Once spectra and images and other data are beamed to Earth, Deep Impact will not be heard from again.
A year and a half earlier, on January 2, 2004, the armored STARDUST spacecraft flew through a hail of ejecta to within 263 kilometers of Comet Wild 2's nucleus. It stuck a tennis-racket-shaped panel of aerogel tiles into the debris storm, in which some of the shrapnel embedded itself. The spacecraft is now on its way home and will drop its singular cargo in the Utah desert on January 15, 2006.
Cody showed Scott Sanford, the STARDUST science team leader, his x-ray microscopy and spectroscopy of meteorite samples to make the case for, among its other strengths, beamline 5.3.2's unique ability to make full-edge spectra (features that stand out on an x-ray absorption graph when an atom's inner electrons are kicked into a higher-energy state) of elements like carbon, nitrogen, and oxygen in each sample.
"There will be a lot of microscopes in play," Cody argued, "but this one will get the most information out fast. You have the full bandwidth to look at." By calibrating the x-ray observations against earlier NMR studies, beamline 5.3.2 has created a database of extraterrestrial matter with which the STARDUST samples can be accurately compared.
Partly as a result of his demonstration of what STXM could do, Cody was invited to become a member of the STARDUST experimental team, joining colleagues Andrew Westphal and Anna Butterworth of the University of California at Berkeley's Space Sciences Laboratory (SSL) in the Berkeley Hills.
Westphal and Butterworth are interested not only in comet samples but in another kind of primitive matter STARDUST is collecting the stuff that gives the mission its name. Only one side of STARDUST's collector was aimed toward the comet; during the mission the other side of the collector was oriented away from the comet to collect interstellar dust.
"Westphal and Butterworth are targeted to receive the first grains of this precious cargo for projected measurements at the STXM at beamline 5.3.2," says Kilcoyne of the ALS.
Building an extraterrestrial database
Kilcoyne reports that over the past year or so the beamline has produced definitive measurements of the organics in more than two dozen meteorites, against which all future measurements on meteorites, interstellar dust grains, and pieces of comet will likely be referenced. "It's an incredible database," says SSL's Butterworth, an analytical chemist, of the database of meteorite organics that Cody is compiling with the 5.3.2 STXM.
Looking to STARDUST, she says, "No one has knowingly sampled a comet before, although it's possible some of the tens of thousands of meteorites we have came from comets. STARDUST will tell us what comets are made of, and the meteorite database will tell us if we've seen it before. As for interstellar dust grains, we've found microscopic particles embedded in meteorites, but STARDUST will give us the first-ever contemporary interstellar dust grains."
Many factors work together to determine the characteristic chemical signature of a specimen from space. One is temperature. Comets, for example, "formed cold and stayed cold; they were never part of a planet," says Cody. He hopes to find that Comet Wild 2 "sits way out" on his chart of how the solar system evolved chemically.
But what happens to a particle of dust or a piece of a comet when it slams into an aerogel tile at up to six kilometers a second? That's the velocity difference between the comet and the passing spacecraft, six times faster than a rifle bullet. Even though aerogel is 99 percent nothing, the remaining one percent of silicon froth brakes the particle fast; friction heats it so much the outer part melts. To understand these effects, the researchers are heating test particles up to 1,400 °C and measuring the chemical changes.
Just finding microscopic dust particles buried in each six-centimeter square of aerogel will be "like looking for 45 ants on a football field," says astrophysicist Westphal of SSL. No fully automated system of image analysis can do the job unaided, so he and Butterworth are recruiting amateur astronomers to visually help with the search for interplanetary dust particles using their home computers.
Once found, "each of these grains of dust is worth about $150 thousand," Westphal says. He's invented a way to extract them with a glass needle inserted along the particle track, a gentler method than existing laser-slicing techniques. SSL's extraction system will be duplicated at the Johnson Space Center in Houston, where the particles will eventually be stored for distribution to researchers around the world.
Anticipation runs high as CIW's Cody and his SSL colleagues prepare for the first samples of dust and cometary material from STARDUST. Cody says, "For a cosmochemist, being able to work with the material from STARDUST is the most privileged thing in the world."
Says Butterworth, "My preparations on 5.3.2 towards STARDUST are focused on challenging sample-prep issues finding, extracting, and preparing comet material containing just a few percent by weight of carbon for STXM. One reason the STXM microscope at beamline 5.3.2 will be important for STARDUST is its very high sensitivity in mapping small amounts of carbonaceous material."
"The beamline and STXM were designed explicitly to cover the carbon, nitrogen and oxygen edges in a single sweep, without any manual adjustments, and to operate in a stable, controlled, low-pressure helium environment that preserves the chemistry of these precious samples," says Kilcoyne. "This means the 5.3.2 STXM is ideally suited to cover the energy range of interest, and it uses a broadband source that does not need time-consuming tuning. Additionally, the dedicated instrumentation has led to a growing microscopy community, who enjoy all the advantages of being at the ALS."
"It's a fantastic time to be a planetary scientist," says Butterworth, who notes one of the reasons the STARDUST material is so precious: "These will be the first samples of an extraterrestrial body to be brought back to Earth since Apollo went to the moon."
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Let’s say you have a baby. Maybe you really do, maybe you don’t. But Dan Scolnic, a cosmologist at the University of Chicago, does have one, and perhaps that's why a hypothetical baby helps him explain the universe. If you take this baby to the doctor, that doctor will weigh and measure the baby, plot those points on a growth chart, and predict how big they’ll be later.
“We kind of have this same situation now with measuring the universe,” says Scolnic, who'll begin a professorship at Duke next month. Scientists have a great picture of what the universe was like as a baby. They also have one of what it looks like all grown up, today. And as with the doctor’s growth chart, a curve—following physics as we know it—should connect the two cleanly.
“You should be able to put in that universe’s baby picture, trace our standard cosmology, and see our universe today—if everything has gone right,” says Scolnic. But that’s not what is happening. “Something,” says Scolnic, “is not going right.”
Cosmologists aren’t sure what that something is, exactly. Maybe they're wrong in their measurement or analysis of the baby universe. Or of its present state.
Those are the boring options, though. “The other,” says Scolnic, “is that our standard model of cosmology isn’t correct.” In other words, the way humans think about the early years, maturation, and fate of the universe might be wrong somehow.
Over the past few years, scientists like Scolnic have investigated those first two hypothetical misunderstandings. They've whittled down their error bars, hardened their methods, re-analyzed the results of competitors and colleagues, and gathered sharper and bigger data. Nevertheless, the discrepancy persists.
Scolnic calls this moment “the era of tension cosmology.” Others just call it a crisis.
To those who don’t study the origin and evolution of the universe, that sounds like a bad thing. To cosmologists, it’s the opposite. To be wrong is to learn that the universe is more interesting than they thought. “We’re right on the cusp of this being the coolest thing ever,” says Scolnic.
One number has led us to said cusp. That number is called the Hubble constant, and it is the rate at which the universe is expanding today (not today like “Tuesday” but today like “in this cosmic moment”). The Hubble constant is an elusive beast, even for cosmology—a kind of white stag among white stags.
Astronomers have devised a few ways to estimate its value, and it is the conflict between their outcomes that’s causing the trouble. One method begins with the universe’s baby picture—a map of the so-called “cosmic microwave background,” or the remnant radiation from the Big Bang. From that picture, astronomers plug what they (think they) know about dark energy, dark matter, regular matter, and gravity into a model. Out pops a present state of the universe, and a prediction of the Hubble constant. Most recently, astronomers did this using cosmic microwave background data from the Planck telescope, a space-based observatory that was decommissioned in 2013.
Another method uses the “cosmic distance ladder.” Astronomers figure out how far away objects are, and how fast they’re moving even farther away, starting from here(ish) and building outward. They calculate the distances to nearby stars, and from them to more distant stars in other galaxies, and from them to supernovae in still-farther-off galaxies. They measure their movement away from us, providing another estimate of the Hubble constant.
Scolnic was part of a big team called SH0ES that used the ladder method. Its Hubble estimate disagrees with Planck's. Behold: the crisis. | 0.817273 | 3.65939 |
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.
Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.
Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.
- 1 Birth of a star
- 2 Mature stars
- 3 Stellar remnants
- 4 Models
- 5 See also
- 6 Further reading
- 7 External links
- 8 References
Birth of a star
Stellar evolution starts with the gravitational collapse of a giant molecular cloud. Typical giant molecular clouds are roughly 100 light-years (9.5×1014 km) across and contain up to 6,000,000 solar masses (1.2×1037 kg). As it collapses, a giant molecular cloud breaks into smaller and smaller pieces. In each of these fragments, the collapsing gas releases gravitational potential energy as heat. As its temperature and pressure increase, a fragment condenses into a rotating sphere of superhot gas known as a protostar.
A protostar continues to grow by accretion of gas and dust from the molecular cloud, becoming a pre-main-sequence star as it reaches its final mass. Further development is determined by its mass. (Mass is compared to the mass of the Sun: 1.0 M☉ (2.0×1030 kg) means 1 solar mass.)
Protostars are encompassed in dust, and are thus more readily visible at infrared wavelengths. Observations from the Wide-field Infrared Survey Explorer (WISE) have been especially important for unveiling numerous Galactic protostars and their parent star clusters.
Brown dwarfs and sub-stellar objects
Protostars with masses less than roughly 0.08 M☉ (1.6×1029 kg) never reach temperatures high enough for nuclear fusion of hydrogen to begin. These are known as brown dwarfs. The International Astronomical Union defines brown dwarfs as stars massive enough to fuse deuterium at some point in their lives (13 Jupiter masses, 2.5 × 1028 kg, or 0.0125 M☉). Objects smaller than 13 Jupiter masses are classified as sub-brown dwarfs (but if they orbit around another stellar object they are classified as planets). Both types, deuterium-burning and not, shine dimly and die away slowly, cooling gradually over hundreds of millions of years.
For a more massive protostar, the core temperature will eventually reach 10 million kelvin, initiating the proton-proton chain reaction and allowing hydrogen to fuse, first to deuterium and then to helium. In stars of slightly over 1 M☉ (2.0×1030 kg), the carbon–nitrogen–oxygen fusion reaction (CNO cycle) contributes a large portion of the energy generation. The onset of nuclear fusion leads relatively quickly to a hydrostatic equilibrium in which energy released by the core exerts a "radiation pressure" balancing the weight of the star's matter, preventing further gravitational collapse. The star thus evolves rapidly to a stable state, beginning the main-sequence phase of its evolution.
A new star will sit at a specific point on the main sequence of the Hertzsprung–Russell diagram, with the main-sequence spectral type depending upon the mass of the star. Small, relatively cold, low-mass red dwarfs fuse hydrogen slowly and will remain on the main sequence for hundreds of billions of years or longer, whereas massive, hot O-type stars will leave the main sequence after just a few million years. A mid-sized yellow dwarf star, like the Sun, will remain on the main sequence for about 10 billion years. The Sun is thought to be in the middle of its lifespan; thus, it is currently on the main sequence.
Eventually the core exhausts its supply of hydrogen and the star begins to evolve off of the main sequence. Without the outward pressure generated by the fusion of hydrogen to counteract the force of gravity the core contracts until either electron degeneracy becomes sufficient to oppose gravity or the core becomes hot enough (around 100 MK) for helium fusion to begin. Which of these happens first depends upon the star's mass.
What happens after a low-mass star ceases to produce energy through fusion has not been directly observed; the universe is thought to be around 13.8 billion years old, which is less time (by several orders of magnitude, in some cases) than it takes for fusion to cease in such stars.
Recent astrophysical models suggest that red dwarfs of 0.1 M☉ may stay on the main sequence for some six to twelve trillion years, gradually increasing in both temperature and luminosity, and take several hundred billion more to slowly collapse into a white dwarf. Such stars are fully convective and will not develop a degenerate helium core with hydrogen burning shells, or at least not until almost the whole star is helium, so they don't ever expand into a red giant.
Slightly more massive stars do expand into red giants, but their helium cores are not massive enough to ever reach the temperatures required for helium fusion so they never reach the tip of the red giant branch. When hydrogen shell burning finishes, these stars move directly off the red giant branch like a post AGB star, but at lower luminosity, to become a white dwarf. A star of about 0.5 M☉ will be able to reach temperatures high enough to fuse helium, and these "mid-sized" stars go on to further stages of evolution beyond the red giant branch.
Stars of roughly 0.5–10 M☉ become red giants, which are large non-main-sequence stars of stellar classification K or M. Red giants lie along the right edge of the Hertzsprung–Russell diagram due to their red color and large luminosity. Examples include Aldebaran in the constellation Taurus and Arcturus in the constellation of Boötes. Red giants all have inert cores with hydrogen-burning shells: concentric layers atop the core that are still fusing hydrogen into helium.
Mid-sized stars are red giants during two different phases of their post-main-sequence evolution: red-giant-branch stars, whose inert cores are made of helium, and asymptotic-giant-branch stars, whose inert cores are made of carbon. Asymptotic-giant-branch stars have helium-burning shells inside the hydrogen-burning shells, whereas red-giant-branch stars have hydrogen-burning shells only. In either case, the accelerated fusion in the hydrogen-containing layer immediately over the core causes the star to expand. This lifts the outer layers away from the core, reducing the gravitational pull on them, and they expand faster than the energy production increases. This causes the outer layers of the star to cool, which causes the star to become redder than it was on the main sequence.
The red-giant-branch phase of a star's life follows the main sequence. Initially, the cores of red-giant-branch stars collapse, as the internal pressure of the core is insufficient to balance gravity. This gravitational collapse releases energy, heating concentric shells immediately outside the inert helium core so that hydrogen fusion continues in these shells. The core of a red-giant-branch star of up to a few solar masses stops collapsing when it is dense enough to be supported by electron degeneracy pressure. Once this occurs, the core reaches hydrostatic equilibrium: the electron degeneracy pressure is sufficient to balance gravitational pressure. The core's gravity compresses the hydrogen in the layer immediately above it, causing it to fuse faster than hydrogen would fuse in a main-sequence star of the same mass. This in turn causes the star to become more luminous (from 1,000–10,000 times brighter) and expand; the degree of expansion outstrips the increase in luminosity, causing the effective temperature to decrease.
The expanding outer layers of the star are convective, with the material being mixed by turbulence from near the fusing regions up to the surface of the star. For all but the lowest-mass stars, the fused material has remained deep in the stellar interior prior to this point, so the convecting envelope makes fusion products visible at the star's surface for the first time. At this stage of evolution, the results are subtle, with the largest effects, alterations to the isotopes of hydrogen and helium, being unobservable. The effects of the CNO cycle appear at the surface, with lower 12C/13C ratios and altered proportions of carbon and nitrogen. These are detectable with spectroscopy and have been measured for many evolved stars.
As the hydrogen around the core is consumed, the core absorbs the resulting helium, causing it to contract further, which in turn causes the remaining hydrogen to fuse even faster. This eventually leads to ignition of helium fusion (which includes the triple-alpha process) in the core. In stars of more than approximately solar mass, it can take a billion years or more for the core to reach helium ignition temperatures.
When the temperature and pressure in the core become sufficient to ignite helium fusion, a helium flash will occur if the core is largely supported by electron degeneracy pressure (stars under 1.4 M☉). In more massive stars, the ignition of helium fusion occurs relatively quietly. Even if a helium flash does occur, the time of very rapid energy release (on the order of 108 Suns) is brief, so that the visible outer layers of the star are relatively undisturbed. The energy released by helium fusion causes the core to expand, so that hydrogen fusion in the overlying layers slows and total energy generation decreases. The star contracts, although not all the way to the main sequence, and it migrates to the horizontal branch on the Hertzsprung–Russell diagram, gradually shrinking in radius and increasing its surface temperature. Core helium flash stars evolve to the red end of the horizontal branch but do not migrate to higher temperatures before they gain a degenerate carbon-oxygen core and start helium shell burning. These stars are often observed as a red clump of stars in the colour-magnitude diagram of a cluster, hotter and less luminous than the red giants. Higher-mass stars with larger helium cores move along the horizontal branch to higher temperatures, some becoming unstable pulsating stars in the yellow instability strip (RR Lyrae variables), whereas some become even hotter and can form a blue tail or blue hook to the horizontal branch. The exact morphology of the horizontal branch depends on parameters such as metallicity, age, and helium content, but the exact details are still being modelled.
After a star has consumed the helium at the core, fusion continues in a shell around a hot core of carbon and oxygen. The star follows the asymptotic giant branch on the Hertzsprung–Russell diagram, paralleling the original red giant evolution, but with even faster energy generation (which lasts for a shorter time). Although helium is being burnt in a shell, the majority of the energy is produced by hydrogen burning in a shell closer to the surface of the star. Helium from these hydrogen burning shells drops towards the center of the star and periodically the energy output from the helium shell increases dramatically. This is known as a thermal pulse and they occur towards the end of the asymptotic-giant-branch phase, sometimes even into the post-asymptotic-giant-branch phase. Depending on mass and composition, there may be several to hundreds of thermal pulses.
There is a phase on the ascent of the asymptotic-giant-branch where a deep convective zone forms and can bring carbon from the core to the surface, This is known as the second dredge up, and in some stars there may even be a third dredge up. In this way a carbon star is formed, very cool and strongly reddened stars showing strong carbon lines in their spectra. A process known as hot bottom burning may convert carbon into oxygen and nitrogen before it can be dredged to the surface, and the interaction between these processes determines the observed luminosities and spectra of carbon stars in particular clusters.
Another well known class of asymptotic-giant-branch stars are the Mira variables, which pulsate with well-defined periods of tens to hundreds of days and large amplitudes up to about 10 magnitudes (in the visual, total luminosity changes by a much smaller amount). In more massive stars the stars become more luminous and the pulsation period is longer, leading to enhanced mass loss, and the stars become heavily obscured at visual wavelengths. These stars can be observed as OH/IR stars, pulsating in the infra-red and showing OH maser activity. These stars are clearly oxygen rich, in contrast to the carbon stars, but both must be produced by dredge ups.
These mid-range stars ultimately reach the tip of the asymptotic-giant-branch and run out of fuel for shell burning. They are not sufficiently massive to start full-scale carbon fusion, so they contract again, going through a period of post-asymptotic-giant-branch superwind to produce a planetary nebula with an extremely hot central star. The central star then cools to a white dwarf. The expelled gas is relatively rich in heavy elements created within the star and may be particularly oxygen or carbon enriched, depending on the type of the star. The gas builds up in an expanding shell called a circumstellar envelope and cools as it moves away from the star, allowing dust particles and molecules to form. With the high infrared energy input from the central star, ideal conditions are formed in these circumstellar envelopes for maser excitation.
It is possible for thermal pulses to be produced once post-asymptotic-giant-branch evolution has begun, producing a variety of unusual and poorly understood stars known as born-again asymptotic-giant-branch stars. These may result in extreme horizontal-branch stars (subdwarf B stars), hydrogen deficient post-asymptotic-giant-branch stars, variable planetary nebula central stars, and R Coronae Borealis variables.
In massive stars, the core is already large enough at the onset of the hydrogen burning shell that helium ignition will occur before electron degeneracy pressure has a chance to become prevalent. Thus, when these stars expand and cool, they do not brighten as much as lower-mass stars; however, they were much brighter than lower-mass stars to begin with, and are thus still brighter than the red giants formed from less massive stars. These stars are unlikely to survive as red supergiants; instead they will destroy themselves as type II supernovas.
Extremely massive stars (more than approximately 40 M☉), which are very luminous and thus have very rapid stellar winds, lose mass so rapidly due to radiation pressure that they tend to strip off their own envelopes before they can expand to become red supergiants, and thus retain extremely high surface temperatures (and blue-white color) from their main-sequence time onwards. The largest stars of the current generation are about 100-150 solar masses because the outer layers would be expelled by the extreme radiation. Although lower-mass stars normally do not burn off their outer layers so rapidly, they can likewise avoid becoming red giants or red supergiants if they are in binary systems close enough so that the companion star strips off the envelope as it expands, or if they rotate rapidly enough so that convection extends all the way from the core to the surface, resulting in the absence of a separate core and envelope due to thorough mixing.
The core grows hotter and denser as it gains material from fusion of hydrogen at the base of the envelope. In all massive stars, electron degeneracy pressure is insufficient to halt collapse by itself, so as each major element is consumed in the center, progressively heavier elements ignite, temporarily halting collapse. If the core of the star is not too massive (less than approximately 1.4 M☉, taking into account mass loss that has occurred by this time), it may then form a white dwarf (possibly surrounded by a planetary nebula) as described above for less massive stars, with the difference that the white dwarf is composed chiefly of oxygen, neon, and magnesium.
Above a certain mass (estimated at approximately 2.5 M☉ and whose star's progenitor was around 10 M☉), the core will reach the temperature (approximately 1.1 gigakelvins) at which neon partially breaks down to form oxygen and helium, the latter of which immediately fuses with some of the remaining neon to form magnesium; then oxygen fuses to form sulfur, silicon, and smaller amounts of other elements. Finally, the temperature gets high enough that any nucleus can be partially broken down, most commonly releasing an alpha particle (helium nucleus) which immediately fuses with another nucleus, so that several nuclei are effectively rearranged into a smaller number of heavier nuclei, with net release of energy because the addition of fragments to nuclei exceeds the energy required to break them off the parent nuclei.
A star with a core mass too great to form a white dwarf but insufficient to achieve sustained conversion of neon to oxygen and magnesium, will undergo core collapse (due to electron capture) before achieving fusion of the heavier elements. Both heating and cooling caused by electron capture onto minor constituent elements (such as aluminum and sodium) prior to collapse may have a significant impact on total energy generation within the star shortly before collapse. This may produce a noticeable effect on the abundance of elements and isotopes ejected in the subsequent supernova.
Once the nucleosynthesis process arrives at iron-56, the continuation of this process consumes energy (the addition of fragments to nuclei releases less energy than required to break them off the parent nuclei). If the mass of the core exceeds the Chandrasekhar limit, electron degeneracy pressure will be unable to support its weight against the force of gravity, and the core will undergo sudden, catastrophic collapse to form a neutron star or (in the case of cores that exceed the Tolman-Oppenheimer-Volkoff limit), a black hole. Through a process that is not completely understood, some of the gravitational potential energy released by this core collapse is converted into a Type Ib, Type Ic, or Type II supernova. It is known that the core collapse produces a massive surge of neutrinos, as observed with supernova SN 1987A. The extremely energetic neutrinos fragment some nuclei; some of their energy is consumed in releasing nucleons, including neutrons, and some of their energy is transformed into heat and kinetic energy, thus augmenting the shock wave started by rebound of some of the infalling material from the collapse of the core. Electron capture in very dense parts of the infalling matter may produce additional neutrons. Because some of the rebounding matter is bombarded by the neutrons, some of its nuclei capture them, creating a spectrum of heavier-than-iron material including the radioactive elements up to (and likely beyond) uranium. Although non-exploding red giants can produce significant quantities of elements heavier than iron using neutrons released in side reactions of earlier nuclear reactions, the abundance of elements heavier than iron (and in particular, of certain isotopes of elements that have multiple stable or long-lived isotopes) produced in such reactions is quite different from that produced in a supernova. Neither abundance alone matches that found in the Solar System, so both supernovae and ejection of elements from red giants are required to explain the observed abundance of heavy elements and isotopes thereof.
The energy transferred from collapse of the core to rebounding material not only generates heavy elements, but provides for their acceleration well beyond escape velocity, thus causing a Type Ib, Type Ic, or Type II supernova. Note that current understanding of this energy transfer is still not satisfactory; although current computer models of Type Ib, Type Ic, and Type II supernovae account for part of the energy transfer, they are not able to account for enough energy transfer to produce the observed ejection of material.
Some evidence gained from analysis of the mass and orbital parameters of binary neutron stars (which require two such supernovae) hints that the collapse of an oxygen-neon-magnesium core may produce a supernova that differs observably (in ways other than size) from a supernova produced by the collapse of an iron core.
The most massive stars that exist today may be completely destroyed by a supernova with an energy greatly exceeding its gravitational binding energy. This rare event, caused by pair-instability, leaves behind no black hole remnant. In the past history of the universe, some stars were even larger than the largest that exists today, and they would immediately collapse into a black hole at the end of their lives, due to photodisintegration.
After a star has burned out its fuel supply, its remnants can take one of three forms, depending on the mass during its lifetime.
White and black dwarfs
For a star of 1 M☉, the resulting white dwarf is of about 0.6 M☉, compressed into approximately the volume of the Earth. White dwarfs are stable because the inward pull of gravity is balanced by the degeneracy pressure of the star's electrons, a consequence of the Pauli exclusion principle. Electron degeneracy pressure provides a rather soft limit against further compression; therefore, for a given chemical composition, white dwarfs of higher mass have a smaller volume. With no fuel left to burn, the star radiates its remaining heat into space for billions of years.
A white dwarf is very hot when it first forms, more than 100,000 K at the surface and even hotter in its interior. It is so hot that a lot of its energy is lost in the form of neutrinos for the first 10 million years of its existence, but will have lost most of its energy after a billion years.
The chemical composition of the white dwarf depends upon its mass. A star of a few solar masses will ignite carbon fusion to form magnesium, neon, and smaller amounts of other elements, resulting in a white dwarf composed chiefly of oxygen, neon, and magnesium, provided that it can lose enough mass to get below the Chandrasekhar limit (see below), and provided that the ignition of carbon is not so violent as to blow the star apart in a supernova. A star of mass on the order of magnitude of the Sun will be unable to ignite carbon fusion, and will produce a white dwarf composed chiefly of carbon and oxygen, and of mass too low to collapse unless matter is added to it later (see below). A star of less than about half the mass of the Sun will be unable to ignite helium fusion (as noted earlier), and will produce a white dwarf composed chiefly of helium.
In the end, all that remains is a cold dark mass sometimes called a black dwarf. However, the universe is not old enough for any black dwarfs to exist yet.
If the white dwarf's mass increases above the Chandrasekhar limit, which is 1.4 M☉ for a white dwarf composed chiefly of carbon, oxygen, neon, and/or magnesium, then electron degeneracy pressure fails due to electron capture and the star collapses. Depending upon the chemical composition and pre-collapse temperature in the center, this will lead either to collapse into a neutron star or runaway ignition of carbon and oxygen. Heavier elements favor continued core collapse, because they require a higher temperature to ignite, because electron capture onto these elements and their fusion products is easier; higher core temperatures favor runaway nuclear reaction, which halts core collapse and leads to a Type Ia supernova. These supernovae may be many times brighter than the Type II supernova marking the death of a massive star, even though the latter has the greater total energy release. This inability to collapse means that no white dwarf more massive than approximately 1.4 M☉ can exist (with a possible minor exception for very rapidly spinning white dwarfs, whose centrifugal force due to rotation partially counteracts the weight of their matter). Mass transfer in a binary system may cause an initially stable white dwarf to surpass the Chandrasekhar limit.
If a white dwarf forms a close binary system with another star, hydrogen from the larger companion may accrete around and onto a white dwarf until it gets hot enough to fuse in a runaway reaction at its surface, although the white dwarf remains below the Chandrasekhar limit. Such an explosion is termed a nova.
When a stellar core collapses, the pressure causes electron capture, thus converting the great majority of the protons into neutrons. The electromagnetic forces keeping separate nuclei apart are gone (proportionally, if nuclei were the size of dust mites, atoms would be as large as football stadiums), and most of the core of the star becomes a dense ball of contiguous neutrons (in some ways like a giant atomic nucleus), with a thin overlying layer of degenerate matter (chiefly iron unless matter of different composition is added later). The neutrons resist further compression by the Pauli Exclusion Principle, in a way analogous to electron degeneracy pressure, but stronger.
These stars, known as neutron stars, are extremely small—on the order of radius 10 km, no bigger than the size of a large city—and are phenomenally dense. Their period of rotation shortens dramatically as the stars shrink (due to conservation of angular momentum); observed rotational periods of neutron stars range from about 1.5 milliseconds (over 600 revolutions per second) to several seconds. When these rapidly rotating stars' magnetic poles are aligned with the Earth, we detect a pulse of radiation each revolution. Such neutron stars are called pulsars, and were the first neutron stars to be discovered. Though electromagnetic radiation detected from pulsars is most often in the form of radio waves, pulsars have also been detected at visible, X-ray, and gamma ray wavelengths.
If the mass of the stellar remnant is high enough, the neutron degeneracy pressure will be insufficient to prevent collapse below the Schwarzschild radius. The stellar remnant thus becomes a black hole. The mass at which this occurs is not known with certainty, but is currently estimated at between 2 and 3 solar masses.
Black holes are predicted by the theory of general relativity. According to classical general relativity, no matter or information can flow from the interior of a black hole to an outside observer, although quantum effects may allow deviations from this strict rule. The existence of black holes in the universe is well supported, both theoretically and by astronomical observation.
Because the core-collapse supernova mechanism itself is imperfectly understood, it is still not known whether it is possible for a star to collapse directly to a black hole without producing a visible supernova, or whether some supernovae initially form unstable neutron stars which then collapse into black holes; the exact relation between the initial mass of the star and the final remnant is also not completely certain. Resolution of these uncertainties requires the analysis of more supernovae and supernova remnants.
A stellar evolutionary model is a mathematical model that can be used to compute the evolutionary phases of a star from its formation until it becomes a remnant. The mass and chemical composition of the star are used as the inputs, and the luminosity and surface temperature are the only constraints. The model formulae are based upon the physical understanding of the star, usually under the assumption of hydrostatic equilibrium. Extensive computer calculations are then run to determine the changing state of the star over time, yielding a table of data that can be used to determine the evolutionary track of the star across the Hertzsprung–Russell diagram, along with other evolving properties. Accurate models can be used to estimate the current age of a star by comparing its physical properties with those of stars along a matching evolutionary track.
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Cascading Material Pours Onto a Young Star
20 April 2011
AUSTIN, Texas — Astronomer Joel Green of The University of Texas at Austin has been following a rare massive flare from a nascent star similar to the early Sun using the European Space Agency's infrared Herschel Space Observatory and a cadre of other telescopes. Green has found that this protostar, called HBC 722, is situated in a tangled web of gas and protostars tightly packed into a small area. Green's research is published in today's issue of The Astrophysical
HBC 722 lies 2,000 light-years away in the "Gulf of Mexico" region of the North America Nebula (NGC 7000), in the constellation Cygnus, the swan. In early 2009, it appeared to be an ordinary young star in a cloud of similarly young stars. Like most stars less than a few million years old, HBC 722 is surrounded by a disk of gas and dust, perhaps beginning to form a planetary system.
It began to brighten, slowly at first, increasing dramatically during the summer of 2010. By late September 2010, it was 20 times brighter than it had been the year before. Since that time, it has slowly begun to settle back down.
The event provided astronomers a unique opportunity to observe the evolution of a flaring young star, an event observed on average only once per decade. These objects are called FU Orionis (FUor) objects, after the prototype found in the constellation Orion in 1936. FU Orionis-type stars are natural laboratories to test the effects of heating on the chemistry and physics of disks and their surrounding envelopes.
The HBC 722 flare is the first such event discovered in more than 30 years, and likely the only one that will occur during the lifetime of the Herschel Space Observatory. Green received permission to view HBC 722 with Herschel as a "target of opportunity" quickly after it was discovered. Herschel turned its PACS, SPIRE, and HIFI instruments on this eruption of light from a young star in the midst of a volatile stellar nursery to help astronomers piece together the chemistry of this active stellar region.
The quick reaction of Herschel and other observatories has allowed astronomers to observe its behavior from early stages, within a few months of its brightening episode. It has been dimming faster than other FUor objects, which are still bright decades after their eruption.
What happened to HBC 722 to cause this flare? It is likely that a large amount of material built up in its surrounding disk, and suddenly reached a critical point where it overflowed and poured onto the star at a rate twenty times greater than usual, releasing vast amounts of heat and ejecting excess material and momentum into the surrounding cloud. The consequences of this
event have yet to manifest fully.
“With Herschel we could see the effect the outburst has on the nearby gas and dust,” Green said. "We want to see if the sudden change in the star's brightness affects its environment and compare it to older flares that have had longer to decay from their outbursts. We also want to compare to stars that are not currently in outburst."
Flares of this magnitude are rare because they are short-lived compared to the relatively quiet states that characterize most young stars. Outbursts are often considered to be an important part of the process by which a young star acquires its final mass, through a small trickle of material punctuated by short, repeated floods.
Herschel revealed the busy environment of HBC 722, comprised of large amounts of molecular material such as carbon monoxide and water, thought to be heated by ultraviolet light from the evolving stars in the vicinity. In Herschel's infrared view, the flare of HBC 722 may highlight vast flows of material from nearby colder and even younger stars. In the future the increased radiation from HBC 722 may further heat the gas in the vicinity as it flows past.
Coordinating with observations by numerous ground-based telescopes, astronomers are looking for signs of the shockwaves that should have been launched from HBC 722. Green will view HBC 722 with Herschel again in June and expects by that time he might observe evidence of the jet that has likely been building since the flare began, but so far has been too small to detect.
A wealth of data on HBC 722 existed before the flare. Green's current data from Herschel and several other ground and space-based telescopes, together with planned follow-up, will make this will be the most-observed FUor object yet. This data timeline will help astronomers better understand the cause of such flares, which are currently thought to originate when large amounts of gas fall from the circumstellar disk onto the protostar.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
— END —
Dr. Joel Green
The Univeristy of Texas at Austin | 0.867304 | 3.868685 |
An asteroid has been ripped to shreds and vaporised after straying too close to a hot white dwarf star, observations suggest. The asteroid was probably flung towards the white dwarf by the gravity of one or more unseen planets, astronomers say.
Stars like the Sun become bloated red giants when they age, then gradually blow off their outer layers until only a dense, inactive core called a white dwarf is left.
Scientists are interested in signs of planets and asteroids around these stellar embers because they offer a preview of what will eventually happen to solar systems like our own.
Astronomers have previously seen other white dwarfs orbited by dusty debris discs and with unusually large amounts of metal on their surfaces, suggesting they are absorbing asteroids that have wandered too close to them and been torn apart (see Rocky planets may circle many white dwarfs).
Now, researchers led by Boris Gaensicke of the University of Warwick, UK, have found the best evidence yet of an asteroid being consumed by a white dwarf. The evidence comes in the form of a hot ring of metallic vapour around a white dwarf called SDSS 1228+1040.
The researchers found signs of the disc in light spectra from the white dwarf acquired by the Sloan Digital Sky Survey’s 2.5-metre telescope at Apache Point, New Mexico, US, the 4.2-metre William Herschel Telescope in the Canary Islands, and by Caltech’s orbiting Galaxy Evolution Explorer (GALEX).
The spectra indicate that a disc containing calcium, magnesium, and iron gas is orbiting the white dwarf at a distance 100 times closer than Mercury’s orbit around the Sun. At this distance, intense radiation from the white dwarf heats the gas to 5000 Kelvin.
The spectra also show that the white dwarf’s atmosphere is enriched in magnesium. That indicates material from the disc is falling onto the star, since the star’s own surface gravity is so great that its own heavy elements should have already sunk towards its centre – and out of sight.
To explain all of this, Gaensicke’s team proposes that an asteroid was flung towards the white dwarf and was ripped apart by the white dwarf’s gravity, with the resulting metal-rich dust heated until it was vaporised.
The location of the disc supports this idea, according to previous calculations, says team member Tom Marsh, also of the University of Warwick. “It turns out that asteroids should get torn up at this sort of distance,” he told New Scientist.
The destruction of the asteroid also hints that unseen planets are lurking in this system. In the star’s previous red giant phase, it should have bloated up so much that it purged everything out to the distance of Mars in our solar system.
So the very fact that the asteroid is so close to the white dwarf now requires it to have been nudged there by something in the outer regions of that solar system. The researchers suggest that one or more planets survived the red giant phase and gravitationally flung the asteroid towards the white dwarf.
Benjamin Zuckerman of the University of California in Los Angeles, US, who has previously published evidence with colleagues about dusty discs around white dwarfs, says the new results are the clearest evidence yet of an asteroid or other object thrown towards a white dwarf and destroyed.
“It shows that likely many planets and asteroids can survive the red giant and planetary nebulae phases of stellar evolution,” he told New Scientist.
Ted von Hippel of the University of Texas in Austin, US, who has also researched white dwarf discs, agrees that the new evidence makes a good case for the destruction of an asteroid, or perhaps even a rocky planet, given the uncertainty in the original object’s mass. The gravitational influence of one or more unseen planets is a likely explanation for this, he says.
It is also possible that the disc is just material shed by the star in the late part of its life, although the lack of hydrogen in the disc would be difficult to explain in this case, he says.
If the disrupted asteroid or planet idea is right, it will shed new light on the fate of planetary systems like our own, he says.
“There’s been very little work about what would happen to planetary systems when a star goes to red giant and white dwarf,” he told New Scientist. “This is giving us insight into the late stages of a planetary system – you could say planetary system destruction,” he says.
Journal reference: Science (vol 314, p 1908) | 0.897796 | 3.894153 |
Over the years, researchers have taken myriad observations of black holes and their environs, but now ESO’s Very Large Telescope Interferometer is giving us the most detailed look of the dust around a black hole at the center of an active galaxy ever obtained. Originally expected to be contained within the ring-shaped torus around the black hole, the observation held a surprise as astronomers discovered that a significant amount of the dust was located both above and below the torus. What can this mean? According to the latest findings and contrary to popular theory, it is possible the dust is being evacuated from the region as a cool wind.
For the last two decades, astronomers have discovered that nearly all galaxies harbor a black hole at their hearts. In many cases, these monsters increase in size by accreting matter from the immediate vicinity. This, in turn, is responsible for the creation of active galactic nuclei (AGN), one of the most energetic objects in the Universe. Surrounding the super-luminous giants are rings of cosmic dust which originate from space – drawn in like water swirling down a dark drain. According to theory, the intense infrared radiation exerted by AGN must have originated from these dusty eddies.
Thanks to the powerful eye of the Very Large Telescope Interferometer (VLTI) at ESO’s Paranal Observatory in Chile, astronomers have now seen something new in a nearby active galaxy cataloged as NGC 3783. While they observed the expected hot dust clocking in at some 700 to 1000 degrees Celsius, what they also observed confounded them… Huge amounts of cooler dust both above and below the main torus.
As Sebastian Hönig (University of California Santa Barbara, USA and Christian-Albrechts-Universität zu Kiel, Germany), lead author of the paper presenting the new results, explains, “This is the first time we’ve been able to combine detailed mid-infrared observations of the cool, room-temperature dust around an AGN with similarly detailed observations of the very hot dust. This also represents the largest set of infrared interferometry for an AGN published yet.”
Is this a black hole teething ring? From their observations, the researchers suspect the newly-discovered dust is flowing outward from the central black hole. This means the wind most likely plays a critical part in the tangled relationship of both the black hole and its surroundings. Apparently the black hole pulls immediate material into it, but the incredible amount of radiation this produces also seems to be pushing it away. Scientists are far from clear as to how these two processes work together, but the discovery of this dusty wind could lead to a better understanding of their evolution.
To get the resolution needed to study the core area of NGC 3783, astronomers needed to use the combined power of the Unit Telescopes of ESO’s Very Large Telescope. Through this union, an interferometer is created – one capable of “seeing” with the equivalent of a 130-meter telescope.
Another team member, Gerd Weigelt (Max-Planck-Institut für Radioastronomie, Bonn, Germany), explains, “By combining the world-class sensitivity of the large mirrors of the VLT with interferometry we are able to collect enough light to observe faint objects. This lets us study a region as small as the distance from our Sun to its closest neighbouring star, in a galaxy tens of millions of light-years away. No other optical or infrared system in the world is currently capable of this.”
What do these new observations mean to the world of astronomy? It might very well change the pattern of how we currently understand AGN. With proof that dust is being expelled by intense radiation, new models must be created – models which include this recent information of how dust can be distributed.
Hönig concludes, “I am now really looking forward to MATISSE, which will allow us to combine all four VLT Unit Telescopes at once and observe simultaneously in the near- and mid-infrared — giving us much more detailed data.” MATISSE, a second generation instrument for the VLTI, is currently under construction.
Original Story Source: ESO News Release. | 0.887059 | 4.043262 |
By the end of this section, you will be able to:
- Describe how radio waves from space are detected
- Identify the world’s largest radio telescopes
- Define the technique of interferometry and discuss the benefits of interferometers over single-dish telescopes
In addition to visible and infrared radiation, radio waves from astronomical objects can also be detected from the surface of Earth. In the early 1930s, Karl G. Jansky, an engineer at Bell Telephone Laboratories, was experimenting with antennas for long-range radio communication when he encountered some mysterious static—radio radiation coming from an unknown source (Figure 1).
He discovered that this radiation came in strongest about four minutes earlier on each successive day and correctly concluded that since Earth’s sidereal rotation period (how long it takes us to rotate relative to the stars) is four minutes shorter than a solar day, the radiation must be originating from some region fixed on the celestial sphere. Subsequent investigation showed that the source of this radiation was part of the Milky Way Galaxy; Jansky had discovered the first source of cosmic radio waves.
In 1936, Grote Reber, who was an amateur astronomer interested in radio communications, used galvanized iron and wood to build the first antenna specifically designed to receive cosmic radio waves. Over the years, Reber built several such antennas and used them to carry out pioneering surveys of the sky for celestial radio sources; he remained active in radio astronomy for more than 30 years. During the first decade, he worked practically alone because professional astronomers had not yet recognized the vast potential of radio astronomy.
Detection of Radio Energy from Space
It is important to understand that radio waves cannot be “heard”: they are not the sound waves you hear coming out of the radio receiver in your home or car. Like light, radio waves are a form of electromagnetic radiation, but unlike light, we cannot detect them with our senses—we must rely on electronic equipment to pick them up. In commercial radio broadcasting, we encode sound information (music or a newscaster’s voice) into radio waves. These must be decoded at the other end and then turned back into sound by speakers or headphones.
The radio waves we receive from space do not, of course, have music or other program information encoded in them. If cosmic radio signals were translated into sound, they would sound like the static you hear when scanning between stations. Nevertheless, there is information in the radio waves we receive—information that can tell us about the chemistry and physical conditions of the sources of the waves.
Just as vibrating charged particles can produce electromagnetic waves (see the Radiation and Spectra chapter), electromagnetic waves can make charged particles move back and forth. Radio waves can produce a current in conductors of electricity such as metals. An antenna is such a conductor: it intercepts radio waves, which create a feeble current in it. The current is then amplified in a radio receiver until it is strong enough to measure or record. Like your television or radio, receivers can be tuned to select a single frequency (channel). In astronomy, however, it is more common to use sophisticated data-processing techniques that allow thousands of separate frequency bands to be detected simultaneously. Thus, the astronomical radio receiver operates much like a spectrometer on a visible-light or infrared telescope, providing information about how much radiation we receive at each wavelength or frequency. After computer processing, the radio signals are recorded on magnetic disks for further analysis.
Radio waves are reflected by conducting surfaces, just as light is reflected from a shiny metallic surface, and according to the same laws of optics. A radio-reflecting telescope consists of a concave metal reflector (called a dish), analogous to a telescope mirror. The radio waves collected by the dish are reflected to a focus, where they can then be directed to a receiver and analyzed. Because humans are such visual creatures, radio astronomers often construct a pictorial representation of the radio sources they observe. Figure 2 shows such a radio image of a distant galaxy, where radio telescopes reveal vast jets and complicated regions of radio emissions that are completely invisible in photographs taken with light.
Radio astronomy is a young field compared with visible-light astronomy, but it has experienced tremendous growth in recent decades. The world’s largest radio reflectors that can be pointed to any direction in the sky have apertures of 100 meters. One of these has been built at the US National Radio Astronomy Observatory in West Virginia (Figure 3). Table 1 lists some of the major radio telescopes of the world.
|Table 1. Major Radio Observatories of the World|
|Individual Radio Dishes|
|Arecibo Observatory||Arecibo, Puerto Rico||305-m fixed dish||www.naic.edu|
|Green Bank Telescope (GBT)||Green Bank, WV||110 × 100-m steerable dish||www.science.nrao.edu/facilities/gbt|
|Effelsberg 100-m Telescope||Bonn, Germany||100-m steerable dish||www.mpifr-bonn.mpg.de/en/effelsberg|
|Lovell Telescope||Manchester, England||76-m steerable dish||www.jb.man.ac.uk/aboutus/lovell|
|Canberra Deep Space Communication Complex (CDSCC)||Tidbinbilla, Australia||70-m steerable dish||www.cdscc.nasa.gov|
|Goldstone Deep Space Communications Complex (GDSCC)||Barstow, CA||70-m steerable dish||www.gdscc.nasa.gov|
|Parkes Observatory||Parkes, Australia||64-m steerable dish||www.parkes.atnf.csiro.au|
|Arrays of Radio Dishes|
|Square Kilometre Array (SKA)||South Africa and Western Australia||Thousands of dishes, km2 collecting area, partial array in 2020||www.skatelescope.org|
|Atacama Large Millimeter/submillimeter Array (ALMA)||Atacama desert, Northern Chile||66 7-m and 12-m dishes||www.almaobservatory.org|
|Very Large Array (VLA)||Socorro, New Mexico||27-element array of 25-m dishes (36-km baseline)||www.science.nrao.edu/facilities/vla|
|Westerbork Synthesis Radio Telescope (WSRT)||Westerbork, the Netherlands||12-element array of 25-m dishes (1.6-km baseline)||www.astron.nl/radio-observatory/public/public-0|
|Very Long Baseline Array (VLBA)||Ten US sites, HI to the Virgin Islands||10-element array of 25-m dishes (9000 km baseline)||www.science.nrao.edu/facilities/vlba|
|Australia Telescope Compact Array (ATCA)||Several sites in Australia||8-element array (seven 22-m dishes plus Parkes 64 m)||www.narrabri.atnf.csiro.au|
|Multi-Element Radio Linked Interferometer Network (MERLIN)||Cambridge, England, and other British sites||Network of seven dishes (the largest is 32 m)||www.e-merlin.ac.uk|
|IRAM||Granada, Spain||30-m steerable mm-wave dish||www.iram-institute.org|
|James Clerk Maxwell Telescope (JCMT)||Mauna Kea, HI||15-m steerable mm-wave dish||www.eaobservatory.org/jcmt|
|Nobeyama Radio Observatory (NRO)||Minamimaki, Japan||6-element array of 10-m wave dishes||www.nro.nao.ac.jp/en|
|Hat Creek Radio Observatory (HCRO)||Cassel, CA||6-element array of 5-m wave dishes||www.sri.com/research-development/specialized-facilities/hat-creek-radio-observatory|
As we discussed earlier, a telescope’s ability to show us fine detail (its resolution) depends upon its aperture, but it also depends upon the wavelength of the radiation that the telescope is gathering. The longer the waves, the harder it is to resolve fine detail in the images or maps we make. Because radio waves have such long wavelengths, they present tremendous challenges for astronomers who need good resolution. In fact, even the largest radio dishes on Earth, operating alone, cannot make out as much detail as the typical small visible-light telescope used in a college astronomy lab. To overcome this difficulty, radio astronomers have learned to sharpen their images by linking two or more radio telescopes together electronically. Two or more telescopes linked together in this way are called an interferometer.
“Interferometer” may seem like a strange term because the telescopes in an interferometer work cooperatively; they don’t “interfere” with each other. Interference, however, is a technical term for the way that multiple waves interact with each other when they arrive in our instruments, and this interaction allows us to coax more detail out of our observations. The resolution of an interferometer depends upon the separation of the telescopes, not upon their individual apertures. Two telescopes separated by 1 kilometer provide the same resolution as would a single dish 1 kilometer across (although they are not, of course, able to collect as much radiation as a radio-wave bucket that is 1 kilometer across).
To get even better resolution, astronomers combine a large number of radio dishes into an interferometer array. In effect, such an array works like a large number of two-dish interferometers, all observing the same part of the sky together. Computer processing of the results permits the reconstruction of a high-resolution radio image. The most extensive such instrument in the United States is the National Radio Astronomy Observatory’s Very Large Array (VLA) near Socorro, New Mexico. It consists of 27 movable radio telescopes (on railroad tracks), each having an aperture of 25 meters, spread over a total span of about 36 kilometers. By electronically combining the signals from all of its individual telescopes, this array permits the radio astronomer to make pictures of the sky at radio wavelengths comparable to those obtained with a visible-light telescope, with a resolution of about 1 arcsecond.
The Atacama Large Millimeter/submillimeter array (ALMA) in the Atacama Desert of Northern Chile (Figure 4), at an altitude of 16,400 feet, consists of 12 7-meter and 54 12-meter telescopes, and can achieve baselines up to 16 kilometers. Since it became operational in 2013, it has made observations at resolutions down to 6 milliarcseconds (0.006 arcseconds), a remarkable achievement for radio astronomy.
Initially, the size of interferometer arrays was limited by the requirement that all of the dishes be physically wired together. The maximum dimensions of the array were thus only a few tens of kilometers. However, larger interferometer separations can be achieved if the telescopes do not require a physical connection. Astronomers, with the use of current technology and computing power, have learned to time the arrival of electromagnetic waves coming from space very precisely at each telescope and combine the data later. If the telescopes are as far apart as California and Australia, or as West Virginia and Crimea in Ukraine, the resulting resolution far surpasses that of visible-light telescopes.
The United States operates the Very Long Baseline Array (VLBA), made up of 10 individual telescopes stretching from the Virgin Islands to Hawaii (Figure 5). The VLBA, completed in 1993, can form astronomical images with a resolution of 0.0001 arcseconds, permitting features as small as 10 astronomical units (AU) to be distinguished at the center of our Galaxy.
Recent advances in technology have also made it possible to do interferometry at visible-light and infrared wavelengths. At the beginning of the twenty-first century, three observatories with multiple telescopes each began using their dishes as interferometers, combining their light to obtain a much greater resolution. In addition, a dedicated interferometric array was built on Mt. Wilson in California. Just as in radio arrays, these observations allow astronomers to make out more detail than a single telescope could provide.
|Table 2. Visible-Light Interferometers|
|Longest Baseline (m)||Telescope Name||Location||Mirrors||Status|
|400||CHARA Array (Center for High Angular Resolution Astronomy)||Mount Wilson, CA||Six 1-m telescopes||Operational since 2004|
|200||Very Large Telescope||Cerro Paranal, Chile||Four 8.2-m telescopes||Completed 2000|
|85||Keck I and II telescopes||Mauna Kea, HI||Two 10-m telescopes||Operated from 2001 to 2012|
|22.8||Large Binocular Telescope||Mount Graham, AZ||Two 8.4-m telescopes||First light 2004|
Radar is the technique of transmitting radio waves to an object in our solar system and then detecting the radio radiation that the object reflects back. The time required for the round trip can be measured electronically with great precision. Because we know the speed at which radio waves travel (the speed of light), we can determine the distance to the object or a particular feature on its surface (such as a mountain).
Radar observations have been used to determine the distances to planets and how fast things are moving in the solar system (using the Doppler effect, discussed in the Radiation and Spectra chapter). Radar waves have played important roles in navigating spacecraft throughout the solar system. In addition, as will be discussed in later chapters, radar observations have determined the rotation periods of Venus and Mercury, probed tiny Earth-approaching asteroids, and allowed us to investigate the mountains and valleys on the surfaces of Mercury, Venus, Mars, and the large moons of Jupiter.
Any radio dish can be used as a radar telescope if it is equipped with a powerful transmitter as well as a receiver. The most spectacular facility in the world for radar astronomy is the 1000-foot (305-meter) telescope at Arecibo in Puerto Rico (Figure 6). The Arecibo telescope is too large to be pointed directly at different parts of the sky. Instead, it is constructed in a huge natural “bowl” (more than a mere dish) formed by several hills, and it is lined with reflecting metal panels. A limited ability to track astronomical sources is achieved by moving the receiver system, which is suspended on cables 100 meters above the surface of the bowl. An even larger (500-meter) radar telescope is currently under construction. It is the Five-hundred-meter Aperture Spherical Telescope (FAST) in China and is expected to be completed in 2016.
In the 1930s, radio astronomy was pioneered by Karl G. Jansky and Grote Reber. A radio telescope is basically a radio antenna (often a large, curved dish) connected to a receiver. Significantly enhanced resolution can be obtained with interferometers, including interferometer arrays like the 27-element VLA and the 66-element ALMA. Expanding to very long baseline interferometers, radio astronomers can achieve resolutions as precise as 0.0001 arcsecond. Radar astronomy involves transmitting as well as receiving. The largest radar telescope currently in operation is a 305-meter bowl at Arecibo.
interference: process in which waves mix together such that their crests and troughs can alternately reinforce and cancel one another
interferometer: instrument that combines electromagnetic radiation from one or more telescopes to obtain a resolution equivalent to what would be obtained with a single telescope with a diameter equal to the baseline separating the individual separate telescopes
interferometer array: combination of multiple radio dishes to, in effect, work like a large number of two-dish interferometers
radar: technique of transmitting radio waves to an object and then detecting the radiation that the object reflects back to the transmitter; used to measure the distance to, and motion of, a target object or to form images of it | 0.84408 | 4.073406 |
Rosetta's comet 67P/Churyumov-Gerasimenko sheds its dusty mantle to reveal its icy nature
Publication date: 17 November 2016
Authors: Fornasier, S., et al.
The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko from large heliocentric distances to its perihelion passage and beyond. We trace the seasonal and diurnal evolution of the colors of the 67P nucleus, finding changes driven by sublimation and recondensation of water ice. The whole nucleus became relatively bluer near perihelion, as increasing activity removed the surface dust, implying that water ice is widespread underneath the surface. We identified large (1500 m2) ice-rich patches appearing and then vanishing in about 10 days, indicating small-scale heterogeneities on the nucleus. Thin frosts sublimating in a few minutes are observed close to receding shadows, and rapid variations in color seen on extended areas close to the terminator. These cyclic processes are widespread and lead to continuously, slightly varying surface properties.Link to publication | 0.804136 | 3.3098 |
By Staff Contributor
Magnetoreception refers to the ability of an organism to perceive magnetic fields. Several animals use it to find their way over long distances by aligning themselves with the magnetic field of the Earth. Just think of the pigeons.
MagnetoreceptionSea turtles, honeybees, spiny lobsters, dolphins, migratory birds, and more all have a magnetic compass. It allows them to use the information implied into earth’s magnetic fields. However, we know just a little beyond that. What remains up for speculation is how they sense it and put it to use. What kind of information are they getting from it? For all that we know, these magnetic fields could give much more information than simple navigation for individual species.
Magnetoreception and HumansJoe Kirschvink, a geophysicist at the California Institute of Technology, is the one that is currently testing humans for a magnetic sense. He says that “It is just a part of our evolutionary history and Magnetoreception may also be the primal sense.”
There was a recent study, published by Kirschvink in the journal Nature Communications, which suggested that a protein in the human retina, when placed into fruit flies, can detect magnetic fields. The research claims that it can serve as a magnetic sensor. However, it is still unknown whether or not humans can use it in this way.
Steven Reppert, the researcher at the University Massachusetts Medical School, told LiveScience :
“It poses the question, ‘maybe we should rethink about this sixth sense. It is also thought to be very important for how animals migrate. Perhaps, this protein is also fulfilling an essential function for sensing magnetic fields in humans.”
In one of the recent experiments, Kirschvink was passing a rotating magnetic field through study participants. During the test, he measured participant’s brainwaves. He discovered that during the counterclockwise rotation of the magnetic field, some neurons responded to the change of the rotation. The response generated a spike in brain’s electrical activity. This result suggests a probable magnetic sense in humans.
The Next StepThe experiment raised multiple questions. For instance, was this neural activity evidence of a magnetic-sense, or it was something else? Even when the human brain responds to these fields in some way, that does not mean that the brain is processing that. There is also the question of what mechanisms are in place within the mind or body which receive these signals. If the body does indeed have magnetoreceptors, where are they? The next step for researchers is to identify them.
The study of Kirschvink is one of the many publications delving into the mysteries of magnetic fields, as well as what impacts they have on humans. The HeartMath Institute could be the leader in this area of research.
The Global Coherence Initiative is an international effort started by some researchers at HeartMath, which seeks to help activate the heart of humanity and promote peace, harmony and a shift in global consciousness. GCI conducts groundbreaking research on the interconnection between humankind and Earth’s magnetic fields and energetic systems.
The hypotheses of the researchers, as well as the scientists behind this project, are as follows:
- The magnetic field of our planet is a carrier of biologically relevant information that connects all of the living systems;
- Every person affects this global information field;
- Collective human consciousness affects the global information field. People that meditate creating heart-centered states of care, love, and compassion will generate more coherent field environment. This can benefit other people and help offset the current planetary discord and incoherence;
- There is a feedback loop between humans and the energetic/magnetic systems of the Earth;
- The planet Earth also has several sources of magnetic fields which affect every one of us. Two of them are the geomagnetic field which emanates from the core of the Earth and the magnetic fields which exist between Earth and the ionosphere. Such fields surround the entire planet and act as protective shields blocking out the harmful effects of solar radiation, as well as cosmic rays, sand, and other forms of space weather. Without these fields, ice as we know it could not exist on Earth. They are part of the dynamic ecosystem of our planet.
Some other evidence which human beings can sense these fields:The scientist recognized that these energy fields, the solar activity and the rhythms taking place on Earth’s magnetic fields affect our health, as well as our behavior
When the magnetic field environment of the Earth is distributed, it can cause insomnia, mental confusion, or lack of energy. But, at times when the fields of the Earth are stable, people reporting increased positive feelings and more creativity and inspiration. This is likely because of a coupling between the human brain, cardiovascular and nervous system with resonating geomagnetic frequencies.
The Earth and the ionosphere generate some frequencies that range from 0.01 hertz to 300 hertz. Some of them are in the same frequency range as the one happening in our brain, cardiovascular system, and autonomic nervous system. This suggests one way for explaining how fluctuations in the magnetic fields of the Earth and the Sun can influence us. The changes maybe affect our brainwaves, heart rhythms, memory, athletic performance and overall health.
Changes in the fields of the Earth from extreme solar activity have also linked to some of the most fabulous creations of the art of humanity, as well as some of its most tragic events.
These fields are affecting us. But, what about how we change these fields?There is an overlap of the brain wave and heart rhythm frequencies with the field resonance of Earth. So, we are not just receivers of biologically relevant information, but also senders. For instance, our heart emits an electromagnetic field that changes according to our emotions. This field can be measured up to several feet away from our body, and it affects not only us but, also those around us.
The research made on this topic, which is still in its infancy, actually has immense ramifications for our world. Further on, it will also prove, as well as highlight the great extent to which our attitudes, emotions and intentions, matter and that these factors within the realm of non – material science, can affect all life on Earth. A coherent, and cooperative intention, could impact global events and improve the quality of life on Earth . Practicing love, gratitude, appreciation and bettering ourselves as an individual are some of the many crucial steps towards changing our planet for the better.
Thanks to: https://www.enlightened-consciousness.com | 0.825371 | 3.004535 |
A reflecting telescope (often called as reflector) is a form of telescope that consumes single or a combination of curved mirrors. This form of telescope has its own advantages due to which nearly all large and modern research grade astronomical activities prefer reflectors. These telescopes do not suffer from any kind of chromatic aberration.
Generally, reflectors are cheaper than refractors of the same size. These telescopes work in a wider spectrum of light. Soon after the invention, reflector telescopes reviews attained the positivity and these telescopes became extraordinary popular for astronomy as they provide in-depth observation during celestial sights.
Best Reflector Telescopes
When you love spending your night under the stars, this product with its enhanced features will make it a special experience for you. The telescope is invented with an impressive 1200mm focal length (f/5.9) XT8 mirror. The mirror coatings provide up to 94 percent enhanced reflectivity, i.e, you get a significant increase in ability to observe dust lanes even in nebulas, resolves the cores of the prominent globular star clusters and reveal some of the most subtle structures in the galaxy. It also has an eye-catching metallic blue optical tube rides on its redesigned base with some adjustable altitude tension knobes.
Like any other reflector telescopes, this product may occasionally require minor collimation adjustments when you desire for peak performance, but the innovaters has made it easy by equipping a secondary and primary mirror with thumbscrew adjustments, i.e, you can now adjust those alignments without using any tool.
It has a big, 2” dual-speed Crayford focuser that lets you experience sharp details of your celestial targets with its fine-focus ratio of 11:1. The Crayford focuser comes with a 1.25-inch step-down adapter that can be used with 2-inch and 1.25-inch eyepieces. With all these mind-boggling features, this product makes itself a best reflector telescope. Moreover, the telescope’s bright white base trim helps you to avoid bumping into or tripping over those pieces of equipments that are hard to see in low-light conditions.
What we like about it:
There are certain reasons for why this product is listed among best reflector telescopes:
- Its Crayford design provides smooth and accurate focus adjustment
- Its Dobsonian design delivers point-and-view simplicity
- It comes with additional accessories like collimation cap, telescope focuser, dust caps, and free download of special edition Starry Night astronomy software.
Being a computerized star locating telescope, Celestron – Nexstar 130SLT offers the database of more than 40,000 stars, nebulae, galaxies, and whatnot. Its 130mm aperture works well to assemble enough light to observe the Solar System and even beyond. Its optics are aluminium multi-coated glass parabolic mirror that by far improves the transmission of light and its contrast. This feature of this reflector telescope enables you to enjoy deep sky viewing with intense detail, crispness, and clarity.
Its compact built feature makes it easily portable and provides easy assembly just about anywhere, i,e. you can ideally enjoy your weekend camping trips and excursions to night sky sites with your family. The alignment procedure is easy to get started. All you need to do is simply centre any three bright objects in the eyepiece and it automatically aligns to the night sky.
Celestron reflector telescope reviews are more positive than negative. This shows the efficient performance of the product. Its computerized feature includes free download of one of the top and popular consumer rated astronomy software programs. Talking about its computerized Go-to feature, it is ideal for beginners to intermediate users. It is also compatible with all Celestron’s most popular and used accessories. Concluding, this 130 SLT is a standard 130mm f/5 Newtonian with optical performance. Plus, two-year warranty from the manufacturers and unlimited access to technical support is a big plus.
What we like about it:
The main reasons for listing this in the list are:
- Easy and quick installation and no additional tool setup required
- Being portable, it is light in weight. Plus, it doesn’t go over your budget.
- Computerized “Go-to scope”, i,e. it includes ‘the sky’ astronomy software ( one of the best software planetariums)
Being a table-top reflector and with optimum reflector telescope review, it provides versatile performance. You can rotate its mount to 360degrees and also up and down with smooth motions. Its altitude tension knob reduces and adjust the tension of up-down movement and help to the lock the optical tube in place.
The portable design gives the Orion StarBlast 6 great and flexible portability. Speaking about portability, it weighs around 23.5 lbs. Moreover, this sturdy reflector base arrives pre-assembled in the box. This allows hassle free set up in no time. The box include eyepiece rack, 25mm and 10mm Sirius Plossl, 1.25” telescope eyepieces. EZ Finder II aiming device, and the Starry Night Software. This telescope is ideal for beginners as well as seasoned astronomers because of its easy operation and versatile performance.
The StarBlust 6 boasts about providing amazing lunar explorations of the Moon, jaw-dropping sights of other planets namely Mars, Jupiter, and Saturn including its stupendous rings. Its 150mm aperture parabolic reflector optics consumes enough light from the objects well beyond the Solar System. It follows a simple alignment procedure where you can use its EZ Finder II sight in order to accurately aim the objects in the sky. Its red dot feature asks you to move the telescope until the red dot is on the object that you want to see. Once it is done, you need to peek through telescope eyepiece and the desired object will be there.
What we like about it:
Every product has its own special features. The features that make this telescope worthy to be listen in this list are:
- Compact table-top design
- For hassle free setup, it comes pre-assembled in the box
- Reveals good details on the moon as well as other bright deep-sky objects
The Meade Polaris 130 EQ boasts decent aperture scopes with good equatorial mounts and supplemented by a stainless steel tripod. Speaking of the equatorial mount, the slow motion control feature makes it easy to track celestial objects smoothly and simply. Just like the above mentioned products, its red dot viewfinder helps you to point your scoping objects that you want to observe. It includes an accessory tray that lets you place your stuff while observing the night sky.
Included astronomical software and instructional DVD helps you to observe more about the celestial bodies. It has an aperture of 130mm and the focal ratio of f/5. Its three eyepieces provide variety of magnifications to support your viewing applications, i.e., for low power, there is an eyepiece of 26mm, for medium power, it has a 9mm eyepiece, and for high power, it has 6.33mm eyepiece. Its rack-and-pinion focuser provide you with a way to fine tune your views of the night sky very easily.
The focal length of about 127mm gives a view of narrow field and is quite ideal for small objects. The manufacturers speaks about the product that the Polaris 130 is packed with all the features that you need to the view the wonders of the sky for the first time out. Speaking of which, this telescope is optimum for beginners as well.
What we like about it:
Apart from its optimum aperture and lenses, there are certain other reasons for why this product is listed among best reflector telescopes:
- Its metal German Equatorial Mount provides slow motion control for convenience
- It delivers bright and clear images for the aspiring astronomers
- Inclusion of astronomical software and instructional DVD
It is a complete assembled telescope weighing about 27 lbs. for maximum convenience while travelling. Speaking of portability, it is made of short 24 inch long optical tube design. Its fast f/5 focal ratio works well for pleasing wide field performance. Its 130 mm parabolic primary mirror provides great and detailed views of deep-sky objects. It includes EQ-2 mount and stable tripod as well. This equatorial mount has dual setting circles and slow motion hand controls.
Moreover, its simple polar alignment procedure allows you to easily track the celestial objects. These celestial objects appear to migrate across the night sky. The included accessory tray provides you the space to place your eyepieces, flashlights, and other accessories close to you while you are indulged in using this reflector telescope. The eyepiece’s moderate magnification provides a great way to begin exploring interesting objects in the night sky.
It includes tripod, accessory tray, two 1.25 inch Sirius Plossl eyepieces (ranging 25mm and 10mm), 1.25 inch rack and pinion focuser, collimation cap, Starry Night astronomy software, and more. The Starry Night Special Edition software can help you plan your observations and understand those observations even when its cloudy in the sky. This telescope kit comes with every additional accessory that you will need to explore the sky (however, the assembly is required). When you have just started reading astronomy, this telescope will compliment your research in best possible ways.
What we like about it:
There are number of reasons to buy this Orion 130ST that also has positive reflector telescope reviews:
- It is capable to gather ample light for getting detailed and great views of the moon and other celestial objects
- Light-weighted, easily portable, and includes assembly tray with strong tripod
- Optimum or beginner and intermediate users
How We Chose The Top Reflector Telescopes In Our List
While listing these reflector telescopes, there are certain things and criteria that were kept in mind. These criteria are more like guidelines that can help you as well for buying your best reflector telescope for your every astronomical purpose:
- Aperture– Aperture forms the most important feature of a telescope. The aperture’s diameter is expressed either in millimetres or in inches. The average numbering of telescope’s aperture should be 2.8 inches (or 70 mm) – and preferably more.
- Telescope mount- A telescope always needs something sturdy for its support. Usually, standard telescopes come packaged with mounts or tripods, or with tubes of smaller scope having a mounting block that allows it to get attached to a standard photo tripod.
- Size- Even though a telescope isn’t a tiny object yet the optimum size matters. To be more specific, the size of the telescope should be compact and portable so that you don’t face any difficulty in case you want to travel the world and explore the galaxy with your equipment.
- Quality- When buying a telescope, its built quality plays a crucial role. Along with its aperture, mirror, focal length or lenses, its overall built quality determines its longevity. With the sturdy built quality telescope, you will be forever excited to explore the night sky.
- Installation- The telescopes should be easy to install. The longer it will take to get installed, the more you will get tangled in the process. These reflector telescopes have easy installation process to provide you hassle free situation.
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- Best Telescope Under $500 | 0.808643 | 3.347613 |
The Fiber-fed Extended Range Optical Spectrograph
FEROS (the Fiber-fed Extended Range Optical Spectrograph) is a spectrograph installed at the MPG/ESO 2.2-metre telescope located at ESO’s La Silla Observatory. FEROS can collect data with high resolution and in wavelengths from near-ultraviolet to infrared, covering the entire visible spectrum.
The combination of covering a large spectral range with a high resolving power has made FEROS particularly useful for research. Astronomers have used FEROS to study exoplanets in other galaxies and evolved stars on the verge of swallowing orbiting planets. FEROS data were also used to accomplish the first detection of lithium in an exploding star. The instrument can also be used for radial velocity measurements of astronomical objects like exoplanet systems, binary stars, and star clusters.
FEROS is an Échelle spectrograph. Spectrographs separate incoming light into individual wavelengths to produce spectra. Astronomers compare known spectra to those of astronomical objects to discover different characteristics of the object like composition or movement in space. An Échelle spectrograph uses a grating with high-angled cuts, prisms, and lenses to separate the light. These optical components are precisely organised to produce spectra with a high resolution, so astronomers can analyse spectral features of celestial bodies in more detail.
Originally installed on the ESO 1.52-metre telescope, the instrument saw first light on 6 October 1998. A few years later the telescope was decommissioned, and FEROS was then moved to the MPG/ESO 2.2-metre telescope. FEROS continues to be used today by Chilean astronomers and researchers from the Max Planck Society.
Science highlights with FEROS
- FEROS part of a team of instruments that finds that most very bright high-mass stars, which drive the evolution of galaxies, do not live alone (eso1230)
- New study finds mysterious lack of dark matter in Sun’s neighbourhood (eso1217)
- Planet found on the verge of being swallowed by its parent star, showing us the Earth's future (eso0305)
The authoritative technical specifications as offered for astronomical observations are available from the Science Operations page. | 0.815364 | 3.787757 |
Earth is the only spot in our close planetary system where people can live without a spacesuit. So, in the event that we wandered outside the comfortable limits of our home, to what extent would we live on different planets? How’s life on other planets? So, fasten your seat belts and let’s begin our journey in search for our new home.
The Hot Dot
Mercury, the nearest planet to the Sun, is really not the hottest in the system, yet it has the most extreme of temperatures. Scientists once believed Mercury was tidally locked – meaning only one side of the planet faced the Sun which explains why one side is so hot while the other is so cold. But Mercury does rotate, just incredibly slow. At its current rotational speed, it takes around 176 Earth days to encounter one Mercurian day-night cycle. But we will die in two minutes due to burning up and freezing.
Not So Lovely
Mercury’s neighbor, Venus, is often thought of as Earth’s twin sister because of the planets’ similar size and composition. But, the grass isn’t greener on the other side because well there is no grass at all. The planet’s atmosphere, composed mainly of thick carbon dioxide, traps the Sun’s heat causing scorching surface temperatures higher than 470 degrees Celsius. The excess amount of CO2 molecules scatters the Sun’s light, staining the sky a reddish orange. You better take in that surprising view fast since it’s the exact opposite thing you’ll see since Venus will vaporize you in under one moment.
Mars is the number one contender for mankind’s future. Home and living there will truly blow your mind. Despite its flaming red color, Mars is not hot. The average annual temperature is minus 60 degrees Celsius with a low of minus 153 degrees. The air of Red Planet will leave you begging for a breath, and silica dust will start to cloud your lungs. Mars’s low atmospheric pressure will cause your organs to rupture within two minutes, resulting in a fast but painful death.
So Big So Empty
Jupiter is nice to look at but if you touch it, you’ll die. The gas goliath has no surface, so your body will plummet through cloud-like layers made up of hydrogen and helium. As you fall further, temperature and weight will rise. But you won’t feel anything because the pressure killed you in less than one second after arriving on the planet.
The Ring of Death
Saturn is another work of universal art. Driving across those rings would be like Rainbow Road in real life. Except not at all because Saturn’s rings aren’t solid. They’re made up of billions of particles that range in size and are almost entirely water ice. Furthermore, you likely won’t discover strong ground on the planet itself. Like Jupiter, the gassy piece of Saturn would swallow your inert body quicker than the tick of a clock.
The Humpty and Dumpty
Uranus and Neptune don’t offer any desire for survival either. And you did likely die of boredom on the way there, considering the billions of kilometers of travel anyway. The ice giants are comprised of for the most part whirling liquids. However, they get their blue tones from methane gas in their environments, which would make you choke. Over the dangerous gas, the extraordinary temperatures on the two planets would add to an almost moment demise.
Home Sweet Home
We are entirely fortunate to live on Earth. Our planet’s proximity to the Sun enables water to exist in liquid form, regulates temperatures and provides energy for photosynthesis. Earth’s atmosphere has a perfect mix of gases that allow us to breath and the planet’s relatively stable magnetic field keeps solar storms from frying us to a crisp. So, be thankful for our planet and treat her well, because no one wants to spend their entire life in a spacesuit.
Hope I have provided you some basic information’s on How’s life on other planets. You can enjoy our trip!!!
- Organic-Rich Ocean Hiding Under The Surface of Pluto
- Direct Pictures of a Pair of Planets That Were Born | 0.830061 | 3.288961 |
A hint that quantum fluctuations in the fabric of the universe slow the speed of light has not been borne out in observations by NASA’s Fermi telescope. The measurements contradict a 2005 result that supported the idea that space and time are not smooth.
Einstein’s theory of special relativity says that all electromagnetic radiation travels through a vacuum at the speed of light. This speed is predicted to be constant, regardless of the energy of the radiation.
Yet in 2005, the MAGIC gamma-ray telescope on La Palma in the Canary Islands suggested the speed of light might not be constant after all. The telescope, which measured the light released by a galaxy around 500 million light years away, found that higher energy photons arrived four minutes behind their lower energy counterparts.
The discovery hinted that the speed of light may change depending on its energy. This effect could be a consequence of some theories of quantum gravity, which attempt to unify Einstein’s theory of gravity with the laws of quantum mechanics. These models postulate that space and time are not smooth. Instead space-time is inherently grainy, fluctuating rapidly over distances of about 10-35 metres, a length called the Planck scale.
If space-time is grainy, higher-energy photons would move more slowly than their lower-energy counterparts. That’s because higher-energy photons have smaller wavelengths, which makes them more sensitive to tiny fluctuations in space-time.
However, the MAGIC lag was apparently too large to be easily explained by graininess on the quantum scale. If the delay were caused by fluctuations in space-time, they would have to occur on scales more than 10 times larger than the Planck scale.
“This intriguing evidence has been wandering around in the quantum gravity community for more than a year now, with hope on the progressive side, and stomach aches on the conservative side,” says physicist Giovanni Amelino-Camelia of Sapienza University of Rome in Italy.
Now new observations suggest quantum gravity cannot be responsible for the time delay observed by MAGIC. The light from a powerful, 7-billion year old gamma-ray burst detected by NASA’s Fermi Gamma-ray Space Telescope shows no evidence of a lag between photons of a range of energies.
“We have fewer stomach aches now,” says Amelino-Camelia. “The Fermi data has pushed the limit where it’s now proven the MAGIC data cannot be interpreted in that way.”
Fermi’s measurement is the most stringent direct limit on how much the speed of light might vary with energy, says Jonathan Granot of the University of Hertfordshire in the UK, who led the analysis of the burst. “For the first time, we can put the limit [down to] the energy scale in which quantum effects would alter the geometry of space time.”
The MAGIC time delay may be down to an astrophysical process where particles are accelerated to enormous energies within the hearts of galaxies. Follow-up calculations after MAGIC’s 2005 result showed that is possible to produce flares that release lower-energy radiation before higher-energy radiation, according to MAGIC collaborator Robert Wagner of the Max Planck Institute of Physics in Munich, Germany. “I think what we can say for the time being is quantum gravity effects cannot be the dominant effect,” he says.
The result does not necessarily strike a blow to quantum gravity. Only a subset of models predict the effect, and “while it seems reasonable to expect that the variation of the speed of light with energy is a sign of quantum space-time, there is no well developed theory of quantum space-time that cleanly makes this prediction,” says Lee Smolin of the Perimeter Institute for Theoretical Physics in Waterloo, Canada.
What’s more, it will require even more precise measurements to completely exclude the possibility that light may change its speed depending on its energy. “If there is an effect, the experiment is now at the threshold of scales where the effect is expected, and there is the exciting prospect that it could be discovered over the…next few years,” Smolin says.
Journal reference: Nature (doi:10.1038/nature08574)
More on these topics: | 0.818076 | 4.180386 |
Reporting from Edwards Air Force Base — NASA rolled out its next-generation space capsule here Wednesday, revealing a bulbous module that is scheduled to carry humans back to the moon in 2020 and eventually onward to Mars.Unlike the space-plane shape of the shuttles, the new Orion Crew Exploration Vehicle looks strikingly similar to the old Apollo space capsule that carried Neil Armstrong, Buzz Aldrin and Michael Collins to the moon and back in 1969, with Armstrong and Aldrin becoming the first humans to walk on the lunar surface.There is one key difference, however. The test module, unveiled at NASA’s Dryden Flight Research Center, is substantially bigger — 16.5 feet in diameter compared with Apollo 11’s 12.8 feet.Still, cramming six astronauts inside will make it “pretty cozy,” he said.
The craft’s extra girth will allow it to carry six astronauts instead of Apollo’s three.
“This is the same shape as Apollo,” said Gary Martin, the project manager for the test program at Dryden. “But the extra space translates into twice as much volume as Apollo.”
Oooh, I’m impressed! /not!
How many times can the wheel be reinvented?
Quite a few apparently.
Finding ancient meteorites on the moon would be exciting enough, but what they may contain really interests Houtkooper.
Consider simple bacterial life on the early Earth, existing inside a rock which is then blasted off the surface of the planet by a large impact. In theory, some of these samples could have landed in lunar craters like Shackleton. Once there, they would be perfectly preserved in a deep freeze for billions of years. Life carried to the moon in this way would almost certainly be dead, although it is possible that some hardy creatures could survive the journey in a dormant state. As Houtkooper succinctly states, “there could be signs of life from early Earth on the moon.”
Things get particularly interesting when a large impact on the moon by an object around 10 km in diameter is considered. If that were to occur, enough material would be thrown up to create a very thin lunar atmosphere. This tenuous atmosphere could last a few hundred years, just enough time to spark into action any dormant life that had been carried to the moon from other worlds.
So it is possible that, dotted throughout the moon’s colorful history, it may have hosted simple but live alien organisms.
Panspermia has made a comeback in recent months, both as a means of transferring life throughout the Cosmos naturally and artificially.
Viability of the organisms being transported about is the issue.
How can living things withstand the rigors of freezing cold, solar and cosmic radiation?
Here are some articles that might answer some of these questions:
A ~ 10-metre object on a heliocentric orbit, now catalogued as 1991 VG, made a close approach to the Earth in 1991 December, and was discovered a month before perigee with the Spacewatch telescope at Kitt Peak. Its very Earth-like orbit and observations of rapid brightness fluctuations argue for it being an artificial body rather than an asteroid. None of the handful of man-made rocket bodies left in heliocentric orbits during the space age have purely gravitational orbits returning to the Earth at that time, and in an3′ case the a priori probability of discovery for 1991 VG was very small, of order one in 100,000 per anmun. In addition, the small perigee distance observed might be interpreted as an indicator of a controlled rather than a random encounter with the Earth, and thus it might be argued that 1991 VG is a candidate as an alien probe observed in the vicinity of our planet.
I think mainstream SETI is afraid of finding Bracewell Probes, because it shakes them from the comfortable notion that material interstellar travel is impossible and any civilization is a safe thousands of light-years away, accessible only by micro and radio waves.
Adam Crowl does ask an interesting question, “…if it is a probe, then why is it suddenly becoming visible? Based on our primitive attempts at invisibility cloaks using meta-materials I suspect any advanced technological species will be able to remain unseen by primitive eyes… yet here we have a probe making itself blatant. Hmmm…”
Hmmm indeed Adam.
The Benfords — Jim at Microwave Sciences, Gregory at the University of California’s Irvine campus, and Dominic (Jim’s son) at NASA GSFC — believe that advanced societies, if they are to be found, ought most likely to exist toward the galactic center, and probably at distances of over a thousand light years. We’re thus talking, in all likelihood, about interstellar beacons rather than targeted transmissions when it comes to SETI. And if beacons are indeed at play, what can we say about their costs, and do our own standards of terrestrial cost have any application in an ETI context?
The message here is that any SETI search has to make assumptions about the beacon builders, and if we can determine something about the economics of the situation, we may learn how to target our searches more effectively. Here’s the essence of the argument about ETI:
We assume that if they are social beings interested in a SETI conversation or passing on their heritage, they will know about tradeoffs between social goods, and thus, in whatever guise it takes, cost. But what if we suppose, for example, that aliens have very low cost labor, i. e., slaves? With a finite number of slaves, you can use them to do a finite number of tasks. And so you pick and choose by assigning value to the tasks, balancing the equivalent value of the labor used to prosecute those tasks. So choices are still made on the basis of available labor. The only case where labor has no value is where labor has no limit. That might be if aliens may live forever or have limitless armies of self-replicating automata, but such labor costs something, because resources, materials and energy, are not free.
Our point is that all SETI search strategies must assume something about the beacon builder, and that cost may drive some alien attempts at interstellar communication.
SETI always seems to come with a built-in willingness to think the best of extraterrestrial cultures. If an alien civilization is sending out a message, it must be doing so out of altruism. The Benfords, though, are interested in exploring motivations from a different angle. They’d like to relate them to the only case of a technological civilization we know of, ourselves, and speculate based on human history. From that perspective, there are two reasons for sending out messages across vast time scales.
Think about what people do. You can go to the Tower of London and explore the chambers where famous prisoners like Thomas More were kept. Invariably, on the walls, you’ll find graffiti, names written into the stone. People have an apparently robust need to engage in one-way communication, putting a note in a bottle and throwing it. Indeed, the Pioneer and Voyager spacecraft are examples of the impulse. Is it likely that any of these tiny vessels will ever be intercepted? Yet putting our names, our stories, our music and our pictures on board outgoing vehicles is a method that resonates. We have a need to encapsulate who we are.
A second reason is the drive to communicate the optimum things about our culture, what Matthew Arnold called “…the best that has been thought and said in the world.” Here the Benfords cite time capsules and monuments as examples of our need to propagate our culture. The contemplation of a legacy is involved here, especially in a scenario where human lifetimes are rising. Here again the communication can be one-way. The statue of King Alfred my wife and I admired in Winchester some years back was not built to impress people within a tight time frame, but to stand as a monument that would reach future generations.
So imagine scenarios like this: A civilization with an ability to plan over millennial time scales foresees problems that are beyond its capabilities. A SETI beacon might encapsulate a call for information and help — send us everything you have on stellar warming…
Here’s another: A civilization in its death throes decides to send out an announcement of its existence. We were here and are no longer, but as long as this message endures, so in a sense do we. And let’s not discount sheer pride of the sort that could keep a beacon in operation long after the beings that built it were gone. Robotically maintained, it might boast of achievements set against the backdrop of the ruin that may eventually attend all technological cultures. Or perhaps we’ll run into interstellar proselytes, out to convert the galaxy to a particular set of beliefs by placing their highest values into their outgoing signal.
I’m glad that finally somebody in mainstream SETI studies have proposed something different to think about when it comes to listening to, or broadcasting signals.
While I feel SETI should do more than just do the radio thing and look for possible Bracewell Probe signals, the Benford Clan at least looked outside the box.
The Monument Beacon theory sounds good, but something else should be added onto that.
If a suspected source is found, perhaps we should train all of our available listening, optical, and any other measuring devices we can muster to locate a Transcension Fossil in its general direction.
Yeah I know, semi-religious technorapture crap and such an object would be hard to find, even if the broadcast signal was strong enough.
But if we were lucky enough to intercept a Beacon in the first place, why not trace it back to the source to see if such things as Technological Singularities take place?
It could explain the Fermi Paradox.
And give us a clue to our ultimate fate possibly.
I had an encounter with an interesting commenter for a couple of days about a post I did about The Galactic Internet and the Cepheid stars. I mentioned SETI and a passing reference to attention should paid to the UFO phenomenon more because it could possibly help with SETI and that the mainstream shouldn’t be so close-minded about it.
Well, you would’ve thought I dug Einstein himself up out of the ground and pissed on the corpse!
In a nutshell, his beef was that the UFO issue wasn’t worth the time because there’s no physical evidence and that it belonged to the fairy, gnome, ghost and whatever superstition you can dream up file. He refused to discuss the post at hand and kept wanting to rant at me about UFOs.
I figured he was some kind of college kid, or maybe even a teacher at a school. At worse, probably a plain ol’ troll!
He raised an interesting point however, “it’s a contradiction to assume that alien technology is millions of years ahead of ours and then expect them to risk their lives by putting their fragile bodies in primitive physical capsules (ufos), when undetectable remote sensing would do the job.”
Why indeed? A pretty good point actually.
Why would an advanced race, unless they were an evolved AI, want to cross interstellar space just to study primitive aboriginals?
Which brings us to this post from UFO Digest:
“The clearest and most succinct summary of reported UFO characteristics I have yet to find was written by the late Dr. J. Allen Hynek in a foreword to the book The UFO Controversy in America (4).
“The reported ability to execute trajectories, often but not always silently, that no known man-made craft could generate or follow; the ability to hover, and then to accelerate to high speeds in the order of seconds (and generally without a sonic boom); on occasion to change shape, and to produce durable physical effects on both animate and inanimate matter. To be, on occasion, unmistakably detected on radar, yet to be peculiarly localized and preferential in their manifestation (that is, their appearance at times and places when and where they would be least likely to be detected, and their avoidance of level flight which would of necessity open them to observation by people along the way). The pattern in the ‘close encounter’ cases is almost universal: a rapid descent to a landing or near landing, a stay of the order of only minutes, and the ascent, at usually a high angle, and disappearance either through distance or by some other means (it is often reported that at a height of a few hundred feet the bright luminosity vanishes). The choice of locale is statistically significant. The close encounter cases simply do not occur on the White House lawn or between halves at the Rose Bowl game, but in desolate spots, generally some distance from habitation and where detection would be least expected. In a small percent of the close encounter cases, robot-like or human-like “creatures” are reported.”
“Dr. Hynek should not need an introduction to anybody who has made even the slightest foray into the field of UFO literature. His own book, The UFO Experience: A Scientific Inquiry (3) is considered a classic in this field and many people, myself included, think it is probably the most important book ever written on this subject. The book includes an appendix listing some eighty cases that were carefully selected by Hynek for maximum credibility. Reading these cases it is easy to conclude that the phenomena in question does not move in a way that is dependent on aerodynamics or on any kind of standard propulsion system. Can we create a set of familiar circumstances that would serve an an analog to what has been so consistently reported and ably summarized by Dr. Hynek?”
Now I can’t pretend to know anything about quantum physics/mechanics, like the author here, I’m only a layman. But the world of the very small is an area of nature we have only begun to explore fully and there are many, many unanswered questions on how it works.
But work it does, our computer chip technology and the Internet Google-Plex utilizes some of its principles.
And without it, our present society couldn’t exist.
Hat tip to The Anomalist
Suppose for a moment that life really is rare in the universe. That when we are able to investigate the nearby stars in detail, we not only discover no civilizations but few living things of any kind. If all the elements for producing life are there, is there some kind of filter that prevents it from proceeding into advanced and intelligent stages that use artifacts, write poetry and build von Neumann probes to explore the stars? Nick Bostrom discusses the question in an article in Technology Review, with implications for our understanding of the past and future of civilization…
Bostrom’s idea of a ‘Great Filter’ comes from Robin Hanson (George Mason University), and consists of the kind of transition that a civilization has to endure to emerge as a space-faring culture. The key question: Is the filter ahead of us or behind? If behind, wonderful — we have already passed the test and can look with some confidence to the future. Recent work, for example, indicates that human beings were reduced to a band of as little as 2000 individuals some 70,000 years ago, near extinction. Yet somehow migrations out of Africa began 60,000 years ago, and all the tools of civilization would emerge in their wake.
I was really taken aback when I read this piece from Bostrum. Of all the people who display paroxysms of anthropocentrism and ethnocentrism, he would be the last person I would expect to display such.
I read Paul Gilster’s blog every day for it’s no nonsense science and for the spirited, intelligent commenting that happens there. I think I live there as much as I live here! And I agree whole-heartedly with his commentary at the end.
To add to his commentary I would like to paraphrase a statement from Graham Hancock; ” To believe there is no other intelligent life in the Universe and there are no other great civilizations is be arrogant and stupid…”
Not an exact quote, but the idea is the same. | 0.939205 | 3.199849 |
Moon* ♊ Gemini
Moon phase on 4 December 2006 Monday is Full Moon, 14 days old Moon is in Gemini.Share this page: twitter facebook linkedin
Moon rises at sunset and sets at sunrise. It is visible all night and it is high in the sky around midnight.
Moon is passing about ∠5° of ♊ Gemini tropical zodiac sector.
Lunar disc appears visually 1.4% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1921" and ∠1947".
The Full Moon this days is the Cold of December 2006.
There is high Full Moon ocean tide on this date. Combined Sun and Moon gravitational tidal force working on Earth is strong, because of the Sun-Earth-Moon syzygy alignment.
The Moon is 14 days old. Earth's natural satellite is moving through the middle part of current synodic month. This is lunation 85 of Meeus index or 1038 from Brown series.
Length of current 85 lunation is 29 days, 15 hours and 43 minutes. It is 1 hour and 43 minutes longer than next lunation 86 length.
Length of current synodic month is 2 hours and 59 minutes longer than the mean length of synodic month, but it is still 4 hours and 4 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠238.7°. At the beginning of next synodic month true anomaly will be ∠276.5°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
2 days after point of perigee on 2 December 2006 at 00:06 in ♉ Taurus. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 9 days, until it get to the point of next apogee on 13 December 2006 at 18:55 in ♍ Virgo.
Moon is 373 163 km (231 873 mi) away from Earth on this date. Moon moves farther next 9 days until apogee, when Earth-Moon distance will reach 404 418 km (251 294 mi).
5 days after its ascending node on 29 November 2006 at 10:26 in ♓ Pisces, the Moon is following the northern part of its orbit for the next 8 days, until it will cross the ecliptic from North to South in descending node on 12 December 2006 at 15:19 in ♍ Virgo.
5 days after beginning of current draconic month in ♓ Pisces, the Moon is moving from the beginning to the first part of it.
11 days after previous South standstill on 23 November 2006 at 07:12 in ♐ Sagittarius, when Moon has reached southern declination of ∠-28.442°. Next day the lunar orbit moves northward to face North declination of ∠28.402° in the next northern standstill on 6 December 2006 at 03:33 in ♊ Gemini.
The Moon is in Full Moon geocentric opposition with the Sun on this date and this alignment forms Sun-Earth-Moon syzygy. | 0.860247 | 3.1372 |
A new image from NASA’s Hubble Space Telescope provides important new details about the first interstellar comet astronomers have seen in our solar system.
The comet, called Comet 2I/Borisov (the “I” stands for interstellar), was spotted near a spiral galaxy known as 2MASX J10500165-0152029. It was approximately 203 million miles from Earth when the image was taken on Nov. 16.
“Data from the Hubble Space Telescope give us the best measure of the size of comet 2I/Borisov’s nucleus, which is the really important part of the comet,” said David Jewitt, a UCLA professor of planetary science and astronomy who analyzed and interpreted the data from the new image.
Jewitt collaborated on the new analysis with colleagues from the University of Hawaii, Germany’s Max Planck Institute for Solar System Research, the Space Telescope Science Institute in Baltimore and Johns Hopkins University’s Applied Physics Laboratory. The scientists were surprised to learn that the nucleus has a radius measuring only about half of a kilometer — or less than one-fifteenth the size that earlier investigations suggested it might be.
“That is important because knowing its size helps us to determine the total number, and mass, of other similar objects in the solar system and the Milky Way,” Jewitt said. “2I/Borisov is the first known interstellar comet, and we would like to learn how many others there are.”
The comet is traveling at a breathtaking speed of 110,000 miles per hour — one of the fastest comets ever seen, Jewitt said. More commonly, comets travel at about half that speed.
Crimean astronomer Gennady Borisov discovered the comet on Aug. 30, using a telescope he built. Based on precise measurements of its changing position, the International Astronomical Union’s Minor Planet Center calculated a likely orbit for the comet, which shows that it came from elsewhere in the galaxy. Jewitt said its precise point of origin is unknown.
A second Hubble Space Telescope image of the comet, taken on Dec. 9, shows the comet even closer to Earth, approximately 185 million miles from Earth, he said.
Comets are icy bodies thought to be fragments left behind when planets form in the outer parts of planetary systems.
Observations by numerous telescopes show that the comet’s chemical composition is similar to that of comets previously observed in our solar system, which provides evidence that comets also form around other stars, Jewitt said. By mid-2020, the comet will have zoomed past Jupiter on its way back into interstellar space, where it will drift for billions of years, Jewitt said.
This article originally appeared in the UCLA Newsroom. | 0.920884 | 3.90266 |
NASA has published the first batch of results from the New Horizons’ Kuiper Belt object flyby that took place on January 1, 2019. Only about 10-percent of the data from that flyby has been transmitted back to researchers on Earth, but the findings have been shared in a study published on May 17. According to the space agency, the object — which is nicknamed Ultima Thule — is ‘far more complex than expected.’
The Kuiper Belt object is officially named 2014 MU69, but is more often referred to as Ultima Thule. The object has an unusual shape resulting from the ‘gentle merger’ of two previously independent bodies that attach at a juncture point NASA calls ‘the neck.’ The object is located around four billion miles from Earth and holds the distinction as the most distant object humans have ever explored.
NASA paints a striking profile of Ultima Thule, explaining that the object is about 22 miles long with a contact binary arrangement, two very different lobe shapes, and an overall appearance that — though still mysterious — likely points at whatever caused the formation billions of years ago. NASA calls the strange shape an ‘unanticipated mystery’ that may one day be unraveled by additional data.
The two space objects were likely tidally locked, gradually slowing over a long period of time before ultimately joining together into the Ultima Thule we see today. New Horizons Principal Investigator Alan Stern explained, “We’re looking into the well-preserved remnants of the ancient past.”
The study sheds some light on the object’s unique features, including the presence of a large depression measuring about 5 miles wide, ‘hills and troughs,’ and smaller pits that may have formed due to sublimation or some other type of material change. As the image above shows, Ultima Thule has a distinct reddish color, with NASA stating that it is the reddest object ever visited by humans in the outer solar system.
This is only the start of what we know about this Kuiper Belt object. NASA explains that data from the New Horizons flyby will continue to trickle in over coming months leading up to summer 2020. At this time, the New Horizons spacecraft is located around 4.1 billion miles from Earth, traveling deeper into the Kuiper Belt at around 33,000 mph. | 0.817599 | 3.432388 |
The supermassive black hole at the center of the Milky Way galaxy, Sagittarius A* is 26,000±1,000 light years from Earth.
We report on the detection in the combined Gaia-DR1/RAVE data of a lack of disk stars in the solar neighbourhood with velocities close to zero angular momentum. We propose that this may be caused by the scattering of stars with very low angular momentum onto chaotic, halo-type orbits when they pass through the Galactic nucleus. We model the effect in a Milky-Way like potential and fit the resulting model directly to the data, finding a likelihood (∼2.7σ) of a dip in the distribution. Using this effect, we can make a dynamical measurement of the Solar rotation velocity around the Galactic center: v⊙=239±9 km s−1. Combined with the measured proper motion of Sgr A∗, this measurement gives a measurement of the distance to the Galactic centre: R0=7.9±0.3 kpc.
Jason A. S. Hunt, Jo Bovy, Raymond G. Carlberg, "Detection of a dearth of stars with zero angular momentum in the solar neighbourhood" (6 Oct 2016). | 0.837581 | 3.469048 |
Nasa has put a miniaturised atomic clock in orbit that it believes can revolutionise deep-space navigation.
About the size of a toaster, the device is said to have 50 times the stability of existing space clocks, such as those flown in GPS satellites.
If the technology proves itself over the next year, Nasa will install the clock in future planetary probes.
The timepiece was one of 24 separate deployments from a Falcon Heavy rocket that launched from Florida on Tuesday.
The other passengers on the flight were largely also demonstrators. They included a small spacecraft to test a new type of “green” rocket fuel, and another platform that aims to propel itself via the pressure of sunlight caught in a large membrane; what’s often called a “lightsail”.
But it is the mercury-ion atomic clock, developed at Nasa’s Jet Propulsion Laboratory (JPL), which has had most attention.
Today, deep-space probes are tracked across the Solar System via radio signals.
These signals are sent from Earth and are immediately returned by the spacecraft. The very precise time taken for the speed-of-light messages to echo back enables navigators to work out the mission’s exact position and to command the necessary course corrections.
But if probes carried their own atomic clocks, this two-way system could be reduced to one-way, and the missions’ onboard computers would then make all the necessary navigational calculations.
The atomic clocks currently used on Earth for deep-space navigation are refrigerator-sized. JPL’s engineers have shrunk this down to something that can easily be accommodated on a spacecraft.
Deputy principal investigator Jill Seubert said “self-driving spacecraft” were one of the top technologies needed to put humans on Mars.
“Autonomous onboard navigation means that a spacecraft can perform its own navigation in real-time without waiting for directions to be sent from navigators back here on Earth. And with this capability, a human-crewed spacecraft can be delivered safely to a landing site with less uncertainty in their path,” she told reporters.
Don Cornwell, from Nasa’s Space Communications and Navigation Program, added: “Of course, for a spacecraft travelling well beyond Earth orbit, the smallest clock inaccuracies can lead to large navigational errors. But [the new clock] has a high degree of clock stability, meaning it can maintain its accuracy over many years.
“The deep space atomic clock’s design should gain or lose less than 2 nanoseconds per day, or an error of one second in nine million years.”
The development of the spacecraft chassis, or bus, that is carrying the clock was begun by the British manufacturer Surrey Satellite Technology Limited at its US division, which was then later sold to the American General Atomics company.
Surrey itself had an interest in six other spacecraft launched on Monday’s Falcon Heavy.
The UK firm assembled this sextet of platforms to be part of a constellation known as FORMOSAT-7. It is a joint US-Taiwanese initiative to monitor the weather by interrogating the way radio signals from GPS satellites are affected as they pass through the atmosphere.
Tuesday was the third time a Falcon Heavy had flown. The rocket is essentially three Falcon-9 rockets strapped together.
As is customary now for the rocket operator SpaceX, the three boosters were commanded to come back to Earth under control once they had finished the job of sending the multi-satellite mission on its way.
Two of the boosters successfully landed back at Cape Canaveral. The third just missed its touchdown target on a drone ship out in the Atlantic. | 0.822358 | 3.154982 |
What Is the Chandra X-Ray Space Observatory?
X-Rays: A Hidden Frontier
When you look around you, everything you see is through the visible portion of what we call the electromagnetic spectrum, or light. That visible part is but a narrow field of the total light spectrum, whose scope is wide and diverse. Other portions to this field included (but are not limited to) infrared, radio waves, and microwaves. One component of the spectrum which is just beginning to be used in space observations are x-rays. The main satellite that explores them is the Chandra X-Ray Observatory, and its journey to becoming that flagship started in the 1960s.
What is Sco-X1?
In 1962, Riccardo Giacconi and his team from American Science and Engineering entered an agreement with the Air Force to help monitor nuclear explosions in the atmosphere from the Soviets. In the same year, he convinced the Air Force (which was envious of the Apollo program and wanted in on it in some fashion) to launch a Geiger counter into space to detect x-rays from the moon in an effort to reveal its composition. On June 18, 1962, an Aerobee rocket was launched with the counter from White Sands Test Range in Nevada. The Geiger counter was in space for only 350 seconds, outside of Earth’s x-ray absorbing atmosphere and into the void of space (38).
While no emissions were detected from the moon, the counter did pick up a huge emission coming from the constellation Scorpius. They named the source of these x-rays Scorpius X-1, or Sco-X1 for short. This object was a deep mystery at the time. The Naval Research Laboratory knew that the Sun did emit x-rays in its upper atmosphere, but they were one-millionth as intense as the visible light emitted by the sun. Sco-X1 was thousands of times as luminous as the Sun in the x-ray spectrum. In fact, most of Sco’s emissions are solely x-rays. Riccardo knew more sophisticated equipment would be needed for further studies (38).
Chandra is Built and Launched
In 1963, Riccardo along with Herbert Gursky hand to NASA a 5-year plan that would culminate in the development of an x-ray telescope. It would take 36 years until his dream was realized in Chandra, launched in 1999. The basic design of Chandra is the same as it was in 1963, but with all the technological advances that have been made since then, including the ability to harness energy from its solar panels and to run on less power than two hair dryers (Kunzig 38, Klesuis 46).
Riccardo knew that x-rays were so energetic that they would simply embed themselves into traditional lenses and flat mirrors, so he designed a conical mirror, made of 4 smaller ones built in descending radius, that would let the rays “skip” along the surface which allows for a low angle of entry and thus better data collection. The long, funnel shape also allows the telescope to see further into space. The mirror has been polished well (so the biggest surface disturbance is 1/10,000,000,000 of an inch, or said another way: no bumps higher than 6 atoms!) for good resolution also (Kunzig 40, Klesuis 46).
Chandra also uses charged-coupled devices (CCD’s), frequently used by the Kepler Space Telescope, for its camera. 10 chips within it measure an x-ray's position as well as its energy. Just as it is with visible light, all molecules have a signature wavelength that can be used to identify the material present. Composition of the objects emitting the x-rays can thus be determined (Kunzig 40, Klesuis 46).
Chandra orbits the Earth in 2.6 days and is one-third the distance from the moon above our surface. It was positioned to increase exposure time and to decrease the interference from the Van Allen belts (Klesuis 46).
Findings of Chandra: Black Holes
As it turns out, Chandra has determined that supernovas emit x-rays in their early years. Depending on the mass of the star that goes supernova, several options will be left over once the stellar explosion is over. For a star that is more than 25 solar masses, a black hole will form. However, if the star is between 10 and 25 solar masses, it will leave behind a neutron star, a dense object made solely of neutrons (Kunzig 40).
A very important observation of galaxy M83 showed that ultra lumnoius X-ray sources, the binary systems that most stellar mass black holes are found in, can have quite an age variation. Some are young with blue stars and others are old with red stars. The black hole usually forms at the same time as its companion, so by knowing the age of the system we can gather more important parameters on black hole evolution (NASA).
A further study on galaxy M83 revealed a stellar-mass black hole MQ1 that was cheating on how much energy it was releasing into the surrounding system. This basis stems from the Eddington Limit, which should be a cap on how much energy a black hole can produce before cutting off its own food supply. Observations from Chandra, ASTA, and Hubble seem to show that the black hole was exporting 2-5 times as much energy as should be possible (Timmer, Choi).
Chandra can see black holes and neutron stars by an accretion disk that surrounds them. This forms when a black hole or a neutron star has a companion star that is so close to the object that it gets material sucked from it. This material falls into a disk that surrounds the black hole or neutron star. While in this disk and as it falls into the host object, the material can get so heated that it will emit x-rays that Chandra can detect. Sco-X1 has turned out to be a neutron star based on the x-ray emissions as well as its mass (42).
Chandra is not only looking at normal black holes but supermassive ones also. In particular, it makes observations of Sagittarius A*, the center of our galaxy. Chandra also looks at other galactic cores as well as galactic interactions. Gas can become trapped between galaxies and gets heated, releasing x-rays. By mapping where the gas is located, we can figure out how the galaxies are interacting with one another (42).
Initial observations of A* showed that it flared on a daily basis with some nearly 100 times as bright as normal. However, on September 14, 2013 a flare was spotted by Daryl Haggard, from Amherst College, and her team that was 400 times brighter than a normal flare and 3 times the brightness of the previous record holder. Then a year later a burst 200 times the norm was seen. This and any other flare are because of asteroids that fell to within 1 AU of A*, falling apart under tidal forces and heated up by the ensuing friction. These asteroids are small, at least 6 miles-wide and could come from a cloud surrounding A* (NASA "Chandra Finds," Powell, Haynes, Andrews).
After this study, Chandra looked again to A* and over a 5-week period watched its eating habits. It found that instead of consuming most of the material falling in, A* only will take 1% and release the rest into outer space. Chandra observed this as it looked at temperature fluctuations of the x-rays being emitted by the excited matter. A* may be not eating well because of the local magnetic fields causing material to be polarized away. The study also showed that the source of the x-rays was not from small stars surrounding A* but most likely from the solar wind emitted by massive stars around A* (Moskowitz, "Chandra").
Chandra led a study looking at supermassive black holes (SMBH) in galaxies NGC 4342 and NGC 4291, finding that the black holes there grew faster than the rest of the galaxy. At first scientists felt that tidal stripping, or lost mass through a close encounter with another galaxy, was at fault but this was disproven after x-ray observations from Chandra showed that the dark matter, which would have been partially stripped, remained intact. Scientists now think those black holes ate a lot early in their lives, preventing star growth through radiation and hence limiting our ability to fully detect the mass of the galaxies (Chandra “Black hole growth”).
This is just a part of mounting evidence that SMBHs and their host galaxies might not grow in tandem. Chandra along with Swift and the Very Large Array collected x-ray and radio wave data on several spiral galaxies including NCGs 4178, 4561 and 4395. They found that these did not have a central bulge like galaxies with SMBHs yet a very small one was found in each galaxy. This could indicate that some other means of galactic growth occurs or that we don't fully understand SMBH formation theory (Chandra “Revealing”).
Findings of Chandra: AGN
The observatory has also examined a special type of black hole called a quasar. Specifically, Chandra looked at RX J1131-1231, which is 6.1 billion-years-old and has a mass 200 million times that of the sun. The quasar is gravitationally lensed by a foreground galaxy, which gave scientists the chance to examine light that would normally be too obscured to make any measurements. Specifically, Chandra and the XMM-Newton X-ray observatories looked at light emitted from iron atoms near the quasar. Based on the level of excitement the photons were in scientists were able to find that the spin of the quasar was 67-87% the max allowed by general relativity, implying that the quasar had a merger in the past (Francis).
Chandra also helped in an investigation of 65 active galactic nuclei. While Chandra looked at the x-rays from them, the Hershel telescope examined the far-infrared portion. Why? In the hopes of uncovering star growth in galaxies. They found that both the infrared and x-rays grew proportionally until they got to high levels, where infrared tapered off. Scientists think this is because the active black hole (x-rays) heat the gas surrounding the black hole so much that potential new stars (infrared) cannot have cool enough gas to condense (JPL “Overfed”).
Chandra has also helped reveal properties of intermediate black holes (IMBH), more massive than stellar but less that SMBH's Located in galaxy NGC 2276, the IMBH NGC 2276 3c is about 100 million light years away and weighs in at 50,000 stellar masses. But even more intriguing is the jets that arise from it, much like SMBH's. This suggests that IMBH's may be a stepping stone to becoming a SMBH ("Chandra Finds").
Findings of Chandra: Exoplanets
Though the Kepler Space Telescope gets much credit for finding exoplanets, Chandra along with the XMM-Newton Observatory was able to make important findings on several of them. In the star system HD 189733, 63 light years away from us, a Jupiter-sized planet passes in front of the star and causes a dip in the spectrum. But fortunately, this eclipsing system impacts not only visual wavelengths but also x-rays. Based on the data obtained, the high x-ray output is because of the planet losing much of its atmosphere - between 220 million to 1.3 billion pounds a second! Chandra is taking this opportunity to learn more about this interesting dynamic, caused by the planet's proximity to its host star (Chandra X-ray Center).
Our little planet cannot affect the Sun much save for some gravitational forces. But Chandra has observed exoplanet WASP-18b having a huge impact on WASP-18, its star. Located 330 light years away, WASP-18b has about 10 Jupiters in total mass and is very close to WASP-18, so close in fact that it has caused the star to become less active (100x less than normal) than it otherwise would be. Models had shown the star to be between 500 million and 2 billion years old, which would normally mean it is quite active and has large magnetic and x-ray activity. Because of WASP-18b's proximity to its host star, it has huge tidal forces as a result of gravity and thus may pull on material that is near the star's surface, which affects how the plasma flows through the star. This in turn can wind down the dynamo effect that produces magnetic fields. If anything were to impact that movement then the field would be decreased (Chandra Team).
As it is with many satellites, Chandra has plenty of life in her. She is just getting into her rhythms and will surely unlock more as we delve deeper into x-rays and their role in our universe.
Andrews, Bill. "Milky Way's Black Hole Snacks on Asteroids." Astronomy Jun. 2012: 18. Print.
"Chandra Observatory Catches Giant Black Hole Rejecting Material." Astronomy.com. Kalmbach Publishing Co., 30 Aug. 2013. Web. 30 Sept. 2014.
Chandra X-Ray Center. "Chandra finds intriguing member of black hole family tree." Astronomy.com. Kalmbach Publishing Co., 27 Feb. 2015. Web. 07 Mar. 2015.
---. " Chandra Sees Eclipsing Planet in X-rays for the First Time." Astronomy.com. Kalmbach Publishing Co., 30 Jul. 2013. Web. 07 Feb. 2015.
---. “Black hole growth found to be out of sync.” Astronomy.com. Kalmbach Publishing Co., 12 Jun. 2013. Web. 24 Feb. 2015.
---. "Chandra X-ray Observatory Finds Planet That Makes Star Act Deceptively Old." Astronomy.com. Kalmbach Publishing Co., 17 Sept. 2014. Web. 29 Oct. 2014.
---. “Revealing a Mini-Supermassive Black Hole.” Astronomy.com. Kalmbach Publishing Co., 25 Oct. 2012. Web. 14 Jan. 2016.
Choi, Charles Q. “Black Hole’s Winds Much Stronger Than Previously Thought.” HuffingtonPost.com. Huffington Post., 02 Mar. 2014. Web. 05 Apr. 2015.
Francis, Matthew. “6-Billion-Year-Old Quasar Spinning Nearly as Fast as Physically Possible.” ars technical. Conde Nast, 05 Mar, 2014. Web. 12 Dec. 2014.
Haynes, Korey. "Black Hole's Record-Setting Burst." Astronomy May 2015: 20. Print.
JPL. “Overfed Black Holes Shut Down Galactic Star-Making.” Astronomy.com. Kalmbach Publishing Co., 10 May 2012. Web. 31 Jan. 2015.
Klesuis, Michael. "Super X-Ray Vision." National Geographic Dec. 2002: 46. Print.
Kunzig, Robert. “X-Ray Visions.” Discover Feb. 2005: 38-42. Print.
Moskowitz, Clara. "Milky Way's Black Hole Spits Out Most Of The Gas It Consumes, Observations Show." The Huffington Post. TheHuffingtonPost.com, 01 Sept. 2013. Web. 29 Apr. 2014.
NASA. "Chandra Sees Remarkable Outburst From Old Black Hole. Astronomy.com. Kalmbach Publishing Co, May 01 2012. Web. Oct. 25, 2014.
- - - . "Chandra Finds Milky Way's Black Hole Grazing on Asteroids." Astronomy.com. Kalmbach Publishing Co., 09 Feb. 2012. Web. 15 Jun. 2015.
Powell, Corey S. "When a Slumbering Giant Awakens." Discover Apr. 2014: 69. Print.
Timmer, John. “Black Holes Cheat on the Eddington Limit to Export Extra Energy.” ars technica. Conte Nast., 28 Feb. 2014. Web. 05 Apr. 2015.
- What is the Cassini-Huygens Probe?
Before Cassini-Huygens blasted into outer space, only 3 other probes had visited Saturn. Pioneer 10 was the first in 1979, beaming back only pictures. In the 1980’s, Voyagers 1 and 2 also went by Saturn, taking limited measurements as they...
- How Was the Kepler Space Telescope Made?
Johannes Kepler discovered the Three Planetary Laws that define orbital motion, so it is only fitting that the telescope used to find exoplanets bears his namesake. As of Feruary 1, 2013, 2321 exoplanet candidates have been found and 105 have been...
Questions & Answers
© 2013 Leonard Kelley | 0.934227 | 3.883051 |
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