Solar Storm and Space Weather – Frequently Asked Questions

SUN/EARTH

1. What is solar activity?

A model of the sun's magnetic field lines.
The sun is a magnetic variable star that fluctuates on times scales ranging from a fraction of a second to billions of years.
Credits: NASA

Solar flares, coronal mass ejections, high-speed solar wind, and solar energetic particles are all forms of solar activity. All solar activity is driven by the solar magnetic field.

2. What is a solar flare?

SOHO image of the most powerful flare in modern times.
The Sun unleashed a powerful flare on 4 November 2003. The Extreme ultraviolet Imager in the 195A emission line aboard the SOHO spacecraft captured the event.
Credits: ESA&NASA/SOHO

A solar flare is an intense burst of radiation coming from the release of magnetic energy associated with sunspots. Flares are our solar system’s largest explosive events. They are seen as bright areas on the sun and they can last from minutes to hours. We typically see a solar flare by the photons (or light) it releases, at most every wavelength of the spectrum. The primary ways we monitor flares are in x-rays and optical light. Flares are also sites where particles (electrons, protons, and heavier particles) are accelerated.

NASA Goddard heliophysics scientists answer some common questions about the sun, space weather, and how they affect the Earth. This is part one of a two-part series. It addresses: 1. What is space weather? 2. What are coronal mass ejections? 3. What are solar flares? 4. What are solar energetic particles? 5. What causes flares and CMEs?
Credits: NASA/Goddard

3. What is a solar prominence?

a solar prominence eruption with Earth provided for scale.
A solar eruptive prominence as seen in extreme UV light on March 30, 2010 with Earth superimposed for a sense of scale.
Credits: NASA/SDO

A solar prominence (also known as a filament when viewed against the solar disk) is a large, bright feature extending outward from the Sun’s surface. Prominences are anchored to the Sun’s surface in the photosphere, and extend outwards into the Sun’s hot outer atmosphere, called the corona. A prominence forms over timescales of about a day, and stable prominences may persist in the corona for several months, looping hundreds of thousands of miles into space. Scientists are still researching how and why prominences are formed.

The red-glowing looped material is plasma, a hot gas comprised of electrically charged hydrogen and helium. The prominence plasma flows along a tangled and twisted structure of magnetic fields generated by the sun’s internal dynamo. An erupting prominence occurs when such a structure becomes unstable and bursts outward, releasing the plasma.

4. What is a coronal mass ejection or CME?

A CME as seen by the coronographs aboard SOHO on Feb. 27, 2000.
A coronal mass ejection on Feb. 27, 2000 taken by SOHO LASCO C2 and C3. A CME blasts into space a billion tons of particles traveling millions of miles an hour.
Credits: ESA&NASA/SOHO

The outer solar atmosphere, the corona, is structured by strong magnetic fields. Where these fields are closed, often above sunspot groups, the confined solar atmosphere can suddenly and violently release bubbles of gas and magnetic fields called coronal mass ejections. A large CME can contain a billion tons of matter that can be accelerated to several million miles per hour in a spectacular explosion. Solar material streams out through the interplanetary medium, impacting any planet or spacecraft in its path. CMEs are sometimes associated with flares but can occur independently.

5. Does ALL solar activity impact Earth? Why or why not?

An erupting pominence with Earth inset to show scale.
A close-up of an erupting prominence with Earth inset at the approximate scale of the image. Taken on July 1, 2002.
Credits: ESA&NASA/SOHO

Solar activity associated with Space Weather can be divided into four main components: solar flares, coronal mass ejections, high-speed solar wind, and solar energetic particles.Solar flares impact Earth only when they occur on the side of the sun facing Earth. Because flares are made of photons, they travel out directly from the flare site, so if we can see the flare, we can be impacted by it.

  • Coronal mass ejections, also called CMEs, are large clouds of plasma and magnetic field that erupt from the sun. These clouds can erupt in any direction, and then continue on in that direction, plowing right through the solar wind. Only when the cloud is aimed at Earth will the CME hit Earth and therefore cause impacts.
  • High-speed solar wind streams come from areas on the sun known as coronal holes. These holes can form anywhere on the sun and usually, only when they are closer to the solar equator, do the winds they produce impact Earth.
  • Solar energetic particles are high-energy charged particles, primarily thought to be released by shocks formed at the front of coronal mass ejections and solar flares. When a CME cloud plows through the solar wind, high velocity solar energetic particles can be produced and because they are charged, they must follow the magnetic field lines that pervade the space between the Sun and the Earth. Therefore, only the charged particles that follow magnetic field lines that intersect the Earth will result in impacts.

6. What are coronal holes?

The dark shape sprawling across the face of the active Sun is a coronal hole.
The dark shape sprawling across the face of the active Sun is a coronal hole, a low density region extending above the surface where the solar magnetic field opens freely into interplanetary space.
Credits: ESA&NASA/SOHO

Coronal holes are variable solar features that can last for weeks to months. They are large, dark areas (representing regions of lower coronal density) when the sun is viewed in EUV or x-ray wavelengths, sometimes as large as a quarter of the sun’s surface. These holes are rooted in large cells of unipolar magnetic fields on the sun’s surface; their field lines extend far out into the solar system. These open field lines allow a continuous outflow of high-speed solar wind. Coronal holes tend to be most numerous in the years following solar maximum.

7. What is a geomagnetic storm?

An illustration of Earth's magnetic field shielding our planet from solar particles.
An illustration of Earth’s magnetic field shielding our planet from solar particles.
Credit: NASA/GSFC/SVS

The Earth’s magnetosphere is created by our magnetic field and protects us from most of the particles the sun emits. When a CME or high-speed stream arrives at Earth it buffets the magnetosphere. If the arriving solar magnetic field is directed southward it interacts strongly with the oppositely oriented magnetic field of the Earth. The Earth’s magnetic field is then peeled open like an onion allowing energetic solar wind particles to stream down the field lines to hit the atmosphere over the poles. At the Earth’s surface a magnetic storm is seen as a rapid drop in the Earth’s magnetic field strength. This decrease lasts about 6 to 12 hours, after which the magnetic field gradually recovers over a period of several days.

8. What is a sunspot?

An Earth-sized sunspot as seen by Hinode.
An Earth-sized sunspot as seen by Hinode.
Credits: NAOJ/NASA/Hinode

Sunspots, dark areas on the solar surface, contain strong magnetic fields that are constantly shifting. A moderate-sized sunspot is about as large as the Earth. Sunspots form and dissipate over periods of days or weeks. They occur when strong magnetic fields emerge through the solar surface and allow the area to cool slightly, from a background value of 6000 ° C down to about 4200 ° C; this area appears as a dark spot in contrast with the very bright photosphere of the sun. The rotation of these sunspots can be seen on the solar surface; they take about 27 days to make a complete rotation as seen from Earth.

Sunspots remain more or less in place on the sun. Near the solar equator the surface rotates at a faster rate than near the solar poles. Groups of sunspots, especially those with complex magnetic field configurations, are often the sites of solar flares. Over the last 300 years, the average number of sunspots has regularly waxed and waned in an 11-year (on average) solar or sunspot cycle.

9. What is the solar cycle?

Graph showing the observed year-to-year variation in the sunspot number.
The observed year-to-year variation in the sunspot number (a measure of the number of dark spots and sunspot groups seen on the white-light Sun, corrected for observing conditions) spanning the period from the earliest use of the telescope through 2007.
Credits: NASA

The sun goes through periodic variations or cycles of high and low activity that repeat approximately every 11 years. Although cycles as short as 9 years and as long as 14 years have been observed. The solar or sunspot cycle is a useful way to mark the changes in the sun.

10. What is solar maximum and solar minimum?

524990main_faq10_full.jpg
Eleven years in the life of the Sun, spanning most of solar cycle 23, as it progressed from solar minimum to maximum conditions and back to minimum (upper right) again, seen as a collage of ten full-disk images of the lower corona. Of note is the prevalence of activity and the relatively few years when our Sun might be described as “quiet.”
Credits: ESA&NASA/SOHO

Solar minimum refers to a period of several Earth years when the number of sunspots is lowest; solar maximum occurs in the years when sunspots are most numerous. During solar maximum, activity on the Sun and the effects of space weather on our terrestrial environment are high. At solar minimum, the sun may go many days with no sunspots visible. At maximum, there may be several hundred sunspots on any day.

11. What is space weather?

Artist concept of the dynamic conditions in space.
Artist concept of the dynamic conditions in space.
Credits: NASA

The term “space weather” was coined not long ago to describe the dynamic conditions in the Earth’s outer space environment, in the same way that “weather” and “climate” refer to conditions in Earth’s lower atmosphere. Space weather includes any and all conditions and events on the sun, in the solar wind, in near-Earth space and in our upper atmosphere that can affect space-borne and ground-based technological systems and through these, human life and endeavor. Heliophysics is the science of space weather.

12. Does the Sun cause space weather?

525022main_faq12.jpg
Artist illustration of events on the sun changing the conditions in Near-Earth space.
Credits: NASA

Looking at the sky with the naked eye, the sun seems static, placid, and constant. But our sun gives us more than just a steady stream of warmth and light. The sun regularly bathes Earth and the rest of our solar system in energy in the forms of light and electrically charged particles and magnetic fields. The resulting impacts are what we call space weather. The sun is a huge thermo-nuclear reactor, fusing hydrogen atoms into helium and producing million degree temperatures and intense magnetic fields. The outer layer of the sun near its surface is like a pot of boiling water, with bubbles of hot, electrified gas—electrons and protons in a fourth state of matter known as plasma—circulating up from the interior and bursting out into space. The steady stream of particles blowing away from the sun is known as the solar wind. Blustering at 800,000 to 5 million miles per hour, the solar wind carries a million tons of matter into space every second (that’s the mass of Utah’s Great Salt Lake) and reaches well beyond the solar system’s planets. Its speed, density and the magnetic fields associated with that plasma affect Earth’s protective magnetic shield in space (the magnetosphere).

13. Do space weather effects / solar storms affect Earth?

Technological infrastructure affected by space weather events.
Technological and infrastructure affected by space weather events.
Credits: NASA

Modern society depends on a variety of technologies susceptible to the extremes of space weather. Strong electrical currents driven along the Earth’s surface during auroral events disrupt electric power grids and contribute to the corrosion of oil and gas pipelines. Changes in the ionosphere during geomagnetic storms interfere with high-frequency radio communications and Global Positioning System (GPS) navigation. During polar cap absorption events caused by solar protons, radio communications can be compromised for commercial airliners on transpolar crossing routes. Exposure of spacecraft to energetic particles during solar energetic particle events and radiation belt enhancements cause temporary operational anomalies, damage critical electronics, degrade solar arrays, and blind optical systems such as imagers and star trackers.

Human and robotic explorers across the solar system are also affected by solar activity. Research has shown, in a worst-case scenario, astronauts exposed to solar particle radiation can reach their permissible exposure limits within hours of the onset of an event. Surface-to-orbit and surface-to-surface communications are sensitive to space weather storms.

14. What are some real-world examples of space weather impacts?

Aurora are a well-known example of the impacts of space weather events.
Aurora are a well-known example of the impacts of space weather events.
Credits: University of Alaska
  • September 2, 1859, disruption of telegraph service.
  • One of the best-known examples of space weather events is the collapse of the Hydro-Québec power network on March 13, 1989 due to geomagnetically induced currents (GICs). Caused by a transformer failure, this event led to a general blackout that lasted more than 9 hours and affected over 6 million people. The geomagnetic storm causing this event was itself the result of a CME ejected from the sun on March 9, 1989.
  • Today, airlines fly over 7,500 polar routes per year. These routes take aircraft to latitudes where satellite communication cannot be used, and flight crews must rely instead on high-frequency (HF) radio to maintain communication with air traffic control, as required by federal regulation. During certain space weather events, solar energetic particles spiral down geomagnetic field lines in the polar regions, where they increase the density of ionized gas, which in turn affects the propagation of radio waves and can result in radio blackouts. These events can last for several days, during which time aircraft must be diverted to latitudes where satellite communications can be used. No large Solar Energetic Particles events have happened during a manned space mission. However, such a large event happened on August 7, 1972, between the Apollo 16 and Apollo 17 lunar missions. The dose of particles would have hit an astronaut outside of Earth’s protective magnetic field, had this event happened during one of these missions, the effects could have been life threatening.

15. Do scientists expect a huge solar storm in 2013?

A sunspot prediction for solar cycle 24.
A sunspot prediction for solar cycle 24.
Credits: NASA/MSFC

The sun goes through cycles of high and low activity that repeat approximately every 11 years. Solar minimum refers to the several Earth years when the number of sunspots is lowest; solar maximum occurs in the years when sunspots are most numerous. During solar maximum, activity on the sun and the possibility of space weather effects on our terrestrial environment is higher. The next solar maximum is expected in the 2013-2014 time frame. No current observations or data show any impending catastrophic solar event. In fact, scientists believe the intensity of the upcoming coming solar maximum will be similar to the previous maximum in 2002.

We have never been so well prepared for the onset of the next solar cycle. NASA maintains a fleet of Heliophysics spacecraft to monitor the sun, geospace, and the space environment between the sun and the Earth.

NASA cooperates with other U.S. agencies to enable new knowledge in studying the sun and its processes. To facilitate and enable this cooperation, NASA’s Heliophysics Division makes its vast research data sets and models publicly available online to industry, academia, and other civil and military space weather interests. Also provided are publicly available sites for citizen science and space situational awareness through various cell phone and e-tablet applications.

16. How long do space weather events usually last?

Series of images show the progression of and eruptive prominence that lifted off from the Sun on Sept. 15, 2010.
This series of images show the progression of and eruptive prominence that lifted off from the Sun on Sept. 15, 2010. SDO caught the action in extreme ultraviolet light. Prominences are cooler clouds of gases suspended above the Sun by often unstable magnetic forces. Their eruptions are fairly common, but this one was larger and clearer to see than most.
Credits: NASA/SDO/AIA

Solar storms can last only a few minutes to several hours but the affects of geomagnetic storms can linger in the Earth’s magnetosphere and atmosphere for days to weeks.

17. How are space weather events observed?

Instruments aboard NASA's Solar Dynamics Observatory.
Instruments aboard the Solar Dynamics Observatory (SDO). (top) The Helioseismic and Magnetic Imager (HMI) extends the capabilities of the SOHO/MDI instrument with continual full-disk coverage at higher spatial resolution and new vector magnetogram capabilities. (Bottom left) The Atmospheric Imaging Assembly (AIA) images the solar atmosphere in multiple wavelengths to link changes in the surface to interior changes. Data includes images of the Sun in 10 wavelengths every 10 seconds. (bottom right) The Extreme ultraviolet Variability Experiment (EVE) measures the solar extreme ultraviolet (EUV) spectral irradiance to understand variations on the timescales which influence Earth’s climate and near-Earth space.
Credits: NASA

Scientists utilize a variety of ground- and space-based sensors and imaging systems to view activity at various depths in the solar atmosphere. Telescopes are used to detect visible light, ultraviolet light, gamma rays, and X rays. They use receivers and transmitters that detect the radio shock waves created when a CME crashes into the solar wind and produces a shock wave. Particle detectors to count ions and electrons, magnetometers record changes in magnetic fields, and UV and visible cameras observe auroral patterns above the Earth.

NASA Goddard heliophysics scientists answer some common questions about the sun, space weather, and how they affect the Earth. This is part two of a two-part series. It addresses: 1. Do all flares and CMEs affect the Earth? 2. What happens when a flare or CME hits the Earth? 3. How quickly can we feel the effects of space weather? 4. Why are there more flares and CMEs happening now?
Credits: NASA/Goddard

18. What are our current capabilities to predict space weather?

NASA's ever evolving Heliophysics System Observatories.
The Heliophysics System Observatory (HSO) showing current operating missions, missions in development, and missions under study.
Credits: NASA/Goddard

NASA operates a system observatory of Heliophysics missions, utilizing the entire fleet of solar, heliospheric, and geospace spacecraft to discover the processes at work throughout the space environment. In addition to its science program, NASA’s Heliophysics Division routinely partners with other agencies to fulfill the space weather research or operational objectives of the nation.

Presently, this is accomplished with the existing fleet of NOAA satellites and some NASA scientific satellites. Space weather “beacons” on NASA spacecraft provide real-time science data to space weather forecasters. Examples include ACE measurements of interplanetary conditions from the Lagrangian point L1 where objects are never shadowed by the Earth or the Moon; CME alerts from SOHO; STEREO beacon images of the far side of the Sun; and super high-resolution images from SDO. NASA will continue to cooperate with other agencies to enable new knowledge in this area and to measure conditions in space critical to both operational and scientific research.

To facilitate and enable this cooperation, NASA’s makes its Heliophysics research data sets and models continuously available to industry, academia, and other civil and military space weather interests via existing Internet sites. These include the Combined Community Modeling Center (CCMC) and the Integrated Space Weather Analysis System (ISWA) associated with GSFC. Also provided are publicly available sites for citizen science and space situational awareness through various cell phone and e-tablet applications.

Beyond NASA, interagency coordination in space weather activities has been formalized through the Committee on Space Weather, which is hosted by the Office of the Federal Coordinator for Meteorology. This multiagency organization is co-chaired by representatives from NASA, NOAA, DoD, and NSF and functions as a steering group responsible for tracking the progress of the National Space Weather Program.

19. How long have we known about space weather?

465382main_SpWeather-orig_full.jpg
Image showing technology and infrastructure that can be affected by space weather events.
Credits: NASA

Space weather is a relatively new term that combines several research fields. Disruptions of the telegraph system by solar storms were seen in the mid-1800’s. Radio operators knew that the sun interfered with radio transmissions soon after radio was invented in the early 1900’s. Problems (such as outages and loss of data) related to space weather were seen in weather satellites when they began operating in the 1960’s. All of these effects come from the same source (solar activity) and the term “space weather” was used to group the causes and effects into one subject.

20. Have scientists seen changes in the intensity of space weather?

Graph of sunspot cycles over the last century.
Sunspot cycles over the last century. The blue curve shows the cyclic variation in the number of sunspots. Red bars show the cumulative number of sunspot-less days. The minimum of sunspot cycle 23 was the longest in the space age with the largest number of spotless days
Credits: Dibyendu Nandi et al.

On a short time scale, the intensity of space weather is always changing. Conditions can be mild one minute and stormy the next. On longer time scales, space weather varies with the solar cycle. Solar flares, coronal mass ejections and solar energetic particles all increase in frequency as we get closer to solar maximum. High-speed wind streams are more frequent at solar minimum, thus ensuring that space weather is something to watch for no matter where we are in the solar cycle.

21. How strong is solar wind (compared to wind on Earth)?

Computer generated image of the constant flow of solar wind streaming outward from the sun.
Computer generated image of the constant flow of solar wind streaming outward from the sun added to an actual image of the sun’s chromosphere from SOHO.
Credits: ESA&NASA/SOHO

The solar wind is very weak compared to the wind on Earth, though it is much, much faster. When we measure solar wind speeds, we typically get speeds of 1-2 million miles per hour. They end up being weaker because there is very little of it. Solar wind density is usually about 100 particles per cubic inch. Thus, a typical pressure from the solar wind is measure in nanopascals whereas at the Earth’s surface, the atmospheric pressure is 100 kilopascals, and surface winds are about 100 pascals. Since solar wind is measured in nanopascals it is approximately 1000 million times weaker than winds here on Earth.

22. What are the northern and southern lights and are they related to space weather?

Aurora Australis Observed from the International Space Station.
Aurora Australis Observed from the International Space Station: Astronaut photograph of the aurora was acquired on May 29, 2010, with a Nikon D3 digital camera, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 23 crew.
Credits: NASA

An aurora is a natural display of light in the sky that can be seen with the unaided eye at night. An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights. A similar phenomenon in the Southern Hemisphere is called the aurora australis. Auroras are the most visible effect of the sun’s activity on the Earth’s atmosphere.

Most auroras occur in far northern and southern regions. The most common color in an aurora is green. But displays that occur extremely high in the sky may be red or purple. Most auroras occur about 50 to 200 miles above the Earth. Some extend lengthwise across the sky for thousands of miles.

Auroral displays are associated with the solar wind, the continuous flow of electrically charged particles from the sun. When these particles reach the earth’s magnetic field, some get trapped. Many of these particles travel toward the Earth’s magnetic poles. When the charged particles strike atoms and molecules in the atmosphere, energy is released. Some of this energy appears in the form of auroras. Auroras occur most frequently during solar maximum, the most intense phase of the 11-year solar or sunspot cycle. Electrons and protons released by solar storms add to the number of solar particles that interact with the Earth’s atmosphere. This increased interaction produces extremely bright auroras.

23. Who is responsible for predicting space weather and sending alerts when there is solar activity?

The forecast center in NOAA's Space Weather Prediction Center in Boulder, CO.
The forecast center in NOAA’s Space Weather Prediction Center in Boulder, CO.
Credits: NOAA SWPC

NOAA’s Space Weather Prediction Center (SWPC) is the nation’s official source of space weather alerts, watches and warnings. It provides real-time monitoring and forecasting of solar and geophysical events. SWPC is part of the National Weather Service and is one of the nine National Centers for Environmental Prediction.

24. How do you forecast space weather?

Forecasting space weather requires data analysis and the use of numerical models to accurately predict changes in the Earth's sp
Forecasting space weather requires data analysis and the use of numerical models to accurately predict changes in the Earth’s space environment.
Credits: NASA, inset images ESA&NASA/SOHO and NOAA GOES

A good space weather forecast begins with a thorough analysis. Forecasters analyze near-real-time ground- and space-based observations to assess the current state of the solar-geophysical environment (from the sun to the Earth and points in between). Space weather forecasters also analyze the 27-day recurrent pattern of solar activity. Based on a thorough analysis of current conditions, comparing these conditions to past situations, and using numerical models similar to weather models, forecasters are able to predict space weather on times scales of hours to weeks.

25. Why is forecasting space weather important?

Imaging showing impacts of space weather events.
Imaging showing impacts of space weather events.
Credits: NASA

As society’s reliance on technological systems grows, so does our vulnerability to space weather. The ultimate goal in studying space weather is an ability to foretell events and conditions on the Sun and in near-Earth space that will produce potentially harmful societal and economic effects, and to do this adequately far in advance and with sufficient accuracy to allow preventive or mitigating actions to be taken.

26. When do the effects of space weather show up?

Illustration of the various dynamic and constant solar effects on Earth.
Illustration of the various dynamic and constant solar effects on Earth. The two solar constants, sunlight and solar wind, takes 8 minutes and 4 days, respectively, to reach Earth. Arrival times of dynamic solar events such as Flares, solar energetic particles and CMEs, are approximated and range from immediate effect to several days.
Credits: NASA/Berkley

Solar flares (sudden brightenings) affect the ionosphere immediately, with adverse effects upon communications and radio navigation.Solar energetic particles arrive in 20 minutes to several hours, threatening the electronics of spacecraft and unprotected astronauts, as they rise to 10,000 times the quiet background flux.Ejected bulk plasma and its pervading magnetic field arrive in 30 – 72 hours (depending upon initial speed and deceleration) setting off a geomagnetic storm, causing currents to flow in the magnetosphere and particles to be energized. The currents cause atmospheric heating and increased drag for satellite operators; they also induce voltages and currents in long conductors at ground level, adversely affecting pipelines and electric power grids. The energetic particles cause the northern lights, as well as surface and deep dielectric charging of spacecraft; subsequent electrostatic discharge of the excess charge build-up can damage spacecraft electronics. The ionosphere departs from its normal state, due to the currents and the energetic particles, thereby adversely affecting communications and radio navigation.

27. Where can I get more information?

NASA Features

NASA Solar Mission Sites

NASA Heliophysics

28. Sun facts:

The image gives a basic overview of the sun’s parts
The image gives a basic overview of the sun’s parts. The cut-out shows the three major interior zones: the core (where energy is generated by nuclear reactions), the radiative zone (where energy travels outward by radiation through about 70% of the Sun), and the convection zone (where convection currents circulate the Sun’s energy to the surface). The surface features (flare, sunspots and photosphere, chromosphere, and the prominence) are all clipped from actual SOHO images of the Sun.
Credits: ESA&NASA/SOHO

The Sun is a magnetic variable star at the center of our solar system that drives the space environment of the planets, including the Earth. The distance of the Sun from the Earth is approximately 93 million miles. At this distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The Sun has a diameter of about 865,000 miles, about 109 times that of Earth. Its mass, about 330,000 times that of Earth, accounts for about 99.86% of the total mass of the Solar System. About three quarters of the Sun’s mass consists of hydrogen, while the rest is mostly helium. Less than 2% consists of heavier elements, including oxygen, carbon, neon, iron, and others. The Sun is neither a solid nor a gas but is actually plasma. This plasma is tenuous and gaseous near the surface, but gets denser down towards the Sun’s fusion core.

The Sun, as shown by the illustration at right, can be divided into six layers. From the center out, the layers of the Sun are as follows: the solar interior composed of the core (which occupies the innermost quarter or so of the Sun’s radius), the radiative zone, and the convective zone, then there is the visible surface known as the photosphere, the chromosphere, and finally the outermost layer, the corona. 
The energy produced through fusion in the Sun’s core powers the Sun and produces all of the heat and light that we receive here on Earth.

The Sun, like most stars, is a main sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 430–600 million tons of hydrogen each second. The Sun’s hot corona continuously expands in space creating the solar wind, a stream of charged particles that extends to the heliopause at roughly 100 astronomical units. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.

Stars like our Sun shine for nine to ten billion years. The Sun is about 4.5 billion years old, judging by the age of moon rocks. Based on this information, current astrophysical theory predicts that the Sun will become a red giant in about five billion (5,000,000,000) years.

  1. Why didn’t the world end in 2012?For an answer to this and other 2012 questions, please visit the NASA 2012 FAQ page at
    http://www.nasa.gov/topics/earth/features/2012.html.

Should we be concerned about solar storms in 2012? Heliophysicist Alex Young from NASA Goddard Space Flight Center sorts out truth from fiction.
Credit: NASA/Goddard

NASA

 

spacenews

 

3507: Ida à Lua em risco de não cumprir meta de 2024

CIÊNCIA/ESPAÇO/LUA

Neil Armstrong é também o primeiro homem a deixar uma pegada na Lua NASA

A NASA teve de suspender as actividades em dois centros de desenvolvimento devido à detecção de um trabalhador infectado com Covid-19

A pandemia gerada pelo novo coronavírus obrigou a NASA a encerrar dois centros de produção de lançadores – e na indústria aeroespacial já há quem admita que esse encerramento poderá levar a um adiamento do regresso à Lua com missões tripuladas, que a agência espacial dos EUA agendou para 2024.

“Sabemos que vai haver impactos nas missões espaciais da NASA, mas à medida que as nossas equipas têm vindo a trabalhar para ter uma análise completa dos cenários e reduzir riscos, decidimos que a nossa principal prioridade é a saúde e a segurança dos trabalhadores da NASA”, referiu Jim Bridenstine, administrador da NASA, num comunicado citado pela Reuters, que não fornece detalhes sobre o período de suspensão de actividades ou o eventual adiamento da ida à Lua.

Michoud Assembly Facility, Nova Orleães, e o Stennis Space Center, no condado de Hancock são os dois centros afetados pelas medidas agora anunciadas pelos responsáveis da NASA. Por serem considerados centros de desenvolvimento prioritários, estes dois centros não foram abrangidos inicialmente pelas medidas de isolamento, que levaram a maioria dos trabalhadores da NASA a deslocar os respectivos locais de trabalho para casa. Contudo, a deteção de um caso de infecção por Covid-19 entre um dos trabalhadores levou a alargar a lógica de teletrabalho para esses dois centros.

Da actividade dos dois centros agora suspensos depende o desenvolvimento do Space Launch System, que deverá dar a conhecer uma nova geração de lançadores, e ainda a cápsula tripulada que dá pelo nome de Orion, que tem em vista o transporte de humanos para a Lua e, posteriormente, para Marte.

Exame Informática
20.03.2020 às 15h59
Hugo Séneca

 

spacenews

 

Tempestades Solares – III

CIÊNCIA/ASTRONOMIA

Tempestades solares estão acontecendo mais perto da Terra, e isso é um problema

Apesar de bonito, fenómeno pode causar estragos nas redes eléctricas, sistemas de comunicação e satélites

As tempestades solares que criam belíssimas auroras nos pólos da Terra também podem causar estragos. Elas podem afectar redes eléctricas, sistemas de comunicação e satélites. Além disso, um novo estudo sugere que a fonte dessas tempestades está muito mais próxima da Terra do seu se pensava.

O planeta é protegido por uma bolha conhecida como magnetosfera, que bloqueia a radiação solar prejudicial. Porém, quando o Sol ocasionalmente emite fluxos de radiação de alta velocidade, e, com isso, linhas de campo magnético intensas, eles podem interagir fortemente com o campo magnético da Terra.

À medida que esse vento solar atinge a magnetosfera, os dois conjuntos de linhas de campo magnético ficam emaranhados. Essa interacção gera calor e acelera as partículas carregadas trazidas pelo vento solar, enfraquecendo temporariamente o campo magnético do planeta e criando fortes tempestades magnéticas que aparecem como auroras.

Segundo os pesquisadores do novo estudo, o fato de as tempestades serem raras e não existirem satélites suficientes para observá-las, não deixa claro exactamente onde e como acontece a reconexão das linhas de campo magnético.

Para descobrir isso, os pesquisadores usaram observações dos satélites de eventos da NASA e interacções em macro-escala durante as tempestades. Durante as tempestades solares, esses satélites ficam na parte da magnetosfera no lado da Terra que não está voltado para o Sol, que se torna alongada pelo vento solar. Os pesquisadores descobriram que essa reconexão magnética pode ocorrer muito mais perto do planeta do que se pensava: cerca de três a quatro diâmetro da Terra.

Além disso, um satélite climático em órbita próxima à Terra detectou eléctrons energizados após a tempestade, sugerindo que o evento de reconexão levou íons e eléctrons a acelerar a altas energias. Os eléctrons que fluem em direcção ao planeta carregam energia ao longo das linhas do campo magnético para criar as auroras.

Essa aceleração pode ser perigosa para centenas de satélites que se movem em órbita geossíncrona e também pode ser prejudicial ao DNA humano, colocando em risco os astronautas, de acordo com o comunicado.

Além disso, tempestades solares podem afetar os habitantes da Terra de maneiras significativas. Em 1921, por exemplo, uma tempestade magnética interrompeu as comunicações telegráficas e causou falhas de energia que levaram à queima de uma estação de trem na cidade de Nova York, segundo o estudo.

“Ao estudar a magnetosfera, aumentamos nossas chances de lidar com os maiores riscos para a humanidade se aventurar no espaço: tempestades alimentadas pelo Sol”, disse o autor principal, Vassilis Angelopoulos, professor de física espacial da UCLA. Essas descobertas podem ajudar os astronautas e os habitantes da Terra a se prepararem melhor para o clima solar perigoso.

Via: Live Science
Guilherme Preta, editado por Matheus Luque
17/01/2020 10h47

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Tempestades Solares – II

CIÊNCIA/ASTRONOMIA

Cientistas descobriram que uma super tempestade solar atinge a Terra a cada 25 anos

Artigo publicado neste Blogue em 4 de Fevereiro de 2020

Cientistas descobriram que uma super tempestade solar atinge a Terra a cada 25 anos

 

 

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Tempestades Solares – I

CIÊNCIA/ASTRONOMIA

Tempestade solar chegando à Terra? Veja como isso poderia nos afectar

Tempestade solar é um fenómeno que acontece quando um cúmulo de energia do sol é libertado por meio de uma explosão, lançando partículas electromagnéticas. Mas essas tempestades são capazes de chegar até a Terra? E se sim, como elas podem interferir na nossa vida e no planeta?

Para começar, como acontece uma tempestade solar?

O nosso Sol é uma massa de gases que emite radiação de todos os tipos e sofre de constantes variações, como explosões de radiação.

As tempestades solares ocorrem quando um cúmulo de energia magnética no Sol é de repente libertado, gerando uma explosão. Se as tempestades forem particularmente fortes, elas podem vir acompanhadas de ejecções de massa coronal (CMEs), que são enormes nuvens de plasma que viajam a milhões de quilómetros por hora.

Os cientistas classificam as tempestades solares em três categorias: C, M ou X, onde a potência cresce dez vezes de uma classe para a outra.

Como isso pode afectar nossa vida?

As tempestades solares de classe C são mais fracas e não afectam a Terra de forma significativa. As explosões solares de classe M podem gerar breves apagamentos de rádio nos pólos e pequenas tempestades de radiação que podem pôr em perigo os astronautas em órbita. Já as tempestades de classe X podem ter consequências em todo o planeta, provocando apagões de rádio generalizados e longas tempestades de radiação. Entretanto, as CMEs que acompanham frequentemente as chamas solares têm potencial ainda mais destrutivo.

Quando as partículas carregadas de CME interagem com o campo magnético da Terra, elas podem gerar tempestades geo-magnéticas poderosas o suficiente para interromper os sinais GPS, os aparelhos de telecomunicação e as redes eléctricas. Voos também podem ser colocados em perigo, pois o fenómeno pode fazer com que os aviões fiquem incomunicáveis.

Por que isso é um problema maior hoje?

Se antigamente, as tempestades solares já representavam um problema, imagine num mundo onde todos dependemos da tecnologia para tudo!

Em 1921, uma tempestade solar eliminou as comunicações e gerou incêndios no nordeste dos Estados Unidos. Um estudo da Metatech Corporation em 2008 mostrou que se essa tempestade tivesse acontecesse hoje, ela afectaria mais de 130 milhões de pessoas em todo os Estados Unidos. Isso significaria um impacto económico de dois triliões de dólares.

Elas também podem afectar o nosso emocional

Além da influência sobre aparelhos tecnológicos, alguns estudos mostram que as tempestades solares também podem afectar o estado emocional das pessoas.

Uma das explicações mais aceitas é de que as tempestades solares dessincronizam nosso ritmo circadiano, que seria nosso relógio biológico. Isso acontece porque a glândula pineal no nosso cérebro é afectada pela actividade electromagnética.

De acordo com o professor Raymond Wheeler, da Universidade de Kansas, as tempestades solares também teriam sido causas directas de conflitos e até guerras. Wheeler estudou sobre como a violência em certas épocas podiam ser comparadas com os ciclos solares, que ocorrem a cada 11 anos.

Os resultados mostraram que, à medida que o ciclo do sol atingiu o pico, houve um aumento nas revoltas, rebeliões, revoluções e guerras entre as nações.

Quando Wheeler comparou as suas descobertas com a história humana, ele encontrou um padrão surpreendente que pode ser rastreado em até 2.500 anos.

Mas nem tudo são problemas

Uma pesquisa da NASA indica que as tempestades solares podem ter ajudado a criar a vida na Terra, descongelando a superfície do planeta. Além disso, cientistas apontam que essas tempestades podem ter propiciado outras condições para o desenvolvimento da vida, ajudando a formar o RNA e DNA.

E quando será a próxima tempestade solar?

As tempestades solares podem acontecer a qualquer momento, mas tendem a tornar-se mais severas e mais frequentes em ciclos de aproximadamente 11 anos.

De acordo com um estudo da Universidade de Denver, publicado pela revista Space Weather, uma tempestade solar de grande magnitude poderá ocorrer em 2020.

hipercultura

 

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3503: Cientistas descobrem o primeiro remanescente pulsante de uma estrela num sistema binário eclipsante

CIÊNCIA/ASTRONOMIA

Impressão de artista de um sistema binário com uma anã branca acretando matéria da sua companheira.
Crédito: ESO/M. Kornmesser

Cientistas da Universidade de Sheffield descobriram uma antiga estrela pulsante num sistema binário, o que lhes permite aceder a informações importantes sobre a história de como estrelas como o nosso Sol evoluem e eventualmente morrem.

A descoberta da primeira estrela anã branca pulsante num binário eclipsante, por físicos da Universidade de Sheffield, significa que a equipa pode ver, pela primeira vez e em detalhe, como a evolução binária afectou a estrutura interna de uma anã branca.

Um binário eclipsante, ou sistema estelar duplo, é constituído por duas estrelas que se orbitam uma à outra e que passam periodicamente uma à frente da outra, a partir da perspectiva da Terra.

As anãs brancas são os núcleos queimados deixados para trás quando uma estrela como o Sol morre. Esta anã branca em particular pode fornecer, pela primeira vez, informações importantes sobre a estrutura, evolução e morte destas estrelas.

Pensa-se que a maioria das anãs brancas sejam compostas principalmente de carbono e oxigénio, mas esta anã em particular é composta principalmente de hélio. A equipa pensa que isso é resultado da companheira binária ter interrompido a sua evolução cedo, antes de ter hipótese de fundir o hélio em carbono e oxigénio.

Os pulsos desta estrela foram descobertos usando a HiPERCAM, uma revolucionária câmara de alta velocidade desenvolvida por uma equipa liderada pelo professor Vik Dhillon do Departamento de Física e Astronomia da Universidade de Sheffield.

A HiPERCAM pode captar uma imagem a cada milissegundo em cinco cores diferentes simultaneamente e está acoplada ao GTC (Gran Telescopio Canarias) de 10,4 metros, o maior telescópio óptico do mundo em La Palma. Isto permitiu que os cientistas detectassem os pulsos rápidos e subtis desta anã branca em particular.

Os pulsos da anã branca e do sistema binário eclipsante permitiram à equipa investigar a sua estrutura usando duas técnicas, asteros-sismologia e estudos de eclipses. A asteros-sismologia envolve a medição da rapidez com que as ondas sonoras viajam através da anã branca.

O Dr. Steven Parsons, que liderou o estudo e do mesmo departamento, disse: “A determinação da composição de uma anã branca não é simples porque estes objectos têm aproximadamente metade da massa do Sol e aproximadamente o tamanho da Terra. Isto significa que a gravidade é extremamente forte numa anã branca, cerca de um milhão de vezes maior do que aqui na Terra, de modo que à superfície de uma anã branca uma pessoa média pesaria 60 milhões de quilogramas. A gravidade faz com que todos os elementos pesados da anã branca afundem para o centro, deixando apenas os elementos mais leves na superfície e, portanto, a verdadeira composição permanece oculta por baixo.

“Esta anã branca pulsante que descobrimos é extremamente importante, pois podemos usar o movimento binário e o eclipse para medir independentemente a massa e o raio desta anã branca, o que nos ajuda a determinar a sua composição. Ainda mais interessante, as duas estrelas neste sistema binário interagiram uma com a outra no passado, transferindo material para a frente e para trás. Podemos ver como esta evolução binária afectou a estrutura interna da anã branca, algo que não conseguimos fazer antes para este tipo de sistemas binários.”

O próximo passo da investigação é continuar a observar a anã branca para registar o maior número possível de pulsos usando a HiPERCAM e o Telescópio Espacial Hubble.

Astronomia On-line
20 de Março de 2020

 

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3502: Equipa descobre método de aprimorar imagens de buracos negros

CIÊNCIA/ASTRONOMIA

A imagem de um buraco negro tem um anel brilhante de emissão em redor de uma “sombra” provocada pelo objecto monstruoso. Este anel é composto de uma série de sub-anéis cada vez mais nítidos que correspondem ao número de órbitas que os fotões deram antes de chegar ao observador.
Crédito: George Wong (UIUC) e Michael Johnson (CfA)

No passado mês de Abril, o EHT (Event Horizon Telescope) despertou entusiasmo internacional ao revelar a primeira imagem de um buraco negro. E agora uma equipa de investigadores publicou novos cálculos que preveem uma subestrutura impressionante e intrincada nas imagens de buracos negros devido à extrema curvatura gravitacional da luz.

“A imagem de um buraco negro na verdade contém uma série aninhada de anéis,” explica Michael Johnson do Centro para Astrofísica de Harvard e Smithsonian. “Cada anel sucessivo tem aproximadamente o mesmo diâmetro, mas torna-se cada vez mais nítido porque a sua luz orbitou o buraco negro mais vezes antes de chegar ao observador. Com a imagem actual do EHT, captámos apenas um vislumbre de toda a complexidade que deve surgir na imagem de qualquer buraco negro.”

Dado que os buracos negros capturam todos os fotões que cruzam o seu horizonte de eventos, lançam uma sombra na sua brilhante emissão circundante do gás quente presente. Um “anel de fotões” envolve esta sombra, produzida a partir da luz que é concentrada pela forte gravidade próxima do buraco negro. Este anel de fotões transporta a impressão digital do buraco negro – o seu tamanho e forma codificam a massa e a rotação do buraco negro. Com as imagens EHT, os investigadores de buracos negros têm uma nova ferramenta para estudar estes objectos extraordinários.

“Este é um momento extremamente emocionante para se pensar na física dos buracos negros,” diz Daniel Kapec, membro da Escola de Ciências Naturais do Instituto de Estudos Avançados. “A teoria da relatividade geral de Einstein faz uma série de previsões impressionantes para os tipos de observações que finalmente estão a chegar ao nosso alcance, e penso que podemos esperar muitos avanços nos próximos anos. Como teórico, acho a rápida convergência entre teoria e experiências especialmente gratificante e espero que possamos continuar a isolar e a observar previsões mais universais da relatividade geral à medida que estas experiências se tornam mais sensíveis.”

A equipa de investigação inclui astrónomos observacionais, físicos teóricos e astrofísicos.

“Reunir especialistas de diferentes áreas permitiu-nos realmente ligar um entendimento teórico do anel de fotões com o que é possível com a observação,” observa George Wong, estudante de física da Universidade de Illinois em Urbana-Champaign. Wong desenvolveu um software para produzir imagens simuladas de buracos negros em resoluções mais altas do que as calculadas anteriormente e para decompor estas imagens na série prevista de sub-imagens. “O que começou como cálculos clássicos de lápis e papel levou-nos a empurrar as nossas simulações a novos limites.”

Os cientistas também descobriram que a subestrutura da imagem do buraco negro cria novas possibilidades para observar buracos negros. “O que realmente nos surpreendeu foi que, enquanto as subestruturas aninhadas são quase imperceptíveis a olho nu nas imagens – mesmo em imagens perfeitas – são sinais fortes e claros em redes de telescópios chamadas interferómetros,” realça Johnson. “Embora a captura de imagens de buracos negros normalmente exija muitos telescópios distribuídos, os sub-anéis são perfeitos para estudar usando apenas dois telescópios separados por grandes distâncias. Adicionar um telescópio espacial ao EHT seria suficiente.”

“A física dos buracos negros sempre foi um assunto sublime, com profundas implicações teóricas,” diz Alex Lupsasca da Sociedade de Harvard. “Como teórico, tenho o prazer de finalmente recolher dados reais sobre estes objectos nos quais temos vindo a pensar abstractamente há tanto tempo.”

Astronomia On-line
20 de Março de 2020

 

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3501: Asteróide Ryugu é provavelmente um elo na formação planetária

CIÊNCIA/ASTRONOMIA

Ampliação do asteróide Ryugu.
Crédito: JAXA, Universidade de Tóquio, Universidade de Kochi, Universidade de Rikkyo, Universidade de Nagoya, Instituto de Tecnologia de Chiba, Universidade de Meiji, Universidade de Aizu, AIST, Universidade de Kobe, Universidade de Auburn

O Sistema Solar foi formado há aproximadamente 4,5 mil milhões de anos atrás. Muitos fragmentos, testemunhas dessa era primitiva, orbitam o Sol como asteróides. Cerca de três-quartos são asteróides do tipo C, ricos em carbono, como 162173 Ryugu, que foi o alvo da missão japonesa Hayabusa2 em 2018 e 2019. A nave está actualmente na sua viagem de regresso à Terra. Inúmeros cientistas, incluindo investigadores planetários do Centro Aeroespacial Alemão (DLR), estudaram intensivamente esta “pilha cósmica de entulho”, que tem quase um quilómetro de diâmetro e que pode passar perto da Terra. As imagens infravermelhas obtidas pela Hayabusa2 foram agora publicadas na revista científica Nature. Mostram que o asteróide consiste quase inteiramente de material altamente poroso. Ryugu foi formado em grande parte a partir de fragmentos de um corpo parental destruído por impactos. A alta porosidade e a baixa força mecânica associada dos fragmentos rochosos que compõem Ryugu garantem que estes corpos se dividem em numerosos fragmentos ao entrar na atmosfera da Terra. Por esta razão, os meteoritos ricos em carbono são muito raramente encontrados na Terra e a atmosfera tende a fornecer uma maior protecção contra eles.

O comportamento térmico revela densidade

Esta investigação das propriedades globais de Ryugu confirma e complementa os achados do ambiente de aterragem em Ryugu obtidos pelo “lander” alemão-francês MASCOT (“Mobile Asteroid Surface SCOuT”) durante a missão Hayabusa2. “Os asteróides frágeis e altamente porosos como Ryugu são provavelmente o elo na evolução da poeira cósmica para corpos celestes massivos,” diz Matthias Grott do Instituto de Pesquisa Planetária do DLR, que é um dos autores da publicação actual da Nature. “Isto fecha uma lacuna no nosso entendimento da formação planetária, já que quase nunca conseguimos detectar esse material nos meteoritos encontrados na Terra.”

No outono de 2018, os cientistas que trabalhavam com o autor principal Tatsuaki Okada da agência espacial japonesa JAXA analisaram a temperatura da superfície do asteróide em várias séries de medições realizadas com o instrumento TIR (Thermal Infrared Imager) a bordo da Hayabusa2. Estas medições foram feitas na faixa de comprimento de onda de 8 a 12 micrómetros durante os ciclos diurno e nocturno. No processo, descobriram que, com muito poucas excepções, a superfície aquece muito rapidamente quando exposta à luz solar. “O rápido aquecimento após o nascer-do-Sol, de aproximadamente -43º C para 27º C, sugere que as partes constituintes do asteróide têm baixa densidade e alta porosidade,” explica Grott. Cerca de 1% das rochas à superfície eram mais frias e mais parecidas com os meteoritos encontrados na Terra. “Estes podem ser fragmentos mais massivos do interior de um corpo parente original, ou podem ter vindo de outras fontes e caído sobre Ryugu,” acrescenta Jörn Helbert do Instituto de Pesquisa Planetária do DLR, que também é um dos autores da publicação da Nature.

De planetesimais a planetas

A frágil estrutura porosa dos asteróides de tipo C pode ser semelhante à dos planetesimais, formados na nebulosa solar primordial e acretados durante inúmeras colisões para formar planetas. A maior parte da massa em colapso da nuvem pré-solar de gás e poeira acumulou-se no jovem Sol. Quando foi atingida uma massa crítica, o processo de criação de calor da fusão nuclear começou no seu núcleo.

A poeira, o gelo e o gás restantes acumularam-se num disco de acreção giratório em torno da estrela recém-formada. Através dos efeitos da gravidade, os primeiros embriões planetários ou planetesimais foram formados nestes discos há aproximadamente 4,5 mil milhões de anos. Os planetas e as suas luas formaram-se a partir destes planetesimais após um período comparativamente curto de talvez apenas 10 milhões de anos. Muitos corpos menores – asteróides e cometas – permaneceram. Estes não foram capazes de se aglomerar para formar planetas adicionais devido a distúrbios gravitacionais, particularmente os provocados por Júpiter – de longe o maior e mais massivo planeta.

No entanto, os processos que ocorreram durante o início da história do Sistema Solar ainda não são totalmente compreendidos. Muitas teorias são baseadas em modelos e ainda não foram confirmadas por observações, em parte porque os traços destes tempos iniciais são raros. “Portanto, a pesquisa sobre o assunto depende principalmente de matéria extraterrestre, que atinge a Terra das profundezas do Sistema Solar na forma de meteoritos,” explica Helberg. Contém componentes da época em que o Sol e os planetas foram formados. “Além disso, precisamos de missões como a Hayabusa2 para visitar os corpos menores que se formaram durante os estágios iniciais do Sistema Solar, a fim de confirmar, complementar ou – com observações apropriadas – refutar os modelos.”

Uma rocha como muitas em Ryugu

Já no verão de 2019, os resultados da missão do “lander” MASCOT haviam mostrado que o seu local de pouso em Ryugu era povoado principalmente por rochas grandes, altamente porosas e frágeis. “Os resultados publicados são uma confirmação dos resultados dos estudos realizados pelo radiómetro MARA do DLR no MASCOT,” disse Matthias Grott, investigador principal do MARA. “Foi agora demonstrado que a rocha analisada pelo MARA é típica para toda a superfície do asteróide. Isto também confirma que fragmentos de asteróides comuns do tipo C como Ryugu provavelmente quebram-se facilmente devido à baixa força interna ao entrar na atmosfera da Terra.”

No dia 3 de Outubro de 2018, o MASCOT aterrou em Ryugu, em queda livre mas ao ritmo de uma caminhada. Após o pouso, “saltou” vários metros adiante, antes que o pacote de experiências com aproximadamente 10 kg parasse. O MASCOT moveu-se à superfície com a ajuda de um braço giratório. Isto tornou possível girar o MASCOT no lado “direito” e até executar saltos à superfície do asteróide devido a baixa atracção gravitacional de Ryugu. No total, o MASCOT realizou experiências em Ryugu durante aproximadamente 17 horas.

Amostras do asteróide Ryugu a caminho da Terra

A Hayabusa2 mapeou o asteróide a partir de orbita e a alta resolução e, posteriormente, adquiriu amostras do corpo primordial em dois locais de pouso. Actualmente, estão seladas numa cápsula de transporte e estão a viajar para a Terra com a nave espacial. A cápsula tem aterragem prevista na Austrália no final de 2020. Até agora, os investigadores assumem que o material de Ryugu é quimicamente semelhante ao dos meteoritos condritos, que também são encontrados na Terra. Os côndrulos são pequenas esferas rochosas de tamanho milimétrico, que se formaram na nebulosa solar primordial há 4,5 mil milhões de anos e são considerados os blocos de construção da formação planetária. No entanto, até agora os cientistas não podem descartar a possibilidade de serem feitos de material rico em carbono, como os encontrados no cometa 67P/Churyumov-Gerasimenko como parte da missão Rosetta da ESA, com o módulo Philae, operado pelo DLR. As análises das amostras de Ryugu, algumas das quais serão realizadas no DLR, são aguardadas com grande expectativa. “É precisamente para esta tarefa – e, é claro, para futuras missões como a missão japonesa MMX (Martian Moons eXploration), na qual amostras extraterrestres serão trazidas para a Terra – que nós, no Instituto de Pesquisa Planetária do DLR em Berlim, começámos a configurar o SAL (Sample Analysis Laboratory) no ano passado,” diz Helbert. A missão da MMX, na qual o DLR participa, voará para as luas marcianas Fobos e Deimos em 2024 e regressará à Terra com amostras das luas do tamanho de asteróides em 2029. Um veículo móvel alemão-francês também fará parte da missão da MMX.

Astronomia On-line
20 de Março de 2020

 

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‘Infinite subrings’ may be next frontier for photographing black holes

SCIENCE/ASTRONOMY

Peering so deeply would require adding a space component to the Event Horizon Telescope.

The Event Horizon Telescope captured this image of the supermassive black hole and its shadow that’s in the center of the galaxy M87.
(Image: © Event Horizon Telescope Collaboration)

Black-hole photography could be even more powerful and revelatory than scientists had thought.

Last April, the Event Horizon Telescope (EHT) project unveiled the first-ever imagery of a black hole, laying bare the supermassive monster at the heart of the galaxy M87. The landmark photos have opened new doors, allowing scientists to probe exotic space-time realms like never before.

And that probing may go much deeper still in the not-too-distant future. The most prominent feature in the EHT imagery, a bright but unresolved ring around M87’s supermassive black hole, likely contains a thin “photon ring” that  is composed of an infinite sequence of subrings, a new study reports.

The intricate structure of this photon ring holds a treasure trove of information about the black hole — information that scientists can access by extending the EHT’s reach a bit, study team members said.

“Black holes are giving us this gift, this signal unlike anything that’s been studied in astronomy,” said lead author Michael Johnson, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

“It’s not just some cheap picture of, ‘We understand black holes better,'” Johnson told Space.com. “It’s actually enabling a whole new way to measure them.”

Put a ring on it

The EHT is a network of eight radio telescopes around the world, which are linked to form a virtual instrument the size of Earth — a technique known as very-long-baseline interferometry (VLBI).

This megascope has been observing two supermassive black holes. One is the M87 beast, which lies 53.5 million light-years from Earth and is about 6.5 billion times more massive than Earth’s sun. The other is the Milky Way’s central black hole, known as Sagittarius A*, which is 26,000 light-years away and harbors “only” 4.3 million solar masses.

The EHT team looked first at M87’s black hole, which is a bit easier to resolve because it’s less variable over short timescales. The project hopes to get imagery of Sagittarius A* soon as well, EHT team members have said.

Such imagery doesn’t depict the interior of a black hole, of course; that’s impossible to pull off without being inside a black hole, because these objects gobble up light. Rather, the EHT provides a silhouette of the black hole, mapping out its event horizon, the point of no return beyond which nothing can escape.

The EHT imagery shows that the silhouette of the M87 black hole is surrounded by a bright ring of emission — photons shot out by the hot, fast-moving plasma swirling around the supermassive object. In the new study, Johnson and his colleagues suggest that this ring is a rich resource for astronomers to mine.

Einstein’s theory of general relativity predicts that embedded within the emission halo is a “photon ring,” which itself consists of a complex nest of infinite subrings, the researchers determined.

“Together, the set of subrings are akin to the frames of a movie, capturing the history of the visible universe as seen from the black hole,” Johnson and his colleagues wrote in the new paper, which was published online today (March 18) in the journal Science Advances.

Watching that “movie” could reveal key but elusive insights about black holes and the nature of gravity, the researchers said. For example, characterizing the subrings in detail could help scientists nail down a black hole’s mass and spin, the two properties that define these exotic objects.

“Once you know these two parameters about the system, we think you know everything there is to know about the black hole,” Johnson said.

EHT observations currently allow calculation of black hole masses within 10% or so of the actual value, he added, and they don’t reveal much about spin. But taking the project off Earth could change things significantly.

A telescope bigger than Earth

The EHT consortium, an international team of about 200 researchers, has long planned to push the array into the final frontier eventually, provided their funding will allow it. After all, bigger telescopes, including those linked via VLBI, are more powerful.

But this prospect has long seemed daunting, as calculations have indicated it would take at least half a dozen space-based components to appreciably improve the EHT’s resolving power, Johnson said.

The new study, however, suggests that reading the subrings won’t require such a significant outlay of resources. The researchers determined that even a single satellite — or just one properly designed instrument aboard a parent spacecraft — would likely do the trick, provided it extended the EHT’s footprint far enough out into space.

“Even, say, at geosynchronous orbit — that’s a big resolution improvement for the EHT,” Johnson said, referring to the swath of space about 22,200 miles (35,730 kilometers) above Earth’s surface. “And then, certainly, once you get out to the moon — that’s where I think we would really be looking at entirely new science.”

The subring signatures should be quite easy for a properly extended EHT to measure, he added.

“They seem almost magical,” Johnson said. “We went from this situation where it was sort of unimaginable to even increase the resolution of EHT images by a factor of two. And now we’re thinking, by adding a single space-based line that’s very long, we might be able to increase EHT resolution by a factor of 100.”

This potential milestone isn’t just around the corner, but it may not be too far off, either; Johnson said that the EHT could get a space component within 10 years or so, if everything breaks the project’s way.

Mike Wall is the author of “Out There” (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.

livescience
By Mike Wall – Space.com Senior Writer
19/03/2020

 

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