From The Unique Vantage Point Of About 25,000 Feet Above Earth, Our Associate Administrator Of Science

Ainda estamos em 2015!! hahahah...

Terça, 36 de dezembro de 2015.

Nessa semana, aqui em Parintins, costuma ser bastante movimentado.

Porém, devido a pandemia, quando eu fui comprar pão no final da tarde de ontem. Eu percebi que a cidade estava irreconhecível... Sem visitantes, sem sons de toadas, sem alegorias.

What is Gravitational Lensing?

A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. This effect is known as gravitational lensing, and the amount of bending is one of the predictions of Albert Einstein’s general theory of relativity.

This illustration shows how gravitational lensing works. The gravity of a large galaxy cluster is so strong, it bends, brightens and distorts the light of distant galaxies behind it. The scale has been greatly exaggerated; in reality, the distant galaxy is much further away and much smaller. Credit: NASA, ESA, L. Calcada

There are three classes of gravitational lensing:

1° Strong lensing: where there are easily visible distortions such as the formation of Einstein rings, arcs, and multiple images.

Einstein ring. credit: NASA/ESA&Hubble

2° Weak lensing: where the distortions of background sources are much smaller and can only be detected by analyzing large numbers of sources in a statistical way to find coherent distortions of only a few percent. The lensing shows up statistically as a preferred stretching of the background objects perpendicular to the direction to the centre of the lens. By measuring the shapes and orientations of large numbers of distant galaxies, their orientations can be averaged to measure the shear of the lensing field in any region. This, in turn, can be used to reconstruct the mass distribution in the area: in particular, the background distribution of dark matter can be reconstructed. Since galaxies are intrinsically elliptical and the weak gravitational lensing signal is small, a very large number of galaxies must be used in these surveys.

The effects of foreground galaxy cluster mass on background galaxy shapes. The upper left panel shows (projected onto the plane of the sky) the shapes of cluster members (in yellow) and background galaxies (in white), ignoring the effects of weak lensing. The lower right panel shows this same scenario, but includes the effects of lensing. The middle panel shows a 3-d representation of the positions of cluster and source galaxies, relative to the observer. Note that the background galaxies appear stretched tangentially around the cluster.

3° Microlensing: where no distortion in shape can be seen but the amount of light received from a background object changes in time. The lensing object may be stars in the Milky Way in one typical case, with the background source being stars in a remote galaxy, or, in another case, an even more distant quasar. The effect is small, such that (in the case of strong lensing) even a galaxy with a mass more than 100 billion times that of the Sun will produce multiple images separated by only a few arcseconds. Galaxy clusters can produce separations of several arcminutes. In both cases the galaxies and sources are quite distant, many hundreds of megaparsecs away from our Galaxy.

Gravitational lenses act equally on all kinds of electromagnetic radiation, not just visible light. Weak lensing effects are being studied for the cosmic microwave background as well as galaxy surveys. Strong lenses have been observed in radio and x-ray regimes as well. If a strong lens produces multiple images, there will be a relative time delay between two paths: that is, in one image the lensed object will be observed before the other image.

As an exoplanet passes in front of a more distant star, its gravity causes the trajectory of the starlight to bend, and in some cases results in a brief brightening of the background star as seen by a telescope. The artistic concept illustrates this effect. This phenomenon of gravitational microlensing enables scientists to search for exoplanets that are too distant and dark to detect any other way.Credits: NASA Ames/JPL-Caltech/T. Pyle

Explanation in terms of space–time curvature

Simulated gravitational lensing by black hole by: Earther

In general relativity, light follows the curvature of spacetime, hence when light passes around a massive object, it is bent. This means that the light from an object on the other side will be bent towards an observer’s eye, just like an ordinary lens. In General Relativity the speed of light depends on the gravitational potential (aka the metric) and this bending can be viewed as a consequence of the light traveling along a gradient in light speed. Light rays are the boundary between the future, the spacelike, and the past regions. The gravitational attraction can be viewed as the motion of undisturbed objects in a background curved geometry or alternatively as the response of objects to a force in a flat geometry.

A galaxy perfectly aligned with a supernova (supernova PS1-10afx) acts as a cosmic magnifying glass, making it appear 100 billion times more dazzling than our Sun. Image credit: Anupreeta More/Kavli IPMU.

To learn more, click here. 

What are Gravitational Waves?

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.

hough 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.

Since then, many astronomers have studied the timing of pulsar radio emissions and found similar effects, further confirming the existence of gravitational waves. But these confirmations had always come indirectly or mathematically and not through actual 'physical’ contact.

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.

How are gravitational waves detected?

When a gravitational wave passes by Earth, it squeezes and stretches space. LIGO can detect this squeezing and stretching. Each LIGO observatory has two “arms” that are each more than 2 miles (4 kilometers) long. A passing gravitational wave causes the length of the arms to change slightly. The observatory uses lasers, mirrors, and extremely sensitive instruments to detect these tiny changes. Watch the animation below to see how this works!

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. 

Source: LIGO & spaceplace.nasa.gov

Image credit: LIGO/VIRGO (SXS, the Simulating eXtreme Spacetimes) &  NASA/Goddard Space Flight Center

Conjunction: Mars, Venus and Moon

by Stefan Grießinger

Feliz Natal pra vocês!

O povo brasileiro está aguardando se o #BolsonaroVaiCair antes do mês de dezembro desse ano, pois será difícil que ainda seja presidente em 2022.

Asas da Nuvem

No dia 2 de julho de 2018, logo pela manhã, próximo às 10 horas, quando eu fui observar o movimento no centro da cidade, percebi nesse instante um fato curioso que ocorreu no céu.

Logo de imediato, imaginei as possíveis formas que a nuvem poderia assumir, uma delas sendo um anjo e outra sendo uma borboleta. Após refletir nas possíveis formas, lembrei de um conceito que relaciona esses fatos que ocorrem no cotidiano, que é chamado de PAREIDOLIA.

A pareidolia é um fenômeno neuropsicológico que faz reconhecer um objeto familiar em um estímulo aleatório. [...]

O especialista em neuropsicologia Fabrizio Veloso, profissional associado à Sociedade Brasileira de Psicologia (SBP), afirma que: “Essa tendência de encontrar padrões com significado em imagens ou sons aleatórios está relacionada com a capacidade que o nosso cérebro possui de transformar nossas percepções em algo familiar, ou seja, relaciona-se à forma como construímos o mundo ao nosso redor”.

Assim, estímulos visuais – ou sonoros – aleatórios tendem a ser traduzidos, reconhecidos e associados por nossos cérebros a objetos e estímulos familiares. E nada mais familiar para humanos desde a infância do que outros rostos humanos, daí a frequência da identificação de faces onde elas não existem objetivamente. [...]

Se isso acontece com você, fique tranquilo. É absolutamente normal, garante a ciência.

Data de registro: 2 de julho de 2018 às 09:43

Créditos do texto: Sociedade Brasileira de Psicologia (SBP). Disponível em:

Sociedade Brasileira de Psicologia

Pareidolia: você já passou por isso

A Sociedade Brasileira de Psicologia (SBP) trabalha para o desenvolvimento científica da Psicologia, no compartilhamento de informações e de

What’s Up - February 2018

What’s Up For February?

This month, in honor of Valentine’s Day, we’ll focus on celestial star pairs and constellation couples.

Let’s look at some celestial pairs!

The constellations Perseus and Andromeda are easy to see high overhead this month.

According to lore, the warrior Perseus spotted a beautiful woman–Andromeda–chained to a seaside rock. After battling a sea serpent, he rescued her. 

As a reward, her parents Cepheus and Cassiopeia allowed Perseus to marry Andromeda.

The great hunter Orion fell in love with seven sisters, the Pleiades, and pursued them for a long time. Eventually Zeus turned both Orion and the Pleiades into stars.

Orion is easy to find. Draw an imaginary line through his belt stars to the Pleiades, and watch him chase them across the sky forever.

A pair of star clusters is visible on February nights. The Perseus Double Cluster is high in the sky near Andromeda’s parents Cepheus and Cassiopeia.

Through binoculars you can see dozens of stars in each cluster. Actually, there are more than 300 blue-white supergiant stars in each of the clusters.

There are some colorful star pairs, some visible just by looking up and some requiring a telescope. Gemini’s twins, the brothers Pollux and Castor, are easy to see without aid.

Orion’s westernmost, or right, knee, Rigel, has a faint companion. The companion, Rigel B, is 500 times fainter than the super-giant Rigel and is visible only with a telescope. 

Orion’s westernmost belt star, Mintaka, has a pretty companion. You’ll need a telescope.

Finally, the moon pairs up with the Pleiades on the 22nd and with Pollux and Castor on the 26th.

Watch the full What’s Up for February Video: 

There are so many sights to see in the sky. To stay informed, subscribe to our What’s Up video series on Facebook.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.