Chandra Spots Extremely Long Cosmic Jet In Early Universe

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7 Fascinating Facts About 2019’s Only Total Solar Eclipse

“3.) Optimally situated viewers will experience 4 minutes and 33 seconds of totality. With Earth near aphelion and the Moon near perigee, it’s nearly twice the duration of 2017’s eclipse.”

On July 2, 2019, the world will experience a total solar eclipse: the only one of the year. Unlike the famous 2017 solar eclipse which spanned the continental United States, this year’s total solar eclipse occurs almost exactly coincident with both lunar perigee, where the Moon is closest to Earth, and solar aphelion, where the Sun is at its farthest point from Earth. July 2nd is just 2 days before our annual aphelion and 3 days before our monthly perigee, meaning that we’ll get 4 minutes and 33 seconds of totality during maximum eclipse: nearly twice as long as 2017′s maximum totality and the longest total solar eclipse we’ll experience until 2027.

What will we learn? What will we see? And how can you observe it from anywhere in the world? Find out these and more amazing facts before the eclipse passes!

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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. 

Lunar eclipse 2019 

Image credit: Dan Wery

The Summer Solstice Has Arrived!

This year’s summer solstice for the northern hemisphere arrives at 11:54 a.m. EDT, meaning today is the longest day of the year! The number of daylight hours varies by latitude, so our headquarters in Washington, D.C. will see 14 hours, 53 minutes, and 51 seconds of daylight. A lot can happen in that time! Let’s find out more.

If you’re spending the day outside, you might be in the path of our Earth Science Satellite Fleet (ESSF)! The fleet, made up of over a dozen Earth observation satellites, will pass over the continental United States about 37 times during today’s daylight hours. 

These missions collect data on atmospheric chemistry and composition, cloud cover, ocean levels, climate, ecosystem dynamics, precipitation, and glacial movement, among other things. They aim to do everything from predicting extreme weather to helping informing the public and decision makers with the environment through GPS and imaging. Today, their sensors will send back over 200 gigabytes (GB) of data back to the ground by sunset. 

As the sun sets today, the International Space Station (ISS) will be completing its 10th orbit since sunrise. In that time, a little more than 1 terabyte-worth of data will be downlinked to Earth.

That number encompasses data from ground communications, payloads, experiments, and control and navigation signals for the station. Approximately 330 GB of that TB is video, including live broadcasts and downlinks with news outlets. But as recently-returned astronaut Serena Auñón-Chancellor likes to point out, there’s still room for fun. The astronauts aboard the ISS can request YouTube videos or movies for what she likes to call “family movie night.”

Astronauts aboard the station also send back images—LOTS of them. Last year, astronauts sent back an average of 66,912 images per month! During today’s long hours of daylight, we expect the crew to send back about 656 images. But with Expedition 59 astronauts David Saint-Jacques (CSA), Anne McClain (NASA), and Oleg Kononenko (RKA) hard at work preparing to return to Earth on Monday, that number might be a little less. 

Say you’re feeling left out after seeing the family dinners and want to join the crew. Would you have enough daylight to travel to the ISS and back on the longest day of the year? Yes, but only if you’re speedy enough, and plan your launch just right. With the current fastest launch-to-docking time of about six hours, you could complete two-and-a-half flights to the ISS today between sunrise and sunset.

When returning from orbit, it’s a longer ordeal. After the Expedition 59 trio arrives on Earth Monday night, they’ll have to travel from Kazakhstan to Houston to begin their post-flight activities. Their journey should take about 18 hours and 30 minutes, just a few hours longer than the hours of daylight we’ll see today.

Happy solstice! Make sure to tune in with us on Monday night for live coverage of the return of Expedition 59. Until then, enjoy the longest day of the year!

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

I love the sky colors ☀️ 🌤❤️