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By NASA
This full-disk image from NOAA’s GOES-13 satellite shows the Americas at the start of astronomical summer in the Northern Hemisphere on June 21, 2012.NASA This full-disk image from NOAA’s GOES-13 satellite was captured at 7:45 a.m. EDT (11:45 UTC) and shows the Americas on June 21, 2012, the start of astronomical summer – in the Northern Hemisphere – that year.
The first day of summer in 2025 is June 20; it is also the longest day of the year. In the Southern Hemisphere, it’s the shortest day of the year and the beginning of winter.
Earth orbits at an angle, so the Northern Hemisphere is tilted toward the Sun half of the year — this is summer in the Northern Hemisphere, and winter in the Southern Hemisphere. The other half of the year, the Northern Hemisphere is tilted away from the Sun, creating winter in the north and summer in the south. Solstices happen twice per year, at the points in Earth’s orbit where this tilt is most pronounced.
Image credit: NASA
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By NASA
Did you know some of the brightest sources of light in the sky come from the regions around black holes in the centers of galaxies? It sounds a little contradictory, but it’s true! They may not look bright to our eyes, but satellites have spotted oodles of them across the universe.
One of those satellites is NASA’s Fermi Gamma-ray Space Telescope. Fermi has found thousands of these kinds of galaxies since it launched in 2008, and there are many more out there!
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Watch a cosmic gamma-ray fireworks show in this animation using just a year of data from the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope. Each object’s magenta circle grows as it brightens and shrinks as it dims. The yellow circle represents the Sun following its apparent annual path across the sky. The animation shows a subset of the LAT gamma-ray records available for more than 1,500 objects in a continually updated repository. Over 90% of these sources are a type of galaxy called a blazar, powered by the activity of a supermassive black hole. NASA’s Marshall Space Flight Center/Daniel Kocevski Black holes are regions of space that have so much gravity that nothing — not light, not particles, nada — can escape. Most galaxies have supermassive black holes at their centers, and these black holes are hundreds of thousands to billions of times the mass of our Sun. In active galactic nuclei (also called “AGN” for short, or just “active galaxies”) the central region is stuffed with gas and dust that’s constantly falling toward the black hole. As the gas and dust fall, they start to spin and form a disk. Because of the friction and other forces at work, the spinning disk starts to heat up.
This composite view of the active galaxy Markarian 573 combines X-ray data (blue) from NASA’s Chandra X-ray Observatory and radio observations (purple) from the Karl G. Jansky Very Large Array in New Mexico with a visible light image (gold) from the Hubble Space Telescope. Markarian 573 is an active galaxy that has two cones of emission streaming away from the supermassive black hole at its center. X-ray: NASA/CXC/SAO/A.Paggi et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA The disk’s heat gets emitted as light, but not just wavelengths of it that we can see with our eyes. We detect light from AGN across the entire electromagnetic spectrum, from the more familiar radio and optical waves through to the more exotic X-rays and gamma rays, which we need special telescopes to spot.
In the heart of an active galaxy, matter falling toward a supermassive black hole creates jets of particles traveling near the speed of light as shown in this artist’s concept. NASA/Goddard Space Flight Center Conceptual Image Lab About one in 10 AGN beam out jets of energetic particles, which are traveling almost as fast as light. Scientists are studying these jets to try to understand how black holes — which pull everything in with their huge amounts of gravity — somehow provide the energy needed to propel the particles in these jets.
This artist’s concept shows two views of the active galaxy TXS 0128+554, located around 500 million light-years away. Left: The galaxy’s central jets appear as they would if we viewed them both at the same angle. The black hole, embedded in a disk of dust and gas, launches a pair of particle jets traveling at nearly the speed of light. Scientists think gamma rays (magenta) detected by NASA’s Fermi Gamma-ray Space Telescope originate from the base of these jets. As the jets collide with material surrounding the galaxy, they form identical lobes seen at radio wavelengths (orange). The jets experienced two distinct bouts of activity, which created the gap between the lobes and the black hole. Right: The galaxy appears in its actual orientation, with its jets tipped out of our line of sight by about 50 degrees. NASA’s Goddard Space Flight Center Many of the ways we tell one type of AGN from another depend on how they’re oriented from our point of view. With radio galaxies, for example, we see the jets from the side as they’re beaming vast amounts of energy into space. Then there’s blazars, which are a type of AGN that have a jet that is pointed almost directly at Earth, which makes the AGN particularly bright.
Blazar 3C 279’s historic gamma-ray flare in 2015 can be seen in this image from the Large Area Telescope on NASA’s Fermi satellite. During the flare, the blazar outshone the Vela pulsar, usually the brightest object in the gamma-ray sky. NASA/DOE/Fermi LAT Collaboration Fermi has been searching the sky for gamma ray sources since 2008. More than half of the sources it has found have been blazars. Gamma rays are useful because they can tell us a lot about how particles accelerate and how they interact with their environment.
So why do we care about AGN? We know that some AGN formed early in the history of the universe. With their enormous power, they almost certainly affected how the universe changed over time. By discovering how AGN work, we can understand better how the universe came to be the way it is now.
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Last Updated Apr 30, 2025 Related Terms
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How can I see the northern lights?
To see the northern lights, you need to be in the right place at the right time.
Auroras are the result of charged particles and magnetism from the Sun called space weather dancing with the Earth’s magnetic field. And they happen far above the clouds. So you need clear skies, good space weather at your latitude and the higher, more polar you can be, the better. You need a lot of patience and some luck is always helpful.
A smartphone can also really help confirm whether you saw a little bit of kind of dim aurora, because cameras are more sensitive than our eyes.
The best months to see aurorae, statistically, are March and September. The best times to be looking are around midnight, but sometimes when the Sun is super active, it can happen any time from sunset to sunrise.
You can also increase your chances by learning more about space weather data and a great place to do that is at the NOAA Space Weather Prediction Center.
You can also check out my project, Aurorasaurus.org, where we have free alerts that are based on your location and we offer information about how to interpret the data. And you can also report and tell us if you were able to see aurora or not and that helps others.
One last tip is finding a safe, dark sky viewing location with a great view of the northern horizon that’s near you.
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By USH
In December 2024, reports began surfacing about strange events involving flashing streetlights house and building lights. These incidents, initially dismissed as isolated cases, have now been observed on a larger scale, spanning countries such as the U.S., Canada, and the UK.
Some observers theorize that drones or unidentified orbs might be responsible. These objects could emit electromagnetic interference, disrupting electrical systems and causing lights to flicker. However, no concrete evidence has linked these phenomena to drone activity.
Others suggest the lights could be a result of hackers targeting the power grid. Cybercriminals might be testing infrastructure vulnerabilities. While plausible, no definitive proof has emerged to support this explanation.
A more unconventional theory suggests that the flashing lights are a result of a phenomenon known as Streetlight Interference (SLI). Proponents argue that certain individuals, nicknamed "SLIders," possess psychic or psychokinetic abilities that unintentionally influence lighting systems. SLI remains scientifically unverified, with no successful replication in controlled settings.
Some experts believe it might be mechanical faults in the electrical systems or or fluctuations in the power supply. However, this theory seems unlikely due to the widespread and simultaneous nature of the phenomenon, which has been reported across multiple countries, suggesting it is not a localized issue.
Or is this phenomenon linked to extraterrestrial activity? Some argue that aliens might use electromagnetic propulsion systems, potentially interfering with electrical systems, akin to the effects portrayed in films like 'Close Encounters of the Third Kind'.
Could the cause of these flashing lights be a harbinger of an impending global or cosmic event, or might it stem from something entirely beyond our understanding?
The two videos below show, besides the on going mysterious drones/UFO/orb sightings, several locations where street lights are flashing.
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