NASA Astronomy Picture of the Day:

very time Venus passes the Earth, it shows the same face. This remarkable fact has been known for only about 50 years, ever since radio telescopes have been able to peer beneath Venus' thick clouds and track its slowly rotating surface. This inferior conjunction -- when Venus and Earth are the closest -- occurs today. The featured animation shows the positions of the Sun, Venus and Earth between 2010-2023 based on NASA-downloaded data, while a mock yellow 'arm' has been fixed to the ground on Venus to indicate rotation. The reason for this unusual 1.6-year resonance is the gravitational influence that Earth has on Venus, which surprisingly dominates the Sun's tidal effect. If Venus could be seen through the Sun's glare today, it would show just a very slight sliver of a crescent. Although previously visible in the evening sky, starting tomorrow, Venus will appear in the morning sky -- on the other side of the Sun as viewed from Earth. Experts Debate: How will humanity first discover extraterrestrial life?

NASA Astronomy Picture of the Day:

Humanity is under attack. The attack is not from large tentacle-flailing aliens, but from invaders so small they can barely be seen, and so strange they are not even clearly alive. All over planet Earth, the human home world, DNA-based humans are being invaded by the RNA-based SARS-CoV2. The virus, which creates a disease known as COVID-19, specializes in reprogramming human cells into zombies that manufacture and release copies of itself. Pictured here is a high magnification image of a human cell covered by attacking novel coronavirus SARS-CoV2 (orange). Epic battles where two species square off in a fight to the death are not unusual on Earth, with several just involving humans typically ongoing at any time. Even so, most humans are predicted to survive. After several years, humanity expects to win this war -- but only after millions of humans have died and trillions of coronaviruses have been destroyed. Wash your hands: Tips for humans on how to survive this SARS-CoV2 assault

NASA Astronomy Picture of the Day:

The center of the Lagoon Nebula is a whirlwind of spectacular star formation. Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long, have been formed by extreme stellar winds and intense energetic starlight. A tremendously bright nearby star, Herschel 36, lights the area. Vast walls of dust hide and redden other hot young stars. As energy from these stars pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds which may cause the funnels. This picture, spanning about 15 light years, features two colors detected by the orbiting Hubble Space Telescope. The Lagoon Nebula, also known as M8, lies about 5000 light years distant toward the constellation of the Archer Sagittarius.

NASA Astronomy Picture of the Day:

It was bright and green and stretched across the sky. This striking aurora display was captured in 2016 just outside of Östersund, Sweden. Six photographic fields were merged to create the featured panorama spanning almost 180 degrees. Particularly striking aspects of this aurora include its sweeping arc-like shape and its stark definition. Lake Storsjön is seen in the foreground, while several familiar constellations and the star Polaris are visible through the aurora, far in the background. Coincidently, the aurora appears to avoid the Moon visible on the lower left. The aurora appeared a day after a large hole opened in the Sun's corona allowing particularly energetic particles to flow out into the Solar System. The green color of the aurora is caused by oxygen atoms recombining with ambient electrons high in the Earth's atmosphere.

Photo by Göran Strand

NASA Astronomy Picture of the Day:

Follow a sunset on a clear day against a distant horizon and you might glimpse green just as the Sun disappears from view. The green flash is caused by refraction of light rays traveling to the eye over a long path through the atmosphere. Shorter wavelengths refract more strongly than longer redder wavelengths and the separation of colors lends a green hue to the last visible vestige of the solar disk. It's harder to see a green flash from the Moon, not to mention the diminutive disks of Venus and Mercury. But a telescope or telephoto lens and camera can help catch this tantalizing result of atmospheric refraction when the celestial bodies are near the horizon. From Sicily, the top panels were recorded on March 18, 2019 for the Sun and May 8, 2020 for the Moon. Also from the Mediterranean island, the bottom panels were shot during the twilight apparition of Venus and Mercury near the western horizon on May 24.

Photo by Marcella Giulia Pace

NASA Astronomy Picture of the Day:

That's not a bright star and crescent Moon caught between branches of a eucalyptus tree. It's Venus in a crescent phase and Mercury. Near the western horizon after sunset, the two inner planets closely shared this telescopic field of view on May 22, seen from a balcony in Civitavecchia, Italy. Venus, the very bright celestial beacon, is wandering lower into the evening twilight. It grows larger in apparent size and shows a thinner crescent as it heads toward its inferior conjunction, positioned between Earth and Sun on June 3. Mercury, in a fuller phase, is climbing in the western sky though, reaching its maximum angular distance from the Sun on June 4 Still, this remarkably close pairing with brilliant Venus made Mercury, usually lost in bright twilight skies, easier to spot from planet Earth. Gallery: Notable Venus & Mercury Conjunction 2020 Images submitted to APOD

Photo by Marco Meniero

NASA Astronomy Picture of the Day:

Still bathed in sunlight, the International Space Station arced through the evening sky over lake Wulfsahl-Gusborn in northern Germany, just after sunset on March 25. The familiar constellation of Orion can be seen left of the trail of the orbital station's bright passage. On the right, Venus is the brilliant evening star above the western horizon. With the camera fixed to a tripod, this scene was captured in a series of five exposures. How can you tell? The short time delay between the end of one exposure and the beginning of the next leaves small gaps in the ISS light trail. Look closely and you'll also see that the sky that appears to be above the horizon is actually a reflection though. The final image has been vertically inverted and the night skyscape recorded in the mirror-like waters of the small lake.

Photo by Helmut Schnieder

NASA Astronomy Picture of the Day:

What are those dots between Saturn's rings? Our Earth and Moon. Just over three years ago, because the Sun was temporarily blocked by the body of Saturn, the robotic Cassini spacecraft was able to look toward the inner Solar System. There, it spotted our Earth and Moon -- just pin-pricks of light lying about 1.4 billion kilometers distant. Toward the right of the featured image is Saturn's A ring, with the broad Encke Gap on the far right and the narrower Keeler Gap toward the center. On the far left is Saturn's continually changing F Ring. From this perspective, the light seen from Saturn's rings was scattered mostly forward , and so appeared backlit. After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 and was directed to enter Saturn's atmosphere, where it surely melted. Gallery: Notable Venus & Mercury Conjunction 2020 Images submitted to APOD

NASA Astronomy Picture of the Day:

What’s higher than the Himalayas? Although the Himalayan Mountains are the tallest on planet Earth, they don't measure up to the Milky Way. Visible above the snow-capped mountains in the featured image is the arcing central band of our home galaxy. The bright spot just above the central plane is the planet Jupiter, while the brightest orange spot on the upper right is the star Antares. The astrophotographer braved below-zero temperatures at nearly 4,000-meters altitude to take the photographs that compose this image. The featured picture is a composite of eight exposures taken with same camera and from the same location over three hours, just after sunset, in 2019 April, from near Bimtang Lake in Nepal. Over much of planet Earth, the planets Mercury (faint) and Venus (bright) will be visible this week after sunset. Experts Debate: How will humanity first discover extraterrestrial life?

Photo by TomasHavel

NASA Astronomy Picture of the Day:

Inside the head of this interstellar monster is a star that is slowly destroying it. The huge monster, actually an inanimate series of pillars of gas and dust, measures light years in length. The in-head star is not itself visible through the opaque interstellar dust but is bursting out partly by ejecting opposing beams of energetic particles called Herbig-Haro jets. Located about 7,500 light years away in the Carina Nebula and known informally as Mystic Mountain, the appearance of these pillars is dominated by dark dust even though they are composed mostly of clear hydrogen gas. The featured image was taken with the Hubble Space Telescope. All over these pillars, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dusty stellar nurseries in which they formed. Within a few million years, the head of this giant, as well as most of its body, will have been completely evaporated by internal and surrounding stars. APOD across world languages: Arabic, Catalan, Chinese (Beijing), Chinese (Taiwan), Croatian, Czech, Dutch, Farsi, French, French, German, Hebrew, Indonesian, Japanese, Korean, Montenegrin, Polish, Russian, Serbian, Slovenian, Spanish and Ukrainian