Vista de uma praia em Alexandria (Egipto).
MOHAMED HOSSAM EFE
2017-09-21
Imagens do Mundo - Hong Kong, China
Um ferry navega até à Ilha de Hong Kong, China.
ANTHONY WALLACE AFP
Astronomy picture of the day - 2017 September 21 - A September Morning Sky
Image Credit & Copyright: Tamas Ladanyi (TWAN)
Explanation: The Moon, three planets, and a bright star gathered near the ecliptic plane in the September 18 morning sky over Veszprem Castle, Hungary. In this twilight skyscape, Mercury and Mars still shine close to the eastern horizon, soon to disappear in the glare of the Sun. Regulus, alpha star of the constellation Leo, is the bright point next to a waning crescent Moon, with brilliant Venus near the top of the frame. The beautiful morning conjunction of Moon, planets, and bright star could generally be followed by early morning risers all around planet Earth. But remarkably, the Moon also occulted, or passed directly in front of, Regulus and each of the three planets within 24 hours, all on September 18 UT. Visible from different locations, timing and watching the lunar occultations was much more difficult though, and mostly required viewing in daytime skies.
2017-09-19
Astronomy picture of the day - 2017 September 19 - Veil Nebula: Wisps of an Exploded Star
Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Explanation: Wisps like this are all that remain visible of a Milky Way star. About 7,000 years ago that star exploded in a supernova leaving the Veil Nebula. At the time, the expanding cloud was likely as bright as a crescent Moon, remaining visible for weeks to people living at the dawn of recorded history. Today, the resulting supernova remnant, also known as the Cygnus Loop, has faded and is now visible only through a small telescope directed toward theconstellation of the Swan (Cygnus). The remaining Veil Nebula is physically huge, however, and even though it lies about 1,400 light-years distant, it covers over five times the size of the full Moon. The featured picture is a Hubble Space Telescope mosaic of six images together covering a span of only about two light years, a small part of the expansive supernova remnant. In images of the complete Veil Nebula, even studious readers might not be able to identify the featured filaments.
2017-09-18
Astronomy picture of the day - 2017 September 18 - Orion above Easter Island
Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory, TWAN)
Explanation: Why were the statues on Easter Island built? No one is sure. What is sure is that over 800 large stone statues exist there. The Easter Island statues, stand, on the average, over twice as tall as a person and have over 200 times as much mass. Few specifics are known about the history or meaning of the unusual rock sculptures, but many believe that they were created about 700 years ago in the images of local leaders of a lost civilization. Featured here, one of the ancient Moai sculptures was imaged in 2016 before the constellation of Orion, including the famous line of three belt stars and brilliant stars Betelgeuse (far left in red) and Rigel (upper center). The stone giant appears, however, to be inspecting the brightest star in the night sky (far right): Sirius.
2017-09-17
Astronomy picture of the day - 2017 September 17 - Bright Spiral Galaxy M81
Image Credit: Subaru Telescope (NAOJ), Hubble Space Telescope;
Processing & Copyright: Roberto Colombari & Robert Gendler
Explanation: One of the brightest galaxies in planet Earth's sky is similar in size to our Milky Way Galaxy: big, beautiful M81. This grand spiral galaxy can be found toward the northern constellation of the Great Bear (Ursa Major). This superbly detailed view reveals M81's bright yellow nucleus, blue spiral arms, and sweeping cosmic dust lanes with a scale comparable to the Milky Way. Hinting at a disorderly past, a remarkable dust lane actually runs straight through the disk, to the left of the galactic center, contrary to M81's other prominent spiral features. The errant dust lane may be the lingering result of a close encounter between M81 and its smaller companion galaxy, M82. Scrutiny ofvariable stars in M81 has yielded one of the best determined distances for an external galaxy -- 11.8 million light-years.
2017-09-16
Astronomy picture of the day - 2017 September 16 - Cassini's Final Image
Image Credit: NASA, JPL-Caltech, Space Science Institute
Explanation: As planned, the Cassini spacecraft impacted the upper atmosphere of Saturn on September 15, after a 13 year long exploration of the Saturnian System. With spacecraft thrusters firing until the end, its atmospheric entry followed an unprecedented series of 22 Grand Finale dives between Saturn and rings. Cassini's final signal took 83 minutes to reach planet Earth and the Deep Space Network antenna complex in Canberra Australia where loss of contact with the spacecraft was recorded at 11:55 UT. For the spacecraft, Saturn was bright and the Sun was overhead as it plowed into the gas giant planet's swirling cloud tops at about 70,000 miles (113,000 kilometers) per hour. But Cassini's final image shows the impact site hours earlier and still on the planet's night side, the cloud tops illuminated by ringlight, sunlight reflected from Saturn's rings.
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