On February 18, as civil twilight began in northern New Mexico skies, the International Space Station, a waning crescent Moon, and planet Mars for a moment shared this well-planned single field of view. From the photographer’s location the sky had just begun to grow light, but the space station orbiting 400 kilometers above the Earth was already bathed in the morning sunlight. At 6:25am local time it took less than a second to cross in front of the lunar disk moving right to left in the composited successive frames. At the time, Mars itself had already emerged from behind the Moon following its much anticipated lunar occultation. The yellowish glow of the Red Planet is still in the frame at the upper right, beyond the Moon’s dark edge.
Why does this galaxy spin so fast? To start, even identifying which type of galaxy UGC 12591 is difficult — featured on the lower left, it has dark dust lanes like a spiral galaxy but a large diffuse bulge of stars like a lenticular. Surprisingly observations show that UGC 12591 spins at about 480 km/sec, almost twice as fast as our Milky Way, and the fastest rotation rate yet measured. The mass needed to hold together a galaxy spinning this fast is several times the mass of our Milky Way Galaxy. Progenitor scenarios for UGC 12591 include slow growth by accreting ambient matter, or rapid growth through a recent galaxy collision or collisions — future observations may tell. The light we see today from UGC 12591 left about 400 million years ago, when trees were first developing on Earth.
Do you recognize this constellation? Setting past the Central Bohemian Highlands in the Czech Republic is Orion, one of the most identifiable star groupings on the sky and an icon familiar to humanity for over 30,000 years. Orion has looked pretty much the same during this time and should continue to look the same for many thousands of years into the future. Prominent Orion is high in the sky at sunset this time of year, a recurring sign of (modern) winter in Earth’s northern hemisphere and summer in the south. The featured picture is a composite of over thirty images taken from the same location and during the same night last month. Below and slightly to the left of Orion’s three-star belt is the Orion Nebula, while four of the bright stars surrounding the belt are, clockwise, Sirius (far left, blue), Betelgeuse (top, orange, unusually faint), Aldebaran (far right), and Rigel (below). As future weeks progress, Orion will set increasingly earlier. Infinite Random Loop: Create an APOD Station in your classroom or Science Center.
Besides fading, is Betelgeuse changing its appearance? Yes. The famous red supergiant star in the familiar constellation of Orion is so large that telescopes on Earth can actually resolve its surface — although just barely. The two featured images taken with the European Southern Observatory’s Very Large Telescope show how the star’s surface appeared during the beginning and end of last year. The earlier image shows Betelgeuse having a much more uniform brightness than the later one, while the lower half of Betelgeuse became significantly dimmer than the top. Now during the first five months of 2019 amateur observations show Betelgeuse actually got slightly brighter, while in the last five months the star dimmed dramatically. Such variability is likely just normal behavior for this famously variable supergiant, but the recent dimming has rekindled discussion on how long it may be before Betelgeuse does go supernova. Since Betelgeuse is about 700 light years away, its eventual supernova — probably thousands of years in the future — will likely be an amazing night-sky spectacle, but will not endanger life on Earth.
To some, this huge nebula resembles a person’s head surrounded by a parka hood. In 1787, astronomer William Herschel discovered this unusual planetary nebula: NGC 2392. More recently, the Hubble Space Telescope imaged the nebula in visible light, while the nebula was also imaged in X-rays by the Chandra X-ray Observatory. The featured combined visible-X ray image, shows X-rays emitted by central hot gas in pink. The nebula displays gas clouds so complex they are not fully understood. NGC 2392 is a double-shelled planetary nebula, with the more distant gas having composed the outer layers of a Sun-like star only 10,000 years ago. The outer shell contains unusual light-year long orange filaments. The inner filaments visible are being ejected by strong wind of particles from the central star. The NGC 2392 Nebula spans about 1/3 of a light year and lies in our Milky Way Galaxy, about 3,000 light years distant, toward the constellation of the Twins (Gemini).
A jewel of the southern sky, the Great Carina Nebula, also known as NGC 3372, spans over 300 light-years, one of our galaxy’s largest star forming regions. Like the smaller, more northerly Great Orion Nebula, the Carina Nebula is easily visible to the unaided eye, though at a distance of 7,500 light-years it is some 5 times farther away. This gorgeous telescopic close-up reveals remarkable details of the region’s central glowing filaments of interstellar gas and obscuring cosmic dust clouds in a field of view nearly 20 light-years across. The Carina Nebula is home to young, extremely massive stars, including the still enigmatic and violently variable Eta Carinae, a star system with well over 100 times the mass of the Sun. In the processed composite of space and ground-based image data a dusty, two-lobed Homunculus Nebula appears to surround Eta Carinae itself just below and left of center. While Eta Carinae is likely on the verge of a supernova explosion, X-ray images indicate that the Great Carina Nebula has been a veritable supernova factory.
On Valentine’s Day in 1990, cruising four billion miles from the Sun, the Voyager 1 spacecraft looked back one last time to make the first ever Solar System family portrait. The portrait consists of the Sun and six planets in a 60 frame mosaic made from a vantage point 32 degrees above the ecliptic plane. Planet Earth was captured within a single pixel in this single frame. It’s the pale blue dot within the sunbeam just right of center in this reprocessed version of the now famous view from Voyager. Astronomer Carl Sagan originated the idea of using Voyager’s camera to look back toward home from a distant perspective. Thirty years later, on this Valentine’s day, look again at the pale blue dot.