What are those bright lights in the sky ahead? When hiking a high mountain pass in northern Italy three weeks ago, a conjunction between our Moon and the distant planet Jupiter was visible as both rose together in the southwest after sunset. The picturesque mountains in the distance are Tre Cime di Lavaredo (Three Peaks of Lavaredo), a UNESCO World Heritage Site and three of the best known mountain peaks in Italy, the Dolomites, and the entire Alps. In the foreground on the left is Locatelli Hut, a refuge for tired hikers as it is located over an hour from nearest parking lot. The bright sky object on the upper left is Saturn. The entire scene was captured on a single 8-second exposure. Jupiter and Saturn will remain prominent in the western sky after sunset this month, while the Moon, in its monthly orbit around the Earth, will pass near Jupiter again in about four days.
Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as dusty as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The featured exposure took over 12 hours and covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye. The actual number of Pleiades stars visible, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer’s eyesight.
Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. Spanning about 40 light-years across the region, this infrared image from the Spitzer Space Telescope was constructed from data intended to monitor the brightness of the nebula’s young stars, many still surrounded by dusty, planet-forming disks. Orion’s young stars are only about 1 million years old, compared to the Sun’s age of 4.6 billion years. The region’s hottest stars are found in the Trapezium Cluster, the brightest cluster near picture center. Launched into orbit around the Sun on August 25, 2003 Spitzer’s liquid helium coolant ran out in May 2009. The infrared space telescope continues to operate though, its mission scheduled to end on January 30, 2020. Recorded in 2010, this false color view is from two channels that still remain sensitive to infrared light at Spitzer’s warmer operating temperatures.
This wide-field telescopic image looks toward the constellation Cepheus and an intriguing visual pairing of dusty reflection nebula NGC 7129 (right) and open star cluster NGC 7142. The two appear separated by only half a degree on the sky, but they actually lie at quite different distances. In the foreground, dusty nebula NGC 7129 is about 3,000 light-years distant, while open cluster NGC 7142 is likely over 6,000 light-years away. In fact, pervasive and clumpy foreground dust clouds in this region redden the light from NGC 7142, complicating astronomical explorations of the cluster. Still, NGC 7142 is thought to be an older open star cluster, while the bright stars embedded in NGC 7129 are perhaps a few million years young. The telltale reddish crescent shapes around NGC 7129 are associated with energetic jets streaming away from newborn stars.
While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it’s not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star’s outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star’s intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This impressive color composite highlights details within the well-studied central region and fainter, seldom imaged features in the nebula’s outer halo. It incorporates broad and narrowband images recorded using filters sensitive to emission from hydrogen and oxygen atoms.
Image data from the Hubble Space Telescope, the European Southern Observatory, and small telescopes on planet Earth are combined in this magnificent portrait of face-on spiral galaxy Messier 61 (M61). A mere 55 million light-years away in the Virgo Cluster of Galaxies, M61 is also known as NGC 4303. It’s considered to be an example of a barred spiral galaxy similar to our own Milky Way. Like other spiral galaxies, M61 also features sweeping spiral arms, cosmic dust lanes, pinkish star forming regions, and young blue star clusters. The bright galactic core is offset to the left in this 50 thousand light-year wide close-up.
Why is the sky near Antares and Rho Ophiuchi so dusty yet colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae. Backlit dust clouds block starlight and so appear dark. Antares, a red supergiant and one of the brighter stars in the night sky, lights up the yellow-red clouds on the lower left of the featured image. Rho Ophiuchi lies at the center of the blue nebula near the top. The distant globular cluster M4 is visible to the right of Antares. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum.