Deep Sky Observing

Articles about how to understand, find, and see celestial objects including stars, galaxies, nebulae, and star clusters with binoculars, telescopes, and the naked eye.

The Sound of the Jellyfish Nebula

March 26, 2024 by Brian Ventrudo Filed Under: Deep Sky, Science

A composite false-color image of the Jellyfish Nebula (IC443). Red indicates visible light, green shows regions of radio emission, and blue shows X-ray emission. Image credit: NASA/Chandra X-Ray Observatory.

Not far from the bright star Propus in the feet of the constellation Gemini lies the supernova remnant IC443, also known as Sharpless 248, but which is more evocatively known as the Jellyfish Nebula. While it’s a difficult object to see visually, this cosmic echo of a long-dead star presents a superb target for imagers because of its turbulent and complex structure. The nebula, which is about 5,000 light years away, is adjacent to a rich region of new star formation called Sharpless 249 in the Orion Spur of the Milky Way which makes the whole region even more photogenic.

The Jellyfish Nebula got its start when a massive star ran out of fuel, quickly collapsed, and detonated as a supernova about 30,000 years ago in a gas-strewn patch of the Milky Way. The shock wave from the explosion collided with clouds of interstellar gas and set them aglow to produced the intricate lacework of nebulosity that makes up the nebula. Most of the glowing gas is hydrogen, but there are also traces of light from ionized oxygen, sulfur, and other elements.
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The Flaming Star Nebula

February 27, 2024 by Brian Ventrudo Filed Under: Deep Sky

The Flaming Star Nebula (IC 405 or Caldwell 31) makes the must-see lists of many visual stargazers and astronomical imagers this time of year. This showpiece nebula in the northern constellation Auriga gains its energy from the star AE Aurigae, a 6^th-magnitude massive blue-white star about 1,500 light years away. This brilliant star, which outshines our Sun by some 30,000 times, blasts out ultraviolet light that ionizes the cloud of hydrogen gas around the star. As the hydrogen atoms reassemble, they emit light at visible wavelengths that make these nebulae so beautiful. IC 405 features a remarkably complex structure with knots of glowing gas that do indeed resemble starry flames frozen into the dark background sky.
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Star Factories in Cepheus

January 28, 2024 by Brian Ventrudo Filed Under: Deep Sky

A deep-field H-alpha image of a small region in Cepheus, about 7 degrees on each edge, showing the nebula IC 1396 surrounding the star cluster Trumpler 37 at lower right and the ‘Flying Bat’ nebula, Sh2-129, at the upper left of the image.

This month we turn our gaze to a field of view about 7^o square in the crooked-house of the constellation Cepheus. The field is a little smaller than your closed fist held at arm’s length. In the image above, captured in H-alpha with a small monochrome astronomy camera and a 90 mm lens, you see in this field a pair of spectacular emission nebulae, an embedded star cluster, half-dozen dark nebulae hiding regions of new star formation, and a blazing late-stage star on the verge of blowing itself to bits. [Read more…] about Star Factories in Cepheus

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A Deep-Sky Vista and the Dark Nebula Le Gentil 3

November 27, 2023 by Brian Ventrudo Filed Under: Deep Sky

The North America Nebula (lower left) and IC1396 (upper right). The dark form of Le Gentil 3 lies just right and below center in this image.

Every picture tells a story, and this wide-field image of the northern Milky Way in Cygnus and Cepheus, which spans nearly 16º on each edge, surely has a lot going on.

To the upper right of this image, you see the blossom-like emission nebula IC1396 in Cepheus with the aging red-orange star μ Cephei, the ‘Garnet Star’, on its limb. Plenty of stars are forming within this stellar nursery.

At the upper left, you see the tiny blossom of the Cocoon Nebula (IC 5146), another stellar nursery at the end of a two-degree-long dark nebula Barnard 168, both set in a rich field of background stars.

Moving down the left side of the image you see more nebulosity culminating in the unmistakable North America Nebula (NGC 7000) and the neighbouring Pelican Nebula (IC 5070) below, both of which encompass more active regions of star formation. Various patches of dark dust and distant star clouds, especially the square formation above NGC 7000 also lie within this wide view, as does the bright star Deneb at the tail of Cygnus, the Swan.

But the showpiece of this image is notable for its lack of light. Just right and below centre you see the vast and irregular void of a cloud of gas and interstellar dust known as Le Gentil 3 that comprises an immense conglomeration of star-making material in the early stages of giving birth to dozens of new star clusters.

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Five Fall Double Stars for a Small Telescope

October 29, 2023 by Brian Ventrudo Filed Under: Deep Sky

Albireo (Beta Cygni). Image credit: Jared Smith via Flickr under Creative Commons license.

Galaxies abound in the deep sky of northern autumn and imagers and visual observers with big telescopes and dark sky have plenty of choice targets. But for us urban visual observers with smaller scopes, galaxies, despite shining with the combined light of several hundred million stars, usually look a little underwhelming. So what’s left to see? Double stars, of course! Often overlooked for flashier sights, double (and multiple) stars offer a great challenge, contrasting colours, and understated but still gasp-worthy beauty that doesn’t take long to appreciate. Here are five superb double stars for northern autumn observers that will make you a fan of these under appreciated objects, listed approximately in order of easiest to hardest to observe [Read more…] about Five Fall Double Stars for a Small Telescope

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