The handle of the Dipper offers a convenient guide two stately face-on spiral galaxies that are visible, at least to some degree, in a small telescope. In dark skies, these two nearby galaxies display clear hints of a striking and ubiquitous pinwheel shape that reveals itself in the clouds of a hurricane or the seed arrangement in a sunflower, a reminder that many of nature’s patterns appear at a wide range of scales [Read more…] about Two Fine Spiral Galaxies Near the Dipper’s HandleShare This:
In our previous stop on our tour of celestial objects of cosmological importance, we looked at a handful of galaxies measured by the early 20th-century astronomer Vesto Slipher. The former Indiana farm boy wrestled with a modestly endowed telescope and a 450-pound spectrometer to make an astonishing discovery. He found the ‘spiral nebulae’ like Andromeda (M31) and the Sombrero (M104) were moving away from us at astonishing speeds, up to 1000 km/s and far faster than any nearby stars. The speeds of these spiral assemblies strongly suggested they lay outside our own group of stars, and were perhaps separate galaxies in their own right far outside our own.
But in science, a strong suggestion is not proof.
In the first years of the 20th century, astronomers had no way of knowing for sure the distance to these spiral assemblies. Indeed, a hundred years ago, they only could estimate the distances to a handful of nearby stars. The true scale of even our own galaxy was a complete mystery. No one knew whether the Milky Way was all there was to the universe, and whether it was a hundred light years across, or a thousand, or a trillion. Never mind the distances to the mysterious ‘spiral nebulae’, which may simply have been nearby star systems in the process of formation.
The key to the distance to the spiral nebulae, which we now know to be separate galaxies, and to the universe itself, lay unexpectedly in a class of unassuming stars, many of which you can see from your backyard with a pair of binoculars or without any optics at all [Read more…] about The Distances to the GalaxiesShare This:
A few weeks ago you had a look at the justly famous Sombrero Galaxy in the constellation Virgo. In a small telescope, the galaxy looks like a silver shard, a faint sliver of light with a star-like core obscured from end to end by a sharply defined lane of dust. It’s one of the prettiest galaxies in the night sky, and it was also a favorite of the Indiana-born astronomer Vesto Slipher, who paused to admire it from time to time as he analyzed its light to make one of the great discoveries of the 20th century. Let’s examine a few more photogenic galaxies on Slipher’s observing list from more than a century ago, and understand just what it was that he unexpectedly discovered [Read more…] about Spring Spiral Galaxies and the Expanding UniverseShare This:
One of the closest congregations of galaxies to our own, the Sculptor Group consists of a series of relatively bright and shapely galaxies clustered in the barren sky near the south galactic pole. The group is anchored by the majestic NGC 253, the Silver Coin Galaxy, one of the most beautiful galaxies for a small telescope. But a little farther south lie two more gems, NGC 55, also called the ‘String of Pearls’, and NGC 300, one of a handful of galaxies known as the ‘Southern Pinwheel’. For northern observers, this pair is low in the thick air over the southern horizon in the late months of the year. Southern-hemisphere observers, however, see these galaxies nearly overhead where it’s much easier to see their distinctive shape and features in a small telescope [Read more…] about Two Fine Galaxies in the Sculptor GroupShare This:
The galaxy IC342 ranks as one of the under-appreciated gems of the northern night sky. As you can see in the image above, this elegant nearby spiral galaxy in the far-northern constellation Camelopardalis (the Giraffe) is a photogenic target for experienced imagers. But it’s rather challenging to see visually in all but the darkest skies. It is, however, worth the effort to see this swirling assembly because it lies in an unusually beautiful field of foreground stars [Read more…] about IC342: An Obscured Spiral Galaxy, Hiding in Plain SightShare This: