Using basic trigonometry, astronomers can directly calculate the distances to nearby stars by measuring the tiny shift in position that occurs as Earth sweeps from one side of its orbit to the other. But what about globular clusters, the huge star swarms that orbit the core of the Milky Way? They are typically too far away to measure the tiny angles needed to make the calculations. Instead, astronomers were long forced to estimate distances based on stellar evolution theory and how the brightness and colours of stars in a globular cluster differed from similar nearby suns. But last year, the Hubble Space Telescope managed to directly measure the distance to NGC 6397, one of the nearest globulars to Earth, to an accuracy of just 3 percent. The answer? 7,800 light years. The cluster apparently formed some 13.4 billion years ago, shortly after the big bang.
A composite image from the Hubble Space Telescope shows a dramatic range of color in galaxy NGC 3344, a weakly barred spiral half the size of the Milky Way some 20 million light years away in the constellation Leo Minor. Hot young stars, seen in blue, populate the spiral arms along with glowing red clouds of gas and dust that provide the raw materials for new suns.
Elliptical galaxy NGC 3610 is the most prominent object in this amazing Hubble image — and a very interesting one at that! Discovered in 1793 by William Herschel, it was later found that this galaxy contains a disc. This is very unusual, as discs are one of the main distinguishing features of a spiral galaxy. And the disc in NGC 3610 is remarkably bright.