FROSTY EVENINGS of late autumn find the brilliant star Capella climbing the eastern sky. This is the brightest star of Auriga, one of the landmark constellations of late fall and winter. Auriga straddles the winter Milky Way and fairly bursts with telescopic riches -if you make the effort to hunt them out.

Many telescope users don't. They settle for Auriga's three big Messier star clusters, M36, M37, and M38, which show as hazy glows in binoculars and fine splashes of stardust in a small telescope. But if you're willing to step off the well-worn path, there's a lot more waiting to be found. This web page gives a detailed telescopic walk through this interesting region.



1. Capella
At magnitude 0, Capella is the sixth brightest star other than the Sun. Its pale yellow color is plainly visible to the naked eye and beautiful in any optical instrument.

Capella is the brightest type G star visible from mid-northern latitudes. It is a trace yellower than the Sun, having a color index of 0.8 compared to the Sun's 0.6. Located 45 light-years away, Capella is an unresolvable binary consisting of two giant stars about 90 and 70 times as bright as the Sun. They orbit each other every 3½ months as far apart as the Sun is from Venus.

2. Epsilon Aurigae
Our first starhop takes us a little more than 3° southwest to this 3rd-magnitude stepping-stone. Try locating it by looking only in your finderscope, ignoring the naked-eye view, to check that you can move a specified direction and distance with the finder.

Epsilon Aurigae is a type F0 supergiant several thousand light-years away. Every 27 years it undergoes a partial eclipse by a gigantic, invisible dark body orbiting it. The most recent eclipse lasted from 1982 to 1984; the next isn't due until 2009.

3. Eta and Zeta Aurigae
This pair of stars is a nice study in color contrasts. Find them a little less than 3° south of Epsilon. Eta, the brighter of the two, is spectral type B3 and slightly bluish. In fact it is about as blue as a star can get, with a color index of - 0.2. Zeta, on the other hand, is an orange giant of spectral type K4 and color index 1.2.

You'll find the color contrast to be plainest in binoculars or a finder. In a 6-inch reflector at 50 power Eta and Zeta are wonderful jewels, but their brilliance seems to wash out some of their color. Both stars are several hundred light-years away.

As a quick check of field diameters, Zeta is 2.7° from Epsilon, 0.8° from Eta, and 0.4° from the 6th-magnitude star just to its north-northeast.

4. NGC 1857
NGC 1857 is a hazy little open star cluster discovered by William Herschel two centuries ago. The cluster contains about 40 faint stars in an area just 6' across. In a 6-inch reflector it appears as a weak but definite glow hiding at the edge of a much larger, very loose group of brighter stars. It gives the impression of being far behind them, like something glowing deep underwater below bright specks floating on the surface. A 7th-magnitude orange star is almost on top of it.

5. Sigma Aurigae
Sigma displays a strong fire-orange color, as might be expected from its spectral type of K4 III and color index of 1.4. The primary star shines at magnitude 5.0; a companion glimmers at 11th or 12th magnitude and lies about 9" to Sigma's south-southeast.

If you have a large telescope or a very dark sky, you might take a slight detour to try for the dim and difficult planetary nebula IC 2120 just 1.3° west of Sigma. It is supposed to have a smooth disk 47" in diameter.

6. M38
Shift almost 2' southeast from Sigma Aurigae, and you'll sweep into this big, bright showpiece of an open cluster. M38 is a rich swarm of some 100 stars of about magnitude 10 and fainter. The cluster is 20' in diameter and looks rather squarish in a 6-inch at 50x, with clumps of stars in the corners. Gazing at it you seem to get occasional glimpses of an even larger, richer background of countless extremely faint stars. Take the time to see if this remote wealth flickers into view.

7. NGC 1907
Just ½° south of M38 is a smaller, fainter, but more compact companion cluster. NGC 1907 contains about 30 stars in an area 7' across. It lies at about the same distance as M38, 4,500 light-years, and may be physically related to it. In a 6-inch at 50x it will appear as an eerie, partially resolved glow.

8. Struve 698
Next star-hop your way 0'.7 southwest to this 7th-magnitude double star. It's a real eye-catcher, golden and smoky gray-blue, with the wide separation of 31". The stars are magnitudes 6.6 and 8.7. Both are catalogued as spectral class K, so the bluish hue of the secondary must be a contrast illusion caused by the bright orange primary. Can you convince yourself that the secondary is really orange?

9. Stock 8 and IC 417
Stock 8 is a small gathering of about 40 faint stars 5' in diameter. Good conditions may help when using small apertures.
Phi Aurigae is the brightest star for some distance around. It is the most prominent of a nameless bunch of field stars about 1/3° in diameter. Another bunch of similar size lies 1/3° to its north.

10. NGC 1893 and IC 410
Here are another, larger cluster and nebula. NGC 1893 appears as a bold, irregular spray of stars in a 6-inch, very elongated north-south. The cluster is estimated to be a mere I million years old, compared to tens or hundreds of millions for most open clusters. It contains about 60 stars.

A half degree north of NGC 1893 is a tiny triple star in the form of a narrow isosceles triangle. This is Struve 687. The triangle is about 50" long and 18" wide, with the western star slightly brighter than the other two.

11. AE Aurigae and the Flaming Star nebula
Hop less than a degree west to the prominent asterism of 16 through 19 Aurigae. This group is immediately recognizable in binoculars or a finder. Continue northwest from there to find 6th-magnitude AE Aurigae.

This type O star is slightly variable in an irregular way. It illuminates the diffuse nebula IC 405, also known as the Flaming Star nebula. In moderately large amateur telescopes the "flames" appear as a big, vague glow to the star's east and north about 20' across. A 6-inch may show hints of the nebulosity. Using high power, look in particular for the narrow wisp ¼° north of AE.

Unlike most O stars in nebulae, AE Aurigae was not born there but is just passing through - and fast. It is hurtling at about 80 miles per second directly away from the great star-forming region around Orion's Sword. Presumably it was expelled from there about 2.7 million years ago. AE Aurigae may have begun life in a tight, fast orbit around another star that blew apart as a supernova, leaving AE to fly away at its orbital velocity. We catch it lighting up the nebula for only a brief time, perhaps 20,000 years. Once it passes, the nebula will return to darkness.

12. KW Aurigae and Dolidze 16
A degree southwest of the Minnow's tail is the 5th-magnitude triple star 14 Aurigae. Two components are immediately obvious in a 6-inch at 50x; the third requires some close looking.

Component A, magnitude 5. 1, varies by an unnoticeable 0.1 magnitude every two hours, earning it the variable star designation KW Aurigae. Component C is the next brightest at magnitude 7.4; it lies 15" southwest of A. Component B is the faintest at magnitude 11, a little spark about 10" north of A.

In addition, a 10th-magnitude star D is 180" northwest. At that distance it is not likely to be a true member of the system.

Just west is a very sparse, irregular gathering of 10 stars known as Dolidze 16. It is listed as about 12' across. In a 6-inch at 50x the cluster is evident once you look for it but is too poor and thin to call much attention to itself.

13. NGC 1931
NGC 1931 is a tiny but rather bright emission and reflection nebula surrounding a 9th-magnitude star. The star is quite obviously fuzzy in a 6-inch. The star itself is a triple and bears the designation ADS4112. Its components A, B, and C are magnitudes 9, 10, and 11, respectively. B is 7" west-southwest of A, and C is 10" to A's northwest.

14. M36
M36 compares well with nearby M38, to which you might want to backtrack for another look. M36 has fewer stars than M38 and is hardly more than half the size, but its stars are brighter. Several of the brightest, including an equal-component double, are arranged in roughly parallel rows.

M36, M38, NGC 1907, and possibly NGC 1931 are all part of the great Auriga OB1 association of young stars 4,000 or 4,500 light-years away.

15. M37
M37 combines the size and richness of M38 with the star brightness of M36. It is nearly 4° east-southeast of M36. M37 appears as a rich, somewhat triangular hive of stellar activity with a number of colored stars. The cluster comprises some 150 stars in an area 24' across. Its distance, like that of the previous clusters, is about 4,500 light-years.

These objects and their extraordinary qualities can be properly appreciated only when they are made part of your observing program, not part of an unchallenging routine. The harder you work at seeing the most your telescope will show, the more rewarding your observing will be.