We have reached that particular time of year when the sky is in transition and we are about to turn the page, so to speak, from the glorious stars and constellations of winter to the somewhat dimmer stars of spring.
And the farewell to those bright winter lights will be pretty quick, in part because of the increasing duration of daylight. Indeed, from early February to early May, the duration of daylight hours increases by an average of 2.7 minutes per day; nearly 20 minutes a week.
During this time, the stars rise and set about four minutes earlier each day. Thus, the combination of these two factors appears to speed up visibility times for winter star patterns.
Related: Night sky, March 2023: what you can see tonight [maps]
Take for example the constellation of Orion. On March 15, two hours after sunset, we find the mighty fighter still in plain sight, about halfway up in the sky and leaning toward the west-southwest horizon. But a month later, on April 15, again two hours after sunset, Orion is much lower and leaning even further towards the horizon. In fact, his left leg literally stands on the west-southwest horizon. And on May 15, two hours after sunset, Orion left. It won’t be until early August that we get our first glimpse of it in the morning sky, rising about an hour before the low sunrise in the east-southeast.
But going back to now, evening sky watchers still have the winter stars in good position and occupy the sky from the west and southwest, while the oncoming spring stars unfold in the sky from the southeast and the east. So let’s explore the personalities of some of the stars that present themselves to us two hours after sunset. We will limit ourselves to stars of the first magnitude or brighter – the popular term for those of magnitude -1, 0 and +1. In other words, any star brighter than magnitude +1.5 is eligible. (A negative magnitude indicates a particularly bright object; the higher the number, the darker it appears.)
Be aware of the planets!
As a warning, let’s also point out that there are a few bright objects in our current evening sky that can be mistaken for stars. They are actually luminous planets. Two hours after sunset, dazzling Venus hangs above the western horizon, while yellow-orange Mars rises much higher – about two-thirds of the way west-southwest of the horizon.
During the second half of March, the red planet passes from the horns of the Taurus bull to the left foot of Castor, one of the twin brothers of Gemini. Venus eclipses everything in the night sky except the moon. Mars is about a hundred times dimmer but currently still ranks as a first magnitude object, although it fades as it continues to move away from Earth.
Two hours after sunset on evenings in late March, the brightest star in our night sky, bluish Sirius, continues to steal the show. It is found to the west of the meridian and low to the south. It looks so bright, at magnitude -1.46, mainly because it’s so close to us, just 8.6 light-years away. Inherently 25 times brighter than our sun, the Dog’s Star is famous for its companion white dwarf (the first degenerate star ever discovered), whose presence was inferred in the 1830s by Friedrich Wilhelm Bessel from the ripple that he found in the movement of Sirius through space. This close and faint companion star, the “Pup”, was first sighted in 1862 by Alvan G. Clark, while testing the excellent 18.5-inch refractor lens now at the Dearborn Observatory in the United Kingdom. ‘Northwestern University.
Beneath Sirius is the “almost” 1st magnitude star Adhara. Although its magnitude is listed as 1.50 in the Royal Astronomical Society of Canada’s 2023 Observer’s Handbook, because astronomers rank these star brightness rankings by a process known as ” binning”, Adhara is barely too weak to be ranked first. magnitude star. The threshold for the official first-magnitude classification is +1.49, so Adhara is recognized as another second-magnitude star; it is the 22nd brightest in the sky, a blue giant and some 430 light years away.
For those living south of +35° latitude, the second-brightest star in the sky is visible well below Sirius and just above the south-southwest horizon. canopy (magnitude -0.74) is a yellow-white giant, about 310 light-years away and emits as much light as 10,000 suns.
Higher and northeast of Sirius is Procyon, at magnitude 0.34, sometimes called the Little Dog Star. The yellow-white Procyon looks so bright because it’s only 11.5 light-years away from us; its intrinsic brightness is only about seven times that of the sun. Like Sirius, Procyon also has a white dwarf companion, whose presence has also been betrayed by its gravitational pull on the main star.
Reddish Betelgeuse in Orion is directly west of Procyon. It is very different from the other three stars, being an enormous red supergiant, so enormous that if it were centered in our solar system, its surface would lie beyond the asteroid belt and it would swallow up the orbits of Mercury, Venus, Earth and Mars. It is by no means a stellar neighbor, being some 548 light-years away from us. And like virtually all other red supergiants, Betelgeuse is a variable star. Its magnitude oscillates irregularly between 0.0 and 1.6.
Even further away is blue-white Rigel, diagonally across Orion from Betelgeuse. This star beacon is one of the brightest in our galaxy, emitting far more light (more than 62,000 times) than our sun. Despite its distance of some 863 light years, it manages to shine at a magnitude of 0.13. Incidentally, the three stars that make up Orion’s famous belt are also Rigel-type dazzling ones, but are almost twice as far from it.
Northwest of Orion is Aldebaran, a bright giant orange star of magnitude 0.85, but with slight variations. It’s a modest 65 light years from us. From our perspective on Earth, this is apparently part of the V-shape Hyades star cluster. Aldebaran, however, is just an innocent bystander; a foreground object, about half the distance from the cluster.
Located about halfway up the western sky, we can see Chapel, a bright yellowish twinkle, 43 light-years away and bright at magnitude 0.08. If you live north of latitude +44°, this star is circumpolar and visible all year round. It is the most solar of the bright winter stars, an extremely close double star whose components are slightly cooler but noticeably brighter and more massive than our own star.
Finally, well above the south-southwest horizon is Pollux in Gemini. This yellow star of magnitude 1.14 is physically similar to Aldebaran, but at a distance of 34 light years, it is only half as far away. And in 2006, an extrasolar planet, later named Thestias, was confirmed orbiting it.
The stars of spring and one last thought
Rise to a point more than halfway up the southeast sky Regulus in Leo the Lion, who leads the spring constellations on the stellar stage while the winter ones withdraw into the western wings. Blue-white Regulus, of magnitude 1.40, is only 79 light-years away and 316 times brighter than the Sun.
Finally, we have Arcturus in Boötes le Bouvier, which rises from the lower sky east-northeast. This orange star of magnitude -0.05 is now known to be 37 light-years away from us, but in 1933 astronomers thought it was 40. That year, at the “Century of Progress” exhibit in Chicago, starlight from Arcturus, focused on a photocell attached to the 40-inch (101 cm) Yerkes refractor and turned on the lights of the exhibit. Astronomers thought they were using radiation that began towards us in 1893 – 40 years before, when the giant Yerkes’ tube and mount were first shown to the public at the Columbian Exposition in the same city. But starlight actually started toward Earth in 1896.
Today, we know a lot more about stars than early astronomers dared to believe. Two hundred and fifty years ago, no one had succeeded in measuring the distance to a star. And the 19th century French philosopher and mathematician Auguste Comte (1798-1857) identified the chemical composition of stars as something man could never know. But thanks to today’s technology, we can combine our appreciation for the beauty of stars with an understanding of what they really are.
If you want to see the stars up close during this seasonal transition, our guides to the best telescopes and the best binoculars are a great place to start. Binoculars are a great tool for viewing entire constellations and asterisms!
And if you’re looking to take pictures of the night sky in any season, check out our guides on how to photograph the moon recommending the best cameras for astrophotography and the best lenses for astrophotography.
Joe Rao is an instructor and guest speaker at New York’s Hayden Planetarium (opens in a new tab). He writes on astronomy for natural history journal (opens in a new tab)THE Farmers Almanac (opens in a new tab) and other publications. Follow us on twitter @Spacedotcom (opens in a new tab) and on Facebook (opens in a new tab).