Explore the Lagoon Nebula, Messier 8
Ordinary binoculars under a dark sky can bring the Lagoon Nebula to you from 5,000 light-years away. Look for M8 a few degrees above and to the right of the Teapot asterism in the constellation Sagittarius. M8 or Messier 8 is the formal designation for this nebula, which is a large gas cloud within our Milky Way galaxy. The Lagoon Nebula is barely visible to the human eye under good conditions, but glorious with a dark sky and a bit of optical aid.
How to find the Lagoon Nebula
You can enjoy great views of M8, but first you have to find it. Let’s start with when to look. For the Northern Hemisphere, mid-summer to mid-fall are ideal. (Or in the Southern Hemisphere, mid-winter to mid-spring.) By early July each year, this object is crossing the meridian – appearing highest in the sky – at midnight. By early September it’s crossing the meridian as darkness falls, making it prime for early evening observations.
Next, pick a night close to new moon and an observing spot that is far from interfering lights to ensure a dark sky and optimal viewing conditions. Visit EarthSky’s Best Places to Stargaze page to find a good viewing location near you.
Then, look for the constellation Sagittarius, which marks the direction of the center of our Milky Way galaxy. You’ll be looking southward in the evening from Earth’s Northern Hemisphere. If you’re in Earth’s Southern Hemisphere, look northward, closer to overhead, and turn the charts below upside-down. Want a more exact location for Sagittarius? We hear good things about Stellarium, which will let you set a date and time from your exact location on the globe.
What you’ll see
The Lagoon Nebula spans an area of sky about three times the size of the full moon. The largest and brightest of a number of nebulosities in and around Sagittarius, it’s widely visible throughout populated areas of North America. Due to its location in the sky (-24 degrees declination), observers farther south see it even higher in the sky, which is better for observing.
As just a very faint patch to the unaided eye, the nebula takes on an oblong shape in binoculars. A brighter nucleus (the so-called “hourglass”) is visible on one side, separated by a dark rift from an open star cluster on the other side. Unlike the published timed-exposure photographs, to the unaided eye the faint nebulosity appears grayish with little if any hint of color.
M8 is about 5,000 light-years away, and roughly 130 light-years in length. The Lagoon Nebula is an emission nebula, composed primarily of hydrogen, much of it ionized (heated or energized) by radiation from the nearby young and massive star Herschel 36. It’s also a star-forming region, or stellar nursery, a place where new stars are being born. An open star cluster – NGC 6530 – of young, hot, blue stars just a few million years old lies in this region. In addition to these young stars, there are also many dark Bok globules (dark nebulae) of condensing gas and dust on their way to becoming protostars and ultimately full-fledged stars like those already formed nearby.
Early observations of the Lagoon
While the fanciful name Lagoon might suggest a mythical origin, there is no known mythology associated directly with this interstellar cloud. The name apparently refers to the shape with the dark lane through the middle, not unlike two lagoons separated by a sandbar. While visible to the unaided eye and therefore certainly seen in antiquity, there is no known mention of this nebula until 1654, when Sicilian astronomer Giovanni Battista Hodierna recorded his observations of the star cluster within the nebula.
The area was observed by several other astronomers, including Charles Messier in 1764, after which it ultimately also became known as Messier 8, or M8, the eighth object in Messier’s catalog.
The Lagoon Nebula’s approximate center position is RA: 18h 04m, declination: -24° 22′.
Bottom line: The Lagoon Nebula, or Messier 8, is a large emission nebula in the constellation Sagittarius that observers can explore with binoculars.