Have you ever gazed at the night sky hoping to spot the dazzling band of gas clouds, nebulae, and stars known as our Milky Way, only to be disappointed by the full Moon outshining everything in the celestial mosaic? Were you left scratching your head after discovering, despite existing around our solar system, the Milky Way isn’t visible year-round?
Whether you’ve been troubled by elusive night sky objects, or you just want to learn a bit more about visual astronomy, this viewing guide will give you the tools you need to predict the best times to view the Milky Way, regardless of where you are on the planet.
TL;DR: Tracking the Milky Way with diagrams and charts—like those featured below—can be a great way to deepen your understanding of the cosmos, but it's not the only way to get familiar with our celestial backyard. With a free software like Star Walk or Stellarium, you can swiftly track numerous celestial objects from the palm of your hand. After all, what's important is getting out there and learning about our universe, not how you track the night sky!
Before diving into the specifics of Milky Way viewing, it’s helpful to review some functional facts about our galactic perspective.
Our Sun orbits the galactic core: Once every 230 million years, the Sun completes a wobbly orbit around the core of our galaxy. The last time Earth was on this side of the galaxy, the dinosaurs were just beginning to roam the massive supercontinent called Pangea!
Our Sun is a disk-star: Unlike the stars found in the halo of our galaxy, as the Sun orbits the galactic core, it stays within the confines of the galactic disk. This orbital path isn’t a neat elliptical orbit like our planet. Instead, the Sun follows a wavelike path, moving to either side of the galactic disk every 1000 years.
Our solar system (ecliptic plane) is tilted: Due to the conservation of angular momentum, as our solar system formed, the ecliptic plane, or the plane on which all the planets orbit, began to tilt forward. When compared to the galactic disk, our celestial equator is tilted at about 60°.
The Milky Way is just one part of the overall galactic structure: Our galaxy is a massive spiraling structure with four main arms wrapping around a bright galactic core. Since we are located near the edge of this structure (within the Orion Spur of the Sagittarius arm), what we can view from our local vantage point is a combination of the Scutum-Centaurus arm overlaying the more luminous galactic core.
Now that you’ve oriented yourself to our local galactic perspective, let’s head back down to Earth and explore the tools needed to predict the best viewing times to spot the Milky Way!
- We know the Sun orbits the galactic core, and the ecliptic plane is tilted 60° to the overall galactic disk.
- We also know that Earth orbits the Sun once every 365.25 days and Earth is tilted to the celestial equator by about 23°.
So, all we need to do now is bring this all together; unfortunately, words will only help so much when dealing with these complex mechanics. If you’re struggling to cram the entire galaxy into your head, check out the diagrams below.
In the first diagram, you can see Earth begins its approach to the galactic core in February, reaches towards the end of June, and begins to move away from the galactic core in September. So, depending on where our planet is positioned in its orbital path, the Sun will either be between Earth and the Galactic Core, beside Earth, or behind Earth. It just so happens that this alignment conveniently lines up with our summer and winter solstices!
Now that you know how to predict the best time of year to spot the Milky Way, the next step is understanding the best time of night.
This next diagram shows Earth's orbital path around the Sun, the general direction of the galactic core, Earth's tilt, and rotational direction. Much like the Sun, the galactic core rises and falls in the night sky as Earth rotates around its axis. Depending on the time of year, the galactic core will either rise in the evening, late in the night, or early in the morning.
February: Near the end of February, the Earth begins moving towards the galactic core in its orbital path around the Sun. As the Earth turns counter clockwise around its axis, the galactic core will first appear in the mid-morning hours, rising on the eastern horizon. It will be briefly visible until twilight begins and the Sun outshines its celestial co-star.
March-May: Through the months of March, April, and May, the galactic core will rise on the eastern horizon earlier each day. Near the end of April, the galactic core will rise on the eastern horizon around or before midnight.
June: Through the month of June, the galactic core will rise earlier in the evening. By the summer solstice for the Northern Hemisphere, the galactic core will rise on the eastern horizon shortly after the Sun sets, and it will reach the highest point in the night sky around Solar midnight, or the half way mark between dusk and dawn. It’s important to keep in mind that while the galactic core will be visible nearly all night long, it will be brightest when it reaches your zenith—the point directly above your head when standing upright—as its light travels through less of the atmosphere to reach your eyes or camera sensor.
July-September: During the months of July, August, and September, the galactic core will rise earlier in the evening as each day passes. By early September, it will rise on the eastern horizon before the Sun sets. During this window, you will have to wait for the evening twilight to fade before viewing the galactic core, but don’t wait too long; it will set on the western horizon shortly after solar midnight.
October-November: The viewing window for the galactic core will shrink as it begins to rise earlier in the afternoon. By the end of November, it will be briefly visible near the western horizon after the Sun sets. However, the lingering glow of the Sun will make it far too faint to observe with the naked eye.
December-January: Since the Sun stays between Earth and the galactic core during this part of the year, viewing isn’t likely.
And that’s it! Now you have the information to get out there and see the Milky Way…
…Or do you? While you now have the information to predict the best Milky Way viewing window, before you start planning a star-struck summer vacation, it’s important to remember theory only gets us so far. Below you will find some practical tips to keep in mind when planning to view or image the Milky Way.
Lunar cycles: While the Moon is a beautiful part of our night sky, it can be quite the eyesore if you are hoping to view the Milky Way. The lunar cycle is only 29.5 days, and there are several nights during the viewing window when the Moon won’t create enough sky-glow to obstruct the Milky Way. Check out this article to understand the complexities of the lunar cycle!
Light pollution: Don’t set yourself up for disappointment! Light pollution and atmospheric conditions can be a real problem for any astronomer, regardless of experience. Check out this helpful article on the Bortle scale to better understand how light pollution will affect your ability to view the Milky Way. Be sure to review the local weather conditions as well!
Latitude: While the viewing window is the same regardless of where you are on the planet, it’s worth considering the way latitudinal positioning can change your view of the night sky. We mentioned in an earlier section that the celestial equator is tilted 60° to the galactic disk and Earth is further tilted about 23° to the celestial equator. How does this impact viewing? The combined angle of these two tilts means the galactic disk is nearly perpendicular to the rotation of Earth. So, the galactic core will (roughly) stretch north to south as it moves across the night sky. Those in lower latitudes are situated so the galactic core is nearly in the middle of the sky (when it’s highest in the night sky). Depending on which hemisphere you are in, the core will either shift to the north or south as you move higher in latitude.
Now that you've learned how to orient yourself to our galactic perspective—or downloaded an app to help you track the night sky—it's time to get out there and put your skills to the test!
Learn More
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Glossary
Bortle Scale
The Bortle scale measures how light polluted a particular area is, and classifies the level of brightness from 1 to 9, with 9 being the brightest. This scale is incredibly helpful for astronomers, as the darker the sky, the more celestial objects are able to be discerned.
Disk Star
Young stars found within the galactic disk of a spiral galaxy are known as disk stars, or population I stars. Their chemical composition and position in a galaxy make them distinct from population II and III stars.
Earth
Also known as the Pale Blue Dot, Earth is the unique planet we are standing on right now. It's located between Venus and Mars in the goldilocks zone of our solar system, making it the third planet from the Sun. Our Earth is estimated to be around four billion years old, and is currently the only known planet to support the necessary conditions for life.
Ecliptic Plane
First described by the Greek astronomer and mathematician Hipparchus, the ecliptic plane is an imaginary two dimensional plane on which planets orbit their host star. Not all celestial objects are confined to the ecliptic plane. For example, Pluto's orbit is titled by about 17° when compared to the other planets and dwarf planets, making is the largest object to deviate from the ecliptic plane.
Galactic Arm
Galactic arms are the massive bands of ionized gas, dust, stars, and nebulae that stretch out from the center of a spiral galaxy. The arms of a spiral galaxy are a vital part of the life cycle of population I stars and planetary nebulae.
Galactic Core
The galactic core, also known as the galactic nucleus, is the luminous center point of a ecliptic and spiral galaxies. In our galaxy, the galactic core is home to a supermassive black hole know as Sagittarius A.
Galactic Disk
The relatively thin plane within which various stars, dust clouds, and nebulae travel around the center point of a spiral galaxy. The Milky Way galaxy’s Galactic disk is around 1000 light years thick, and 100,000 light years wide.
Galactic Halo
The halo is the luminous structure surrounding the galactic nucleus. It ranges in size and shape depending on the type of galaxy. In spiral galaxies, like our Milky Way galaxy, the halo elongated and shaped similarly to a football.
Galaxy
Galaxies are massive collections of various celestial objects, and structurers, that share a common orbital path around a galactic nucleus. The three types of galaxies are spiral, elliptical, and irregular.
Interstellar clouds
Interstellar clouds are a collection of various elemental gasses, dust, and plasma left over from various galactic events, such has supernovas, galactic collisions, and even the big bang.
Latitude
Latitude is one of two coordinates used to find a position on a globe. Lower latitudes are closer to the equator, while higher latitudes are closer to the poles.
Light pollution
Light pollution is the brightening of the atmosphere due to lights from street lamps, other forms of artificial light, and even the Moon. As light enters the atmosphere, it washes out the night sky, making it very difficult to observe the stars, nebulae, and planets. In order to combat light pollution in astrophotography, special filters have been developed to cut through excess light and enhance images. These filters are known as City Light Suppression filters, commonly referred to as CLS filters.
Milky Way
The Milky Way is the name of the galaxy that hosts our solar system. Named for its bright milky appearance in the night sky, the Milky Way is home to countless stars, nebulae, and a even a few supermassive black holes. It estimated to be over 13 billion years old, and it would take over 100,000 light years to travel from one side to the other.
Moon
A moon is a naturally occurring object that orbits a planet or other celestial bodies (excluding stars). These are also called natural satellites. The Moon, capitalized is the Earth's only natural satellite and is the brightest object in the night sky. The Moon stabilizes the tilt Earth's orbit, causing the seasons, and tides.
Nadir
The nadir is geometrical term which describes an imaginary line running below and perpendicular to a two dimensional plane. In the context of visual astronomy, it refers to the point directly below you when standing upright. While less commonly used than its opposing term zenith, it can be useful when describing the location of objects that are below your celestial horizon.
Nebula
A nebula is a type of celestial body that is made up of gas and/or dust. There are 3 different types of nebulae within space. Emission nebulae have a “glowing” effect, where they absorb and emit light from surrounding stars. The colors emitted are entirely dependent on the gasses present within the nebulae itself. This type of nebula also includes planetary nebula and supernova remnants, produced by stars themselves. As opposed to emitting light itself, reflection nebulae reflect starlight from neighboring stars. Reflection nebulae are typically blue in color, such as the Pleiades or the Running Man Nebula. The last type of nebulae is dark nebulae, which blocks stars and other objects from our view, creating a dark silhouette.
Orbit
An orbit is a predictable and periodic path an object follows as it moves through the space-time warped by a more massive celestial object. We have known about celestial orbits since early antiquity, however, it was not until Johannes Kepler formalized the three laws of planetary motion that we gained the ability to acutely predict the movements of our planetary neighbors.
Planet
A planet is a type of celestial body that is created as the proto-planetary disk of a young star system is pulled inwards towards the host star. As this disk contracts, its matter condenses into asteroids, comets, and ionized gas clouds. These celestial objects inevitably collide with one another to form protoplanets, dwarf planets, and eventually, planets like those easily viewed in our night sky.
Seeing Conditions
This term refers to the overall clarity of the night sky at any given time and within any given location. This clarity fluctuates constantly, as it is based on numerous different atmospheric conditions, such as humidity, turbulence, high clouds, heat, and plenty more. To give an example, you may have witnessed stars in the night sky “twinkle.” This is due to our atmosphere distorting their incoming light, causing a twinkling effect. When it comes to astronomy, especially when observing the planets and the Moon, seeing conditions are very important to consider, as these distortions can cause the subjects to become blurred and unfocused. It’s best practice to observe celestial objects when the atmosphere is most stable.
Sky Glow
As light interacts with the various component chemicals that make up our atmosphere, it occasionally changes direction and intensity. We perceive this interaction as a reduction in the transparency of our atmosphere, which can impact the visibility of objects in the night sky. Sky glow can be caused by terrestrial light pollution, sunlight, and even moonlight.
Solar Midnight
Unlike true midnight, solar midnight is the point where the Sun is closest to your nadir (the point directly below your feet). Solar midnight also delineates the half way mark between dusk and dawn.
Solar noon
Unlike true noon, solar noon is the point where the Sun is closest to your zenith (the point directly above your head when standing upright). Solar noon also delineates the half way mark between dawn and dusk.
Solar System
A solar system is any collection of celestial objects, and structures, found orbiting a star, or set of stars. Our solar system is home to many planets, dwarf planets, comets, and asteroids, but these are just some of the celestial objects that come together to form a solar system.
Star
A star is a luminous sphere of plasma held together by the collective gravitational attraction of hydrogen and helium atoms. Stars also contain various trace elements, such as lithium, carbon, and towards the end of there life cycle, iron. Stars come in many temperatures, colors, and sizes. High mass stars like Betelgeuse appear to shine red from our perspective because our eyes are only sensitive to a small portion of the electromagnetic spectrum. To see the true luminosity of Betelgeuse, you need specialized equipment designed to capture the appropriate wavelength of light.
Summer Solstice
Also known as the Estival solstice, the summer solstice is the day with the longest duration of daylight hours. It occurs twice every year, once for each hemisphere.
Sun
The Sun is the star in which our planet (others in our solar system) orbit around. Like other stars, the Sun is a luminous sphere of plasma held together by the collective gravitational attraction of hydrogen and helium atoms.
Visual Observation
Visual observation is the study of celestial objects using specialized visual equipment like telescopes and binoculars, or simply viewing the sky with your naked eye. Born from our species' first attempts to understand the many mysterious objects that fill our night sky, visual astronomy has blossomed into an expansive field of study, and inspired many to join in the pursuit of knowledge that beckoned our curious ancestors.
Winter Solstice
Also known as the Hibernal Solstice, the winter solstice is the day with the shortest duration of daylight hours. Its occurs twice every year, once for each hemisphere.
Zenith
The zenith is commonly used geometrical term which describes an imaginary line running above and perpendicular to a two dimensional plane. For visual astronomy, the zenith simply refers to the point directly above your head when standing upright, and can be a useful point of reference when describing the position of celestial objects in our night sky.
