Discovering the Universe Through the Constellation Orion
Do you ever look up at the night sky and get lost in the stars? Maybe while you’re stargazing, you spot some of your favorite constellations. But did you know there’s more to constellations than meets the eye? They’re not just a bunch of imaginary shapes made up of stars — constellations tell us stories about the universe from our perspective on Earth.
What is a constellation?
A constellation is a named pattern of stars that looks like a particular shape. Think of it like connecting the dots. If you join the dots — stars, in this case — and use your imagination, the picture would look like an object, animal, or person. For example, the ancient Greeks believed an arrangement of stars in the sky looked like a giant hunter with a sword attached to his belt, so they named it after a famous hunter in their mythology, Orion. It’s one of the most recognizable constellations in the night sky and can be seen around the world. The easiest way to find Orion is to go outside on a clear night and look for three bright stars close together in an almost-straight line. These three stars represent Orion's belt. Two brighter stars to the north mark his shoulders, and two more to the south represent his feet.
Over time, cultures around the world have had different names and numbers of constellations depending on what people thought they saw. Today, there are 88 officially recognized constellations. Though these constellations are generally based on what we can see with our unaided eyes, scientists have also invented unofficial constellations for objects that can only be seen in gamma rays, the highest-energy form of light.
Perspective is everything
The stars in constellations may look close to each other from our point of view here on Earth, but in space they might be really far apart. For example, Alnitak, the star at the left side of Orion's belt, is about 800 light-years away. Alnilam, the star in the middle of the belt, is about 1,300 light-years away. And Mintaka, the star at the right side of the belt, is about 900 light-years away. Yet they all appear from Earth to have the same brightness. Space is three-dimensional, so if you were looking at the stars that make up the constellation Orion from another part of our galaxy, you might see an entirely different pattern!
The superstars of Orion
Now that we know a little bit more about constellations, let’s talk about the supercool cosmic objects that form them – stars! Though over a dozen stars make up Orion, two take center stage. The red supergiant Betelgeuse (Orion's right shoulder) and blue supergiant Rigel (Orion's left foot) stand out as the brightest members in the constellation.
Credit: Derrick Lim
Betelgeuse is a young star by stellar standards, about 10 million years old, compared to our nearly 5 billion-year-old Sun. The star is so huge that if it replaced the Sun at the center of our solar system, it would extend past the main asteroid belt between Mars and Jupiter! But due to its giant mass, it leads a fast and furious life.
Betelgeuse is destined to end in a supernova blast. Scientists discovered a mysterious dimming of Betelgeuse in late 2019 caused by a traumatic outburst that some believed was a precursor to this cosmic event. Though we don’t know if this incident is directly related to an imminent supernova, there’s a tiny chance it might happen in your lifetime. But don't worry, Betelgeuse is about 550 light-years away, so this event wouldn't be dangerous to us – but it would be a spectacular sight.
Rigel is also a young star, estimated to be 8 million years old. Like Betelgeuse, Rigel is much larger and heavier than our Sun. Its surface is thousands of degrees hotter than Betelgeuse, though, making it shine blue-white rather than red. These colors are even noticeable from Earth. Although Rigel is farther from Earth than Betelgeuse (about 860 light-years away), it is intrinsically brighter than its companion, making it the brightest star in Orion and one of the brightest stars in the night sky.
Credit: Rogelio Bernal Andreo
Buckle up for Orion’s belt
Some dots that make up constellations are actually more than one star, but from a great distance they look like a single object. Remember Mintaka, the star at the far right side of Orion's belt? It is not just a single star, but actually five stars in a complex star system.
Credit: X-ray: NASA/CXC/GSFC/M. Corcoran et al.; Optical: Eckhard Slawik
Sword or a stellar nursery?
Below the three bright stars of Orion’s belt lies his sword, where you can find the famous Orion Nebula. The nebula is only 1,300 light-years away, making it the closest large star-forming region to Earth. Because of its brightness and prominent location just below Orion’s belt, you can actually spot the Orion Nebula from Earth! But with a pair of binoculars, you can get a much more detailed view of the stellar nursery. It’s best visible in January and looks like a fuzzy “star” in the middle of Orion’s sword.
More to discover in constellations
In addition to newborn stars, Orion also has some other awesome cosmic objects hanging around. Scientists have discovered exoplanets, or planets outside of our solar system, orbiting stars there. One of those planets is a giant gas world three times more massive than Jupiter. It’s estimated that on average there is at least one planet for every star in our galaxy. Just think of all the worlds you may be seeing when you look up at the night sky!
It’s also possible that the Orion Nebula might be home to a black hole, making it the closest known black hole to Earth. Though we may never detect it, because no light can escape black holes, making them invisible. However, space telescopes with special instruments can help find black holes. They can observe the behavior of material and stars that are very close to black holes, helping scientists find clues that can lead them closer to discovering some of these most bizarre and fascinating objects in the cosmos.
Next time you go stargazing, remember that there’s more to the constellations than meets the eye. Let them guide you to some of the most incredible and mysterious objects of the cosmos — young stars, brilliant nebulae, new worlds, star systems, and even galaxies!
To keep up with the most recent stellar news, follow NASA Universe on Twitter and Facebook.
Make sure to follow us on Tumblr for your regular dose of space!
3K notes · View notes
Weird and Wonderful Irregular Galaxies
Spiral and elliptical galaxies seem neatly put together, but what happened to irregular galaxies? Irregular galaxies have one-of-a-kind shapes and many look like blobs! Why do they look the way they do? Astronomers think the uniqueness of these galaxies results from their interactions with other galaxies — like when they pass close to one another or even collide!
Looking back at the early universe with the help of our Hubble Space Telescope’s “deep field” observations, astronomers can peek at galaxies millions and billions of light-years away. They noticed that these far-away galaxies appear unusually messy, showing more star formation and mergers than galaxies closer to the Milky Way.
We also see irregular galaxies closer to home, though. Some may form when two galaxies pass close together in a near-miss. When this happens, their gravity pulls stars out of place in both galaxies, messing up the neat structure they originally had as spiral or elliptical galaxies. Think of it like this: you happen to have a pile of papers sitting at the edge of a table and when someone passes close by the papers become ruffled and may scatter everywhere! Even though the two galaxies never touched, gravity's effects leave them looking smeared or distorted.
Some irregular galaxies result from the collision between two galaxies. And while some of these look like a blob of stars and dust, others form dazzling ring galaxies! Scientists think these may be a product of collisions between small and large galaxies. These collisions cause ripples that disturb both galaxies, throwing dust, gas, and stars outward. When this happens, it pushes out a ring of material, causing gas clouds to collide and spark the birth of new stars. After just a few million years, stars larger than our Sun explode as supernovae, leaving neutron stars and black holes throughout the ring!
Not all galaxy collisions create irregular galaxies — our Milky Way spiral galaxy has gone through many mergers but has stayed intact! And for some interacting galaxies, being an irregular galaxy may just be a phase in their transformation. We’re observing them at a snapshot in time where things are messy, but they may eventually become neat and structured spirals and ellipticals.
Irregular galaxies are similar to each other, but unique and beautiful because of their different interactions, whether they’re just passing another galaxy or taking part in a dramatic collision. Keep up with NASA Universe on Facebook and Twitter where we post regularly about galaxies.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.
3K notes · View notes
Deep Sky towards Andromeda
Today's image comes curtesy of APOD, an image of the greater area of sky surrounding the Andromeda Galaxy M31.
Towards the top is M33, the Triangulum galaxy sometimes called the Pinwheel (however so is M101 in Ursa Major, so seems to be some confusion between amateur astronomers).
At a distance of just 3.2 million light years, it's one of the closest and large galaxies in our local neighbourhood. What you're really seeing is 40 billion stars stretched out over 60,000 light years as it was 3.2 million years ago.
Sivan 2, regions of ionised hydrogen gas bombarded by ultra violet light from new born stars which then emits its own light glow as a result, what is termed as an emissions nebula.
SH2 - 126 Nebula, another example of ionized hydrogen gas emitting light through bombardment of UV from a nearby new star.
Then of course there is the centre piece, the Andromeda Galaxy M31 which in 5 billion years from now will be merging with our Milky Way, just as our own sun turns red giant.
323 notes · View notes