The night sky offers us a variety of spectacles throughout the year, but for the remainder of the month, we have front-row seats to see — not one or two — but seven planets at once.
Mercury, Venus, Mars, Jupiter, Saturn, Neptune and Uranus are all visible in the night sky through the end of February. But what does that look like, and how do you find those planets among the stars?
To discuss this celestial phenomenon and share ways to best view it, the Michigan State University College of Natural Science sat down with two astronomy experts — Emily Elizondo, an MSU physics and astrophysics graduate student, and Darryl Seligman, an MSU postdoctoral fellow who is starting as faculty in the physics and astronomy department this fall — to answer these questions.
How rare is it for the planets to align?
Elizondo: The phenomenon of having planets aligned is not super rare. It happens every couple of years, but not to the extent that we are going to see it now. We’ll be seeing all seven at the end of the month. It’s probably more often you see three or four planets aligned.
What does it mean when we say the planets are aligned?
Elizondo: If you were to observe the sky from Earth, you’d see the planets look like they were in a curved line, and that’s them following the ecliptic, which is the apparent path that the sun takes in the sky. This is because the planets are at low inclination, so they’re in line with the plane of the sun. And if you were to zoom out and look at the orbits of the planets, they wouldn’t actually be in a line — they’d just be on the same side of the sun from our perspective on Earth. So that’s why we’d be able to see all of them in the sky.
Seligman: If you look at the three-dimensional view of the solar system, the planets are all in this very flat plane, like a disc. If you’re sitting on the Earth and all the planets were visible all of the time, you would see the alignment all the time. It’s just now they’re all visible. And just seeing them all trace out the ecliptic is interesting because in other exoplanetary systems they have found planets that are not aligned. So, it’s up to you to decide if you think that means the solar system is special or not, but everything is aligned in the solar system.
What is the best time to see this phenomenon?
Elizondo: Mercury started to come to view on Feb. 23, and it’ll be visible until the end of month, and then it will dip back below the horizon at the end of the month. The best time to view this is approximately 90 minutes after sunset.
Where should we look when we’re trying to see the planets?
Elizondo: The planets will be in the southern half of the sky. Toward the southwest is where Saturn and Mercury are going to be, and then toward the southeast is where Mars and Jupiter will be, and then Neptune, Venus and Uranus will be in between. There are apps that use motion-sensing technology, so you can type in the planet’s name, and it’ll show you where that planet is in the sky.
So, for those of us who have trouble seeing anything other than the Big Dipper, should we rely on an app for help?
Seligman: Funnily enough, knowing constellations and where things in the sky has nothing to do with what we as astronomers actually do on a day-to-day basis. We both do theoretical astrophysics too, so we don’t even observe very much. And even the people who observe a lot, they have some coordinates that they put in the telescope (or the telescope operator puts in). So, for most of us, it’s a running joke because most of us have no idea. Remember, the ecliptic is the path that the sun is taking. So that’s basically tracing out the plane of the solar system. And then all of this is a backdrop, and all the constellations are much further away.
How can you tell the difference between a star and a planet?
Elizondo: Stars twinkle in the sky. Planets don’t. Stars twinkle due to the light from the star interacting with the atmosphere, which distorts the light and makes it look like it’s twinkling. The planets don’t twinkle because they are a lot closer to the earth. They look like a disc rather than a point source, which prevents that sort of distortion. Planets are also brighter because they are closer, but there are some planets that are hard to see with the naked eye because they are a lot farther away compared to some stars, which can be massive and really bright.
Which of the planets is easiest to spot, and how can you tell which one you’re looking at?
Elizondo: Venus is the easiest to spot because it’s the brightest. It is right next to Earth, and it also contains clouds that are reflective, so that also helps it look a lot brighter. Jupiter and Saturn are bright because they are the largest of the planets.
Will we be able to see all the planets with the naked eye or is special equipment needed to see certain ones?
Elizondo: Typically, you can see all of them with the naked eye, aside from Neptune and Uranus, which are very far away — not only are they the farthest ones from us, but they’re also not as large.