Which Planets Are Visible To The Unaided Eye

which planets are visible to the unaided eye

“Which planets are visible to the unaided eye?” someone will sometimes ask me when they learn that I am an amateur astronomer. Also, I sometimes get people asking me if there is anything interesting to see in the nighttime sky besides the moon.  When I tell them that they can see some of the planets, they are completely stunned. So I decided to write an article about this topic and answer the question once and for all in a blog entry that will be posted and available on the Internet for the entire world to see.

The five brightest planets – Mercury, Venus, Mars, Jupiter, and Saturn can easily be seen with the naked eye if one knows when and where to look. They are visible for much of the year, except for short periods of time when they are too close to the Sun to observe. All of the planets will not normally be visible on a single night, however.

Now that you know which planets are visible to the unaided eye, the next question is how can you find them in the night sky?

Three Methods To Determine When and Where To Look For Planets

Method 1 – Use the “Old School” method of reading star and planetary charts

If you make a quick to trip the public library, you should be able to find charts that map the positions of the celestial bodies in the skies above us. Keep in mind that for our purposes we’ll only be able to make a rough approximation of the positions. Here are a few tips to help you get oriented to the night sky.

  1. Establish a point of reference – Determine which way is North and face in that direction. While facing north, locate the North Star (Polaris). Once you’ve identified the North Star, you can use it as your reference for all other objects. (Optionally, you can also use the moon as an alternative reference point. While the moon is an easier object to find in the night sky, it will require more effort on your part to translate the position of celestial objects relative to the moon)
  2. Use altitude and azimuth information from the charts to direct your view to the desired object.  Starting from your initial position and straight out into the horizon, that is North at 0 degrees of altitude.
  3. Azimuth approximation – By definition, the azimuth is the direction of a celestial object, measured clockwise around the observer’s horizon from the north. So an object due north has an azimuth of 0°, one due east 90°, south 180° and west 270°. If you are facing north and extend your right arm straight out from your body, your arm will be pointing east (90 degrees). South (180 degrees) will be directly behind you. If you extend your left arm straight out from your body, your arm will be pointing west (270 degrees).  Using these very rough azimuth references, turn your body so that you are facing the same direction as the desired object.
  4. Altitude approximation – Looking at the horizon is 0 degrees and straight up is 90 degrees of altitude. Halfway between the horizon and straight up is 45 degrees of altitude. If you take half the angle between the horizon and 45 degrees, your view will be at 22.5 degrees. Similarly, if you take half the angle between 45 degrees and straight up (90 degrees), your view will be at 67.5 degrees.
  5. Please keep in mind that these are very rough approximations, since pinpointing the exact location of a celestial object with any precision will require taking into account and adjusting for your physical location on Earth and the current time.

As an alternative to going to the library, you could also purchase a book to add to your own personal library. In the table below, are several books that we have found super useful.

Title

Author

Check Price On Amazon

“Discover The Stars” Richard Berry Check Price
“NightWatch: A Practical Guide To Viewing The Universe” Terrence Dickinson Check Price
“2018 Guide To The Night Sky: A Month-to-Month Guide To Exploring The Skies Above North America” Storm Dunlop and Will Tirion Check Price
“50 Things To See With A Small Telescope” John Read Check Price
“Astronomy With A Home Telescope: The Top 50 Celestial Bodies To Discover In The Night Sky” Seth Penricke Check Price

Three Methods To Determine When and Where To Look For Planets

Method 1 – Use the “Old School” method of reading star and planetary charts

If you make a quick to trip the public library, you should be able to find charts that map the positions of the celestial bodies in the skies above us. Keep in mind that for our purposes we’ll only be able to make a rough approximation of the positions. Here are a few tips to help you get oriented to the night sky.

  1. Establish a point of reference – Determine which way is North and face in that direction. While facing north, locate the North Star (Polaris). Once you’ve identified the North Star, you can use it as your reference for all other objects. (Optionally, you can also use the moon as an alternative reference point. While the moon is an easier object to find in the night sky, it will require more effort on your part to translate the position of celestial objects relative to the moon)
  2. Use altitude and azimuth information from the charts to direct your view to the desired object.  Starting from your initial position and straight out into the horizon, that is North at 0 degrees of altitude.
  3. Azimuth approximation – By definition, the azimuth is the direction of a celestial object, measured clockwise around the observer’s horizon from north. So an object due north has an azimuth of 0°, one due east 90°, south 180° and west 270°. If you are facing north and extend your right arm straight out from your body, your arm will be pointing east (90 degrees). South (180 degrees) will be directly behind you. If you extend your left arm straight out from your body, your arm will be pointing west (270 degrees).  Using these very rough azimuth references, turn your body so that you are facing the same direction as the desired object.
  4. Altitude approximation – Looking at the horizon is 0 degrees and straight up is 90 degrees of altitude. Halfway between the horizon and straight up is 45 degrees of altitude. If you take half the angle between the horizon and 45 degrees, your view will be at 22.5 degrees. Similarly, if you take half the angle between 45 degrees and straight up (90 degrees), your view will be at 67.5 degrees.
  5. Please keep in mind that these are very rough approximations, since pinpointing the exact location of a celestial object with any precision will require taking into account and adjusting for your physical location on Earth and the current time.

As an alternative to going to the library, you could also purchase a book to add to your own personal library. Here are several that we have found super useful:

“Discover The Stars”, by Richard Berry

<Click Here To Check The Latest Amazon Price>

http://amzn.to/2ARLe6G

“NightWatch: A Practical Guide To Viewing The Universe”, by Firefly Books

<Click Here To Check The Latest Amazon Price>

http://amzn.to/2ASV3B9

“2018 Guide To The Night Sky: A Month-to-Month Guide To Exploring The Skies Above North America”, by Storm Dunlop and Will Tirion

<Click Here To Check The Latest Amazon Price>

http://amzn.to/2C93etl

“50 Things To See With A Small Telescope”, by John Read

<Click Here To Check The Latest Amazon Price>

http://amzn.to/2BXNf0s

“Astronomy With A Home Telescope: The Top 50 Celestial Bodies To Discover In The Night Sky”, by Seth Penricke

<Click Here To Check The Latest Amazon Price>

http://amzn.to/2Cbzhsz

Method 2 – Check Online !

If during your viewing session you have access to a computer or smartphone, you can always visit websites online that publish sky charts. Typically the sky charts are published every month and provide approximate of locations of objects based upon time of viewing. One of my favorites is Astronomy.com.  They publish a Sky Guide (http://www.astronomy.com/sky-guide) that is very helpful in locating the planets, but also other cosmic events as well.

Here are some links to other online planet and star charts (in alphabetical order):

The advantage of using an online chart is that you can be reasonably assured that the data is up-to-date, plus you can specify chart map for different locations and times (pretty handy if you’re curious what the night sky looks like in other parts of the world).

Be sure to give them a try and identify your favorite one, then bookmark it in your browser so that you can always find it quickly.

Method 2 – Check Online !

If during your viewing session you have access to a computer or smartphone, you can always visit websites online that publish sky charts. Typically the sky charts are published every month and provide approximate of locations of objects based upon time of viewing. One of my favorites is Astronomy.com.  They publish a Sky Guide (http://www.astronomy.com/sky-guide) that is very helpful in locating the planets, but also other cosmic events as well.

Here are some links to other online planet and star charts (in alphabetical order):

  • AstroViewer.com
  • SkyMapOnline.net
  • StelVision.com
  • TheSkyLive.com

The advantage of using an online chart is that you can be reasonably assured that the data is up-to-date, plus you can specify chart map for different locations and times (pretty handy if you’re curious what the night sky looks like in other parts of the world).

Be sure to give them a try and identify your favorite one, then bookmark it in your browser so that you can always find it quickly.

Method 3 – Get An Interactive App !

If you have a smartphone, you can install the “SkyView” app. It is available for both iPhones and Android phones. SkyView is available in a LITE version (free) and also a paid version (more features and capabilities).

SkyView on iPhone

SkyView on iPhone

skyview android

SkyView on Android device

SkyView in Night Mode

SkyView in Night Mode

The “lite” version of the app makes stargazing easy and accessible to everyone! Simply install the app, and then just point your device at the sky to identify stars, constellations, satellites, and more!

The app also include a special Night Mode, where all of the screen information is only rendered in the color red, thus saving your night vision eyesight.

There is also a version made specifically for the iPad, so tablet users can joining on the fun as well !

SkyView on iPad

SkyView is also available for the iPad

Method 3 – Get An Interactive App !

If you have a smartphone, you can install the “SkyView” app. It is available for both iPhones and Android phones. SkyView is available in a LITE version (free) and also a paid version (more features and capabilities). There is also a version made specifically for the iPad, so tablet users can joining on the fun as well !

<< INSERT SCREENSHOT>>

This application is developed and maintained by Terminal Eleven, LLC.

Five Tips For Improving Your Viewing Session

  1. Choose a evening when the night sky is clear and not overcast (obviously!). If it’s cold, wear appropriate clothing to stay warm.
  2. Allow ample time for your eyes to adjust to the darkness, at least 30-40 minutes.
  3. Dim the lights on any equipment that you have with you, this include power indicator lights, warning / safety lights, laptop computers, tablet computers and of course cell phones.
  4. If need to have a light source, such as a small flashlight, be sure the light emitted is red (either a red bulb or red lens cover).
  5. Take vitamin A on a regular basis. While taking regular doses of vitamin will no improve night vision, it may help in prevent night blindness.

Five Tips For Improving Your Viewing Session

  1. Choose a evening when the night sky is clear and not overcast (obviously!). If it’s cold, wear appropriate clothing to stay warm,
  2. Allow ample time for your eyes to adjust to the darkness, at least 30-40 minutes.
  3. Dim the lights on any equipment that you have with you, this include power indicator lights, warning / safety lights, laptop computers, tablet computers and of course cell phones.
  4. If need to have a light source, such as a small flashlight, be sure the light emitted is red (either a red bulb or red lens cover).
  5. Take vitamin A on a regular basis. While taking regular doses of vitamin will no improve night vision, it may help in prevent night blindness.

What Light Source Allows Us To See Stars And Planets ?

At this point, we need to consider the light that emanates from the stars and planets.

Stars generate their own light as a reaction of the nuclear fusion activity. Take the Earth’s Sun for example, atoms of hydrogen combine to form helium, which results production of HUGE amounts of heat and light. So even though stars are physical large and they are the direct source of their own light, their remote distance makes them appear as a tiny dot in the night sky.

Planets on the other hand, do not produce any significant, sustained light on their own. The surface of the planet just reflects the light it receives from the Sun back into outer space. The amount of light reflected from a planet depends upon a number of factors including the size of the planet, whether it has any cloud cover, and the reflectivity of the planet’s surface. The brightness of a planet to the unaided eye will depend upon a number of factors: the planet’s distance from the Sun, it’s apparent size ((i.e. the angular size when viewed from the Earth), and the relative positions of the planet and the Earth in their orbits.

What Is The Light Source That Allows Us To See Stars And Planets ?

At this point, we need to consider the light that emanates from the stars and planets.

Stars generate their own light as a reaction of the nuclear fusion activity. Take the Earth’s Sun for example, atoms of hydrogen combine to form helium, which results production of HUGE amounts of heat and light. So even though stars are physical large and they are the direct source of their own light, their remote distance makes them appear as a tiny dot in the night sky.

Planets on the other hand, do not produce any significant, sustained light on their own. The surface of the planet just reflects the light it receives from the Sun back into outer space. The amount of light reflected from a planet depends upon a number of factors including the size of the planet, whether it has any cloud cover, and the reflectivity of the planet’s surface. The brightness of a planet to the unaided eye will depend upon a number of factors: the planet’s distance from the Sun, it’s apparent size ((i.e. the angular size when viewed from the Earth), and the relative positions of the planet and the Earth in their orbits.

Why Do Star Twinkle ?   How To Tell The Difference Between A Planet and A Star

When viewing planets and stars with an unaided eye, there is a simple trick that allows you to quickly distinguish between them.

“Objects that appear to twinkle/blink are stars, And objects that exhibit a constant level of light are planets”

This is a general rule-of-thumb, but for the most part (99.99% of the time) it holds true.  So why is it… why do stars twinkle?  First, understand that stars are located enormous distances away from our planet, and as a result, we only see them as very small points of light that twinkle because they are affected by the turbulence in the Earth’s atmosphere. The atmospheric turbulence act like lenses and prisms affect the light’s path. The official scientific term for this twinkling phenomenon is “scintillate”. In simple terms, twinkling of stars is caused by the passing of light through the different layers of Earth’s turbulent atmosphere. As an observer, you will probably notice the scintillation effects are more pronounced when viewing stars that are located closer to the horizon, this is because the light entering through the horizon is passing through a much thicker layer of the Earth’s atmosphere.

As for planets, they are located much closer to Earth and the light reflected from them are more easily resolved through the atmosphere.  With their relative close proximity, the light they reflect is comprised of many rays of lights that pierce through the atmosphere so that they can be resolved as an object with an observable diameter. With the multiple rays of light traversing the atmospheric turbulence, the deviations tend to average out to the extent that the observer has less of a perceived variation in light. In other words, the scintillation effect is so slight that the light from the object appears constant. So with an unaided eye, the planets are close enough to the Earth that they appear as a small disk in the night sky. There are exceptions, and two of the planets, Mars and Saturn, may sometimes be mis-identified as stars during their more distant orbits when they are noticeably dimmer and could suffer the effects of scintillation.

The Mystery Viewing Planets vs. Stars Is Solved

With the information you have acquired from this article, you’re ready to go outside, look up into the sky and view the wondrous sights of above. And as you you’ll have a better chance of discerning planets from stars, and you’ll also know why the stars twinkle in the night sky.

So now if anyone asks you,

“Which planets are visible to the unaided eye?”

You’ve got the answer and can share it with the world!

Next Steps

When you’re ready to learn more about astronomy and using an optical instrument to view the stars, planets, and more… Be sure to check out our “Telescope 101“, it is packed with plenty of useful information.

Telescope 101

https://stargazingpro.com/telescope-guide/

Why Do Star Twinkle ?   How To Tell The Difference Between A Planet and A Star

When viewing planets and stars with an unaided eye, there is a simple trick that allows you to quickly distinguish between them.

“Objects that appear to twinkle/blink are stars, And objects that exhibit a constant level of light are planets”

This is a general rule-of-thumb, but for the most part (99.99% of the time) it holds true.  So why is it… why do stars twinkle?  First, understand that stars are located enormous distances away from our planet, and as a result, we only see them as very small points of light that twinkle because they are affected by the turbulence in the Earth’s atmosphere. The atmospheric turbulence act like lenses and prisms affect the light’s path. The official scientific term for this twinkling phenomenon is “scintillate”. In simple terms, twinkling of stars is caused by the passing of light through the different layers of Earth’s turbulent atmosphere. As an observer, you will probably notice the scintillation effects are more pronounced when viewing stars that are located closer to the horizon, this is because the light entering through the horizon is passing through a much thicker layer of the Earth’s atmosphere.

As for planets, they are located much closer to Earth and the light reflected from them are more easily resolved through the atmosphere.  With their relative close proximity, the light they reflect is comprised of many rays of lights that pierce through the atmosphere so that they can be resolved as an object with an observable diameter. With the multiple rays of light traversing the atmospheric turbulence, the deviations tend to average out to the extent that the observer has less of a perceived variation in light. In other words, the scintillation effect is so slight that the light from the object appears constant. So with an unaided eye, the planets are close enough to the Earth that they appear as a small disk in the night sky. There are exceptions, and two of the planets, Mars and Saturn, may sometimes be mis-identified as stars during their more distant orbits when they are noticeably dimmer and could suffer the effects of scintillation.

Planets vs. Stars

With the information you have acquired from this article, you’re ready to go outside, look up into the sky and view the wondrous sights of above. And as you you’ll have a better chance of discerning planets from stars, and you’ll also know why the stars twinkle in the night sky.

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