How do Scientists Measure the Temperature of Planets?

temperature of planets
Photo Credit: Matteo Fusco

When determining what the coldest planet is, we must first ask how the temperature of planets are measured. Knowledgable people immediately answer “Uranus of course; the temperature on Uranus is minus 371 degrees Fahrenheit”. How does anyone know that? Did we shoot thermometers at the planet or something?

Actually, scientists HAVE placed thermometers on some planets, most notably Mars. But for the more distant planets like Uranus, scientists estimate the temperature by looking at the light emitted by the planet. When estimating temperature, scientists don’t look at visible light; they look at infrared light, the light that has a longer wavelength than the red light that we can see.

red hot coals
Photo Credit: Michal Matlon

Planck’s law is a formula that calculates how much light is emitted at each wavelength from an object based on its temperature. This law is firmly founded on the basics of quantum mechanics, thermodynamics, and relativity. You can obtain an intuitive understanding of what the scientists are doing by looking at the coals of a fire. The hotter coals emit a lot of white light, less-hot coals glow red, and cool coals do not emit any visible light.

What Tools Are used to Calculate the Temperature of Planets?

Scientists use a device called a bolometer to convert the infrared light the planet emits at different wavelengths into distinct electrical signals, which can be converted into an estimate of the temperature of the planet. Similar technology is currently in use in thermal imagers and cameras, which are inexpensive and widely available. These devices are used for all sorts of purposes, such as checking for insulation leaks, determining if an infant has a fever, and observing wildlife in the dark.

Photo Credit: ActionVance

It’s rather astonishing that you can buy a thermal imager at Walmart for under $100 that works on the same principles that scientists use to estimate the temperatures of objects that are billions of miles away.

How Old is The Sun?

sun and clouds
Photo Credit: Pixabay

The Sun has been providing the Earth with sunlight for several billion years. Have you ever stopped and actually asked yourself How Old is the Sun? At some point, both celestial bodies will die, but while the Earth is expected to become uninhabitable within the next billion years, the Sun has a much longer lifespan.

The Sun is estimated to be 4.6 billion years old, making it one of the oldest entities in the Solar System. Despite the star’s age seeming like a massive number, the Sun is at the middle point of its life. Here’s a quick look at the Sun’s life cycle, from its formation to its ultimate demise.

What Is the Life Cycle of the Sun?

The Sun’s lifespan can be narrowed down to three phases: its formation, current state, and death.

The Formation

Simply put, the Sun was initially part of a hydrogen and helium molecular cloud before a nearby supernova’s shockwave forced it to become a star. In reality, that shockwave caused the cloud’s molecules to compress. Along with a rotating motion, a part of the cloud built up much heat and pressure in its core, leading to the formation of a star with disks surrounding it. 

That’s how the Sun (star) and the planets (disks) of the Solar System were formed.

NASA sun photo
Photo Credit: NASA

The Main Sequence

The Sun is almost at the midpoint of its main sequence phase, during which nuclear fusion occurs, turning hydrogen into helium. As the millennia pass, the star will continue depleting its core’s hydrogen while it also grows in size and emits an increasing amount of solar radiation.

The Sun’s main sequence phase is estimated to last 9-10 billion years. Considering it’s already 4.6 billion years old, it should have enough hydrogen in its core for almost 5 more billion years.

After Hydrogen Exhaustion

Once all the core’s hydrogen is exhausted, the Sun will spend a billion years expanding until it becomes a Red Giant. At that point, about 6 billion years away, the Sun’s surface will be close to Mars, and its luminosity will be 1000 times stronger. 

The Sun will spend around a billion years as a Red Giant before depleting its core’s helium, leading to an unstable phase and the beginning of its death.

How Old is The Sun and When Will The Sun Die?

The Sun’s death begins with an explosion (planetary nebula), followed by the star becoming a White Dwarf. From then on, estimates have shown that the Sun’s White Dwarf phase will last for billions, if not trillions of years, before turning into a Black Dwarf, at which point it won’t emit any light or heat.

How old is the sun
Rendering Credit: Pixabay


Even though the Sun is 4.6 billion years old, its core contains enough hydrogen to keep the star stable for another 5-6 billion years. Once the hydrogen is depleted, the Sun will gradually get larger before becoming a Red Giant. 

A billion years after the beginning of the Red Giant phase, the Sun will unstably increase in size before exploding into a planetary nebula and becoming a White Dwarf. At that stage, the Sun will be dead. However, it will still emit light and heat for billions or trillions of years before it turns into a Black Dwarf.

If you want to get a better idea of how we know how old the Sun is and what will happen to the Solar System, feel free to go through our in-depth analysis of the Sun’s and Solar System’s lifetime.

How Do We Know How Old the Sun Is?

The Sun has been shining for several billion years, allowing the Earth to become the only planet in the Solar System that can host life. But, how do we know how old the sun is when we can’t even get to its surface? Finding the exact point in time when the Sun formed was initially impossible, but there are methods we can use to get an estimate.

As technology advanced, scientists found several ways to pinpoint the Sun’s age, even though these were indirect methods. They all offered the same results, thus giving an accurate answer on the Sun’s age. Here are the two methods used to determine how old the Sun is.

How do we know how old the sun is
Rendering Credit: Brano

The Methods Used to Find How Old the Sun Is

Luckily enough, the entire Solar System and the Sun were formed within a few million years. Thus, by figuring out how old the Solar System is, estimates showed that the Sun is between 4.5-4.6 billion years old. Radioactive dating and Solar System evolution models are used to date the Solar System’s (and subsequently the Sun’s) age.

Radioactive Dating

Simply put, radioactive dating is the process of measuring the core decay of astronomical objects, such as meteorites, as well as Moon and Earth rocks. Considering that the Solar System is as old as the Sun, the radioactive dating results would reveal the star’s age.

While the oldest Earth rocks found were 3.8 billion years old, Moon rocks from the Apollo missions were determined to be 4.5 billion years old. Additionally, when dating ancient meteorites, the results gave a definitive answer; the Sun and the Solar System are around 4.6 billion years old.

Solar Eclipse
Photo Credit: Jongsun Lee

Solar System Evolution Models

In an attempt to replicate the results found from radioactive dating, scientists created computer models that simulated the Solar System’s evolution. By utilizing some parameters from the Sun, the results regarding the star’s age were identical to those of radioactive dating.

To understand how these computer models work, examining the aforementioned parameters is necessary. As the Sun ages, it produces different luminosity levels, allowing for accurate aging when added to a simulation model. Thus, by creating the stellar evolution models and crosschecking the luminosity levels, the Sun’s age was again determined to be 4.6 billion years.

How Do We Know How Old the Sun Is? Conclusion

Photo Credit: Pixabay

Finding out the Sun’s age was, at first, challenging. However, with the help of new technological advancements and the idea that the Solar System and the Sun were of similar age, scientists utilized two methods to discover how old the Sun is: radioactive dating and stellar evolution models.

With radioactive dating, the decay found in core elements of meteorites, Earth rocks, and Moon rocks was used to estimate their age, which would be equivalent to the Sun’s age. In addition to this, computer models of the Solar System’s evolution were developed, which came to the same conclusion as radioactive aging by utilizing the Sun’s current luminosity levels.

If you want to learn more about how long the Sun will last and what will become of the Solar System, feel free to check out our thorough analysis of the Sun’s life cycle.

Why You’ll Love Inspiration4 Mission to Space!

Inspiration4 Mission
Photo Credit: Pixabay

Inspiration4 Mission to Space brings to life the challenge of sending four non-astronauts into orbit. It’s everything we love about binge-watching a TV show!

Why You’ll Love Inspiration4 Mission to Space!

We love a “thinking” space documentary, something that “lingers” in our minds for a while. Sometimes it’s good to relax and watch something that’s not so intellectually heavy. Inspriation4 is an easy-to-watch, binge-able, Sunday afternoon kind of show. 

Limited Series = Shorter Time Commitment

This limited series Netflix space documentary has five episodes. It’s more of a time commitment than our other Best Space Documentary recommendations, but it’s not a “Cosmos” level of commitment.  

This is definitely one of the best space documentaries on Netflix  The ability to get to know the crew members will keep you intrigued.

Grab some popcorn and get ready to see how four ordinary people train for space travel. To be transparent, one of the four is a self-made billionaire. The other three crew members are regular folks!

Get To Know The Inspiration4 Crew

Four crew members represent the mission pillars of Leadership, Hope, Generosity, and Prosperity. In episodes 1 & 2, we meet the crew.

  • Leadership: Jared Isaacman, Commander & Benefactor. Isaacman may excite a new generation of potential space explorers.
  • Hope: Hayley Arceneaux is a childhood cancer survivor. Her journey with St. Judes inspired her to return as a PA with leukemia and lymphoma patients. Spoiler alert: tears may fill your eyes upon meeting her.
  • Generosity: Chris Sembroski represents a generous spirit after winning his spot on Inspiration4. St Judes held a Super Bowl fundraising campaign. All donors received an entry to become crewmembers! Sembroski donated $500 and won the trip of a lifetime. He may have forgotten to tell his wife that he entered a trip to go to space…
  • Prosperity: Dr. Sian Proctor represents an entrepreneurial spirit and a lifelong passion for space exploration. Dr. Proctor missed the cut-off to be actual NASA astronaut years ago. Today she’s getting her shot. Her unbridled excitement for this journey will fill you with joy.

Inspiration4 raised over $240 million for St. Judes Children’s Research Hospital.

Photo Credit: Pixabay

Amazing Views Of Space

This all-civilian crew orbited around the earth, and the show revealed stunning views.

The final episode of this space documentary takes us on the ride of a lifetime! The Inspiration4 crew lifts off from Kennedy Space Center. Awe takes over when the reality of being in orbit, and the window view, set in for the crewmembers.

Footage of earth mesmerizes crew and viewers alike. Finally, it’s space exploration from your couch!

Inspriration4: Worth the Watch

Why should Inspiration4 have its place in your viewing Netflix queue? Most space documentaries focus on theoretical science, the “what’s possible.” Inspiration4 is all about applied science. Seeing and experiencing equates to believing.

You’ll experience how it feels for ordinary civilians to travel into space. 

There’s an unending universe out there. Inspiration4 will leave you ready to pack your bags and do a little space travel yourself.

After you’ve watched and fallen in love with Inspiration4 click here to view our full list of space documentary recommendations!

The Farthest: Voyager in Space

the farthest: voyager in space
Photo Credit: Andy Holmes

The Voyager space missions are humanity’s most remarkable achievement. The Voyager missions will still be active long after we’re all gone. 

The Farthest: Voyager in Space is about the fundamental questions of science. What is the universe made of? Where did life begin? Are we alone in the universe?

This is one of the best space documentaries ever made, and it’s streaming on Netflix.

Voyager Objectives

The primary mission goal is to collect data from Saturn and Jupiter. Primary mission success means the spacecraft continues to Uranus, Neptune, and interplanetary space. 

Golden Records

The Golden record’s goal is to capture the diversity of life and culture on Earth. Instructions on how to play the record are on the record jacket. The concept is that this record is planet earth saying, “Hello!” Each record contains images, music, sounds, and greetings from various cultures across Earth.

Engineers share their frustration with the Golden Records. The records may be humankind’s introduction to another species. What’s included on the record? How do you select 100 images to represent humanity? What music represents all cultures? Should we include a roadmap to Earth?

voyager in space
Photo Credit Georgia Vagim

Planetary gravitational slingshot 

Once every 176 years, the outer planets in our solar system “line up in a row” for a short period. NASA scientists race to take advantage of this opportunity.

Harnessing planetary gravitational forces allows the spacecraft to adjust its trajectory without fuel. The gravitational forces of Jupiter slingshot the Voyager spacecraft towards Saturn. Then from Saturn to Uranus, and Uranus to Neptune.  

If the Voyager can catch the alignment window, it will travel from Saturn to Neptune in twelve years. Missing the alignment window equates to a thirty-year trip.  

Unexpected discoveries

What’s NASA life like when Voyager approaches a planet?  Data begins to pour in from the spacecraft. Images to analyze, data to interpret, and press conferences galore. 

The film rewards the viewer with ah-ha! moments during planetary flybys. Raw, unprocessed images allow us to see the planets bouncing around the camera’s field of view. Distorted, distended, defocused images transition into crisp, high-resolution images. The images are breathtaking.

We’re in the room when discoveries occur. The planetary images are enough to rewrite science textbooks.

Photo Credit: Jeremy Thomas

Are we alone in the universe?

When the Voyagers have depleted their power supplies, the Golden Records become the primary mission. The Farthest: Voyager in Space discusses the possibility of extraterrestrial life. We appreciate the intelligent conversation.  

Early in the film, there’s a discussion between NASA and the U.S. President about mission funding. NASA shares why the Voyager mission is essential. The stated goal is Jupiter and Saturn data collection.  

NASA doesn’t mention its own secondary, somewhat secret, goal. A hope that the Voyagers would travel for a much greater distance than “only” Saturn and Jupiter. 

Wrap up

The Farthest: Voyager in Space begins to address the fundamental questions of science. We suspect the real answers from the Voyager missions may be tens of thousands of years away. 

This is one of the top ten space documentaries that we recommend. Click here to check out the rest!

A Quick Guide to Dwarf Planets

When most people talk about the solar system, they’re thinking of the big guys—large planets like Jupiter and Neptune

However, there are also smaller planets, called dwarf planets in the solar system. 

dwarf planets
Photo Credit: Guillermo Ferla

These dwarf planets are much farther away, and have some slightly different characteristics. Let’s go over what they are and why they can’t be considered true planets!

What Are Dwarf Planets?

This concept was integrated into the world of astrology in August 2006, when the International Astronomical Union decided that Pluto was no longer a planet and changed its title. While it was no longer the farthest planet from the sun, it was still part of the solar system as a dwarf planet.

According to the IAU, dwarf planets have to meet both the basic requirements to be a planet:

  1. They must orbit a star
  2. They must have enough mass to have a spherical (or nearly spherical) shape through hydrostatic equilibrium. 

However, those aren’t the only requirements they have to meet. In addition to those requirements, they also have to meet the following criteria:

  • Can’t be a satellite of a planet or another stellar body
  • Must share the vicinity of the orbit with other objects

As long as a planet meets those four criteria, you’ve got a dwarf planet on your hands. 

Currently Known Dwarf Planets

The whole dwarf planet thing started one year before Pluto got kicked out of the solar system (not literally, just technically speaking). 

This is when a celestial body called Eris was found. 

Scientists began to debate whether Eris should be added as the tenth planet in the solar system, or whether it deserved its own classification. 

As you can tell, they decided on the latter. However, that also meant that they had to re-examine Pluto’s classification, naming it as a dwarf planet too. 

Once this classification was established, it paved the way for scientists to identify and classify other dwarf planets. Today, there are five known dwarf planets: 

  1. Ceres
  2. Pluto
  3. Haumea
  4. Makemake
  5. Eris

Let’s take a closer look at each of them. 


Ceres is the dwarf planet closest to the sun. It’s a trans-Neptunian object, with a distance of 413,690,250 km from the sun, and was the first visited by NASA’s Dawn space probe. Before being a dwarf planet, until 2006, it was classified as an asteroid.


Pluto is a frozen dwarf planet, whose average temperature sits at -240 ºC. This dwarf planet can, at times, can be closer to the sun than Neptune due to its orbit. 

Photo Credit: NASA


Haumea is similar in size to Pluto and is the fourth in the solar system when it comes to dwarf planets. It was discovered in 2003, but it didn’t get classified as a dwarf planet until after Pluto. 

This planet is shaped like a rugby ball, and half a decade ago, it was discovered that it was the first known Kuiper belt object to have rings. In case you’re not clear on where Kuiper is, that’s the same belt that Pluto is located in!


Makemake is a plutoid object smaller than Pluto. However, it’s the second brightest plutoid in the Kuiper belt, as seen from Earth. 


Eris is the fifth and last dwarf planet. That means that it’s the furthest from the sun. It’s also the largest known dwarf planet to date.

dwarf planets
Photo Credit: Alexander Andrews

Dwarf Planets, a Recent Concept

Astronomers who study space constantly decid to adopt a new terms. That’s how they managed to regroup celestial bodies such as Pluto!

Despite their smaller stature, dwarf planets are still important parts of our solar system. They also are just one more step on the road to many more discoveries about outer space.