How big is the solar system?

How Big Is the Solar System?

This artist's concept depicts NASA's Voyager 1 spacecraft entering interstellar space, or the space between stars. Interstellar space is dominated by the plasma, or ionized gas, that was ejected by the death of nearby giant stars millions of years ago. The environment inside our solar bubble is dominated by the plasma exhausted by our sun, known as the solar wind. The interstellar plasma is shown with an orange glow similar to the color seen in visible-light images from NASA's Hubble Space Telescope that show stars in the Orion nebula traveling through interstellar space. Image released Sept. 12, 2013.

(Image: © NASA/JPL-Caltech)

Voyager 1 has left the solar system. The big news that the spacecraft reached interstellar space on Aug. 25, 2012, after its decades-long sojourn begs the question: Just how far did it have to travel to knock on cold, dark space's door?

In other words, just how big is the solar system that earthlings call home?

  • That's a question whose answer is steeped in hot gas traveling faster than the speed of sound.
  • “There's a gas flowing outward from the sun called the solar wind, at about a million miles an hour, it's supersonic,” said study researcher and Voyager 1 team member Donald Gurnett, of the University of Iowa, who is principal investigator of the plasma wave instrument. [How the Voyager Space Probes Work (Infographic)]
  • As the charged gas zips away from the sun, it expands and spreads out; at the same time, its density decreases.
  • “Fifty years ago or thereabouts, it was recognized or postulated that the solar wind has to be stopped by the interstellar gas pressure, the gas between the stars,” Gurnett told LiveScience in an interview.

Scientists knew this cold, dark space between stars existed, calling the boundary between it and the bubble of hot, charged particles surrounding our solar system the heliopause. Even so, they didn't know how dense this boundary might be.

The boundary would mark the end of the solar system and the beginning of interstellar space, hence revealing the size of the solar system.

“There's been a great quest for a long time to figure out where this boundary was,” Gurnett said. “It was once thought — at least two scientific papers 30 or so years ago claimed it was just beyond Jupiter.”

Now that Voyager 1, which launched in 1977, has penetrated the heliopause and entered the stars' chilly quarters, Gurnett and his colleagues can say the boundary is much farther out than Jupiter's orbit.

The end of the solar system is about 122 astronomical units (AU) away from the sun, where one AU is 93 million miles (150 million kilometers). That's about three times as far out as Pluto, which is about 40 AU from the sun, or about six times farther away from Earth than Neptune's orbit.

That means Voyager 1 is about 1 light-day away from planet Earth. For comparison, the nearest star Alpha Centauri lies 4.3 light-years away. A radio signal, which travels at the speed of light (186,000 miles a second, or nearly 300,000 km/s), takes 17 hours to travel from Voyager 1 to Earth.

“Voyager is the highest-speed object ever produced by a human,” Gurnett said.

The scientists involved in the mission knew the spacecraft had pushed through the heliopause on April 9, 2013, when they saw a Voyager 1 recording of a sudden spike in oscillations of plasma (hot, ionized gas) at a certain frequency.

“When we saw that, it took us 10 seconds to say we had gone through the helio-pause,” Gurnett said in a statement.

The frequency suggested a plasma density that was 80 times higher than anything seen inside the heliosphere's outer edge.

In fact, the density was close to what astronomers would expect in interstellar space. They then back-calculated when Voyager 1 would have passed the heliopause.

Voyager 1 is beyond the solar bubble but has yet to reach the Oort Cloud, a repository of comets a light-year or so away from which many of the icy bodies travel to the inner solar system. The Oort Cloud forms a sort of icy shell around the solar system.

How Big is the Sun? | Size of the Sun

The sun is the largest and the most massive object in the solar system, but it is just a medium-sized star among the hundreds of billions of stars in the Milky Way galaxy.

How Big Is the Solar System?This image from the Solar Dynamics Observatory (SDO) shows the sun at 12:45 PM EDT on July 12, 2012 during an X1.4 class flare. The image is captured in the 304 Angstrom wavelength, which is typically colorized in red and shows temperatures in the 50,000 Kelvin range. (Image credit: NASA/SDO/AIA)

Radius, diameter & circumference

The sunis nearly a perfect sphere. Its equatorial diameter and its polar diameter differ by only 6.2 miles (10 km). The mean radius of the sun is 432,450 miles (696,000 kilometers), which makes its diameter about 864,938 miles (1.392 million km). You could line up 109 Earths across the face of the sun. The sun's circumference is about 2,713,406 miles (4,366,813 km).

It may be the biggest thing in this neighborhood, but the sun is just average compared to other stars. Betelgeuse, a red giant, is about 700 times bigger than the sun and about 14,000 times brighter.

“We have found stars that are 100 times bigger in diameter than our sun. Truly those stars are enormous,” NASA says on its SpacePlace website. “We have also seen stars that are just a tenth the size of our sun.”

According to NASA's solar scientist C. Alex Young, if the sun were hollow, it would take about one million Earths to fill it.

It's possible that the sun is even larger than previously thought.

Xavier Jubier, an engineer and solar eclipse researcher, creates detailed models of solar and lunar eclipses to determine precisely where the moon's shadow would fall during the solar eclipse.

But when he matched actual photos and historical observations with the models, he found precise eclipse shapes only made sense if he scaled up the sun's radius by a few hundred kilometers.

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Size of solar system – ratios of the planet sizes

Powers of Ten and Size of the Solar System

If Jupiter is a styrofoam ball that is about 6 inches in diameter, then how big is Earth?  How big would the Sun be?

Scale – Ratios – The size of the Solar System It is difficult for us humans to grasp the sheer size of the solar system, and the universe. This lab activity will focus in on this idea.

In this activity you will be given a set of Styrofoam spheres and other objects and asked to calculate and then demonstrate relative sizes and distances.

On the next page is the information about the planets needed for this activity.

Part One – Mass You are going to calculate the ratios of their masses. Assume you have 100 objects, such as candy canes or chocolate bars, and the mass of the Sun is 100 objects. You are going to calculate the masses of the planets in units of candy. You will get to eat the candy afterwards.

Part Two – Size You are going to put them in the correct order “to scale” with the eight planets and dwarf planets listed here. Once you have done that, you will calculate the size of the sphere that you would need to represent the Sun.

Part Three – Distance – Styrofoam spheres “your solar system” After you have the planets in order, you are then going to calculate the distance – to scale – between the planets and place your spheres at the correct distance from the Sun. You will place the spheres from Part One along a measuring tape.

Part Four – Distance – Earth and Moon You will be given a picture of the Earth and our Moon to the correct scale. Please cut them out and using the size of the picture of the Earth and the known distance between them, you will calculate the distance the pictures should be placed to demonstrate the scale of the distance.


Examples – You will be calculating ratios. Mass: And for the mass, the Sun has a mass of 1.991 x 1030 kilograms so if we wanted the Sun to have a mass of 36 students (the total mass of the class) then the mass of Earth would be 0.00011 studnets

Diameter: For example, let us say the largest sphere was 21 cm in diameter. Jupiter is actually 142,000 km in diameter and Saturn is 120,000 km in diameter. So Saturn diameter is 18 cm.

Distances: And for the distances, Eris is 52 AU from the Sun and Saturn is 9.5 AU, so if we wanted Eris to be 4.0 metres or 400 centimetres from the Sun, then Saturn distance would be 74 cm.

Data that you will need to do this activity.

How Big Is the Solar System?

How Big is the Solar System?

For most of us, stuck here on Earth, we see very little of the rest of the Solar System. Just the bright Sun during the day, the Moon and the planets at night. But in fact, we’re embedded in a huge Solar System that extends across a vast amount of space.

Which begs the question, just how big is the Solar System?

Before we can give a sense of scale, let’s consider the units of measurement.

Distances in space are so vast, regular meters and kilometers don’t cut it. Astronomers use a much larger measurement, called the astronomical unit. This is the average distance from the Earth to the Sun, or approximately 150 million kilometers.

Mercury is only 0.39 astronomical units from the Sun, while Jupiter orbits at a distance of 5.5 astronomical units. And Pluto is way out there at 39.2 astronomical units.

That’s the equivalent of 5.9 billion kilometers.

If you could drive your car at highway speeds, from the Sun all the way out to Pluto, it would take you more than 6,000 years to complete the trip.

But here’s the really amazing part. Our Solar System extends much, much farther than where the planets are.

The furthest dwarf planet, Eris, orbits within just a fraction of the larger Solar System.

The Kuiper Belt, where we find a Pluto, Eris, Makemake and Haumea, extends from 30 astronomical units all the way out to 50 AU, or 7.5 billion kilometers.

And we’re just getting started.

How Big is the Solar System?

  • Copyright 1989 by Guy Ottewell
    Universal Workshop PO Box 102
    Raynham, MA 02767-0102
    Toll Free: 800-533-5083
    Fax: 508-967-2702
  • Email: [email protected]

This is a classic exercise for visualizing just how BIG our Solar System really is.

Both the relative size and spacing of the planets are demonstrated in this outdoor exercise, using a mere peppercorn to represent the size of the Earth. Guy Ottewell has kindly given permission for this electronic presentation of The Thousand-Yard Model; his exercise is presented in its original form, indexed with a few anchors to help you find you way around the large file.

We also include a catalog describing several Ottewell publications. Image of the planets courtesy of NASA.


Can you picture the dimensions of the solar system?

Probably not, for they are of an order so amazing that it is difficult either to realize or to show them.

You may have seen a diagram of the Sun and planets, in a book. Or you may have seen a revolving model of the kind called an orrery (because the first was built for an Earl of Orrery in 1715).

But even the largest of such models–such as those that cover the ceilings of the Hayden Planetarium in New York and the Morehead Planetarium at Chapel Hill-are far too small.

They omit the three outermost planets, yet still cannot show the remaining ones far enough apart.

The fact is that the planets are mighty small and the distances
between them are almost ridiculously large. To make any representation
whose scale is true for the planets sizes and distances, we must go

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The following exercise could be called a Model, a Walk or a Happening. I have done it more than twenty times with groups of varied ages (once
we were televised) or with a single friend; and others, such as elementary-school teachers, have carried it out with these instructions.
Since it is simple, it may seem suitable for children only.

It can,
indeed, be done with children down to the age of seven. Yet it can also
be done with a class consisting of professors of astronomy. It will not
waste their time. They will discover that what they thought they knew,
they now apprehend.

To take another extreme, the most uncontrollable
high-school students or the most blase college students unfailingly switch
on their full attention after the first few paces of the excursion.

There is one other party that may profitably take the planet-walk, and
that is yourself, alone. Reading the following description is no
substitute: you must go out and take the steps and look at the distances,
if the awe is to set in.

First, collect the objects you need. They are:

Sun-any ball, diameter 8.00 inches
Mercury-a pinhead, diameter 0.03 inch
Venus-a peppercorn, diameter 0.08 inch
Earth-a second peppercorn
Mars-a second pinhead
Jupiter-a chestnut or a pecan, diameter 0.90 inch
Saturn-a hazelnut or an acorn, diameter 0.70 inch
Uranus-a peanut or coffeebean, diameter 0.30 inch
Neptune-a second peanut or coffeebean
Pluto- a third pinhead (or smaller, since Pluto is the smallest planet)

You may suspect it is easier to search out pebbles of the right sizes. But the advantage of distinct objects such as peanuts is that their rough sizes are remembered along with them. It does not matter if the peanut is not exactly .3 inch long; nor that it is not spherical.

A standard bowling ball happens to be just 8 inches wide, and makes a nice
massive Sun, so I couldn't resist putting it in the picture. But it may not
be easy to find and certainly isn't easy to carry around. There are plenty of
inflatable balls which are near enough in size.

How Big Is the Solar System? – NASA Solar System Exploration

Our solar system is huge. There is a lot of empty space out there between the planets.

Voyager 1, the most distant human-made object, has been in space for more than 40 years and it still has not escaped the influence of our Sun. As of Feb. 1, 2020, Voyager 1 is about 13.

8 billion miles (22.2 billion kilometers) from the Sun — nearly four times the average distance from the Sun to icy Pluto.

In an effort to bring these vast distances down to Earth, we've shrunk the solar system to the size of an American football field. If the Sun were the size of a dime on the goal line, Neptune would be 60 yards away.

Needless to say, our solar system doesn't fit real well on paper — or a Web site for that matter.

Scientists figured out a while ago that writing out those huge numbers wasn't the best use of their time, so they invented the Astronomical Unit (AU).

One AU, about 93 million miles (150 million kilometers), represents the average distance from the Sun to the Earth. It would take an airliner more than 20 years to fly that distance — and that's just a one-way ticket.

(That's traveling at about 400 mph or 644 kilometers per hour.)

In an effort to bring these vast distances down to Earth, we've shrunk the solar system down to the size of a football field.

On this scale, the Sun, by far the largest thing in our solar system, is only a ball about two-thirds of an inch (17 millimeters) in diameter sitting on the goal line — that's about the width of a U.S. dime coin.

Considering a typical honeybee is about half an inch long, the fans are going to need telescopes to see the action.

The inner planets — Mercury, Venus, Earth and Mars — are about the size of grains of sand on a football field scale. They would be dwarfed by a typical flea, which is about 3 millimeters long.

Closest to the goal line is Mercury, just under a yard from the end zone (.8 yards to be specific). In reality, the average distance from the Sun to Mercury is roughly 35 million miles (58 million kilometers) or 0.4 AU. At this scale, Mercury's diameter would be scarcely as large as the point of a needle.

Venus is next. It is 1.4 yards from the end zone. The true average distance from the Sun to Venus is about 67 million miles (108 million kilometers) or 0.7 AU. Its size on this scale is about 0.15 millimeters.

On to Earth, sitting pretty on the 2-yard line. It is slightly larger than Venus at about 0.16 millimeters.

At this scale, Earth and the inner planets are within the first three yards of the goal line.

Just as most quarterbacks would be extremely pleased to find their team within two yards of a touchdown, Earth reaps many benefits from this prime location in the solar system. We are at the perfect distance from the Sun for life to flourish. Venus is too hot. Mars is too cold. Scientists sometimes call our region of space the “Goldilocks Zone” because it appears to be just right for life.

As noted earlier, Earth's average distance to the Sun is about 93 million miles (150 million kilometers) from the Sun. That's 1 AU.

Mars is on the three-yard line of our imaginary football field. The red planet is about 142 million miles (228 million kilometers) on average from the Sun. That's 1.5 AU. On this scale, Mars is about 0.08 millimeters.

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How Big Is the Solar System?

What do you think about when you stare out into the night sky? Do you WONDER how far away those shiny objects really are? Or do you instead imagine what types of alien life might be out there staring back at you?

If you've spent much time here on Earth, you know it's a pretty amazing place. Compared to a single individual, Earth is humongous. It would take most, if not all, of a lifetime to see even a fraction of its treasures.

That's probably why it blows your mind when you realize how unbelievably tiny Earth is compared to the rest of the solar system and the larger universe. In fact, it can be nearly impossible to comprehend truly the size of the universe.

Even if you concentrate on just Earth's neighborhood — our solar system — its size can boggle the mind. Scientists had to come up with a new unit of measurement just to get a grasp on the immense distances within the solar system. The astronomical unit (AU) is based upon the average distance from Earth to the Sun, or approximately 93 million miles.

For example, Mercury, the closest planet to the Sun, is 0.39 astronomical units from the Sun. But what about the planet farthest out there? Today, scientists consider Neptune to be the farthest official planet, but dwarf planet Pluto is still out there in our solar system. Pluto sits 39.2 astronomical units from the Sun, or about 3.67 billion miles.

So is that the size of our solar system? Around 3.67 billion miles? Nope! Our solar system extends well beyond Pluto. Pluto sits within the Kuiper Belt with other dwarf planets that extend from 30 AU out to 50 AU.

But even the Kuiper Belt isn't at the end of the solar system.

Astronomers know that the Sun's solar wind travels farther out into space where it eventually meets the interstellar medium, which is the cold, dark background material of the galaxy that exists between stars. This point is known as the heliopause or the termination shock, and astronomers believe it's approximately 122 AU away from the Sun.

While some astronomers are content to claim that the size of the solar system is around 122 AU, others point out that the solar system should really be defined by the reach of its gravity. In other words, if an object can be said to orbit the Sun, then it should be considered part of the solar system.

Using this expanded definition, astronomers point to the theoretical Oort Cloud as the approximate boundary of the solar system. A cloud of icy objects that could be the source of comets that enter the inner solar system from time to time, the Oort Cloud sits more than 100,000 AU away from the Sun.

Using the Oort Cloud as an approximate boundary would mean that the size of our solar system approaches nearly 2 light years! That's equivalent to almost 12 trillion miles. Try to wrap your mind around that. And once you have wrapped your mind around that, remember that's just the size of our tiny solar system, which is just a speck in terms of the whole universe!

How Many Solar Panels Do You Need: Panel Size and Output Factors

Determining how many solar panels you’ll need for your home means first knowing what your goals are. Do you want to minimize your carbon footprint?  Maximize your return on your investment? Save as much money as possible?  Most people want to save money while minimizing their environmental impact.

To calculate how many solar panels you need, you need to know the following: how much energy your household uses; your roof’s usable surface area; the climate and peak sunlight in your area; the wattage and relative efficiency of the photovoltaic (PV) panels you’re considering; and whether net metering is available.

One simple way of answering the “How many solar panels do I need” question is to consult a professional solar installer, who can give you a free home solar evaluation.

1. How much solar power will you need?

To determine your home’s average energy requirements look at past utility bills.

You can calculate how many solar panels you need by multiplying your household’s hourly energy requirement by the peak sunlight hours for your area and dividing that by a panel’s wattage.

Use a low-wattage (150W) and high-wattage (370W) example to establish a range (ex: 17-42 panels to generate 11,000 kWh/year). Note that how much sunlight your roof gets and factors such as roof size and battery storage will figure in as well.

If you work with SunPower, our solar experts will handle all these calculations for you. But to give you some idea of how many solar panels are needed for the average home (or for your home in particular), here is a sample set of questions that a solar professional might use to figure it out:

2. How many watts do you currently use?

Look at your electricity bill for average usage. Look for “Kilowatt Hours (or kWh) Used” or something similar, and then note the time period represented (usually 30 days). If your bill doesn’t show kilowatt hours used, look for beginning and ending meter readings and subtract the previous reading from the most recent one.

You want daily and hourly usage for our calculations, though, so if your bill doesn’t show a daily average, just divide the monthly or annual average by 30 or 365 days, respectively, and then divide again by 24 to determine your hourly average electricity usage. Your answer will be in kilowatt-hours (kWh). (And just in case you are wondering, a kilowatt-hour is how much power you are using at any given time multiplied by the total time the power is being used.)

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