Have you ever wondered what life on Earth may be like in a different scenario? I did, and I’d like you to imagine a world where our sun is a big, blazing star called Arcturus and not anymore the familiar yellow orb we all know. In this article, we will learn about Arcturus, trying to see how this red giant star differs from the Sun. And we’ll even travel to a hypothetical Earth where Arcturus would be our “Sun”! Ready?

Arcturus: The Guardian of the Bear

The name “Arcturus” is Greek in origin and means “bear follower” or “guardian of the bear,” suggesting that Arcturus “chases” Ursa Major, commonly known as the “Great Bear,” around the sky.

There are billions of stars in the cosmos. However, Arcturus is the brightest star in the Northern Hemisphere and the fourth-brightest star in the night sky of planet Earth, being outshone only by Sirius, Canopus, and Alpha Centauri.

Only 37 light-years away from Earth, in the constellation Boötes, Arcturus is a far older star than our Sun. Its estimated age is 7.1 billion years, whereas the Sun formed 4.6 billion years ago.

QUIZ

1. What is Arcturus’ estimated age?

a) 3.5 billion years

b) 7.1 billion years

c) 10.8 billion years

d) 15.2 billion years

Arcturus: The Red Giant Star

Arcturus is reaching the end of its life cycle, being the perfect example of a red giant star – impressively large and bright, and surprisingly cool. As a red giant, Arcturus exhausted the hydrogen in its core and moved to the stage of synthesizing heavier elements such as carbon, nitrogen, and oxygen. This process produces a lot of energy, which causes Arcturus to expand and cool down.

Therefore, Arcturus has a surface temperature cooler by about 1,200 degrees Celsius than that of the Sun. Most of the red giant’s energy is radiated as heat. In fact, the star emits 215 times more heat than our Sun, which is a yellow dwarf star.

Arcturus possesses only slightly more mass than the Sun but expands that material into a radius about 25 times larger. The Sun’s diameter is only 1.39 million kilometers, whereas the red giant’s diameter is roughly 30 million kilometers. The brilliance of Arcturus is likewise almost 170 times greater than that of the Sun.

Arcturus is not just a bright and massive star, but it is also the fastest-moving star visible from Earth. It is rushing toward us at a rate of around 122 km/s (273,000 mph) in relation to the Sun.

When Arcturus will run out of helium, its outer layers will most likely disappear, leaving behind a white dwarf (which is the star’s dense core). Fortunately, Arcturus is still blazing strong today and will keep illuminating our night sky for a very long time.

QUIZ

How does Arcturus compare in size to the Sun?

a) Arcturus is smaller than the Sun

b) Arcturus is about the same size as the Sun

c) Arcturus is much larger than the Sun

How to Find Arcturus

Arcturus is easily recognizable, standing out among the other celestial bodies in the night sky with its warm, orange hue and striking brightness. Its radiance has made Arcturus a useful tool for sailors in ancient times, as they relied on it to navigate through unfamiliar waters. With Arcturus as their guide watching over them, they could traverse vast seas with greater ease and without any fear of losing direction. Even today, this remarkable star remains a go-to spot for enthusiasts of astronomy and stargazing.

Arcturus is part of a group of stars known as the “Spring Triangle,” along with Spica and Regulus, all visible in the night sky during springtime in the northern hemisphere.

If you’re still struggling to spot Arcturus, don’t worry – there’s a helpful trick. You can use the Big Dipper as a guide and look for the distinguished curve formed by its three “handle” stars: Alioth, Mizar, and Alkaid. Once this arc is spotted, follow the direction of that curve until you run into Arcturus. It is even a famous phrase: “Follow the arc to Arcturus and then speed on to Spica.”

QUIZ

Which stars are part of the Spring Triangle?

a) Sirius, Betelgeuse, and Aldebaran

b) Vega, Deneb, and Altair

c) Arcturus, Spica and Regulus

d) None of the above

Life on Earth with Arcturus

After absorbing all this information about Arcturus, it’s fascinating to ponder the implications of Earth orbiting around such a massive and luminous star. Let’s imagine together all the possibilities, except the obvious fact that Arcturus would instantly consume with its enormous heat the entire Earth!

The length of the day would be comparable to what we now experience because it is dictated by the rotation of the Earth on its axis (assuming that our planet’s orbit stays roughly the same as it is now!). But to keep its distance from Arcturus, Earth would need to move through space far more quickly than it does now while orbiting the Sun in our current solar system, and an Earth-year would be much longer than 365 days. In fact, one entire orbit of Arcturus would take the Earth hundreds of years to complete.

The Sky and The Air

If Earth were to orbit around Arcturus, our familiar sky would be transformed into a spectacle, unlike anything we’ve encountered before. Arcturus is a red giant star with an orange-red glow readily discernible to the naked eye. Furthermore, this celestial object radiates light at significantly higher levels than our own Sun does. The consequence could be incredibly bright daylight unimaginable compared to what we are used to experiencing.

Because Arcturus gives off another kind of light than our Sun, the sky might appear during the day more orange or yellow instead of blue. The star’s light could affect even the color of the clouds, giving them a more reddish-orange tint. And the constellations we are familiar with could appear completely different at night because Arcturus’ brightness might wash out some of the other stars.

Arcturus is significantly hotter than our Sun and emits a different type of radiation, both of which would have a substantial effect on the Earth’s atmosphere. Thus, it is likely that the air would be thinner and drier. Not breathable for humans without the aid of specialized equipment!

The Temperature and The Water

Let’s overlook once more the fact that life, as we know it today, wouldn’t be possible on an Earth that orbits Arcturus because this red giant although has a surface temperature of around 4,300 Kelvin, the equivalent of approximately 4,000 degrees Celsius, emits high levels of heat. This means that the Earth’s temperature would reach 800 degrees Celsius if our planet were to orbit Arcturus.

Along with drought conditions and water scarcity, the rising temperature may also affect rainfall patterns and temperature (raindrops will feel extremely hot). The increased ultraviolet (UV) light brought on by Arcturus, our new hypothetical Sun, may also enhance the toxicity of rainfall and even change the physical characteristics of the water. Stronger ocean currents could result from the increased heat input. In reality, at almost 800 degrees Celsius, Earth’s oceans will just boil.

Fauna and Flora

The presence of Arcturus in our solar system would alter how organisms evolved to survive and flourish on our Blue Earth. They would be forced to adapt to extreme UV radiation and other environmental stresses.

One possible adaptation for mammals would be to evolve thicker fur or other insulation to protect themselves against increased heat and radiation. Some animals might also develop more efficient cooling mechanisms to regulate their body temperature. Additionally, animals might adapt to become more nocturnal.

To survive on this heated Earth, plants would also likely undergo massive evolution. One possibility could be that plants develop more efficient photosynthesis mechanisms and ways to conserve water (since the increased heat and decreased rainfall could lead to more arid conditions).

Back to the REALITY!

Don’t be afraid to play around with your imagination, by taking proven facts and running them in fictive scenarios inside your head. It doesn’t hurt you, or others. You are, in fact, training your mind to think abstractly, and this is a skill that you will want to have in life, trust me! But no matter how far you travel with your imagination, always keep an eye on the reality!

And here the reality is this:

Once, Arcturus was a star similar in many ways to our Sun, but it evolved over billions of years to become the red giant that it is today. By studying Arcturus, we will be able to better understand the future of our own star, because it will come a day when the Sun will be identical to Arcturus. And when that happens, Earth will have indeed temperatures of 800 degrees Celsius, toxic rainfalls, boiling oceans, burning lands, and no life at all on it.

However, the ecosystem and the animals on Earth don’t need 2,5 billions of years to perish. Deforestation, air pollution, plastic pollution, climate change, and wildlife extinction are all issues that Earth is still dealing with TODAY!

I encourage you to create your own scenarios, stories or drawings of Arcturus, and to share them with us on our Facebook page or community.