![WORLDS WITHOUT SUNS](https://magarticles.magzter.com/articles/15256/676743/60d9b158b1f5b/WORLDS-WITHOUT-SUNS.jpg)
When we think about planets, a star usually comes as part of the package. After all, where would Earth be without the Sun? Imagine Luke Skywalker’s home planet of Tatooine without its twin suns, or Superman without Rao, the red supergiant around which Krypton spun. Yet you’d be wrong to imagine that planets are never starless. Astronomers have already found swarms of rogue planets – worlds wandering the open chasm of space alone.
As far as we know, planets always start off with stars. They are the leftover fragments from star formation, the offcuts that you’d throw away in a skip if you were building a house. A cloud of gas and dust that was otherwise minding its own business may begin to contract if it’s hit by a shock wave from an exploding star. As the cloud compresses, gravity takes over and bundles it into an ever-smaller space until fledgling stars ignite inside.
The shrinking cloud begins to spin faster and faster, flinging leftover gas and dust into discs around new stars. Gravity continues its work here, too. Dust grains merge into lumps the size of golf balls, which continue to snowball until they reach a kilometre or so across.
Astronomers call these planetary building blocks planetesimals. Close to the star they are made of metals – the only materials with high enough melting points to stay solid in the face of the inferno. Further out – beyond an imaginary boundary called the ice line – temperatures plummet below freezing and the planetesimals take the form of frigid lumps of water, ammonia and methane ices. That’s why we have rocky planets close to the Sun and ice giants the furthest out.
هذه القصة مأخوذة من طبعة Issue 118 من All About Space.
ابدأ النسخة التجريبية المجانية من Magzter GOLD لمدة 7 أيام للوصول إلى آلاف القصص المتميزة المنسقة وأكثر من 9,000 مجلة وصحيفة.
بالفعل مشترك ? تسجيل الدخول
هذه القصة مأخوذة من طبعة Issue 118 من All About Space.
ابدأ النسخة التجريبية المجانية من Magzter GOLD لمدة 7 أيام للوصول إلى آلاف القصص المتميزة المنسقة وأكثر من 9,000 مجلة وصحيفة.
بالفعل مشترك? تسجيل الدخول
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LONG AGO, A LAKE ON MARS MAY HAVE BEEN SPRAWLING WITH MICROBES
Curiosity discovered manganese oxide in bedrock in a Martian region that may have been a shoreline billions of years ago
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MOON TOUR HELL
Finding this fascinating crater isnt as hard as its name suggests...
![THIS MONTH'S PLANETS](https://reseuro.magzter.com/100x125/articles/15256/1729654/-7K-H52mO1719993250345/THIS-MONTHS-PLANETS.jpg)
THIS MONTH'S PLANETS
Most of the planets are tricky targets this month, but our guide will help you locate them
![UNIVERSE BEFORE TIME](https://reseuro.magzter.com/100x125/articles/15256/1729654/cHFLjjJOS1719991851680/UNIVERSE-BEFORE-TIME.jpg)
UNIVERSE BEFORE TIME
Could the existence of a mirror-image cosmos before the Big Bang solve some of the biggest mysteries in astronomy?
![CLIMATE CHANGE IN THE SOLAR SYSTEM](https://reseuro.magzter.com/100x125/articles/15256/1729654/Se3Bbyf0G1719991384386/CLIMATE-CHANGE-IN-THE-SOLAR-SYSTEM.jpg)
CLIMATE CHANGE IN THE SOLAR SYSTEM
Alongside Earth, our planetary neighbourhood is changing, but it’s not for the better…
![Stars give tiny planets a gravitational 'squeeze' to strip away their atmospheres](https://reseuro.magzter.com/100x125/articles/15256/1729654/QMnZ5oBmH1719991224194/STARS-GIVE-TINY-PLANETS-A-GRAVITATIONAL-SQUEEZE-TO-STRIP-AWAY-THEIR-ATMOSPHERES.jpg)
Stars give tiny planets a gravitational 'squeeze' to strip away their atmospheres
A scientist has learned more about the violent processes that rip atmospheres away from planets, finding that squashing and squeezing by a parent star can contribute to this process.
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The Milky Way's halo is filled with ‘magnetic doughnuts' as wide as 100,000 light years
The outer halo of the Milky Way is filled with magnetic fields that take the shape of vast doughnuts with diameters ranging from 12,000 to 100,000 light years, with the heart of our galaxy at their centre.
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The Pentagon wants the commercial space reserve to support military satellites in orbit
The US Department of Defense is developing a plan to use the ever-growing American commercial space industry for national security purposes.
![DOES A COSMIC 'GLITCH' IN GRAVITY CHALLENGE ALBERT EINSTEIN'S GREATEST THEORY?](https://reseuro.magzter.com/100x125/articles/15256/1729654/qd-Mswgsf1719990737533/DOES-A-COSMIC-GLITCH-IN-GRAVITY-CHALLENGE-ALBERT-EINSTEINS-GREATEST-THEORY.jpg)
DOES A COSMIC 'GLITCH' IN GRAVITY CHALLENGE ALBERT EINSTEIN'S GREATEST THEORY?
Gravity changes once you reach a cosmic scale
![DEEP SKY CHALLENGE : STELLAR TREASURES OF THE ARCHER AND SCORPION](https://reseuro.magzter.com/100x125/articles/15256/1729654/kQkKImKfQ1719990358327/DEEP-SKY-CHALLENGE-STELLAR-TREASURES-OF-THE-ARCHER-AND-SCORPION.jpg)
DEEP SKY CHALLENGE : STELLAR TREASURES OF THE ARCHER AND SCORPION
Summer skies are stuffed full of amazing objects for your telescope - if you're prepared to stay up late