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Stargazing at home Week 5: Hop from star to star
The back pages Puzzles Quick crossword, a matchstick puzzle and a quiz p52
Feedback Strange maths and tangerine dreams: the week in weird p53
Twisteddoodles for New Scientist A cartoonist’s take on the world p53
Almost the last word Shopping green and fluorescent blue ink: readers respond p54
The Q&A Anu Ojha reveals the solar system’s coolest moons p56
Stargazing at home Week 5
Hop from star to star The Orion constellation is one of the easiest to spot, and you can use it to work your way across the sky, says Abigail Beall
What you need You don't need anything
For next week Binoculars
Next in the series 1 Model the equinox 2 Find the North Star and Southern Cross 3 Test your area’s light pollution 4 Identify the craters of the moon 5 Orion and Sirius: how to star-hop 6 Planet spotting: Mars, Mercury and Uranus When is a star not a star? 7 Taurus and the zodiacal constellations
BETELGEUSE SIRIUS ORION'S BELT RIGEL
ARMAN GOLESTANEH
Abigail Beall is a science writer in Leeds, UK. This series is based on her book The Art of Urban Astronomy @abbybeall
THIS week, we are going to be star-hopping. We will identify the most recognisable constellation visible around now – Orion – and use it to find Sirius, the brightest star in the night sky. You don’t need any equipment, and as Orion is one of the brightest constellations, light pollution shouldn’t be a problem either. Sirius can be seen in summer in the southern hemisphere, rising early in the morning before the sun, and in the evening when it sets after the sun. At the moment in the northern hemisphere, Sirius will rise above the horizon at about midnight, and it will appear earlier through winter. Orion the Hunter is a great constellation to start with because it contains many bright stars. It is also found on the celestial equator, which means it can be seen from anywhere in the world. It appears in September, and is visible for most of the night between January and March. The best way to find Orion is to look for the iconic line of three stars that make the asterism of Orion’s Belt. Their names are Alnitak, Alnilam and Mintaka. The brightest star in Orion and the sixth-brightest in the night sky is Rigel, at the bottom right. Rigel is actually a system of three stars, the blue supergiant Rigel A with two fainter companions. Betelgeuse, at the top left, is Orion’s shoulder. Although it is between 11 and 15 times as massive as the sun, its radius is 950 times wider. This makes it one of the biggest stars we know of. It is a red
Stargazing at home online
Projects will be posted online each week at newscientist.com/maker Email: [email protected]
supergiant, so has used up its core of hydrogen and is now burning the helium around its outside. It is some 8 or 10 million years old, which is quite old for a supergiant. Such stars burn their fuel quickly and brightly. This means Betelgeuse might explode in a supernova any day now. However, before you get excited, “any day now” in astronomical terms means any time in the next million years. Now for the star-hop. Going from the right side of Orion’s Belt to the left, carry that line a little further than the distance between Betelgeuse and Rigel. At the end is Sirius, the dog star, in the constellation Canis Major.
Most stars we can see with the naked eye are binary systems, and Sirius is no exception. Sirius A and B orbit each other at a distance of between 8.2 and 31.5 astronomical units (1 AU is the distance between Earth and the sun). Sirius A is about twice as big and 25 times as bright as our sun, but Sirius B used up its hydrogen a long time ago, became a red giant and is now a white dwarf. In absolute terms, that makes Sirius quite a dim star. The only reason it appears bright is that it is just 8.6 light years away. Next week, we will be finding out how to tell the difference between a star and a planet, and spotting all those it is possible to see. ❚ 19 October 2019 | New Scientist | 51
Feedback Strange maths and tangerine dreams: the week in weird p53
Twisteddoodles for New Scientist A cartoonist’s take on the world p53
Almost the last word Shopping green and fluorescent blue ink: readers respond p54
The Q&A Anu Ojha reveals the solar system’s coolest moons p56
Stargazing at home Week 5
Hop from star to star The Orion constellation is one of the easiest to spot, and you can use it to work your way across the sky, says Abigail Beall
What you need You don't need anything
For next week Binoculars
Next in the series 1 Model the equinox 2 Find the North Star and Southern Cross 3 Test your area’s light pollution 4 Identify the craters of the moon 5 Orion and Sirius: how to star-hop 6 Planet spotting: Mars, Mercury and Uranus When is a star not a star? 7 Taurus and the zodiacal constellations
BETELGEUSE SIRIUS ORION'S BELT RIGEL
ARMAN GOLESTANEH
Abigail Beall is a science writer in Leeds, UK. This series is based on her book The Art of Urban Astronomy @abbybeall
THIS week, we are going to be star-hopping. We will identify the most recognisable constellation visible around now – Orion – and use it to find Sirius, the brightest star in the night sky. You don’t need any equipment, and as Orion is one of the brightest constellations, light pollution shouldn’t be a problem either. Sirius can be seen in summer in the southern hemisphere, rising early in the morning before the sun, and in the evening when it sets after the sun. At the moment in the northern hemisphere, Sirius will rise above the horizon at about midnight, and it will appear earlier through winter. Orion the Hunter is a great constellation to start with because it contains many bright stars. It is also found on the celestial equator, which means it can be seen from anywhere in the world. It appears in September, and is visible for most of the night between January and March. The best way to find Orion is to look for the iconic line of three stars that make the asterism of Orion’s Belt. Their names are Alnitak, Alnilam and Mintaka. The brightest star in Orion and the sixth-brightest in the night sky is Rigel, at the bottom right. Rigel is actually a system of three stars, the blue supergiant Rigel A with two fainter companions. Betelgeuse, at the top left, is Orion’s shoulder. Although it is between 11 and 15 times as massive as the sun, its radius is 950 times wider. This makes it one of the biggest stars we know of. It is a red
Stargazing at home online
Projects will be posted online each week at newscientist.com/maker Email: [email protected]
supergiant, so has used up its core of hydrogen and is now burning the helium around its outside. It is some 8 or 10 million years old, which is quite old for a supergiant. Such stars burn their fuel quickly and brightly. This means Betelgeuse might explode in a supernova any day now. However, before you get excited, “any day now” in astronomical terms means any time in the next million years. Now for the star-hop. Going from the right side of Orion’s Belt to the left, carry that line a little further than the distance between Betelgeuse and Rigel. At the end is Sirius, the dog star, in the constellation Canis Major.
Most stars we can see with the naked eye are binary systems, and Sirius is no exception. Sirius A and B orbit each other at a distance of between 8.2 and 31.5 astronomical units (1 AU is the distance between Earth and the sun). Sirius A is about twice as big and 25 times as bright as our sun, but Sirius B used up its hydrogen a long time ago, became a red giant and is now a white dwarf. In absolute terms, that makes Sirius quite a dim star. The only reason it appears bright is that it is just 8.6 light years away. Next week, we will be finding out how to tell the difference between a star and a planet, and spotting all those it is possible to see. ❚ 19 October 2019 | New Scientist | 51