Tag Archives: stars

Gould’s Belt

30.3-28.7 million years ago

Logarithmic History has had a lot of geology and biology lately, not so much astronomy. But all is not peaceful in the heavens.

Benjamin Gould is a nineteenth century astronomer who noted that a lot of bright stars in the sky — especially the bright blue stars that we know are very young — seem to fall along a ring tilted at a 20 degree angle to the Milky Way. This ring has come to be called Gould’s Belt. The Belt is an ellipse about 2400 by 1500 light years across where there has been a recent wave of star formation. Our Sun lies within the belt, somewhat off center; the center lies in the direction of the Pleiades.

The Belt began forming maybe thirty million years ago. We’re not sure what happened. A supernova may have set off star formation, but it would have to have been a huge one. Or it may be that a gas cloud or a clump of dark matter passed at an angle through our part of the Milky Way, and started stars forming with its shock wave. There are features resembling Gould’s Belt in other galaxies. In any case, the Belt is one of the really striking features of our part of the Milky Way.

Whatever its cause, no one disputes its magnificence. Gould’s belt is the most prominent starry feature in the Sun’s neighborhood, contributing most of the bright young stars nearby. Nearly two thirds of the massive stars within 2,000 light-years of the Sun belong to Gould’s belt. If I were kidnapped by an alien spaceship and taken to some remote corner of the Galaxy, Gould’s belt is what I’d look for to find my way back home.

Ken Crosswell. Gould’s Belt.

If you’re in the Northern hemisphere you can look at the sky tonight and see the Milky Way in an arc in the Western sky, stretching from North to South. West of the Milky Way you’ll see some of Gould’s belt, an arc of bright stars running north to south from the Pleiades, through Taurus and the bright stars of Orion, and Canis Major. So tonight look at the stars, and drink a toast if you want to your ape ancestors who were just on the cusp of splitting off from monkeys thirty million years ago.

We are stardust

The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.

Carl Sagan (h/t to commenter remanandhra)

There’s a long gap between the origin of the universe, the first stars, and early galaxies, and the origin of our Solar System and our planet Earth. If we were using a linear scale for our calendar, the Solar System would get started in September. Even on our logarithmic scale, Sun and Earth wait until late January. A spiral galaxy like the Milky Way is an efficient machine for turning dust into stars over many billions of years. But the earliest stars it produces are poor in “metals” (to an astronomer, anything heavier than helium is a metal). It takes generations of exploding stars producing heavier elements and ejecting them into space before a star like the Sun — 2% metal – can form.

Alchemists thought they could change one element into another – lead into gold, say. But it takes more extreme conditions than in any chemistry lab to transmute elements. The heart of a star makes heavy elements out of hydrogen and helium; it takes a supernova to make elements heavier than iron. So it’s literally true, not just hippy poetry, that “we are stardust” (at least the part of us that isn’t hydrogen).

Gould’s Belt

Logarithmic History has had a lot of geology and biology lately, not so much astronomy. But all is not peaceful in the heavens.

Benjamin Gould is a nineteenth century astronomer who noted that a lot of bright stars in the sky — especially the bright blue stars that we know are very young — seem to fall along a ring tilted at a 20 degree angle to the Milky Way. This ring has come to be called Gould’s Belt. The Belt is an ellipse about 2400 by 1500 light years across where there has been a recent wave of star formation. Our Sun lies within the belt, somewhat off center; the center lies in the direction of the Pleiades.

The Belt began forming maybe thirty million years ago. We’re not sure what happened. A supernova may have set off star formation, but it would have to have been a huge one. Or it may be that a gas cloud or a clump of dark matter passed at an angle through our part of the Milky Way, and started stars forming with its shock wave. There are features resembling Gould’s Belt in other galaxies. In any case, the Belt is one of the really striking features of our part of the Milky Way.

Whatever its cause, no one disputes its magnificence. Gould’s belt is the most prominent starry feature in the Sun’s neighborhood, contributing most of the bright young stars nearby. Nearly two thirds of the massive stars within 2,000 light-years of the Sun belong to Gould’s belt. If I were kidnapped by an alien spaceship and taken to some remote corner of the Galaxy, Gould’s belt is what I’d look for to find my way back home.

Ken Crosswell. Gould’s Belt.

If you’re in the Northern hemisphere and look west just after sundown tonight, you’ll see Mercury low in the sky in the constellation Taurus. Gould’s Belt runs through Taurus, and through the bright stars of Perseus, Orion, and Canis Major. So tonight look at the stars, and drink a toast if you want to your ape ancestors who were just on the cusp of splitting off from monkeys thirty million years ago.

We are stardust

There’s a long gap between the origin of the universe, the first stars, and early galaxies, and the origin of our Solar System and our planet Earth. If we were using a linear scale for our calendar, the Solar System would get started in September. Even on our logarithmic scale, Sun and Earth wait until late January. A spiral galaxy like the Milky Way is an efficient machine for turning dust into stars over many billions of years. But the earliest stars it produces are poor in “metals” (anything heavier than helium). It takes generations of exploding stars producing heavier elements and ejecting them into space before a star like the Sun — 2% metal – can form.

Alchemists thought they could change one element into another – lead into gold, say. But it takes more extreme conditions than in any chemistry lab to transmute elements. The heart of a star makes heavy elements out of hydrogen and helium; it takes a supernova to make elements heavier than iron. So it’s literally true, not just hippy poetry, that “we are stardust” (at least the part of us that isn’t hydrogen).

 

Gould’s Belt

Logarithmic History has had a lot of geology and biology lately, not so much astronomy. But all is not peaceful in the heavens.

Benjamin Gould is a nineteenth century astronomer who noted that a lot of bright stars in the sky — especially the bright blue stars that we know are very young — seem to fall along a ring tilted at a 20 degree angle to the Milky Way. This ring has come to be called Gould’s Belt. The Belt is an ellipse about 2400 by 1500 light years across where there has been a recent wave of star formation. Our Sun lies within the belt, somewhat off center; the center lies in the direction of the Pleiades.

The Belt began forming maybe thirty million years ago. We’re not sure what happened. A supernova may have set off star formation, but it would have to have been a huge one. Or it may be that a gas cloud or a clump of dark matter passed at an angle through our part of the Milky Way, and started stars forming with its shock wave. In any case, the Belt is one of the really striking features of our part of the Milky Way.

If you’re in the Northern hemisphere and look west after sundown tonight, you’ll see Venus and the Moon low in the sky, and the Milky Way above them. Gould’s Belt intercepts the Milky Way to the north and passes below it, through the bright stars of Perseus, Orion, and Canis Major and then disappears below the southern horizon. So tonight look at the stars, and drink a toast if you want to your ape ancestors who were just on the cusp of splitting off from monkeys thirty million years ago.

Sun, Earth, Moon

Our star, our planet, our satellite, some tweets.

Present at the Creation

The universe is 13.8 billion years old, give or take a few tens of millions. A lot happened at the beginning. Starting January 1st, just after midnight (Mountain Time Zone; sorry East Coasters), I’ll launch a burst of tweets covering this earliest history. I’ll give times as “time since the beginning,” in seconds, minutes, or years. Fractions of a second will be given in exponential form. So10^-43 or 10-43 seconds is 1/10,000,000,000,000,000,000,000,000,000,000,000,000,000,000 seconds. (Yes, there are 43 0’s in that fraction. This is the smallest physically meaningful unit of time – the Planck time, a quantum limit. You can’t get any closer to Zero Time than that.)

From January 2 on, I’ll report time in “years ago” not “time since the beginning,” until sometime in September, when I’ll switch to BCE/CE (equivalent to BC/AD).

There will be two big bouts of tweeting in January. January 1st will cover the beginning of the universe; inflation; the Big Bang; origins of fundamental forces, particles, atomic nuclei, and atoms; and formation of the first stars and galaxies (including the Milky Way). And January 20, and just after will cover the formation of the solar system, Earth and Moon, Earth’s first rocks and minerals, and the origin of life. Tweeting won’t be quite so intense during the rest of January.