“The universe is made of stories, not of atoms.”
~ Muriel Rukeyser, American Poet
A Nebula Story
The story of the Sun and Earth, and therefore us, is a story of a long-ago nebula. A nebula is an extremely vast space cloud of mostly hydrogen gas, but plenty of dust, too. Basically, nebulae are either collapsing to make new stars, or they are expanding — the result of the star losing its ability to sustain nuclear fusion.
Our nebula story starts when the Sun reached critical mass and “switched on” — some 4.6 billion years in the past. This occurs when an unfathomable amount of hydrogen accumulates, pulls itself into a ball via gravity, and starts to shine by nuclear fusion — the blistering conversion of hydrogen into helium and energy.
Most of this spinning nebula’s mass — 99.8% — coalesced into the ferocious Sun. The left over scattered debris — the remaining 0.2% — became the planets, moons, comets, asteroids, and meteoroids. More than half of this leftover mass became Jupiter.
Our solar system story is not one of an only child. The nebula gave birth to numerous stars; the entire stellar family from this one ancient nebula is estimated to be anywhere from 1,000 to 10,000 stars. Strange to imagine the Sun has so many stellar siblings… Where are they?
One family member is now called HD 162826. The remote star is 110 light years away and lives in the constellation Hercules. Spectra analysis has determined the chemical composition of HD 162826 matches the Sun. Each star contains similar trace amounts of the elements barium and yttrium. Astronomers also have tracked its orbit backwards around the galactic core and compared it to the Sun’s orbit. These orbital paths point to a similar place of origin.
The discovery of a solar sibling is new, announced in May 2014 by scientists at the University of Texas. The thousands of remaining siblings are unknown. After the billions of years since the Sun and Earth’s birth, these stars drifted far apart from each other—making them difficult to find and study. HD 162826 is believed to be the Sun’s closest sibling.
Exploring the Sun’s beginning from a long-ago nebula allows us to take a second glance at nebulae we see today. The gorgeous Waterfall Nebula above is an enormous space cloud being lit by its newly born stars. The glowing golden arc extends 10 light years from top to bottom; you could fit about six solar systems along its path! Another great stellar nursery, one we show often in the Planetarium, is the Orion Nebula. Star formation here is also estimated in the thousands and may come in different stages.
The Sun was born out of a nebula and will die giving birth to a new nebula. The Sun’s concluding chapter will start about five billion years from now. The amount of hydrogen the Sun has been vigorously fusing into helium for 10 billion years will slowly run out. The Sun is large enough—as stars go—to fuse this helium “ash” into heavier elements. It will grow hotter until it begins to expand gradually. Eventually, the bulging Sun will engulf Mercury, Venus, and the Earth, and a new nebula will be born.
Astronomers witness this stellar death process playing itself out in many nebulae across the galaxy. The gas and dust clouds created from these bulging space clouds are called planetary nebulae, because the first ones discovered looked like planets. But they can look very different, too. A beautiful example is the Butterfly Nebula. This debris comes from a star that was once larger than the Sun. It is about 3,400 light years away in the constellation Scorpius.
Eventually, these expanding death nebulae will thin out and become drifting interstellar debris. Maybe some will encounter other space clouds from other stars that have run out of fuel. These clouds might mix with even more stellar wreckage and grow stronger. Their combined gravity might be enough to pull them inward into balls of nuclear fusion — stars.
These stellar birth and death stories occur constantly throughout the universe. The real wonder is, are we the only ones writing their stories?
Find the "X" Moon
This striking “X” is a stunning new transportation facility built by an alien civilization from Mars.
Okay, sorry, that’s not true. It’s April Fool’s Day and I couldn’t resist!
The “X” is simply light and show of crater walls and crater floors. The strange lunar marker is fairly easy to spot, but you will need binoculars or a small telescope. Most people have never seen it, but if you’re up for a challenge, you have a short window. The lunar “cross” lasts for only a few hours before the Moon's first quarter phase. The “X” can be seen along the terminator — the shadow line between lunar day and night. The “X” is produced by low sunlight illuminating crater walls. The dark parts are the much deeper floors of the crater.
Observing the Moon’s power through a telescope can be a powerful event — with or without seeing the “X.” Check out this video. >>
(Remember, you can always look through a telescope at your local astronomy club.)
Another Pizza in the Solar System
When Jupiter’s moon Io was first seen by Voyager 1 in March 1979, it discovered a very different surface. Oranges and yellows covered the innermost moon. Soon, NASA and the world were wondering, why? A few months later, a plume of sulfur gas was spotted jetting from the moon’s surface. Io was geologically active. Volcanoes erupted here.
Io’s proximity to Jupiter was the culprit. The gas giant’s gravity pulls on the close side of Io more than the far side. This tidal tugging stretches Io back and forth, causing the heat and energy that produce the eruptions on the surface.
The stunning images of Io soon had many people calling it the “pizza moon.” Now, nearly 40 years later, new pictures of Jupiter make you want to call it the “pizza planet”!
Of all the stunning pictures of the largest planet, we never imaged its polar regions — until now, thanks to NASA’s Juno spacecraft.
Jupiter’s new pizza appearance is caused by cyclones that churn and whirl around each other near the poles. Juno’s new infrared mosaic reveals eight storms around a central storm in the north pole. In the south polar area, five storms surround the one in the middle. These octagon- and pentagon-shaped series of swirls were not totally surprising for Jupiter scientists. Not long ago, a six-sided (hexagon) storm was photographed at Saturn’s North Pole. The main difference between the two gas giants is Jupiter’s tempests are multiple, while Saturn’s storm is singular.
Jupiter has always been a colorful planet—think of its Great Red Spot. Scientists have long seen many dynamic storms all over its surface. These are caused by Jupiter’s hot interior rising, caused by its immense mass, and its cold cloud tops descending, caused by its considerable distance from the Sun. Jupiter’s fast rotation—once every 9.9 hours—causes its many layered bands. Their colors are due to the different levels of energy received from the Sun.
Venus climbs a little higher in the west this April. Look for the nearby Pleiades star cluster and the bright red star Aldebaran in Taurus the bull. A crescent Moon wanders by on the nights of April 17-18.
As April ends, it means it’s the last chance to see Orion in the evening sky until next November! Look fairly soon after sunset low in the western sky. Venus will be easy to spot; scan south and look for all of Orion’s bright stars—and the dog-star Sirius, too!
Jupiter moves firmly into the evening sky this month. It rises a little before 11:00 p.m. CDT on April Fool’s night and then by 8:45 p.m. CDT at April’s end. Watch the Moon orbit by twice this month. You will have to stay up later (about 11:00 p.m.) for the first pass on the nights of April 2-3. The second sighting of Jupiter and the Moon occurs soon after sunset on April 28-30.
Mars and Saturn switch places early this month. From April 1-3, notice their positions change as the faster Mars passes Saturn. They appear close, but remember it’s only a line-of-sight effect; these two planets are about 750,000,000 miles apart! The Moon joins the planets and the stars of Sagittarius on the mornings of April 6-8.
Mercury is too close to the Sun to see all month.
See the Universe through a telescope! Join one of the Milwaukee-area astronomy clubs and spot craters on the Moon, the rings of Saturn, the moons of Jupiter, and much more.
Send an e-mail to Planetarium Director Bob Bonadurer at firstname.lastname@example.org and place 'subscribe' in the subject line to receive the Starry Messenger and monthly star map.
Follow Bob on Twitter @MPMPlanetarium.