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Explore the wonders of our incredible universe
origins • Solar System • Cosmic Phenomena • Exploration
contents
cosmic phenomena
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78 How much does The milky way weigh? 80 black holes 86 quasars 88 gamma-ray bursts 90 Space mysteries 94 auroras 96 Is Earth’s magnetic field flipping soon? 98 How did Pluto get its whale?
Credit: NASA
Credit: ESA/Hubble, NASA, M. Kornmesser
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102 Amazing Records of spaceflight 108 The Hubble Space Telescope 112 the iss 118 NASA’s one-year mission 120 Weirdest discoveries by Spirit and Opportunity 122 The James Webb Space Telescope 126 exoplanets 132 private space travel 136 space Calendar 2019
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Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)
exploration
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contents The Best space photos of
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2019 (so far) Page 8
the universe and its origins
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Credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstadt/Sean Doran
the solar system
Credit: Thinkstock
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Credit: Thinkstock
18 What is the Big Bang theory? 24 Alternatives to the Big Bang theory 26 Determining the age of the universe 28 The first stars 30 Parallel universes 34 Universe by numbers
40 Planets of the Solar System 46 What lunar craters can tell us about the Solar System 48 What we know about Mars 56 What are meteorites? 58 Earth overview 64 The sun 68 25 weirdest facts about the Solar System
amazing space photos Credit: ESA/Hubble & NASA, P. Dobbie et al.; CC BY 4.0 ABOVE: A new view from the Hubble Space Telescope features a colorful open star cluster known as Messier 11. This group of stars is nicknamed the “Wild Duck Cluster” because its brightest members form the shape of the letter “V,” resembling a flock of flying ducks. Messier 11 is located more than 6,000 light-years from Earth in the constellation Scutum, and astronomers believe the cluster formed about 220 million years ago.
Credit: NASA/Lee Wingfield
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amazing space photos
Two sounding rockets created this colorful light display in the night sky as they launched on a mission to study Earth’s auroras. NASA’s Auroral Zone Upwelling Rocket Experiment (AZURE) mission launched two Black Brant XI-A sounding rockets on April 5 from the Andøya Space Center in Norway.
Credit: NASA/ESA/Hubble/STScI/AURA/W. Sparks/R. Sahai
BELOW: The Egg Nebula, seen here in a view from the Hubble Space Telescope, is a “preplanetary nebula,” or a cloud of dust and gas ejected from a dying star and illuminated by the star’s last bit of light. Located about 3,000 light-years away from Earth in the Cygnus constellation, the faint Egg Nebula was first spotted by astronomers in the 1970s, and it was the first nebula of its kind that anyone had ever seen. It was then imaged by Hubble in the 1990s.
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The universe and its origins
Parallel Universes: Theories & Evidence Our universe may live in one bubble that is sitting in a network of bubble universes in space
Words: Elizabeth Howell
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s our universe unique? From science fiction to science fact, there is a concept that suggests that there could be other universes besides our own, where all the choices you made in this life played out in alternate realities. The concept is known as a “parallel universe,” and is a facet of the astronomical theory of the multiverse. The idea is pervasive in comic books, video games, television and movies. Franchises ranging from “Buffy the Vampire Slayer” to “Star Trek” and “Doctor Who” to “Digimon” use the idea to extend plotlines (see the boxout on page 33 for more pop culture examples). There actually is quite a bit of evidence out there for a multiverse. First, it is useful to understand how our universe is believed to have come to be.
light began to shine through. Eventually, the small particles began to form into the larger pieces of matter we know today, such as galaxies, stars and planets. One big question with this theory is: are we the only universe out there? With our current technology, we are limited to observations within this universe because the universe is curved and we are inside the fishbowl, unable to see the outside of it (if there is an outside). There are at least five main theories why a multiverse is possible:
Did you know...?
What are the arguments for a multiverse?
We don’t know what the shape of space-time is exactly. One prominent theory is that it is flat and goes on forever. This would present the possibility of many universes being out there. But with that topic in mind, it’s possible that universes can start repeating themselves. That’s because particles can only be put together in so many ways. More about that in a moment.
An idea from string theory is that parallel ‘braneworlds’ exist in a higher-dimensional space
Around 13.8 billion years ago, simply speaking, everything we know of in the cosmos was an infinitesimal singularity. Then, according to the Big Bang theory, some unknown trigger caused it to expand and inflate in three-dimensional space. As the immense energy of this initial expansion cooled,
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1. Infinite universes
2. Bubble universes Another theory for multiple universes comes from “eternal inflation.” Based on research from Tufts University cosmologist Alexander Vilenkin, when
The universe and its origins
Our universe could just be one of an infinite number of others
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the solar system
lunar craters What Moon craters can tell us about Earth and our solar system Words: Meghan Bartels
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steroid impacts have a bad reputation here on Earth – it’s the dinosaurs’ signature public relations victory – but it’s the moon that really bears the scars of living in our messy neighborhood. That’s because Earth has an arsenal of forces that slowly wear away the craters left behind by impacts. And that’s frustrating for scientists who want to better understand the debris hurtling around our solar system. So a 2019 study uses the pockmarked lunar surface to trace the history of things smashing into both our Moon and Earth, finding signs that our neighborhood got a lot messier about 290 million years ago. “It’s a cool study that talks about our dynamic solar system and it’s good that it’s out there,” Nicolle Zellner, a physicist at Albion College in Michigan (not involved in the research), told Space.
A comparison of the near (right) and far (left) side of the Moon
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com. “It’ll get people thinking and testing it, so that’s exciting.” Earth and the Moon are close enough on the solar system scale that stray asteroids should crash into each at about the same frequency. Earth may attract a few extra with its stronger gravity, and Earth likely suffers more hits because of its larger surface area – but in terms of impact per square mile, they should be clocking in about the same. Scientists have identified only about 180 impact craters here on Earth, as opposed to hundreds of thousands of lunar impact craters. Earth wipes them away with winds and rainfall, oceans and plate tectonics. “The Moon is perfect for studying craters,” Sara Mazrouei, a planetary scientist who led the new research during her doctoral studies at the University of Toronto, told Space.com. “Everything stays there.”
But in order to trace the history of impacts, scientists needed to not just identify craters, but also estimate their ages. And that’s much harder on the Moon than on Earth, since geologists can’t currently sample lunar craters directly. So the team behind the new research settled on what may be a surprising measurement: how well nearby rocks retain heat during the long, cold lunar night. That might seem like an awfully random measurement. But when a large impactor strikes the Moon, it scoops out a crater and litters the surrounding landscape with boulders sourced from that material. Over time, those rocks are struck by smaller impactors that break them into smaller and smaller rocks, which eventually become dusty regolith, so the team argued that older craters would be surrounded by finer rocks and younger craters by larger ones.
the solar system Melosh, a planetary scientist at Purdue University who wasn’t involved in the new research, told Space.com. In particular, he’s not sold on the boulder- disintegration model they used – he thinks it doesn’t properly account for how that process speeds up as rocks get smaller. And he doesn’t see enough Earth craters to support solid statistical analyses; he worries that they’re working from too small a sample size. “That doesn’t mean it’s wrong, but it also doesn’t mean that it’s right – we just really don’t know,” Melosh said. “This is a noble attempt to go just a little bit farther than the data support.” Zellner understands how difficult studying lunar craters can be: she’s worked with the droplets of glass created by impacts and carried back to Earth in samples gathered by the Apollo astronauts. But dating that glass is still a challenge even with today’s lab technology, and the samples all come from a small patch of the Moon’s surface. Orbiter data puts scientists at more of a distance, but covers the entire lunar surface – neither method is perfect. “We’re doing the best we can with what we have now,” Zellner said. “This is science, right? We put ideas out there, and then we find ways to test those ideas, and the idea either stands the test of time or it doesn’t.” And all three scientists offered compelling reasons why doing the work to figure out the Moon’s impact history is worthwhile. First, of course, there’s the self-interested approach:
Earth craters can come with some unpleasant side effects. “Everybody is interested in the cratering rate on Earth because we don’t want to end up like the dinosaurs,” Melosh said. The catastrophic aftermath of the impact wiped out a staggering three-quarters of all species alive at the time, although this mass extinction left plenty of room for our own mammalian ancestors to thrive and evolve. “We should thank our lucky meteorite, but it was pretty bad for everybody else on the planet.” Learn enough about impacts, the theory goes, and we may be able to save our own skins the next time around. For Zellner, there’s a more exotic appeal as well: Learning more about our own solar system could help scientists understand not just our own neighborhood, but also the processes that have shaped the many alien solar systems that scientists keep discovering. Mazrouei sees the work as an example of how different solar system bodies can shed light on each other. One of her co-authors is already looking forward to how the BepiColombo mission to Mercury, armed with an instrument much like that at the moon now, will be able to add another dimension to cratering studies. Earth is great to live on, but scientists can’t piece together its past from home. It takes studying the Moon and its pristinely cratered surface to understand what our planet has been through, Mazrouei said. “We get to detangle a lot of Earth’s history as well.”
“Learn enough about impacts, and we may be able to save our own skins the next time around”
Credit: NASA MSFC
Then, when that landscape transitions from a 14-day lunar day to a 14-day lunar night, it changes temperature at different rates. “The idea is that big rocks can hold heat throughout the night, whereas that regolith or sand loses heat,” Mazrouei said. “As craters get older, they become less rocky.” In turn, they cool off faster. So Mazrouei and her colleagues looked at thermal imaging data from an instrument called the Diviner on board NASA’s Lunar Reconnaissance Orbiter, which has been circling the Moon since 2009. The team identified 111 individual craters that they knew were less than 1 billion years old, analyzed their heat signatures and, using a model of how quickly lunar boulders disintegrate, estimated their age. The result showed an intriguing pattern: a spike in impact rates about 290 million years ago, when cratering rates appear to have more than doubled. That would suggest something significant changed in our solar system around then – perhaps, the team proposes, a large space rock in the Asteroid Belt breaking up and wandering closer to Earth and the Moon. And comparing the craters we do know about here on Earth to their results, the team sees similar patterns, suggesting scientists have found a pretty representative, if small, collection of craters. Not everyone is convinced, however. “The results are intriguing, but I think that the actual support for these conclusions is pretty weak,” Jay
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the solar system
25 weirdest solar system facts Read on to find out some of the strangest facts about planets, dwarf planets, comets and other incredible objects around the solar system Words: Elizabeth Howell
Uranus appears to be a featureless blue ball upon first glance, but this gas giant of the outer solar system is pretty weird upon closer inspection. First, the planet rotates on its side for reasons scientists haven’t quite figured out. The most likely explanation is that it underwent some sort of one or more titanic collisions in the ancient past. In any case, the tilt makes Uranus unique among the solar system planets. Uranus also has tenuous rings, which were confirmed when the planet passed in front of a star (from Earth’s perspective) in 1977; as the star’s light winked on and off repeatedly, astronomers realized there was more than just a planet blocking its starlight. More recently, astronomers spotted storms in Uranus’ atmosphere several years after its closest approach to the sun, when the atmosphere would have been heated the most.
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Credit: Thinkstock
Uranus is tilted on its side
the solar system
Jupiter's moon Io has towering volcanic eruptions Io’s eruptions come from the immense gravity the moon is exposed to, being nestled in Jupiter’s gravitational well. The moon’s insides tense up and relax as it orbits closer to, and farther from, the planet, generating enough energy for volcanic activity. Scientists are still trying to figure out how heat spreads through Io’s interior, though, making it difficult to predict where the volcanoes exist using scientific models alone.
Credit: Getty Images
For those of us used to Earth’s relatively inactive moon, Io’s chaotic landscape may come as a huge surprise. The Jovian moon has hundreds of volcanoes and is considered the most active moon in the solar system, sending plumes up to 250 miles into its atmosphere. Some spacecraft have caught the moon erupting; the Pluto-bound New Horizons craft caught a glimpse of Io bursting when it passed by in 2007.
Mars also has the longest valley
Credit: Thinkstock
If you thought the Grand Canyon was big, that’s nothing compared to Valles Marineris. At 2,500 miles (4,000 km) long, this immense system of Martian canyons is more than 10 times as long as the Grand Canyon on Earth. Valles Marineris escaped the notice of early Mars spacecraft (which flew over other parts of the planet) and was finally spotted by the global mapping mission Mariner 9 in 1971. And what a sight to miss – Valles Marineris is about as long as the US! The lack of active plate tectonics on Mars makes it tough to figure out how the canyon formed. Some scientists even think that a chain of volcanoes on the other side of the planet, known as the Tharsis Ridge, somehow bent the crust from the opposite side of Mars.
Mars has the biggest volcano (that we know of) While Mars seems quiet now, we know that in the past something caused gigantic volcanoes to form and erupt. This includes Olympus Mons, the biggest volcano ever discovered in the solar system. At 374 miles (602 km) across, the volcano is comparable to the size of Arizona. It’s 16 miles (25 km) high – triple the height of Mount Everest.
Volcanoes on Mars can grow to such immense size because gravity is much weaker on the Red Planet than it is here on Earth. But how those volcanoes came to be in the first place is not well known. There is a debate among scientists as to whether or not Mars has a global plate tectonic system and whether it is active.
Venus has superpowerful winds Venus is a hellish planet with a high-temperature, high-pressure environment on its surface. Ten of the Soviet Union’s heavily shielded Venera spacecraft lasted only a few minutes on its surface when they landed there in the 1970s. But even above its surface, the planet has a bizarre environment. Scientists have found that its upper winds flow 50 times faster than the planet’s rotation. The European Venus Express spacecraft (which orbited the planet between 2006 and 2014) tracked the winds over long periods and detected periodic variations. It also found that the hurricane-force winds appeared to be getting stronger over time.
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Exploration
Bizzare Mars
The weirdest Martian discoveries by the Opportunity and Spirit rovers Words: Hanneke Weitering
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A mysterious object that bears a striking resemblance to a powdered, jelly-filled doughnut mysteriously appeared in front of the Opportunity rover’s panoramic camera on January 8, 2014. Previous images of that exact same spot were suspiciously doughnut-free. No one knew what it was or where it came from, but people on Earth were captivated by the Martian doughnut – you could say… they were eating it up! After several weeks of analyzing the images taken by Opportunity, NASA scientists determined that what looked like a jelly-filled pastry was actually just a plain old rock that had been kicked up and displaced by the rover’s wheels as it drove around.
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The twin Spirit and Opportunity rovers both landed on Mars in 2004
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A Martian bunny rabbit
NASA’s Opportunity rover never found life on Mars, but in a photo of Meridiani Planum, it did find a mysterious object that looks like a long-eared bunny rabbit. The image was released in March 2004 (about two months after Opportunity arrived at the Red Planet) as part of the rover’s “mission success” panorama. The bunny’s ears appeared to move slightly in the weak Martian wind, so it couldn’t have been a rock. NASA engineers said it appears to be “a piece of soft material that definitely came from our vehicle,” like cotton insulation or a Vectran cover.
Credit: NASA
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Jelly doughnut
Credit: NASA/JPL-Caltech
ASA’s Opportunity rover has officially concluded its 15-year mission on Mars, the agency announced in February 2019. Eight months after a raging dust storm incapacitated Opportunity’s solar panels, leaving it unable to communicate with Earth, NASA has stopped waiting for it to wake up and will no longer listen for signals from the rover. Opportunity, NASA’s longest-running Mars rover, outlived its twin rover, Spirit, which went silent in 2010 after getting stuck in a sand trap and running out of power. Both rovers launched to the Red Planet in 2003 and are collectively known as NASA’s Mars Exploration Rovers. The twin rovers made some remarkable scientific discoveries over the course of their missions on the Red Planet. Here we’ll focus on some of the stranger things Opportunity and Spirit have spotted on Mars.
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exploration
Credit:: NASA/JPL-Caltech/Cornell/USCS
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Credit: NASA/JPL-Caltech/Cornell University
Just a few months after the Opportunity rover arrived at the Red Planet, its cameras spotted this deceptively delicious-looking patch of rocks near the landing site. Not knowing exactly what they were looking at, scientists starting calling these strangely spherical rocks “blueberries.” It’s unclear exactly how these rocks came to be, but scientists believe that they constitute one of the earliest pieces of evidence that Mars had a very watery past.
A person on Mars?
Opportunity’s twin, a nearly identical rover named Spirit, also made some strange discoveries during its time roving around the Red Planet. In 2007, Spirit snapped a photo of what vaguely resembles a human-like figure perched on a rock. While some interpreted the image to be evidence of life on Mars, NASA has assured everyone that the “figure” was just a rock.
The first extraterrestrial meteorite
On Jan. 6, 2005, the Opportunity rover found a basketball-size meteorite on Mars – the first meteorite ever discovered on another planet. Opportunity’s spectrometers scoped out the space rock and determined that it’s mostly made of iron and nickel. NASA named the meteorite Heat Shield Rock because it was spotted near Opportunity’s heat shield, which was discarded during the rover’s landing in 2003.
Credit: NASA/JPL/Cornell
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Blueberries on Mars
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