Universe Today

April 23, 2014May 12, 2018 by Elizabeth Howell

The Inner and Outer Planets in Our Solar System

The Solar System. Credit: spaceplace.nasa.gov

In our Solar System, astronomers often divide the planets into two groups — the inner planets and the outer planets. The inner planets are closer to the Sun and are smaller and rockier. The outer planets are further away, larger and made up mostly of gas.

The inner planets (in order of distance from the sun, closest to furthest) are Mercury, Venus, Earth and Mars. After an asteroid belt comes the outer planets, Jupiter, Saturn, Uranus and Neptune. The interesting thing is, in some other planetary systems discovered, the gas giants are actually quite close to the sun.

This makes predicting how our Solar System formed an interesting exercise for astronomers. Conventional wisdom is that the young Sun blew the gases into the outer fringes of the Solar System and that is why there are such large gas giants there. However, some extrasolar systems have “hot Jupiters” that orbit close to their Sun.

The Inner Planets:

The four inner planets are called terrestrial planets because their surfaces are solid (and, as the name implies, somewhat similar to Earth — although the term can be misleading because each of the four has vastly different environments). They’re made up mostly of heavy metals such as iron and nickel, and have either no moons or few moons. Below are brief descriptions of each of these planets based on this information from NASA.

Mercury: Mercury is the smallest planet in our Solar System and also the closest. It rotates slowly (59 Earth days) relative to the time it takes to rotate around the sun (88 days). The planet has no moons, but has a tenuous atmosphere (exosphere) containing oxygen, sodium, hydrogen, helium and potassium. The NASA MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft is currently orbiting the planet.

The terrestrial planets of our Solar System at approximately relative sizes. From left, Mercury, Venus, Earth and Mars. Credit: Lunar and Planetary Institute

Venus: Venus was once considered a twin planet to Earth, until astronomers discovered its surface is at a lead-melting temperature of 900 degrees Fahrenheit (480 degrees Celsius). The planet is also a slow rotator, with a 243-day long Venusian day and an orbit around the sun at 225 days. Its atmosphere is thick and contains carbon dioxide and nitrogen. The planet has no rings or moons and is currently being visited by the European Space Agency’s Venus Express spacecraft.

Earth: Earth is the only planet with life as we know it, but astronomers have found some nearly Earth-sized planets outside of our solar system in what could be habitable regions of their respective stars. It contains an atmosphere of nitrogen and oxygen, and has one moon and no rings. Many spacecraft circle our planet to provide telecommunications, weather information and other services.

Mars: Mars is a planet under intense study because it shows signs of liquid water flowing on its surface in the ancient past. Today, however, its atmosphere is a wispy mix of carbon dioxide, nitrogen and argon. It has two tiny moons (Phobos and Deimos) and no rings. A Mars day is slightly longer than 24 Earth hours and it takes the planet about 687 Earth days to circle the Sun. There’s a small fleet of orbiters and rovers at Mars right now, including the large NASA Curiosity rover that landed in 2012.

The Outer Planets:

The outer planets (sometimes called Jovian planets or gas giants) are huge planets swaddled in gas. They all have rings and all of plenty of moons each. Despite their size, only two of them are visible without telescopes: Jupiter and Saturn. Uranus and Neptune were the first planets discovered since antiquity, and showed astronomers the solar system was bigger than previously thought. Below are brief descriptions of each of these planets based on this information from NASA.

Jupiter: Jupiter is the largest planet in our Solar System and spins very rapidly (10 Earth hours) relative to its orbit of the sun (12 Earth years). Its thick atmosphere is mostly made up of hydrogen and helium, perhaps surrounding a terrestrial core that is about Earth’s size. The planet has dozens of moons, some faint rings and a Great Red Spot — a raging storm happening for the past 400 years at least (since we were able to view it through telescopes). NASA’s Juno spacecraft is en route and will visit there in 2016.

Saturn: Saturn is best known for its prominent ring system — seven known rings with well-defined divisions and gaps between them. How the rings got there is one subject under investigation. It also has dozens of moons. Its atmosphere is mostly hydrogen and helium, and it also rotates quickly (10.7 Earth hours) relative to its time to circle the Sun (29 Earth years). Saturn is currently being visited by the Cassini spacecraft, which will fly closer to the planet’s rings in the coming years.

Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which it is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.

Uranus: Uranus was first discovered by William Herschel in 1781. The planet’s day takes about 17 Earth hours and one orbit around the Sun takes 84 Earth years. Its mass contains water, methane, ammonia, hydrogen and helium surrounding a rocky core. It has dozens of moons and a faint ring system. There are no spacecraft slated to visit Uranus right now; the last visitor was Voyager 2 in 1986.

Neptune: Neptune is a distant planet that contains water, ammmonia, methane, hydrogen and helium and a possible Earth-sized core. It has more than a dozen moons and six rings. The only spacecraft to ever visit it was NASA’s Voyager 2 in 1989.

To learn more about the planets and missions, check out these links:

Solar System Exploration: Planets (NASA)
NASA Photojournal (NASA)
Missions (NASA)
Space Science (European Space Agency)
USGS Astrogeology (U.S. Geological Survey)
The Solar System And Its Planets (European Space Agency)

April 22, 2014April 26, 2016 by Jason Major

Surprise: Earth Is Hit By a Lot More Asteroids Than You Thought

Sentinel will orbit the Sun, looking outwards for NEOs that could potentially impact our planet.

“The fact that none of these asteroid impacts shown in the video was detected in advance is proof that the only thing preventing a catastrophe from a ‘city-killer’ sized asteroid is blind luck.”

– Ed Lu, B612 Foundation CEO and former NASA astronaut

When we think of recent large asteroid impacts on Earth, only a handful may come to mind. In particular, one is the forest-flattening 1908 Tunguska explosion over Siberia (which may have been the result of a comet) and another is the February 2013 meteor that exploded over Chelyabinsk, shattering windows with its air blast. Both occurred in Russia, the largest country on Earth, and had human witnesses — in the case of the latter many witnesses thanks to today’s ubiquitous dashboard cameras.

While it’s true that those two observed events took place 105 years apart, there have been many, many more large-scale asteroid impacts around the world that people have not witnessed, if only due to their remote locations… impact events that, if they or ones like them ever occurred above a city or populated area, could result in destruction of property, injuries to people, or worse.

(And I’m only referring to the ones we’ve found out about over the past 13 years.)

A new video released by the B612 Foundation shows a visualization of data collected by a global nuclear weapons test network. It reveals 26 explosive events recorded from 2000 to 2013 that were not the result of nuclear detonations — these were impacts by asteroids, ranging from one to 600 kilotons in energy output.

Update: a list of the 26 aforementioned impacts and their energy outputs is below:

8/25/2000 (1-9 kilotons) North Pacific Ocean
4/23/2001 (1-9 kilotons) North Pacific Ocean
3/9/2002 (1-9 kilotons) North Pacific Ocean
6/6/2002 (20+ kilotons) Mediterranean Sea
11/10/2002 (1-9 kilotons) North Pacific Ocean
9/3/2004 (20+ kilotons) Southern Ocean
10/7/2004 (10-20 kilotons) Indian Ocean
10/26/2005 (1-9 kilotons) South Pacific Ocean
11/9/2005 (1-9 kilotons) New South Wales, Australia
2/6/2006 (1-9 kilotons) South Atlantic Ocean
5/21/2006 (1-9 kilotons) South Atlantic Ocean
8/9/2006 (1-9 kilotons) Indian Ocean
9/2/2006 (1-9 kilotons) Indian Ocean
10/2/2006 (1-9 kilotons) Arabian Sea
12/9/2006 (10-20 kilotons) Egypt
9/22/2007 (1-9 kilotons) Indian Ocean
12/26/2007 (1-9 kilotons) South Pacific Ocean
10/7/2008 (1-9 kilotons) Sudan
10/8/2009 (20+ kilotons) South Sulawesi, Indonesia
9/3/2010 (10-20 kilotons) South Pacific Ocean
12/25/2010 (1-9 kilotons) Tasman Sea
4/22/2012 (1-9 kilotons) California, USA
2/15/2013, (20+ kilotons) Chelyabinsk Oblast, Russia
4/21/2013 (1-9 kilotons) Santiago del Estero, Argentina
4/30/2013 (10-20 kilotons) North Atlantic Ocean
(Source: B612 Foundation)

To include the traditonally macabre comparison, the bomb used to destroy Hiroshima at the end of World War II was about 15 kilotons; the Nagasaki bomb was 20.

This evening former NASA astronauts Ed Lu, Tom Jones, and Apollo 8 astronaut Bill Anders will present this video to the public at a live Q&A event at the Museum of Flight in Seattle, Washington.

CEO and co-founder of the B612 Foundation, Ed Lu is working to increase awareness of asteroids and near-Earth objects with the ultimate goal of building and launching Sentinel, an infrared observatory that will search for and identify as-yet unknown objects with orbits that intersect Earth’s. The event, titled “Saving the Earth by Keeping Big Asteroids Away,” will be held at 6 p.m. PDT. It is free to the public and the visualization above is now available online on the B612 Foundation website. A press event will also be taking place at 11:30 a.m. PDT, and will be streamed live here.

Currently there is no comprehensive dynamic map of our inner solar system showing the positions and trajectories of these asteroids that might threaten Earth. The citizens of Earth are essentially flying around the Solar System with eyes closed. Asteroids have struck Earth before, and they will again – unless we do something about it.

– B612 Foundation

Want to support the Sentinel mission? Donate online here.

Added 4/24: The April 22 press conference at the Museum of Flight can be watched in its entirety below:

Technical note: While B612 and Ed Lu are presenting a new visualization on April 22, the data behind it are not entirely new. Previous surveys on NEA populations have determined within reasonable parameters the number of objects and likelihood of future impacts of varying sizes using data from WISE and ground-based observatories… see a series of slides by Alan Harris of JPL/Caltech here. (ht Amy Mainzer)

Also, if you have questions on the asteroid visualization, there are some FAQs on the B612 site here.

April 22, 2014December 23, 2015 by Nancy Atkinson

Views of Earth From Space on Earth Day 2014

It’s been said that one of the reasons Earth Day was started back in 1970 was because of the images of Earth from space taken during the Apollo missions to the Moon. So, what better way to celebrate than to see how Earth looks today from space?

NOAA’s GOES-East satellite captured this stunning view of the Americas on Earth Day, April 22, 2014 at 11:45 UTC/7:45 a.m. EDT.

Find out more about this image and what all is visible here.

More satellite images will likely be taken today, and we’ll add them as they become available.

April 22, 2014April 26, 2016 by David Dickinson

Remembering John Houbolt: the Man Who Gave Us Lunar Orbit Rendezvous

John Houbolt demonstrating Lunar Orbit Rendezvous circa 1962. Credit: NASA.

The space community lost a colossus of the of the Apollo era last week, when John Houbolt passed away last Tuesday just five days after his 95^th birthday.

Perhaps the name isn’t as familiar to many as Armstrong or Von Braun, but John Houbolt was a pivotal figure in getting us to the Moon.

Born in Altoona, Iowa on April 10^th, 1919, Houbolt spent most of his youth in Joliet, Illinois. He earned a Masters degree in Civil Engineering from the University of Illinois at Urbana-Champaign in 1942 and a PhD in Technical Sciences from ETH Zurich in Switzerland in 1957. But before that, he would become a member of the National Advisory Committee for Aeronautics (NACA) in 1942, an organization that would later become the National Aeronautics and Space Administration or NASA in 1958.

It was 1961 when Houbolt made what would be his most enduring mark on the space program. He was working as an engineer at the Langley Research Center, at a time when NASA and the United States seriously needed a win in the space race. The U.S.S.R. had enjoyed a long string of firsts, including first satellite in orbit (Sputnik 1, October 1957), first spacecraft to photograph the lunar farside (Luna 3 in October 1959) and first human in space with the launch of Yuri Gagarin aboard Vostok 1 in April 1961. A young President Kennedy would make his now famous “We choose to go to the Moon…” speech at Rice University later the next year in late 1962. Keep in mind, in U.S. astronaut John Glenn had just made his first orbital flight months before Kennedy’s speech, and total accumulated human time in space could be measured in mere hours. Unmanned Ranger spacecraft were having a tough time even getting off of the pad, and managing to crash a space probe into the Moon was considered to be a “success”. The task of sending humans “by the end of this decade” was a daunting one indeed…

NASA would soon have a mandate to sent humans to the Moon: but how could they pull it off?

Early ideas for manned lunar missions envisioned a single gigantic rocket that would head to the Moon and land, Buck Rodgers style, “fins first.” Such a rocket would have to be enormous, and carry the fuel to escape Earth’s gravity well, land and launch from the Moon, and return to Earth.

A second approach, known as Earth-orbit rendezvous, would see several launches assemble a mission in low Earth orbit and then head to the Moon. Curiously, though this was an early idea, it was never used in Apollo, though it was briefly resurrected during the now defunct Constellation Program.

Three plans to go to the Moon. Credit: NASA.

But it was a third option that intrigued Houbolt, known as Lunar Orbit Rendezvous. LOR had been proposed by rocket pioneers Yuri Kondratyuk and Hermann Oberth in 1923, but had never been seriously considered. It called for astronauts to depart the Earth in a large rocket, and instead, use a small lander designed only to land and launch from the Moon while the spacecraft for Earth return orbited overhead.

Houbolt became a staunch advocate for the idea, and spent over a year convincing NASA officials. In one famous letter to NASA associate administrator Robert Seamans, Houbolt was known to have remarked “Do we want to go to the Moon or not?”

It’s interesting to note that it was probably only in a young organization like the NASA of the early 1960s that, in Houbolt’s own words, a “voice in in the wilderness” could be heard. Had NASA become a military run organization — as many advocated for in the 1950s — a rigid chain of command could have meant that such brash ideas as Houbolt’s would have never seen the light of day. Thank scientists such as James Van Allen for promoting the idea of a civilian space program that we take for granted today.

Even then, selling LOR wasn’t easy. The idea looked preposterous: astronauts would have to learn how to undock and dock while orbiting a distant world, with no chance of rescue. There was no second chance, no backup option. Early plans called for an EVA for astronauts to enter the Lunar Module prior to descent which were later scrapped in favor of extracting it from atop the third stage and boarding internally before reaching the Moon.

Once Houbolt had sold key visionaries such as Wernher von Braun on the idea in late 1962, LOR became the way we would go to the Moon. And although Houbolt’s estimations of the mass required for the Lunar Module were off by a factor of three, the story is now the stuff of early Apollo era legend. You can see Houbolt (played by Reed Birney) and the tale of the LM and LOR in the From Earth to the Moon episode 5 entitled “Spider”.

Houbolt was awarded NASA’s medal for Exceptional Scientific Achievement in 1963, and he was in Mission Control When Apollo 11 touched down in the Sea of Tranquility.

He passed away in a Scarborough, Maine nursing home last Tuesday, and joins other unsung visionaries of the early space program such as Mary Sherman Morgan. It’s sad to think that we may soon live in a world where those who not only walked on the Moon, but those who also sent us and knew how to get there, are no longer with us.

Thanks, John… you gave us the Moon.

April 22, 2014December 23, 2015 by Elizabeth Howell

How Many Moons Does Venus Have?

A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL

There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth’s Moon to those with an atmosphere (most notably, Saturn’s Titan). Jupiter and Saturn have many moons each, and even Mars has a couple of small asteroid-like ones. But what about Venus, the planet that for a while, astronomers thought about as Earth’s twin?

The answer is no moons at all. That’s right, Venus (and the planet Mercury) are the only two planets that don’t have a single natural moon orbiting them. Figuring out why is one question keeping astronomers busy as they study the Solar System.

Astronomers have three explanations about how planets get a moon or moons. Perhaps the moon was “captured” as it drifted by the planet, which is what some scientists think happened to Phobos and Deimos (near Mars). Maybe an object smashed into the planet and the fragments eventually coalesced into a moon, which is the leading theory for how Earth’s Moon came together. Or maybe moons arose from general accretion of matter as the solar system was formed, similar to how planets came together.

The International Space Station captured as it passed in front of the Moon on Dec. 6, 2013, as seen from Puerto Rico. Credit and copyright: Juan Gonzalez-Alicea.

Considering the amount of stuff flying around the Solar System early in its history, it’s quite surprising to some astronomers that Venus does not have a moon today. Perhaps, though, it had one in the distant past. In 2006, California Institute of Technology researchers Alex Alemi and David Stevenson presented at the American Astronomical Society’s division of planetary sciences meeting and said Venus could have been smacked by a large rock at least twice. (You can read the abstract here.)

“Most likely, Venus was slammed early on and gained a moon from the resulting debris. The satellite slowly spiraled away from the planet, due to tidal interactions, much the way our Moon is still slowly creeping away from Earth,” Sky and Telescope wrote of the research.

“However, after only about 10 million years Venus suffered another tremendous blow, according to the models. The second impact was opposite from the first in that it ‘reversed the planet’s spin,’ says Alemi. Venus’s new direction of rotation caused the body of the planet to absorb the moon’s orbital energy via tides, rather than adding to the moon’s orbital energy as before. So the moon spiraled inward until it collided and merged with Venus in a dramatic, fatal encounter.”

Venus as photographed by the Pioneer spacecraft in 1978. Some exoplanets may suffer the same fate as this scorched world. Credit: NASA/JPL/Caltech

There could be other explanations as well, however, which is part of why astronomers are so interested in revisiting this world. Figuring out the answer could teach us more about the solar system’s formation.

To learn more about Venus, check out these links:

Venus (NASA)
Venus Express (European Space Agency spacecraft currently at the planet)
Venus (Astronomy Cast)
Venus (Windows To The Universe)
Venus Crater Database (Lunar and Planetary Institute)
Magellan Mission to Venus (NASA)
Chasing Venus (Smithsonian)

April 21, 2014December 30, 2015 by Nancy Atkinson

Watch: New Documentary Follows the Hunt for Gravitational Waves

A newly released documentary brings you behind the scenes in the hunt for gravitational waves. The 20-minute film, called “LIGO, A Passion for Understanding,” follows the scientists working to create one of the most powerful scientific tools ever made: the Laser Interferometer Gravitational-Wave Observatories (LIGO). You can watch the documentary above.
Continue reading “Watch: New Documentary Follows the Hunt for Gravitational Waves”

April 21, 2014December 23, 2015 by David Dickinson

Our Guide to the Bizarre April 29th Solar Eclipse

The 2013 partial eclipse rising over the Vehicle Assembly Building along the Florida Space Coast. This month's solar eclipse will offer comparable sunset views for eastern Australia. Photo by author.

Will anyone see next week’s solar eclipse? On April 29^th, an annular solar eclipse occurs over a small D-shaped 500 kilometre wide region of Antarctica. This will be the second eclipse for 2014 — the first was the April 15^th total lunar eclipse — and the first solar eclipse of the year, marking the end of the first eclipse season. 2014 has the minimum number of eclipses possible in one year, with four: two partial solars and two total lunars. This month’s solar eclipse is also a rarity in that it’s a non-central eclipse with one limit. That is, the center of the Moon’s shadow — known as the antumbra during an annular eclipse — will juuuust miss the Earth and instead pass scant kilometres above the Antarctic continent.

The "footprint" of the April 29th solar eclipse. Credit: — The “footprint” of the April 29th solar eclipse. Credit: Eclipse predictions by Fred Espenak, NASA/GSFC.

A solar eclipse is termed “non-central with one limit” when the center of the Moon’s umbra or antumbra just misses the Earth and grazes it on one edge. Jean Meeus and Fred Espenak note that out of 3,956 annular eclipses occurring from 2000 BCE to 3000 AD, only 68 (1.7%) are of the non-central variety. An annular eclipse occurs when the Moon is too distant to cover the disk of the Sun, resulting in a bright “annulus” or “ring-of-fire” eclipse. A fine example of just such an eclipse occurred over Australia last year on May 10^th, 2013. An annular eclipse crossed the United States on May 10^th, 1994 and will next be seen from the continental U.S. on October 14^th 2023. But of course, we’ll see an end the “total solar eclipse drought” long before that, when a total solar eclipse crosses the U.S. on August 21^st, 2017!

An animated .gif of the April 29th eclipse. Credit: NASA/GSFC/A.T. Sinclair.

The “centrality” of a solar eclipse or how close a solar eclipse comes to crossing the central disk of the Earth is defined as its “gamma,” with 0 being a central eclipse, and 1 as the center of the Moon’s shadow passing 1 Earth radii away from central. All exclusively partial eclipses have a gamma greater than 1. The April 29^th eclipse is also unique in that its gamma is very nearly 1.000… in fact, combing the 5,000 year catalog of eclipses reveals that no solar eclipse from a period of 2000 B.C. to 3000 A.D. comes closer to this value. The solar eclipses of October 3^rd, 2043 and March 18^th, 1950 are, however very similar in their geometry. Guy Ottewell notes in his 2014 Astronomical Calendar that the eclipses of August 29^th, 1486 and January 8^th, 2141 also come close to a gamma of 1.000. On the other end of the scale, the solar eclipse of July 11^th 1991 had a gamma of nearly zero. This eclipse is part of saros series 148 and is member 21 of 75. This series began in 1653 and plays out until 2987 AD. This saros will also produce one more annular eclipse on May 9^th 2032 before transitioning to a hybrid and then producing its first total solar eclipse on May 31^st, 2068. But enough eclipse-geekery. Do not despair, as several southern Indian Ocean islands and all of Australia will still witness a fine partial solar eclipse from this event. Antarctica has the best circumstances as the Sun brushes the horizon, but again, the tiny sliver of “annularity” touches down over an uninhabited area between the Dumont d’Urville and Concordia stations currently occupied by France… and it just misses both! And remember, its astronomical fall headed towards winter “down under,” another strike against anyone witnessing it from the polar continent. A scattering of islands in the southern Indian Ocean will see a 55% eclipsed Sun. Circumstances for Australia are slightly better, with Perth seeing a 55% eclipsed Sun and Sydney seeing a 50% partial eclipse.

The view of the eclipse from multiple locations across the Australian continent at 7:00 UT on April 29th. Created by the author using Stellarium.

Darwin, Bali Indonesia and surrounding islands will see the Moon just nick the Sun and take a less than 20% “bite” out of it. Observers in Sydney and eastern Australia also take note: the eclipse occurs low to the horizon to the west at sunset, and will offer photographers the opportunity to grab the eclipse with foreground objects. Viewing a partial solar eclipse requires proper eye protection throughout all phases. The safest method to view a partial solar eclipse is via projection, and this can be done using a telescope (note that Schmidt-Cassegrain scopes are bad choice for this method, as they can heat up quickly!) or nothing more sophisticated than a spaghetti strainer to create hundreds of little “pinhole projectors.”

A simulation of the view that no one will see: the annular eclipse one kilometre above latitude 71S longitude 131E above the Antarctic. Created using Stellarium. — A simulation of the view that no one will see: the annular eclipse as seen hovering one kilometre above the Antarctic at latitude 71S longitude 131E . Created using Stellarium.

And although no human eyes may witness the annular portion of this eclipse, some orbiting automated ones just might. We ran some simulations using updated elements, and the European Space Agency’s Sun observing Proba-2 and the joint NASA/JAXA Hinode mission might just “thread the keyhole” and will witness a brief central eclipse for a few seconds on April 29^th: And though there’ll be few webcasts of this remote eclipse, the ever-dependable Slooh is expected to carry the eclipse on April 29th. Planning an ad hoc broadcast of the eclipse? Let us know! As the eclipse draws near, we’ll be looking at the prospects for ISS transits and more. Follow us as @Astroguyz as we look at these and other possibilities and tell our usual “tales of the saros”. And although this event marks the end of eclipse season, its only one of two such spans for 2014… tune in this October, when North America will be treated to another total lunar eclipse on the 8^th and a partial solar eclipse on the 23^rd… more to come! Send in those eclipse pics to the Universe Today Flickr community… you just might find yourself featured in this space!

April 21, 2014December 23, 2015 by Nancy Atkinson

Stunning Original Drawing of the Latest SpaceX Launch

An original pencil illustration of the SpaceX CRS-3 Falcon 9 Dragon launch on April 18, 2014. Credit and copyright: Wendy Clark.

Here’s something you don’t see much anymore: an original pencil drawing of a launch. This drawing by Wendy Clark from the UK is reminiscent of the pre-spaceflight days, before we had actual images of launches, and just our dreams of spaceflight. This isn’t the first time Clark has drawn a launch (here’s an article we posted of her drawings of the MAVEN launch and the final space shuttle launch) but this one is almost a contrast in themes: the latest technology in launches from the upstart SpaceX team vs. an old-school, old fashioned, by-hand product.

For this drawing, she reiterated what she told us previously: “Don’t let anyone tell you drawing a rocket is easy!” Clark said on Flickr. “The Strongback was a complete dog of an object to draw, such a maze of engineering.”

She also captured the ‘dirty’ side of launches: “Dust and gravel being thrown up everywhere, and the lovely Falcon 9 rocket was a little grubby on lift-off and I’ve tried to reflect that in the drawing,” she said.

Thanks to Wendy Clark for sharing her work on Universe Today’s Flickr site. See more of her drawings and photography on her own Flickr page.

April 21, 2014July 26, 2016 by Elizabeth Howell

How Far Are The Planets From The Sun?

Artist's impression of the planets in our solar system, along with the Sun (at bottom). Credit: NASA

The eight planets in our solar system each occupy their own orbits around the Sun. They orbit the star in ellipses, which means their distance to the sun varies depending on where they are in their orbits. When they get closest to the Sun, it’s called perihelion, and when it’s farthest away, it’s called aphelion.

So to talk about how far the planets are from the sun is a difficult question, not only because their distances constantly change, but also because the spans are so immense — making it hard for a human to grasp. For this reason, astronomers often use a term called astronomical unit, representing the distance from the Earth to the Sun.

The table below (first created by Universe Today founder Fraser Cain in 2008) shows all the planets and their distance to the Sun, as well as how close these planets get to Earth.

Mercury:

Closest: 46 million km / 29 million miles (.307 AU)
Farthest: 70 million km / 43 million miles (.466 AU)
Average: 57 million km / 35 million miles (.387 AU)
Closest to Mercury from Earth: 77.3 million km / 48 million miles

Venus:

Closest: 107 million km / 66 million miles (.718 AU)
Farthest: 109 million km / 68 million miles (.728 AU)
Average: 108 million km / 67 million miles (.722 AU)
Closest to Venus from Earth: 40 million km / 25 million miles

Earth:

Closest: 147 million km / 91 million miles (.98 AU)
Farthest: 152 million km / 94 million miles (1.01 AU)
Average: 150 million km / 93 million miles (1 AU)

Mars:

Closest: 205 million km / 127 million miles (1.38 AU)
Farthest: 249 million km / 155 million miles (1.66 AU)
Average: 228 million km / 142 million miles (1.52 AU)
Closest to Mars from Earth: 55 million km / 34 million miles

Jupiter:

Closest: 741 million km /460 million miles (4.95 AU)
Farthest: 817 million km / 508 million miles (5.46 AU)
Average: 779 million km / 484 million miles (5.20 AU)
Closest to Jupiter from Earth: 588 million km / 346 million miles

Saturn:

Closest: 1.35 billion km / 839 million miles (9.05 AU)
Farthest: 1.51 billion km / 938 million miles (10.12 AU)
Average: 1.43 billion km / 889 million miles (9.58 AU)
Closest to Saturn from Earth: 1.2 billion km /746 million miles

Uranus:

Closest: 2.75 billion km / 1.71 billion miles (18.4 AU)
Farthest: 3.00 billion km / 1.86 billion miles (20.1 AU)
Average: 2.88 billion km / 1.79 billion miles (19.2 AU)
Closest to Uranus from Earth: 2.57 billion km / 1.6 billion miles

Neptune:

Closest: 4.45 billion km /2.77 billion miles (29.8 AU)
Farthest: 4.55 billion km / 2.83 billion miles (30.4 AU)
Average: 4.50 billion km / 2.8 billion miles (30.1 AU)
Closest to Neptune from Earth: 4.3 billion km / 2.7 billion miles

As a special bonus, we’ll include Pluto too, even though Pluto is not a planet anymore.

Uranus and Neptune, the Solar System’s ice giant planets. (Images from Wikipedia.) — *Uranus and Neptune, the Solar System’s ice giant planets. Credit: Wikipedia Commons*

Pluto:

Closest: 4.44 billion km / 2.76 billion miles (29.7 AU)
Farthest: 7.38 billion km / 4.59 billion miles (49.3 AU)
Average: 5.91 billion km / 3.67 billion miles (39.5 AU)
Closest to Pluto from Earth: 4.28 billion km / 2.66 billion miles

To learn more:

Online resources demonstrating the scale of the Solar System:

If The Moon Were Only A Pixel (Josh Worth Art & Design)
Scale Model Of Our Solar System (University of Manitoba)
Build A Solar System (Exploratorium)
Scale Solar System (Josh Wetenkamp)

Many cities and countries have also installed scale models of the Solar System, such as:

Voyage Scale Solar System (Washington, D.C.)
Sagan Planet Walk (Ithaca, N.Y.)
Maine Solar System Model
Sweden Solar System
Planet Walk (Munich, Germany)
The Solar System (Brittany, France; website in French only)
Solar System Drive (Australia)

April 21, 2014December 29, 2015 by Susie Murph

Carnival of Space #350

Carnival of Space. Image by Jason Major.

This week’s Carnival of Space is hosted by Nicole Gugliucci at her Cosmoquest blog.

Click here to read Carnival of Space #350

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.