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.
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 29th, 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 15th 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: 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 10th, 2013. An annular eclipse crossed the United States on May 10th, 1994 and will next be seen from the continental U.S. on October 14th 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 21st, 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 29th 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 3rd, 2043 and March 18th, 1950 are, however very similar in their geometry. Guy Ottewell notes in his 2014 Astronomical Calendar that the eclipses of August 29th, 1486 and January 8th, 2141 also come close to a gamma of 1.000. On the other end of the scale, the solar eclipse of July 11th 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 9th 2032 before transitioning to a hybrid and then producing its first total solar eclipse on May 31st, 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 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 29th: 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 8th and a partial solar eclipse on the 23rd… more to come! Send in those eclipse pics to the Universe Today Flickr community… you just might find yourself featured in this space!
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
The planet Venus, as imaged by the Magellan 10 mission. Credit: NASA/JPL
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
Artist’s impression of Jupiter and Io. Credit: NASA/JPL
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. 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:
Planets in our Solar system size comparison.
Largest to smallest are pictured left to right, top to bottom: Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury. Via Wikimedia Commons.
If you’re interested in planets, the good news is there’s plenty of variety to choose from in our own Solar System. From the ringed beauty of Saturn, to the massive hulk of Jupiter, to the lead-melting temperatures on Venus, each planet in our solar system is unique — with its own environment and own story to tell about the history of our Solar System.
What also is amazing is the sheer size difference of planets. While humans think of Earth as a large planet, in reality it is dwarfed by the massive gas giants lurking at the outer edges of our Solar System. This article explores the planets in order of size, with a bit of context as to how they got that way.
A Short History of the Solar System:
No human was around 4.5 billion years ago when the Solar System was formed, so what we know about its birth comes from several sources: examining rocks on Earth and other places, looking at other solar systems in formation and doing computer models, among other methods. As more information comes in, some of our theories of the Solar System must change to suit the new evidence.
Today, scientists believe the Solar System began with a spinning gas and dust cloud. Gravitational attraction at its center eventually collapsed to form the Sun. Some theories say that the young Sun’s energy began pushing the lighter particles of gas away, while larger, more solid particles such as dust remained closer in.
Artist’s conception of a solar system in formation. Credit: NASA/FUSE/Lynette Cook
Over millions and millions of years, the gas and dust particles became attracted to each other by their mutual gravities and began to combine or crash. As larger balls of matter formed, they swept the smaller particles away and eventually cleared their orbits. That led to the birth of Earth and the other eight planets in our Solar System. Since much of the gas ended up in the outer parts of the system, this may explain why there are gas giants — although this presumption may not be true for other solar systems discovered in the universe.
Until the 1990s, scientists only knew of planets in our own Solar System and at that point accepted there were nine planets. As telescope technology improved, however, two things happened. Scientists discovered exoplanets, or planets that are outside of our solar system. This began with finding massive planets many times larger than Jupiter, and then eventually finding planets that are rocky — even a few that are close to Earth’s size itself.
The other change was finding worlds similar to Pluto, then considered the Solar System’s furthest planet, far out in our own Solar System. At first astronomers began treating these new worlds like planets, but as more information came in, the International Astronomical Union held a meeting to better figure out the definition.
Hubble image of Pluto and some of its moons, Charon, Nix and Hydra. Image Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team
The result was redefining Pluto and worlds like it as a dwarf planet. This is the current IAU planet definition:
“A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.”
Jupiter (69,911 km / 43,441 miles) – 1,120% the size of Earth
Saturn (58,232 km / 36,184 miles) – 945% the size of Earth
Uranus (25,362 km / 15,759 miles) – 400% the size of Earth
Neptune (24,622 km / 15,299 miles) – 388% the size of Earth
Earth (6,371 km / 3,959 miles)
Venus (6,052 km / 3,761 miles) – 95% the size of Earth
Mars (3,390 km / 2,460 miles) – 53% the size of Earth
Mercury (2,440 km / 1,516 miles) – 38% the size of Earth
Eight planets and a dwarf planet in our Solar System, approximately to scale. Pluto is a dwarf planet at far right. At far left is the Sun. The planets are, from left, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Credit: Lunar and Planetary Institute
Jupiter is the behemoth of the Solar System and is believed to be responsible for influencing the path of smaller objects that drift by its massive bulk. Sometimes it will send comets or asteroids into the inner solar system, and sometimes it will divert those away.
Saturn, most famous for its rings, also hosts dozens of moons — including Titan, which has its own atmosphere. Joining it in the outer solar system are Uranus and Neptune, which both have atmospheres of hydrogen, helium and methane. Uranus also rotates opposite to other planets in the solar system.
The inner planets include Venus (once considered Earth’s twin, at least until its hot surface was discovered); Mars (a planet where liquid water could have flowed in the past); Mercury (which despite being close to the sun, has ice at its poles) and Earth, the only planet known so far to have life.
To learn more about the Solar System, check out these resources:
A composite of 33 Lyrid meteors captured by the UK Meteor Network cameras in 2012. Credit: @UKMeteorNetwork
The month of April doesn’t only see showers that bring May flowers: it also brings the first dependable meteor shower of the season. We’re talking about the Lyrid meteors, and although 2014 finds the circumstances for this meteor shower as less than favorable, there’s still good reason to get out this weekend and early next week to watch for this reliable shower.
The Lyrid meteor shower typically produces a maximum rate of 10-20 meteors per hour, although outbursts topping over a hundred per hour have been observed on occasion. The radiant, or the direction that the meteors seem to originate from, lies at right ascension 18 hours and 8 minutes and declination +32.9 degrees north. This is just about eight degrees to the southwest of the bright star Vega, which is the brightest star in the constellation of Lyra the Lyre, which also gives the Lyrids its name.
Fun fact: this radiant actually lies juuusst across the border of Lyra in the constellation of Hercules… technically, the “Lyrids” should be the “Herculids!” This is because the shower was identified and named in the 19th century before the International Astronomical Union officially adopted the modern layout we use for the constellations in 1922.
The rising Lyrid radiant, looking to the northeast at 2AM local from latitude 30 degrees north. Created using Stellarium.
The source of the Lyrids was tracked down in the late 1860s by mathematician Johann Gottfried Galle to Comet C/1861 G1 Thatcher, the path of which came within 0.02 Astronomical Units (A.U.s) of the Earth’s orbit on April 20th, 1861, just six weeks before the comet reached perihelion. Comet G1 Thatcher is on a 415 year orbit and won’t return to the inner solar system until the late 23rd century.
The orbital path of Comet G1 Thatcher during its 1861 passage. Credit: NASA/JPL Ephemeris Generator.
But we can enjoy the dust grains it left in its wake as they greet the Earth to burn up in its atmosphere every April. The activity of the Lyrids typically spans April 16th to the 25th, with a short 24 hour peak above a ZHR of 10 on April 22nd-23rd. Thus, like the short duration Quadrantids in January, timing is critical; if you happen to observe this shower before or after the peak, you may see nothing at all. This year, the key mornings will be Tuesday, April 22nd, and Wednesday April 23rd. The wide disparity of predictions for the exact arrival of the peak of the Lyrids, as quoted in differing sources speaks to just how poorly this meteor shower is understood. Scanning various reliable resources, we see times quoted from April 22nd at 4:00 Universal Time (UT) from the American Meteor Society, to 17:00 UT on the same date for the Royal Canadian Astronomical Society, to April 23rd at 17:45 UT from Guy Ottewell’s venerable 2014 Astronomical Calendar!
Definitely, more observations of this curious shower are needed.
The position of the Lyrid meteor shower radiant across the border in the constellation Hercules. (Credit Starry Night Education software).
Now for the bad news. This year finds the light-polluting Moon in nearly its worst location possible for a meteor shower. Remember this week’s total lunar eclipse? Well, the Moon is now waning gibbous and will reach last quarter phase at 7:52 UT/3:52 AM EDT on April 22nd, and will thus be rising at local midnight and be high in the sky towards dawn. The Lyrid radiant rises at 9:00 PM this week for observers around 40 degrees north and rides highest at 6:00 AM local, about 45 minutes before sunrise.
Looking at the International Meteor Organization’s historical data, here’s what the Lyrids have done over the past few years:
A “ZHR” is the Zenithal Hourly Rate, a theoretical maximum number of meteors that an observer could expect to witness under dark skies if the radiant was straight overhead. Note that 2011 had similar circumstances with respect to the Moon as this year, so don’t despair! The Lyrids are approaching the Earth from nearly perpendicular in its orbit and have a head on velocity of about 48 kilometres per second, respectable for a meteor shower. They also present a higher-than-average number of fireballs, with about a quarter leaving persistent trains.
Outbursts have also occurred in 1803, 1849, 1850, 1922, 1945 and 1982. United States observers based in Florida and Colorado noted a brief ZHR approaching 100 per hour back in 1982 under especially favorable New Moon conditions.
The orientation of the Earth on April 22nd at 12UT/08AM EDT. Credit: Stellarium.
Ironically, the Lyrids are also one of the oldest meteor showers identified from historic records. In fact, Galle actually traced the shower back to Chinese records dating all the way back to March 16th 687 BC, which describes “Stars (that) dropped down like rain…” clearly, the Lyrids were considerably more active in ancient times.
More recently, attempts were made to link the 2012 Sutter’s Mill meteorite fall to the Lyrids, which were underway at the time. This turned out to be a case of “meteor-wrong,” however, as described by Geoff Notkin of the Meteorite Men who noted that no meteorite fall has ever been linked to a meteor shower, though he does get lots of calls whenever news of a big meteor shower hits the press.
A good strategy for beating the Moon includes blocking it behind a hill or building while observing. Early morning is the best time to watch for Lyrids — or most any meteor shower for that matter — as you’re then on the half of the Earth facing forward into the meteor stream. And you don’t have to face toward the radiant to see Lyrid meteors, as they can appear anywhere in the sky.
With the advent of DSLRs, photographing meteors is easier than ever before. All you need to do is use a wide angle lens and take periodic time exposures of the sky. Do a few early test shots to get the combination of f-stop, ISO and shutter speed just right for current sky conditions, and be sure to review those images on a full size monitor afterward: nearly every meteor we’ve captured turned up in post-review only.
Looking to contribute to our understanding of the Lyrid meteors? Simply count the number you see and the location and length of your observation and send your report into the International Meteor Organization. And don’t forget to tweet those Lyrids to #Meteorwatch!
…and there’s more to come. Next month, a true “wildcard outburst” may be in the offing from Comet 209P/LINEAR on May 26th… can you say “Camelopardalids?”
Artist's rendering of Kepler-186f (Credit: NASA Ames/SETI Institute/Caltech)
It’s truly a “eureka” moment for Kepler scientists: the first rocky Earth-sized world has been found in a star’s habitable “Goldilocks” zone, the narrow belt where liquid water could readily exist on a planet’s surface without freezing solid or boiling away. And while it’s much too soon to tell if this really is a “twin Earth,” we can now be fairly confident that they do in fact exist.
The newly-confirmed extrasolar planet has been dubbed Kepler-186f. It is the fifth and outermost planet discovered orbiting the red dwarf star Kepler-186, located 490 light-years away. Kepler-186f completes one orbit around its star every 130 days, just within the outer edge of the system’s habitable zone.
The findings were made public today, April 17, during a teleconference hosted by NASA.
“This is the first definitive Earth-sized planet found in the habitable zone around another star,” says lead author Elisa Quintana of the SETI Institute at NASA Ames Research Center. “Finding such planets is a primary goal of the Kepler space telescope. The star is a main-sequence M-dwarf, a very common type. More than 70 percent of the hundreds of billions of stars in our galaxy are M-dwarfs.”
A visualization of the many “unseen” red dwarfs in the night sky. (CLICK FOR ANIMATION) Credit: D. Aguilar & C. Pulliam (CfA)
Unlike our Sun, which is a G-type yellow dwarf, M-dwarf stars (aka red dwarfs) are much smaller and dimmer. As a result their habitable zones are much more confined. But, being cooler stars, M-dwarfs have long lifespans, offering planets in their habitable zones — like Kepler-186f — potentially plenty of time to develop favorable conditions for life.
In addition, M-dwarfs are the most abundant stars in our galaxy; 7 out of 10 stars in the Milky Way are M-dwarfs, although most can’t be seen by the naked eye. Finding an Earth-sized planet orbiting one relatively nearby has enormous implications in the hunt for extraterrestrial life.
“M dwarfs are the most numerous stars,” said Quintana. “The first signs of other life in the galaxy may well come from planets orbiting an M dwarf.”
Still, there are many more conditions on a planet that must be met for it to be actually habitable. But size, composition, and orbital radius are very important first steps.
“Some people call these habitable planets, which of course we have no idea if they are,” said Stephen Kane, an assistant professor of physics and astronomy at San Francisco State University in California. “We simply know that they are in the habitable zone, and that is the best place to start looking for habitable planets.”
Scale comparison of the Kepler-186 system and the inner Solar System (NASA Ames/SETI Institute/Caltech)
As far as the planetary system’s age is concerned — which relates to how long life could have potentially had to evolve on Kepler-186f’s surface — that’s hard to determine… especially with M-dwarf stars. Because they are so stable and long-lived, once they’re formed M-dwarfs essentially stay the same throughout their lifetimes.
“We know it’s probably older than a few billion years, but after that it’s very difficult to tell,” BAERI/Ames scientist Tom Barclay told Universe Today. “That’s the problem with M-dwarfs.”
A comparison of the Kepler 186 and Solar systems (Presentation slide, NASA/Ames)
The exoplanet was discovered via the transit method used by NASA’s Kepler spacecraft, whereby stars’ brightnesses are continually monitored within a certain field of view. Any dips in luminance reveal the likely presence of a passing planet.
Because of its small size — just slightly over 1 Earth radius — and close proximity to its star, Kepler-186f can’t be observed directly with current telescope technology.
The Gemini North telescope on the summit of Mauna Kea (Gemini Observatory/AURA)
“However, what we can do is eliminate essentially all other possibilities so that the validity of these planets is really the only viable option,” said Steve Howell, Kepler project scientist and a co-author on the paper.
Using the latest advanced imaging capabilities of the Gemini North and Keck II observatories located atop Mauna Kea in Hawaii, astronomers were able to determine that the signals detected by Kepler were from a small orbiting planet and not something else, such as a background or companion star.
“The Keck and Gemini data are two key pieces of this puzzle,” Quintana said. “Without these complementary observations we wouldn’t have been able to confirm this Earth-sized planet.”
Kepler-186f joins the other 20 extrasolar worlds currently listed in the Habitable Exoplanets Catalog, maintained by the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo. To date 961 exoplanets have been confirmed through Kepler observations, with 1,696 total confirmed altogether. (Source)
Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
Whether Kepler-186f actually resembles Earth or not, this discovery provides more information on the incredible variety of planetary systems to be found even in our little corner of the galaxy.
“The diversity of these exoplanets is one of the most exciting things about the field,” Kane said. “We’re trying to understand how common our solar system is, and the more diversity we see, the more it helps us to understand what the answer to that question really is.”
The SETI Institute’s Allen Telescope Array has surveyed the Kepler-186 system for any potential signals but so far none has been detected. Further observations are planned.
“Kepler-186f is special because we already know that a planet of its size and distance is capable of supporting life.”
– Elisa Quintana, research scientist, SETI Institute
The team’s paper, “An Earth-sized Planet in the Habitable Zone of a Cool Star” by Elisa V. Quintana et al., will be published in the April 18 issue of Science.
This map shows the paths of Ceres and Vesta in Virgo through late June at five-day intervals. Vesta is currently magnitude +5.8 and Ceres 7.0. Both are easily visible in binoculars from suburban and rural skies. A wide view map below will help you navigate from nearby bright Mars to Zeta Virginis. From Zeta, star hop to either asteroid. Stars are shown to about magnitude +8.5. Click to enlarge. Created with Chris Marriott's SkyMap software
Don’t let them pass you by. Right now and continuing through July, the biggest and brightest asteroids will be running on nearly parallel tracks in the constellation Virgo and so close together they’ll easily fit in the same binocular field of view. The twofer features Ceres (biggest) and Vesta (brightest) which are also the prime targets of NASA’s Dawn Mission. Now en route to a Ceres rendezvous next February, Dawn orbited Vesta from July 2011 to September 2012 and sent back spectacular photos of two vast impact basins, craters stained black by carbon-rich asteroids and parallel troughs that stretch around the 330-mile-wide world like rubber bands.
This mosaic of Vesta synthesizes some of the best views the spacecraft had of the giant asteroid. The towering mountain at the south pole – more than twice the height of Mount Everest – is visible at the bottom of the image. The set of three craters known as the “snowman” can be seen at the top left. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
Astronomers used Dawn’s gravity data to discover Vesta is more like a planet than anyone had supposed. Deep beneath its crust, composed of lighter minerals, lies a denser iron core. Most asteroids were too small to generate enough interior heat through the decay of radioactive elements to melt and “differentiate” into core, mantle and crust like the terrestrial planets. Thanks to our new understanding, you’ll hear Vesta referred to as a ‘baby planet’.
A full 5.3 hour rotation of Vesta using photos taken by Dawn. Credit: NASA
Studies of its crustal rocks showed a match to a clan of basaltic meteorites called howardites, eucrites and diogenites. Many of these formerly volcanic rocks that trace their origin to Vesta are found in numerous private and institutional collections. With a little homework, you can even buy a slice of Vesta on eBay, making for one of the least expensive sample return missions ever undertaken.
Dawn’s Greatest Hits at Vesta – A quick summary of key discoveries accompanied by electric guitar
While Vesta is a rocky body, Ceres shows telltale signs of water and iron-rich clay. Like Vesta, it also appears to have cooked itself into denser core and lighter crust. Because Ceres is less dense than Earth, astronomers believe water ice may be buried beneath its dusty crust.
Dwarf planet Ceres (right) is located in the asteroid belt, between the orbits of Mars and Jupiter. Observations by ESA’s Herschel space observatory between 2011 and 2013 found that the dwarf planet has a thin water-vapor atmosphere. It’s the first unambiguous detection of water vapor around an object in the asteroid belt. Credit: ESA/ATG medialab
Earlier this year, astronomers working with the Herschel Space Telescope announced the discovery of plumes of water vapor blasting from two regions on the dwarf planet’s surface. While Ceres is an asteroid it’s also a member of a select group of dwarf planets, bodies large enough to have crunched themselves into spheres through their own gravity but not big enough to clear the region they orbit of smaller asteroids.
Vesta (left) and Ceres. Vesta was photographed up close by Dawn, while the best views we have to date of Ceres come from the Hubble Space Telescope. Notice the bright white spot which is still a mystery. Credit: NASA/ESA
Ceres and Vesta will be gradually drawing closer in the coming weeks and months until on July 5 only 10 arc minutes (one-third the diameter of a full moon) will separate them. They’ll also be fading, but not so much that binoculars won’t show them throughout this excellent dual apparition. Vesta will only dim to magnitude +7 by July 1, Ceres to 8.4. Come mid-June I’ll return with a detailed map showing how best to see the dynamic duo during their close conjunction.
To find your way to the 4th magnitude stars Zeta and Tau Virginis, which you can use with the detailed map to guide you to Ceres and Vesta, start with brilliant Mars in the southern sky and look about one fist to the left or east to spot Zeta. Map shows the sky around 10 o’clock local time in late April. Stellarium
Sure, both Ceres and Vesta look exactly like stars even in large amateur telescopes, but sampling photons from real asteroids while listening to the sound of frogs on a spring night is my idea of a good time. Maybe yours too. Good luck!
Astronaut Drew Feustel reenters the space station after completing an 8-hour, 7-minute spacewalk at on Sunday, May 22, 2011. He and fellow spacewalker Mike Fincke conducted the second of the four EVAs during the STS-134 mission. Credit: NASA
Talk about a high-flying career! Being a government astronaut means you have the chance to go into space and take part in some neat projects — such as going on spacewalks, moving robotic arms and doing science that researches the nature of the human body.
Behind the glamor and the giddiness of flight, however, astronauts also need to pay their bills on Earth. How much you get paid as an astronaut depends on what agency you work for – as well as your experience, just like any other career.
The information below for NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA) is current as of April 2014, unless otherwise noted. Three agencies do not disclose salary scales online, at least in English pages: the Japan Aerospace Exploration Agency (JAXA), the Russian Federal Space Agency (Roscosmos) and the China National Space Administration (CNSA).
NASA
Astronaut Chris Cassidy training for a spacewalk in NASA’s Neutral Buoyancy Laboratory. Credit: Robert Markowitz
NASA has 43 active astronauts and eight astronauts-in-training who were selected in 2013. Until basic training is completed, which takes about two years, selectees are called “astronaut candidates”. (Astronauts from other agencies, such as ESA and CSA, often join NASA selectees for basic training.) Then even after they’re selected, it could be years more before they take a spaceflight.
Some astronauts are hired as civilian employees while others come over from the military. Civilian astronauts are paid according to a government scale that ranges from classifications GS-11 to GS-14.
In 2012, employees living in Houston (where astronaut training facilities are located) make a minimum of $64,724 for a GS-11 to a maximum of $141,715 for a GS-14. As employees pick up more qualifications, responsibility and experience, their salaries increase.
Military salaries were not disclosed, but NASA said those employees from the armed forces “remain in an active duty status for pay, benefits, leave, and other similar military matters.”
European Space Agency
Expedition 36/37’s Luca Parmitano, a European Space Agency astronaut, moments after landing Nov. 10, 2013. Credit: NASA/Carla Cioffi
ESA’s most recent astronaut class was selected in 2009. They have all either flown in space, or have been assigned to future missions aboard the International Space Station. Astronauts are paid between the A2 and A4 scales set by the Coordinated Organisations, a group of European intergovernmental groups.
“Upon entering the ESA Astronaut Corps, new recruits will generally be paid at the A2 level. Following the successful completion of the basic astronaut training, the recruit will be paid in accordance with the grade A3. The promotion to the grade A4 generally follows after the first spaceflight,” the European Space Agency stated.
While ESA’s website does not specify the salaries for astronauts beyond the grade, another Coordinated Organisation – called the North Atlantic Treaty Organisation – lists the annual A2 salary as 58,848 Euros ($81,404) and the A4 salary as 84,372 Euros ($116,619.)
Canadian Space Agency
David Saint-Jacques (left) with fellow Canadian astronaut trainee Jeremy Hansen. The two men were selected as astronauts in 2009. Credit: NASA
Canada has two active astronauts, neither of which have been assigned to a spaceflight yet. The CSA does not disclose on its website how much astronauts make, but some information is available on the website of the Privy Council Office – an advisory group to Canada’s prime minister and senior officials.
As of 2011, astronauts are paid a minimum of $89,100 Canadian ($80,897) in Grade 1 and a maximum of $174,000 Canadian ($158,470) in Grade 3. Newly minted astronaut candidates appear to move to Level 2 upon completing basic astronaut training, which takes two years, and then increase their salary with more experience.
Military astronauts are paid according to a separate scale that was not disclosed in PCO documents.
Becoming a government astronaut
The European Space Agency’s astronaut class of 2009 (left to right): Andreas Mogensen, Alexander Gerst, Samantha Cristoforetti, Thomas Pesquet, Luca Parmitano, Timothy Peake. Credit: European Space Agency/S. Corvaja
Generally, you must be the citizen of a particular country with a space program to apply as an astronaut. U.S. astronauts are U.S. citizens, European astronauts are citizens of European countries, and so forth.
Each space agency has periodic astronaut selections where they put out a call for candidates and then winnow down the list to a handful of people selected for astronaut training. The United States had its last selection in 2013, and ESA, CSA and JAXA did theirs in 2009.
While space agencies are careful not to specify certain kinds of degrees or universities for applicants, generally speaking astronauts have technical, medical or military backgrounds.
Astronauts are best known by the public for their time in space, but in reality they will spend most of their careers on the ground. International Space Station astronauts are expected to be proficient in station systems, science and spacewalks. They also must learn how to operate the Soyuz spacecraft that gets them into space, and to learn Russian since that country is a major partner of the International Space Station.
When astronauts aren’t training, they’re working to support other missions — sometimes in locations such as NASA’s Mission Control or in pools used for spacewalk training. They additionally spend hours of time doing outreach for schools and other audiences, and travelling all over the world to the various training centers used to get people ready for spaceflight.
It’s a tough career, but those who make the trek into space say the view is totally worth it.
Astronaut Edward White, the first American to walk in space. Image Credit: NASA
Want to learn more?
The following pages give you more information on becoming an astronaut, and what to expect once you get selected.
Did the Moon appear a little on crimson side to you last night? It’s not your imagination, but it was a fine textbook example of a total lunar eclipse. This was the first total lunar eclipse visible from the Earth since late 2011, and the first of four visible from the Americas over the next 18 months.
And although much of the U.S. and Canadian eastern seaboard was under cloud cover, those west of the Mississippi River were treated to a fine show. We were the lucky exception here at Astroguyz HQ just north of Tampa Bay in Florida, as the storm front held off juuusst long enough to witness the eclipse in its entirety.
We will admit, though, that there were some tense moments. A wave of thick clouds threatened to end our session altogether just moments before the onset of totality before finally abating. We shot stills, streamed video, made observations, and heck, just stepped back once in a while to stare at the ruby-tinged beauty that was totality.
And judging from the flurry of web traffic, the odd late Monday night/ early Tuesday morning timing for this eclipse did little to stem folks interest. We noted to Virtual Star Party co-host that the excitement was reminiscent to the early morning landing of Curiosity on the Red Planet.
Anyhow, here’s just a sampling of some of the great pics currently pouring in to Universe Today:
An eclipsed Moon+Spica. Credit: Henry Weiland of Honolulu, Hawaii
Visually, we’d place this morning’s eclipse between a Danjon value of 3 and 4, with a bright yellowish rim contrasting with a dark, coppery core near the center of the umbra. One astute viewer noted during the webcast that the eclipsed Moon took on a decidedly 3-D appearance, versus its usual flat look when nearing Full.
The eclipsed Moon, Mars and Spica. Credit: @Astrocolors
And speaking of Mars, we fielded lots of “what are those bright stars nearby?” questions as well. The bright blue-white star Spica and the planet Mars “photobombed” many eclipse images. Spica just missed being occulted by the Moon during the eclipse by less than two degrees, And Mars just passed opposition this week and was at its closest approach to the Earth for 2014 on the night of the eclipse.
Approaching totality as seen from Jacksonville, Florida. Credit: Richard Hay @WinObs.
As totality approached, shutter-speeds became longer as the red edge of the Moon became apparent. It always amazes me to think that the Earth casts that long red shadow back into the void of space every night, but its only during a lunar eclipse that you actually get to see it. We’re always told that the Earth is round, but during a lunar eclipse is one of the only times that you can really witness this curve, up close and personal.
A gathering of red objects, both celestial and terrestrial. Credit: AstroVal1, New York City.
This eclipse was placed reasonably high in the sky for Northern hemisphere viewers, though that also meant a lack of pics with foreground, except of course for creative shots like the one above. And with the explosion of digital imaging technology, its amazing what folks are doing to image eclipses, even using mobile phones:
We’ve come a long way since the days of film and doing back of the envelope calculations for afocal SLR photography of the Moon, that’s for sure. Unlike solar totality, lunar eclipses are a long at stately affair. In fact, totality during this eclipse lasted for one hour and 18 minutes, about 29 minutes short of the theoretical maximum. This morning’s eclipse won’t be topped in length until 2018.
A brick red Moon in eclipse. Credit: Rob Sparks.
This also marked our first attempts at adventures in live-streaming an eclipse both on UStream and G+, which was a blast. Thanks to co-hosts and saros chasers Scott Lewis, Fraser Cain, Thad Szabo and Katie Mack (@AstroKatie) for making the broadcast a success!
As of yet, there’s no images of the eclipse from space-based assets, though some may surface. Universe Today’s Elizabeth Howell noted that NASA engineers took precautions to protect the Lunar Reconnaissance Orbiter during the event: an extended lack of sunlight is a bad thing for solar-powered spacecraft. As of yet, there’s no word as to how the LADEE spacecraft also in orbit around the Moon fared, though its due to complete its mission and crash into the Moon this month.
The eclipsed Moon and Spica. Photo by Author.
And like the “Blue,” “Super” and “Mini” Moon, the Blood Moon meme is now — for better or worse — here to stay. We’ve already fielded multiple queries for media sources asking if the current tetrad of eclipses has any special significance, and the answer is no; I would still file your taxes on this April the 15th. Eclipses happen, as do wars, earthquakes and lost car keys… each and every year.
Approaching totality. Credit: John O’Connor, Fort Pierce, Florida.
Want more? There’s no word yet as to if anyone caught any of the more bizarre challenges during this eclipse, such as completing a triple saros exeligmos, catching an ISS transit, spotting a selenelion or catching a stellar occultation during the eclipse. If you did any of the above, let us know!
And finally, the biggest post-eclipse question on everyone’s mind is always: when’s the next one? Well, Australians only have to wait two weeks until a partial solar eclipse graces their continent on April 29th… and the next total lunar eclipse once again favors North America and the Pacific region on October 8th, 2014.
T’was a great kickoff this morning of eclipse season 1 of 2 for 2014!
"Comet ISON" -- People's Choice award winner: Eric Cardoso, Setúbal, Portugal, Credit: Eric Cardoso
Comet ISON’s gone but positively not forgotten. The National Science Foundation today shared the results of their Comet ISON Photography Contest. You’ll recognize many of the names because so many of their photos have graced stories written for Universe Today.
Come take a look back at the high points of one of the most highly anticipated and studied comets of all time. Click each photo for a full-sized view. Congratulations to all the winners!
“Broom Star” — 1st place in the Through the Scope category: Damian Peach, Hampshire, U.K., Credit: Damian Peach“C/2012 S1 ISON” — 2nd place Through the Scope: Gerald Rhemann, Vienna, Austria. Credit: Gerald Rhemann“Comet ISON over Pokhara City, Nepal” — 1st place Cameras and Tripods category: Atish Aman, Delhi, India. Credit: Atish Aman“Comet ISON, Port Medway, Nova Scotia” — 2nd place Cameras and Tripods category: Barry Burgess, Nova Scotia, Canada. Credit: Barry Burgess“Comet ISON Gossamer Tail & Disconnection Event” — 1st place Piggyback Cameras category: John Chumack, Ohio, USA. Credit: John Chumack“Mercury and ISON” — 2nd place Piggyback Cameras: Gaeul Song, Korea. Credit: Gaeul Song
