MarCO-B, one of the experimental Mars Cube One (MarCO) CubeSats, took this image of Mars from about 4,700 miles (6,000 km) away during its flyby of the Red Planet on November 26, 2018. MarCO-B was flying by Mars with its twin, MarCO-A, to attempt to serve as communications relays for NASA’s InSight spacecraft as it landed on Mars. Image via NASA/JPL-Caltech.
NASA’s MarCO mission was built to see whether two experimental, briefcase-sized spacecraft could survive the trip to deep space, and the two CubeSats proved more than able. After cruising along behind NASA’s InSight for seven months, they successfully relayed data back down to Earth from the lander during its descent to the Martian surface yesterday (Monday, November 26, 2018).
Nicknamed “EVE” and “WALL-E” after the stars of the 2008 Pixar film, MarCO-A and MarCO-B used experimental radios and antennas, providing an alternate way for engineers to monitor the landing. The CubeSats provided information to InSight’s landing team in just 8 minutes – the time it took for radio signals to travel from Mars to Earth. That was much faster than waiting on NASA’s Mars orbiters, which weren’t positioned to be able to observe the entire event and send data back to Earth immediately.
Andy Klesh is MarCO chief engineer at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, which built the CubeSats. Klesh said in a statement:
WALL-E and EVE performed just as we expected them to. They were an excellent test of how CubeSats can serve as ‘tag-alongs’ on future missions, giving engineers up-to-the-minute feedback during a landing.
Landing on Mars is exceptionally difficult: Before InSight, only about 40 percent of all attempts by various nations had succeeded. Even if a spacecraft doesn’t survive landing, having a “black box” – or a pair of them, as with MarCO – to record the event can help engineers design better landing technology.
Neither of the MarCO CubeSats carry science instruments, but that didn’t stop the team from testing whether future CubeSats could perform useful science at Mars. As MarCO-A flew by, it conducted some impromptu radio science, transmitting signals through the edge of Mars’ atmosphere. Interference from the Martian atmosphere changes the signal when received on Earth, allowing scientists to determine how much atmosphere is present and, to some degree, what it’s made of.
John Baker is JPL’s program manager for small spacecraft. He said:
CubeSats have incredible potential to carry cameras and science instruments out to deep space. They’ll never replace the more capable spacecraft NASA is best known for developing. But they’re low-cost ride-alongs that can allow us to explore in new ways.
As a bonus, some consumer-grade cameras aboard MarCO provided “drive-by” images as the CubeSats sailed past Mars. MarCO-B was programmed to turn so that it could image the planet in a sequence of shots as it approached Mars (before launch, MarCO-A’s cameras were found to be either non-functioning or too blurry to use).
After the landing, MarCO-B turned backward to take a farewell shot of the Red Planet. It also attempted to snap some photos of Mars’ moons, Phobos and Deimos.
Bottom line: The 2 briefcase-sized CubeSats successfully relayed data back down to Earth from Insight during its descent to the Martian surface on Monday, November 26, 2018.
Bottom line: NASA heard from the MarCO CubeSats loud and clear from Mars on November 26, 2018.
from EarthSky https://ift.tt/2FK6zoC
MarCO-B, one of the experimental Mars Cube One (MarCO) CubeSats, took this image of Mars from about 4,700 miles (6,000 km) away during its flyby of the Red Planet on November 26, 2018. MarCO-B was flying by Mars with its twin, MarCO-A, to attempt to serve as communications relays for NASA’s InSight spacecraft as it landed on Mars. Image via NASA/JPL-Caltech.
NASA’s MarCO mission was built to see whether two experimental, briefcase-sized spacecraft could survive the trip to deep space, and the two CubeSats proved more than able. After cruising along behind NASA’s InSight for seven months, they successfully relayed data back down to Earth from the lander during its descent to the Martian surface yesterday (Monday, November 26, 2018).
Nicknamed “EVE” and “WALL-E” after the stars of the 2008 Pixar film, MarCO-A and MarCO-B used experimental radios and antennas, providing an alternate way for engineers to monitor the landing. The CubeSats provided information to InSight’s landing team in just 8 minutes – the time it took for radio signals to travel from Mars to Earth. That was much faster than waiting on NASA’s Mars orbiters, which weren’t positioned to be able to observe the entire event and send data back to Earth immediately.
Andy Klesh is MarCO chief engineer at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, which built the CubeSats. Klesh said in a statement:
WALL-E and EVE performed just as we expected them to. They were an excellent test of how CubeSats can serve as ‘tag-alongs’ on future missions, giving engineers up-to-the-minute feedback during a landing.
Landing on Mars is exceptionally difficult: Before InSight, only about 40 percent of all attempts by various nations had succeeded. Even if a spacecraft doesn’t survive landing, having a “black box” – or a pair of them, as with MarCO – to record the event can help engineers design better landing technology.
Neither of the MarCO CubeSats carry science instruments, but that didn’t stop the team from testing whether future CubeSats could perform useful science at Mars. As MarCO-A flew by, it conducted some impromptu radio science, transmitting signals through the edge of Mars’ atmosphere. Interference from the Martian atmosphere changes the signal when received on Earth, allowing scientists to determine how much atmosphere is present and, to some degree, what it’s made of.
John Baker is JPL’s program manager for small spacecraft. He said:
CubeSats have incredible potential to carry cameras and science instruments out to deep space. They’ll never replace the more capable spacecraft NASA is best known for developing. But they’re low-cost ride-alongs that can allow us to explore in new ways.
As a bonus, some consumer-grade cameras aboard MarCO provided “drive-by” images as the CubeSats sailed past Mars. MarCO-B was programmed to turn so that it could image the planet in a sequence of shots as it approached Mars (before launch, MarCO-A’s cameras were found to be either non-functioning or too blurry to use).
After the landing, MarCO-B turned backward to take a farewell shot of the Red Planet. It also attempted to snap some photos of Mars’ moons, Phobos and Deimos.
Bottom line: The 2 briefcase-sized CubeSats successfully relayed data back down to Earth from Insight during its descent to the Martian surface on Monday, November 26, 2018.
Cassini spacecraft image from 2010 of Saturn’s moon Enceladus. The moon is backlit, with its dark outline crowned by glowing jets from the south polar region. Notice that there are several separate jets, or sets of jets, emanating from the fissures known to scientists as “tiger stripes.” Image via NASA/JPL/Space Science Institute.
Saturn’s moon Enceladus is very small – only about 310 miles (500 kilometers) across – but it may hold clues to one of the biggest mysteries of all time – are we alone? Beneath the icy crust lies a global salty ocean, not too different from Earth’s oceans. Could that ocean contain life of some kind? That is a question that many scientists – and the public alike – would like to find an answer for. Enceladus, however, is very far away and planetary missions are expensive – but there may be an ideal solution.
Billionaire entrepreneur and physicist Yuri Milner wants to send a private mission back to this intriguing world, and NASA wants to help him. This incredible idea was first reported in New Scientist on November 8, 2018 (please note this article is behind a paywall). It was then reported by Gizmodo the same day.
Agreements signed by NASA and Milner’s non-profit Breakthrough Starshot foundation in September show that the organizations are working on scientific, technical and financial plans for the ambitious mission. NASA has committed over $70,000 to help produce a concept study for a flyby mission. The funds won’t be paid to Breakthrough but represent the agency’s own staffing costs on the project.
Enceladus is a very small moon, but it has a global ocean beneath its icy crust. Image via NASA/JPL-Caltech.
Breakthrough Initiatives, part of Milner’s non-profit Breakthrough Starshot Foundation, would lead and pay for the mission, with consultation from NASA. The board of Breakthrough Initiatives includes billionaires Yuri Milner and Mark Zuckerberg, and the late physicist Stephen Hawking. Breakthrough Initiatives has been studying various mission concepts for space exploration, including a solar sail to nearby stars, advancing the technology to discover other Earth-like planets and sending out a direct message, similar to the previous Arecibo message, specifically to try and catch the attention of aliens.
Enceladus has become a prime target in the search for extraterrestrial life in our solar system, since its subsurface ocean is thought to be quite similar to oceans on Earth, thanks to data from the Cassini mission, which orbited Saturn from 2004 until September 2017. Scientists already know it is salty and there is evidence for geothermal activity on the ocean floor, similar to “smoker” volcanic vents on the bottom of oceans on Earth. Such geothermal vents – at least on Earth – are oases for a wide variety of ocean life despite the darkness and cold temperatures away from the vents.
Cassini also investigated the plumes of Enceladus – huge “geysers” of water vapor erupting through cracks in the surface at the south pole of Enceladus. Cassini flew right through some of them, analyzing their composition, and found they contain water vapor, ice particles, complex organic molecules and salts. Cassini wasn’t capable of finding life directly, but it did find valuable clues and hints that there may well be something alive in that alien ocean, even if only microbes.
The geysers of Enceladus: huge plumes of water vapor erupt through cracks in the icy surface at the south pole. Cassini analyzed them and found they contain water vapor, ice particles, complex organic molecules, salts and methane. Image via NASA/JPL-Caltech/SSI.
Earlier this year, New Scientistalso reported that there may already be some tentative evidence for microbes in Enceladus’s ocean. Cassini detected traces of methane in the water vapor plumes, and when scientists tested computer models of conditions in the ocean, they found that microbes that emit methane after combining hydrogen and carbon dioxide – called methanogens – could easily survive there. According to Chris McKay at NASA’s Ames Research Center in Moffett Field, California:
This [team] has taken the first step to showing experimentally that methanogens can indeed live in the conditions expected on Enceladus.
The scientists found that the microbes were able to thrive at temperatures and pressures likely found in Enceladus’s oceans, ranging from 0 to 90 degrees Celsius (32 to 194 Fahrenheit), and up to 50 Earth atmospheres. They also found that olivine minerals, thought to exist in the Saturnian moon’s core, could be chemically broken down to produce enough hydrogen for methanogens to thrive.
Another proposed return mission to Enceladus is the Enceladus Life Finder (ELF), which would orbit Saturn and make repeated passes through the plumes – like Cassini, but with updated instruments. Image via Jonathan Lunine.
Another proposed return mission to Enceladus is the Enceladus Life Finder (ELF), which would orbit Saturn and make repeated passes through the plumes – like Cassini, but with updated instruments that could even test whether any amino acids found have predominately left- or right-handed structures. (Life on Earth predominately creates left-handed forms, and scientists think that life elsewhere will also favor one form over the other instead of a random mixture as would occur from abiotic chemistry.)
Cassini wasn’t designed to detect life directly, but on a future mission – such as the one proposed – a mass spectrometer would be able to detect carbon isotope ratios unique to living organisms, as well as other potential “biomarkers” of methanogens, including lipids and hydrocarbons.
Saturn’s ocean moon Enceladus as seen by the Cassini spacecraft. Billionaire Yuri Milner wants to send a mission back there to search for life. Image via NASA/JPL-Caltech/SSI.
Bottom line: Scientists are eager to return to Enceladus to learn more about its intriguing subsurface ocean. The new plan by billionaire Yuri Milner, with NASA’s assistance, may be the best bet to go back and see if anything is swimming in those mysterious alien waters.
Cassini spacecraft image from 2010 of Saturn’s moon Enceladus. The moon is backlit, with its dark outline crowned by glowing jets from the south polar region. Notice that there are several separate jets, or sets of jets, emanating from the fissures known to scientists as “tiger stripes.” Image via NASA/JPL/Space Science Institute.
Saturn’s moon Enceladus is very small – only about 310 miles (500 kilometers) across – but it may hold clues to one of the biggest mysteries of all time – are we alone? Beneath the icy crust lies a global salty ocean, not too different from Earth’s oceans. Could that ocean contain life of some kind? That is a question that many scientists – and the public alike – would like to find an answer for. Enceladus, however, is very far away and planetary missions are expensive – but there may be an ideal solution.
Billionaire entrepreneur and physicist Yuri Milner wants to send a private mission back to this intriguing world, and NASA wants to help him. This incredible idea was first reported in New Scientist on November 8, 2018 (please note this article is behind a paywall). It was then reported by Gizmodo the same day.
Agreements signed by NASA and Milner’s non-profit Breakthrough Starshot foundation in September show that the organizations are working on scientific, technical and financial plans for the ambitious mission. NASA has committed over $70,000 to help produce a concept study for a flyby mission. The funds won’t be paid to Breakthrough but represent the agency’s own staffing costs on the project.
Enceladus is a very small moon, but it has a global ocean beneath its icy crust. Image via NASA/JPL-Caltech.
Breakthrough Initiatives, part of Milner’s non-profit Breakthrough Starshot Foundation, would lead and pay for the mission, with consultation from NASA. The board of Breakthrough Initiatives includes billionaires Yuri Milner and Mark Zuckerberg, and the late physicist Stephen Hawking. Breakthrough Initiatives has been studying various mission concepts for space exploration, including a solar sail to nearby stars, advancing the technology to discover other Earth-like planets and sending out a direct message, similar to the previous Arecibo message, specifically to try and catch the attention of aliens.
Enceladus has become a prime target in the search for extraterrestrial life in our solar system, since its subsurface ocean is thought to be quite similar to oceans on Earth, thanks to data from the Cassini mission, which orbited Saturn from 2004 until September 2017. Scientists already know it is salty and there is evidence for geothermal activity on the ocean floor, similar to “smoker” volcanic vents on the bottom of oceans on Earth. Such geothermal vents – at least on Earth – are oases for a wide variety of ocean life despite the darkness and cold temperatures away from the vents.
Cassini also investigated the plumes of Enceladus – huge “geysers” of water vapor erupting through cracks in the surface at the south pole of Enceladus. Cassini flew right through some of them, analyzing their composition, and found they contain water vapor, ice particles, complex organic molecules and salts. Cassini wasn’t capable of finding life directly, but it did find valuable clues and hints that there may well be something alive in that alien ocean, even if only microbes.
The geysers of Enceladus: huge plumes of water vapor erupt through cracks in the icy surface at the south pole. Cassini analyzed them and found they contain water vapor, ice particles, complex organic molecules, salts and methane. Image via NASA/JPL-Caltech/SSI.
Earlier this year, New Scientistalso reported that there may already be some tentative evidence for microbes in Enceladus’s ocean. Cassini detected traces of methane in the water vapor plumes, and when scientists tested computer models of conditions in the ocean, they found that microbes that emit methane after combining hydrogen and carbon dioxide – called methanogens – could easily survive there. According to Chris McKay at NASA’s Ames Research Center in Moffett Field, California:
This [team] has taken the first step to showing experimentally that methanogens can indeed live in the conditions expected on Enceladus.
The scientists found that the microbes were able to thrive at temperatures and pressures likely found in Enceladus’s oceans, ranging from 0 to 90 degrees Celsius (32 to 194 Fahrenheit), and up to 50 Earth atmospheres. They also found that olivine minerals, thought to exist in the Saturnian moon’s core, could be chemically broken down to produce enough hydrogen for methanogens to thrive.
Another proposed return mission to Enceladus is the Enceladus Life Finder (ELF), which would orbit Saturn and make repeated passes through the plumes – like Cassini, but with updated instruments. Image via Jonathan Lunine.
Another proposed return mission to Enceladus is the Enceladus Life Finder (ELF), which would orbit Saturn and make repeated passes through the plumes – like Cassini, but with updated instruments that could even test whether any amino acids found have predominately left- or right-handed structures. (Life on Earth predominately creates left-handed forms, and scientists think that life elsewhere will also favor one form over the other instead of a random mixture as would occur from abiotic chemistry.)
Cassini wasn’t designed to detect life directly, but on a future mission – such as the one proposed – a mass spectrometer would be able to detect carbon isotope ratios unique to living organisms, as well as other potential “biomarkers” of methanogens, including lipids and hydrocarbons.
Saturn’s ocean moon Enceladus as seen by the Cassini spacecraft. Billionaire Yuri Milner wants to send a mission back there to search for life. Image via NASA/JPL-Caltech/SSI.
Bottom line: Scientists are eager to return to Enceladus to learn more about its intriguing subsurface ocean. The new plan by billionaire Yuri Milner, with NASA’s assistance, may be the best bet to go back and see if anything is swimming in those mysterious alien waters.
Brett Joseph captured Venus in the east, very near the sunrise point, on October 31, 2018, less than a week after the planet passed between us and the sun and thereby entered the morning sky. Why could he see Venus so near the sunrise? Because Venus is very bright!
Jupiter is a bright planet, and Mars was also exceedingly bright for a couple of months, centered on late July, 2018. But neither Jupiter nor Mars at its brightest can outshine Venus.
Our neighboring world – orbiting one step inward from Earth around the sun – is the third-brightest object in the sky, after the sun and moon. In late November and early December, 2018, Venus is easily visible in the east before sunup. It’s at its brightest around this time for this entire morning apparition, which extends into 2019.
Why is this world so bright?
Larry Estes in North Richland Hills, Texas caught this image of Venus with a Samsung Galaxy S9 phone on November 13, 2018. He wrote: “Went out for star shots and Venus was so bright that I thought it was a plane coming, at first. When sunrise came it took this shot from the top of my car. Could lie and say it was a calm body of water, but it is the reflection onto the top of my car.”
As the planet next-inward from Earth in orbit around the sun, Venus is relatively nearby. But its nearness isn’t the only reason Venus is bright. Consider that Mars orbits one step outward from Earth. And Mars waxes and wanes in brightness in our sky. It’s only exceptionally bright around the time Earth passes between Mars and the sun, when the Red Planet is at its closest to us, which it was earlier this year, around late July.
With Venus, something else is going on. Astronomers use the term albedo to describe how bright a planet is in absolute terms. When sunlight strikes a planet, some of the light is absorbed by the planet’s surface or atmosphere – and some is reflected. Albedo is a comparison between how much light strikes an object – and how much is reflected.
As you might have guessed, Venus has the highest albedo of any major planet in our solar system.
Throughout November of 2018, Venus has been near a bright star, Spica in the constellation Virgo. Spica is one of the brightest stars in our sky but it’s nowhere near as bright as Venus! A. Kannan caught Venus and Spica on November 13, 2018 and wrote: “The planet Venus and Star Spica shines brightly at dawn before sunrise in Singapore. The pair looks so beautiful in the dark sky.”
The albedo of Venus is close to .7, meaning it reflects about 70 percent of the sunlight striking it. When the moon is close to full in Earth’s sky, it can look a lot brighter than Venus, but the moon reflects only about 10 percent of the light that hits it. The moon’s low albedo is due to the fact that our companion world is made of dark volcanic rock. It appears bright to us only because of its nearness to Earth. It’s only about a light-second away, in contrast for several light-minutes for Venus.
Venus is bright (it has a high albedo) because it’s blanketed by highly reflective clouds. The clouds in the atmosphere of Venus contain droplets of sulfuric acid, as well as acidic crystals suspended in a mixture of gases. Light bounces easily off the smooth surfaces of these spheres and crystals. Sunlight bouncing from these clouds is a big part of the reason that Venus is so bright.
By the way, Venus isn’t the most reflective body in our solar system. That honor goes to Enceladus, a moon of Saturn. Its icy surface reflects some 90% of the sunlight striking it.
Since Venus passed between us and the sun in late October, 2018, its lighted half – or day side – is still facing mostly away. It’s an interesting fact that this crescent Venus can appear brighter than the fuller Venus we see at other times. Read more about why. This crescent Venus was captured by Prabhakaran A on Novermber 20, 2018, from Mleiha, UAE. Equipment: Edge HD 11″ Alt Az – Explore Scientific 3x Extender – ZWO 290MC. Postprocessing: stacked 9000 frames in AS!3 and processed in Registax.
We mentioned above that Mars is brightest when Earth passes between the Red Planet and the sun. At such times, Mars is closest to us, and so it appears brightest in our sky. A similar situation occurs for Venus: the planet is brightest in our sky around the time Venus passes between us and the sun, although not exactly at that time.
Because Venus orbits the sun inside Earth’s orbit, when it goes between us and the sun its lighted hemisphere, or day side, is facing away from us. At such times, it’s difficult or impossible to see Venus at all.
Because it’s an inner planet, as Venus approaches its time of passing between the Earth and sun, we see the planet exhibit phases, like a tiny moon. As Venus draws up behind Earth in orbit – and prepares to “lap” us in the race of the planets – observers on Earth can watch as the phase of Venus wanes. Meanwhile, as the crescent Venus in waning in phase, the overall size of the disk of Venus gets larger in Earth’s sky, as Venus draws closer to us and prepares to go between us and the sun.
Venus is brightest when those two factors combine – waning crescent, plus largest overall size of Venus’ disk – so that the greatest amount of surface area of Venus shows in our sky. Astronomers call this greatest illuminated extent.
In 2018, Venus reached greatest illuminated extent in the evening sky on September 21. It’ll reach greatest illuminated extent in the morning sky on December 1 or 2, 2018, depending on your time zone.
Venus is brightest at what’s called greatest illuminated extent, or greatest brilliancy. It happens when Venus is relatively near Earth, and when telescopes show it in a crescent phase, like a tiny crescent moon. At such times, you can see Venus in the daytime. Read more about how. Here’s a telescopic view of a crescent Venus (l) and the moon, in daytime, via NASA.
Bottom line: Venus is the third-brightest object in the sky, after the sun and moon. That’s partly because sunlight is easily reflected by acidic clouds in the atmosphere of Venus.
from EarthSky https://ift.tt/2FI7d5P
Brett Joseph captured Venus in the east, very near the sunrise point, on October 31, 2018, less than a week after the planet passed between us and the sun and thereby entered the morning sky. Why could he see Venus so near the sunrise? Because Venus is very bright!
Jupiter is a bright planet, and Mars was also exceedingly bright for a couple of months, centered on late July, 2018. But neither Jupiter nor Mars at its brightest can outshine Venus.
Our neighboring world – orbiting one step inward from Earth around the sun – is the third-brightest object in the sky, after the sun and moon. In late November and early December, 2018, Venus is easily visible in the east before sunup. It’s at its brightest around this time for this entire morning apparition, which extends into 2019.
Why is this world so bright?
Larry Estes in North Richland Hills, Texas caught this image of Venus with a Samsung Galaxy S9 phone on November 13, 2018. He wrote: “Went out for star shots and Venus was so bright that I thought it was a plane coming, at first. When sunrise came it took this shot from the top of my car. Could lie and say it was a calm body of water, but it is the reflection onto the top of my car.”
As the planet next-inward from Earth in orbit around the sun, Venus is relatively nearby. But its nearness isn’t the only reason Venus is bright. Consider that Mars orbits one step outward from Earth. And Mars waxes and wanes in brightness in our sky. It’s only exceptionally bright around the time Earth passes between Mars and the sun, when the Red Planet is at its closest to us, which it was earlier this year, around late July.
With Venus, something else is going on. Astronomers use the term albedo to describe how bright a planet is in absolute terms. When sunlight strikes a planet, some of the light is absorbed by the planet’s surface or atmosphere – and some is reflected. Albedo is a comparison between how much light strikes an object – and how much is reflected.
As you might have guessed, Venus has the highest albedo of any major planet in our solar system.
Throughout November of 2018, Venus has been near a bright star, Spica in the constellation Virgo. Spica is one of the brightest stars in our sky but it’s nowhere near as bright as Venus! A. Kannan caught Venus and Spica on November 13, 2018 and wrote: “The planet Venus and Star Spica shines brightly at dawn before sunrise in Singapore. The pair looks so beautiful in the dark sky.”
The albedo of Venus is close to .7, meaning it reflects about 70 percent of the sunlight striking it. When the moon is close to full in Earth’s sky, it can look a lot brighter than Venus, but the moon reflects only about 10 percent of the light that hits it. The moon’s low albedo is due to the fact that our companion world is made of dark volcanic rock. It appears bright to us only because of its nearness to Earth. It’s only about a light-second away, in contrast for several light-minutes for Venus.
Venus is bright (it has a high albedo) because it’s blanketed by highly reflective clouds. The clouds in the atmosphere of Venus contain droplets of sulfuric acid, as well as acidic crystals suspended in a mixture of gases. Light bounces easily off the smooth surfaces of these spheres and crystals. Sunlight bouncing from these clouds is a big part of the reason that Venus is so bright.
By the way, Venus isn’t the most reflective body in our solar system. That honor goes to Enceladus, a moon of Saturn. Its icy surface reflects some 90% of the sunlight striking it.
Since Venus passed between us and the sun in late October, 2018, its lighted half – or day side – is still facing mostly away. It’s an interesting fact that this crescent Venus can appear brighter than the fuller Venus we see at other times. Read more about why. This crescent Venus was captured by Prabhakaran A on Novermber 20, 2018, from Mleiha, UAE. Equipment: Edge HD 11″ Alt Az – Explore Scientific 3x Extender – ZWO 290MC. Postprocessing: stacked 9000 frames in AS!3 and processed in Registax.
We mentioned above that Mars is brightest when Earth passes between the Red Planet and the sun. At such times, Mars is closest to us, and so it appears brightest in our sky. A similar situation occurs for Venus: the planet is brightest in our sky around the time Venus passes between us and the sun, although not exactly at that time.
Because Venus orbits the sun inside Earth’s orbit, when it goes between us and the sun its lighted hemisphere, or day side, is facing away from us. At such times, it’s difficult or impossible to see Venus at all.
Because it’s an inner planet, as Venus approaches its time of passing between the Earth and sun, we see the planet exhibit phases, like a tiny moon. As Venus draws up behind Earth in orbit – and prepares to “lap” us in the race of the planets – observers on Earth can watch as the phase of Venus wanes. Meanwhile, as the crescent Venus in waning in phase, the overall size of the disk of Venus gets larger in Earth’s sky, as Venus draws closer to us and prepares to go between us and the sun.
Venus is brightest when those two factors combine – waning crescent, plus largest overall size of Venus’ disk – so that the greatest amount of surface area of Venus shows in our sky. Astronomers call this greatest illuminated extent.
In 2018, Venus reached greatest illuminated extent in the evening sky on September 21. It’ll reach greatest illuminated extent in the morning sky on December 1 or 2, 2018, depending on your time zone.
Venus is brightest at what’s called greatest illuminated extent, or greatest brilliancy. It happens when Venus is relatively near Earth, and when telescopes show it in a crescent phase, like a tiny crescent moon. At such times, you can see Venus in the daytime. Read more about how. Here’s a telescopic view of a crescent Venus (l) and the moon, in daytime, via NASA.
Bottom line: Venus is the third-brightest object in the sky, after the sun and moon. That’s partly because sunlight is easily reflected by acidic clouds in the atmosphere of Venus.
Beautiful telescopic image of comet 46P/Wirtanen, taken November 4, 2018, with an 11-inch telescope by Martin Mobberley. The image shows the development of a gas tail for the comet. Used with permission.
Have you heard about comet 46P/Wirtanen? It’s due to pass closest to our sun and Earth in December 2018. Comet Wirtanen is the brightest comet in the night sky now, visible not with the eye alone, but to astronomers with telescopes and binoculars. In December 2018, comet Wirtanen might indeed become visible to the eye, at least from dark locations. Wirtanen’s closest approach to the sun will be December 12, 2018, and its closest approach to Earth is just a few days later, on December 16. You’ll find some charts, and info on how to see it, below.
As of late November, observers around the world are reporting that Comet 46P/Wirtanen is showing a brightness or visual magnitude between 5.5 to 6.5. That is on the cusp of visibility to the eye, in theory. However, the dim light reflected from comet Wirtanen is spread over a large cometary atmosphere.
This may mean that – as December arrives, the month in which the comet should look brightest from Earth – Wirtanen may look more diffuse and harder to see than expected. As the comet may not be easily visible for casual observers, a good option would be to verify if your local astronomy club will be hosting events for observing comet 46P/Wirtanen.
Also, in November 2018, astronomers reported capturing a new image of comet Wirtanen, showing gas spirals as the comet rotates. See the image.
Pablo Goffard in Valle del Elqui, Coquimbo, Chile captured Comet Wirtanen on November 7, 2018. 130 mm Newton Telescope, Canon T3.
Comet Wirtanen on December 8, 2018, shortly after nightfall. Illustration by Eddie Irizarry using Stellarium.
How close will comet Wirtanen come?
According to astronomers at the University of Maryland, this passage of comet Wirtanen near the Earth (near by comet standards, that is) will be the 10th closest approach of a comet in modern times.
At its closest to us, the comet will be about 30 times the moon’s distance (7.1 million miles, or 11.5 million km).
The record for the closest observed comet – for all of recorded history – goes to D/1770 L1 Lexell, which came at less than 6 times the Earth-moon distance in June, 1770.
Or, contrast Wirtanen’s closest appraoch – 30 times the moon’s distance, 7.1 million miles, or 11.5 million km – to another comet that swept relatively near us recently, 21P/Giacobini-Zinner, causing a brief outburst in this year’s Draconid meteor shower. Giacobini-Zinner swept closest to Earth on September 9-10, 2018, at 36 million miles (58 million km). That was the closest Giacobini-Zinner had come in 72 years!
So you see comets are elusive objects. They don’t come very close, usually, in any absolute sense. Still, this 2018 approach is a good one for comet Wirtanen. To understand why, you have to think of the comet, and Earth, in their orbits.
Comet Wirtanen belongs to the Jupiter family of comets. Its orbit brings the comet just outside of Earth’s orbit, to just inside of Jupiter’s path around the sun. Although it orbits our sun every 5.4 years, the 2018 pass is its closest since its discovery some 70 years ago by American astronomer Carl A. Wirtanen on January 17, 1948.
Since its discovery, the comet has approached Earth’s orbit a dozen times. However, as it happens, each time it swept in near our planet’s orbit, Earth was on the far side of the orbit, as seen in the following illustration:
A close approach of a comet depends in part on where the comet is, and in part on where Earth is, when the 2 bodies sweep closest. This illustration shows the approach of comet Wirtanen to Earth’s orbit in July, 2013. At that time, Earth was on the other side of its orbit from the comet, so the approach was not particularly close. Image via astro.vanbuitenen.nl.
Not so in 2018. At the 2018 encounter, the comet and Earth will be on the same side of Earth’s orbit, when the closest approach occurs:
The 2018 approach of comet 46P/Wirtanen is the comet’s closest since its discovery in 1948. Image via astro.vanbuitenen.nl.
How bright will the comet get? No one knows for certain. Comets are unpredictable by their nature. Estimates indicate Wirtanen might reach a visual magnitude of 3.5 to 6. That would place the comet clearly in the realm of visibility with the unaided eye (although diffuse objects like comets are tougher to see than the pinpoints of stars at comparable magnitudes).
The image below provides a mixture of observations so far – and predictions – for the brightness of comet Wirtanen when closest to Earth in December, 2018:
This is what’s called a lightcurve. It’s a measurement of comet 46P/Wirtanen’s brightness over time. Lightcurve (colored dots) compiled from observations reported to the Minor Planet Center1 (solid circles) and the Comet Observer’s Database2 (open circles). Predicted magnitudes are current estimates from sources using different techniques, and have a wide variability. For more information about these predictions, see the Wirtanen brightness discussion. Image via University of Maryland’s comet 46P/Wirtanen: current status page.
How can you see comet Wirtanen?
And, most importantly, will this comet be visible with the unaided eye? Some observers are already glimpsing the celestial visitor using binoculars. In early November, Wirtanen had a visual magnitude of 8, making it the brightest comet in our skies for the moment, but still not visible to the unaided eye.
By mid December, 46P/Wirtanen might reach a magnitude of 3.5 to 6, perhaps visible to the unaided eye as a faint, diffuse object from dark skies.
In December, binoculars and small telescopes should show a diffuse cometary atmosphere, which might appear considerably large for an object whose icy cometary nucleus, or core, is less than a mile (just 1.2 km) wide.
Will the comet show a tail? Due to the orientation in space of Earth and Wirtanen when the comet is closest, the ion tail will be behind the comet, not visible from Earth’s perspective. If 46P/Wirtanen develops a slight curved tail in the coming weeks, it should be barely detectable, easier to see in astrophotography than with the unaided eye.
Again – always – expect to get the best views and contrast through binoculars or a telescope, in a dark sky location, far from city lights.
No telescope or binoculars? Consider watching the comet online. On December 12 and 17, 2018 (around the closest approach of the comet to the sun and Earth), the Virtual Telescope Project will be showing comet Wirtanen live, online, for free. Click here for more information, and check out their poster for this event, below:
Comet Wirtanen via Tel Lekatsas, from Ma Ma Creek, Australia. Used with permission.
So comet 46P/Wirtanen might – or might not – meet your expectations. As always, if you take the time to watch it over some weeks, you’ll appreciate it more. There are some nice details here to appreciate.
For example, as you gaze at the comet, realize that its cometary atmosphere – or coma – is bigger, in an absolute sense, than the planet Jupiter.
As for how big the coma will appear in our sky … some estimates suggest it might be as big as the apparent diameter of the moon! Maybe even bigger. Since the outer area of this dim coma will be the faintest, astrophotography will be the best way of detecting how big it really is, especially by mid December.
Also, if you have optical aid, you might be able to discern this comet’s movement in front of the stars. In early November, the comet was approaching Earth at 21,251 miles per hour (34,200 km/h), or 9.5 km/s. By December, as the comet gets closer to us, Wirtanen will appear to gain speed. Careful observations of the comet – in particular with a small telescope – should let you perceive its motion relative to the stars, over about a 30-minute period.
Location of comet 46P/Wirtanen on December 1, 2018, as seen from central U.S. around 9 p.m., facing south. Illustration by Eddie Irizarry using Stellarium.
On December 8, 2018, comet 46P/Wirtanen should be easier to locate. Note that stars Saiph and Rigel (on the right side of Orion) point to the comet. Also, the celestial visitor should be slightly brighter by then. This view shows the sky as seen from central U.S. shortly after nightfall on December 8, facing southeast. Illustration by Eddie Irizarry using Stellarium.
The night of December 15, 2018, may provide your best views of comet 46P/Wirtanen. First, look at the familiar stars of Orion, then look up to the stars that compose the Pleiades cluster in Taurus. By mid December, the comet is located very close to this easy-to-find group of stars. Facing east, shortly after nightfall. Illustration by Eddie Irizarry using Stellarium.
And there is more…
By early December, sky enthusiasts observing comet 46P/Wirtanen with telescopes will occasionally see one or more slow-moving objects entering the same field of view as the comet. These objects will appear so slow, that they will look like asteroids. However, these are not space rocks. They are human-made satellites.
Between December 6 and 12, 2018, comet 46P/Wirtanen enters an area of the sky where, as seen from our perspective, there is an orbiting ring of some 450 active geostationary satellites.
The belt of meteorological, television and other communication satellites orbit our planet at about 22,236 miles (35,786 km) above Earth’s equator. As these satellites orbit our planet at the same speed that Earth rotates, geostationary satellites appear to be motionless, at a fixed position in the sky, thus explaining why the small satellite dishes on the roof of our houses are pointing at a fixed position.
Because they orbit so high above Earth, these satellites are illuminated by the sun most of the time.
Observers using telescopes with a small motor that tracks astronomical objects in the sky, compensating for the Earths’ rotation, will perceive the slow motion of these satellites passing in front of the comet and stars. The view will be similar to the one seen on this video:
If the object appears to cross the field of view in the telescope fairly fast, you are likely looking at a satellite in low-Earth orbit. But if the satellite is moving slowly and remains visible several seconds through the telescope, you are probably seeing one of many geostationary satellites that will be visible in the path of comet Wirtanen from early to mid-December.
Sometimes, geostationary satellites may be visible in groups of 3 or more.
The line that crosses from east to west is the celestial equator as seen from the Northern Hemisphere. From our perspective, comet Wirtanen appears to enter the belt of geostationary satellites between December 6 to 12. If you are looking from a location north of the equator, then there is a slight perspective difference or parallax of objects in space, so these satellites are seen slightly south of the celestial equator, as seen from the U.S.
Can you confirm you are looking at a geostationary satellite at the eyepiece? Yes. If you are a using a computerized or tracking telescope, center the slow-moving object in the field of view. Then turn off the telescope or tracking function. If it’s a geostationary satellite, it will remain centered and now all the stars will appear to slowly drift as Earth rotates.
Keep in mind that you might have to re-align the telescope to continue observing the comet or other astronomical objects. Have fun!
The December 16, 2018, close approach to Earth of comet Wirtanen will happen less than 4 days after the comet’s perihelion, or closest point to the sun. Because comets are increasingly active as they draw nearer the sun that binds them in orbit, this comet can be expected to be near its brightest around then. It might be visible to the eye from a dark location. Image via University of Maryland.
Bottom line: Comet Wirtanen will come closest to Earth in December. Comets are unpredictable, but it seems this one might at least offer good binocular views, and it’ll possibly be visible to the eye. Will it be more interesting than just a diffuse coma ball? Let’s see what’s in store for us!
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Beautiful telescopic image of comet 46P/Wirtanen, taken November 4, 2018, with an 11-inch telescope by Martin Mobberley. The image shows the development of a gas tail for the comet. Used with permission.
Have you heard about comet 46P/Wirtanen? It’s due to pass closest to our sun and Earth in December 2018. Comet Wirtanen is the brightest comet in the night sky now, visible not with the eye alone, but to astronomers with telescopes and binoculars. In December 2018, comet Wirtanen might indeed become visible to the eye, at least from dark locations. Wirtanen’s closest approach to the sun will be December 12, 2018, and its closest approach to Earth is just a few days later, on December 16. You’ll find some charts, and info on how to see it, below.
As of late November, observers around the world are reporting that Comet 46P/Wirtanen is showing a brightness or visual magnitude between 5.5 to 6.5. That is on the cusp of visibility to the eye, in theory. However, the dim light reflected from comet Wirtanen is spread over a large cometary atmosphere.
This may mean that – as December arrives, the month in which the comet should look brightest from Earth – Wirtanen may look more diffuse and harder to see than expected. As the comet may not be easily visible for casual observers, a good option would be to verify if your local astronomy club will be hosting events for observing comet 46P/Wirtanen.
Also, in November 2018, astronomers reported capturing a new image of comet Wirtanen, showing gas spirals as the comet rotates. See the image.
Pablo Goffard in Valle del Elqui, Coquimbo, Chile captured Comet Wirtanen on November 7, 2018. 130 mm Newton Telescope, Canon T3.
Comet Wirtanen on December 8, 2018, shortly after nightfall. Illustration by Eddie Irizarry using Stellarium.
How close will comet Wirtanen come?
According to astronomers at the University of Maryland, this passage of comet Wirtanen near the Earth (near by comet standards, that is) will be the 10th closest approach of a comet in modern times.
At its closest to us, the comet will be about 30 times the moon’s distance (7.1 million miles, or 11.5 million km).
The record for the closest observed comet – for all of recorded history – goes to D/1770 L1 Lexell, which came at less than 6 times the Earth-moon distance in June, 1770.
Or, contrast Wirtanen’s closest appraoch – 30 times the moon’s distance, 7.1 million miles, or 11.5 million km – to another comet that swept relatively near us recently, 21P/Giacobini-Zinner, causing a brief outburst in this year’s Draconid meteor shower. Giacobini-Zinner swept closest to Earth on September 9-10, 2018, at 36 million miles (58 million km). That was the closest Giacobini-Zinner had come in 72 years!
So you see comets are elusive objects. They don’t come very close, usually, in any absolute sense. Still, this 2018 approach is a good one for comet Wirtanen. To understand why, you have to think of the comet, and Earth, in their orbits.
Comet Wirtanen belongs to the Jupiter family of comets. Its orbit brings the comet just outside of Earth’s orbit, to just inside of Jupiter’s path around the sun. Although it orbits our sun every 5.4 years, the 2018 pass is its closest since its discovery some 70 years ago by American astronomer Carl A. Wirtanen on January 17, 1948.
Since its discovery, the comet has approached Earth’s orbit a dozen times. However, as it happens, each time it swept in near our planet’s orbit, Earth was on the far side of the orbit, as seen in the following illustration:
A close approach of a comet depends in part on where the comet is, and in part on where Earth is, when the 2 bodies sweep closest. This illustration shows the approach of comet Wirtanen to Earth’s orbit in July, 2013. At that time, Earth was on the other side of its orbit from the comet, so the approach was not particularly close. Image via astro.vanbuitenen.nl.
Not so in 2018. At the 2018 encounter, the comet and Earth will be on the same side of Earth’s orbit, when the closest approach occurs:
The 2018 approach of comet 46P/Wirtanen is the comet’s closest since its discovery in 1948. Image via astro.vanbuitenen.nl.
How bright will the comet get? No one knows for certain. Comets are unpredictable by their nature. Estimates indicate Wirtanen might reach a visual magnitude of 3.5 to 6. That would place the comet clearly in the realm of visibility with the unaided eye (although diffuse objects like comets are tougher to see than the pinpoints of stars at comparable magnitudes).
The image below provides a mixture of observations so far – and predictions – for the brightness of comet Wirtanen when closest to Earth in December, 2018:
This is what’s called a lightcurve. It’s a measurement of comet 46P/Wirtanen’s brightness over time. Lightcurve (colored dots) compiled from observations reported to the Minor Planet Center1 (solid circles) and the Comet Observer’s Database2 (open circles). Predicted magnitudes are current estimates from sources using different techniques, and have a wide variability. For more information about these predictions, see the Wirtanen brightness discussion. Image via University of Maryland’s comet 46P/Wirtanen: current status page.
How can you see comet Wirtanen?
And, most importantly, will this comet be visible with the unaided eye? Some observers are already glimpsing the celestial visitor using binoculars. In early November, Wirtanen had a visual magnitude of 8, making it the brightest comet in our skies for the moment, but still not visible to the unaided eye.
By mid December, 46P/Wirtanen might reach a magnitude of 3.5 to 6, perhaps visible to the unaided eye as a faint, diffuse object from dark skies.
In December, binoculars and small telescopes should show a diffuse cometary atmosphere, which might appear considerably large for an object whose icy cometary nucleus, or core, is less than a mile (just 1.2 km) wide.
Will the comet show a tail? Due to the orientation in space of Earth and Wirtanen when the comet is closest, the ion tail will be behind the comet, not visible from Earth’s perspective. If 46P/Wirtanen develops a slight curved tail in the coming weeks, it should be barely detectable, easier to see in astrophotography than with the unaided eye.
Again – always – expect to get the best views and contrast through binoculars or a telescope, in a dark sky location, far from city lights.
No telescope or binoculars? Consider watching the comet online. On December 12 and 17, 2018 (around the closest approach of the comet to the sun and Earth), the Virtual Telescope Project will be showing comet Wirtanen live, online, for free. Click here for more information, and check out their poster for this event, below:
Comet Wirtanen via Tel Lekatsas, from Ma Ma Creek, Australia. Used with permission.
So comet 46P/Wirtanen might – or might not – meet your expectations. As always, if you take the time to watch it over some weeks, you’ll appreciate it more. There are some nice details here to appreciate.
For example, as you gaze at the comet, realize that its cometary atmosphere – or coma – is bigger, in an absolute sense, than the planet Jupiter.
As for how big the coma will appear in our sky … some estimates suggest it might be as big as the apparent diameter of the moon! Maybe even bigger. Since the outer area of this dim coma will be the faintest, astrophotography will be the best way of detecting how big it really is, especially by mid December.
Also, if you have optical aid, you might be able to discern this comet’s movement in front of the stars. In early November, the comet was approaching Earth at 21,251 miles per hour (34,200 km/h), or 9.5 km/s. By December, as the comet gets closer to us, Wirtanen will appear to gain speed. Careful observations of the comet – in particular with a small telescope – should let you perceive its motion relative to the stars, over about a 30-minute period.
Location of comet 46P/Wirtanen on December 1, 2018, as seen from central U.S. around 9 p.m., facing south. Illustration by Eddie Irizarry using Stellarium.
On December 8, 2018, comet 46P/Wirtanen should be easier to locate. Note that stars Saiph and Rigel (on the right side of Orion) point to the comet. Also, the celestial visitor should be slightly brighter by then. This view shows the sky as seen from central U.S. shortly after nightfall on December 8, facing southeast. Illustration by Eddie Irizarry using Stellarium.
The night of December 15, 2018, may provide your best views of comet 46P/Wirtanen. First, look at the familiar stars of Orion, then look up to the stars that compose the Pleiades cluster in Taurus. By mid December, the comet is located very close to this easy-to-find group of stars. Facing east, shortly after nightfall. Illustration by Eddie Irizarry using Stellarium.
And there is more…
By early December, sky enthusiasts observing comet 46P/Wirtanen with telescopes will occasionally see one or more slow-moving objects entering the same field of view as the comet. These objects will appear so slow, that they will look like asteroids. However, these are not space rocks. They are human-made satellites.
Between December 6 and 12, 2018, comet 46P/Wirtanen enters an area of the sky where, as seen from our perspective, there is an orbiting ring of some 450 active geostationary satellites.
The belt of meteorological, television and other communication satellites orbit our planet at about 22,236 miles (35,786 km) above Earth’s equator. As these satellites orbit our planet at the same speed that Earth rotates, geostationary satellites appear to be motionless, at a fixed position in the sky, thus explaining why the small satellite dishes on the roof of our houses are pointing at a fixed position.
Because they orbit so high above Earth, these satellites are illuminated by the sun most of the time.
Observers using telescopes with a small motor that tracks astronomical objects in the sky, compensating for the Earths’ rotation, will perceive the slow motion of these satellites passing in front of the comet and stars. The view will be similar to the one seen on this video:
If the object appears to cross the field of view in the telescope fairly fast, you are likely looking at a satellite in low-Earth orbit. But if the satellite is moving slowly and remains visible several seconds through the telescope, you are probably seeing one of many geostationary satellites that will be visible in the path of comet Wirtanen from early to mid-December.
Sometimes, geostationary satellites may be visible in groups of 3 or more.
The line that crosses from east to west is the celestial equator as seen from the Northern Hemisphere. From our perspective, comet Wirtanen appears to enter the belt of geostationary satellites between December 6 to 12. If you are looking from a location north of the equator, then there is a slight perspective difference or parallax of objects in space, so these satellites are seen slightly south of the celestial equator, as seen from the U.S.
Can you confirm you are looking at a geostationary satellite at the eyepiece? Yes. If you are a using a computerized or tracking telescope, center the slow-moving object in the field of view. Then turn off the telescope or tracking function. If it’s a geostationary satellite, it will remain centered and now all the stars will appear to slowly drift as Earth rotates.
Keep in mind that you might have to re-align the telescope to continue observing the comet or other astronomical objects. Have fun!
The December 16, 2018, close approach to Earth of comet Wirtanen will happen less than 4 days after the comet’s perihelion, or closest point to the sun. Because comets are increasingly active as they draw nearer the sun that binds them in orbit, this comet can be expected to be near its brightest around then. It might be visible to the eye from a dark location. Image via University of Maryland.
Bottom line: Comet Wirtanen will come closest to Earth in December. Comets are unpredictable, but it seems this one might at least offer good binocular views, and it’ll possibly be visible to the eye. Will it be more interesting than just a diffuse coma ball? Let’s see what’s in store for us!
Comet 46P/Wirtanen can be seen rotating in this new image from Farnham et al./ University of Maryland.
Using specialized filters to observe cyanogen gases produced by comet 46P/Wirtanen, astronomers were able to capture new images of the celestial visitor, showing gas spirals as the comet rotates. Astronomer Tony Farnham and colleagues reported these results via the Central Bureau for Astronomical Telegrams on November 10, 2018, and the image was also posted on University of Maryland’s current status page for Wirtanen on November 26.
These new observations suggest comet 46P/Wirtanen has a rotation period of 8.91 hours.
Will this comet become visible to the eye in December, as hoped? No one knows yet, and comets are known for being unpredictable. As of late November, observers around the world are reporting that Comet 46P/Wirtanen is showing a brightness or visual magnitude between 5.5 to 6.5. That is on the cusp of visibility to the eye, in theory.
However, the dim light reflected from comet Wirtanen is spread over a large cometary atmosphere.
This may mean that – as December arrives, the month in which the comet should look brightest from Earth – Wirtanen may look more diffuse and harder to see than expected. Like most comets, it will surely require truly dark skies to be seen. As the comet may not be easily visible for casual observers, a good option would be to verify if your local astronomy club will be hosting events for observing comet 46P/Wirtanen.
As is always best with comets, keep your expectations low. Still, comet 46P/Wirtanen might still provide nice views through binoculars and small telescopes, especially away from city lights.
Bottom line: Comet 46P/Wirtanen can be seen rotating in this new image from Farnham et al./ University of Maryland.
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Comet 46P/Wirtanen can be seen rotating in this new image from Farnham et al./ University of Maryland.
Using specialized filters to observe cyanogen gases produced by comet 46P/Wirtanen, astronomers were able to capture new images of the celestial visitor, showing gas spirals as the comet rotates. Astronomer Tony Farnham and colleagues reported these results via the Central Bureau for Astronomical Telegrams on November 10, 2018, and the image was also posted on University of Maryland’s current status page for Wirtanen on November 26.
These new observations suggest comet 46P/Wirtanen has a rotation period of 8.91 hours.
Will this comet become visible to the eye in December, as hoped? No one knows yet, and comets are known for being unpredictable. As of late November, observers around the world are reporting that Comet 46P/Wirtanen is showing a brightness or visual magnitude between 5.5 to 6.5. That is on the cusp of visibility to the eye, in theory.
However, the dim light reflected from comet Wirtanen is spread over a large cometary atmosphere.
This may mean that – as December arrives, the month in which the comet should look brightest from Earth – Wirtanen may look more diffuse and harder to see than expected. Like most comets, it will surely require truly dark skies to be seen. As the comet may not be easily visible for casual observers, a good option would be to verify if your local astronomy club will be hosting events for observing comet 46P/Wirtanen.
As is always best with comets, keep your expectations low. Still, comet 46P/Wirtanen might still provide nice views through binoculars and small telescopes, especially away from city lights.
In late November and early December, 2018, the dazzling planet Venus will be shining at greatest brilliancy in the morning sky. Venus is always the 3rd-brightest celestial object, after the sun and moon. Even so, Venus’ brightness now – at maximum – is some 2 1/2 times greater than Venus at minimum brightness.
Because Venus is an inferior planet – orbiting the sun inside Earth’s obit – this world shows the whole range of phases, much like Earth’s moon. Throughout the rest of 2018, you’ll need a telescope to view Venus as a waxing crescent world.
And, perhaps, it’ll surprise you that Venus shines most brightly when its disk is only about 25% illuminated by sunshine, as viewed from Earth.
Dennis Chabot of Posne NightSky Astrophotography caught Venus near the star Spica in the constellation Virgo on November 18, 2018. Thanks, Dennis!
Up before dawn? Then look for the bright stars Spica and Arcturus near Venus. These stars will disappear in the bright morning twilight, while brighter Venus shines on!
Venus’ disk will become 100% illuminated in sunshine some 8 1/2 months from now (August 14, 2019). But – at that time – Venus will be nearly 5 times farther from Earth than it is right now. Hence, the illuminated portion of Venus’ disk will actually cover less square area of sky – and Venus will be less bright – when seen as fully illuminated next August.
Thus you might see that greater brilliancy for Venus is a trade-off between the apparent size of the planet’s disk, and the extent to which we see the disk illuminated by sunlight. That’s why astronomers tend not to speak in terms of Venus’ greatest brilliancy. Instead, with more precision, they speak of the greatest illuminated extent of Venus.
This series of images – via Statis Kalyvis shows Venus through a telescope for a time in 2004. It starts with Venus far from Earth, albeit showing us most of its “day” side. As Venus swings closer to Earth in its smaller, faster orbit, its phase decreases, but its disk size enlarges. Read more about Venus’ phases.
Like many sky phenomena, the waxing and waning of Venus is cyclical and predictable. When Venus is in the evening sky, due to pass between the Earth and sun – as it did last on October 26, 2018 – the distance between Earth and Venus is decreasing. At the same time, we’re seeing less and less of the planet’s day side. Thus, before Venus enters the morning sky, Venus’ phase is shrinking, but its disk size is enlarging.
The converse is also true. After Venus has passed between us and the sun – and is fleeing ahead of us in orbit, as now – we find it in the morning sky, with the distance between our 2 worlds increasing. Now, Venus’ is in a waxing phase; we’re seeing more of its day side each day. But its disk size is diminishing because it’s rushing ahead of us in orbit.
This chart – via Guy Ottewell’s blog – shows Earth and Venus in November, 2018. The sight lines to the sun and outer planets are set for mid-November. The arrows show Venus and Earth traveling in orbit throughout the month.
Venus passed between us and the sun on October 26, 2018. So this world was closer to Earth over the last month or so, yet its phase was exceedingly thin. Throughout the most of November, the illuminated portion of Venus (the sliver we could see of its day side) covered less square area of sky than it does at present. On December 1 or 2, 2018 (depending upon your time zone), Venus will reach its greatest illuminated extent – that moment of trade-off when the illuminated portion of Venus’ disk (the part we see) will cover the maximum area in Earth’s sky.
At or near greatest illuminated extent, Venus always shines most brightly in Earth’s sky.
That is the case for Venus, now.
Venus just passed the point that astronomers call inferior conjunction. See bottom of diagram. When Venus is to the east (left) of the Earth-sun line, we see Venus as an evening “star” in the west after sunset. After Venus reaches its inferior conjunction, Venus then moves to the west (right) of the Earth-sun line, appearing as a morning “star” in the east before sunrise. Note that Earth and Venus orbit the sun counterclockwise, as seen from the north of the solar system plane.
So Venus last passed between the Earth and sun on October 26, 2018. Some 72 days after this inferior conjunction, Venus will reach its greatest elongation (that is its maximum angular separation from the sun) on January 6, 2019. At that point, Venus’ disk will be approximately 50% illuminated in sunshine.
At Venus’ last greatest eastern elongation on August 17, 2018, Venus reigned over the evening sky; and at the coming greatest western elongation – on January 6, 2019 – Venus will reign in the morning sky. In ancient times, the Greeks actually called Venus Hesperus when she dominated the evening sky and Phosphorus when she loomed over the morning sky. Did they know these two entities were really a single world? Some say yes, and some say no.
Midway between greatest eastern (evening) elongation and inferior conjunction, Venus’ disk is about 25% illuminated in sunshine and this is when Venus shines brightest in the evening sky.
Then, midway between inferior conjunction and greatest western (morning) elongation, Venus’ disk is again 25% illuminated in sunshine and this is when Venus beams most mightily in the morning sky.
Alice Cheung in Plymouth, U.K. wrote on November 20, 2018: “I got up and opened the curtains. It’s been a while since we had a clear sky, so I was surprised to see Venus shining so brightly!”
Bottom line: In late November and early December, Venus enjoys her glory days – her greatest brilliancy – in the morning sky. Look east before sunup! Greatest illuminated extent for Venus – when this world shows us the maximum amount of its bright, reflective surface – will come on December 1 or 2, 2018, depending upon your time zone.
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In late November and early December, 2018, the dazzling planet Venus will be shining at greatest brilliancy in the morning sky. Venus is always the 3rd-brightest celestial object, after the sun and moon. Even so, Venus’ brightness now – at maximum – is some 2 1/2 times greater than Venus at minimum brightness.
Because Venus is an inferior planet – orbiting the sun inside Earth’s obit – this world shows the whole range of phases, much like Earth’s moon. Throughout the rest of 2018, you’ll need a telescope to view Venus as a waxing crescent world.
And, perhaps, it’ll surprise you that Venus shines most brightly when its disk is only about 25% illuminated by sunshine, as viewed from Earth.
Dennis Chabot of Posne NightSky Astrophotography caught Venus near the star Spica in the constellation Virgo on November 18, 2018. Thanks, Dennis!
Up before dawn? Then look for the bright stars Spica and Arcturus near Venus. These stars will disappear in the bright morning twilight, while brighter Venus shines on!
Venus’ disk will become 100% illuminated in sunshine some 8 1/2 months from now (August 14, 2019). But – at that time – Venus will be nearly 5 times farther from Earth than it is right now. Hence, the illuminated portion of Venus’ disk will actually cover less square area of sky – and Venus will be less bright – when seen as fully illuminated next August.
Thus you might see that greater brilliancy for Venus is a trade-off between the apparent size of the planet’s disk, and the extent to which we see the disk illuminated by sunlight. That’s why astronomers tend not to speak in terms of Venus’ greatest brilliancy. Instead, with more precision, they speak of the greatest illuminated extent of Venus.
This series of images – via Statis Kalyvis shows Venus through a telescope for a time in 2004. It starts with Venus far from Earth, albeit showing us most of its “day” side. As Venus swings closer to Earth in its smaller, faster orbit, its phase decreases, but its disk size enlarges. Read more about Venus’ phases.
Like many sky phenomena, the waxing and waning of Venus is cyclical and predictable. When Venus is in the evening sky, due to pass between the Earth and sun – as it did last on October 26, 2018 – the distance between Earth and Venus is decreasing. At the same time, we’re seeing less and less of the planet’s day side. Thus, before Venus enters the morning sky, Venus’ phase is shrinking, but its disk size is enlarging.
The converse is also true. After Venus has passed between us and the sun – and is fleeing ahead of us in orbit, as now – we find it in the morning sky, with the distance between our 2 worlds increasing. Now, Venus’ is in a waxing phase; we’re seeing more of its day side each day. But its disk size is diminishing because it’s rushing ahead of us in orbit.
This chart – via Guy Ottewell’s blog – shows Earth and Venus in November, 2018. The sight lines to the sun and outer planets are set for mid-November. The arrows show Venus and Earth traveling in orbit throughout the month.
Venus passed between us and the sun on October 26, 2018. So this world was closer to Earth over the last month or so, yet its phase was exceedingly thin. Throughout the most of November, the illuminated portion of Venus (the sliver we could see of its day side) covered less square area of sky than it does at present. On December 1 or 2, 2018 (depending upon your time zone), Venus will reach its greatest illuminated extent – that moment of trade-off when the illuminated portion of Venus’ disk (the part we see) will cover the maximum area in Earth’s sky.
At or near greatest illuminated extent, Venus always shines most brightly in Earth’s sky.
That is the case for Venus, now.
Venus just passed the point that astronomers call inferior conjunction. See bottom of diagram. When Venus is to the east (left) of the Earth-sun line, we see Venus as an evening “star” in the west after sunset. After Venus reaches its inferior conjunction, Venus then moves to the west (right) of the Earth-sun line, appearing as a morning “star” in the east before sunrise. Note that Earth and Venus orbit the sun counterclockwise, as seen from the north of the solar system plane.
So Venus last passed between the Earth and sun on October 26, 2018. Some 72 days after this inferior conjunction, Venus will reach its greatest elongation (that is its maximum angular separation from the sun) on January 6, 2019. At that point, Venus’ disk will be approximately 50% illuminated in sunshine.
At Venus’ last greatest eastern elongation on August 17, 2018, Venus reigned over the evening sky; and at the coming greatest western elongation – on January 6, 2019 – Venus will reign in the morning sky. In ancient times, the Greeks actually called Venus Hesperus when she dominated the evening sky and Phosphorus when she loomed over the morning sky. Did they know these two entities were really a single world? Some say yes, and some say no.
Midway between greatest eastern (evening) elongation and inferior conjunction, Venus’ disk is about 25% illuminated in sunshine and this is when Venus shines brightest in the evening sky.
Then, midway between inferior conjunction and greatest western (morning) elongation, Venus’ disk is again 25% illuminated in sunshine and this is when Venus beams most mightily in the morning sky.
Alice Cheung in Plymouth, U.K. wrote on November 20, 2018: “I got up and opened the curtains. It’s been a while since we had a clear sky, so I was surprised to see Venus shining so brightly!”
Bottom line: In late November and early December, Venus enjoys her glory days – her greatest brilliancy – in the morning sky. Look east before sunup! Greatest illuminated extent for Venus – when this world shows us the maximum amount of its bright, reflective surface – will come on December 1 or 2, 2018, depending upon your time zone.
Tom Hoffman, InSight Project Manager, NASA JPL, left, and Sue Smrekar, InSight deputy principal investigator, NASA JPL, react after receiving confirmation that the Mars InSight lander successfully touched down on the surface of Mars on Monday. Image via NASA/ Bill Ingalls.
It was a series of cheers – more cheers – and finally a gigantic cheer from space scientists and engineers at NASA’s Jet Propulsion Laboratory, as they witnessed the nail-biting minutes prior to the InSight spacecraft’s successful touchdown on Mars’ surface on Monday, November 26, 2018. The lander touched down near Mars’ equator on the western side of a flat, smooth expanse of lava called Elysium Planitia. The signal affirming a completed landing sequence came at 19:52:59 UTC (2:52:59 p.m. EST). This was NASA’s eighth successful soft-landing on Mars.
InSight took almost seven months to travel 300 million miles (458 million km) from Earth. This craft is not a rover; it’s designed to stay in one place and to drill into and study Mars’ deep interior. The name InSight stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport. NASA said:
InSight’s two-year mission will be to study the deep interior of Mars to learn how all celestial bodies with rocky surfaces, including Earth and the Moon, formed.
We hit the Martian atmosphere at 12,300 mph (19,800 km per hour), and the whole sequence to touching down on the surface took only six-and-a-half minutes. During that short span of time, InSight had to autonomously perform dozens of operations and do them flawlessly – and by all indications that is exactly what our spacecraft did.
Another big winner on Monday was the MarCO mission, embodied in two briefcase-sized CubeSats that launched on the same rocket as InSight and made the trip to Mars with it. When they reached Mars, after successfully carrying out a number of communications and in-flight navigation experiments, the twin MarCOs were set in position to receive transmissions during InSight’s entry, descent and landing. The MarCOs successfully received the landing signal from InSight and relayed it to NASA’s Jet Propulsion Laboratory in Pasadena, California. They are the first CubeSats sent into deep space. Joel Krajewski, MarCO project manager at JPL, said:
That’s one giant leap for our intrepid, briefcase-sized robotic explorers. I think CubeSats have a big future beyond Earth’s orbit, and the MarCO team is happy to trailblaze the way.
Totally agree. Copies of these sats could be built for a few hundred $K now, and soon will cost tens of $K. NASA Science is wisely investing in this exciting area. https://t.co/ephq4ia1Lz
InSight will begin to collect science data within the first week after landing, though the teams will focus mainly on preparing to set InSight’s instruments on the Martian ground. At least two days after touchdown, the engineering team will begin to deploy InSight’s 5.9-foot-long (1.8-meter-long) robotic arm so that it can take images of the landscape.
InSight principal investigator Bruce Banerdt of JPL said:
Landing was thrilling, but I’m looking forward to the drilling. When the first images come down, our engineering and science teams will hit the ground running, beginning to plan where to deploy our science instruments. Within two or three months, the arm will deploy the mission’s main science instruments, the Seismic Experiment for Interior Structure (SEIS) and Heat Flow and Physical Properties Package (HP3) instruments.
InSight is expected to operate on the surface for one Martian year, plus 40 Martian days, or sols, until at least November 24, 2020.
Here's a version of @NASAInSight's first #Mars image edited to remove the distracting debris from the lens cover and some barrel distortion. For aesthetic enjoyment only (and until we see a new version from the lander!) #MarsLandingpic.twitter.com/Kdf9yxwPvX
Tom Hoffman, InSight Project Manager, NASA JPL, left, and Sue Smrekar, InSight deputy principal investigator, NASA JPL, react after receiving confirmation that the Mars InSight lander successfully touched down on the surface of Mars on Monday. Image via NASA/ Bill Ingalls.
It was a series of cheers – more cheers – and finally a gigantic cheer from space scientists and engineers at NASA’s Jet Propulsion Laboratory, as they witnessed the nail-biting minutes prior to the InSight spacecraft’s successful touchdown on Mars’ surface on Monday, November 26, 2018. The lander touched down near Mars’ equator on the western side of a flat, smooth expanse of lava called Elysium Planitia. The signal affirming a completed landing sequence came at 19:52:59 UTC (2:52:59 p.m. EST). This was NASA’s eighth successful soft-landing on Mars.
InSight took almost seven months to travel 300 million miles (458 million km) from Earth. This craft is not a rover; it’s designed to stay in one place and to drill into and study Mars’ deep interior. The name InSight stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport. NASA said:
InSight’s two-year mission will be to study the deep interior of Mars to learn how all celestial bodies with rocky surfaces, including Earth and the Moon, formed.
We hit the Martian atmosphere at 12,300 mph (19,800 km per hour), and the whole sequence to touching down on the surface took only six-and-a-half minutes. During that short span of time, InSight had to autonomously perform dozens of operations and do them flawlessly – and by all indications that is exactly what our spacecraft did.
Another big winner on Monday was the MarCO mission, embodied in two briefcase-sized CubeSats that launched on the same rocket as InSight and made the trip to Mars with it. When they reached Mars, after successfully carrying out a number of communications and in-flight navigation experiments, the twin MarCOs were set in position to receive transmissions during InSight’s entry, descent and landing. The MarCOs successfully received the landing signal from InSight and relayed it to NASA’s Jet Propulsion Laboratory in Pasadena, California. They are the first CubeSats sent into deep space. Joel Krajewski, MarCO project manager at JPL, said:
That’s one giant leap for our intrepid, briefcase-sized robotic explorers. I think CubeSats have a big future beyond Earth’s orbit, and the MarCO team is happy to trailblaze the way.
Totally agree. Copies of these sats could be built for a few hundred $K now, and soon will cost tens of $K. NASA Science is wisely investing in this exciting area. https://t.co/ephq4ia1Lz
InSight will begin to collect science data within the first week after landing, though the teams will focus mainly on preparing to set InSight’s instruments on the Martian ground. At least two days after touchdown, the engineering team will begin to deploy InSight’s 5.9-foot-long (1.8-meter-long) robotic arm so that it can take images of the landscape.
InSight principal investigator Bruce Banerdt of JPL said:
Landing was thrilling, but I’m looking forward to the drilling. When the first images come down, our engineering and science teams will hit the ground running, beginning to plan where to deploy our science instruments. Within two or three months, the arm will deploy the mission’s main science instruments, the Seismic Experiment for Interior Structure (SEIS) and Heat Flow and Physical Properties Package (HP3) instruments.
InSight is expected to operate on the surface for one Martian year, plus 40 Martian days, or sols, until at least November 24, 2020.
Here's a version of @NASAInSight's first #Mars image edited to remove the distracting debris from the lens cover and some barrel distortion. For aesthetic enjoyment only (and until we see a new version from the lander!) #MarsLandingpic.twitter.com/Kdf9yxwPvX
