Here is a picture to show you the state of the solar system. The view is from 15 degrees north of the ecliptic plane, at longitude 217 degrees and 6 astronomical units from the sun. The dashed line is the vernal equinox direction (where the sun appeared to be at the March 20 equinox). The purpose is to show the paths of the planets in April and May, and sightlines from Earth to them at April 29.
You can see that the only planet in the evening sky, that is, to the “left” (east) of the sun, is Venus, still slowly climbing in that direction.
Jupiter – which is near the moon this weekend – will move into the evening sky, that is, reach opposition and be highest at midnight, on May 9. Farther on the morning side, Mars and Saturn make a group; Mars passed Saturn on April 2.
And lower, into the morning twilight, Mercury is on April 29 at greatest elongation, or angular distance from the sun.
Mercury’s elongation is indeed the greatest for this year (27 degrees). And yet, because of the angle at which it comes slanting out from our north-hemisphere horizon, this is the worst, that is, worst of Mercury’s appearances from our Northern Hemisphere perspective – the paradox caused by the small planet’s oblique orbit.
Bottom line: Bright planets Jupiter, Saturn, Mars, Venus, Mercury as seen from above the solar system – with the line of sight from Earth marked – on April 29, 2018.
Here is a picture to show you the state of the solar system. The view is from 15 degrees north of the ecliptic plane, at longitude 217 degrees and 6 astronomical units from the sun. The dashed line is the vernal equinox direction (where the sun appeared to be at the March 20 equinox). The purpose is to show the paths of the planets in April and May, and sightlines from Earth to them at April 29.
You can see that the only planet in the evening sky, that is, to the “left” (east) of the sun, is Venus, still slowly climbing in that direction.
Jupiter – which is near the moon this weekend – will move into the evening sky, that is, reach opposition and be highest at midnight, on May 9. Farther on the morning side, Mars and Saturn make a group; Mars passed Saturn on April 2.
And lower, into the morning twilight, Mercury is on April 29 at greatest elongation, or angular distance from the sun.
Mercury’s elongation is indeed the greatest for this year (27 degrees). And yet, because of the angle at which it comes slanting out from our north-hemisphere horizon, this is the worst, that is, worst of Mercury’s appearances from our Northern Hemisphere perspective – the paradox caused by the small planet’s oblique orbit.
Bottom line: Bright planets Jupiter, Saturn, Mars, Venus, Mercury as seen from above the solar system – with the line of sight from Earth marked – on April 29, 2018.
Composite image of Jupiter and its 4 Galilean moons. From top to bottom the moons are Io, Europa, Ganymede, Callisto. The Galileo spacecraft obtained the images to make this composite in 1996. Image via NASA PhotoJournal.
If you have binoculars or a telescope, it’s fairly easy whenever Jupiter is visible to see the giant planet’s four largest moons. They look like pinpricks of light – like tiny “stars” – all on or near the same plane crossing the planet. They’re often called the Galilean moons to honor Galileo, who discovered them in 1610.
In their order from Jupiter, these moons are Io, Europa, Ganymede and Callisto.
… put a low-power eyepiece in your telescope and center Jupiter. Focus carefully so that the planet’s edge is as sharp as possible, let any vibrations settle down, and then take a good long look.
Depending on the size of your scope and the quality of the night’s seeing … you’ll probably see all four, but possibly only three depending on when you look. The count often changes from night to night (or if you’re patient, even from hour to hour). That’s because while orbiting Jupiter they sometimes glide in front of the planet, behind it, or through its shadow.
These hide-and-seek movements confounded Galileo Galilei when he first spied these ‘stars’ in 1610. But he soon realized they were actually circling around Jupiter, forming a miniature solar system of sorts. We see their orbits almost exactly edge on.
…Callisto is usually (but not always) farthest from Jupiter, and Ganymede is a little brighter than the others. Sulfur-coated Io has a pale yellow-orange cast. Still not sure? The answers are just a mouse clicks away, thanks to SkyandTelescope.com’s handy guide to identifying the Galilean satellites at any time and date.
Fernando Roquel Torres in Caguas, Puerto Rico, captured Jupiter, the Great Red Spot (GRS) and all 4 of its largest moons – the Galilean satellites – on the date of Jupiter’s 2017 opposition (April 7).
Jupiter and three of its four Galilean satellites, as they would appear in a small telescope. Illustration via SkyandTelescope.com.
As Kelly said, the Galilean moons orbit Jupiter around its equator. We do see their orbits almost exactly edge-on, but, as with so much in astronomy, there’s a cycle for viewing the edge-on-ness of Jupiter’s moons. This particular cycle is six years long. That is, every six years, we view Jupiter’s equator – and the moons orbiting above its equator – most edge-on.
Starting in late 2016, Jupiter’s axis began tilting enough toward the sun and Earth so that the outermost of the four moons, Callisto, has not been passing in front of Jupiter or behind Jupiter, as seen from our vantage point. This will continue for a period of about three years, during which time Callisto is perpetually visible to those with telescopes, alternately swinging above and below Jupiter as seen from Earth.
Composite image of Jupiter and its 4 Galilean moons. From top to bottom the moons are Io, Europa, Ganymede, Callisto. The Galileo spacecraft obtained the images to make this composite in 1996. Image via NASA PhotoJournal.
If you have binoculars or a telescope, it’s fairly easy whenever Jupiter is visible to see the giant planet’s four largest moons. They look like pinpricks of light – like tiny “stars” – all on or near the same plane crossing the planet. They’re often called the Galilean moons to honor Galileo, who discovered them in 1610.
In their order from Jupiter, these moons are Io, Europa, Ganymede and Callisto.
… put a low-power eyepiece in your telescope and center Jupiter. Focus carefully so that the planet’s edge is as sharp as possible, let any vibrations settle down, and then take a good long look.
Depending on the size of your scope and the quality of the night’s seeing … you’ll probably see all four, but possibly only three depending on when you look. The count often changes from night to night (or if you’re patient, even from hour to hour). That’s because while orbiting Jupiter they sometimes glide in front of the planet, behind it, or through its shadow.
These hide-and-seek movements confounded Galileo Galilei when he first spied these ‘stars’ in 1610. But he soon realized they were actually circling around Jupiter, forming a miniature solar system of sorts. We see their orbits almost exactly edge on.
…Callisto is usually (but not always) farthest from Jupiter, and Ganymede is a little brighter than the others. Sulfur-coated Io has a pale yellow-orange cast. Still not sure? The answers are just a mouse clicks away, thanks to SkyandTelescope.com’s handy guide to identifying the Galilean satellites at any time and date.
Fernando Roquel Torres in Caguas, Puerto Rico, captured Jupiter, the Great Red Spot (GRS) and all 4 of its largest moons – the Galilean satellites – on the date of Jupiter’s 2017 opposition (April 7).
Jupiter and three of its four Galilean satellites, as they would appear in a small telescope. Illustration via SkyandTelescope.com.
As Kelly said, the Galilean moons orbit Jupiter around its equator. We do see their orbits almost exactly edge-on, but, as with so much in astronomy, there’s a cycle for viewing the edge-on-ness of Jupiter’s moons. This particular cycle is six years long. That is, every six years, we view Jupiter’s equator – and the moons orbiting above its equator – most edge-on.
Starting in late 2016, Jupiter’s axis began tilting enough toward the sun and Earth so that the outermost of the four moons, Callisto, has not been passing in front of Jupiter or behind Jupiter, as seen from our vantage point. This will continue for a period of about three years, during which time Callisto is perpetually visible to those with telescopes, alternately swinging above and below Jupiter as seen from Earth.
Rearing on its hind legs, the giant ground sloth would have been a formidable prey for anyone, let alone humans without modern weapons. Tightly muscled, angry and swinging its forelegs tipped with wolverine-like claws, it would have been able to defend itself effectively. Our ancestors used misdirection to gain the upper hand in close-quarter combat with this deadly creature.
What is perhaps even more remarkable is that we can read this story from the 10,000-year-old footprints that these combatants left behind, as revealed by our new research published April 25, 2018, in Science Advances. Numerous large animals such as the giant ground sloth – so-called megafauna – became extinct at the end of the Ice Age. We don’t know if hunting was the cause but the new footprint evidence tells us how human hunters tackled such fearsome animals and clearly shows that they did.
White Sands National Monument. Image via Matthew Bennett, Bournemouth University.
These footprints were found at White Sands National Monument in New Mexico, U.S., on part of the monument used by the military. The White Sands Missile Range, located close to the Trinity nuclear site, is famous as the birthplace of the U.S. space program, of Ronald Reagan’s Star Wars initiative and of countless missile tests. It is now a place where long-range rather than close-quarter combat is fine-tuned.
Tracking the footprints. Image via Matthew Bennett, Bournemouth University.
It is a beautiful place, home to a huge salt playa (dry lake) known as Alkali Flat and the world’s largest gypsum dune field, made famous by numerous films including “Transformers” and “The Book of Eli.” At the height of the Ice Age it was home to a large lake (paleo Lake Otero).
As the climate warmed, the lake shrank and its bed was eroded by the wind to create the dunes and leave salt flats that periodically pooled water. The Ice Age megafauna left tracks on these flats, as did the humans that hunted them. The tracks are remarkable in that they are only a few centimeters beneath the surface and yet have been preserved for over 10,000 years.
Footprint comparison. Image via David Bustos, National Park Service.
Here there are tracks of extinct giant ground sloth, of mastodon, mammoth, camel and dire wolf. These tracks are colloquially known as “ghost tracks” as they are only visible at the surface during specific weather conditions, when the salt crusts are not too thick and the ground not too wet. Careful excavation is possible in the right conditions and reveals some amazing features.
Perhaps the coolest of these is a series of human tracks that we found within the sloth prints. In our paper, produced with a large number of colleagues, we suggest that the humans stepped into the sloth prints as they stalked them for the kill. We have also identified large “flailing circles” that record the sloth rising up on its hind legs and swinging its fore legs, presumably in a defensive, sweeping motion to keep the hunters at bay. As it overbalanced, it put its knuckles and claws down to steady itself.
Plaster cast footprints. Image via David Bustos, National Park Service.
These circles are always accompanied by human tracks. Over a wide area, we see that where there are no human tracks, the sloth walk in straight lines. Where human tracks are present, the sloth trackways show sudden changes in direction suggesting the sloth was trying to evade its hunters.
Piecing together the puzzle, we can see how sloth were kept on the flat playa by a horde of people who left tracks along the its edge. The animal was then distracted by one stalking hunter, while another crept forward and tried to strike the killing blow. It is a story of life and death, written in mud.
Matthew Bennett, dusting for prints. Image via David Bustos, National Park Service.
What would convince our ancestors to engage is such a deadly game? Surely the bigger the prey, the greater the risk? Maybe it was because a big kill could fill many stomachs without waste, or maybe it was pure human bravado.
At this time at the end of the last Ice Age, the Americas were being colonized by humans spreading out over the prairie plains. It was also a time of animal extinctions. Many paleontologists favor the argument that human over-hunting drove this wave of extinction and for some it has become an emblem of early human impact on the environment. Others argue that climate change was the true cause and our species is innocent.
It is a giant crime scene in which footprints now play a part. Our data confirms that human hunters were attacking megafauna and were practiced at it. Unfortunately, it doesn’t cast light on the impact of that hunting. Whether humans were the ultimate or immediate cause of the extinction is still not clear. There are many variables including rapid environmental change to be considered. But what is clear from tracks at White Sands is that humans were then, as now, “apex predators” at the top of the food chain.
Rearing on its hind legs, the giant ground sloth would have been a formidable prey for anyone, let alone humans without modern weapons. Tightly muscled, angry and swinging its forelegs tipped with wolverine-like claws, it would have been able to defend itself effectively. Our ancestors used misdirection to gain the upper hand in close-quarter combat with this deadly creature.
What is perhaps even more remarkable is that we can read this story from the 10,000-year-old footprints that these combatants left behind, as revealed by our new research published April 25, 2018, in Science Advances. Numerous large animals such as the giant ground sloth – so-called megafauna – became extinct at the end of the Ice Age. We don’t know if hunting was the cause but the new footprint evidence tells us how human hunters tackled such fearsome animals and clearly shows that they did.
White Sands National Monument. Image via Matthew Bennett, Bournemouth University.
These footprints were found at White Sands National Monument in New Mexico, U.S., on part of the monument used by the military. The White Sands Missile Range, located close to the Trinity nuclear site, is famous as the birthplace of the U.S. space program, of Ronald Reagan’s Star Wars initiative and of countless missile tests. It is now a place where long-range rather than close-quarter combat is fine-tuned.
Tracking the footprints. Image via Matthew Bennett, Bournemouth University.
It is a beautiful place, home to a huge salt playa (dry lake) known as Alkali Flat and the world’s largest gypsum dune field, made famous by numerous films including “Transformers” and “The Book of Eli.” At the height of the Ice Age it was home to a large lake (paleo Lake Otero).
As the climate warmed, the lake shrank and its bed was eroded by the wind to create the dunes and leave salt flats that periodically pooled water. The Ice Age megafauna left tracks on these flats, as did the humans that hunted them. The tracks are remarkable in that they are only a few centimeters beneath the surface and yet have been preserved for over 10,000 years.
Footprint comparison. Image via David Bustos, National Park Service.
Here there are tracks of extinct giant ground sloth, of mastodon, mammoth, camel and dire wolf. These tracks are colloquially known as “ghost tracks” as they are only visible at the surface during specific weather conditions, when the salt crusts are not too thick and the ground not too wet. Careful excavation is possible in the right conditions and reveals some amazing features.
Perhaps the coolest of these is a series of human tracks that we found within the sloth prints. In our paper, produced with a large number of colleagues, we suggest that the humans stepped into the sloth prints as they stalked them for the kill. We have also identified large “flailing circles” that record the sloth rising up on its hind legs and swinging its fore legs, presumably in a defensive, sweeping motion to keep the hunters at bay. As it overbalanced, it put its knuckles and claws down to steady itself.
Plaster cast footprints. Image via David Bustos, National Park Service.
These circles are always accompanied by human tracks. Over a wide area, we see that where there are no human tracks, the sloth walk in straight lines. Where human tracks are present, the sloth trackways show sudden changes in direction suggesting the sloth was trying to evade its hunters.
Piecing together the puzzle, we can see how sloth were kept on the flat playa by a horde of people who left tracks along the its edge. The animal was then distracted by one stalking hunter, while another crept forward and tried to strike the killing blow. It is a story of life and death, written in mud.
Matthew Bennett, dusting for prints. Image via David Bustos, National Park Service.
What would convince our ancestors to engage is such a deadly game? Surely the bigger the prey, the greater the risk? Maybe it was because a big kill could fill many stomachs without waste, or maybe it was pure human bravado.
At this time at the end of the last Ice Age, the Americas were being colonized by humans spreading out over the prairie plains. It was also a time of animal extinctions. Many paleontologists favor the argument that human over-hunting drove this wave of extinction and for some it has become an emblem of early human impact on the environment. Others argue that climate change was the true cause and our species is innocent.
It is a giant crime scene in which footprints now play a part. Our data confirms that human hunters were attacking megafauna and were practiced at it. Unfortunately, it doesn’t cast light on the impact of that hunting. Whether humans were the ultimate or immediate cause of the extinction is still not clear. There are many variables including rapid environmental change to be considered. But what is clear from tracks at White Sands is that humans were then, as now, “apex predators” at the top of the food chain.
Man and moonset – March 1, 2018 – from Martin Marthadinata in Surabaya, East Java, Indonesia.
For general reference, we say a full moon is full all night. Because, in order to look full, the moon has to be more or less opposite the sun, every full moon rises in the east around sunset and climbs highest up for the night midway between sunset and sunrise (around midnight). Every full moon sets around sunup. That’s true as seen from around the globe.
But, technically speaking, the moon is full only at the instant that it’s 180o from the sun in ecliptic longitude. The moon turns full on April 30, 2018 at 00:58 UTC, which at North American time zones translates to April 29 at 9:58 p.m. ADT, 8:58 p.m. EDT, 7:58 p.m. CDT, 6:58 p.m. MDT and 5:58 p.m. PDT.
This full moon will be near a very bright planet, Jupiter, as shown on the chart below:
The moon is near the dazzling planet Jupiter on the night of April 28-30, 2018.
Here’s something else fun about this April 2018 full moon, and, in fact, about most full moons. That is, it won’t undergo an eclipse. In fact, the April 2018 full moon swings a whopping 5o (10 moon diameters) north of the ecliptic, the plane of Earth’s orbit around the sun. So it misses being in Earth’s shadow by a wide margin.
Some full moons come closer to passing through Earth’s shadow – that is, closer to being in eclipse without actually doing so – but the fact is that most full moons fail to reside at the antisolar point, the point that’s directly opposite the sun. It’s only when the moon passes through or very close to the antisolar point that we see a total eclipse of the moon.
October 8, 2014 total lunar eclipse composite by Michele Whitlow.
The next two full moons – May and June 2018 – will pass to the north of the ecliptic and the antisolar point, too. So there will be no lunar eclipse in May or June 2018.
The July 2018 full moon will sweep right through the antisolar point. The center of the full moon will pass a scant one-tenth of a degree north of the ecliptic. So, if you’re on the right place on Earth, you’ll see a total lunar eclipse on July 27, 2018.
This total lunar eclipse on July 27 comes one fortnight (two weeks) after the partial solar eclipse of July 13, 2018, and one fortnight (two weeks) before the partial solar eclipse on August 11, 2018.
Worldwide map of the total eclipse of the moon via EclipseWise. Note that the full moon passes right over the antisolar point (the + at the center of the Earth’s shadow). Click here for a more detailed chart.
This April full moon is the second full moon after the March equinox. In North America, we’ll call it the Pink Moon, Grass Moon or Egg Moon. Meanwhile, in the Southern Hemisphere, this full moon is called the Hunter’s Moon, the full moon that immediately follows the Harvest Moon.
Worldwide map via the US Naval Observatory, showing the daytime and nighttime sides of Earth at the instant of full moon (2018 April 30 at 00:58 UTC). The shadow line at left (running through the US) depicts sunset April 29, and the shadow line at right represents sunrise April 30.
Bottom line: From the world’s western hemisphere, the moon is full on the night of April 29, 2018. From the eastern hemisphere, it’s full on April 30. It swings a whopping 5o (10 moon diameters) north of the plane of Earth’s orbit around the sun and misses being in Earth’s shadow by a wide margin.
Man and moonset – March 1, 2018 – from Martin Marthadinata in Surabaya, East Java, Indonesia.
For general reference, we say a full moon is full all night. Because, in order to look full, the moon has to be more or less opposite the sun, every full moon rises in the east around sunset and climbs highest up for the night midway between sunset and sunrise (around midnight). Every full moon sets around sunup. That’s true as seen from around the globe.
But, technically speaking, the moon is full only at the instant that it’s 180o from the sun in ecliptic longitude. The moon turns full on April 30, 2018 at 00:58 UTC, which at North American time zones translates to April 29 at 9:58 p.m. ADT, 8:58 p.m. EDT, 7:58 p.m. CDT, 6:58 p.m. MDT and 5:58 p.m. PDT.
This full moon will be near a very bright planet, Jupiter, as shown on the chart below:
The moon is near the dazzling planet Jupiter on the night of April 28-30, 2018.
Here’s something else fun about this April 2018 full moon, and, in fact, about most full moons. That is, it won’t undergo an eclipse. In fact, the April 2018 full moon swings a whopping 5o (10 moon diameters) north of the ecliptic, the plane of Earth’s orbit around the sun. So it misses being in Earth’s shadow by a wide margin.
Some full moons come closer to passing through Earth’s shadow – that is, closer to being in eclipse without actually doing so – but the fact is that most full moons fail to reside at the antisolar point, the point that’s directly opposite the sun. It’s only when the moon passes through or very close to the antisolar point that we see a total eclipse of the moon.
October 8, 2014 total lunar eclipse composite by Michele Whitlow.
The next two full moons – May and June 2018 – will pass to the north of the ecliptic and the antisolar point, too. So there will be no lunar eclipse in May or June 2018.
The July 2018 full moon will sweep right through the antisolar point. The center of the full moon will pass a scant one-tenth of a degree north of the ecliptic. So, if you’re on the right place on Earth, you’ll see a total lunar eclipse on July 27, 2018.
This total lunar eclipse on July 27 comes one fortnight (two weeks) after the partial solar eclipse of July 13, 2018, and one fortnight (two weeks) before the partial solar eclipse on August 11, 2018.
Worldwide map of the total eclipse of the moon via EclipseWise. Note that the full moon passes right over the antisolar point (the + at the center of the Earth’s shadow). Click here for a more detailed chart.
This April full moon is the second full moon after the March equinox. In North America, we’ll call it the Pink Moon, Grass Moon or Egg Moon. Meanwhile, in the Southern Hemisphere, this full moon is called the Hunter’s Moon, the full moon that immediately follows the Harvest Moon.
Worldwide map via the US Naval Observatory, showing the daytime and nighttime sides of Earth at the instant of full moon (2018 April 30 at 00:58 UTC). The shadow line at left (running through the US) depicts sunset April 29, and the shadow line at right represents sunrise April 30.
Bottom line: From the world’s western hemisphere, the moon is full on the night of April 29, 2018. From the eastern hemisphere, it’s full on April 30. It swings a whopping 5o (10 moon diameters) north of the plane of Earth’s orbit around the sun and misses being in Earth’s shadow by a wide margin.
Take a first-person journey across the landscape of six exoplanets in this virtual exoplanet tour, above. The planets include Wasp-121b, a world whose atmosphere is being driven off by its parent star; Kepler-62e, which may be covered by a deep ocean and ravaged by monster waves; and 55 Cancri e, a hellish world likely covered in vast lava flows and engulfed in huge lightning storms. The virtual tour – with its 360-degree visual display – was designed and created by astrophysicists from the University of Exeter, in conjunction with the science center We The Curious in Bristol, U.K., and visual effects artists from Cornwall-based animation studio Engine House.
The tour has had over a million YouTube views since launching in late 2017.
Astronomer Nathan Mayne of the University of Exeter said in a statement:
It is great to know that our research into distant planets has fascinated so many people. However, more importantly hopefully through this video we have been able to explain and demystify our research enabling everyone to understand and get excited about our exploration of the planets in our galaxy … The mini-documentary gives a snapshot of astrophysical techniques, and what we have learned about planets using them.
Ross Exton, video producer for We The Curious, added:
I wanted to create something I’d never seen before. By collaborating with talented visual effects artists and astrophysicists currently studying these exoplanets, we were able to create a series of visuals which are not only stunning, but are informed by real scientific research.
Bottom line: Take a virtual tour of six exoplanets.
Take a first-person journey across the landscape of six exoplanets in this virtual exoplanet tour, above. The planets include Wasp-121b, a world whose atmosphere is being driven off by its parent star; Kepler-62e, which may be covered by a deep ocean and ravaged by monster waves; and 55 Cancri e, a hellish world likely covered in vast lava flows and engulfed in huge lightning storms. The virtual tour – with its 360-degree visual display – was designed and created by astrophysicists from the University of Exeter, in conjunction with the science center We The Curious in Bristol, U.K., and visual effects artists from Cornwall-based animation studio Engine House.
The tour has had over a million YouTube views since launching in late 2017.
Astronomer Nathan Mayne of the University of Exeter said in a statement:
It is great to know that our research into distant planets has fascinated so many people. However, more importantly hopefully through this video we have been able to explain and demystify our research enabling everyone to understand and get excited about our exploration of the planets in our galaxy … The mini-documentary gives a snapshot of astrophysical techniques, and what we have learned about planets using them.
Ross Exton, video producer for We The Curious, added:
I wanted to create something I’d never seen before. By collaborating with talented visual effects artists and astrophysicists currently studying these exoplanets, we were able to create a series of visuals which are not only stunning, but are informed by real scientific research.
Bottom line: Take a virtual tour of six exoplanets.
In late April 2018, the sun’s innermost planet Mercury swings to its greatest western elongation from the sun, that is, its farthest point west of the sun in our sky for this morning apparition. Mercury is 27 degrees west of the sun at its farthest, this time around. It’s low in the eastern sky before sunrise. Farthest from the sunrise … sounds easiest to view, right? That’s true for the Southern Hemisphere; this is Mercury’s best apparition in the morning sky for all of 2018 for southerly latitudes. Yet at northerly latitudes, this is Mercury’s poorest showing in the morning sky for the year.
The featured sky chart above is especially for the Southern Hemisphere. It’s specifically for Cape Town, South Africa, which is roughly the same latitude as Sydney, Australia and Auckland, New Zealand and Santiago, Chile. Given an unobstructed eastern horizon, all these places should be able to view Mercury with the eye alone in a predawn sky. At temperate latitudes in the Southern Hemisphere (South Africa, southern Australia, New Zealand), Mercury rises better than 2 hours before the sun.
Meanwhile, at mid-northern latitudes (United States and Europe), Mercury comes up about an hour before sunrise, and mid-northern latitudes will find Mercury deeply buried in the glow of twilight.
That’s in spite of the fact that this present morning apparition will last for yet another month.
At northerly latitudes, the shallow angle of the ecliptic – the pathway of the sun, moon and planets – on springtime mornings keeps Mercury buried in the glare of sunrise.
Why is this morning showing of Mercury so outstanding from the Southern Hemisphere, but so poor in the Northern Hemisphere? Mercury’s distance west of the sun (27 degrees) is the same for the whole Earth. Here’s what’s different. The ecliptic – the roadway of the sun, moon and planets across the sky – makes a narrow angle with the predawn horizon in spring. Meanwhile, in autumn, it makes an exceptionally steep angle (nearly perpendicular) with the predawn horizon … and it’s autumn now south of the equator.
Bottom line: If you live in the Southern Hemisphere, late April and early May 2018 present your best opportunity of 2018 to spot Mercury, the innermost planet, in east before sunrise.
In late April 2018, the sun’s innermost planet Mercury swings to its greatest western elongation from the sun, that is, its farthest point west of the sun in our sky for this morning apparition. Mercury is 27 degrees west of the sun at its farthest, this time around. It’s low in the eastern sky before sunrise. Farthest from the sunrise … sounds easiest to view, right? That’s true for the Southern Hemisphere; this is Mercury’s best apparition in the morning sky for all of 2018 for southerly latitudes. Yet at northerly latitudes, this is Mercury’s poorest showing in the morning sky for the year.
The featured sky chart above is especially for the Southern Hemisphere. It’s specifically for Cape Town, South Africa, which is roughly the same latitude as Sydney, Australia and Auckland, New Zealand and Santiago, Chile. Given an unobstructed eastern horizon, all these places should be able to view Mercury with the eye alone in a predawn sky. At temperate latitudes in the Southern Hemisphere (South Africa, southern Australia, New Zealand), Mercury rises better than 2 hours before the sun.
Meanwhile, at mid-northern latitudes (United States and Europe), Mercury comes up about an hour before sunrise, and mid-northern latitudes will find Mercury deeply buried in the glow of twilight.
That’s in spite of the fact that this present morning apparition will last for yet another month.
At northerly latitudes, the shallow angle of the ecliptic – the pathway of the sun, moon and planets – on springtime mornings keeps Mercury buried in the glare of sunrise.
Why is this morning showing of Mercury so outstanding from the Southern Hemisphere, but so poor in the Northern Hemisphere? Mercury’s distance west of the sun (27 degrees) is the same for the whole Earth. Here’s what’s different. The ecliptic – the roadway of the sun, moon and planets across the sky – makes a narrow angle with the predawn horizon in spring. Meanwhile, in autumn, it makes an exceptionally steep angle (nearly perpendicular) with the predawn horizon … and it’s autumn now south of the equator.
Bottom line: If you live in the Southern Hemisphere, late April and early May 2018 present your best opportunity of 2018 to spot Mercury, the innermost planet, in east before sunrise.
A chronological listing of news articles posted on the Skeptical Science Facebook Page during the past week.
Editor's Pick
Global temperatures have dropped since 2016. Here’s why that’s normal.
It was only two years ago that a new record-warm global temperature was set, but things have already cooled off significantly. Temperature anomalies hit record peaks in 2016 but have been sliding since then. Global temperatures are still much warmer than normal, but according to NASA, the first quarter of 2018 (January-March) was the fourth warmest, behind 2015, 2016, 2017 and tied with 2010.
This is normal, of course.The world has not seen the last of global warming. The long-term upward trend in temperatures is the result of man-made fossil fuel emissions, but natural processes that affect global temperature — like El Niño — still play a role. Sometimes they make things warmer and sometimes they make things cooler.
The current cooling episode is mostly the result of a reversal of waters in the Tropical Pacific, which can modulate global temperature. Since the Pacific Ocean is our largest global body of water, what it does makes a big difference on global climate. A similar reversal followed the super El Niño in the late ’90s — 1998 was the hottest year on record at the time in part because of the warm El Niño water pushing global temperatures over the brink. Earth went from having one of the strongest El Niño events on record (very warm waters in the central Tropical Pacific) to a few years of cooler waters, thanks to a La Niña period.
A chronological listing of news articles posted on the Skeptical Science Facebook Page during the past week.
Editor's Pick
Global temperatures have dropped since 2016. Here’s why that’s normal.
It was only two years ago that a new record-warm global temperature was set, but things have already cooled off significantly. Temperature anomalies hit record peaks in 2016 but have been sliding since then. Global temperatures are still much warmer than normal, but according to NASA, the first quarter of 2018 (January-March) was the fourth warmest, behind 2015, 2016, 2017 and tied with 2010.
This is normal, of course.The world has not seen the last of global warming. The long-term upward trend in temperatures is the result of man-made fossil fuel emissions, but natural processes that affect global temperature — like El Niño — still play a role. Sometimes they make things warmer and sometimes they make things cooler.
The current cooling episode is mostly the result of a reversal of waters in the Tropical Pacific, which can modulate global temperature. Since the Pacific Ocean is our largest global body of water, what it does makes a big difference on global climate. A similar reversal followed the super El Niño in the late ’90s — 1998 was the hottest year on record at the time in part because of the warm El Niño water pushing global temperatures over the brink. Earth went from having one of the strongest El Niño events on record (very warm waters in the central Tropical Pacific) to a few years of cooler waters, thanks to a La Niña period.
It is a giant crime scene in which footprints now play a part. Our data confirms that human hunters were attacking megafauna and were practiced at it. Unfortunately, it doesn’t cast light on the impact of that hunting. Whether humans were the ultimate or immediate cause of the extinction is still not clear. There are many variables including rapid environmental change to be considered. But what is clear from tracks at White Sands is that humans were then, as now, “apex predators” at the top of the food chain.
