Sun enters Ophiuchus on November 30

November 30, 2017. If you could see the stars in the daytime, you’d see the sun shining in front of the border of the constellations Ophiuchus and Scorpius on this date. The sun crosses a constellation boundary, into Ophiuchus.

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the zodiac … but unlike Scorpius, Ophiuchus is not one of the traditional twelve zodiacal constellations.

The sun will remain in front of Ophiuchus until December 18.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, as defined by the International Astronomical Union (IAU), although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned.

There are the 12 traditional zodiacal constellations that have been with us since ancient times. The relatively recent addition of Ophiuchus as a member of the zodiac has increased the number to 13.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

View larger. | Ophiuchus the Serpent Bearer.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Sun in zodiacal constellations 2017

Sun in zodiacal signs 2017

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

from EarthSky http://ift.tt/1l1yQbj

November 30, 2017. If you could see the stars in the daytime, you’d see the sun shining in front of the border of the constellations Ophiuchus and Scorpius on this date. The sun crosses a constellation boundary, into Ophiuchus.

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the zodiac … but unlike Scorpius, Ophiuchus is not one of the traditional twelve zodiacal constellations.

The sun will remain in front of Ophiuchus until December 18.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, as defined by the International Astronomical Union (IAU), although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned.

There are the 12 traditional zodiacal constellations that have been with us since ancient times. The relatively recent addition of Ophiuchus as a member of the zodiac has increased the number to 13.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

View larger. | Ophiuchus the Serpent Bearer.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Sun in zodiacal constellations 2017

Sun in zodiacal signs 2017

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

from EarthSky http://ift.tt/1l1yQbj

Where’s the moon? Waxing gibbous

Waxing gibbous moon via Clarise Samuels in Montreal. She used multiple exposures to superimpose the moon on a close-up of small light bulbs and she wrote: “It would be nice if we had a lot of moons.”

This week’s waxing gibbous moon rises during the hours between noon and sunset. It sets in the wee hours after midnight. It falls between a first quarter moon and a full moon, and, it so happens, this upcoming full moon is a supermoon.

Any moon that appears more than half lighted but less than full is called a gibbous moon. The word gibbous comes from a root word that means hump-backed.

People often see a waxing gibbous moon in the afternoon, shortly after moonrise, while it’s ascending in the east as the sun is descending in the west. It’s easy to see a waxing gibbous moon in the daytime because, at this phase of the moon, a respectably large fraction of the moon’s dayside is now facing our way.

Want to know more? Check out our post offering 4 keys to understanding moon phases.

Point of interest on a waxing gibbous moon: Sinus Iridum (Bay of Rainbows) surrounded by the Jura Mountains. Photo by Lunar 101-Moon Book in Toronto, Canada.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

from EarthSky http://ift.tt/1j8UWzb

Waxing gibbous moon via Clarise Samuels in Montreal. She used multiple exposures to superimpose the moon on a close-up of small light bulbs and she wrote: “It would be nice if we had a lot of moons.”

This week’s waxing gibbous moon rises during the hours between noon and sunset. It sets in the wee hours after midnight. It falls between a first quarter moon and a full moon, and, it so happens, this upcoming full moon is a supermoon.

Any moon that appears more than half lighted but less than full is called a gibbous moon. The word gibbous comes from a root word that means hump-backed.

People often see a waxing gibbous moon in the afternoon, shortly after moonrise, while it’s ascending in the east as the sun is descending in the west. It’s easy to see a waxing gibbous moon in the daytime because, at this phase of the moon, a respectably large fraction of the moon’s dayside is now facing our way.

Want to know more? Check out our post offering 4 keys to understanding moon phases.

Point of interest on a waxing gibbous moon: Sinus Iridum (Bay of Rainbows) surrounded by the Jura Mountains. Photo by Lunar 101-Moon Book in Toronto, Canada.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

from EarthSky http://ift.tt/1j8UWzb

Probing the Hubble Ultra Deep Field

Here’s the Hubble Ultra Deep Field region, as observed with the MUSE instrument installed at the Very Large Telescope of the European Southern Observatory in northern Chile. MUSE data provide a rainbow-like spectrum for each pixel in this picture. Image via ESO/ MUSE HUDF collaboration.

Sometimes, astronomy is about surveying widely to get the big picture. And sometimes it’s about looking more and more deeply. First released in 2004, the Hubble Ultra Deep Field is clearly about going deep. It’s a composite image of a tiny region of space, located in the direction of the southern constellation Fornax, made from Hubble Space Telescope data gathered over several months. There are an estimated 10,000 galaxies in the Hubble Ultra Deep Field, which exist as far back in time as 13 billion years ago (between 400 and 800 million years after the Big Bang). Being able to see galaxies so near the beginning of our universe has been a fantastic tool for understanding how the universe has evolved. And now – thanks to an instrument called MUSE (Multi Unit Spectroscopic Explorer), astronomers have been able to eke out yet more information – a veritable bonanza of information – from the Hubble Ultra Deep Field. Their work is being published today (November 29, 2017) in a series of 10 papers in a special issue of the peer-reviewed journal Astronomy & Astrophysics.

MUSE does more than just see the galaxies. It also splits their light into its component colors, using a technique that astronomers call spectroscopy. In the image above, a team of astronomers led by Roland Bacon of the Centre de recherche astrophysique de Lyon, France, used MUSE to obtain a rainbow-like spectrum for each pixel in the Hubble Ultra Deep Field.

These astronomers said this work involved:

… the deepest spectroscopic observations ever made.

They obtained spectra for 1,600 galaxies in the Hubble Ultra Deep Field. That’s 10 times as many galaxies as has been painstakingly obtained in this field over the last decade by ground-based telescopes. Roland Bacon said:

MUSE can do something that Hubble can’t — it splits up the light from every point in the image into its component colours to create a spectrum. This allows us to measure the distance, colors and other properties of all the galaxies we can see — including some that are invisible to Hubble itself.

Jarle Brinchmann, lead author of one of the papers describing results from this survey, from the University of Leiden in the Netherlands and the Institute of Astrophysics and Space Sciences at CAUP in Porto, Portugal, commented:

MUSE has the unique ability to extract information about some of the earliest galaxies in the universe — even in a part of the sky that is already very well studied. We learn things about these galaxies that is only possible with spectroscopy, such as chemical content and internal motions — not galaxy by galaxy but all at once for all the galaxies!

Among other results, MUSE revealed 72 galaxies never seen before in this very tiny area of the sky. These galaxies wouldn’t have been obvious to Hubble. They’re members of a perplexing group of galaxies known as Lyman-alpha emitters. They shine only in Lyman-alpha light (produced when electrons in hydrogen atoms drop from the second-lowest to the lowest energy level). These objects become noticeable in MUSE data because MUSE disperses the light into its component colors. Meanwhile, in direct images such as those from the Hubble Space Telescope, these galaxies remain invisible. Why do these galaxies shine in this peculiar way? Astronomers don’t fully know.

The work also revealed luminous hydrogen halos around galaxies in the early universe. The astronomers said this discovery offers:

… a new and promising way to study how material flows in and out of early galaxies.

Other potential applications of this dataset are explored in the series of papers, including a study of the role of faint galaxies during cosmic reionization (starting just 380,000 years after the Big Bang), galaxy merger rates when the universe was young, galactic winds, star formation and the mapping the motions of stars in the early universe.

Roland Bacon pointed out that the data for all of this work were obtained prior to an upgrade to MUSE’s Adaptive Optics Facility (AOF). He said:

The activation of the AOF after a decade of intensive work by ESO’s astronomers and engineers promises yet more revolutionary data in the future.

From MUSE’s website: “Looking like a machine straight out of the movie The Matrix, with its Medusa-like hoses and connections, MUSE is the latest of the 2nd-generation instruments to be installed on Yepun (UT4), the fourth Unit Telescope of the Very Large Telescope at the Paranal Observatory.”

Bottom line: Astronomers used an instrument called MUSE to peer toward the area of the Hubble Ultra Deep Field and to conduct the deepest-ever spectroscopic survey. The result? A bonanza of new knowledge!

The 10 new papers via MUSE:

The MUSE Hubble Ultra Deep Field Survey: I. Survey Description, Data Reduction and Source Detection

The MUSE Hubble Ultra Deep Field Survey: II. Spectroscopic Redshift and Line Flux Catalog, and Comparisons to Color Selections of Galaxies at 3 < z < 7

The MUSE Hubble Ultra Deep Field Survey: III. Testing Photometric Redshifts to 30th Magnitude

The MUSE Hubble Ultra Deep Field Survey: IV. An Overview of C III] Emitters

The MUSE Hubble Ultra Deep Field Survey: V. Spatially Resolved Stellar Kinematics of Galaxies at Redshift 0.2 < z < 0.8,”

The MUSE Hubble Ultra Deep Field Survey: VI. The Faint-End of the Ly-alpha Luminosity Function at 2.91 < z < 6.64 and Implications for Reionisation

The MUSE Hubble Ultra Deep Field Survey: VII. Fe II* Emission in Star-Forming Galaxies

The MUSE Hubble Ultra Deep Field Survey: VIII. Extended Lyman-alpha Haloes,

The MUSE Hubble Ultra Deep Field Survey: IX. Evolution of Galaxy Merger Fraction up to z ? 6

The MUSE Hubble Ultra Deep Field Survey: Ly-alpha Equivalent Widths at 2.9 < z < 6.6

from EarthSky http://ift.tt/2ijiYVE

Here’s the Hubble Ultra Deep Field region, as observed with the MUSE instrument installed at the Very Large Telescope of the European Southern Observatory in northern Chile. MUSE data provide a rainbow-like spectrum for each pixel in this picture. Image via ESO/ MUSE HUDF collaboration.

Sometimes, astronomy is about surveying widely to get the big picture. And sometimes it’s about looking more and more deeply. First released in 2004, the Hubble Ultra Deep Field is clearly about going deep. It’s a composite image of a tiny region of space, located in the direction of the southern constellation Fornax, made from Hubble Space Telescope data gathered over several months. There are an estimated 10,000 galaxies in the Hubble Ultra Deep Field, which exist as far back in time as 13 billion years ago (between 400 and 800 million years after the Big Bang). Being able to see galaxies so near the beginning of our universe has been a fantastic tool for understanding how the universe has evolved. And now – thanks to an instrument called MUSE (Multi Unit Spectroscopic Explorer), astronomers have been able to eke out yet more information – a veritable bonanza of information – from the Hubble Ultra Deep Field. Their work is being published today (November 29, 2017) in a series of 10 papers in a special issue of the peer-reviewed journal Astronomy & Astrophysics.

MUSE does more than just see the galaxies. It also splits their light into its component colors, using a technique that astronomers call spectroscopy. In the image above, a team of astronomers led by Roland Bacon of the Centre de recherche astrophysique de Lyon, France, used MUSE to obtain a rainbow-like spectrum for each pixel in the Hubble Ultra Deep Field.

These astronomers said this work involved:

… the deepest spectroscopic observations ever made.

They obtained spectra for 1,600 galaxies in the Hubble Ultra Deep Field. That’s 10 times as many galaxies as has been painstakingly obtained in this field over the last decade by ground-based telescopes. Roland Bacon said:

MUSE can do something that Hubble can’t — it splits up the light from every point in the image into its component colours to create a spectrum. This allows us to measure the distance, colors and other properties of all the galaxies we can see — including some that are invisible to Hubble itself.

Jarle Brinchmann, lead author of one of the papers describing results from this survey, from the University of Leiden in the Netherlands and the Institute of Astrophysics and Space Sciences at CAUP in Porto, Portugal, commented:

MUSE has the unique ability to extract information about some of the earliest galaxies in the universe — even in a part of the sky that is already very well studied. We learn things about these galaxies that is only possible with spectroscopy, such as chemical content and internal motions — not galaxy by galaxy but all at once for all the galaxies!

Among other results, MUSE revealed 72 galaxies never seen before in this very tiny area of the sky. These galaxies wouldn’t have been obvious to Hubble. They’re members of a perplexing group of galaxies known as Lyman-alpha emitters. They shine only in Lyman-alpha light (produced when electrons in hydrogen atoms drop from the second-lowest to the lowest energy level). These objects become noticeable in MUSE data because MUSE disperses the light into its component colors. Meanwhile, in direct images such as those from the Hubble Space Telescope, these galaxies remain invisible. Why do these galaxies shine in this peculiar way? Astronomers don’t fully know.

The work also revealed luminous hydrogen halos around galaxies in the early universe. The astronomers said this discovery offers:

… a new and promising way to study how material flows in and out of early galaxies.

Other potential applications of this dataset are explored in the series of papers, including a study of the role of faint galaxies during cosmic reionization (starting just 380,000 years after the Big Bang), galaxy merger rates when the universe was young, galactic winds, star formation and the mapping the motions of stars in the early universe.

Roland Bacon pointed out that the data for all of this work were obtained prior to an upgrade to MUSE’s Adaptive Optics Facility (AOF). He said:

The activation of the AOF after a decade of intensive work by ESO’s astronomers and engineers promises yet more revolutionary data in the future.

From MUSE’s website: “Looking like a machine straight out of the movie The Matrix, with its Medusa-like hoses and connections, MUSE is the latest of the 2nd-generation instruments to be installed on Yepun (UT4), the fourth Unit Telescope of the Very Large Telescope at the Paranal Observatory.”

Bottom line: Astronomers used an instrument called MUSE to peer toward the area of the Hubble Ultra Deep Field and to conduct the deepest-ever spectroscopic survey. The result? A bonanza of new knowledge!

The 10 new papers via MUSE:

The MUSE Hubble Ultra Deep Field Survey: I. Survey Description, Data Reduction and Source Detection

The MUSE Hubble Ultra Deep Field Survey: II. Spectroscopic Redshift and Line Flux Catalog, and Comparisons to Color Selections of Galaxies at 3 < z < 7

The MUSE Hubble Ultra Deep Field Survey: III. Testing Photometric Redshifts to 30th Magnitude

The MUSE Hubble Ultra Deep Field Survey: IV. An Overview of C III] Emitters

The MUSE Hubble Ultra Deep Field Survey: V. Spatially Resolved Stellar Kinematics of Galaxies at Redshift 0.2 < z < 0.8,”

The MUSE Hubble Ultra Deep Field Survey: VI. The Faint-End of the Ly-alpha Luminosity Function at 2.91 < z < 6.64 and Implications for Reionisation

The MUSE Hubble Ultra Deep Field Survey: VII. Fe II* Emission in Star-Forming Galaxies

The MUSE Hubble Ultra Deep Field Survey: VIII. Extended Lyman-alpha Haloes,

The MUSE Hubble Ultra Deep Field Survey: IX. Evolution of Galaxy Merger Fraction up to z ? 6

The MUSE Hubble Ultra Deep Field Survey: Ly-alpha Equivalent Widths at 2.9 < z < 6.6

from EarthSky http://ift.tt/2ijiYVE

Aries? Here’s your constellation

The constellation Aries the Ram. His head is turned backward, looking in the direction of the Pleaides star cluster. Image via Old Book Art image Gallery

The sun – as seen from Earth – passes in front of the constellation Aries the Ram from about April 19 to May 14 every year. Of course, a Northern Hemisphere spring or Southern Hemisphere autumn presents the wrong time of year for viewing the constellation Aries because then the mighty Ram is lost in the sun’s glare. November and December are especially good months for viewing Aries.

Follow the links below to learn more about how to see Aries in the night sky, and about this constellation in the history of astronomy and in mythology.

Best time for seeing Aries the Ram

What is the First Point of Aries?

Aries the Ram in star lore

Sky chart of the constellation Aries the Ram, showing the Pleiades star cluster near the Pisces/Taurus border. Click here for a larger chart

Look for Cassiopeia high over Polaris, the North Star around 8 p.m. local time in early December and 6 p.m. in early January. Then use Cassiopeia to star-hop to Aries by drawing an imaginary line from Polaris, the North Star, and through the star Segin (Epsilon Cassiopeiae).

Not sure how to find the North Star with respect to Cassiopeia in December and January? This chart should help.

Best time for seeing Aries the Ram. The best time to behold the Mighty Ram is at the opposite end of the year, when the Earth is on the other side of the sun. In late October, this constellation rises in the east at sunset, reaches its highest point in the sky at midnight and sets in the west at sunrise.

November and December are especially good months for viewing Aries the Ram in all his starlit majesty, for this constellation shines above the eastern horizon at nightfall and stays out for most of the night. Aries culminates – reaches its highest point in the sky – at about 10 p.m. local time (the time in all time zones) in late November, 8 p.m. local time in late December and 6 p.m. local time in late January.

Aries is not a particularly prominent constellation, so a dark country sky absent of moonlight is most desirable for viewing the Ram at its finest. The three stars depicting the Ram’s bust – Hamal, Sheratan and Mesartim – suddenly brighten in a dark sky, as if someone had turned up the dimmer switch. By the way, a small telescope reveals that Mesartim is a double star.

Fortunately, the head of the Ram is fairly easy to locate. You’ll find it midway between these two signposts: the Pleiades star cluster to the east and the Square of Pegasus to the west. The Ram’s head is actually turned backward, as if admiring the Pleiades – or perhaps his own golden fleece.

You can also star-hop to Aries by drawing an imaginary line from Polaris, the North Star, and through a certain star in the constellation Cassiopeia: Segin (Epsilon Cassiopeiae). You’re seeking for the star at the east end of the famed starlit W or M, as shown on the sky chart at right. It’s a very long hop, more than twice the Polairs/Segin distance. Jump until you land between the Pleiades cluster and the Square of Pegasus.

By definition, the sun resides at the First Point of Aries on the March equinox. This point has a declination of zero degrees and a right ascension of zero degrees. The ecliptic and celestial equator intersect on the March and September equinoxes, and the celestial equator is equal to a declination of 0^o. Image via Wikimedia Commons

What is the First Point of Aries? The First Point of Aries marks the sun’s position in front of the constellations of the Zodiac on the Northern Hemisphere’s spring equinox or Southern Hemisphere’s autumnal equinox. This equinox happens yearly on or near March 20, as the sun crosses the celestial equator, going from south to north.

The First Point of Aries, which is actually in the constellation Pisces nowadays, defines the coordinate system on the celestial sphere. The First Point of Aries always coincides with 0^o right ascension and 0^o declination. Right ascension is the equivalent of longitude here on Earth. Declination on the sky’s dome is the equivalent of latitude.

The First Point of Aries is one of two places on the celestial sphere where the ecliptic and celestial equator intersect. The First Point of Libra resides 180^o east of the First Point of Aries, marking the September equinox point on the celestial sphere.

Because the Earth’s rotational axis wobbles full circle relative to the backdrop stars in about 26,000 years, Polaris doesn’t remain the North Star forever and the equinox points don’t remain fixed relative to the stars of the Zodiac. The March equinox point drifts westward (along the ecliptic) through the constellations of the Zodiac at about one degree (two sun diameters) in 72 years or 30^o in 2160 years.

Hence, the March equinox point passed out of the constellation Aries and into the constellation Pisces in 68 B.C. Even so, we still call this equinox point the First Point of Aries.

Hamal, ancient equinox star

Map showing the ancient Kingdom of Colchis on the eastern shore of the Black Sea. View larger.

Aries the Ram in star lore. In Greek mythology, Aries represents the supernatural Ram that was sent by Zeus to rescue the children of Athamus, the King of Thebes, from political intrigue. Phrixus and his sister Helle were about to meet their demise, but the flying Ram, which could both speak and reason, took them away in the nick of time.

The children held on tight as the Ram flew them away for the safety of Colchis, an ancient kingdom bordering the eastern shore of the Black Sea. Unfortunately, Helle fell into the sea and drowned before reaching their destination. Hellespont – the ancient name for the Dardanelles straight near Istanbul, Turkey – marks the place of her death and was named in her honor.

Phrixus survived the long trip to Colchis. He gave thanks by sacrificing the Ram to Zeus, hanging it in a sacred grove where the fleece turned to gold. Later on, Jason and the Argonauts recovered the Golden Fleece.

Enjoying EarthSky? Sign up for our free daily newsletter today!

Bottom line: How to see the constellation Aries the Ram, plus info about this constellation in the history of astronomy, and in mythology.

Taurus? Here’s your constellation
Gemini? Here’s your constellation
Cancer? Here’s your constellation
Leo? Here’s your constellation
Virgo? Here’s your constellation
Libra? Here’s your constellation
Scorpius? Here’s your contellation
Sagittarius? Here’s your constellation
Capricornus? Here’s your constellation
Aquarius? Here’s your constellation
Pisces? Here’s your constellation
Aries? Here’s your constellation
Birthday late November to early December? Here’s your constellation

from EarthSky http://ift.tt/1vF99yI

The constellation Aries the Ram. His head is turned backward, looking in the direction of the Pleaides star cluster. Image via Old Book Art image Gallery

The sun – as seen from Earth – passes in front of the constellation Aries the Ram from about April 19 to May 14 every year. Of course, a Northern Hemisphere spring or Southern Hemisphere autumn presents the wrong time of year for viewing the constellation Aries because then the mighty Ram is lost in the sun’s glare. November and December are especially good months for viewing Aries.

Follow the links below to learn more about how to see Aries in the night sky, and about this constellation in the history of astronomy and in mythology.

Best time for seeing Aries the Ram

What is the First Point of Aries?

Aries the Ram in star lore

Sky chart of the constellation Aries the Ram, showing the Pleiades star cluster near the Pisces/Taurus border. Click here for a larger chart

Look for Cassiopeia high over Polaris, the North Star around 8 p.m. local time in early December and 6 p.m. in early January. Then use Cassiopeia to star-hop to Aries by drawing an imaginary line from Polaris, the North Star, and through the star Segin (Epsilon Cassiopeiae).

Not sure how to find the North Star with respect to Cassiopeia in December and January? This chart should help.

Best time for seeing Aries the Ram. The best time to behold the Mighty Ram is at the opposite end of the year, when the Earth is on the other side of the sun. In late October, this constellation rises in the east at sunset, reaches its highest point in the sky at midnight and sets in the west at sunrise.

November and December are especially good months for viewing Aries the Ram in all his starlit majesty, for this constellation shines above the eastern horizon at nightfall and stays out for most of the night. Aries culminates – reaches its highest point in the sky – at about 10 p.m. local time (the time in all time zones) in late November, 8 p.m. local time in late December and 6 p.m. local time in late January.

Aries is not a particularly prominent constellation, so a dark country sky absent of moonlight is most desirable for viewing the Ram at its finest. The three stars depicting the Ram’s bust – Hamal, Sheratan and Mesartim – suddenly brighten in a dark sky, as if someone had turned up the dimmer switch. By the way, a small telescope reveals that Mesartim is a double star.

Fortunately, the head of the Ram is fairly easy to locate. You’ll find it midway between these two signposts: the Pleiades star cluster to the east and the Square of Pegasus to the west. The Ram’s head is actually turned backward, as if admiring the Pleiades – or perhaps his own golden fleece.

You can also star-hop to Aries by drawing an imaginary line from Polaris, the North Star, and through a certain star in the constellation Cassiopeia: Segin (Epsilon Cassiopeiae). You’re seeking for the star at the east end of the famed starlit W or M, as shown on the sky chart at right. It’s a very long hop, more than twice the Polairs/Segin distance. Jump until you land between the Pleiades cluster and the Square of Pegasus.

By definition, the sun resides at the First Point of Aries on the March equinox. This point has a declination of zero degrees and a right ascension of zero degrees. The ecliptic and celestial equator intersect on the March and September equinoxes, and the celestial equator is equal to a declination of 0^o. Image via Wikimedia Commons

What is the First Point of Aries? The First Point of Aries marks the sun’s position in front of the constellations of the Zodiac on the Northern Hemisphere’s spring equinox or Southern Hemisphere’s autumnal equinox. This equinox happens yearly on or near March 20, as the sun crosses the celestial equator, going from south to north.

The First Point of Aries, which is actually in the constellation Pisces nowadays, defines the coordinate system on the celestial sphere. The First Point of Aries always coincides with 0^o right ascension and 0^o declination. Right ascension is the equivalent of longitude here on Earth. Declination on the sky’s dome is the equivalent of latitude.

The First Point of Aries is one of two places on the celestial sphere where the ecliptic and celestial equator intersect. The First Point of Libra resides 180^o east of the First Point of Aries, marking the September equinox point on the celestial sphere.

Because the Earth’s rotational axis wobbles full circle relative to the backdrop stars in about 26,000 years, Polaris doesn’t remain the North Star forever and the equinox points don’t remain fixed relative to the stars of the Zodiac. The March equinox point drifts westward (along the ecliptic) through the constellations of the Zodiac at about one degree (two sun diameters) in 72 years or 30^o in 2160 years.

Hence, the March equinox point passed out of the constellation Aries and into the constellation Pisces in 68 B.C. Even so, we still call this equinox point the First Point of Aries.

Hamal, ancient equinox star

Map showing the ancient Kingdom of Colchis on the eastern shore of the Black Sea. View larger.

Aries the Ram in star lore. In Greek mythology, Aries represents the supernatural Ram that was sent by Zeus to rescue the children of Athamus, the King of Thebes, from political intrigue. Phrixus and his sister Helle were about to meet their demise, but the flying Ram, which could both speak and reason, took them away in the nick of time.

The children held on tight as the Ram flew them away for the safety of Colchis, an ancient kingdom bordering the eastern shore of the Black Sea. Unfortunately, Helle fell into the sea and drowned before reaching their destination. Hellespont – the ancient name for the Dardanelles straight near Istanbul, Turkey – marks the place of her death and was named in her honor.

Phrixus survived the long trip to Colchis. He gave thanks by sacrificing the Ram to Zeus, hanging it in a sacred grove where the fleece turned to gold. Later on, Jason and the Argonauts recovered the Golden Fleece.

Enjoying EarthSky? Sign up for our free daily newsletter today!

Bottom line: How to see the constellation Aries the Ram, plus info about this constellation in the history of astronomy, and in mythology.

Taurus? Here’s your constellation
Gemini? Here’s your constellation
Cancer? Here’s your constellation
Leo? Here’s your constellation
Virgo? Here’s your constellation
Libra? Here’s your constellation
Scorpius? Here’s your contellation
Sagittarius? Here’s your constellation
Capricornus? Here’s your constellation
Aquarius? Here’s your constellation
Pisces? Here’s your constellation
Aries? Here’s your constellation
Birthday late November to early December? Here’s your constellation

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Your dog is good for your heart

Image via Marc Fagelson.

EarthSky’s 2018 lunar calendars are here! Get yours while they last.

A team of Swedish scientists used national registries of more than 3.4 million Swedes aged 40 to 80 to study the association between dog ownership and cardiovascular health. Their study shows that dog owners had a lower risk of death due to cardiovascular disease or to other causes during the 12-year follow-up.

Mwenya Mubanga, of Uppsala University, is lead junior author of the study, wich was published November 7, 2017 in the journal Scientific Reports. Mubanga said in a statement:

A very interesting finding in our study was that dog ownership was especially prominent as a protective factor in persons living alone, which is a group reported previously to be at higher risk of cardiovascular disease and death than those living in a multi-person household. Perhaps a dog may stand in as an important family member in the single households.

…Another interesting finding was that owners to dogs from breed groups originally bred for hunting were most protected.

In Sweden, every person carries a unique personal identity number. Every visit to a hospital is recorded in national databases, accessible to researchers after de-identification of data. Even dog ownership registration has been mandatory in Sweden since 2001. These scientists studied whether being registered as a dog-owner was associated with later diagnosis of cardiovascular disease or death from any cause.

Tove Fall is senior author of the study and Associate Professor in Epidemiology at Uppsala University. She said:

These kinds of epidemiological studies look for associations in large populations but do not provide answers on whether and how dogs could protect from cardiovascular disease. We know that dog owners in general have a higher level of physical activity, which could be one explanation to the observed results. Other explanations include an increased well-being and social contacts or effects of the dog on the bacterial microbiome in the owner.

There might also be differences between owners and non-owners already before buying a dog, which could have influenced our results, such as those people choosing to get a dog tending to be more active and of better health.

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Bottom Line: A Swedish study suggests a correlation between dog ownership in a lower risk of death from cardiovascular disease and other causes.

Read more from Uppsala University

from EarthSky http://ift.tt/2iiXuIu

Image via Marc Fagelson.

EarthSky’s 2018 lunar calendars are here! Get yours while they last.

A team of Swedish scientists used national registries of more than 3.4 million Swedes aged 40 to 80 to study the association between dog ownership and cardiovascular health. Their study shows that dog owners had a lower risk of death due to cardiovascular disease or to other causes during the 12-year follow-up.

Mwenya Mubanga, of Uppsala University, is lead junior author of the study, wich was published November 7, 2017 in the journal Scientific Reports. Mubanga said in a statement:

A very interesting finding in our study was that dog ownership was especially prominent as a protective factor in persons living alone, which is a group reported previously to be at higher risk of cardiovascular disease and death than those living in a multi-person household. Perhaps a dog may stand in as an important family member in the single households.

…Another interesting finding was that owners to dogs from breed groups originally bred for hunting were most protected.

In Sweden, every person carries a unique personal identity number. Every visit to a hospital is recorded in national databases, accessible to researchers after de-identification of data. Even dog ownership registration has been mandatory in Sweden since 2001. These scientists studied whether being registered as a dog-owner was associated with later diagnosis of cardiovascular disease or death from any cause.

Tove Fall is senior author of the study and Associate Professor in Epidemiology at Uppsala University. She said:

These kinds of epidemiological studies look for associations in large populations but do not provide answers on whether and how dogs could protect from cardiovascular disease. We know that dog owners in general have a higher level of physical activity, which could be one explanation to the observed results. Other explanations include an increased well-being and social contacts or effects of the dog on the bacterial microbiome in the owner.

There might also be differences between owners and non-owners already before buying a dog, which could have influenced our results, such as those people choosing to get a dog tending to be more active and of better health.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

Bottom Line: A Swedish study suggests a correlation between dog ownership in a lower risk of death from cardiovascular disease and other causes.

Read more from Uppsala University

from EarthSky http://ift.tt/2iiXuIu

Clouds near Australia

Image via NASA.

On October 17, 2017, NASA’s Suomi NPP satellite captured this image of an unusual cloud pattern off the coast of southern Australia.

According to Paul Lainio, a meteorologist at Australia’s Bureau of Meteorology, the pattern was caused by a phenomenon in the atmosphere called gravity waves. Similar to a boat’s wake, which forms as water is pushed upward by the boat and pulled downward again by gravity, these clouds are formed by the rise and fall of air columns. As the wave moves along the cloud band, the wave peaks appear cloudy and the troughs appear cloud-free. In this case, the gravity waves developed as a result of instability on the flank of a strong jet stream moving ahead of the cold front. Lainio said:

This type of effect is relatively unusual since it requires a strong anticyclonic-curved jet that develops gravity waves of sufficient magnitude. The gravity waves are the atmosphere’s way of restoring balance, and they usually don’t last for lengthy periods.

Bottom line: Satellite image of cloud pattern off southern Australia.

Read more from NASA

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Image via NASA.

On October 17, 2017, NASA’s Suomi NPP satellite captured this image of an unusual cloud pattern off the coast of southern Australia.

According to Paul Lainio, a meteorologist at Australia’s Bureau of Meteorology, the pattern was caused by a phenomenon in the atmosphere called gravity waves. Similar to a boat’s wake, which forms as water is pushed upward by the boat and pulled downward again by gravity, these clouds are formed by the rise and fall of air columns. As the wave moves along the cloud band, the wave peaks appear cloudy and the troughs appear cloud-free. In this case, the gravity waves developed as a result of instability on the flank of a strong jet stream moving ahead of the cold front. Lainio said:

This type of effect is relatively unusual since it requires a strong anticyclonic-curved jet that develops gravity waves of sufficient magnitude. The gravity waves are the atmosphere’s way of restoring balance, and they usually don’t last for lengthy periods.

Bottom line: Satellite image of cloud pattern off southern Australia.

Read more from NASA

from EarthSky http://ift.tt/2i1k4lb

Moon near Uranus on November 29

Tonight – November 29, 2017 – as the moon travels in front of the constellations of the zodiac, it’ll appear in the general direction of the planet Uranus. Tonight is a good night to locate the constellation Pisces, which is behind the moon and Uranus now. Then you can search for the stars of Pisces again – and maybe find Uranus, too – in a dark country sky during the second and third week of December, after the moon has dropped out of the evening sky.

Near-infrared view of the ice giant planet Uranus, its rings and some of its moons. Image via European Southern Observatory.

What will you see of Pisces on this moonlit night? You might at least pick out the Circlet, which is a noticeable asterism within Pisces. (See the sky chart of the constellation Pisces below.)

Most stargazers need binoculars, a moon-free night and a detailed sky chart, like the one here via Sky & Telescope to see Uranus. This world is bigger than Earth, but it’s also 20 times farther from the sun than Earth is from the sun.

If you’re familiar with the Great Square of Pegasus and the Circlet of Pisces, make use of these star patterns to map out the general vicinity of Uranus. Uranus resides in front of the constellation Pisces and near the ecliptic.

Sky chart of the constellation Pisces

The constellation Pisces is best seen on a moonless night. Many stargazers use the Square of Pegasus to locate Pisces. Click here for a sky chart showing you Uranus’ position in Pisces for 2017.

This detailed sky chart is your ticket to finding the planet Uranus.

Uranus is the seventh planet outward from the sun. Even on a moonless night, Uranus appears no brighter than the faintest visible stars.

The moon – presently in front of the constellation Pisces – is waxing toward full and will be in front of the constellation Taurus on the night of the full moon.

The moon with clouds and a contrail. Faint planet Uranus is at the arrow tip. Photo taken November 21, 2015 by Nikolaos Pantazis in Greece.

Bottom line: On the night of November 29, 2017, the moon is located along our line of sight to the faint planet Uranus. But don’t expect to see Uranus in the moon’s glare.

Easily locate stars and constellations during any day and time with EarthSky’s Planisphere.

from EarthSky http://ift.tt/1N1h4L4

Tonight – November 29, 2017 – as the moon travels in front of the constellations of the zodiac, it’ll appear in the general direction of the planet Uranus. Tonight is a good night to locate the constellation Pisces, which is behind the moon and Uranus now. Then you can search for the stars of Pisces again – and maybe find Uranus, too – in a dark country sky during the second and third week of December, after the moon has dropped out of the evening sky.

Near-infrared view of the ice giant planet Uranus, its rings and some of its moons. Image via European Southern Observatory.

What will you see of Pisces on this moonlit night? You might at least pick out the Circlet, which is a noticeable asterism within Pisces. (See the sky chart of the constellation Pisces below.)

Most stargazers need binoculars, a moon-free night and a detailed sky chart, like the one here via Sky & Telescope to see Uranus. This world is bigger than Earth, but it’s also 20 times farther from the sun than Earth is from the sun.

If you’re familiar with the Great Square of Pegasus and the Circlet of Pisces, make use of these star patterns to map out the general vicinity of Uranus. Uranus resides in front of the constellation Pisces and near the ecliptic.

Sky chart of the constellation Pisces

The constellation Pisces is best seen on a moonless night. Many stargazers use the Square of Pegasus to locate Pisces. Click here for a sky chart showing you Uranus’ position in Pisces for 2017.

This detailed sky chart is your ticket to finding the planet Uranus.

Uranus is the seventh planet outward from the sun. Even on a moonless night, Uranus appears no brighter than the faintest visible stars.

The moon – presently in front of the constellation Pisces – is waxing toward full and will be in front of the constellation Taurus on the night of the full moon.

The moon with clouds and a contrail. Faint planet Uranus is at the arrow tip. Photo taken November 21, 2015 by Nikolaos Pantazis in Greece.

Bottom line: On the night of November 29, 2017, the moon is located along our line of sight to the faint planet Uranus. But don’t expect to see Uranus in the moon’s glare.

Easily locate stars and constellations during any day and time with EarthSky’s Planisphere.

from EarthSky http://ift.tt/1N1h4L4