Bernie's What's Up

WHAT’S UP IN APRIL

By Bernie Reim

The word April is derived from Aprilis, which means to open. That is exactly what the buds and flowers will do this month as our hemisphere turns more and more towards the sun, causing steadily increasing daylight during this first full month of spring.

This month is notoriously unpredictable, as T.S. Eliot says in his famous poem, “The Wasteland”, “April is the cruelest month.” We can count on what constellations will be visible, but not the conditions. Notice that the brightest stars of winter in the winter hexagon are now slipping lower into the western horizon even as the top of the summer triangle is beginning to rise over the eastern horizon.

The later you stay up in spring, the more of a summer sky reveals itself. The whole sky appears to shift eastward at the rate of two hours per month. So if you look at the sky at 10 pm in the middle of April that is the same sky you would see at 8 pm during the middle of May. That is because a star will rise 4 minutes earlier each day, which amounts to 120 minutes or 2 hours earlier each month. The sidereal day is only 23 hours and 56 minutes long. The earth rotates in the same direction on its axis as it revolves around the sun, which is counterclockwise as seen from the northern hemisphere. Since we are revolving around the sun at the rate of 67,000 mph or 18.6 miles per second, the sun appears to move eastward at the rate of about one degree per day against the fixed background of stars. The rotation rate of earth varies based on your latitude. At the equator it is just over 1,000 mph (25,000 miles divided by 24 hours) and at this latitude of about 43 degrees north, it rotates at around 750 mph, which also happens to be about the speed of sound.

The highlights this month include nice conjunctions of the moon and Jupiter in the morning sky, the moon and Saturn in the evening sky, and the Pleiades, the moon and Venus in the western sky at dusk.

The king of the planets will rise around 11 pm by the end of April. Look for Jupiter in the morning sky one hour before sunrise about 10 degrees above and to the left of Antares, the brightest star in Scorpius and, at 700 times the diameter of our sun, one of the largest stars in our whole galaxy of around 200 billion stars. The waning gibbous moon will pass just below Antares and Jupiter on the mornings of the 7th, 8th, and 9th.

As the moon continues to fade, it will pass near Mars low in the east southeastern morning sky about 45 minutes before sunrise on the mornings of April 13 and 14.

Then we switch to the evening sky to watch the slender waxing crescent moon pass near the Pleiades, the Hyades, and Venus on the evenings of April 18, 19 and 20. The best night will be Thursday night the 19th, when the crescent moon will be just a few degrees above the Pleiades and a few degrees below brilliant Venus.

The Pleiades, or the Seven Sisters, also known as Subaru in Japanese, are a related cluster of about 500 young stars located around 400 light years away. That means that the light you are seeing from that cluster left there just as Galileo started looking through his first telescope in 1609 and began making many great, earth-shaking discoveries that forever changed the way humans perceived their solar system and effectively launched the scientific age.

The average age of those 500 young stars is around 100 million years. That may seem old, but that is nearly 50 times younger than our own earth and sun. The earth was certainly a very different place when those stars in the Pleiades were born. That was during the height of the Jurassic Period when dinosaurs reigned supreme.

We end this celestial tour with the waxing gibbous moon passing near Saturn and Regulus in Leo on the evenings of April 24 and 25. Saturn will end its retrograde or westward motion in the sky away from Leo on April 19. Through a telescope you will notice that its rings are tilted at 15 degrees, but they are closing more and more and will not be that far open again for five years. Now 2 months past opposition, Saturn is fading out and getting smaller in our sky again. At 0.3 magnitude, it is about 10 times fainter than Jupiter and about 50 times fainter than Venus.

April 2. The full moon is at 1:15 p.m. This is also called the Pink, Seed, Grass, or Egg Moon.

April 3. The moon is at apogee, or farthest from the earth at 406,329 km.

April 5. Jupiter ends its prograde, or direct, eastward motion today. It will begin its retrograde loop today, which will not end until August 7th. Jupiter will reach opposition in 2 months, on June 5, when it will rise at sunset.

April 6. Pioneer 11 was launched on this day in 1973. It took great pictures of Jupiter in 1974 and Saturn in 1979. By 1995, when we lost contact, it was already 6.5 billion km away, which is about the number of people living on Earth today. Both Pioneer 10 and 11 carry a plaque which contains a message from humankind. It is heading out of our solar system towards the constellation of Aquila the Eagle, but it will take 4 million years to get there.

April 7. The Compton Gamma Ray Observatory was deployed on this day in 1991. This highly successful mission ended in June of 2000 as the telescope reentered the atmosphere. It saw about one highly energetic gamma ray burst per day during its 9 years of observations.

April 10. Last quarter moon is at 2:04 p.m.

April 15. Wilbur Wright was born on this day in 1867. The Wright brother’s first flight was in December of 1903, less than 66 years before we went to the moon.

April 17. New moon is at 7:36 am. The moon is at perigee at 357,135 km today.

April 19. The waxing crescent moon will be just below and to the right of Venus and above and to the left of the Pleiades this evening.

April 22. The Lyrid Meteor Shower peaks this Sunday morning. Caused by Comet Thatcher, you can expect 15 to 20 meteors per hour to emanate from the sky near Vega in the constellation of Lyra this morning. This bright, zero magnitude star was our North Star 13,000 years ago and will once again be our North Star in 13,000 more years. Our polar axis is continually changing because the earth is wobbling like a top as its spin rate slows down. This process is called precession of the equinoxes. In just 2000 years, Gamma Cephei, the star at the bottom of the upside down house that is Cepheus the King, will be our North Star. By coincidence, Gamma Cephei happened to be one of over 100 stars discovered so far that have planets orbiting around them. When Vega once again becomes our North Star, the sky will look quite different at this latitude, since we will gain some southern constellations including the Southern Cross. In turn, we will lose the lower half of Orion and the Winter Hexagon.

April 24. First quarter moon is at 2:36 a.m.

Here is Bernie Riem's What's Up column:
WHAT’S UP IN APRIL By Bernie Reim The word April is derived from Aprilis, which means to open. That is exactly what the buds and flowers will do this month as our hemisphere turns more and more towards the sun, causing steadily increasing daylight during this first full month of spring. This month is notoriously unpredictable, as T.S. Eliot says in his famous poem, “The Wasteland”, “April is the cruelest month.” We can count on what constellations will be visible, but not the conditions. Notice that the brightest stars of winter in the winter hexagon are now slipping lower into the western horizon even as the top of the summer triangle is beginning to rise over the eastern horizon. The later you stay up in spring, the more of a summer sky reveals itself. The whole sky appears to shift eastward at the rate of two hours per month. So if you look at the sky at 10 pm in the middle of April that is the same sky you would see at 8 pm during the middle of May. That is because a star will rise 4 minutes earlier each day, which amounts to 120 minutes or 2 hours earlier each month. The sidereal day is only 23 hours and 56 minutes long. The earth rotates in the same direction on its axis as it revolves around the sun, which is counterclockwise as seen from the northern hemisphere. Since we are revolving around the sun at the rate of 67,000 mph or 18.6 miles per second, the sun appears to move eastward at the rate of about one degree per day against the fixed background of stars. The rotation rate of earth varies based on your latitude. At the equator it is just over 1,000 mph (25,000 miles divided by 24 hours) and at this latitude of about 43 degrees north, it rotates at around 750 mph, which also happens to be about the speed of sound. The highlights this month include nice conjunctions of the moon and Jupiter in the morning sky, the moon and Saturn in the evening sky, and the Pleiades, the moon and Venus in the western sky at dusk. The king of the planets will rise around 11 pm by the end of April. Look for Jupiter in the morning sky one hour before sunrise about 10 degrees above and to the left of Antares, the brightest star in Scorpius and, at 700 times the diameter of our sun, one of the largest stars in our whole galaxy of around 200 billion stars. The waning gibbous moon will pass just below Antares and Jupiter on the mornings of the 7th, 8th, and 9th. As the moon continues to fade, it will pass near Mars low in the east southeastern morning sky about 45 minutes before sunrise on the mornings of April 13 and 14. Then we switch to the evening sky to watch the slender waxing crescent moon pass near the Pleiades, the Hyades, and Venus on the evenings of April 18, 19 and 20. The best night will be Thursday night the 19th, when the crescent moon will be just a few degrees above the Pleiades and a few degrees below brilliant Venus. The Pleiades, or the Seven Sisters, also known as Subaru in Japanese, are a related cluster of about 500 young stars located around 400 light years away. That means that the light you are seeing from that cluster left there just as Galileo started looking through his first telescope in 1609 and began making many great, earth-shaking discoveries that forever changed the way humans perceived their solar system and effectively launched the scientific age. The average age of those 500 young stars is around 100 million years. That may seem old, but that is nearly 50 times younger than our own earth and sun. The earth was certainly a very different place when those stars in the Pleiades were born. That was during the height of the Jurassic Period when dinosaurs reigned supreme. We end this celestial tour with the waxing gibbous moon passing near Saturn and Regulus in Leo on the evenings of April 24 and 25. Saturn will end its retrograde or westward motion in the sky away from Leo on April 19. Through a telescope you will notice that its rings are tilted at 15 degrees, but they are closing more and more and will not be that far open again for five years. Now 2 months past opposition, Saturn is fading out and getting smaller in our sky again. At 0.3 magnitude, it is about 10 times fainter than Jupiter and about 50 times fainter than Venus. April 2. The full moon is at 1:15 p.m. This is also called the Pink, Seed, Grass, or Egg Moon. April 3. The moon is at apogee, or farthest from the earth at 406,329 km. April 5. Jupiter ends its prograde, or direct, eastward motion today. It will begin its retrograde loop today, which will not end until August 7th. Jupiter will reach opposition in 2 months, on June 5, when it will rise at sunset. April 6. Pioneer 11 was launched on this day in 1973. It took great pictures of Jupiter in 1974 and Saturn in 1979. By 1995, when we lost contact, it was already 6.5 billion km away, which is about the number of people living on Earth today. Both Pioneer 10 and 11 carry a plaque which contains a message from humankind. It is heading out of our solar system towards the constellation of Aquila the Eagle, but it will take 4 million years to get there. April 7. The Compton Gamma Ray Observatory was deployed on this day in 1991. This highly successful mission ended in June of 2000 as the telescope reentered the atmosphere. It saw about one highly energetic gamma ray burst per day during its 9 years of observations. April 10. Last quarter moon is at 2:04 p.m. April 15. Wilbur Wright was born on this day in 1867. The Wright brother’s first flight was in December of 1903, less than 66 years before we went to the moon. April 17. New moon is at 7:36 am. The moon is at perigee at 357,135 km today. April 19. The waxing crescent moon will be just below and to the right of Venus and above and to the left of the Pleiades this evening. April 22. The Lyrid Meteor Shower peaks this Sunday morning. Caused by Comet Thatcher, you can expect 15 to 20 meteors per hour to emanate from the sky near Vega in the constellation of Lyra this morning. This bright, zero magnitude star was our North Star 13,000 years ago and will once again be our North Star in 13,000 more years. Our polar axis is continually changing because the earth is wobbling like a top as its spin rate slows down. This process is called precession of the equinoxes. In just 2000 years, Gamma Cephei, the star at the bottom of the upside down house that is Cepheus the King, will be our North Star. By coincidence, Gamma Cephei happened to be one of over 100 stars discovered so far that have planets orbiting around them. When Vega once again becomes our North Star, the sky will look quite different at this latitude, since we will gain some southern constellations including the Southern Cross. In turn, we will lose the lower half of Orion and the Winter Hexagon. April 24. First quarter moon is at 2:36 a.m.