Tag: astronomy

Astronomy, Sky Watching, Feature

2019-2020: Mars Until it Retrogrades
Mars (NASA Photo)

 

This chart shows the rising time differences for the rising times of the bright planets and stars near the ecliptic and sunrise for up to five hours before sunrise. The moon’s time differences are displayed in circles. The setting times of Jupiter and Saturn are graphed compared to sunrise. (Data from the U.S. Naval Observatory)

(This article was first published in the Northern Lights Fall Issue)

Mars begins an apparition that takes it to an opposition on October 12, 2020, 808 days following its 2018 perihelic opposition. The opposition, that will be highlighted in a future issue, brings Mars to its closest approach about a week before opposition. On October 6, the closest approach is 35.8 million miles, about 8% farther away than the preceding close passing. This corresponds to a smaller disk presented through a telescope.

The chart above, compiled with data from the U.S. Naval Observatory, shows the morning sky for 13 months beginning August 1, 2019, from Chicago, Illinois. Time intervals are noted on the chart and in the daily notes. Specific times are for Chicago, Illinois. To observe locally, refer to local sources for the times of sunrise and sunset; apply the time differentials in the notes.

The chart displays the time differences between the time of sunrise and the rising times for other planets, moon, and bright stars near the ecliptic, for up to five hours before sunrise. The moon’s rising time difference is displayed with circles. The setting time differences for Jupiter and Saturn, compared to sunrise, are displayed as well. The three phases of twilight are graphed compared to sunrise, and conjunctions are identified. The chart also notes several dates when the moon is near the bright planets.

Mars, Jupiter, and Saturn have oppositions that occur within 91 days in 2020. The interest in the Mars opposition adds a highlight to the Great Conjunction of Jupiter and Saturn that occurs late in the year. Such Jupiter – Saturn conjunctions occur about every 20 years.

The apparent sizes of Mars (in arcseconds) at its oppositions are graphed from 1930 to 2050. The larger apparent sizes occur when Mars is near perihelion and smallest when it is near aphelion. The time between oppositions for Mars, Jupiter, and Saturn are displayed for some oppositions (in days). The Great Conjunctions of Jupiter and Saturn that occur about every 20 years are displayed with yellow stars, including the time (in days) between oppositions of the two planets.

Mars’ apparent size at opposition (24.3”) is 8% smaller than the 2018 perihelic opposition and 11% smaller than the 2003 close opposition. This was described above with the close approach that is farther away in 2020 than the most recent perihelic opposition. The chart above displays the apparent size of Mars at its oppositions from 1930 through 2050. The twenty-year intervals of the Jupiter – Saturn Great Conjunction are displayed with yellow stars along with the time interval between their oppositions. For several Mars’ oppositions, the time intervals are noted for the Bright Outer Planets – Mars, Jupiter, and Saturn.

In this summary the events before opposition include monthly passages of the moon that highlight the beginning of a lunar occultation that is easier to view in the Western US, conjunctions with Jupiter, Pluto, Saturn, Ceres, and Neptune.

The apparition began with Mars’ conjunction with the sun on September 2, 2019. While dim, it began a slow crawl into the morning sky. By mid-month Mars was rising at Civil Twilight when the sun was 6° below the horizon.

At the beginning of October, the Red Planet (m = 1.8) is just above the eastern horizon, 45 minutes before sunrise, although it is a binocular object. The planet continues to rise earlier, Nautical Twilight (sun’s altitude = −12°) on October 6. Throughout October it rises earlier, rising at Astronomical Twilight on October 25. In the summary, each entry includes the planet’s magnitude, apparent size, distance from Earth in Astronomical Units, and difference between the planet’s rising time and sunrise, stated in minutes. This time changes in the summary on July 1, 2020, when the difference noted is between sunset and the rising of Mars. Here’s what to look for:

  • October 26: (1.8, 3.7”, 2.56 AU, 94m) Forty-five minutes before sunrise, the waning crescent moon (27.6 days old, 4% illuminated) is 5.6° to the upper left of Mars, about 8° up in the east-southeast. At this time, Mars is 4.5° below Gamma Virginis (γ Vir, m 3.4). Use a binocular.
  • November 10: (1.8, 3.8”, 2.50 AU, 122m) One hour before sunrise, Mars, about 9° up in the east-southeast, passes 2.8° to the upper left of Spica (α Vir, m = 1.0).
  • November 24: (1.7, 3.9”, 2.42 AU, 146m) One hour before sunrise, the waning crescent moon (27.3d, 6%) is 3.7° to the left of Mars, 15° up in the east-southeast. At the same time Mars is 9.5° to the upper right of Mercury (m = −0.4). Tomorrow morning, at the closest approach, the planets have about the same separation, although the gap is neither a conjunction nor a quasi-conjunction.
  • November 25: (1.7, 3.9”, 2.42 AU, 148m) One hour before sunrise, Mars is 14° up in the southeast, 9.5° to the upper right of bright Mercury (m = −0.3), 7° in altitude. The thin crescent moon (28.3d, 2%) is 5.5° to the lower left of Mercury. You’ll need a clear horizon to see the moon. It’s only 3° in altitude.
  • November 30: (1.7, 3.9”, 2.39 AU, 156m) One hour before sunrise, Mars, 15° in altitude in the southeast, is 0.2° to the lower left of Lambda Virginis (λ Vir, m = 2.8).

December 2019

As the year closes, Mars continues its eastward march. Early in the month, bright Mercury is to the lower left of Mars. Still over 2 Astronomical Units from Earth, Mars moves through Libra and between the pincers of the Scorpion. The planet rises about 3 hours before sunrise, but it’s low altitude and southerly location may send you on a chase to find a clear horizon.

  • December 1: (1.7, 3.9”, 2.38 AU, 157m) Mars moves into Libra, 7.3° to the upper right of Zubenelgenubi (α Lib, m = 2.8). Sixty minutes before sunrise, Mars is about 15° up in the southeast.
  • December 12: (1.7, 4.0”, 2.32 AU, 174m) One hour before sunrise, Mars, over 17° up in the southeast, passes 0.2° to the upper left of Zubenelgenubi.
  • December 18: (1.6, 4.1”, 2.28 AU, 181m) One hour before sunrise, Mars, nearly 18° up in the southeast, is 0.7° to the lower right of Nu Librae (ν Lib, m =5.2). Use a binocular to see the pair.
  • December 21: (1.6, 4.2”, 2.25 AU, 184m) One hour before sunrise, Mars, 18° up in the southeast, is 2.3° to the upper left of Iota Librae (ι Lib, m = 4.5).
  • December 22: (1.6, 4.2”, 2.25 AU, 185m) One hour before sunrise, Mars, 18° in altitude in the southeast, is over 8° to the lower left of the waning crescent moon (25.7d, 15%). The moon is above a line that connects Zubenelgenubi and Zubeneschamali (β Lib, m = 2.6). The lunar crescent is 3.5° to the upper left of Zubenelgenubi.
  • December 23: (1.6, 4.2”, 2.24 AU, 191m) One hour before sunrise, Mars, 18° up in the southeast, is 6° to the upper right of the crescent moon (26.8d, 8%).

January 2020

As the New Year breaks, Mars is an unimpressive “star” low in the southeast as sunrise approaches, rising about 4 a.m. CST. It continues to move through Libra and Scorpius and into southern Ophiuchus. At mid-month it passes north of its Rival, Antares.

Notice on the rising chart above that the time differential between the rising of Mars and sunrise decreases from late January through early-April. The declination of the sun is greater than Mars’ position.  The sun is moving toward the vernal equinox while Mars is approaching the ecliptic’s lowest point. The basic principle is that the farther north an object the earlier it rises. During January and February, the time interval between sunrise and Mars rising decreases nearly 20 minutes. This is reflected in the dip the Mars rising line takes on the chart. The differential increases after Mars moves farther north in declination.

  • January 7, 2020: (1.5, 4.4”, 2.14 AU, 196m) One hour before sunrise, Mars, 19° up in the southeast, is 1° to the right of Graffias (β Sco, m = 2.5). Mars enters Scorpius today and moves through in only 8 days.
  • January 8: (1.5, 4.4”, 2.13 AU, 197m) One hour before sunrise, Mars, over 18° up in the southeast, passes 0.7° below Graffias.
  • January 9: (1.5, 4.4”, 2.12 AU, 197m) One hour before sunrise, Mars, over 18° up in the southeast, is still near Graffias, passing 0.1° from Omega1 Scorpii (ω1 Sco, m = 3.9). Use a binocular to see the planet with the dimmer starfield.
  • January 15: (1.5, 4.5”, 2.08 AU, 198m) Mars moves into Ophiuchus. It crosses the constellation in 27 days. One hour before sunrise, Mars is over 18° in altitude in the southeast, 1.8° to the upper right of Omega Ophiuchi (ω Oph, m = 4.4).
  • January 18: (1.5, 4.6”, 2.05 AU, 199m) One hour before sunrise, Mars, over 18° up in the southeast, is 4.7° to the upper left of Antares (α Sco, m = 1.0). At the same time, Mars is 0.4° below Omega Ophiuchi. View the star and Mars in the growing twilight with a binocular.
  • January 20: (1.4, 4.6”, 2.04 AU, 198m) One hour before sunrise, Mars is 18° up in the southeast, 3.9° to the lower left of the crescent moon (25.2d, 19%).
  • January 21: (1.4, 4.6”, 2.03 AU, 199m) One hour before sunrise, Mars, 18° up in the southeast, is over 9° to the upper right of the moon (26.2d, 11%).
  • January 24: (1.4, 4.7”, 2.00 AU, 198m) Mars is 2.0 Astronomical Units from Earth. One hour before sunrise, the Red Planet is 18° up in the southeast, 6.3° to the upper left of Antares.

February 2020

During February, Mars moves from Ophiuchus into Sagittarius, through the rich galactic background of our galaxy’s nucleus region. Use a binocular to track the planet’s motion. After mid-month, the moon occults Mars in a bright sky as sunrise approaches. Mars heads toward conjunctions with Jupiter, Pluto, and Saturn next month. Watch the gaps close during February as the Bright Outer Planets appear above the southeast horizon before sunrise.

  • February 1: (1.4, 4.8”, 1.94 AU, 197m) Mars moves south of the ecliptic. One hour before sunrise, find it about 18° up in the southeast.
  • February 2: (1.3, 4.8”, 1.93 AU, 196m) One hour before sunrise, Mars, about 18° up in the southeast, is 1° above Omicron Ophiuchi (ο Oph, m = 5.1).
  • February 4: (1.3, 4.9”, 1.92 AU, 195m) One hour before sunrise, Mars is over 17° in altitude in the southeast. It is 1.8° to the upper left of Theta Ophiuchi (θ Oph, m = 3.2).
  • February 5: (1.3, 4.9”, 1.91 AU, 194m) One hour before sunrise, Mars, over 17° up in the southeast, is 0.9° to the upper left of 44 Ophiuchi (44 Oph, m = 4.2).
  • February 6: (1.3, 4.9”, 1.90 AU, 194m) Mars rises at its most southerly rising azimuth, 122°, until March 5, 2020.
  • February 7: (1.3, 5.0”, 1.90 AU, 194m) One hour before sunrise, Mars, about 17° in altitude in the southeast, is 0.6° to the upper left of 51 Ophiuchi (51 Oph, m = 4.8).
  • February 9: (1.3, 5.0”, 1.88 AU, 193m) Mars is about 20° to the upper left of Jupiter (m = −1.9), 7° up in the southeast, one hour before sunrise.
  • February 11: (1.3, 5.0”, 1.86 AU, 192m) Mars moves into Sagittarius. It begins to approach the bright nebulae and rich star field above the Teapot of Sagittarius. Use low powers to view the planet and the starry background. As the moon approaches the region during the next week, watch Mars move between the Lagoon Nebula (M8, NGC 6523) and the Trifid Nebula (M20, NGC 6514). Mars crosses the constellation in 50 days.
  • February 17: (1.2, 5.2”, 1.81 AU, 189m) One hour before sunrise, Mars, nearly 17° up in the southeast, is about 13° to the lower left of the moon (23.6d, 33%).
  • February 18: (1.2, 5.2”, 1.81 AU, 189m) One hour before sunrise, the crescent moon (24.6d, 24%), about 17° up in the southeast, is 0.4° to the right of Mars. As sunrise approaches, the moon inches toward the planet. If you can track Mars into a brighter sky, the moon occults it a few minutes after 6 a.m. CST, about 35 minutes before sunrise in Chicago. Observers in the Western U.S. see the moon occult Mars in a darker sky.
  • February 26: (1.1, 5.4”,1.74 AU, 185m) One hour before sunrise, Mars, 16° up in the southeast, passes 1.8° to the upper left of Kaus Borealis (λ Sgr, m =2.8), the star at the top of the lid of the Teapot of Sagittarius.
March 20: Mars passes 0.6° to the lower right of Jupiter. Locate the planets in the southeast about an hour before sunrise.

March 2020

Mars marches eastward in Sagittarius, above the Teapot’s handle, and continues to rise earlier. By month’s end, the planet rises before 4 a.m. CDT, as the clock advances one hour on March 8. The gaps to Jupiter, Pluto, and Saturn close as Mars passes the planetary trio this month.

  • March 1: (1.1, 5.5”, 1.70 AU, 183m) One hour before sunrise, Mars, 16° up in the southeast, is 10° to the upper right of Jupiter (m = −2.0).
  • March 5: (1.1, 5.6”, 1.67 AU, 180m) One hour before sunrise, Mars, 16° up in the southeast, passes 2.9° to the upper left of Nunki (σ Sgr, m = 2.0) and appears nearly 8° to the upper right of Jupiter.
  • March 11: (1.0, 5.8”, 1.62 AU, 178m) One hour before sunrise, Mars, 16° up in the southeast, is 4.9° to the upper right of Jupiter. Gaps until the Jupiter – Mars conjunction: Mar 12, 4.3°; Mar 13, 3.7°; Mar 14, 3.3°; Mar 15, 2.7°; Mar 16, 2.2°; Mar 17, 1.7°, Mars to the right of Jupiter; Mar 18, 1.2°; Mar 19, 0.9°.
  • March 15: (1.0, 5.9”, 1.59 AU, 177m) One hour before sunrise, Mars, 16° up in the southeast, is 10° to the upper right of Saturn (m = 0.7).
  • March 18: (0.9, 6.0”, 1.56 AU, 174m) The crescent moon (24.1d, 29%) joins the scene with Jupiter and Mars. The trio makes a small triangle, the moon is 2.4° to the lower right of Jupiter and 2.2° to the lower left of Mars.

 

  • March 20: (0.9, 6.0”, 1.55 AU, 174m) Jupiter – Mars conjunction! Mars is 0.6° to the lower right of Jupiter. The gaps after the conjunction as Mars moves away from Jupiter: Mar 21, 0.9°; Mar 22, 1.3°; Mar 23, 1.7°; Mar 24, 2.3°; Mar 25, 2.7°; Mar 26, 3.4°; Mar 27, 3.9°; Mar 28, 4.5°; Mar 29, 5.0°. The next Jupiter – Mars conjunction is May 29, 2022 in the morning sky. At that conjunction the sky has 4 bright planets – Venus, Jupiter, Mars, and Saturn – in the southeastern sky. The moon is nearby, a few days before the closest Jupiter – Mars passage. This morning the Mars – Saturn gap is 7.1°.
  • March 23: (0.9, 6.1”, 1.52 AU, 174m) Mars passes 0.1° to the lower left of Pluto (m = 14.3). At the beginning of morning twilight, Mars is about 12° up in the southeast. This is clearly a stretch to see this conjunction. A big scope and ideal sky conditions are needed to locate the distant world near Mars.
  • March 26: (0.8, 6.2”, 1.50 AU, 173m) Mars is nearly equidistant from the two bright giant planets, although Mars is below a line that connects Jupiter and Saturn. One hour before sunrise, Mars, 15° up in the southeast, is 3.3° to the lower left of Jupiter and 3.2° to the upper right of Saturn. The Jupiter – Saturn gap is 6.4°.
March 31: Mars passes 0.9° to the lower right of Saturn. The planets are in the southeast about an hour before sunrise.
  • March 31: (0.8, 6.4”, 1.46 AU, 172m) Mars – Saturn conjunction! One hour before sunrise, Mars, 16° up in the southeast is 0.9° to the lower right of Saturn. The Mars – Saturn gap grows after the conjunction: Apr 1, 1°; Apr 2, 1.4°; Apr 3, 1.9°; Apr 4, 2.5°; Apr 5, 3.1°; Apr 6, 3.7°; Apr 7, 4.3°; Apr 8, 5.0°. This morning gap to Jupiter is 6.1°. Mars moves into Capricornus.

April 2020

Mars is now moving away from Jupiter and Saturn and through the starfield of Capricornus. Continue to track it with low powers as it passes dimmer stars. It has a close appearance with the moon at mid-month. By month’s end the planet rises before 3 a.m. CDT.

  • April 5: (0.7, 6.6”, 1.42 AU, 172m) One hour before sunrise, Mars, nearly 16° up in the southeast, is 5.1° to the lower right of Beta Capricorni (m = 3.0). Look for Saturn and Jupiter nearby.
  • April 7: (0.7, 6.7”, 1.41 AU, 172m). One hour before sunrise, Mars is 10° to the lower left of Jupiter and over 4° to the lower left of Saturn.
  • April 15: (0.6, 7.0”, 1.34 AU, 173m) One hour before sunrise, Mars, 16° up in the southeast, is nearly 10° to the left of the thick crescent moon (22.0d, 45%). At the same time, the moon is 3.3° below Saturn. This morning Jupiter is 5.5° to the upper right of Saturn and nearly 15° to the upper right of Mars.
  • April 16: (0.6, 7.0”, 1.34 AU, 173m) One hour before sunrise, Mars, over 16° up in the southeast, is 3.8° to the upper right of the crescent moon (23.0d, 36%). Mars is 10° to the lower left of Saturn.
  • April 20: (0.5, 7.2”, 1.30 AU, 174m) One hour before sunrise, Mars, nearly 17° up in the southeast, is 0.8° below Theta Capricorni (θ Cap, m = 4.0). In the brightening sky, use a binocular to see the star with Mars.
  • April 23: (0.5, 7.3”, 1.28 AU, 175m) One hour before sunrise, Mars, about 17° up in the southeast, is nearly 15° to the lower left of Saturn. Meanwhile, the Jupiter – Saturn gap is 5.1°.
  • April 25: (0.5, 7.4”, 1.27 AU, 177m) One hour before sunrise, Mars, over 17° up in the southeast, is 0.2° to the lower right of Iota Cap (ι Cap, m = 4.2). Optical assistance helps see Mars’ close proximity to the star.

May 2020

Mars moves from Capricornus into the dim star field of Aquarius early in the month, brightening about 45% as it nears 1.0 Astronomical Unit away. The planet is about 40 times brighter than the stars it passes during the month. Continue to use low power to track the planet on its eastward march. The moon passes at mid-month, although about a degree farther away than in April. The planet passes Ceres late in the month.  As April closes, Mars rises before 2 a.m.

  • May 1: (0.4, 7.7”, 1.22 AU, 180m) Ninety minutes before sunrise, Mars, 14° up in the southeast, 0.9° above Gamma Capricorni (γ Cap, m = 3.6).
  • May 4: (0.4, 7.8”, 1.20 AU, 183m) Mars is 1.0° to the upper left of Delta Capricorni (δ Cap, m = 2.8), 90 minutes before sunrise. The planet is over 14° up in the southeast.
  • May 9: (0.3, 8.0”, 1.16 AU, 187m) Mars moves into Aquarius. Ninety minutes before sunrise, locate it nearly 16° in altitude in the southeast. Mars crosses the constellation in 47 days.
  • May 11: (0.3, 8.1”, 1.14 AU, 188m) About 90 minutes before sunrise, Mars, about 16° up in the southeast, passes 0.3° to the upper right of Iota Aquarii. (ι Aqr, m = 4.2).
  • May 14: (0.2, 8.3”, 1.13 AU, 192m) About 90 minutes before sunrise, Mars, nearly 17° up in the southeast, is over 9° to the upper left of the slightly gibbous moon (21.3d, 52%).
  • May 15: (0.2, 8.3”, 1.12 AU, 193m) Mars is nearly 17° up in the southeast, ninety minutes before sunrise, 4.5° to the upper right of the moon (22.3d, 42%).
  • May 18: (0.2, 8.5”, 1.11 AU, 196m) One hour before sunrise, Jupiter is 27° up in the south. Saturn is 4.7° to the left of Jupiter. This is a quasi-conjunction. Saturn began retrograding May 11 and Jupiter May 18. This occurs over 7 months before the two planets’ Great Conjunction. At this time, Mars, 36° to the left of Jupiter, is 21° up in the southeast.
  • May 19: (0.2, 8.6”, 1.11 AU, 198m) Mars passes nearly 20° north of Fomalhaut (α PsA, m = 1.2). While not near the ecliptic, Fomalhaut is a bright beacon among the dimmer stars of this region. And its place helps note the passage of bright solar system objects. One hour before sunrise, Mars is 22° up in the southeast while the star is about 4° in altitude in the southeast.
  • May 21: (0.1, 8.7”, 1.08 AU, 201m) About 90 minutes before sunrise, Mars, over 18° up in the southeast, passes 0.8° to the lower right of Sigma Aquarii (σ Aqr, m =4.8).
  • May 24: (0.1, 8.8”, 1.06 AU, 205m) Ninety minutes before sunrise, Mars, over 19° up in the southeast, is 7° to the upper left of Ceres (1Ceres, m = 8.0), 1.2° to the lower right of Delta Aquarii (δ Aqr, m = 3.2).
  • May 25: (0.1, 8.9”, 1.05 AU, 207m) About 90 minutes before sunrise, Mars, over 19° up in the southeast, passes 3.5° above Tau Aquarii (τ Aqr, m = 4.0).
  • May 30: (0.0, 9.2”, 1.02 AU, 215m) Mars passes 1.9° to the lower right of Lambda Aquarii (λ Aqr, m = 3.7). Mars is over 20° up in the southeast, ninety minutes before sunrise.

June 2020

During the month, Earth moves within 1 Astronomical Unit of Mars, while the Red Planet’s brightness grows nearly 0.5 magnitude. The planet passes Neptune late in the month. As the month closes, Mars rises at about 12:30 p.m. CDT.

  • June 1: (0.0, 9.3”, 1.00 AU, 218m) Mars is 1 Astronomical Unit from Earth. Ninety minutes before sunrise the planet is 21° up in the southeast.
  • June 5: (−0.1, 9.6”, 0.98 AU, 225m) Mars is 90° west of the sun. Ninety minutes before sunrise, it is nearly 21° up in the southeast.
  • June 8: (−0.1, 9.8”, 0.96 AU, 232m) Ninety minutes before sunrise Mars is nearly 24° up in the southeast. With a binocular observe that it is 1.5° to the lower right of Phi Aquarii (φ Aqr, m = 4.2) and 0.3° to the upper left of Chi Aquarii (χ Aqr, m = 4.9).
  • June 13: (−0.2, 10.1”, 0.92 AU, 243m) Ninety minutes before sunrise, Mars, 26° up in the southeast, is 1.6° to the lower right of Neptune (m = 7.9) and 4.7° to the upper right of the moon (21.6d, 49%). Use higher powers to see Neptune’s 2.3”-diameter disk.
  • June 25: (−0.4, 11.0”, 0.85 AU, 276m) Mars moves into Pisces, below the six, fourth magnitude stars that make the western fish. Mars makes a partial passage through Pisces in 13 days, then it moves into Cetus. It is 0.2° to the upper right of 27 Piscium (27 Psc, m = 4.8). Ninety minutes before sunrise, Mars is 31° up in the southeast.

July 2020

The time differential in the notes changes to rising time after sunset. (On July 8, Mars rises in the east 221 minutes after sunset.) Earth begins to close in on Mars. Now brighter than all the stars, except Sirius from the Northern Hemisphere, Mars gleams from the southeast before morning twilight begins. It moves into Cetus for a short duration, still among dimmer stars. Continue to track it with a binocular, although larger scopes should start to bring in details visually. The morning sky has a planet parade of all the planets in the solar system. In addition to ruddy Mars, brilliant Venus joins, Jupiter and Saturn, although brilliant Venus shines from the eastern sky. Jupiter and Saturn pass opposition six days apart, then Mercury pops into the sky. This results in 5 naked eye planets in the sky at once. Additionally, the telescopic planets are there as well: Uranus, Neptune, and Pluto. (Historically, Pluto is a planet. Without too much description, we have many things in astronomy that are misnamed – like planetary nebula.)

  • July 8: (−0.6, 12.2”, 0.77 AU, 221m) Mars moves into Cetus. Mars moves across this corner of Cetus in 19 days, then back into Pisces. The constellations are not uniform in shape and size. The ecliptic is less than 1° from a corner of Cetus near coordinates Right Ascension, 0 hours, 26 minutes; Declination, 2°. Cetus also bounds Aries on the south, but Mars moves north of the ecliptic after opposition and it does not return to this constellation this apparition. Ninety minutes before sunrise (about 4 a.m. CDT in Chicago), it is 37° up in the southeast.
  • July 11: (−0.7, 12.4”, 0.75 AU, 215m) Two hours before sunrise, Mars, nearly 36° up in the southeast, is over 6° to the upper left of the moon (20.1d, 65%).
  • July 12: (−0.7, 12.5”, 0.74 AU, 212m) Mars rises before midnight CDT. Two hours before sunrise, Mars, 36° up in the southeast, is nearly 6° to the upper right of the moon (21.1d, 56%). At this time, brilliant Venus is nearly 6° up in the east-northeast, 0.9° to the upper left of Aldebaran (m = 0.8).
  • July 14: (−0.8, 12.7”, 0.74 AU, 209m) Jupiter (m = −2.8) is at opposition. One hour after sunset, Jupiter is 10° up in the southeast, nearly 7° to the upper right of Saturn. Later this night, at 1 a.m. CDT, July 15, Mars is 11° up in the east, 77° to the east of Jupiter, now 26° up in the south.
  • July 18: (−0.8, 13.1”, 0.71 AU, 200m) Mars is 105° west of the sun. Ninety minutes before sunrise, it is 42° up in the southeast.
  • July 19: (−0.8, 13.2”, 0.71 AU, 199m) Two hours before sunrise, Mars, nearly 40° up in the southeast, passes 2.2° to the upper left of 20 Ceti (20 Cet, m = 4.8). This morning and for the next week, look for the five naked eye planets simultaneously. Mercury rises higher in the eastern sky and brightens as Jupiter appears lower in the southwestern sky. This morning the thin crescent moon is part of the scene. Look for them 45 minutes before sunrise. The moon (28.1d, 2%) is about 5° up in the east-northeast. Dim Mercury (m = 0.8) is about 5° to the right of the moon at about the same altitude, only slightly higher in the sky. It’s a binocular object. Brilliant Venus (m = −4.4) is over 20° up in the east, 4.5° to the lower left of Aldebaran. By this time, Mars is over 45° up in the south-southeast. Saturn (m = 0.1) is 9° up in the southwest, 7° to the upper left of Jupiter that is just above the southwestern horizon. The five naked eye planets are in the sky simultaneously with the bonus of a thin crescent moon!
  • July 20: (−0.9, 13.4”, 0.70 AU, 197m) Saturn is at opposition. One hour after sunset, Saturn is 10° up in the southeast, about 7° to the lower left of Jupiter. As midnight approaches, Mars is about 3° up in the east, about 74° east of Saturn, now 26° up in the south-southeast.
  • July 24: (−0.9, 13.8”, 0.68 AU, 189m) Two hours before sunrise, Mars, nearly 42° up in the southeast, is 5.6° to the lower right of Delta Piscium (δ Psc, m = 4.4).
  • July 27: (−1.0, 14.1”, 0.66 AU, 184m) Mars moves back into Pisces. Two hours before sunrise, the planet is over 43° up in the southeast. Brilliant Venus is over 60° to the lower left of Mars.
  • July 31: (−1.1, 14.6”, 0.64 AU, 178m) Two hours before sunrise, Mars, 45° up in the southeast is 4.9° below Epsilon Piscium (ε Psc, m = 4.2).

August 2020

Mars, now back in the constellation Pisces, continues its eastward march, as its brightness grows. While Mars brightens, Venus dominates the morning sky. Mars passes perihelion on August 2.

  • August 2: (−1.1, 14.8”, 0.63 AU, 175m) Mars is at perihelion, 1.38 Astronomical Units from the sun. It is 45° from its position when it is at opposition, measured along its orbit. Mars rises before 10 p.m. CDT. As midnight approaches the plant is about 10° in altitude in the east.
  • August 9: (−1.3, 15.7”, 0.60 AU, 164m) Two hours before sunrise, Mars, nearly 50° up in the southeast, is 0.9° to the upper right of the moon (19.6d, 72%).
  • August 14: (−1.4, 16.4”, 0.58 AU, 155m) Two hours before sunrise, Mars, 52° up in the south-southeast, is 1.0° below Mu Piscium (μ Psc, m = 4.8).
  • August 23: (−1.6, 17.7”, 0.53 AU, 139m) Two hours before sunrise, Mars, over 50° up in the south, is 0.5° to the upper left of Nu Piscium (ν Psc, m = 4.4).

September 2020

Earth closes to within 0.5 Astronomical unit of Mars. The planet is now appearing above the eastern horizon before midnight. Mars slows and stops its eastward motion against the starry background.

  • September 2: (−1.8, 19.2”, 0.49 AU, 120m) Two hours before sunrise, Mars, 55° up in the south, is 3.6° to the upper right of Xi Piscium (ξ Psc, m = 4.6). In the evening, three hours after sunset (about 10:30 p.m. CDT in Chicago), Mars is 10° up in the east.
  • September 4: (−1.9, 19.5”, 0.48 AU, 117m) Mars is 135° west of the sun. Three hours after sunset, Mars is nearly 11° up in the east. The gibbous moon (17.0d, 92%) is over 12° to the upper right of the planet.
  • September 5: (−1.9, 19.6”, 0.48 AU, 115m) Two hours before sunrise, Mars, 54° up in the south-southwest, is 10° to the upper left of the moon (17.3d, 91%). In the evening, 3 hours after sunset, Mars – 11° up in the east – is 0.8° to the upper left of the moon (18.0d, 86%).
  • September 6: (−1.9, 19.8”, 0.47 AU, 112m) Two hours before sunrise, Mars, nearly 55° up in the south-southwest, is 2° to the lower right of the moon (18.3d, 85%). In the evening, three hours after sunset, Mars – 11° up in the east is nearly 12° to the upper right of the moon (19.0d, 79%).
  • September 8: (−2.0, 20.1”, 0.47 AU, 108m) Two hours before sunrise, Mars is 53° up in the south-southwest. This evening the planet rises before 9 p.m. CDT. Three hours after sunset, Mars is over 12° up in the east.
  • September 11: (−2.1, 20.4”, 0.46 AU, 101m) Mars eastward motion ends and it begins to retrograde. It is 141° west of the sun. Two hours before sunrise, the planet is 52° up in the south-southwest. In the evening, three hours after sunset, Mars is nearly 14° up in the east.

Until retrograde began, Mars passed four planets and a minor planet, and had an occultation with the moon. Earth is now closing in toward its closest approach and Mars’ opposition, about a month away. While not as close as the last perihelic opposition, the next opposition occurs farther north and promises great views. In a later issue, we pick up the story of Mars at opposition.

 

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Astronomy, Sky Watching

2019, October 29: Venus and the Moon

Venus passed its superior conjunction on August 14, 2019, and slowly moved to the evening part of the sky. For several weeks, the visibility of Venus suffered from our poor view of the solar system near the sun after sunset for observers at mid-northern latitudes. Now in October, Venus starts to become visible. 

Venus climbs into bright evening twilight in the southwestern sky and is soon visible in darker skies.  It is headed toward a conjunction with Jupiter in late November. 

On October 27, Venus is 20° from the sun and sets in the southwest and about an hour after sunset.

The moon makes its first appearance with Venus on October 29, as illustrated above.  

Here’s what to look for (Find a clear southwest horizon and use a binocular to initially help you locate Venus and the moon.): Thirty minutes after sunset, the moon appears to the upper left of Venus, only 4° up in the southwest with bright Jupiter to the upper left of the pair. The moon is 1.8 days old, past its New phase, and 4.4% illuminated.

Let us know what you see in the comments below.  Click the link and subscribe to this web page.  Fall 2019 is an exciting time to observe Venus and the moon pass the bright evening planets.

Astronomy, Sky Watching

2019, October 26, 2019: Mars and the Moon

After its solar conjunction in early September, Mars has been crawling into the morning sky.  It is a not-so-bright “star” that is low in the eastern sky before sunrise in late October.  The moon provides guidance to its location.  Take along a binocular and find a clear horizon.  Here’s what to look for.

  • October 25: One hour before sunrise, the waning crescent moon (26.7 days past its new phase and 10% illuminated), over 20° up in the east-southeast. Mars, only 5° up in the east, is nearly 19° to the lower left of the moon. On closer inspection, the Red Planet is 3.8° to the lower right of Gamma Virginis.
  • October 26: The moon is very thin this morning, only 4% illuminated.  The thin sliver is striking to see. One hour before sunrise, the moon, about 11° up in the east, is 1.9° to the upper left of Gamma Virginis and nearly 6° to the upper left of Mars. Use a binocular to view this scene.

Let us know what you see in the comments.

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Astronomy, Sky Watching

2019, October 1-6: Waxing Moon Passes Evening Planets, Jupiter and Saturn
The moon passes the evening planets, Jupiter and Saturn, during early October 2019. (The moon’s size is exaggerated on the diagram.)

The moon returns to the evening sky and passes Jupiter and Saturn early in October 2019.  The following summarizes the evenings, one hour after sunset.  (Check your local sources for the time of sunset for your location.)

  • October 1: One hour after sunset the crescent moon (3.2 days after the New phase, 15% illuminated), 11° up in the west-southwest, is east of a line that connects Zubenelgenubi  and Zubeneschamali (β Lib, m = 2.6), 6.5° to the lower left of Zubeneschamali.  Bright Jupiter is 19° up in the southwest.  Meanwhile, Saturn is about 25° to the upper left of Jupiter.  Saturn is nearly 26° up in the south.
  • October 2: The crescent moon (4.2d, 23%) is about 16° up in the southwest, one hour after sunset. Through a binocular observe the crescent moon. The binocular reveals the gentle glow of Earthshine in the lunar night. At the same time, the lunar crescent is nearly 12° to the lower right of Jupiter.
  • October 3: One hour after sunset, the moon (5.2d, 33%) is 1.9° to the upper left of Jupiter.
  • October 4: One hour after sunset, the moon (6.2d, 43%) is nearly midway between Jupiter and Saturn; the planets are over 25° apart, although the moon is closer to Saturn. The moon – Saturn gap, 10.7°; moon – Jupiter, 14.6°. All three are along the same diagonal line.
  • October 5: Today, the moon reaches its First Quarter phase at 11:47 a.m. CDT Three of the bright planets continue to hide in the sun’s glare. Mars, about a month after its solar conjunction, is 11° west of the sun, rising about one hour before sunrise. The visibility of Mercury and Venus suffers from a poorly inclined ecliptic – plane of the solar system – this time of year. Venus, 14° east of the sun, sets 36 minutes after the sun; Mercury, 21° east of the sun, sets about 5 minutes after Venus. The two bright outer planets, Jupiter and Saturn are in the southern sky after sunset. Saturn, 25° up in the south, is 2.1° to the upper right of the slightly gibbous moon (7.2d, 53%). The planet is west of south cardinal point. Bright Jupiter, 25° to the lower right of Saturn, is nearly 18° up in the south-southwest.
  • October 6: One hour after sunset, the moon (8.2d, 63%), 25° up in the south – east of the meridian, is over 14° to the upper left of Saturn.

Happy observing!

Astronomy, Sky Watching

2019, September 23: Equinox: Equal Night or Equal Day and Night

 

(Image Credit: NASA)

The sun reaches the Autumnal Equinox (as considered from the Northern Hemisphere) on September 23, 2019 at 2:50 a.m.  CDT. 

Since our planet is tilted about 23.5 degrees, the sun appears higher in the sky during the summer season and lower during the winter.  The sun’s rising and setting positions change throughout the seasons as well.   During late March and late September, the sun rises at the east cardinal point and sets at the west cardinal point.  Its arc across the sky is halfway between the extremes of Summer and Winter.

The sun’s light shines most directly at the equator.  Those folks living there see the sun pass overhead.  Noon is nearly shadowless. because of the sun’s path as seen from the equatorial region.

The day is called “Equinox,” sometimes translated as “equal night.”  The sun is in the sky for approximately 12 hours from the equator to higher latitudes.  Sometimes we tell school children that we have “12 hours of daylight and 12 hours of night.”

Consider this: During a 24-hour period, there are three cycles of light.  Daytime, the period when the sun is above the horizon and brightly illuminates the ground.  Dark, the period when the sky is completely without sunlight and twilight and it is as dark as it gets naturally.  Twilight, the period when the sun is below the horizon, but it illuminates the sky.  As the sun sets, the sky is bright and it’s easy to see terrestrial features.  This is known as Civil Twilight.  During this twilight phase, streetlights turn on.  If you know where to look, Venus and Jupiter can be seen

The sky continues to darken.  From a location with a good horizon, Nautical twilight occurs when the horizon is barely visible.  This is easier to at sea and so the name.  Brighter planets and stars become visible.  This occurs about 60 minutes after sunset.  Then the sky continues to darken until the last light shines from the western horizon.  This is Astronomical Twilight.  This takes about 90 minutes.  Until the process reverses in the morning, the sky is dark, as dark as it gets naturally.

So when I look at this for my latitude, on September 23, daylight is 12 hours, 8 minutes long; twilight, 3 hours, 7 minutes; and darkness, 8 hours, 45 minutes.

At my latitude “Equal Darkness,” when the daylight hours are equal to the dark hours, is October 30. Daylight and darkness are equal at 10 hours, 26 minutes. Twilight takes up the balance that is divided between the pre-sunrise hours and post-sunset hours.

 

Astronomy, Sky Watching

2019, September 24: The Moon and Beehive Cluster

September 24: As the sky begins to brighten in the morning, about 90 minutes before sunrise, look east for the waning cresent moon.  It is 25.0 days old (past the New phase) and 25% illuminated.  Castor and Pollux, the Gemini Twins, are above the moon and Procyon is to the moon’s right.  Regulus is far below the moon.

With a binocular look below the moon for a small smattering of stars.  They look like diamonds on the velvet of the darker sky.  This is the Beehive Cluster.  The cluster is about 500 light years away and it contains about 350 stars, a few dozen of which can been seen with a binocular.

If you have sharp eyesight, look for the cluster without a binocular. To the unaided eye, the cluster resembles a cotton ball.

The cluster is also known as the Praesepe (Manger).  More formally it is known by its catalog numbers M44 or NGC 2632.

Tomorrow morning, September 25, the moon is below the cluster and still above Regulus.  Take a look!

(As an aside, look at the moon through the binocular.  On the night portion, notice that it is slightly illuminated.  This is from sunlight reflecting from the nearly full Earth, as seen from the moon, gently illuminating the night portion of the moon — Earthshine.)

Astronomy, Sky Watching

2019, August 29: Sirius in Eastern Morning Sky

Now appearing in a darker sky, Sirius joins the bright stars in the eastern sky.  The sky’s brightest star is now past its heliacal rising.  The Winter Triangle – Sirius, Betelgeuse, and Procyon – is easy to locate.  Betelgeuse is visible with Rigel, stars in Orion.  Farther north, the stars of Gemini – Castor and Pollux are visible.