2024, May 8: Mars at Perihelion

Astronomy

2024, May 8: Mars is at Perihelion today, its closest point to the sun.  Find it before sunrise in the eastern sky.

Mars - This image shows the globe of Mars set against a dark background. The disc of the planet features yellow, orange, blue and green patches, all with an overall muted grey hue, representing the varying composition of the surface.
Chart Caption – To mark 20 years of ESA’s Mars Express, the High Resolution Stereo Camera (HRSC) team has produced a new global color mosaic: Mars as never seen before. The mosaic reveals the planet’s surface color and composition in spectacular detail. (Photo: European Space Agency, ESA)

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by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 5:38 a.m. CDT; Sunset, 7:57 p.m. CDT.  Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.

Mars Closest to Sun

Mars at perihelion
Chart Caption – Mars is at perihelion – the closest point to the sun.

Mars is at perihelion today.  The planet is closest to the sun, 1.38 astronomical units (or A.U.) from the central star.  One A.U. is Earth’s average distance from the sun, a value of about 93 million miles.

The Red Planet’s orbit is  not a perfect circle, but elliptical.  It ranges from this perihelion distance to 1.67 A.U., the farthest distance from the sun, known as aphelion.

Mars at Perihelion. Lowell and his canals
Photo Caption – Percival Lowell and his map of Mars (Photo Credit: Lowell Observatory)

When Earth passes between the sun and Mars near the Martian perihelion, Mars shines brightly in the night sky.  Before the invention of robot spacecraft, Mars’ tiny moons were observed during a perihelic opposition.  At another close opposition, Percival Lowell’s supposedly observed the planet’s “canals,” likely contributing to science fiction’s stories of Martian life.

Mars at opposition, 2016 and 2018
These side-by-side images of Mars, taken roughly two years apart, show very different views of the same hemisphere of Mars. Both were captured when Mars was near opposition, which occurs about every two years, when Earth’s orbit catches up to Mars’ orbit. At that time, the Sun, Earth, and Mars fall in a straight line, with Mars and the Sun on “opposing” sides of Earth. (NASA Photo)

Perihelic Oppositions

Perihelic oppositions, those times when Earth passes Mars at perihelion, occur every 15-17 years.  The last one occurred during 2018, and the next is forecast for September 15, 2035. The closest gap between Earth and Mars is predicted to be 0.38 A.U., four days before opposition.

The largest canyon in the Solar System cuts a wide swath across the face of Mars. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep.
The largest canyon in the Solar System cuts a wide swath across the face of Mars. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep. (NASA)

While Mars is currently low in the eastern sky before sunrise, Earth is slowly overtaking it.  Our world passes by on January 15, 2025.  By then Mars is approaching aphelion and the distance between the two planets is 0.64 A.U., although the next opposition, February 19, 2027, is farther at 0.67 A.U.

Summaries of Current Sky Events
Summary for Venus as a Morning Star, 2023-24

Here is today’s planet forecast:

Morning Sky

Mars and Saturn before Sunrise

Mars at Perihelion
Chart Caption – 2024, May 8: Mars and Saturn are in the eastern sky before sunrise.

Mars and Saturn are in the eastern sky an hour before sunrise.  Saturn, nearly 15° above the east-southeastern horizon, is easier to see.

Mars, marching eastward, continues to open a gap with the Ringed Wonder.  It is over 6° above the east horizon and over 18° to Saturn’s lower left.  With no bright star in the region, look carefully with a binocular for the morning planets.

Mercury and Venus

Mercury, rising 51 minutes before the sun, suffers from a poorly inclined ecliptic, because the plane of the solar system makes a low angle with the horizon. At 30 minutes before sunrise, it is less than 5° above the eastern horizon and over 16° to the lower left of Mars, now bathed in bright twilight.

Venus rises only 14 minutes before the sun.  It nears its superior conjunction with the sun early next month, followed by a wide swing into the western sky as the Evening Star.

Evening Sky

Moon and Aldebaran

2024, May 8: A thin crescent moon and Aldebaran are in the west-northwest after sundown.
Chart Caption – 2024, May 8: A thin crescent moon and Aldebaran are in the west-northwest after sundown.

At 45 minutes after sundown, moon watchers can find a razor-thin crescent moon through a binocular less than 5° above the west-northwest horizon.  Tomorrow evening, look for the moon that is 5% lit and about 15° up in the evening sky during twilight.

This evening, the star Aldebaran is over 6° above the horizon and over 12° to the moon’s upper left.  It nears its heliacal setting, the last evening that it is visible without any optical assistance.

Capella is about one-third of the way up in the sky above the northwest horizon. This star is approaching its first morning appearance.  It is one of a few bright stars that can be seen before sunrise in the eastern sky and again in the west after sundown.  It is visible before sunrise, then moving westward during the daytime to show in the western sky after sundown.

Double Exposure

This double appearance occurs because of its far northerly location.  It makes a longer arc across the sky than the sun, so it appears before sunup and after sundown.  Stars that are farther northward than Capella, Arcturus, Deneb, and Vega never set, the so-called circumpolar stars that include the two Bears, the King and Queen, and the Dragon.  Polaris is nearly above Earth’s north pole and seems to be fixed above the north cardinal direction.

The evening sky is without a bright evening planet.  Jupiter, nearing its solar conjunction, sets 36 minutes after sunset and nearly an hour before Aldebaran.

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