Special to CosmicTribune.com, May 5, 2024

Excerpts from weekly Sky&Telescope report.

SUNDAY, MAY 5

■ A gigantic spring asterism you may not know is the Great Diamond, some 50° tall and extending over five constellations. It now stands upright in the southeast to south after dusk. Its stars are magnitudes 0, 1 ,2 and 3.

Start with Spica, its bottom, mag 1. Upper left from Spica is brighter Arcturus, mag 0. Almost as far upper right from Arcturus is Cor Caroli, 3rd magnitude. The same distance lower right from there is Denebola, the 2nd-magnitude tailtip of Leo. And then back to Spica.

The bottom three of these stars, the brightest, form a nearly perfect equilateral triangle. We can call this the “Spring Triangle” to parallel to those of summer and winter.

MONDAY, MAY 6

■ Face north as the stars come out, look very high, and you’ll find the Pointers, the end stars of the Big Dipper’s bowl, on the north meridian pointing toward Polaris straight down below. From the Pointers to Polaris is about three fists at arm’s length.

TUESDAY, MAY 7

■ The Sombrero Galaxy, M104, is one of the most iconic deep-sky objects. Glowing at 8th magnitude, it’s ideally placed at its highest in the south these moonless evenings. It’s on the border of Corvus and Virgo 10° west of Spica. Less well known are a bunch of nice telescopic double stars in the Sombrero’s general area.

Matt Wedel says M104 is “one of the few galaxies for which I can reliably detect an orientation in 10×50 binoculars.” But for that you’ll definitely need a very dark sky.

■ New Moon (exact at 11:22 p.m. EDT).

WEDNESDAY, MAY 8

■ The Arch of Spring spans the western sky in late twilight. Pollux and Castor form its top: They’re lined up roughly horizontally in the west-northwest, about three finger-widths at arm’s length apart. Look far to their lower left for Procyon, and farther to their lower right for 2nd-magnitude Menkalinan and then bright Capella.

On May 10th the waxing Moon will start stepping up through the inside of the Arch, as indicated below.

Back in the evening sky, the waxing crescent emerges to begin a new lunation. (The Moon is drawn three times its actual apparent size; it doesn’t really overlap the Pleiades. Not that you will see the Pleiades so low in bright twilight anyway!)

THURSDAY, MAY 9

■ Summer is still six weeks away, but the Summer Triangle is beginning to make its appearance in the east, one star after another. The first in view is bright Vega. It’s already low in the northeast as twilight fades.

Next up is Deneb, lower left of Vega by about two fists at arm’s length. Deneb follows about an hour and a half behind Vega.

The third is Altair, which shows up far to their lower right by 10 or 11 p.m.

FRIDAY, MAY 10

■ Three zero-magnitude stars shine after dark in May: Arcturus high in the southeast, Vega much lower in the northeast, and Capella in the northwest. They appear so bright because each is at least 60 times as luminous as the Sun, and because they’re all relatively nearby: 37, 25, and 42 light-years from us, respectively.

This evening, Vega and Capella stand at the same height above the horizon shortly after dark.

SATURDAY, MAY 11

■ This is the time of year when Leo the Lion starts walking downward toward the west, on his way to departing into the sunset in early summer. Right after dark, spot the brightest star fairly high in the west-southwest. That’s Regulus, his forefoot.

SUNDAY, MAY 12

■ The thickening crescent Moon shines just left of Pollux this evening. About twice as far to their right, Castor lies nearly on the same line. For skywatchers in the Central time zone, the lineup is perfect about an hour after full dark. That happens later at night for the Eastern time zone, earlier if you’re west of Central.

  May 5-12: Summer triangle appears in the East, The Sky