An Angara rocket launches the COSMOS 2560 satellite from Plesetsk Cosmodrome on Oct.
Look for the Great Diamond of Spring in May's night sky and discover the rich realm of galaxies within. (Image credit: Yoshiyoshi Hirokawa via Getty Images)
With the evening moon appearing as a crescent phase for much of this upcoming week, we now have an opportunity to view some of the fainter sky objects that now occupy our spring evening sky.Looking high overhead and toward the south just after nightfall, there is a broad star pattern formed by four stars. The near-third magnitude star, Cor Caroli (in the constellation of Canes Venatici the Hunting Dogs), is the faintest of the four that comprise a large diamond frame that can be found high in the sky and due south at around 10 p.m. local daylight time. The other stars in the diamond are second magnitude Denebola (marking the tail of Leo, the Lion), first magnitude Spica (the spike of wheat in the hand of Virgo) and zero-magnitude Arcturus (in Boötes the Herdsman).In his popular constellation guide, "The Stars — A new Way to See Them," author Hans A. Rey (1898-1977) called it the "Virgin's Diamond," after the constellation of Virgo, though others refer to it simply as "The Great Diamond."But it's not sanctioned. . . Of course, the Diamond is not an official constellation but is an asterism. The constellations shown on modern star atlases are all officially approved by the International Astronomical Union (I.A.U.), but while constellations are official, asterisms are not. An asterism is often defined as a noteworthy or striking pattern of stars within a constellation, but that is not always the case. The Big Dipper is not a constellation itself, but an asterism which is part of the larger constellation of Ursa Major, the Great Bear.
The Great Diamond in the night sky. (Image credit: Created in Canva Pro)Some might wonder why the constellation patterns differ from other similarly designed charts and are not standardized. The two main reasons are that different people see constellations in different ways and that, as far as astronomy today is concerned, constellations are not considered star pictures but as specific sky areas. The official constellation boundaries were drawn up in 1930. Before that time, no two atlases agreed as to the limits, and much confusion resulted.So, while the Diamond is not "official," it still is recognized as a landmark star pattern of the spring season.And even here, some see this pattern differently. If, for example, we don't include Cor Caroli, then the Diamond becomes "The Spring Triangle."Stellar statsHere are some noteworthy details about each star, going from brightest to faintest:Arcturus: A brilliant star that sparkles with a golden yellow or topaz hue, it is the brightest star in the constellation Boötes the Bear Driver. In late spring and early summer, Arcturus is usually the first star you see after sunset, soaring high in the southern sky. It ranks as the fourth brightest star in the sky and is a giant, fully 26 times the diameter of the sun and 170 times as luminous.Its main claim to fame is that it opened Chicago's Century of Progress Exposition of 1933 by shining on a photoelectric cell and moving through space at 76 miles (122 km) per second, which means that over the centuries, it changes its place in the sky more rapidly than any of the other bright stars.Spica: In Greek and Roman tradition, the constellation of Virgo was identified with the goddess of justice, Astraea, who ruled the world during the fabled Golden Age. In the old allegorical star books, the goddess holds some spikes of wheat in each hand and her brightest star — Spica — glows in one of the ears of grain hanging from her left hand. Spica is the 16th brightest star in the sky and is 250 light-years away. It is not one star but two, positioned so close to one another that they are egg-shaped rather than spherical, and can only be separated by their spectra; the two components orbit each other every four days. The primary star is about 20,000 times more luminous tha
An Angara rocket launches the COSMOS 2560 satellite from Plesetsk Cosmodrome on Oct. 15, 2022. Another trio in the COSMOS series — COSMOS 2581, 2582 and 2583 — launched in February 2025 and has performed sophisticated rendevzous operations in orbit. (Image credit: Roscosmos)
Two Russian spacecraft just demonstrated a very particular set of orbital skills.The satellites, known as COSMOS 2581 and COSMOS 2583, got within just 10 feet (3 meters) or so of each other on April 28, according to COMSPOC, a Pennsylvania-based space situational awareness company."This wasn't a coincidental pass — COSMOS 2583 performed several fine maneuvers to maintain this tight configuration," COMSPOC wrote in a May 1 X post, which featured an animation of the rendezvous.🛰️Russian satellites multi-object proximity event in LEORadar tracking data via @LeoLabs_Space, processed through COMSPOC SSA Suite.This week we observed a complex proximity event involving Russian satellites: COSMOS 2581, 2582, 2583, and Object F (a subsatellite released by… pic.twitter.com/3nDkcOmTuDMay 1, 2026The two satellites and a third one, COSMOS 2582, launched to low Earth orbit in February 2025 atop a Soyuz rocket. According to COMSPOC, all three of them were involved in the recent rendezvous and proximity operations (RPO), as was "Object F," a subsatellite previously deployed by COSMOS 2583.During the 10-foot close approach, "COSMOS 2582 trailed the formation at sub-100 km range, while Object F passed within 15 km of 2582 and within 10 km of 2581 — neither maneuvered," wrote COMPSOC, which analyzed radar tracking data gathered by the California company LeoLabs."For context: in late 2025 to now, we tracked these same COSMOS satellites performing 3-object RPO," COMSPOC added in the May 1 X post. "Whatever Russia is testing, it's sophisticated."Such sophisticated orbital maneuvering is not exactly surprising; we've seen similar things from Russia before. For example, according to outside observers, the nation has operated multiple "inspector satellites," including COSMOS 2542, which made a close approach to a U.S. spy satellite in 2020.The other major space powers have such capabilities as well. American and Chinese satellites have also been observed checking out other nations' spacecraft high above Earth.
Michael Wall is the Spaceflight and Tech Editor for Space.com and joined the team in 2010. He primarily covers human and robotic
spaceflight, military space, and exoplanets, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.
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