Sagittarius A*

Objects shown in this view

Sagittarius A* (supermassive black hole)

The center of the Milky Way; in 2022 the Event Horizon Telescope imaged its shadow. Its event horizon is about the diameter of Mercury's orbit around the Sun. Reinhard Genzel and Andrea Ghez shared half of the 2020 Nobel Prize in Physics for decades of tracking the orbits of stars around it. The star S2 orbits it with a period of about 16 years, accelerating to nearly 3% of the speed of light at closest approach. Radio emission from the galactic center was first detected in 1974, long before it was known to be caused by a black hole. It's a relatively quiet supermassive black hole: it isn't actively consuming large amounts of matter, so it's far dimmer than many other galactic nuclei. It can't be observed in visible light, since intervening interstellar dust blocks it - only radio, infrared and X-ray observations reveal it. The Event Horizon Telescope's 2022 image was only the second black hole ever imaged, after M87's in 2019. Its name comes from the constellation Sagittarius, the direction in which it appears from Earth.

Sun / Solar System (G2V star · you are here)

Orbits the galactic center at ~230 km/s. In one full galactic year, the Solar System has only orbited the Milky Way a handful of times since the dinosaurs went extinct. The Orion Arm is actually a minor spur bridging the Milky Way's two major arms (Perseus and Sagittarius), not a full spiral arm of its own. The Sun formed about 4.6 billion years ago from an interstellar cloud of gas, likely alongside many sibling stars in an open cluster. It also oscillates vertically relative to the galactic plane, bobbing above and below the disk roughly every 30 million years. Because of our distance from the galactic center, the Milky Way's light appears as a faint band across the night sky, brightest toward Sagittarius.

Orion Nebula (M42) (diffuse nebula · stellar nursery)

A naked-eye star-forming region in the sword of Orion. It's the closest large star-forming region to Earth, making it one of astronomy's most closely studied nebulae. At its heart, the four hot young stars of the Trapezium Cluster ionize the surrounding gas, producing the nebula's glow. It contains thousands of young stars and protoplanetary disks (proplyds), where planetary systems are actively forming. Charles Messier catalogued it in 1769, though it had already been observed through telescopes since the 1610s. Both Hubble and the James Webb Space Telescope have produced highly detailed images of it, revealing the young stars hidden within.

Pleiades (M45) (open star cluster)

Young, hot blue stars; 6–7 are visible to the naked eye. It's only about 100 million years old, astronomically very young for a star cluster. The cluster is wrapped in a faint blue reflection nebula, which is actually the light of an unrelated dust cloud it happens to be passing through. It features in the mythology of many cultures: the Seven Sisters in Greek myth, and Subaru in Japanese culture (the source of the car maker's logo). It contains at least a thousand stars, though only the brightest 6-9 are visible to the naked eye. In tens of millions of years, the Milky Way's gravity will gradually disperse the cluster's stars onto independent orbits.

Eagle Nebula (M16) (emission nebula + star cluster)

Home of Hubble’s famous “Pillars of Creation” image. The famous 1995 Hubble image was led by Jeff Hester and Paul Scowen, and remains one of astronomy's most iconic pictures. The 'pillars' are dense columns of hydrogen gas and dust in which new stars are actively forming. A 2014 Hubble follow-up and a 2022 James Webb image, both in infrared, saw through the dust to reveal the young stars hidden inside. It's named after the bright star cluster embedded within it, part of the surrounding open cluster NGC 6611. The Pillars may have already been destroyed by a nearby supernova shockwave millennia ago - what we see today is delayed light from before that event.

Alpha Centauri (triple star system)

The closest star system to the Sun; Proxima Centauri b orbits in the habitable zone. It's made up of three stars: Alpha Centauri A and B form a close binary pair, while the faint Proxima Centauri orbits farther out. Alpha Centauri A and B are similar in size and temperature to the Sun, earning them the nickname 'the Sun's twins'. Proxima Centauri is a red dwarf, and is itself the single closest star to the Sun. Proxima Centauri b's discovery was announced in 2016; its mass is roughly Earth-like. It's visible to the naked eye from the southern hemisphere, the third-brightest star in the night sky. The Breakthrough Starshot project aims to send tiny, light-propelled probes to the system within decades.

Betelgeuse (red supergiant)

The shoulder of Orion; astronomically speaking, it will explode as a supernova in the near future. It's so large that if placed at the Sun's position, its surface would extend past Jupiter's orbit. It dimmed unusually in 2019-2020, sparking speculation of an imminent supernova - astronomers eventually attributed this to a huge dust cloud it had ejected. 'The near future' in astronomical terms could still mean anywhere up to hundreds of thousands of years, not necessarily within a human lifetime. If it explodes, the supernova would likely be visible from Earth even in daylight, but poses no danger to life on Earth given the distance. Its mass is about 15-20 times the Sun's, and it's a rapidly evolving star nearing the end of its life.

Crab Nebula (M1) (supernova remnant)

The remnant of the supernova observed in 1054; a pulsar sits at its center. The 1054 supernova was recorded by Chinese and Japanese astronomers, reportedly visible in daylight for weeks. At its center, a neutron star (pulsar) spins about 30 times per second, emitting beams of radio and X-ray radiation. Charles Messier catalogued it first in 1758, an observation that helped spark his later Messier catalogue of deep-sky objects. The nebula is still expanding, and measuring the expansion speed of its gas let astronomers calculate the date of the original explosion. It's one of the most important objects in the history of stellar evolution theory, since its origin is tied to a specific, historically observed event.

Lagoon Nebula (M8) (emission nebula)

A naked-eye stellar nursery toward Sagittarius. It's named for the dark, winding dust lane that curves through it, resembling a lagoon. It spans about 100 light-years, making it one of the largest and brightest diffuse nebulae in the sky. Charles Messier catalogued it in 1764, though Arab astronomers had already noted it centuries earlier. A compact region within it, nicknamed the 'Hourglass Nebula', hosts especially intense star formation. It's an easy target for binoculars or even a modest telescope, making it one of the most popular amateur astronomy targets.

Carina Nebula (NGC 3372) (giant emission nebula)

One of the largest stellar nurseries; home to Eta Carinae. It's larger and brighter than the Orion Nebula, but visible only from the southern hemisphere, so it's less widely known. Eta Carinae is an extremely unstable, massive star system that underwent a giant eruption around 1840 and could explode as a supernova at any time. It contains the 'Homunculus Nebula', the cloud of material ejected during Eta Carinae's 1840 outburst. It hosts several open star clusters, including the young, hot Trumpler 14. The James Webb Space Telescope's 2022 image known as the 'Cosmic Cliffs' was taken from this nebula.

Double Cluster (h and χ Persei) (pair of open clusters)

Two young clusters side by side, both visible to the naked eye. The two clusters are physically close to each other, likely born from the same star-forming cloud around the same time. They're only about 12-14 million years old, extremely young by astronomical standards. The ancient Greek astronomer Hipparchus already recorded their existence around 130 BCE. Together they contain several thousand stars, including a number of unusually bright supergiants. Through binoculars or a small telescope, they're one of the most beautiful sights in the northern sky, in the constellation Perseus.

Omega Centauri (NGC 5139) (globular cluster)

The Milky Way’s largest globular cluster, with millions of ancient stars. It's about 150 light-years across, with a mass of roughly 4 million Suns - far larger than most other globular clusters. Some astronomers believe it's actually the surviving core of a dwarf galaxy the Milky Way absorbed long ago, rather than a 'true' globular cluster. It may harbor an intermediate-mass black hole at its center, though this remains debated. It's visible to the naked eye from the southern hemisphere, one of the brightest globular clusters in the sky. Its stars show an unusually wide range of ages and compositions, supporting the dwarf-galaxy origin theory.

Rosette Nebula (emission nebula)

A flower-shaped stellar nursery with a young cluster at its heart. It spans about 130 light-years, and the young star cluster at its center (NGC 2244) ionizes the surrounding gas with its radiation. The cluster's stars are only a few million years old, having formed from the nebula's own material. Its ring-like, hollow shape comes from stellar winds and radiation from the cluster blowing the surrounding gas outward. It lies in the constellation Monoceros, a favorite target for amateur astrophotographers. In long-exposure images it glows a distinctive red, produced by ionized hydrogen gas.

Vela Supernova Remnant (supernova remnant)

The remnant of a star that exploded ~11,000 years ago, with a pulsar. The Vela Pulsar spins about 11 times per second, making it one of the most closely studied neutron stars. The gas cloud left behind by the explosion is still expanding, forming intricate, filamentary structures. Its relative closeness (about 800 light-years) makes it one of the best-studied supernova remnants. The Vela Pulsar regularly produces 'glitches', sudden jumps in its spin rate, that reveal clues about a neutron star's internal structure. It's visible from the southern hemisphere, in the constellation Vela.

Rho Ophiuchi Cloud (star-forming cloud)

One of the closest, most colorful clouds of dust and gas. It's one of the closest active star-forming regions to the Sun, making it especially important for astronomical research. Its varied colors come from a mix of blue reflection nebulae, red emission nebulae, and dark dust lanes. It lies right next to the red supergiant star Antares, which adds further color to the scene. It contains hundreds of young, still-forming stars (protostars). It's one of the most popular targets in astrophotography, prized for its rich color palette.

North America Nebula (NGC 7000) (emission nebula)

A nebula named for its continent-like shape, near Deneb. William Herschel discovered it in 1786, though its continent-like shape only really shows up in photographs. The darker area nicknamed the 'Gulf of Mexico' is actually a foreground dust cloud blocking the brighter gas behind it. It's physically connected to the neighboring Pelican Nebula, separated visually only by an intervening dust lane. It lies in the constellation Cygnus, near the bright star Deneb. It's a faint object, best seen with dark skies and long-exposure astrophotography.

Large Magellanic Cloud (satellite dwarf galaxy)

The Milky Way’s largest companion; supernova SN 1987A erupted here. SN 1987A was the closest and most closely studied supernova of the modern astronomical era. It's named after Ferdinand Magellan, whose 1519-1522 expedition was the first to document it for Europeans. It hosts its own active star-forming regions, including the Tarantula Nebula, one of the most active such regions in the Local Group. It's easily visible to the naked eye from the southern hemisphere, as a bright, hazy patch. The Milky Way's gravity is slowly tearing it apart; a stream of gas connects it to the Small Magellanic Cloud.

Small Magellanic Cloud (satellite dwarf galaxy)

A dwarf galaxy visible to the naked eye from the southern hemisphere. Along with the Large Magellanic Cloud, it's one of the Milky Way's closest and brightest satellite galaxies. Henrietta Leavitt's observations of Cepheid variable stars here, around 1908, established the period-luminosity relation, a cornerstone of astronomical distance measurement. Its mass and size are much smaller than the Large Magellanic Cloud's, hence the name. A stream of interstellar gas connects it to the Large Magellanic Cloud, evidence of their gravitational interaction. It lies in the constellation Tucana, one of the easiest dwarf galaxies to find in the sky.