Astronomy

Black holes should be practically everywhere. In the Milky Way Galaxy, you shouldn’t be able to go across the street without hitting one. Stellar mass black holes result from dying, massive stars, which end their lives in supernova explosions. So, given the stellar population history of our galaxy, there ought to be tens of millions or more black holes in the Milky Way. And yet we know of only about two dozen. Why? They are very hard to detect. Black holes were hypothesized by the English natural philosopher John Michell, who calculated that collapsed “dark stars” with extreme gravity ought to exist. That was in 1783. Despite this, evidence for the first stellar black hole wasn’t confirmed until 1990, with the famous “bet” between Stephen Hawking and Kip Thorne. During the first…

Memorable viewing Your January 2023 issue was excellent! The bright comet list brought back pleasant memories of nights outdoors. I graduated from high school in 1957, and that is the only year I remember seeing two naked-eye comets: Comet Arend-Roland and Comet Mrkos (formally known as C/1957 P1). I recall hauling my small scope atop our high school building to watch them with members of our science club. Your notes about comet photography correctly point out how digital photos are now easy to take; it’s too bad we only had a Kodak Hawkeye camera in 1957. — Roger Grossenbacher, Lancaster, OH Missing mission I am disappointed that your January 2023 special issue on comets failed to mention the historic Stardust mission, which brought back samples from the coma of Comet Wild-2 and then…

NGC 346 — tucked in the Small Magellanic Cloud (SMC), a dwarf galaxy close to the Milky Way — is one of the most curious star-forming regions in the nearby universe. The SMC has an extremely low metallicity, meaning it lacks almost any elements other than hydrogen and helium. As such, it looks less like a modern galaxy and more like one that belongs in the 2-billion- to 3-billion-year-old universe. This period corresponds to a time called cosmic noon, when stars first began cropping up in droves following the Big Bang. In the photo, the orange strands show dense, cold clouds of molecular hydrogen and dust feathering outward, creating an optimal environment for star and planet formation. The fluffier pink areas, meanwhile, highlight much hotter, more energetic clouds of hydrogen. The fact that…

HOMELESS STARS Hubble recently showed that light from stars that are between galaxies within clusters is present in both old and young groups. This means stars are lost from their galaxies as clusters form, rather than stripped away over time. MOUNT MAGNETAR A magnetar — a rapidly spinning, highly magnetic neutron star — suddenly slowed its spin and began emitting radio waves in October 2020. Astronomers speculate a volcano-like rupture on its surface might be to blame. FAIL BRITANNIA On Jan. 9, Virgin Orbit attempted the first ever orbital launch from the United Kingdom. But the rocket’s upper stage suffered an anomaly, failing to lift the vehicle into orbit. Virgin Orbit has previously made four successful launches, all from California. SCIENCE: NASA, ESA, STSCI, JAMES JEE (YONSEI UNIVERSITY); IMAGE PROCESSING: JOSEPH DEPASQUALE (STSCI).…

Finding dark nighttime skies for observing is getting harder — and the rate at which dark skies are disappearing is faster than satellite-based measurements might indicate. This find comes from a Science paper published Jan. 19 and based on more than a decade of observations from around the world. To determine how quickly the night sky is brightening, researchers developed the Globe at Night citizen science project. They gave 51,351 volunteers in 19,262 locations a star chart showing which stars are visible under varying levels of light pollution. The volunteers then regularly reported which chart best matched the sky from their location on cloudless, Moonless nights. Those reports showed the sky is growing brighter at a rate of 7 to 10 percent per year, averaging out to a global decrease in night-sky…

The dusty debris disk of AU Microscopii, located a mere 32 light-years away, glows in new images from the James Webb Space Telescope (JWST). Using a coronagraph — an instrument that can block light from the central star (whose location is shown here by a white graphical star) — astronomers imaged the disk with two different infrared filters. The blue image shows infrared light at 3.56 microns and reveals fine-grained dust. The red image shows a wavelength of 4.44 microns and traces coarser grains. The blue image is brighter, meaning there is more fine dust than coarse. Astronomers were able to view the disk down to about 460 million miles (740 million kilometers) from the star — roughly the distance of Jupiter from the Sun. While that may seem far,…