Magazine Posts

NASA Astronomy Picture of the Day:

How much mass do flocculent spirals hide? The featured image of flocculent spiral galaxy NGC 4414 was taken with the Hubble Space Telescope to help answer this question. Flocculent spirals -- galaxies without well-defined spiral arms -- are a quite common form of galaxy, and NGC 4414 is one of the closest. Stars and gas near the visible edge of spiral galaxies orbit the center so fast that the gravity from a large amount of unseen dark matter must be present to hold them together. Understanding the matter and dark matter distribution of NGC 4414 helps humanity calibrate the rest of the galaxy and, by deduction, flocculent spirals in general. Further, calibrating the distance to NGC 4414 helps humanity calibrate the cosmological distance scale of the entire visible universe.

Portrait of Billie Holiday and Mister, taken by William Gottlieb at the Downbeat Club, New York, 1947. Today, 110 years ago, she was born in Philadelphia.

William P. Gottlieb, Public domain, via Wikimedia Commons. View source.

NASA Astronomy Picture of the Day:

Why are there so many moonquakes? Analyses of seismometers left on the moon during the Apollo moon landings reveal a surprising number of moonquakes occurring within 100 kilometers of the surface. In fact, 62 moonquakes were detected in data recorded between 1972 and 1977. Many of these moonquakes are not only strong enough to move furniture in a lunar apartment, but the stiff rock of the moon continues to vibrate for many minutes, significantly longer than the softer rock earthquakes on Earth. The cause of the moonquakes remains unknown, but a leading hypothesis include tidal gravity from -- and relative heating by -- our Earth. Regardless of the source, future moon dwellings need to be built to withstand the frequent shakings. Pictured here, Apollo 11 astronaut Buzz Aldrin stands beside a recently deployed lunar seismometer, looking back toward the lunar landing module. Explore Your Universe: Random APOD Generator

View towards Signal Hill at night, Cape Town, Western Cape, South Africa.

Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons. View source.

"The public and experts are far apart in their enthusiasm and predictions for AI. But they share similar views in wanting more personal control and worrying regulation will fall short". More at Pew Research Center ➜

NASA Astronomy Picture of the Day:

In dramatic silhouette against a cloudy daytime sky over Paris, France, gargoyles cast their monstrous gaze outward from the west facade of Notre Dame Cathedral. Taken on March 29, this telephoto snapshot also captures the dramatic silhouette of a New Moon against the bright solar disk in a partial solar eclipse. Happening high in Parisian skies, the partial eclipse was close to its maximum phase of about 23 percent. Occurring near the end of the first eclipse season of 2025, this partial solar eclipse followed the total eclipse of the Full Moon on March 13/14. The upcoming second eclipse season of 2025 will see a total lunar eclipse on September 7/8 and partial solar eclipse on September 21. The partial solar eclipse will be seen only from locations in planet Earth's southern hemisphere.

Photo by Bertrand Kulik

Male Chocó grasshopper (Opaon varicolor). A wingless short-horned grasshopper endemic to the Andes in Colombia.

Charles J. Sharp, CC BY-SA 4.0, via Wikimedia Commons. View source.

NASA Astronomy Picture of the Day:

Scanning the skies for galaxies, Canadian astronomer Paul Hickson and colleagues identified some 100 compact groups of galaxies, now appropriately called Hickson Compact Groups. The four prominent galaxies seen in this intriguing telescopic skyscape are one such group, Hickson 44. The galaxy group is about 100 million light-years distant, far beyond the spiky foreground Milky Way stars, toward the constellation Leo. The two spiral galaxies in the center of the image are edge-on NGC 3190 with its distinctive, warped dust lanes, and S-shaped NGC 3187. Along with the bright elliptical, NGC 3193 (above and left) they are also known as Arp 316. The spiral toward the lower right corner is NGC 3185, the 4th member of the Hickson group. Like other galaxies in Hickson groups, these show signs of distortion and enhanced star formation, evidence of a gravitational tug of war that will eventually result in galaxy mergers on a cosmic timescale. The merger process is now understood to be a normal part of the evolution of galaxies, including our own Milky Way. For scale, NGC 3190 is about 75,000 light-years across at the estimated distance of Hickson 44.

Photo by Jiang Wu

Dome of the Rock on the Temple Mount Jerusalem.

Ralf Roletschek, GFDL 1.2, via Wikimedia Commons. View source.