Public Posts

NASA Astronomy Picture of the Day:

It was the strongest gravitational wave signal yet measured -- what did it show? GW250114 was detected by both arms of the Laser Interferometer Gravitational-wave Observatory (LIGO) in Washington and Louisiana USA earlier this year. Analysis showed that the event was created when two black holes, each of mass around 33 times the mass of the Sun, coalesced into one larger black hole with a mass of around 63 solar masses. Even though the event happened about a billion light years away, the signal was so strong that the spin of all black holes, as well as initial ringing of the final black hole, was deduced with exceptional accuracy. Furthermore, it was confirmed better than before, as previously predicted, that the total event horizon area of the combined black hole was greater than those of the merging black holes. Featured, an artist's illustration depicts an imaginative and conceptual view from near one of the black holes before collision.

Feskekôrka (meaning "fish church") is a historic building in Gothenburg, Sweden that formerly housed an indoor fish market. Its name is based on the building's resemblance to a neo-Gothic church.

Arild Vågen, CC BY-SA 4.0, via Wikimedia Commons. View source.

NASA Astronomy Picture of the Day:

How massive can a normal star be? Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, making it one of the most massive stars known. This star is the brightest object located in the central cavity near the bottom center of the featured image taken with the Webb Space Telescope in infrared light. For comparison, a rollover image from the Hubble Space Telescope is also featured in visible light. Close inspection of the images, however, has shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least. Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record. Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357. Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be breaking out and illuminating a spectacular cocoon. Teachers & Students: Ideas for Utilizing APOD in the Classroom

The participants of the Prussian Egypt expedition on the top of the Great Pyramid, watercolour by Johann Jakob Frey, 1842.

Johann Jakob Frey, Public domain, via Wikimedia Commons. View source.

Jorge Luis Borges (1899 – 1986) Argentine short-story writer, essayist and poet. He was a key figure in Spanish language and universal literature.

NASA Astronomy Picture of the Day:

On Saturn, the rings tell you the season. On Earth, today marks an equinox, the time when the Earth's equator tilts directly toward the Sun. Since Saturn's grand rings orbit along the planet's equator, these rings appear most prominent -- from the direction of the Sun -- when the spin axis of Saturn points toward the Sun. Conversely, when Saturn's spin axis points to the side, an equinox occurs, and the edge-on rings are hard to see from not only the Sun -- but Earth. In the featured montage, images of Saturn between the years of 2020 and 2025 have been superposed to show the giant planet passing, with this year's equinox, from summer in the north to summer in the south. Yesterday, Saturn was coincidently about as close as it gets to planet Earth, and so this month the ringed giant's orb is relatively bright and visible throughout the night.

Photo by Imran Sultan

The Isaiah Scroll is the best preserved of the seven Dead Sea Scrolls that were first discovered by Bedouin shepherds from Qumran. The Dead Sea Scrolls were first made available to the public on this date in 1991.

Unknown artistUnknown artist, Public domain, via Wikimedia Commons. View source.

There are only two moments each year when the Sun lies directly above Earth’s equator. These moments are the equinoxes, when, at any location, the lengths of day and night are roughly equal. The March equinox happens sometime between March 19 and 21. The September equinox occurs sometime between September 21 and 24.
In the Northern Hemisphere, the March equinox marks the beginning of Spring and the September equinox the beginning of Fall. The reverse takes place in the Southern Hemisphere.

NASA Astronomy Picture of the Day:

Does the Sun set in the same direction every day? No, the direction of sunset depends on the time of the year. Although the Sun always sets approximately toward the west, on an equinox like tomorrow the Sun sets directly toward the west. After tomorrow's September equinox, the Sun will set increasingly toward the southwest, reaching its maximum displacement at the December solstice. Before tomorrow's September equinox, the Sun had set toward the northwest, reaching its maximum displacement at the June solstice. The featured time-lapse image shows seven bands of the Sun setting one day each month from 2019 December through 2020 June. These image sequences were taken from Alberta, Canada -- well north of the Earth's equator -- and feature the city of Edmonton in the foreground. The middle band shows the Sun setting during an equinox -- in March. From this location, the Sun will set along this same equinox band again tomorrow.