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NASA Astronomy Picture of the Day
September 2, 2025
The Horsehead and Flame Nebulas
The Horsehead Nebula is one of the most famous nebulae on the sky. It is visible as the dark indentation to the orange emission nebula at the far right of the featured picture. The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright emission nebula. Like clouds in Earth's atmosphere, this cosmic cloud has assumed a recognizable shape by chance. After many thousands of years, the internal motions of the cloud will surely alter its appearance. The emission nebula's orange color is caused by electrons recombining with protons to form hydrogen atoms. Toward the lower left of the image is the Flame Nebula, an orange-tinged nebula that also contains intricate filaments of dark dust.
https://apod.nasa.gov/apod/astropix.html
The full 'Corn Moon' rises this week — bringing a 'blood moon' lunar eclipse to most of the world
August 31, 2025
The final full moon of the Northern Hemisphere's summer will occur on Sunday, Sept. 7, and the best time to see it will be later that day as it rises in the east at dusk.
Although it's often called the Harvest Moon, September's full moon is named the Corn Moon this year. That's because the closest full moon to the equinox on Sept. 22 is traditionally called the Harvest Moon, and this year, that's October's full moon (rising Oct 6).
This switch-up happens every three years, according to Time and Date.
Other names for September's full moon include the Wine Moon, the Song Moon and the Barley Moon, while Anishinaabeg people call the September moon "Wabaabagaa Giizis," which means the "Changing Leaves Moon," according to the Center for Native American Studies.
Although the moon will be officially full at 2:10 p.m. EDT (18:10 UTC) on Sept. 7, a full moon is best observed as it rises in the east shortly after the sun has set in the west.
This month, that happens a few hours after the moon has become full, with the Corn Moon rising a few minutes after sunset across North America.
This year's Corn Moon is also a total lunar eclipse for viewers in some areas of the world. From Australia, Asia, Africa and parts of Europe, a "blood moon" will be visible for 82 minutes — the longest total lunar eclipse since Nov. 8, 2022.
It will be almost identical to the total lunar eclipse seen in North America for 65 minutes on March 14, 2025. However, the Sept. 7 eclipse will occur before moonrise in North America.
You can look at the full moon without any optical aids, but if you catch it at moonrise, stargazing binoculars and backyard telescopes can help reveal details on the lunar surface that are not visible to the naked eye.
As the full moon rises, its glare increases significantly, making it difficult to view the moon directly.
The following evening, on Monday, Sept. 8, the waning gibbous moon will have Saturn close by. The ringed planet will be particularly bright because it reaches its annual opposition — when it's closest to Earth — on Sept. 20.
After September's Corn Moon, the next full moon will be the Harvest Moon, which will turn full on Monday, Oct. 6.
https://www.livescience.com/space/the-moon/the-full-corn-moon-rises-this-week-bringing-a-blood-moon-lunar-eclipse-to-most-of-the-world
https://www.timeanddate.com/astronomy/moon/full-corn.html
https://www.farmersalmanac.com/full-moon-dates-and-times
The Blind Date of Mars with 3I/ATLAS in a Month
September 1, 2025
Blind dates are exciting because they hold the potential for surprises, especially when dealing with an interstellar date partner of unknown origin.
On October 3, 2025, the interstellar object 3I/ATLAS will pass within a distance of 29 million kilometers from Mars.
At that time, the HiRISE camera onboard the Mars Reconnaissance Orbiter will be able to image 3I/ATLAS with a resolution of 30 kilometers per pixel.
The resulting closeup image might separate the contributions of the nucleus and surrounding dust cloud to the total luminosity of reflected sunlight stemming from 3I/ATLAS.
The Minimum Orbit Intersection Distance (MOID) of 3I/ATLAS from Mars, namely the closest distance that 3I/ATLAS gets to the complete path of Mars around the Sun, is merely 2.7 million kilometers.
This by itself constitutes a remarkable fine-tuning of the path of 3I/ATLAS.
If 3I/ATLAS is a technological object, this short MOID makes it easy for a precursor mini-probe to reach Mars.
In addition, an orbit correction by 10–15 kilometers per second during the month of September 2025, could shrink the closest approach distance of 3I/ATLAS from Mars to zero, as calculated in Figure 4 of my paper with Adam Hibberd and Adam Crowl (accessible here).
The ejection of icy fragments from the surface of a natural comet can only result in a velocity kick of order 0.4 kilometers per second based on the analysis of data from the Webb telescope (accessible here).
This ejection speed is insufficient for these fragments to reach Mars. Moreover, the extent of the CO2 plume observed by SPHEREx around 3I/ATLAS (as reported here) is of order 350,000 kilometers, a distance beyond which the plume is expected to be confined by the ram-pressure from the solar wind.
This distance is still shorter by a factor of a hundred from the value needed to reach Mars during the closest approach of 3I/ATLAS without a maneuver.
Given all these considerations, the arrival of materials from 3I/ATLAS to Mars in October 2025 will be a potential signature of technology.
Gladly, the Labor Day holiday provided me with a relief from my routine administrative duties as director of Harvard’s Institute for Theory & Computation.
In between interviews for television and podcasts, I calculated that if 3I/ATLAS has a precursor probe that was traveling ahead of it and sideways towards Mars by about 30 million kilometers, then this precursor probe would be able to intercept Mars on October 3, 2025 or during the week preceding it.
This provides a second motivation for using HiRISE within a month.
In addition to imaging the nucleus and dust cloud of 3I/ATLAS, HiRISE could image Mars in search for any precursor objects that precede 3I/ATLAS and get closer to Mars than the main object.
Near-Earth telescopes cannot detect the reflection of sunlight from precursor objects that are smaller than a hundred meters, the upper limit on the size of all space probes launched by humans so far.
Blind dates can be exciting if we observe the other side with curiosity and regard data collection as an opportunity to learn something new.
https://avi-loeb.medium.com/the-blind-date-of-mars-with-3i-atlas-in-a-month-476c7288a576