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Ephemeris: 10/10/2024 – Where did Comet Tsuchinshan-ATLAS come from?
This is Ephemeris for Thursday, October 10th. Today the Sun will be up for 11 hours and 13 minutes, setting at 7:05, and it will rise tomorrow at 7:53. The Moon, at first quarter today, will set at 12:05 tomorrow morning.
The comet Tsuchinshan-ATLAS will get far enough from the direction of the Sun so we can see it in the evening this weekend. It comes from the Oort Cloud of comets in the far reaches of the solar system probably extends maybe three quarters* of the way to the nearest other star to us Alpha Centauri. Somebody figured out that it has an orbital period of around 80,000 years. Every few million years or so a star comes close enough to the Sun to stir up the comets in the Oort Cloud, sending some of them out escaping the Sun and some sent in towards the inner solar system. This of course is one of the latter. No two comets are exactly alike so they’re quite unpredictable. Some have a lot of dust and some are mostly frozen gases.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
* On the radio program I stated a “quarter of the way”.
Addendum
The Oort Cloud is named after Jan Oort, a Dutch astronomer, who proposed a cloud of comets in 1950 as the source of long period comets. The cloud would extend from 2,000 to 200,000 times Earth’s distance from the Sun. The shape of the cloud is roughly spherical. Comet encounters with Jupiter can cause them to become short period comets, or be ejected from the solar system.
Ephemeris: 09/10/2024 – What last Saturday’s opposition from the Sun means
This is Ephemeris for Tuesday, September 10th. Today the Sun will be up for 12 hours and 45 minutes, setting at 8:01, and it will rise tomorrow at 7:17. The Moon, 1 day before first quarter, will set at 11:17 this evening.
Last Saturday the planet Saturn moved in opposition to the Sun. It’s not an insurrection or anything, but Saturn was opposite the Sun in the sky. At that time Saturn would be closest to the Earth of some 806 million miles (900 km). Saturn is 9 1/2 times the distance of the Earth to the Sun so over the year as Saturn moves from opposition through conjunction with the Sun to opposition again it does not vary in size very much, unlike Venus and Mars which are closer to us and vary a lot in size over their period around our sky. Saturn is now an evening planet and so will become a fixture in our evening skies for the next 4 or so months. It lies in a star poor part of the sky so it’s easy to find. Saturn’s rings are now nearly edge on to us so in a small telescope Saturn looks like a tiny disk stapled onto the sky with the staple being a bright line through the planet.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
* Mars has a fairly elliptical orbit and next January’s opposition is almost at its farthest. In 2003 Mars was as close as that it has gotten in 50,000 years, or so they tell me. At that time Mars’ apparent size was 72% larger than it will be next January. Mars has its closest oppositions to the Earth every 15 or 17 years. The last time it occurred was in 2018, and the next time will be in 2035.
Ephemeris: 08/19/24 – Dark Energy
This is Ephemeris for Monday, August 19th. Today the Sun will be up for 13 hours and 50 minutes, setting at 8:41, and it will rise tomorrow at 6:51. The Moon, at full today, will rise at 9:02 this evening.
The Big Bang, nearly 14 billion years ago set the universe to be expanding. All the mass of ordinary matter and the dark matter I talked about last week should be slowing that expansion. However, it was discovered, about 20 years ago, that the universal expansion is not slowing down. It is increasing its expansion rate. Astronomers do not really know why. Since expansion requires energy. This new property is called dark energy. It is actually the expansion of space itself. The galaxies are not fleeing by their own motion through space. They are carried by the expanding space around them. It turns out that objects with mass cannot exceed the speed of light, but the expansion of space itself has no speed limit. At least that’s how I understand it.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). Times will be different for other locations.
Addendum
Timeline of the universe. A representation of the evolution of the universe over 13.77 billion years. The far left depicts the earliest moment we can now probe, when a period of “inflation” produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted about 375,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe. Public Domain.
Ephemeris: 08/16/2024 – WIMPs and MACHOs
This is Ephemeris for Friday, August 16th. Today the Sun will be up for 13 hours and 58 minutes, setting at 8:46, and it will rise tomorrow at 6:48. The Moon, 3 days before full, will set at 3:34 tomorrow morning.
The dark matter that holds the clusters of galaxies together in the universe may be made of weakly interacting massive particles which astronomers have dubbed WIMPs. These particles would be more massive than the particles that ordinary matter is made of, but do not interact with ordinary matter or give off or absorb light. They are detected by the influence of their gravitational force alone. An alternative idea is Massive Compact Halo Objects or MACHOs. These may be made-up of ordinary matter. Since there are many more low mass stars, like red dwarfs, than there are high mass stars, perhaps there’s the creation of planet sized bodies like brown dwarfs. These are planets more massive than Jupiter, but not massive enough to become stars. As such, they should be practicably invisible.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). Times will be different for other locations.
Addendum
For more information on Dark Matter search for it on the internet. One Article I found is here: https://sciencenotes.org/what-is-dark-matter/. They dismiss MACHOs by not mentioning them at all, concentrating on the much more likely WIMPs.
Ephemeris: 08/15/2024 – What’s the matter with dark matter?
This is Bob Moler with Ephemeris for Thursday, August 15th. Today the Sun will be up for 14 hours and 1 minute, setting at 8:47, and it will rise tomorrow at 6:47. The Moon, 3 days past first quarter, will set at 2:23 tomorrow morning.
Over the past century astronomers have come to the realization that we are seeing only about 5% of the mass and energy of the universe. Galaxies in clusters seemed to move too fast to not escape, dissipating the cluster, yet after billions of years they still exist. Also, the stars in galaxies revolve about their centers much faster than expected revealing missing mass. So astronomers have come up with the idea that either there is missing matter that we can’t see, what’s called dark matter or there is something wrong with Newton’s and Einstein’s theories of gravity. Astronomers have come up with up two possible types of dark matter, which they humorously dub WIMPs and MACHOs. More about them tomorrow.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). Times will be different for other locations.
Addendum
Ephemeris: 07/22/2024 – Happy Pi Approximation Day
This is Bob Moler with Ephemeris for Pi Approximation Day*, Monday, July 22nd. Today the Sun will be up for 15 hours exactly, setting at 9:19, and it will rise tomorrow at 6:19. The Moon, 1 day past full, will rise at 10:37 this evening.
The first Pi day of the year for mathematics junkies was March 14th utilizing the three most significant digits of the mathematical value π, the ratio of the circumference of a circle to its diameter, written as 3.14. Today is the second version of π written as the fraction 22/7. We don’t write our date that way, we write it as 7/22. In other parts of the world it is written as 22/7. So whichever way you slice it, it’s a pi day and in Northern Michigan I would imagine it’s a cherry pi. In the sky today the planet Mercury is at its greatest elongation or separation east of the Sun in the western sky. It is preceding the Sun heading southward against the stars and is not easily visible after sunset.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.
* In the radio program I called it Pi Day #2. I have since found out that today has a special name.
Addendum
Ephemeris: 07/11/2024 – Low energy routes to get to the Moon
This is Ephemeris for Thursday, July 11th. Today the Sun will be up for 15 hours and 19 minutes, setting at 9:27, and it will rise tomorrow at 6:09. The Moon, 2 days before first quarter, will set at 12:26 tomorrow morning.
Back in the Apollo days when we sent people to the Moon, the trip out was only three days. The latest generation of unmanned probes to the Moon sent by the United States and other countries can take days, weeks, or even months to reach the Moon, so what’s going on? These are robot probes, needing little power. Humans however are high maintenance. Even when they’re doing nothing they are breathing, eating, and using resources. So when humans are aboard you have got to get there fast. Also, many of these probes are CubeSats, no bigger than a breadbox*. They must get into orbit of the Moon with very little thrust other than that of the rocket that launched them. They can go out as far as a million miles away before falling back to the Moon.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.
* OK, I’m an old guy, the modern size comparison would be a microwave.
Addendum
Ephemeris: 06/25/2024 – Three kinds of novas
This is Ephemeris for Tuesday, June 25th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, 3 days before last quarter, will rise at 12:35 tomorrow morning.
As I mentioned yesterday we’re expecting a nova or bright star that we expect to appear sometime this year, maybe in September according to some astronomers. A nova is a rapid brightening of a star due to some cataclysmic event happening to it. There are three kinds that we actually know of. A nova, which is what we’re expecting; a supernova, an explosion maybe a million times greater; and the recently discovered kilonova when two neutron stars collide, which is a thousand or so times brighter than an ordinary nova. A nova and one kind of supernova (Type 1) involve a binary star system which contains a white dwarf star near the end of its life close enough to a larger star to siphon off material. At some point enough has built up and an explosion occurs.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.
Addendum
The second type of Supernova is caused when a supermassive star’s core collapses when it’s made of iron and tries to fuse it into heaver elements. That process takes energy rather than producing it. Oops! The star collapses on itself, and… Kablooey!
Nova in a binary system
A red giant star and white dwarf orbit each other in this animation of a nova similar to T Coronae Borealis. The red giant is a large sphere in shades of red, orange, and white, with the side facing the white dwarf the lightest shades. The white dwarf is hidden in a bright glow of white and yellows, which represent an accretion disk around the star. A stream of material, shown as a diffuse cloud of red, flows from the red giant to the white dwarf. When the red giant moves behind the white dwarf, a nova explosion on the white dwarf ignites, creating a ball of ejected nova material shown in pale orange. After the fog of material clears, a small white spot remains, indicating that the white dwarf has survived the explosion. NASA/Goddard Space Flight Center.
Ephemeris: 05/24/2024 – The twilight zone
This is Ephemeris for Friday, May 24th. Today the Sun will be up for 15 hours and 9 minutes, setting at 9:14, and it will rise tomorrow at 6:04. The Moon, 1 day past full, will rise at 11:06 this evening.
Let’s take a look at twilight, despite the fact it doesn’t end until 1132 PM. Of course the bright Moon will rise before then. By the 12th of June astronomical twilight will end at midnight and a couple of days before the summer solstice it will have extended itself to 12:05 AM. The Moon tonight will rise in the middle of astronomical twilight so we’ll get about 1/2 hour or so of semi dark sky viewing from about 10:37 PM to moonrise at 11:07. There are three intervals of twilight. Civil twilight which is the period between sunset and when the Sun is 6° below the horizon. Nautical twilight extends to when the Sun is 12° below the horizon, and astronomical twilight which ends when the Sun is 18° below the horizon.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location
Addendum
Ephemeris: 05/23/2024 – My observations of the Earth as a globe
This is Bob Moler with Ephemeris for Thursday, May 23rd. Today the Sun will be up for 15 hours and 7 minutes, setting at 9:13, and it will rise tomorrow at 6:05. The Moon, at full today, will rise at 9:58 this evening.
As far as I can remember back in time I’ve always thought that the Earth was a globe. To me that the Earth is flat is nonsensical. And I’ve looked to the sky as confirmation that the Earth was indeed a globe. During my first trip to a southern state I saw it for myself. From our vantage point here in Michigan the constellation of Scorpius the scorpion just scrapes the southern horizon at its highest. When traveling down to Kentucky it was higher in the sky, so that was my first proof that the Earth is round. I’ve since gone to Hawaii and even using the programs I wrote and use for the times for Ephemeris, based on the Earth as a globe, I was able to predict when and where to see the Southern Cross. It was right there as calculated by my program.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.
Addendum
Bob Moler's Ephemeris Blog 
