Category Archives: Planets

Astronomy, Black Hole, Cosmology, Dark Matter, NASA, Planets

Ten amazing space discoveries in 2024.

The Early Universe is Running out of Supermassive Black holes.

As the Webb Space Telescope continues to find supermassive blackholes (SMBH) in the time after the Dark Ages, there has been a significant down turn in their masses. Now the most common SMBHs earlier than one billion years ABB are about 4 million solar masses – about the same mass as Sgr A* in our Milky Way.  At 700 million years ABB, Webb found a SMBH with 40 million solar masses. GN-z11 at 420 million years ABB has an estimated mass of 2 million suns. LID-568 (See NASA artwork above) has a mass of 10 million suns at an age 1.5 billion years ABB. ZS7 consists of two merging SMBHs each with a mass of about 50 million suns at an age of about 740 million years ABB. So, Webb is now giving us a glimpse of black hole mergers and rapid growth long before we reach the billion-sun masses of todays SMBHs.

Cosmic Gravity Wave Background

Teams of scientists worldwide have reported the discovery of the “low pitch hum” of these cosmic ripples flowing through the Milky Way. The detected signal is compelling evidence and consistent with theoretical expectations of gravity wave pulses from millions of distant binary hole mergers, where these black holes are of the SMBH variety. The artwork above is provided by NASA. [UC Berkeley News]

DESI survey of 6 million galaxies validates Big Bang

Researchers used the Dark Energy Spectroscopic Instrument (DESI) to map how nearly 6 million galaxies cluster across 11 billion years of cosmic history as shown in the image above (Credit: D. Schlegel/Berkeley Lab using data from DESI). Their observations line up with what Einstein’s theory of general relativity predicts. Looking at galaxies and how they cluster across time reveals the growth of cosmic structure, which lets DESI test theories of modified gravity – an alternative explanation for our universe’s accelerating expansion. DESI researchers found that the way galaxies cluster is consistent with our standard model of gravity and the predictions from Einstein’s theory of general relativity. There is even a suggestion in the data that Dark Energy is weakening as the universe ages over the last 11 billion years. This has huge implications for modeling the future of the universe. [News from Berkeley Lab]

Supersymmetry searches still come up empty-handed

Before the beginning of the Large Hadron Collider data taking, supersymmetry (SUSY)  was seen as a single answer to many unresolved open questions of the Standard Model. The LHC ATLAS research program has first quickly excluded most of the simplest SUSY configurations, then moved to a detailed work targeting many signatures, not necessarily favored by a theoretical prejudice. The lack of an identified SUSY signal so far at the massive ATLAS detector shown above (Credit: ATLAS Experiment © 2022 CERN) is certainly a disappointing and possibly somewhat surprising outcome to many scientists. A lot of theoretical effort into String theory and the search for a quantum theory of gravity hinges on going beyond the so-called Standard Model, and supersymmetry is a key mathematical ingredient to many of these simpler extensions. [LHC-ATLAS Consortium]

Dark Matter searches still find no candidate particles

After 40 years of searching for dark matter candidate particles, the currently most popular assumption for the nature of DM still is that of a (new) particle, even though the jury is not entirely out on whether the present observations of DM are due to a particle (or wave-like behavior at very low masses) or due to our limited understanding of the gravitational force at large scales. The figure above shows the current list of candidate particles being considered (Credit: CERN/G. Bertone and T. M. P. Tait) Despite its success, the Standard Model of particle physics (SM) in its present form (6 quarks, 6 leptons, 1 Higgs boson, plus the 12 quanta for the three non-gravity forces) is not able to offer an explanation for dark matter. It offers no known particle that can play that role. The LHC experiments, meanwhile, have by now completed and published all their main DM search analyses for the Run-2 data taken before 2016. No evidence as yet has been found for signals of the production of dark matter or dark sector particles. Dark matter, as a particle representing some 25% of all gravitating ‘stuff’ in the universe, remains one of the biggest puzzles in physics today.

Origin of the solar wind discovered

After several decades of theoretical speculation, solar physicists are now certain that they have discovered how our sun produces the interplanetary wind of matter that streams out of its corona at speeds of over 200 km/s. In 2024, the ESA-led Solar Orbiter spacecraft made the first ever connection between measurements of the solar wind around a spacecraft to high-resolution images of the Sun’s surface at a close distance. The spacecraft passed through the magnetic field connected to the edge of a coronal hole complex. This let the team watch the way the solar wind changed its speed – from fast to slow or vice versa – and other properties, confirming that they were looking at the correct region. In the end, they got a perfect combination of both types of features together. The image above (Credit:ESA & NASA/Solar Orbiter/EUI Team; acknowledgement: Lakshmi Pradeep Chitta, Max Planck Institute for Solar System Research) taken by the ESA/NASA Solar Orbiter spacecraft shows a ‘coronal hole’ near the Sun’s south pole. Subsequent analysis revealed many tiny jets of plasma being released into the corona and solar wind during the observation. 

The origin of the springtime, dinosaur-killer asteroid

According to a recent article published in Nature magazine, the object that smashed into Earth and kick-started the extinction that wiped out almost all dinosaurs 66 million years ago was an asteroid that originally formed beyond the orbit of Jupiter, according to geochemical evidence from the impact site in Chicxulub, Mexico. Comparisons between the chemical record left behind by the strike 66 million years ago and known meteorite samples suggest that the Cretaceous asteroid was a carbonaceous chondrite. This type of asteroid is one of the oldest known, having formed billions of years ago in the early solar system. As these chondrites can only come from asteroids found beyond Jupiter, it suggests that the asteroid must have had its origins there too. Some of the chondritic spherules got into the gills of dying fish, fossils of which have been used to reveal that  the asteroid impacted during the springtime in the northern hemisphere. This is possible to know based on where the lines of growth in the fish’s bones stop, which can be read somewhat like rings in a tree trunk.

Current round-up of fireball detections worldwide

The most recent world map of detected fireballs from 1988 to 2024 detected with a variety of sensors (optical, infrasound, etc) reveals that fireballs delivering less than 30 kilotons-equivalent TNT upon atmospheric detonation are uniformly spread around Earth’s surface. In 2019 it was determined that the Geostationary Lightning Mapper (GLM) instruments on GOES weather satellites can detect fireballs and bolides. This largely removes much of the observer-bias from the detections irrespective of geographic latitude. The bright red dot is the 2013 Chelyabinsk Meteor fireball and impact. (Credit: NASA/CNEOS/JPL)

NASA spacecraft detects subterranean Martian water

Using seismic activity to probe the interior of Mars, geophysicists have found evidence for a large underground reservoir of liquid water — enough to fill oceans on the planet’s surface. The data from NASA’s Insight lander (2018-2022) allowed the scientists to estimate that the amount of groundwater could cover the entire planet to a depth of between 1 and 2 kilometers, or about a mile. While that’s good news for those tracking the fate of water on the planet after its oceans disappeared more than 3 billion years ago, the reservoir won’t be of much use to anyone trying to tap into it to supply a future Mars colony. It’s located in tiny cracks and pores in rock in the middle of the Martian crust, between 11.5 and 20 kilometers (7 to 13 miles) below the surface. Even on Earth, drilling that deep would be a challenge. [UC Berkeley News].

Organized magnetic fields in Sgr A* black hole accretion disk

A new image from the Event Horizon Telescope (EHT) collaboration has uncovered strong and organized magnetic fields spiraling from the edge of the supermassive black hole Sagittarius A* (Sgr A*). Seen in polarized light for the first time, this new view of the monster lurking at the heart of the Milky Way Galaxy has revealed a magnetic field structure strikingly similar to that of the black hole at the center of the M87 galaxy, suggesting that strong magnetic fields may be common to all black holes. This similarity also hints toward a hidden jet in Sgr A*.Scientists unveiled the first image of Sgr A*— which is approximately 27,000 light-years away from Earth— in 2022, revealing that while the Milky Way’s supermassive black hole is more than a thousand times smaller and less massive than M87’s, it looks remarkably similar. This made scientists wonder whether the two shared common traits outside of their looks. To find out, the team decided to study Sgr A* in polarized light. Previous studies of light around M87* revealed that the magnetic fields around the black hole giant allowed it to launch powerful jets of material back into the surrounding environment. Building on this work, the new images have revealed that the same may be true for Sgr A*. [Credit EHT Collaboration]

Astronomy, Gravity, Moon, Planets

Why are there no ocean tides at the equator?

A typical scene on North Seymour in the Galapagos Islands. (Credit:Wikipedia-David Adam Kess). In general, tides along continental shores near the equator are much less violent than elsewhere.

Tides are a very complex phenomenon. For any particular location, their height and fluctuation in time depends to varying degrees on the location of the Sun and the Moon, and to the details of the shape of the beach, coastline, coastline depth and prevailing ocean currents. Here is a figure that shows the difference between high tide and low tide around the world.

Newton’s explanation is that, when you calculate the difference in gravity between Earth and moon at each point on the surface of Earth, you get the customary graph shown here:

This is also the shape of the ‘equipotential surface’ where mass would be in equilibrium and instantaneously ‘at rest’. There are two gravitational tides: The Body Tide and the Water Tide. The Body Tide is the response of the solid Earth to this gravitational distortion in the solid rock of Earth. The lunar body tide has a height of 0.3 meters relative to the unstressed shape of Earth while the solar body tide is about half this high. The water tides are far higher because water is lower density than rock and is free to flow around Earth’s surface with lower inertia than rock. Water tide heights can exceed 10 meters!

You would think that the solid body tide would flex the ground so severely that pipes, railroad tracks and other systems would flex and break over time. The good news is that the scale of this distortion is continent-spanning as the figure below shows.

So what does this all have to do with whether tides are found at the Equator?

Although Newton gave us the basic gravitational theory for solid body tides, his application of this theory to the behavior of water was not correct in detail. The French mathematician Laplace used Newton’s gravitational theory, but realized that its application to water tides had much more to do with the gravitational forcing of various water oscillations. Water oscillations, treated as a harmonic system with many different resonant frequencies is a much more powerful description of the details of water tides on Earth. When you combine the main lunar water tide and the solar tides acting on a complex shaped layer of water along Earth’s surface, what you get is a very different pattern of high and low water tides shown in this figure.

This figure created by Dr. Richard Ray/Space Geodesy branch, NASA/GSFC, shows the M2 lunar tidal constituent. Amplitude is indicated by color, and the white lines are cotidal differing by 1 hr. The curved arcs around the amphidromic points show the direction of the tides, each indicating a synchronized 6 hour period. Note that this response of ocean water has virtually nothing to do with the simple two-bulges, gravitational stress pattern expected from Newton’s calculation above.

So are there water tides at the Equator? Yes there are, and in fact the only locations that have very weak tides are near the poles!

Astronomy, Planets, Sun

Has the loss of mass by the Sun over the last 4 billion years been enough to affect planetary orbits?

Fron the ISS ,our sun is a dazzling star (Credit: NASA/ISS). The luminosity of the Sun is 200 trillion trillion watts or 2 x 10^33 ergs per second. From Einstein’s famous equation, E = mc^2, and using c = 3 x 10^10 centimeters/sec, the Sun’s luminosity is equal to a loss of mass from the fusion cycle of about 2 x 10^12 grams/second. Over one year this is 7 x 10^19 grams, and over the entire life of the Sun to date is about 3.1 x 10^29 grams. The mass of the Sun is 4 x 10^33 grams so this loss equals 0.008 percent of its current mass. The mass of Jupiter is about 0.1 percent of the Sun’s current mass, so over the Sun’s entire lifetime to date, it has lost barely 0.08 percent of Jupiter’s mass, or about the mass of the Earth.

We can estimate how much this mass loss would have changed the orbit of the Earth by approximating the orbital dynamics as the balance between kinetic and gravitational potential energy or 1/2 mV^2 = GMm/R where m = mass of Earth, and M = mass of Sun. We see that a reduction in the Sun’s mass by a factor of of 0.00008 causes an increase in the Earth-Sun distance if the kinetic energy of the Earth is held constant. This means that over the last 4.5 billion years, we can estimate that the Earth’s orbit has increased by about 0.00008 x 93 million miles or about 7,000 miles; about the Earth’s own diameter!

The Sun also produces a ‘solar wind’ of particles at a rate of about 10^-14 solar masses per year. The NASA illustration shows the general idea of what this wind does as it travels through interplanetary space. In 4 billion years this amounts to about 0.001 percent of the Sun’s mass, which to the level of our approximations is a factor of 8 times smaller that the mass loss from converting some of its mass into light. However, both the solar luminosity and solar wind have not been constant over 4 billion years, with the sun having been fainter long ago, and its wind having been much stronger when it was first born.

The overall effects of these mass loss rates can be significant when dynamicists try to predict the long-term orbits of planets. We know that small changes in any physical parameter in these ‘non-linear’ mathematical theories can produce substantial changes in the locations of planets in their orbits. It would not surprise me if the sun loosing 1 Earth mass over 4 billion years might also have a significant effect in predictions of where planets are in the distant future.

Astronomy, Planets

What is the distance from the Sun to the Earth for each month of the year?

We all know that Earth orbits our sun in an elliptical path, which means that for certain times of the year it is closer to the sun than for others. Here is a distorted view of the basic orbit (Credit: Wikipedia), but beware that the scales are all wrong. There is only a 5 million kilometer difference between the longest and shortest lengths of the ellipse!

According to the 1996 US Ephemeris, on the 21st of each month, the distance to the Sun is:

Month...............distance............

January             0.9840       147,200,000
February            0.9888       147,900,000
March               0.9962       149,000,000
April               1.0050       150,300,000
May                 1.0122       151,400,000
June                1.0163       152,000,000
July                1.0161       152,000,000
August              1.0116       151,300,000
September           1.0039       150,200,000
October             0.9954       148,900,000
November            0.9878       147,700,000
December            0.9837       147,200,000

.................................

where the first column gives the distance in Astronomical Units so that 1.0 AU = 149,597,900 kilometers By the way, I have rounded all of the distance numbers to 4 significant figures. If you want a mathematical formula that gives you the distances in AU using these table entries for month number N, it looks like this:

d(N) = 1.0000 + 0.0163 cos [ (2pi/12)*((N-1)/12) + 200*2pi/360]

As you can see from the table, the Earth is farthest from the Sun when the Northern Hemisphere is in the summer season (July 3), and closest in the winter (January 3). If you were living in the Southern Hemisphere, the seasons are reversed so that in the summer, the Sun is closest and in the winter it is farthest.

Astronomy, Planets

Why does Venus rotate backwards from the other planets?

The rotation period of Venus cannot be decided through telescopic observations of its surface markings because its featureless thick atmosphere makes this impossible. In the 1960’s, radar pulses were bounced off of Venus while at its closest distance to the Earth, and it was discovered that its rotation period, its day, was 243.09 +/- 0.18 earth days long, but it rotated on its axis in a backwards or retrograde sense from the other planets. The above image was created by NASA’s Magellan spacecraft whos radar imaging technique was able to detect surface feaatures as small as a few kilometers across.

If you were to look down at the plane of the solar system from its ‘north pole’ you would see the planets orbiting the Sun counterclockwise, and rotating on their axis counterclockwise. Except for Venus. Venus would be rotating clockwise as it orbited the Sun counterclockwise. Venus is not alone. The axis of Uranus is inclined so far towards the plane of the solar system that it almost rolls on its side as it orbits the Sun.

What accounts for the extreme inclinations of the rotation axis of Venus and Uranus? For years it was thought that in the case of Venus that Earth was the culprit. It is a curious fact that as Venus rotates three times on its axis in 729.27 days, Earth goes twice around the Sun ( 728.50 days) This has suggested to many astronomers that Earth and Venus are locked into a 3:2 tidal resonance. There are many bodies in the solar system that seem to be locked into various kinds of spin-orbit resonances, especially families of asteroids with the planet Jupiter. Mercury also seems to be gravitationally locked into some kind of resonance with the Sun since its day (58.646 days) and its year ( 87.969 days) are also in the proportion of 3:2.

Forces acting on spinning bodies result in some peculiar acrobatics. For instance, if you take a spinning top and give it a push, it will begin to wobble in a manner called precession. The axis of the Earth makes a 26,000 year wobble with an amplitude of tens of degrees. This is all due to the influence of the Moon’s tidal attraction of the Earth. In the case of Venus, however, the gentle gravitational forces it may receive over billions of years to place it in a 3:2 resonance with the Earth don’t seem to be strong enough to tip the entire planet over to make its rotation retrograde. The best, current, ideas still favor some dramatic event that occurred while Venus (and Uranus for that matter) were being formed. It is known from the cratering evidence we see on a variety of planetary surfaces, that soon after the planets were formed, there were still some might large mini-planets orbiting the Sun. One of these may have collided with the Earth, dredging up material that later solidified into our Moon. The satellites of the outer planets are probably representitives of this ancient population of bodies. Venus may have experienced an encounter with one of these large bodies in which, unlike for Earth, the material didn’t form a separate moon, but was absorbed into the body of Venus. In addition to mass and kinetic energy, this body would also have contributed angular momentum. The result is that the new spin direction and speed for Venus was seriously altered from its initial state, which could have been very Earth-like. Today, the result of that last, ancient collision is Venus with a retrograde rotation.

This theory may also apply to Uranus provided that the collision happened before the 15 satellites themselves were captured or formed. Their orbital planes look very uniform and show no evidence for a dramatic gravitational event such as a collision. It may be, too, that the Uranian collision event dredged up matter and flung it into orbit around Uranus, and out of this were formed the larger, coplanar, moons of Uranus.

This is, clearly, a complicated and not well understood phenomenon. The facts for Venus point towards a collision event to put its axis and rotation in the retrograde sense. The tidal action of the Earth on Venus, acting steadily over billions of years, then established the 3:2 spin-orbit resonance. Every 2 earth years, the exact same portion of the Venerian ( Cytherian) surface faces Earth. Could there be some sub- surface concentration of mass on this portion of Venus that the Earth can grab onto to create the tidal lock?

Astronomy, Planets, Space Travel

How long would a trip to Mars take?

Contrary to the ‘point and shoot’ idea, an actual trip to Mars looks very round-a-bout as the figure above shows for a typical ‘minimum cost’ trajectory. This, by the way, is called a Hohman Transfer Orbit, and is the mainstay of interplanetary space travel. All you need to do is give your payload a few km/sec of added speed at Earth to place you into the right elliptical orbit whose aphelion is at the location of mars, and then when you get there you fire your rockets in the opposite direction a second time to reduce your speed by a few km/sec to put you into a mars-capture orbit. You spend your entire flight coasting between the planets with no rockets firing. That’s what makes it a cheap flight in terms of fuel, but an expensive one in terms of flight time. In the end, it is always fuel cost that wins.

The travel time depends on the exact details of the orbit you take between the Earth and Mars. The typical time during Mars’s closest approach to the Earth every 1.6 years is about 260 days. Again, the details depend on the rocket velocity and the closeness of the planets, but 260 days is the number most often estimated, give or take 10 days. Some high-speed transfer orbits could make the trip in as little as 130 days.

That said, chemical rockets are very inefficient for interplanetary travel with specific impulses of about 250 seconds and maximum speeds of 10 km/sec. For some really quick trips ,engineers consider advanced ion propulsion systems with specific impulses of over 5000 seconds and maximum speeds of 100 km/sec and travel times of a month. Nuclear-thermal rockets can do even better with speeds up to 10,000 km/sec. At these speeds, a trip to Mars becomes less than a week!

Astronomy, Planets

What is the Typical Temperature on Mars?

The daytime surface temperature is about 80 F during rare summer days, to -200 F at the poles in winter. The air temperature, however, rarely gets much above 32 F.

The temperatures on the two Viking landers, measured at 1.5 meters above the sursurface, range from + 1° F, ( -17.2° C) to -178° F (-107° C). However, the temperature of the surface at the winter polar caps drop to -225° F, (-143° C) while the warmest soil occasionally reaches +81° F (27° C) as estimated from Viking Orbiter Infrared Thermal Mapper.

In 2004, the Spirit rover recorded the warmest temperature around +5 C and the coldest is -15 Celsius in the Guisev Crater.

The Curiosity Rover landed in August 2012 and has been steadily building up an enormous data base of meteorological conditions and measurements. Here from its equatorial location in Gale Crater are its temperature readings. Credit: NASA/JPL-Caltech/CAB(CSIC-INTA)/FMI/Ashima Research. This pair of graphs shows about one-fourth of a Martian year’s record of temperatures (in degrees Celsius) measured by the Rover Environmental Monitoring Station (REMS) on NASA’s Curiosity rover. The data are graphed by sol number (Martian day, starting with Curiosity’s landing day as Sol 0), for a period from mid-August 2012 to late February 2013, corresponding to late winter through the end of spring in Mars’ southern hemisphere.

Astronomy, Planets

Why don’t Mercury and Venus have moons?

This colorful view of Mercury was produced by using images from the color base map imaging campaign during MESSENGER’s primary mission. These colors are not what Mercury would look like to the human eye, but rather the colors enhance the chemical, mineralogical, and physical differences between the rocks that make up the planet’s surface. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington.

Most likely Mercury and Venus have no moons because they are too close to the Sun.

Any moon with too great a distance from these planets would be in an unstable orbit and it would be captured by the Sun. If they were too close to these planets they would be destroyed by tidal gravitational forces. The zones where moons around these planets could be stable over billions of years is probably so narrow that no body was ever captured into orbit, or created in situ, when the planets were first being accreted.

What are the specifics? Lets do the calculation of forces!

Mercury: How far from Mercury would a satellite be at which point the gravity force of the sun equals that of mercury?

G(Mp)m/rs^2 = G(Ms)m/R^2

were M is the masss of the sun, m is the mass of the satellite, rs is the distance of the satellite from the center of mercury and R is the distance from Mercury to the sun. The value for the satellite mass, m, cancils, as does the constant of gravity, G, so for R = 35 million km, Ms = 2×10^30 kg, Mp = 3.3×10^23 kg, we get with some algebra that rs = 14,000 km.

The tidal limit for the satellite, which is the point at which the tidal gravity force of Mercury shatters the satellite, is given by the formula R = 1.26 x Rm (Rho m/Rho M)^1/3 where Rho m is the satellites density and Rho M is the planets density. For a satellite made of mercury material the densities are the same so the tidal radius is 1.26 x Mercury’s radius of 2440 km, or 3070 kilometers.

So the roughly stable orbit range for such a satellite is between 3000 km and 14,000 km from the center of Mercury, or between 600 and 11,000 km from its surface. For Venus, the same calculation woud give a significantly wider orbit range from 7600 km to 162,000 km from the planet’s center, or 1600 to 156,000 km from its surface.

Clearly, Venus is a far more promissing place to stuff one or more moons, so it is a puzzle why it has none, unless the catastrophic impact that tilted Venus’s rotation axis also stripped off any primordial, orbiting moons.